Student Experiment Documentation · integration progress review, and nal experiment report. The R2C2 Team consists of a diverse and inter-disciplinary group of students from Lule

SEDStudent Experiment Documentation

Document ID: BX29 R2C2 SEDv1-0 16Jan19

Mission: BEXUS 29

Team Name: R2C2

Experiment Title: Radar Recognition of Chaff Clouds in the stratosphere

Team NameStudent Team Leader: Niels de Graaf

Team Members: Nehir SchmidDaniel Royo SerranoAydin Nakhaee-zadeh GutierrezMaximilian ZachKiran TikareGuillermo Zaragoza ProusDavid Villegas PradosAdam Peter HoehneMaximilian Buhrer

University: Lulea University of Technology

Version: Issue Date: Document Type: Valid from

1.0 January 16, 2019 Spec January 16, 2019

Issued by:

The R2C2 Team

Approved by:

xx

BX29 R2C2 SEDv1-0 16Jan19

- 2 -

CHANGE RECORD

Version Date Changed chapter Remarks0 2018-12-06 New Version1-0 All PDR


- 3 -

Abstract:The R2C2 (Radar Recognition of Chaff Clouds in the stratosphere) experimentconcerns the navigation of high altitude aerostatic balloons. To navigate suchballoons, it is critical to know which wind directions are available in the closevicinity of the balloon and with which intensity the wind is flowing. As of now,the only possible way to determine how the wind layers are moving around theballoon is through trial and error. This means changing the altitude of theballoon in the hopes of finding a wind current that will take it in the desireddirection. The objective of this experiment is to test a method of determiningthe direction of the wind layers below the balloon at high altitude. To dothis, chaff will be used. Chaff consists of small conductive metal pieces. Whenreleased mid-air it forms a“cloud”and slowly drifts away following the air currentsbefore eventually dispersing. This chaff cloud can be tracked with a radar. Touse this method for navigation, the tracking would ideally be done from theballoon. The R2C2 experiment would ideally use an on-board radar system aschaff tracking system. However, to keep the workload of the experiment at areasonable amount, the team plans to use a ground radar system instead. Thisexperiment also tests the design and implementation of a chaff release system.The gathered data of the chaff descent will be analyzed for information aboutthe stratospheric winds, the dynamics of chaff clouds and the effects of differentchaff foil shapes and sizes. We hope to extract information that will help choosesuitable chaff probes and radar systems for future experiments and applications.

Keywords: Balloon Experiments for University Students, High-Altitude Balloon Navigation,Chaff, Wind Layers,


- 4 -

Contents

CHANGE RECORD 2

PREFACE 7

1 Introduction 91.1 Scientific Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91.2 Mission Statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111.3 Experiment Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121.4 Experiment Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

1.4.1 Experiment time-line . . . . . . . . . . . . . . . . . . . . . . . . . . . 141.5 Team Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2 Experiment Requirements and Constraints 172.1 Functional Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172.2 Performance Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182.3 Design Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202.4 Operational Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212.5 Constraints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

3 Project Planning 233.1 Work Breakdown Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . 233.2 Schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263.3 Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

3.3.1 Manpower . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283.3.2 Budget . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

3.4 Outreach Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313.5 Risk Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

4 Experiment Design 364.1 Experiment Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 364.2 Experiment Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

4.2.1 Mechanical Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . 384.2.2 Thermal Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . 394.2.3 Electrical Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

4.3 Experiment Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 404.3.1 Electrical Components . . . . . . . . . . . . . . . . . . . . . . . . . . 404.3.2 Mechanical Components . . . . . . . . . . . . . . . . . . . . . . . . . 41

4.4 Mechanical Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 434.4.1 Chaff properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 434.4.2 Chaff capsule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 434.4.3 Free fall system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 454.4.4 Structure and protection . . . . . . . . . . . . . . . . . . . . . . . . . 464.4.5 Electronic box . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 484.4.6 Fixing and manipulation interfaces . . . . . . . . . . . . . . . . . . . 484.4.7 Mechanical components . . . . . . . . . . . . . . . . . . . . . . . . . 48

4.5 Electrical Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49


- 5 -

4.5.1 Block Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 494.5.2 Microcontroller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 494.5.3 Sensors and Actuators . . . . . . . . . . . . . . . . . . . . . . . . . . 504.5.4 PCB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 514.5.5 Data storage and Communication . . . . . . . . . . . . . . . . . . . . 514.5.6 Camera . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

4.6 Thermal Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 524.6.1 Thermal Environment . . . . . . . . . . . . . . . . . . . . . . . . . . 524.6.2 Overall Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 534.6.3 Internal Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . 544.6.4 Calculations and Simulation Reports . . . . . . . . . . . . . . . . . . 54

4.7 Power System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 554.8 Software Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

4.8.1 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 564.8.2 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 564.8.3 Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

4.9 Ground Support Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

5 Experiment Verification and Testing 625.1 Verification Matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 625.2 Test Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

5.2.1 Planned Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 665.2.2 Test Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

5.3 Test Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

6 Launch Campaign Preparations 73

7 Data Analysis and Results 747.1 Data Analysis Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

7.1.1 Analysis Strategy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 747.2 Launch Campaign . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

7.2.1 Flight preparation activities during launch campaign . . . . . . . . . . 757.2.2 Flight performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . 757.2.3 Recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 757.2.4 Post flight activities . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

7.3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 757.3.1 Expected Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

7.4 Lessons Learned . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

8 Abbreviations and References 778.1 Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 778.2 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

A Experiment Reviews 81

B Outreach 82

C Additional Technical Information 83


- 6 -

D Checklists 85

E Simulations 86E.1 Model of chaff dipole motion . . . . . . . . . . . . . . . . . . . . . . . . . . 86E.2 Model of stratospheric environment . . . . . . . . . . . . . . . . . . . . . . . 89


- 7 -

PREFACE

The Rocket and Balloon Experiments for University Students (REXUS/BEXUS) programmeis realized under a bilateral Agency Agreement between the German Aerospace Center (DLR)and the Swedish National Space Board (SNSB). The Swedish share of the payload has beenmade available to students from other European countries through a collaboration with theEuropean Space Agency (ESA).

EuroLaunch, a cooperation between the Esrange Space Center of SSC and the Mobile RocketBase (MORABA) of DLR, is responsible for the campaign management and operations of thelaunch vehicles. Experts from DLR, SSC, ZARM, and ESA provide technical support to thestudent teams throughout the project.

The Student Experiment Documentation (SED) is a continuously updating document regardingthe BEXUS student experiment R2C2 - (Radar Recognition of Chaff Clouds in the stratosphere)and will undergo reviews during the preliminary design review, the critical design review, theintegration progress review, and final experiment report.

The R2C2 Team consists of a diverse and inter-disciplinary group of students from Lulea Uni-versity of Technology’s Masters program in Space Engineering and and Spacecraft Design. Theteam members come from different engineering and scientific backgrounds, namely AerospaceEngineering, Software Engineering, Electronics and Communication Engineering, Automaticsand Robotics, Mechatronics and Motion Control and Physics.


- 8 -

Acknowledgements

The R2C2 team wishes to acknowledge the invaluable support received by the REXUS/BEXUSorganizers, SNSB, DLR, ESA, SSC, ZARM, Esrange Space Centre, and ESA Education. Inparticular, the team’s gratitude extends to the following project advisers who show specialinterest in our experiment:

1. Dr. Thomas Kuhn, Associate Professor at Lulea University of Technology (LTU).

2. Mr. Olle Persson, Operations Administrator at Lulea University of Technology (LTU).A former REXUS/BEXUS affiliate, Mr. Persson has been providing guidance based onhis experience.

3. Ms. Kanika Garg, PhD Studentat at Lulea University of Technology (LTU).

4. Prof. Reza Emami, Professor and Chair of Onboard Space Systems at Lulea Universityof Technology (LTU).


- 9 -

1 Introduction

1.1 Scientific Background

Stratospheric balloons are high-altitude balloons that are released into the stratosphere. Theyare the only type of balloons that can be operated in this region of the atmosphere (15 to 45km in altitude), which is too low for satellites, too high for aircraft and cleared too quickly byrockets [1]. They generally serve as weather balloons or are used as a platform for conductingexperiments in a near-space environment; to study the the atmosphere, its chemistry and dy-namics; or for technology demonstrators in the upper atmosphere. In order to be able to floatin the thin atmosphere, stratospheric balloons are filled with gas, typically helium or hydrogenand more rarely also methane.

The navigation of these balloons is nowadays rather limited as only the flight altitude ofthe balloon can be directly influenced by either releasing ballast—letting the balloon rise—orby releasing gas—which will result in the balloon descending—. All horizontal movement ofstratospheric balloons is caused by winds carrying the balloon. In theory these winds could beused for indirect navigating of the balloon, however, there needs to be a way of characterizingthem before being able to use them efficiently. According to most models winds blow in dif-ferent directions at different altitudes in the stratosphere. Therefore it should be possible tosteer the balloon at an altitude, where the wind currents carry it into a desired direction. Thedifficulty thereby is to measure the direction and speed of the wind in the vicinity of the balloon[2]. The most commonly used method nowadays is to use the balloon itself as a probe. Theballoon is made to ascend and descend until an altitude with wind in the desired direction isfound. This method uses the resources of the mission, namely gas and ballast, which reducesthe possible mission duration. What is needed to prevent this are new methods to measurethe winds around high altitude balloons.

Since the air in the stratosphere is quite thin, the question is which particles to observeto measure the winds from their movement. One possibility is to introduce artificial particlesthat then can be tracked [3]. A proven method is to use chaff [4, 5, 6, 7, 8]. Chaff consists ofa lot of thin pieces made from conductive materials for example from aluminium or metallizedglass fibre or plastic. The chaff pieces have a very small mass to surface ratio α, for examplein the shape of micrometer thin foil. This makes the single chaff pieces receptive to air drag,leading to a relatively slow drop even in thin air. When released into the air, the conductivechaff forms a cloud that reflects radar signals. In typical applications for wind measurementsthe single chaff pieces act like half-wave dipoles for the used radar signals [9]. In typical appli-cations for wind measurements the single chaff pieces act like half-wave dipoles for the usedradar signals [4]. To measure wind, a chaff cloud is released into the air. The position of thischaff cloud is tracked using a radar while it slowly descends. From the derivatives of the chaffcloud position the local wind speed and directions can be determined. Chaff has been usedfor wind measurements mostly at altitudes between 49 km to 95 km [10].


- 10 -

There is strong evidence suggesting that the winds in the stratosphere are structured into hor-izontal layers with a vertical extension in the order of 102 m [11]. Within each layer the windcan be described by nearly inertial oscillations added to a mean flow. The wind flows almostcompletely horizontal. Its speed and direction change only slightly and in smooth variations.Between two layers there is a thin layer with abrupt changes in the wind. Vertical wind profilesfrom successive soundings have shown that these layers remain stable over a duration of a fewhours at least and they have a horizontal expansion of the order of hundreds of kilometers[12]. The ideal scenario for balloon navigation would be to detect such a stable layer with ahorizontal wind in the desired direction and then navigate the balloon vertically into this airflow.


- 11 -

1.2 Mission Statement

As of now, an efficient way to navigate a balloon at high altitude does not exist. Thisexperiment seeks to test a method of navigating balloons by releasing and tracking with radara chaff cloud. The data collected will be used to infer the wind behavior below the balloonin order to find a suitable wind layer that will take the balloon in the desired direction. High-altitude balloons could then be steered by changing the flight altitude to a height wherethe wind will carry the balloon in a desired direction. Of special interest is to determine ifhorizontal layers in which the wind moves in an organized fashion, as most current modelsof the stratosphere propose, do exist. Such layers would be ideal to carry the balloon in acertain direction for long periods of time. The existence of these layers will be inferred by theconsistency in different measures through the release of different chaff clouds.


- 12 -

1.3 Experiment Objectives

The primary objectives of the R2C2 experiment are:

Obj.P.01 To measure the speed and direction of the wind below the BEXUS balloonObj.P.02 To analyze the gathered data in order to determine the feasibility of this method

to navigate balloons at high altitude.Obj.P.03 Development of a system capable of safely releasing chaff clouds from a balloon.

The secondary objectives of the R2C2 experiment are:

Obj.S.01 Analysis of the effects that different shapes and sizes of chaff foil would havein the dynamics of the chaff cloud. This is intended to provide a first as a firstapproximation so as to discern which would be the optimal foil size and shapethat future experiments could work from.

Obj.S.02 Analysis of the gathered data regarding the wind structure of the stratosphereand comparison to the typical model of horizontal wind layers.


- 13 -

1.4 Experiment Concept

The R2C2 experiment will release chaff clouds from the BEXUS balloon and measure theirposition as they descend until the clouds are completely dispersed.

The payload on the balloon carries six capsules with chaff probes. Fig. 1 shows a diagramof all hardware components. Because chaff consists of small conductive pieces, chaff piecesentering electronic systems might lead to short circuits. R2C2’s chaff release system preventsthe chaff from coming near other experiments and the BEXUS gondola. Each probe can beindividually released. For a release a chaff capsule is dropped in free fall. At a safe distancebelow the gondola, a line abruptly stops the fall. This shall from now on be called the catch.The shock from the catch is used to open the capsule and release the chaff probe. The probethen forms a chaff cloud that will be tracked to measure a wind profile over its descend path.The tracking is performed by an external ground-based radar. R2C2 will obtain the positiondata measured by this radar for later analysis.

