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Development Status of EXPERT, the European eXPErimental Re-entry Testbed

Federico Massobrio Alenia Spazio SpA, Strada Antica di Collegno 253, 10146 Torino, Italy

Marco Caporicci European Space Agency (ESA/ESTEC), Keplerlaan 1, P.O. Box 299 –2200 AG Noordwijk ZH, The Netherlands

and

Michelangelo Serpico Centro Italiano Ricerche Aerospaziali (CIRA), v. Maiorise, 81043 Capua CE, Italy

EXPERT is a milestone step for the acquisition in Europe of base re-entry technologies and capabilities in recognition of the importance of an independent European access to space and in preparation for the future needs of transportation and exploration missions. The objective of EXPERT is to provide a test-bed for the validation of aerothermodynamics models, codes and ground test facilities in a representative flight environment to improve the understanding of issues related to analysis, testing and extrapolation to flight. The vehicle, a symmetrical re-entry capsule 1.6 m high and 1.3 m diameter for about 350 kg will be launched on a sub-orbital trajectory 120 km high at a Mach 5 re-entry velocity using a VOLNA launcher. Following the completion of the Phase B, the development phase is expected to be undertaken by mid 2005 under ESA contract, Alenia Spazio leading the industrial team and CIRA coordinating the scientific payload.

List of Acronyms Aero/TD Aero-Thermodynamics ARD Atmospheric Re-entry Demonstrator CFD Computational Fuido-Dynamics CIRA Centro Italiano Ricerche Aerospaziali CMC Ceramic Matrix Composite COTS Commercial Off-the-Shelves CSCI Computer Software Configuration Items DHU Data Handling Unit DKR Detra-Kemp-Riddell ESA European Space Agency EXPERT European eXPErimental Re-entry Testbed FCW Fully Catalytic Wall FEI Flexible External Insulation FESART FEasibility Study of A Re-entry Testbed FTM Flight Test Measurements GPS Global Positioning System

GSE Ground Support Equipment NCW Non- Catalytic Wall NE Non-Equilibrium NS Navier-Stokes OBDH On-Board Data Handling OML Outer Mold Line P.I. Principal Investigators P/L Payload PCW Partially Catalytic Wall PDR Preliminary Design Review PG Perfect Gas SW Software SWBLI Shock-Wave Boundary-Layer Interaction TCS Thermal Control System TPS Thermal Protection System TU Technology University

I. Introduction ince the early nineties ESA has worked to gain actual flight experience of the atmospheric re-entry phenomena, as required for the correct design of human transportation vehicles, reusable space transportation systems,

planetary exploration and sample return missions. S

AIAA/CIRA 13th International Space Planes and Hypersonics Systems and Technologies AIAA 2005-3446

Copyright © 2005 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

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In 1998 the Atmospheric Re-entry Demonstrator (ARD) was successfully flown. It performed a controlled sub-orbital flight, from spacecraft separation through atmospheric re-entry to splashdown. It carried material samples and instrumentation, so that actual flight parameters could be compared with those predicted mathematically. Other capsules have been flown as the result of national projects (Express, Mirka, etc.) with various levels of success. All these systems were characterized by relatively simple or even well-experimented shapes. Moreover the thermal protection consisted mainly or exclusively of ablative materials.

For the correct design of future space vehicles more precise data are desirable for a number of aerothermodynamic phenomena such as:

- flap efficiency and heating; - shock wave / boundary layer interactions: - boundary layer transition from laminar to turbulent; - high temperature and gas chemistry effects; - gas-surface interaction effects (catalysis, oxidation). Past developments undertaken in Europe for Hermes, the crew

transportation capsules and the X-38 lifting body vehicle have shown that there is a need of actual hypersonic and atmospheric re-entry flight data for proper benchmarking of the aerothermodynamic predictions and design tools. These consist of computational fluid dynamic analyses and wind tunnel experimentation, as well as verified ground-to-flight extrapolation methodologies.