Multiple releases are planned during the whole BEXUS flight. This will allow a comparison ofdifferent wind profiles and different types of chaff can be tested. As stated in the objectives,R2C2 aims to compare different sizes and shapes of chaff foils in order to provide a first ideaof which kind of foil would be ideal to measure wind profiles.

Figure 1: Block diagram showing all components of the R2C2 experiment hardware. Thepayload consists of the main payload and six release modules. In addition to that there is aconnection to the ground station for processing of payload data. The position data is measuredby an external radar system.


- 14 -

1.4.1 Experiment time-line

The work-flow of the experiment is illustrated in Fig. 2. Once the BEXUS balloon passes20 km altitude on its ascent, it reaches the region that is interesting for high-altitude balloonnavigation. Research balloons typically reach altitudes between 18 and 50 km. When releasingchaff at 20 km, the altitudes that can be probed with descending chaff clouds already extend2 km within the interesting region. At 20 km altitude the first chaff probe is released and theradar starts tracking. This marks the start of the release sequence. Five further chaff cloudswill be released. The second release occurs 25 min after the first and the following releases atintervals of 35 min. After the last release the system will be secured for landing.

This procedure allows the experiment to collect as much data as possible during the flight. Itis not necessary to perform all proposed measurements to perform a data analysis regardingR2C2’s objectives. The amounts of releases and the timing of the releases can be modified ifnecessary.

T + 4200

last Release

1st Release

T + 5400 T + 7500 T + 9600 T + 11700 T + 13800

20 km 20 Km

Altitude

Time [s]

26 Km 26 km

Figure 2: Experiment time-line.


- 15 -

1.5 Team Details

Niels de Graaf - Management Division

Current Education: SpaceMaster Round 14, Lulea Uni-versity of Technology

Previous Education: BSc in Mechatronics and MotionControl

Responsibilities: Team leader

Nehir Schmid - Scientific Division

Current Education: Master in Spacecraft Design,Lulea University of Technology

Previous Education: BSc in Physics

Responsibilities:data analysis, simulations developer,funding research

Daniel Royo Serrano - Management Division/Doc-umentation

Current Education: Master in Spacecraft Design,Lulea University of Technology

Previous Education: BSc. in Aerospace Technology En-gineering

Responsibilities: Deputy team leader, documentation,funding research

Aydin Nakhaee-Zadeh Gutierrez - Systems Engi-neering/Software Division/Radar Expert


Previous Education: BSc. in Aerospace Engineering inTelecommunications

Responsibilities: Head of system engineering, radar ex-pert and member of the software department

Maximilian Zach - Mechanical Division/SystemsEngineering


Previous Education: Bachelor’s Degree in Aviation

Responsibilities:


- 16 -

Kiran Tikare - Electronics/Software Division

Current Education: Masters in Space Science and Tech-nology, Lulea University of Technology

Previous Education: Bachelors in Electronics and Com-munication Engineering

Responsibilities: Head of Electrical and Electronics Divi-sion, Member of Software Department

Guillermo Zaragoza Prous - Software


Previous Education: Master’s in Automatics andRobotics; Bachelor’s in Software Engineering Responsi-

bilities: Software development and design

David Villegas Prados - Mechanical Division


Previous Education: BSc in Aerospace Engineering

Responsibilities: Head of mechanical team

Adam Hoehne - Thermal


Previous Education: BSc in Materials Engineering

Responsibilities: Thermal design

Max Buhrer - Outreach


Previous Education: BSc. in Aerospace Informatics

Responsibilities: Outreach and Funding


- 17 -

2 Experiment Requirements and Constraints

2.1 Functional Requirements

F.01.: The experiment shall measure the wind currents in the stratosphere below the BEXUSballoon during flight.

F.02.: The experiment shall release chaff probes.

F.03.: The experiment shall be able to release different types of chaffs.

F.04.: The movement of the chaff cloud shall be tracked by radar.

F.05.: The radar should be able to define the size and shape of the chaff cloud.

F.06.: The chaff shall not interfere with other experiments.

F.07.: The chaff shall not interfere with the gondola.

F.08.: The experiment shall measure the position of the gondola.

F.09.: The experiment shall measure the air pressure of the environment around the gondola.

F.10.: The experiment shall measure the temperature of the environment around the gondola.

F.11.: The experiment shall measure the humidity of the environment around the gondola.

F.12.: The experiment shall execute a system performance check of the release system.


- 18 -

2.2 Performance Requirements

Derived from F.01.:

P.01.: The experiment shall measure the wind speed within an error of ± TBD m/s. 1

P.02.: The experiment shall measure the wind directions within an error of ± TBD.

P.03.: The experiment shall measure the wind current vertical position within an errorof ± TBD m.

P.04.: The experiment shall measure the wind current horizontal position within anerror of ± TBD m.

Derived from F.02. and F.03.:

P.05.: The experiment shall release at least two types of chaff.

P.06.: The time between releases shall be higher than 12 min.

Derived from F.04.:

P.07.: The chaff cloud material shall be electromagnetically reflective.

P.08.: The chaff cloud released by the experiment shall be tracked by a radar at fre-quencies between 2.5 GHz and 10 GHz.

P.09.: The chaff cloud position shall be tracked within an error in the position of ±TBD m.

P.10.: The geometry of the chaff cloud shall ensure a minimum vertical speed of thechaff cloud of TBD and a maximum of TBD.

P.11.: The radar shall take measurements of the position of the chaff cloud with aminimum rate of TBD Hz.

Derived from F.05. and F.06.:

P.12.: The radar should ensure a maximum radial resolution of 1000 m.

P.13.: The radar should ensure a maximum angle resolution of 1.0 for 100 km.

Derived from F.07.:

P.14.: The chaff cloud shall be released at a safety distance of at least 18 m below thegondola.

Derived from F.08.:

P.15.: The experiment shall measure the position of the gondola within an error of ±32 m.

P.16.: The experiment shall obtain position measurements of the gondola with a ratehigher than 1 Hz.

Derived from F.09.:

1This requirement will be subject to the


- 19 -

P.17.: The experiment shall measure the air pressure around the gondola within an errorof ± 0.1 hPa .

P.18.: The experiment shall obtain pressure measurements of the the environmentaround the gondola with a rate higher than 1 Hz.

Derived from F.10.:

P.19.: The experiment shall measure the temperature of the environment around thegondola with an error of ± 1C.

P.20.: The experiment shall obtain temperature measurements of the environmentaround the gondola with a rate higher than 1 Hz.

Derived from F.11.:

P.21.: The experiment shall measure the humidity of the the environment around thegondola with an error of ± 0.5%.

P.22.: The experiment shall obtain humidity measurements of the the environmentaround the gondola with a rate higher than 1 Hz.

Derived from F.12.:

P.23.:The experiment shall give feedback of each procedure step done by the experiment.


- 20 -

2.3 Design Requirements

D.1.: The experiment shall be able to operate within the limits of the temperature profile ofthe BEXUS balloon during the flight and launch.

D.2.: The experiment shall be able to operate within the limits of the pressure profile of theBEXUS balloon during the flight and launch.

D.3.: The pressurized parts of the experiment shall support 1.5 the working pressure.

D.4.: The pressurized parts of the experiment shall be able to operate at environmentalpressure down to 5 hPa.

D.5.: The experiment shall be able to operate within the limits of the vibration profile of theBEXUS vehicle during the flight and launch.

D.6.: The total mass of all payload shall not exceed 22kg.

D.7.: The payload shall fit in a box of dimensions 500 mm x 400 mm x 400 mm.

D.8.: The experiment shall withstand a maximum vertical acceleration of 10 G.

D.9.: The experiment shall withstand a maximum horizontal acceleration of 5 G.

D.10.: The on-board communication system shall be compatible with the gondola´s E-linksystem.

D.11.: The down-link data rate to the ground station shall be lower than 205 Kbps .

D.12.: The ground station shall be compatible with the BEXUS ground E-net.

D.13.: The up-link data rate to the ground station shall be lower than 50 Kbps .

D.14.: The experiment´s power supply shall be compatible with the gondola´s provided power.

D.15.: The experiment DC current draw shall be lower than 1.8 A.

D.16.: The total power consumption of the experiment shall be lower than 374.4 Wh.

D.17.: The experiment shall be mechanically compatible with the gondola attachments.

D.18.: The experiment shall not disturb or harm any other experiments.

D.19.: The experiment shall not jam other experiments´ signals.

D.20.: The experiment shall not jam the E-link.

D.21.: The experiment shall ensure that the density of the chaff cloud before touching theground is be less than 40 µg

m3 .

D.22.: The chaff foils shall not be inhalable.


- 21 -

2.4 Operational Requirements

O.1.: The experiment shall be able to automatically continue the performance in case com-munication with ground station is lost.

O.2.: The experiment shall be able to autonomously disable releases for security reasons.

O.3.: The experiment shall be able to monitor the status of the gondola.

O.4.: The experiment shall be able to rearrange the timing of the releases.

O.5.: The experiment should notify to the ground station the release time with at least 1 minprior to the release.

O.6.: The ground station shall be able to monitor the experiment.

O.7.: The ground station shall be able to control the experiment.

O.8.: The experiment shall store the status of the experiment (Housekeeping data) duringthe BEXUS flight.


- 22 -

2.5 Constraints

• The Radar characteristics will depend on the available radar, so it is possible that notall the radar requirements can be fulfilled and therefore some of the objectives of theexperiment.

• The schedule will be mainly defined by each of the project revisions. In order to facethis constraint a project plan has been made taking into account the human resourcesand possible delays.

• The manpower will depend on the computed workload and availability of each of themembers during the duration of the BEXUS project. It is expected that each of theteam members dedicate 20 hours per week to R2C2 BEXUS project.

• A preliminary budget estimation of 3300 Euros has been made, which might changeduring the duration of the project. The budget will be one of our main constrains as itdepends on the sponsors.


- 23 -

3 Project Planning

3.1 Work Breakdown Structure

The R2C2 team is divided in different categories responsible for the several aspects and chal-lenges rising from the project as shown in 3. Each group has a devoted leader that will reportto the management division. In this way the project manager can divide the tasks accordingto how each division progress.

The management is divided between 3 members. The project manager is responsible for divid-ing the tasks. He allows a smooth communication between the different division and organizesactivities when multidisciplinary tasks are needed to be performed in the critical developmentphases of the project. He analyzes the risks within the project and presents the projectsprogress in front of stakeholders A second member is in control of the documentation andthe task of setting up contact with sponsors and partners and maintaining and maintainingthese relationships. A third member is responsible for the outreach and online content making.

The systems engineering division is in charge of defining setting up contact with sponsors andpartners and maintaining , the performance requirements, discuss the design requirements withthe different divisions and create a risk analysis. This will be used to design test plans thatwill ensure that the functionalities of the system are complying with the requirements.


- 24 -

Figure 3: Work division breakdown.

The mechanical division is responsible for designing the different parts needed for the experi-ment including the structure placed in the gondola, the reeling system and the chaff releasingcontainers. Activities such as CAD designing, component selection, manufacturing, risk anal-ysis simulation in order for the components to meet the requirements and testing are amongthe mechanical division team responsibilities.

The electrical division will design the circuitry, select the necessary electrical componentsand perform the necessary tests indicated by the risk analysis.

One team member is in charge of the thermal challenges that the experiment will experience.This includes analyzing the amount of thermal shielding that the electrical and mechanicalcomponents should need and if the use of thermal heating systems is also needed.

The Software division will be responsible for creating the software architecture, including thesoftware used on board for the micro controllers connected with different sensors and actua-tors used for performing the experiment, the communication with the ground station and theinterface of the ground station to easily control the progress of the experiment.


- 25 -

As finding an appropriate radar is of the utmost importance for the experiment to be a success,a radar division has also been created. This division is responsible for providing the necessaryknowledge regarding radars and their working principle to the rest of the team; perform simu-lations in order to define the radar specifications according to this knowledge; and contactingthe different radar stations that fits these specifications.

Finally, the scientific division will simulate the dynamics behavior of the winds in the strato-sphere and its interaction with the chaff. From this, the more appropriate types of chaff willbe determined, as well as deriving a methodology to analyze the data after the experimentis carried out. All results will be made available to the scientific community once the projectfinishes.


- 26 -

3.2 Schedule

The schedule proposed by the team is presented in the Gantt chart of figure 4. The due datesfor the student reports are approximated and the exams periods have been included in order toremark possible work load from the University activity. Besides, some activities are overlappedas they can be done in parallel, including possible synergies between them.


-27-

Figure 4: Team’s Gantt chart schedule.

BX

29R

2C2

SE

Dv1-0

16Jan19

- 28 -

3.3 Resources

3.3.1 Manpower

The background of the R2C2 team members is summarized in Table 3.

Team Member Background and project related experience

Niels De Graaf BSc. in Mechatronics and Motion ControlNehir Schmid BSc. in PhysicsDaniel Royo Serrano BSc. in Aerospace Technology EngineeringAydin Nakhaee-zadeh Gutierrez BSc. in Aerospace Engineering in TelecommunicationsMaximilian Zach BSc. in EngineeringKiran Tikare B.E. in Electronics and CommunicationGuillermo Zaragoza Prous BSc. in Software Engineering and MSc. in Automatics

and RoboticsDavid Villegas Prados BSc. In Aerospace EngineeringAdam Peter Hoehne BSc. in Mechanical and Materials EngineeringMaximilian Peter Hoehne BSc. in Mechanical and Materials Engineering

Table 3: Background and project related experience of team members.

An estimation of the projected effort required by all team members for the different stages ofthe project is detailed in Table 4.

Stage Duration (weeks) Effort (hours)Preliminary Design 10 1800Critical Design 6 1080Experiment Building, Testing and Integration 14 2520Final Experiment Preparations 6 1080Launch Campaign 1 180Data Analysis and Reporting 4 720

Table 4: Project Effort Allocation per Project Stages. The number of weeks between eachstage has been estimated by the calendar in previous BEXUS rounds.

As the number of team members is nine, it is expected that the effort contributed by eachteam member will average twenty hours per week or 820 hours in total.


- 29 -

As of now, all R2C2 members are based in Kiruna, Sweden and enrolled in a LTU Masterprogram. However, only three team members are expected to remain in Kiruna for the wholeduration of the project. The rest of the team is expected to continue their studies in partneruniversities of LTU across Europe. This, however, does not mean that they will no longer beinvolved in the project but it is safe to say that coordinating efforts will prove to be difficultif the team members are not based in the same location. It is therefore critical that theteam advances the project as much as possible before relocating away from Kiruna. It is ourintention to work on the project through the summer, as the team members will not have yetany commitments in their new universities. However, actual availability and work commitmentsof the team members over the summer still need to be negotiated and finalized.


- 30 -

3.3.2 Budget

LTU will provide financial assistance to the tune of 2500 SEK for every team member that isenrolled in a project course at LTU. Other potential sources of funding that will be pursuedinclude:

1. The Swedish National Space Agency, SNSA, will be reached out to during their nextopen call to researchers in Sweden to apply for funding for Space Research, includingEarth Observation Research.

2. Meteorological institutes, research initiatives, researchers, academic institutions, andinstitutional donors involved in climate change will be reached out to for contributionsbased on the interest of collaborating in the experiment.

3. Third-party providers of required equipment, components, and materials will be ap-proached with an opportunity for these providers to sponsor the project through donationbefore considering the related expenses. Visibility of the experiment through the plannedoutreach programs will serve as a visibility incentive to encourage such contributions.


- 31 -

3.4 Outreach Approach

The main public relations efforts will be made through the R2C2 website and social medianetworks such as Facebook, Instagram and Twitter. Besides detailed technical and scientificdocumentation and media content published on the website, a more comprehensive languageused in social media posts is targeted to a broader audience that is not necessarily familiar tothe topic.

Furthermore, the website features a blog-like sub page, where the current progress is describedin greater detail to complement the posts on social media. An extended list of the web pagesections, as well as links to all the social media sites can be found in Appendix B.

Video footage of experiment building and testing will be published on a dedicated YouTubechannel.

In addition to the efforts mentioned above, project updates will also be shared on Snapchat.This service promises an interactive experience for the community and thanks to its popularityamong the younger generation might spark their interest in the aerospace field.

A next step will be the project promotion on leading crowdfunding platforms such as Kickstarteror GoFundMe.


- 32 -

3.5 Risk Register

Risk ID

TC – Technical/Implementation

MS – Mission (operational performance)

SF – Safety

VE – Vehicle

PE – Personnel

EN – Environmental

OR - Outreach

BG - Budget

Adapt these to the experiment and add other categories. Consider risks to the experiment, tothe vehicle and to personnel.

Probability (P)

A Minimum – Almost impossible to occur

B Low – Small chance to occur

C Medium – Reasonable chance to occur

D High – Quite likely to occur

E Maximum – Certain to occur, maybe more than once

Severity (S)

1. Negligible – Minimal or no impact

2. Significant – Leads to reduced experiment performance

3. Major – Leads to failure of subsystem or loss of flight data

4. Critical – Leads to experiment failure or creates minor health hazards

5. Catastrophic – Leads to termination of the REXUS/BEXUS program, damage to thevehicle or injury to personnel

The rankings for probability (P) and severity (S) are combined to assess the overall riskclassification, ranging from very low to very high and being coloured green, yellow, orange orred according to the SED guidelines.

Whether a risk is acceptable or unacceptable has been assigned according to the SED guide-lines. Where mitigation is written for acceptable risks this details the mitigation undertakenin order to reduce the risk to an acceptable level.


-33-

ID Risk (& consequence if) P S P * S Action

TC10 Software fails to store data B 2 Very LowAcceptable Risk: Extensive testing will be done. Usingtelemetry, most of the data gathered from sensors will besent to ground station.

TC20 Failure of several sensors B 2 Very LowAcceptable Risk: Thermal test (Test Number 5) to approvethe functionality of the experiment.

TC30 Critical component is destroyed in testing B 1 Very LowAcceptable Risk: Spare components can be ordered but forexpensive ones, they will be ordered and tested early in theproject in case we need to order more.

TC40Electrical connections dislodges or short cir-cuits because of vibration or shock

B 4 Low

Acceptable Risk. D-sub connections will be screwed in place.It will be ensured that there are no loose connections andzip ties will be used to help keep wires in place. Carefulsoldering and extensive testing will be applied.

TC50Experiment electronics fail due to long expo-sure to cold or warm temperatures

B 3 LowAcceptable Risk: Thermomechanical and thermoelectricalsolutions will be simulated and tested in detail to help preventthis from happening

TC60Software and electrical fail to control heaterscausing temperature to drop or rise below orabove operational rang

B 2 Very LowAcceptable Risk: Tests will be performed prior to the flight todetect and minimize the risk of occurrence.The system willbe analyzed prior to flight and tested extensively on reliability.

TC70On-board memory will be full (flight timelonger than expected)

A 2 Very LowAcceptable Risk: The experiment shall go through testingand analysis to guarantee the onboard memory size is suffi-cient.

TC80 Communication loss with ground station A 2 Very LowAcceptable Risk: Experiment will be designed to operateautonomously.

TC90Software fails to control release mechanismsautonomously

B 2 Very Low Acceptable Risk: Extensive testing will be done.


TC100 Complete software failure B 4 LowAcceptable Risk: A long duration testing (bench test) willbe performed to catch the failures early.

BX

29R

2C2

SE

Dv1-0

16Jan19

-34-

TC110 Release Mechanism Fails B 2 LowAcceptable Risk: Several releases planned. Extensive testingwill be conducted.

TC120Radar is experiencing issues with tracking thechaff.

B 4 LowAcceptable Risk: Prior Tracking tests will be conducted.Communication with Radar company to ensure functionaltracking.

MS10 Down link connection is lost prematurely. B 2 Very Low Acceptable Risk: Data will also be saved on SD card.

MS20Experiment lands in water causing electronicsfailure

B 1 Very Low Acceptable Risk: Data will not be stored on board.

MS30 Balloon power failure. B 2 LowAcceptable Risk; Residual chaff stays in containers if poweris lost.

MS30 Solenoids (only moving parts) freeze. C 3 LowShielding, Coating and Heating will be installed to preventfreezing. Thermal analysis will be conducted.

SF10 Rope failure of free fall system. B 4 LowAcceptable Risk: Analysis and testing will be conducted toavoid rope failure.High Safety margin.

SF20 Chaff interferes with experiments. B 4 LowAcceptable Risk: Sensors will help releasing chaff only in safeconditions.

SF30 Chaff creates environmental issues. A 2 Very LowAcceptable Risk: Amount and size of chaff will not be prob-lematic to the environment. Chaff limits on ground will notbe exceeded.

VE10 Gondola Fixing Interface. B 1 Low

Acceptable Risk: The experiment box could detach from thegondola’s rails and the two boxes could detach one from theother. The experiment will be secured to the gondola and toeach other with multiple fixings. These will also be tested.

VE20 Hard Impact. B 1 Very LowAcceptable Risk: The experiment does not rely on data ormaterials stored in the gondola.

BX

29R

2C2

SE

Dv1-0

16Jan19

-35-


PE10 Team Member leaves the team. C 3 LowAcceptable Risk: Subteams always consist of at least 2 peo-ple to avoid open spots. Workload evenly separated betweenremaining team.

PE20Team members from the same division areunavailable during the same period over thesummer.

C 2 LowAcceptable Risk: Team will be coordinated so that each teamhas at least one available representative, also management.

PE30Miscommunication between team membersresults in work being incomplete or inaccu-rate.

B 3 Very LowAcceptable Risk: The use of ”freedcamp”(PM-tool) will en-sure members know their assigned work and deadlines. Com-munication via WhatsApp and regular meetings support this.

PE40 Internal problems between team members. B 2 Very LowAcceptable Risk: Team Building department enrolled tomeet apart of BEXUS work and support bonding.

Table 7: Risk Register.

BX

29R

2C2

SE

Dv1-0

16Jan19

- 36 -

4 Experiment Design

4.1 Experiment Setup

The experiment is a system consisting of the payload, the ground based radar and the studentsbased in Esrange controlling the mission. The payload will transmit data of the condition ofthe balloon and release chaff by reeling down the containers, the ground based radar will trackthe chaff clouds and the student base will receive the on board data and active the chaffreleases.

The system of payload is illustrated in 5. The main structure will be a cuboid made ofaluminum profiles in which the different parts of the payload will be attached to the gondolaof the balloon. The structure is designed to be fixed to a bottom corner of the gondola orin the middle of one side of the bottom. However, attaching it to a corner will bring morestrength by constraining the experiment at more sides and make it safer.

The cuboid is divided in two different modules. The Releasing Module and the Electronic box,located next to the RM structure and is used for placing the electronics of the mission. Thisarrangement is made in order that the mechanical parts does not interfere with the electronicsand the wiring interfacing the rest of the balloon system including the communication for downlink. The RM structure is used for the reeling down system, all the parts needed to get thechaff containers at a safety distance from the gondola for releasing the chaff. In the lower partof the structure the chaff containers will be placed along with the module for activating thefree fall of the chaff container.

Figure 5: Main structure of the experiment.

The central component of the electronics are the microcontrollers that are regulating all thesensors and the actuators on board, as well linking the communication with the rest balloonfor down and up link communication. The PCB’s are used for placing all the componentsneeded for the sensors to work at their nominal framework. Most of these components will beplaced in the electronic protection box. Moreover the camera will be placed in the electronic


- 37 -

box to be protected from the environment and have a focus on the performance of the releasesystem and the chaff deployment. The electronics part is explained with more detail in theelectrical design subsection.

The reeling down system consists of a set of pulleys with rolled ropes that are from Dyneema®Line, very stiff material, to prevent from breaking when released. The idea of using this ma-terial is inherited from a previous BEXUS project reel.SMRT. Each chaff container is releasedindividually and the cables have different lengths to avoid collision. To ensure that friction isminimized all the pulleys are mounted to rods in traversing the center of the structure usingball bearings.The mechanism if further explained in the mechanical design.

The containers are attached to the rope and placed at the bottom of the structure on trapdoors that are triggered by solenoids. When electrical current is flowing through the solenoid,it retracts a pin holding the trap door, letting the chaff container fall out of the structure. Thecontainers are designed in a way that the containers completely open up with the tension ofthe rope when hanging below the gondola.

The way that the different parts of the system interact and their function is summarized inthe block diagram 1.

Figure 6: Context block diagram of the experiment.


- 38 -

4.2 Experiment Interfaces

4.2.1 Mechanical Interfaces

The experiment will be fixed to the gondola rails by means of 90 degree aluminum brackets.The outside structure of the experiment box will be fixed to one face of the bracket with thehammer nut in the rails of the structure profile. The hammer nut will penetrate the aluminumsheet which covers the experiment, the bracket, the washer which will allow dissipation ofstresses and the nut, in the respective order. The face fixed to the gondola rails will also havethe hammer nut in the rails and the nut to secure it. The sketch of one attachment point isobserved in Figure 7.

Figure 7: Sketch of one interface between the experiment profile and the gondola rails.

This structure will be repeated 5 times for each rail for a total of 10. The bottom of theexperiment should mounted exposed to the outside in order to be able to proceed with thechaff release. Since the experiment does not have a direct bottom support provided by thegondola, sufficient tests and simulations regarding the shock produced by the chaff modulewhen it reaches the lowest point of the release will be done. To ensure the stability of theexperiment inside the gondola, any additional brackets or structural support will be determinedby those tests with the typical safety factor used in engineering between 2-2.5 [13]. Theelectronic box (EB) will be also be fixed with the same procedure as before using the rails andprofile structure.

If it is possible, the experiment could benefit from being located in a corner of the gondola.Then, using the vertical beam as an extra rail, more fixations will be placed providing morestability.


- 39 -

4.2.2 Thermal Interfaces

The thermal interfaces of the experiment coincide with the mechanical interfaces as the primaryform of heat transfer is through conduction. The generation of heat would come from the useof the the electronics and the heater used to keep the electronics within the operating rangeof temperature. The outside facing walls and the bottom of the payload would be the thermalinterface with the cold outside air and will be well insulated. The walls that are protected bythe gondola are thermally variable due to other experiment requirements, this thermal interfaceis minimally insulated to provide a constant temperature. The heat sink interface would bethe connection to the gondola chassis.

4.2.3 Electrical Interfaces

There are two electrical interfaces with the experiment to be listed. The Ethernet cableconnected to the Ethernet module of the microcontroller in the electronic box of the payload.This is to downlink and uplink the data to the student ground station. In addition there isa power interface of 2 cables going from the batteries of the gondola to the power converterinside the electronic box feeding most of the electronics used for the experiment.


-40-

4.3 Experiment Components

4.3.1 Electrical Components

Here are listed all the electrical components that will be on board the gondola.

ID Component Weight Size No. Cost Availability Status NotesE1 Microcontroller 45.35g 7.9x5.6x2.6 cm 2 20€ Available - arduino unoE2 GPS module+Antenna 200g 3.5x4.6cm 1 40€ Available - 3m long cable antennaE3 Altitude sensor 50g 2.426x2.426 cm 1 25€ Available - E-barometerE4 T° Sensor 50g 5x0.6cm 2 50€ Available -E5 Humidity sensor 30g 1.6x2.5x0.8 cm 2 10€ Available -E6 Limit switch 0.5x0.6x0.1cm 6 40 2€ - -E7 Solenoid 225g 5.77 x 2.54 x 3.18 cm 6 20€ Available -E8 Ethernet module 50g 1.5x4x1cm 1 10€ Available -E9 SD module 30g 1x1.5x0.2 cm 2 10€ Available -

E10 Camera 500g 10x5x5cm 1 50€ Available - -E11 DC-DC converters - - - - - - -

Table 8: Electrical components, weight, availability and cost.

BX

29R

2C2

SE

Dv1-0

16Jan19

-41-

4.3.2 Mechanical Components

Table 9 shows the different components required for the manufacturing of the unit, as well as tentative estimation of the size and mass. Thecost of such elements will be determined in the later stage.

ID Component Size Mass no. Cost Availability Status Notes

M1 Bracket 20x20mm -30+(6)

TBD StoreNotordered

90°.

M2 Hammer nut M8x1.25 - 30 TBD OnlineNotordered

M3 Washer M8x1.25 -30+(6)

TBD StoreNotordered

M4 Nut M8x1.25 - 30 TBD StoreNotordered

M5 Aluminum profile 1 40x40x300mm3 400g 18 TBD OnlineNotordered

Horizontal

M6 Aluminum profile 2 40x40x275mm3 380g 8 TBD OnlineNotordered

Vertical

M6Aluminum platetype I

380x275x2mm3 550g 10 TBD StoreNotordered

Normal platesto cover sideand top

M7Aluminum platetype II

300x300x10mm 510g 1 TBD StoreNotordered

Bottom plate, 6holes of 500mm

M8 Power lock M8 13.5x28mm 15g 24 TBD OnlineNotordered

Join aluminumprofile

M10 Corner fastener 40x40mm 65g 24 TBD OnlineNotordered

M11Aluminum cylindertype I

d=50mm 10g 6 TBD OnlineNotordered

Hollow cylinderl = 150mm

M12Aluminum cylindertype II


Hollow cylinderl = 800mm

BX

29R

2C2

SE

Dv1-0

16Jan19

-42-

M13Stainless steelhinge


M14Aluminum Trap-door

75x30mm 30g 6 TBD OnlineNotordered

Essentially analuminum plate

M15 Aluminum axle rod d=40mm 1.25kg 2 TBD OnlineNotordered

l = 300mm

M16Steel Pulley ballbearing

40mm inner,20mm race

500g 6 TBD OnlineNotordered

M17 Dyneema™ line 100m 0.76kg TBD OnlineNotordered

M18 ABS Container 20mm 50g 6 TBD LTUNotordered

M19 PCV pistil d=20mm 50g 6 TBD OnlineNotordered

M20 Chaff 10mmx2µm 100g 6 TBD LTUNotordered

Table 9: Mechanical components required with estimation of size, weight, availability and cost

BX

29R

2C2

SE

Dv1-0

16Jan19

- 43 -

4.4 Mechanical Design

The design proposed serves as a first approximation to estimate the order of magnitude ofeach component respect to the gondola cubic box.

4.4.1 Chaff properties

The entire purpose of the mechanical design is to safely deploy chaff below the gondola.Chaff will have the following properties explained in the table below. The material of thechaff is aluminum, therefore it is also very conductive the reason why the containers are madein a material avoiding electrostatic interaction. The chaff will be stored in containers, eachcontainer will have the equivalent of 100 grams.

Property Value

Material AluminumLength 0.5-15mm

Thickness 2 µmDensity 2702 kg/m3

Table 10: Properties of the chaff

4.4.2 Chaff capsule

The chaff capsule consists of two parts, a cylinder container and the“pistil”, a bar with a plateon the bottom and the top. The pistil is fixed and the container can move freely up and down.The container should have enough space inside so that chaff is not compact in its interior andallows a smooth and efficient exit. Because the container walls can move freely, when thecapsule is in the gondola, it will be supported by the trap door. When it is released the dragacting on the bottom face of the pistil will exert a force upwards which will avoid chaff fromgetting out. When the rope reaches the maximum length, the tension will stop the pistil fromgoing down, but the container will still go down until it is stopped by the bottom of the pistil,exposing all the chaff to the outside and releasing it.


- 44 -

Figure 8: Chaff capsule before being opened and after its opening.

The material of the chaff capsule should not be conductive or at least not interact with thechaff. This will prevent the electrostatic forces between the chaff to interact with the capsuleand the rest of the gondola. Therefore, since it is a simple design a thought approach is to3D print it with ABS (Acrylonitrile butadiene styrene). This material could be used accordingto the following considerations:

1. Wide temperature working range

2. High electrical resistivity, which insulates electrostatic forces which might be induced bythe chaff.

3. It is a non-static material. The problem of certain plastics is that they do not dissipatethe static electricity. Special fillers and fibers in ABS prevent this.

4. Valuable tensile strength.

5. Cheap to manufacture.

6. Availability of 3D printers at LTU.

The properties of this material are shown in Table 11. The fall is desired to be straight for thechaff to have a smooth disposal to the outside air and at the desired position. That meansthat the capsule should pull the rope down and not the other way around (which would meanthat the capsule will rotate and fall unpredictably). To fulfill such task the capsule should bemuch heavier than the rope. Moreover, the cylinder container should also be heavier than thepistil so that it does not open before reaching the length of the rope. In case ABS is not heavyenough for the capsule, different materials with similar properties will be studied.


- 45 -

Property Value

Density 1.25g/cm3

Thermal conductivity 0.1 W/mKElectric resistivity 108 ΩmUltimate strength 40 MPaElasticity modulus 2800 MPa

Elongation at break 50%

Table 11: Properties of ABS

4.4.3 Free fall system

The free fall system consist of the different components which will play a direct role in themovement of the capsule from the gondola to the releasing chaff position. Two design viewsof this system are shown in Figures 9 and 10.

Pulleys and rope: A shaft will be fixed to profiles in the middle of the structure using ballbearing fixtures. They will allow the pulley to rotate and maintain the chaff fixed. Then, usingseveral ball-bearing, the same shaft can be used for several capsule. It is important for theshaft to be fixed for a release to happen independently. Ball-bearing pulleys will be fixed onthe shaft on which the Dyneema™ lines will be wound on. When the trap-doors under thecontainers open, the rope will be unwound due to the containers pulling it down simply bygravity. The characteristics of the Dyneema™ line are shown in Appendix C Figure 21. Eachcontainer will be connected to a rope with a different length so that the containers do notcollide with each other when the reach the lowest position (since some lateral displacementsmight occur).

Trap-door: This is the only actuated part of the mechanical design, making a link betweenthe electronics and the chaff release. Each chaff container will be placed on one of the trap-doors that will be independent from each other. The trap doors made out of aluminum sheetwill be fixed parallel to the bottom plate of the structure using door fixtures. The other sideof the door will be held with a pin from a solenoid. The solenoid has the ability to retract thepin when current is going through its coil acting as a magnet. When the pin is retracted thedoor facing the bottom part will open with the door fixture. A spring with a pin will be placedagainst the fixture in order to prevent the trap door from opening and closing because of theexternal forces from the environment.

Cylinder Guide: Since the chaff capsule is hanging from the rope and supported by thetrap-door, a fixed hollow cylinder will be placed around the capsule. It will be attached tothe bottom plate to restrain the movement of each chaff capsule to avoid spilling of thechaff and it will extend down up to the trap-door, enclosing the capsule completely. Withthis configuration, protection is given to the gondola in case chaff spills when the trap-door isopened. The position of this cylinder will ensure that chaff will flow downward. Sufficient tests


- 46 -

will be carried to understand how chaff would flow in the case of spill. Also tests regarding howhumidity affects the chaff release will be carried and how this cylinder influences this release.

Figure 9: Schematic 3D design of the free falling system design with the different components.

Figure 10: Bottom view of the free falling system design with the different components.

4.4.4 Structure and protection

The whole external structure will be made out of aluminum strut profiles. They will allow asimple and secure mounting and operation. The experiment will have two different modules:the Releasing Module (RM) and the Electronic Box (EB) and they will be next to each other.


- 47 -

The critical structural design is the RM, since it will need to absorb the shock produced whenthe the rope is fully extended.

The profiles chosen are shown in Figure 11. The characteristic cross-section is 40 × 40mm.Bars will be joined together with power lock fastener. To reinforce the structure angle fastenerswill be added to each of the corners. In the case that tests show that more reinforcementis needed, strengthening elements 45 × 60° will be used for the corners. This features areobserved in figure 12

Figure 11: Cross-sectional area of profile bar

Figure 12: Structural bars and reinforcements.

The sides of the RM and the top will be cover with an aluminum sheet to prevent it from anyexternal factor. The bottom part will be divided into two different levels. The first level isan aluminum sheet with holes in it for the release of the capsules and the cylinder guide toprevent movement of the capsule. The second level will contain the trap-doors An horizontalbox will be added in the middle parallel to the ones of the structure to allow the electricalwires through it in their way to the solenoid, which will be place on such box. In the mostprobable case in which the solenoid will need heating, it will be placed inside this box also. Aside view of these two levels is can be inferred in 9 and 10.


- 48 -

4.4.5 Electronic box

Next to the structure all the electronics will be stored within a box made of PVC to contain allthe sensors and the microcontroller. The location of the EB is decided to be next to the RM toensure its integrity when the impulse force is produced by the falling capsule. The placementof the EB next to the RM will also allow the RM to be shorter, reducing its moment of inertiaand providing overall stability to the system. A layer of polyurethane foam will surround thebox below the PVC to prevent the electronics to be crushed during the experiment. Thislayer will also serve as insulating material which will allow electronics working at the desirableworking temperature. The box will be fixed as shown in figure 7.The protective layers will befurther explained in the Section 4.6 of this report as well as the requirements related to theworking temperatures of the components.

4.4.6 Fixing and manipulation interfaces

The EB and and RM will be fixed together by the profile bars with the same mechanismexplained before (power lock). They should be connected to allow the passage of wiresthrough it to reach the solenoid. Because of the easy mounting of the structure, the recoveryof the EB should not be a problem.

For manipulating the instrument once it is fixed to the gondola, the aluminum sheets of twoof the sides will be easily retractable (the ones perpendicular to the gondola rails). The topwill also be retractable to allow any possible change or adjust.

4.4.7 Mechanical components

All the components used in the mechanical design can be found in Table 9


- 49 -

4.5 Electrical Design

4.5.1 Block Diagrams

The electronics design is depicted in Figure 13. There is a major distinction in the designbetween the components inside the protected electronic box and the ones directly in theframe. Most of the sensors, microcontrollers, data storage, power converters and connectionwith the BEXUS communication and power supply will be protected by said box. Componentsthat will provide data about the environment conditions will be placed outside the box. Notethat the camera will be in the electronic box that will contain a hole for the lens. A powerconverter will be needed in order to be able to use the power source supplied by BEXUS, asall components chosen work with a current of 5V.

Figure 13: Block diagram for all Electronic components Showing the Signals and Power Con-nections.

4.5.2 Microcontroller

For the controlling of the components and communicating the data to the BEXUS communi-cation to the MGC a system of two Arduino UNO units will be used. Both microcontrollers


- 50 -

will be inside the electrical box and communicate with each other using I2C communication.One will be connected to the sensors and communicates the values. The other one is con-nected with Ethernet to the BEXUS communication and to the only actuators of the systemto launch the release system: the solenoids. Both Arduino units will be powered thought USBconnection to make use of

4.5.3 Sensors and Actuators

GPS sensor The experiment will use a GPS Arduino module that will be placed in theelectronic box. However, the antenna provided will stand outside to ensure a favorable satellitereception. The data will be downlinked in order of the student ground base to inform the groundbased radar of the location of the balloon during the chaff release. The data provided will alsobe useful afterwards when doing the chaff cloud data analysis. At this point of the project theproposed component is the NEO-6M GPS Module [14] for Arduino.

Altitude Sensor A digital barometer for Arduino will be used in order to measure the altitudeat which the balloon is navigating . It is crucial that the data of this sensor is downlinked forthe team to know if a release of chaff is possible or not. Moreover if the connection with theballoon is lost, the data of this sensor will be used in the automatic chaff releasing softwareas a variable. This sensor will be placed inside the electronic box for shielding. The chosencomponent for estimations is the BMP085 [15].

Temperature Sensors In order to measure the temperature in the system, thermocoupleswill be used. This data will be downlinked as well for getting knowledge of the temperature atwhich the containers are at when releasing chaff. Therefore there will be a temperature sensorplaced inside the electronic box and one placed outside.The RS PRO 4 wire PT100 Sensor[16] is chosen for this application.

Humidity Sensor In order for the team to get data on the humidity level during the exper-iment, the DHT22 humidity sensor[17] will be used. One will be placed inside the electronicbox and another one outside to gather the data about the humidity during the hole flotationand most importantly the chaff release. This will be helpful for comparing behaviour of thechaff with humidity with previous tests that will be performed during the testing phase.

Limit switches For the team to get feedback if the chaff containers have been releasedsuccessfully limit switches[18] will be used. These will be placed against the containers andwill be deactivated when the container is released.

Solenoids As mentioned earlier in the mechanical design, the chaff containers will be releasedby opening trap doors. These trap doors are held with a pin from a solenoid. Electrical currentretracts the pin turning the coil into a magnet. Each trap door will have a solenoid. The typeof solenoid used will be a framed pull action solenoid. No specific solenoid model has been


- 51 -

chosen yet because the minimal working temperature is either not known or to high for theenvironment. In this environment coating has to be planned for these components.

4.5.4 PCB

The components inside the electronic box will be soldered to a PCB along with the resistors,capacitors and transistors that are needed for the nominal framework of the sensors. Thedimensions and the layout of the PCB are still to be determined.

4.5.5 Data storage and Communication

The communication from the Arduino to the BEXUS uplink and downlink will be done usingan Ethernet Arduino module [19]. Only one module is needed since only one Arduino com-municates data outside the experiment. The data of each Arduino will be stored and analysedafter the flight. Two SD card and an SD card Arduino module [20] will be needed.

4.5.6 Camera

The camera will be placed inside the electronic box with a hole for the lens and will be faceddownwards with an angle to look at the progress of the chaff releasing system by seeing if thecontainers are falling correctly and opening the way they should. The camera information willnot be downlinked, the team will use the data after the recovery for the outreach. The camerawill be powered using LI batteries, a power converter will be needed. The specific camera thatwill be used is not yet determined.


- 52 -

4.6 Thermal Design

• Possible problems. If there is necessity of cooling, heating, insulation

• Temperatures of the different systems, mechanical, electrical.

• Temperature interaction between these system. How the heat will flow from one toanother.

• Simple calculations of temperature gradients and overall temperatures.

• avoid condensation inside the container for chaff

4.6.1 Thermal Environment

The thermal environment of the outside cold air is a concern due to the range of tempera-tures. The large variance in outside air temperature is the most concerning with a rangingfrom between Kiruna’s ground temperature in October to tropopause temperature [21]. Theground temperature in October for Kiruna is between 0°C and −15°C. The lowest temperatureto design for is the tropopause temperature of -80°C. The data from the previous flights haveexperienced air temperatures of −60°C. The second issue caused by the stratospheric environ-ment of the flight is the lack of convection. The low pressure of the atmosphere combinedwith the shielding of the payload’s walls minimizes the convection environment of the payloadexperiment. With the opening from the RM, the operating environment will be subjected tothe low temperature and low pressure air of the outside. The electronics with an optimaltemperature of room temperature might need to be heated before and during launch due tothe cold ground temperatures. In such case, a heater will be added in the EB to maintain aproper temperature.

Figure 14: Atmospheric Pressure and Temperature by Altitude [22]


- 53 -

4.6.2 Overall Design

The structural components will be made of aluminum alloys, specifically aluminum alloys 2014and 2024. These alloys have a large range of operating temperatures, with brittleness notbecoming a factor even at cryogenic temperatures [23]. In Figure 15, Aluminum 2014-T6increases in strength as the metal temperature decreases, while the ductility of the material isconstant. The chart also shows that the strength has a sudden decrease starting at 100°C andis at 57% of room temperature strength at 150°C. The RM and EB structure will be made ofaluminum as well as their cover.

Figure 15: Aluminum 2014-T6 Properties by Temperature [24]

Other materials will form the insulation and chaff capsules. Polyurethane foam will be usedfor the EB to insulate the box and maintain the electronic components at an adequate tem-perature. The chaff capsule should be made of a non-conductive material and that is wherePVC and ABS will be used. Finally, the rope will be made out Dyneema™ fiber. The thermalcharacteristics of the materials used are presented in Table 12.

MaterialConductivity

(W/m°C)Heat

Capacity (J/g°C)Operating

Temperature (°C)

Aluminum(2014-T6 & 2024-T6)

151− 154 0.88 −196 to +150

ABS 0.195 1.42 −85 to + 70PVC 0.158 1.05 −15? to + 80

Polyurethane 0.026 1.4− 1.5 −60 to + 100Dyneema™ 0.2(T )− 20(A) 1.85 below +130

Table 12: Thermal properties of the different materials used. [24, 25, 26, 27, 28, 29, 30, 31, 32]


- 54 -

The minimum temperature of normal PVC is found to be not adequate for the environment.It will become too brittle in the cold temperatures. However, further studies will be car-ried regarding derivatives which might be better withstanding low temperatures, while beingeconomical and non-conductive.

In the case of the electronics, the temperature inside of the box should stay within the operatingtemperature range of all the components. The polyurethane will help insulate some of thecold, but a heater will be needed. Table 13 shows the operating temperatures of the electricalcomponents.

Component Minimal working T°Microcontroller -40°C

GPS module -40°CAltitude sensor -40°C

T°sensor -50°CHumidity sensor -40°C

Limit switch -40°CSolenoid -10°C

Ethernet module -40°CSD module -40°C

Camera -25°C

Table 13: Electrical components, Temperature Requirements.

The most vulnerable component is the solenoid with a minimum temperature requirementof -10°C. Heaters will be strategically placed to provide effective heating of the components,ideally located near the microcontroller, the camera and the solenoids. The heaters will keepthe payload temperature within the working temperatures of all components.

4.6.3 Internal Temperature

4.6.4 Calculations and Simulation Reports

The program to be used to analyze the system for thermal and fluid dynamics is ANSYS™. At alater date when the CFD thermal analysis is completed, it will be determined if the materials arethermally adequate. The thermal simulations will inform how thick the insulation of the payloadwalls and floor should be to achieve a consistent working temperature of the components. Thetemperature profiles of the payload from the simulation will aid in determination of issue ofcondensation and how to minimize it.


- 55 -

4.7 Power System

The gondola provides 28.8 V or 13 Ah battery with a recommended maximum current drawof 1.8A. The experiment must run on external power from 4 hours before launch during thecountdown phase and for the entire flight duration, lasting approximately 4 hours. As a factorof safety the experiment should be able to run for an additional 2 hours. Moreover eachcomponent power consumption is taken when active. A lot of components will be in standbyduring certain periods of the flight. The solenoids are active for a maximum of 2 secondsduring the experiment but power budget has been calculated in the case that some othervariables need to be taken into account. The camera will be the only component power bybatteries provided inside the electronic box.

ID Component Voltage Current No. Power[W] Total[Wh] Min. work T°E1 Microcontroller 5V 45 mA 2 0.225 45 -40°CE2 GPS module 5V 100mA 1 0.5 50 -40°CE3 Altitude sensor 5V 1mA 1 0.005 0.5 -40°CE4 T°sensor 5V 100mA 2 0.5 100 -50°CE5 Humidity sensor 5V 1.5mA 2 0.0075 1.25 -40°CE6 Limit switch 5V 10mA 6 0.05 30 -40°CE7 Solenoid 5V 1.5A 6 7.5 7.5 estimated -10°CE8 Ethernet module 5V 160mA 1 0.8 80 -40°CE9 SD module 5V 15mA 2 0.075 15 -40°C

Total 329.25Gondola available 374

E10 Camera 12V 1A 1 12 1200 -25°C

Table 14: Electrical components, power consumption.

All the components feed by the gondola are powered with a voltage of 5V to use less DC-DCpower converters.


- 56 -

4.8 Software Design

4.8.1 Purpose

The purpose of the code used in the project is to monitor and control the experiment andmaintain communication with the ground station. The software is divided in two parts, as theexperiment itself, one on board and one on the ground. The on board program will collectthe information from the sensors and send the telemetry, and will also send a signal to releasethe containers when it is required. The ground station will receive, process and show thetelemetry in the graphical user interface (GUI), as well as sending the respective commands.The experiment will be able to operate in two different modes, autonomous and manual, whichwill be described in Section 4.8.2.

4.8.2 Design

High Level Design

The design of the on board software that is going to run in the experiment is defined byhow the two Arduino boards are used. One of them, named “Collector”, is connected to allthe on board sensors and is in charge of storing the collected data and send it to the otherArduino board, named “Mind”, which will take care of the business logic which ensures thatthe system work properly, see Figure 16.

Figure 16: High level diagram of the On board software system.

The Collector will store the measurements in a physical data storage, which will be recoverafter the balloon flight. This measurements will be written down each time they arrive to theboard, although the package sent to the Mind will have a predefined periodicity, in order toavoid the saturation of any of the boards. The data sent would be the last received value atthat specific moment.

The Mind will manage all the commands sent by the ground station, releasing the chaff con-tainers according to the flow charts in Figures 18 and 19. It will be connected directly to the


- 57 -

E-Link System, thus it will directly receive the commands and will forward the data sent bythe Collector. Each meaningful step that the Mind will do will be logged in a data storage.

The ground station software will be divided into two main parts: the Communication Nodeand the Processing and Graphics System (PGS). The main purpose of the former is to formatthe commands sent by the PGS in a way that the E-Link System can transport them anddeliver the data from the E-Link System to the PGS. All the communication between the GUIand the experiment on board passes through the Communication Node.

Figure 17: High level diagram of the Ground Station software system.

Once the Communication Node has received a data package from the Mind, it delivers theinformation to the PGS, specifically to the Data Storage Node (DSN). This node will storethe telemetry received in a persistent data storage, such as a DB or a file, for late processing.Then, the package will be forwarded to the Data Processor Node (DPN), which will preparethe data for the GUI. The DSN and the DPN could be modified in the future and even com-bined in a single node, if necessary. Finally, the data will be shown to the operator on thescreen, using the GUI.

If the user decides to execute a command, the GUI will send the order to the Command Node. Itwill prepare the command so the Mind can understand it and forward it to the CommunicationNode, which will format the command and sent it through the E-Link System.

Telemetry and Command Variables

A primary set of telemetry and command variables has been predefined (see Table 15). Thetelemetry will be sent downwards from the experiment to the ground station, meanwhile thecommands will be sent upwards from the ground station to the experiment. The global vari-ables will be predefined for both systems, and, in case of G00 and G01, modified if necessaryby the operator in the ground station, being the new value forwarded to the experiment. Thevalues of the variables G02-G07 will be set by the Mind when each container is released.

The telemetry can be divided into two subgroups, statuses (T0X) and values (T1X), while thecommands can be divided in mode commands (C0X) and release commands (C1X).


- 58 -

ID Variable Type DataType UnitsT00 Experiment Status Telemetry Enumeration [OK, ERROR, PASIVE]T01 Container Status Telemetry Enumeration [OK, ERROR, RELEASED]T02 Communication Status Telemetry Enumeration [OK, ERROR]T03 Temperature 1 Status Telemetry Enumeration [OK, ERROR]T04 Temperature 2 Status Telemetry Enumeration [OK, ERROR]T05 Humidity Status Telemetry Enumeration [OK, ERROR]T06 GPS Status Telemetry Enumeration [OK, ERROR]T07 Altitude Status Telemetry Enumeration [OK, ERROR]T11 Temperature 1 Telemetry Float Degrees CelsiusT12 Temperature 2 Telemetry Float Degrees CelsiusT13 Humidity Telemetry Float PercentageT14 Longitude Telemetry Double Decimal DegreesT15 Latitude Telemetry Double Decimal DegreesT16 Altitude Telemetry Integer MetresG00 Launch Time Global Time Hour of the dayG01 Release Gap Time Global Integer SecondsG02 Container 1 Released Time Global Time Hour of the dayG03 Container 2 Released Time Global Time Hour of the dayG04 Container 3 Released Time Global Time Hour of the dayG05 Container 4 Released Time Global Time Hour of the dayG06 Container 5 Released Time Global Time Hour of the dayG07 Container 6 Released Time Global Time Hour of the dayC00 Stop Command Command - -C01 Resume Command Command - -C02 Set Manual Mode Command - -C03 Set Autonomous Mode Command - -C11 Release Container 1 Command - -C12 Release Container 2 Command - -C13 Release Container 3 Command - -C14 Release Container 4 Command - -C15 Release Container 5 Command - -C16 Release Container 6 Command - -

Table 15: Telemetry and Command Variables considered for the experiment monitorizationand control.

Software System FlowThe system has two modes of operation: manual and autonomous. When the system is inone mode the other can be selected by the operator during the mission. If the Mind losesconnection with the ground station, the system will automatically set the autonomous mode.

For the manual mode, see Figure 18, the idea is to let the operator in the Ground Station todecide when it is time to release a chaff container. The system will make a recognition of thestatus of the experiment and will ask the operator to confirm the release in case there is anypossible risk. In case of having no more chaff containers left, the system will jump to a passive


- 59 -

mode, where it will only collect data.

Figure 18: Flow chart of the manual mode of the release system.

The autonomous mode will operate when the operator decides to let the Mind take controlof the system or when the communication between ground and gondola is lost. In the lattercase, the Mind will try to reconnect while waiting the gap between each release. When thecountdown has come to an end, the system will do several checks in order to ensure that it issafe to release the chaff. When a chaff container is released, the countdown is reset with thevalue of the global variable G01 (see Table 15).

Figure 19: Flow chart of the autonomous mode of the release system.

Graphical User InterfaceThe graphical user interface will display all the RT telemetry, when communication is possible,and will allow the operator to send any possible command to the experiment. A first conceptof how the GUI will possibly be can be seen in figure 20.


- 60 -

All the telemetry related with the status of the system will be displayed on the left-side ofthe screen, while the data acquired from the exteroceptive sensors will be displayed on theright-side. The available commands will be situated in the left-bottom corner. The locationof the experiment will be shown in a map in the center of the display.

Figure 20: First concept of the graphical user interface (GUI) for the Ground Station. Not allthe variables are included.

4.8.3 Implementation

Several software technologies have been chosen to implement the software:

• In the Ground Station:

– Unix environment

– C/C++ programming language

– Qt framework for the Graphical User Interface

• In the Gondola:

– Arduino programming language

• Communication:

– TCP/IP

In order to control, version and store all the programmed code, a git repository will be createdin one of the main online repository platforms, such as GitLab or Bitbucket (TBD). The workprocess with this repository will be similar to what is determined by the Gitflow methodology[33]. The repository will be private during the development of the project but will be madepublic once the project finishes.


- 61 -

4.9 Ground Support Equipment

Aside from the Radar, the ground support equipment will be composed also of a computer orlaptop that will run the GUI where all the telemetry will monitor in real-time, as well as allowthe operator to send commands to the experiment. This computer will be able to:

• Connect with the E-Link System through an Ethernet connection.

• Store all the packages and data that arrives from the experiment.

• Store all the logs generated by the ground station software.

• Run the GUI software and present the information to the user in RT.


- 62 -

5 Experiment Verification and Testing

The success of the experiment will come from the data obtained by tracking the chaff with theradar and by verifying the requirements, which will ensure the proper and correct functioningof the experiment. The aim of this section is to define all possible methods to verify thatthe system can full fill the main objectives at the conditions imposed by the BEXUS´ flight.The verification and compliance of the different requirements will enable to meet the princi-pal objectives of this proposed experiment. In addition, the verification of the requirementswill enable to make a proof of concept of the navigation technology behind this proposedexperiment.

5.1 Verification Matrix

The verification matrix is made following the standard of ECSS-E-10-02A. [34].

The verification methods are defined as follows:

• Test (T). Physical test on the experiment/part/system.

• Inspection (I). Simple inspection of the element.

• Analysis or similarity (A). Analysis corresponds to e.g. computer simulations, similarityis ensured when it is stated that part of the elements of the experiment are similar toparts that have already flown successfully on previous programmes.

• Review-of-design (R). Use of documentation (drawings, schematics) to ensure that ele-ments perform as expected.

ID Written requirement VerificationTestnumber

Status

F.01.The experiment shall measure the wind cur-rents in the stratosphere below the BEXUSballoon during flight.

A - ND

F.02. The experiment shall release chaff probes. A,T,R Test-1 ND

F.03.The experiment shall be able to release dif-ferent types of chaffs.

A,T,R Test-1 ND

F.04.The movement of the chaff cloud shall betracked by radar.

A,T Test-2 ND

F.05.The radar should be able to define the sizeand shape of the chaff cloud.

A - ND

F.06.The chaff shall not interfere with other ex-periments.

T,R Test-2 ND

F.07. The chaff shall not interfere with the gondola. T,R Test-2 ND

F.08.The experiment shall measure the position ofthe gondola.

T,R Test-3 ND

F.09.The experiment shall measure the air pressureof the environment around the gondola.

T,R Test-4 ND


- 63 -

F.10.The experiment shall measure the tempera-ture of the environment around the gondola.

T,R Test-5 ND

F.11.The experiment shall measure the humidityof the environment around the gondola.

T,R Test-6 ND

F.12.The experiment shall execute a system per-formance check of the release system.

T,A Test-7 ND

P.01.The experiment shall measure the wind speedwithin an error of ± TBD m/s.

A - ND

P.02.The experiment shall measure the wind direc-tions within an error of ± TBD.

A - ND

P.03.The experiment shall measure the wind cur-rent vertical position within an error of ±TBD m.

A - ND

P.04.The experiment shall measure the wind cur-rent horizontal position within an error of ±TBD m.

A - ND

P.05.The experiment shall release at least twotypes of chaff.

A,T,R Test-1 ND

P.06.The time between releases shall be higherthan 12 min.

A,T,R Test-1 ND

P.07.The chaff cloud material shall be electromag-netically reflective.

A,T Test-2 ND

P.08.The chaff cloud released by the experimentshall be tracked by radar frequencies between2.5 GHz and 10 GHz.

A - ND

P.09.The chaff cloud position shall be trackedwithin an error in the position of ± TBD m.

A - ND

P.10.The geometry of the chaff cloud shall ensurea minimum vertical speed of TBD and a max-imum of TBD.

A - ND

P.11.The radar shall take measurements of the po-sition of the chaff cloud with a minimum rateof TBD Hz.

A - ND

P.12.The radar should ensure a maximum radialresolution of 1500 m.

A - ND

P.13.The radar should ensure a maximum angleresolution of 1.0 for 100 km.

A - ND

P.14.The chaff cloud shall be released at a safetydistance of at least 18 m below the gondola.

T,R Test-2 ND

P.15.The experiment shall measure the position ofthe gondola within an error of ± 32 m.

T,R Test-3 ND

P.16.The experiment shall obtain position mea-surements of the gondola with a rate higherthan 1 Hz.

T,R Test-3 ND


- 64 -

P.17.The experiment shall measure the air pressurearound the gondola within an error of ± 0.1hPa .

T,R Test-4 ND

P.18.The experiment shall obtain pressure mea-surements of the the environment around thegondola with a rate higher than 1 Hz.

T,R Test-4 ND

P.19.The experiment shall measure the tempera-ture of the environment around the gondolawith an error of ± 1C.

T,R Test-5 ND

P.20.The experiment shall obtain temperaturemeasurements of the environment around thegondola with a rate higher than 1 Hz.

T,R Test-5 ND

P.21.The experiment shall measure the humidityof the the environment around the gondolawith an error of ± 0.5%.

T,R Test-6 ND

P.22.The experiment shall obtain humidity mea-surements of the the environment around thegondola with a rate higher than 1 Hz.

T,R Test-6 ND

P.23.The experiment shall give feedback of eachprocedure step done by the experiment.

T,A Test-7 ND

D.01.The experiment shall be able to operate inthe temperature profile of the BEXUS balloonduring the flight and launch.

T,A Test-8 ND

D.02.The experiment shall be able to operate in thepressure profile of the BEXUS balloon duringthe flight and launch.

T,ATest-9Test-10

ND

D.03.The pressurized parts of the experiment shallsupport 1.5 the working pressure.

T,A Test-9 ND

D.04.The pressurized parts of the experiment shallbe able to operate at environmental pressuredown to 5 hPa.

T,A Test-10 ND

D.05.The experiment shall be able to operate in thevibration profile of the BEXUS vehicle duringthe flight and launch.

T,A Test-11 ND

D.06.The total mass of all payload shall not exceed22kg.

I,A Test-12 ND

D.07.The payload shall fit in a box of dimensions500 mm x 400 mm x 400 mm.

I,R - ND

D.08.The experiment shall withstand a maximumvertical acceleration of 10 G.

T,A Test-13 ND

D.09.The experiment shall withstand a maximumhorizontal acceleration of 5 G.

T,A Test-13 ND

D.10.The on-board communication system shall becompatible with the gondola´s E-link system.

T,R Test-14 ND

D.11.The down-link data rate to the ground stationshall be lower than 205 Kbps .

R - ND


- 65 -

D.12.The ground station shall be compatible withthe BEXUS ground E-net.

R,T Test-14 ND

D.13.The up-link data rate to the ground stationshall be lower than 50 Kbps.

R - ND

D.14.The experiment´s power supply shall be com-patible with the gondola´s provided power.

R,T Test-15 ND

D.15.The experiment DC current draw shall belower than 1.8 A.

R,T Test-15 ND

D.16.The total power consumption of the experi-ment shall be lower than 374.4 Wh.

R,T Test-15 ND

D.17.The experiment shall be mechanically com-patible with the gondola attachments.

R,I - ND

D.18.The experiment shall not disturb or harm anyother experiments.

R,I,A - ND

D.19.The experiment shall not jam other experi-ments´ signals.

T,A Test-2 ND

D.20. The experiment shall not jam the E-link. T,A Test-2 ND

D.21.The density of the chaff cloud before touchingthe ground shall be less than 40 µg

m3 .A - ND

D.22.The geometry of the chaff foils shall not beinhale-able.

I - ND

O.01.The experiment shall be able to automaticallycontinue the performance in case communi-cation with ground station is lost.

T,A Test-14 ND

O.02.The experiment shall be able to au-tonomously disable releases for security rea-sons.

T,A Test-7 ND

O.03.The experiment shall be able to monitor thestatus of the gondola.

T,A Test-7 ND

O.04.The experiment shall be able to rearrange thetiming of the releases.

T,A Test-7 ND

O.05.The experiment should notify to the groundstation the release time with at least 1 minprior to the release.

T,A Test-7 ND

O.06.The ground station shall be able to monitorthe experiment.

T,A Test-14 ND

O.07.The ground station shall be able to controlthe experiment.

T,A Test-14 ND

O.08.The experiment shall store the status of theexperiment (Housekeeping data) during theBEXUS flight.

T,A Test-7 ND

Table 16: Verification Matrix.


- 66 -

5.2 Test Plan

5.2.1 Planned Tests

The planned tests are as follows:

1. Release System Test in Table 17

2. EM Test in Table 18

3. Position Sensor Test in Table 19

4. Pressure Sensor Test in Table 20

5. Temperature Sensor Test in Table 21

6. Humidity Sensor Test in Table 22

7. CPU and Electronics Test in Table 23

8. Temperature Test in Table 24

9. Pressurization 1 Test in Table 25

10. Pressurization 2 Test in Table 26

11. Vibration Test in Table 27

12. Weight Test in Table 28

13. Mechanical Test in Table 29

14. Communication Test in Table 30

15. Electrical Test in Table 31

5.2.2 Test Descriptions

Test Number 1Test Type VerificationTest Facility Kiruna, LTU Space CampusTested Item Release System

Test Level/ Procedureand Duration

Test procedure: Hang the experiment from a distance high enoughto deploy the containers of the release system without touchingthe ground. The elasticity coefficient of the rope will simulate thelow frequency vibrations on the gondola. Simulate the possiblesequences scenarios that can occur during the BEXUS flight.Test duration: 8 hours

Test Campaign Duration 3 WeeksTest Campaign Date AgustTest Status TBT

Table 17: Description Test-1.


- 67 -

Test Number 2Test Type VerificationTest Facility Kiruna, LTU Space CampusTested Item EM


Test procedure: Reproduce the effect of the chaff cloud and trackit with simulated radar and check that the tracked frequenciescoincides with the frequencies simulated.Test duration: 4 hours.



Test Number 3Test Type VerificationTest Facility Kiruna, LTU Space CampusTested Item Position Sensor


Test procedure: Check that the position sensor works in the ex-pected error range. Simulate the location of the experiment onthe gondola and check that the position sensor still works.Test duration: 4 hours.



Test Number 4Test Type Verification & CalibrationTest Facility Kiruna, LTU Space CampusTested Item Pressure Sensor


Test procedure: Test the pressure sensor at different simulatepressures. Calibrate the sensor. Check the results are the oneexpected.Test duration: 2 hours.

Test Campaign Duration 1 WeeksTest Campaign Date July and AgustTest Status TBT



- 68 -

Test Number 5Test Type Verification & CalibrationTest Facility Kiruna, LTU Space CampusTested Item Temperature Sensor


Test procedure: Test the temperature sensor at different simulatetemperatures. Calibrate the sensor. Check the results are the oneexpected.Test duration: 1.5 hours.



Test Number 6Test Type Verification & CalibrationTest Facility Kiruna, LTU Space CampusTested Item Humidity Sensor


Test procedure: Test the humidity sensor at different simulatehumidity environments. Calibrate the sensor. Check the resultsare the one expected.Test duration: 2.5 hours.



Test Number 7Test Type SoftwareTest Facility Kiruna, LTU Space CampusTested Item Payload CPU and Electronics


Test procedure: Simulate by software the sequence of the experi-ment during launch, flotation, land and recovery time at differentpossible simulated BEXUS flight scenarios. The different scenariosare going to be simulated from the BEXUS flights records in [21].Test duration: 6 hours.

Test Campaign Duration 3 daysTest Campaign Date JulyTest Status TBT



- 69 -

Test Number 8Test Type VerificationTest Facility Kiruna, LTU Space CampusTested Item Payload


Test procedure: Place experiment in thermal chamber and take thetemperature down to −80C during a BEXUS flight time (around5 hours base in [21]). During this time the performance of thebatteries, the actuators and the thermal control of the payloadwill be checked.Test duration: 8.0 hours.



Test Number 9Test Type PressureTest Facility Kiruna, LTU Space CampusTested Item Pressurize parts


Test procedure: The pressurized parts use in the experiment will beplaced inside a pressure chamber under 1.5 the ambient pressure.The reaction of the pressurize parts will be recorded.Test duration: 3 hours.



Test Number 10Test Type PressureTest Facility Kiruna, LTU Space CampusTested Item Pressurize parts


Test procedure: The pressurized parts use in the experiment willbe placed inside a vacuum chamber under 5 mbar. The reactionof the pressurize parts will be recorded.Test duration: 3 hours.




- 70 -

Test Number 11Test Type High Frequency VibrationTest Facility Kiruna, LTU Space CampusTested Item Payload


Test procedure: Test the vibration resistance of the experiment bysimulating the vibrations at high frequencies (Frequencies higherthan 10 Hz).Test duration: 4 hours.



Test Number 12Test Type WeightTest Facility Kiruna, LTU Space CampusTested Item PayloadTest Level/ Procedureand Duration

Test procedure: measure the weight of the entire payload.Test duration: 1. hour.

Test Campaign Duration 1 dayTest Campaign Date JulyTest Status TBT


Test Number 13Test Type MechanicalTest Facility Kiruna, LTU Space CampusTested Item Payload


Test procedure: Simulate 10 G load over the vertical axis of thepayload and 5 G over the horizontal axis of the payload. Doa survey of damage of all payload components, specially criticalparts.Test duration: 1. hour.




- 71 -

Test Number 14Test Type CommunicationsTest Facility Kiruna, LTU Space CampusTested Item


Test procedure: Test HMI of the MGC. Inspect the connectionbetween the MGC and the BEXUS ground station. Perform a datatransfer between the MGC and the payload simulating the possibledata rates between the ground station and the experiment. Testduration: 1.0 hour.



Test Number 15Test Type ElectricalTest Facility Kiruna, LTU Space CampusTested Item Payload


Test procedure: Power the payload and test all the electroniccomponents. Measure the different currents in the EB at worstelectrical scenario, with all the electronics component working atthe same time. Measure the power consumption by each of theelectronics components.Test duration: 2 hours.




- 72 -

5.3 Test Results

As testing has yet to be done, no test results exist currently. As the project advances, and allrequirements are assigned verification methods, the testing environments can be set up, andthe experiment components tested.


- 73 -

6 Launch Campaign Preparations


- 74 -

7 Data Analysis and Results

7.1 Data Analysis Plan

The data analysis plan will depend on parameters that are still to be defined. A more de-tailed description will be compiled once the simulations have given needed insight and thecharacteristics of the radar have been taken into account.

Until then a concept of the R2C2 data analysis plan is described under the assumption thatthe following data was collected during the experiment:

1. The position data for each chaff cloud provided by the radar

2. Position data for the BEXUS balloon

3. data from radiosondes that will be used for comparison

7.1.1 Analysis Strategy

In order to get the horizontal wind velocity for all the different altitudes the position data isdifferentiated in time. Vertical winds can be derived from a comparison of the measured verticalmovement of the chaff cloud and its theoretical descend velocity in a windless environment.

A data cleansing will be performed prior to performing the data analysis.The main sources oferrors in the measurements are expected to be the errors of the radar measurements and theerrors originating from the spreading of the chaff cloud.

Depending on the resolution of the measurements and the magnitude of the expected errors,the data will first have to be smoothed to reduce the inherent random errors arising from bothradar tracking and chaff dispersion. This prevents the errors from propagating through thedata analysis where their effects might be magnified.

R2C2’s wind measurements will be compared against expected results derived from theoreticalmodels, but also against other measurements. The BEXUS balloon shall serve as a wind probeduring its ascent and descent. To do this both the experiments own measurements of theballoon’s position as well as the data taken by EBASS will be studied. R2C2 also proposesto have radiosondes starting from ESRANGE or somewhere in the region where the BEXUSballoon passes through shortly before, during or directly after the launch campaign. The winddata these radiosondes measure will be used to compare and validate the measurements takenby chaff tracking.

The expected outcome is proof that chaff tracking can be used for wind measurements inthe stratosphere at altitudes interesting for high-altitude balloon navigation. Wind profiles foreach chaff cloud will be obtained. Moreover, limitations on how long and over what distancesthe wind profiles remain constant could be derived from the gathered data. Insights will begained regarding the effects of the chaff type on the quality of the obtained measurements.


- 75 -

7.2 Launch Campaign

7.2.1 Flight preparation activities during launch campaign

7.2.2 Flight performance

7.2.3 Recovery

7.2.4 Post flight activities

7.3 Results

No results for now. More will come after the launch campaign in an updated version of theSED.

7.3.1 Expected Results


- 76 -

7.4 Lessons Learned


- 77 -

8 Abbreviations and References

8.1 Abbreviations

ABS Acrylonitrile butadiene styreneBEXUS Balloon Experiment for University StudentsDB DatabaseDLR Deutsches Zentrum fur Luft- und RaumfahrtDPN Data Processor NodeDSN Data Storage NodeEB Electronic BoxEBASS Esrange BAlloon Service SystemESA European Space AgencyGPS Global Positioning SystemGUI Graphical User InterfaceI2C Inter-Integrated CircuitLTU Lulea University of TechnologyMATLAB MATrix LABoratoryMB Mega ByteMGC Mission Ground ControlMORABA Mobile Rocket BaseND Not DoneNOAA National Oceanographic and Atmospheric Adminis-

tration (USA)OS Operating SystemPGS Processing and Graphics SystemPVC Polyvinyl chlorideRM Releasing ModuleRT Real-timeSED Student Experiment DocumentationSNSB Swedish National Space BoardSSC Swedish Space CorporationTBC To Be ConfirmedTBD To Be DeterminedZARM Zentrum fur angewandte Raumfahrttechnologie und

Mikrogravitation


- 78 -

8.2 References

[1] About stratospheric balloons. http://http://www.asc-csa.gc.ca/eng/sciences/balloons/about-stratospheric-balloons.asp. Accessed:2018-1-14.

[2] David Hambling. The us military is testing stratospheric balloons that ridethe wind so they never have to come down. MIT Technology Review, 2018.https://www.technologyreview.com/ Accessed: 2019-01-01.

[3] M F. Larsen. Wind measurements: Trimethyl aluminum (TMA) chemical release tech-nique, pages 47–51. 01 2013.

[4] Hans-Ulrich Widdel. Foil chaff clouds as a tool for in-situ measurements of atmosphericmotions in the middle atmosphere: their flight behaviour and implications for radar track-ing. Journal of Atmospheric and Terrestrial Physics, 52(2):89 – 101, 1990.

[5] C A Reddy C Raghava Reddi M Devarajan, P R Parmeswaran. Accuracy of stratosphericwind measurements using chaff releases from rh-200 rockets. Indian Journal of RadioSpace Physics, 13:48 – 55, 1984.

[6] Yoshiko Koizumi et al. Foil chaff ejection systems for rocket-borne measurement of neutralwinds in the mesosphere and lower thermosphere. Review of Scientific Instruments,75(7):2346–2350, 2004.

[7] Naomoto et al. Iwagami. Waves in airglow structures experiment 2004: Overview andpreliminary results. Advances in Space Research, 35:1964–1970, 12 2005.

[8] Yoshiko Koizumi et al. In situ observations of instabilities in the mesopause region usingfoil chaff technique during the waves in airglow structures experiment (wave) campaigns.Journal of Geophysical Research: Atmospheres, 114(D20), 2009.

[9] P. F. Hodnett. The aerodynamics of foil chaff. Proceedings of the Royal Irish Academy.Section A: Mathematical and Physical Sciences, 79:59–71, 1979.

[10] K. S. Gage and T. E. VanZandt. Wind measurement techniques available for the middleatmosphere program. Journal of Geophysical Research: Oceans, 86(C10):9591–9598,1981.

[11] C. Sidi and J. Barat. Observational evidence of an inertial wind structure in the strato-sphere. Journal of Geophysical Research: Atmospheres, 91(D1):1209–1217, 1986.

[12] J. S. Sawyer. Quasi-periodic wind variations with height in the lower stratosphere. Quar-terly Journal of the Royal Meteorological Society, 87(371):24–33.

[13] Factors of safety - fos - are important for engineering design. https://www.engineeringtoolbox.com/factors-safety-fos-d_1624.html. Ac-cessed: 2018-01-09.


http://http://www.asc-csa.gc.ca/eng/sciences/balloons/about-stratospheric-balloons.asp

http://http://www.asc-csa.gc.ca/eng/sciences/balloons/about-stratospheric-balloons.asp

https://www.engineeringtoolbox.com/factors-safety-fos-d_1624.html

https://www.engineeringtoolbox.com/factors-safety-fos-d_1624.html

- 79 -

[14] U-Blox. Gps sensor datasheet. https://www.u-blox.com/sites/default/files/products/documents/NEO-6_DataSheet_%28GPS.G6-HW-09005%29.pdf. Accessed: 2019-01-13.

[15] Adafruit. Altitude sensor datasheet. https://cdn-shop.adafruit.com/datasheets/BST-BMP085-DS000-06.pdf. Accessed: 2019-01-13.

[16] RS. Thermocouple datasheet. https://docs-emea.rs-online.com/webdocs/15bb/0900766b815bb2cc.pdf. Accessed: 2019-01-13.

[17] Sparkfun. Humidity sensor datasheet. https://www.sparkfun.com/datasheets/Sensors/Temperature/DHT22.pdf. Accessed: 2019-01-13.

[18] Digikey. Limit switch datasheet. https://www.digikey.com/product-detail/en/panasonic-electronic-components/ESE-22MH24/P13584STR-ND/1245477. Accessed: 2019-01-13.

[19] Microchip. Ethernet module datasheet. http://ww1.microchip.com/downloads/en/devicedoc/39662c.pdf. Accessed: 2019-01-13.

[20] Adafruit. Sd module datasheet. https://cdn-learn.adafruit.com/downloads/pdf/adafruit-micro-sd-breakout-board-card-tutorial.pdf. Accessed: 2019-01-13.

[21] EuroLaunch. BEXUS User Manual. Version 7.2. 31 Nov 2017.

[22] Daniel J. Jacob. Chapter 2. atmospheric pressure. http://acmg.seas.harvard.edu/people/faculty/djj/book/bookchap2.html. Accessed: 2019-01-12.

[23] Frank Armao. Aluminum workshop: Charpy v-notch testing—why not aluminum?https://www.thefabricator.com/article/aluminumwelding/aluminum-workshop-charpy-v-notch-testing-why-not-aluminum-.Accessed: 2019-01-12.

[24] MatWeb Material Property Data. Aluminum 2014-t6; 2014-t651.http://www.matweb.com/search/DataSheet.aspx?MatGUID=e5de9f1161d34f71a34ae016723d097f. Accessed: 2019-01-12.

[25] The Engineering ToolBox. Thermoplastics - physical prop-erties. https://www.engineeringtoolbox.com/physical-properties-thermoplastics-d_808.html. Accessed: 2019-01-12.

[26] The Engineering ToolBox. Polyurethane insulation. https://www.engineeringtoolbox.com/polyurethane-insulation-k-values-d_1174.html. Accessed: 2019-01-12.

[27] The Engineering ToolBox. Insulation materials - temperature ranges. https://www.engineeringtoolbox.com/insulation-temperatures-d_922.html.Accessed: 2019-01-12.


https://www.u-blox.com/sites/default/files/products/documents/NEO-6_DataSheet_%28GPS.G6-HW-09005%29.pdf



https://cdn-shop.adafruit.com/datasheets/BST-BMP085-DS000-06.pdf

https://cdn-shop.adafruit.com/datasheets/BST-BMP085-DS000-06.pdf

https://docs-emea.rs-online.com/webdocs/15bb/0900766b815bb2cc.pdf

https://docs-emea.rs-online.com/webdocs/15bb/0900766b815bb2cc.pdf

https://www.sparkfun.com/datasheets/Sensors/Temperature/DHT22.pdf

https://www.sparkfun.com/datasheets/Sensors/Temperature/DHT22.pdf

https://www.digikey.com/product-detail/en/panasonic-electronic-components/ESE-22MH24/P13584STR-ND/1245477



http://ww1.microchip.com/downloads/en/devicedoc/39662c.pdf

http://ww1.microchip.com/downloads/en/devicedoc/39662c.pdf

https://cdn-learn.adafruit.com/downloads/pdf/adafruit-micro-sd-breakout-board-card-tutorial.pdf



http://acmg.seas.harvard.edu/people/faculty/djj/book/bookchap2.html

http://acmg.seas.harvard.edu/people/faculty/djj/book/bookchap2.html

https://www.thefabricator.com/article/aluminumwelding/aluminum-workshop-charpy-v-notch-testing-why-not-aluminum-

https://www.thefabricator.com/article/aluminumwelding/aluminum-workshop-charpy-v-notch-testing-why-not-aluminum-

http://www.matweb.com/search/DataSheet.aspx?MatGUID=e5de9f1161d34f71a34ae016723d097f

http://www.matweb.com/search/DataSheet.aspx?MatGUID=e5de9f1161d34f71a34ae016723d097f

https://www.engineeringtoolbox.com/physical-properties-thermoplastics-d_808.html

https://www.engineeringtoolbox.com/physical-properties-thermoplastics-d_808.html

https://www.engineeringtoolbox.com/polyurethane-insulation-k-values-d_1174.html



https://www.engineeringtoolbox.com/insulation-temperatures-d_922.html

https://www.engineeringtoolbox.com/insulation-temperatures-d_922.html

- 80 -

[28] STUG. Thermal resistance. http://www.stug.com.au/materials/engineering-plastics-properties/min-max-operating-temperatures.php. Accessed: 2019-01-12.

[29] Ensinger. Plastics with low temperature properties. https://www.ensingerplastics.com/en/shapes/plastic-material-selection/low-temperature. Accessed: 2019-01-12.

[30] DSM. Fact sheet: Ultra high molecular weight polyethylene fiber from dsm dyneema.https://issuu.com/eurofibers/docs/name8f0d44. Accessed: 2019-01-12.

[31] ASM Aerospace Specification Metals Inc. Aluminum 2014-t6; 2014-t651. http://asm.matweb.com/search/SpecificMaterial.asp?bassnum=MA2014T6. Ac-cessed: 2019-01-12.

[32] ASM Aerospace Specification Metals Inc. Aluminum 2024-t6. http://asm.matweb.com/search/SpecificMaterial.asp?bassnum=ma2024t6. Accessed: 2019-01-12.

[33] Vincent Driessen. A successful git branching model. https://nvie.com/posts/a-successful-git-branching-model/. Accessed: 2019-01-13.

[34] ECSS Secretariat. Space Engineering: Verification. ESA-ESTEC, Requirements Stan-dards Division, ESTEC, P.O. Box 299, 2200 AG Noordwijk, The Netherlands, Nov 1998.

[35] Eugene F Knott, DJ Lewinski, and SD Hunt. Chaff theoretical/analytical characteriza-tion and validation program. Technical report, GEORGIA INST OF TECH ATLANTAENGINEERING EXPERIMENT STATION, 1981.

[36] James Brunk, Dennis Mihora, and Peter Jaffe. Chaff aerodynamics. Technical report,ALPHA RESEARCH INC SANTA BARBARA CA, 1975.

[37] University of Wyoming Department of Atmospheric Science. Atmospheric soundings.http://weather.uwyo.edu/upperair/sounding.html. Accessed: 2019-01-13.

[38] National Oceanic and Atmospheric Administration of the USA:. Will be completed afterthe u.s. government shutdown ends. https://ruc.noaa.gov/raobs/. Accessed:2018-12-16.


http://www.stug.com.au/materials/engineering-plastics-properties/min-max-operating-temperatures.php



https://www.ensingerplastics.com/en/shapes/plastic-material-selection/low-temperature



https://issuu.com/eurofibers/docs/name8f0d44

http://asm.matweb.com/search/SpecificMaterial.asp?bassnum=MA2014T6

http://asm.matweb.com/search/SpecificMaterial.asp?bassnum=MA2014T6

http://asm.matweb.com/search/SpecificMaterial.asp?bassnum=ma2024t6

http://asm.matweb.com/search/SpecificMaterial.asp?bassnum=ma2024t6

https://nvie.com/posts/a-successful-git-branching-model/

https://nvie.com/posts/a-successful-git-branching-model/

http://weather.uwyo.edu/upperair/sounding.html

https://ruc.noaa.gov/raobs/

- 81 -

Appendix A Experiment Reviews


- 82 -

Appendix B Outreach


- 83 -

Appendix C Additional Technical Information

Figure 21: Characteristics of the Dyneema rope depending on its size


- 84 -

Figure 22: Estimation of the price budget of the project


- 85 -

Appendix D Checklists


- 86 -

Appendix E Simulations

The simulations try to predict in a simplified way how the chaff will fall once it is released fromthe gondola. The final output will be the horizontal and vertical displacements, as well as thevelocity in the three components. The software can be extended to include the radar specificsand predict the signal response received from the chaff cloud. The concept of the simulation isbased on the papers of E. F. Knott, D. J. Lewimki and S. D. Hunt from the Georgia Instituteof Technology [35] and J. Brunk, D. Mihora and P. Jaffe from the Alpha Reserach Institute ofSanta Barbara [36].

E.1 Model of chaff dipole motion

A chaff piece is defined as a dipole 23. The characteristic motion of the falling dipole isindicated in Fig. 23. It is a spiral with spiral rate Ω and spiral radius a. The geometry of afoil type chaff piece is a stripe with width c, length l and negligible thickness d.

Figure 23: Characteristic helical chaff dipole spiral motion. Source: Brunk et al. [36]

The basic equation governing the motion of a single dipole is given by Newton’s 2nd law.

mdv

dt= FD + FG (1)

Here FD is the drag force and FG is the weight. The drag force depends on the exactproperties of the dipole’s properties and its motion, which makes Eq. (1) very complex. Theassumptions used to simplify and solve this problem are listed below.


- 87 -

• The dipoles tend to maintain their pitch angle, γ. This is based on the findings of Brunket al. [36].

• The angle of attack αT also remains constant.

• This means the initial angle θ = γ − αT also remains constant.

• The spiral rate Ω and the spiral radius a are constant and taken from statistical Gaussiandistributions with a determined mean value and standard deviation.

• Turbulent effects are ignored. For that purpose, the time interval chosen should be smallenough so that changes in the wind velocity due to turbulent effects are negligible. Thistime interval ∆t should be less than 10 ms.

Figure 24: Definition of angles around a chaff dipole. Source: Brunk et al. [36]

In this model the horizontal displacement of the chaff is given by the sum of the spiral motionand the motion induced by the wind currents. Expressing the drag force and the weight, Eq.(1) becomes

mdv

dt=

1

2ρApCD (u− v) (u− v)−mg (2)

where

m is the mass of the dipole,

v is the dipole velocity vector,

ρ is the atmospheric density,

Ap ≈ c · l sin(αT ) is the dipole’s projected area onto the plane normal to v.

CD is the drag coefficient,

u is the wind velocity vector.

g = gk is the gravitational acceleration.

Eq. (2) can be split into the three Cartesian coordinates. In the system used each vector isgiven as r = xi + yj + zk, where k is the vertical direction and i and j span the horizontal


- 88 -

plane. The equations for the three separate components are

dvxdt

= ε (ux − vx)2 (3)

dvydt

= ε (uy − vy)2 (4)

dvzdt

= ε (uz − vz)2 − g (5)

where

ε = ±ρApCD2m

(6)

The ± comes from the necessity to preserved the vector sense of the velocity difference (u−v).Eq.(3) and (4) are essentially the same. They can be solved analytically by integrating withrespect to the velocity (from v0 to v(t)) and the time (from t0 to t0 + ∆t) obtaining thefollowing expression, valid for vx and vy.

v(t) = u− u− v0

1 + ε(u− v0)∆t(7)

The displacement of the particle, P (t) due to the wind motion can be calculated integrating theprevious equation. The horizontal positions are then given by the sum of the initial positionsx0 and y0, the displacement caused by winds and the displacement due to the helical motionof the dipole:

x(t) = x0 + Px(t) + a cos(Ωt+ Ω0) (8)

y(t) = y0 + Py(t) + a sin(Ωt+ Ω0) (9)

This means the horizontal positions can be expressed as

x(t) = x0 + a cos(Ωt+ Ω0) + u′xt+1

εln[1 + t(u′x − v0x)] (10)

y(t) = y0 + a sin(Ωt+ Ω0) + u′y∆t+1

εln[1 + εt(u′y − v0y)] (11)

The vertical component has a more difficult solution and needs a case distinction based onthe value of ε.

If ε < 0, meaning that uz < vz

vz(t) = u′z − ζ tan

[tan−1

(u′z − v0z

ζ

)− ζε∆t

](12)

where

ζ =

√g

ε(13)


- 89 -

If ε > 0, meaning that uz > vz

vz(t) = u′z − ζu′z − v0z + ζ tanh(ζε∆t)

ζ + (u′z − v0z) tanh(ζε∆t)(14)

Both equations can be integrated to find the vertical position of the dipole.

If ε < 0,

z(t) = z0 + u′z∆t−1

ε

[cos(ζε∆t) +

u′z − v0z

ζsin(ζε∆t)

](15)

If ε > 0,

z(t) = z0 + (u′z + ζ)∆t− 1

εln

1

2ζ

[(uz + ζ − v0z)e

2ζε∆t − (uz − ζ − v0z)]

(16)

From the equations proposed, the velocity and position of the chaff for arbitrary wind charac-teristics can be found. Still one of the parameters needs to be estimated accordingly, the dragcoefficient. The drag coefficient is defined as,

CD = CN cos(αT ) + CA sin(αT ) (17)

where CN is the normal coefficient and CA the axial coefficient. Both coefficients were in allprevious simulations obtained as tabulated values depending on the Reynold’s number.

Re =ρvc

µ(18)

However Despite extensive research these or similar tables could not be found. If the searchremains unsuccesful the initial coefficients for the R2C2 simulation might have to be createdin a preceding Monte Carlo simulation.

The angle of attack is generated randomly and the first approximation of the drag coefficient iscalculated. The angle of attack needs to be correlated with the following formula to estimateits real value.

αT = sin−1

(2mgv2

z

ρApCD

)1/3

− θ (19)

with vz given as,

vz =

(2mg sin γ

ρApCD

)1/2

sin γ (20)

E.2 Model of stratospheric environment

To be able to define the stratosphere environment in our simulations, and have reasonablevalues for the winds u, different radiosonde data sets were analyzed. To fit the conditionsduring the launch campaign, the data analyzed is from October measurements performed inthe years 2014 to 2018 from three weather stations at similar latitudes and longitudes closeto ESRANGE.


- 90 -

The data for measurements performed at Andøya (Norway) and Kandalaksa (Russia) weretaken from a collection provided by the the University of Wyoming [37]. The data for measure-ments performed from Sodankyla (Finland) were obtained over the database of the NationalOceanic and Atmospheric Administration (NOAA) of the USA [38]. Some of the analyzeddata is shown in Fig. 25.

To find parameters for the model of the stratospheric environment of the chaff cloud, onlythe data from altitudes higher than 20 km is considered. In the data from 2018 (Fig. 25a,25b) there is a clear trend of eastward winds, just like expected from the flight trajectories ofprevious BEXUS balloons. Parameters derived from the radiosonde data for the simulation arecollected in Table 33.


- 91 -

Table 33: Yearly averages for the different stations

Year Value [Unit] Andøya Kandalaksa Sodankyla2018 vN [m/s] 4.99± 5.79 7.29± 7.15 -

vE [m/s] 17.13± 5.79 15.33± 6.66 -minvN [m/s] −46.36± 11.06 −17.94± 2.71 -maxvN [m/s] 23.20± 5.54 35.03± 11.14 -minvE [m/s] −9.63± 2.79 −15.19± 5.47 -maxvE [m/s] 56.99± 9.64 43.78± 13.36 -max∆vN [m/s] 10.06± 9.42 3.79± 3.80 -max∆vE [m/s] 19.36± 8.51 3.35± 3.32 -

2017 vN [m/s] 6.04± 7.06 7.11± 4.80 5.34± 5.32vE [m/s] 12.72± 6.99 11.16± 7.58 8.18± 5.81minvN [m/s] −23.26± 4.49 −25.24± 6.17 −22.52± 3.99maxvN [m/s] 24.49± 8.28 28.28± 10.66 27.10± 10.76minvE [m/s] −25.32± 4.07 −26.33± 14.53 −21.77± 10.28maxvE [m/s] 32.25± 9.36 30.60± 11.06 35.59± 20.38max∆vN [m/s] 8.75± 7.42 3.38± 3.59 8.542± 6.72max∆vE [m/s] 8.67± 7.28 3.33± 3.23 8.29± 7.04



2014 vN [m/s] - 3.26± 5.02 3.64± 5.49vE [m/s] - 17.18± 8.59 16.86± 7.68minvN [m/s] - −16.18± 6.65 −21.50± 5.07maxvN [m/s] - 42.57± 3.17 34.93± 7.11minvE [m/s] - −16.81± 2.97 −11.93± 4.74maxvE [m/s] - 38.87± 12.93 37.46± 9.85max∆vN [m/s] - 3.05± 4.31 -max∆vE [m/s] - 3.24± 3.10 -


- 92 -

(a) Andoya 2018

(b) Kandalaksa 2018

(c) Sodankyla 2016

Figure 25: Data from different radiosonde soundings. The dashed black lines mark the zerowith no winds and the average of the winds at altitudes higher than 20 km. For better visibilityonly data from the radiosondes that reached the highest altitudes is displayed.


Documents

Student Experiment Documentation · integration progress review, and nal experiment report. The R2C2 Team consists of a diverse and inter-disciplinary group of students from Lule