The EXPERT vehicle has been conceived precisely to address these shortcomings by obtaining an aerothermodynamic flight database, allowing addressing the specific phenomena and validating the tools. The vehicle shape is designed so that the various aerothermodynamic phenomena may be addressed and dedicated measurements may be performed. The primary objective of EXPERT is to provide a test-bed for the validation of aerothermodynamics models, codes and ground test facilities in a representative flight environment, to improve the understanding of issues related to analysis, testing and extrapolation to flight.

One major consequence is the requirement to adopt non-ablative thermal protections to avoid contamination of the flow boundary layer by chemical species and solid particles. This leads to the choice of thermal protection materials, which are not expected to undergo degradation during the flight and therefore would be candidate for reusable thermal protection applications (although no actual data on extended reusability will be obtained from one single flight). Also special care has to be placed on the location and number of measurement sensors, the recording of the free stream parameters during re-entry using an appropriate Air Data System and in the safe storage and telemetry downloading of the performed measurements. Innovative and promising measurement techniques candidate for utilization in-flight are being assessed, as they may enhance the quality of the obtained flight database.

The initial vehicle concept was the subject of a feasibility study in the frame of the Agency General Studies Program in 2001. Various candidate shapes were analyzed and traded-off. Also an initial assessment of the vehicle mission, layout and subsystems was performed, which gave confidence about its feasibility. The retained solution consists of a low-cost re-entry capsule with conical shape and blunt nose, launched by the low-cost Russian submarine-based Volna sub-orbital launcher

Figure 1. The EXPERT vehicle.

Figure 2. The VOLNA launcher.

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(which employs the R-29R missile). EXPERT is designed for sub-orbital flights with a re-entry velocity range, which may vary from 5 to 7 km/s. The foreseen landing site is the Russian military base in the Kamchatka peninsula. At least three recurring flights (with dedicated flight units) are envisaged for different re-entry conditions, starting from 2007, and a promising market of potential experiments is arising.

The actual development of EXPERT was proposed and approved by the ESA Member States at the occasion of the November 2001 Ministerial Council in Edinburgh. By 2003, the confirmed subscriptions by the Member States reached a level sufficient to undertake the actual development of the project (first flight unit). A Phase B industrial contract has been placed to advance the EXPERT system to PDR maturity including the definition of the experiment interface and to produce the technical and programmatic data package for Phase C/D, operations and post flight analyses. Presently the Industrial Team has successfully completed the PDR of the Phase B study.

II. System Architecture

A. General Configuration The EXPERT capsule shape is composed of simple geometrical elements: an ellipsoidal blunt nose, a conical

body, a clothoid ellipse-cone junction and four flat sides with four fixed flaps (two open ones and two closed ones). The structural concept is designed to sustain the four main load conditions, that are launch, aerodynamic drag (i.e. dynamic pressure + heating), parachute opening and ground impact.

For the thermal protection system, four main areas are identified: a C/SiC nose cap, metallic TPS on the conical sides, F-lexible External Insulation (FEI) on the rear face and ceramic flaps. The TPS surface is high densely instrumented to allow for flow conditions reconstruction after flight, as part of the several experiments.

The nose, the external shield and the four ramps will carry the aerodynamic drag. The external lateral thermal shield will consist of four curved corner panels and four triangular panels. The junction between corner panels and triangular panels, as well as the junctions to the

internal structure and to the ceramic nose, will allow relative displacements to accommodate the thermal gradients as well as sustain controlled natural depressurization / re-pressurization during the flight.

The capsule at launch is suspended upside-down to the third stage of Volna via an interface adapter. The parachute bay is located in the central cylindrical area. For the best efficiency of the structural load path the

shear panels will be bolted to the cylindrical wall of the parachute bay, therefore a structural wall will surround the parachute assembly.

The EXPERT capsule will impact the ground in nose-down configuration. It is therefore likely a damage of the nose surface such that its re-use will be inhibited. The internal structure is designed to preserve its integrity allowing the recovery of the stored data and as much as possible of the avionic equipment for post-flight inspection.

The avionics architecture is simplified up to maximum extent, making large use of Commercial Off-The-Shelves (COTS) equipment.

B. Aerothermodynamics and Aerodynamics The system activities on aerothermodynamics and

aerodynamics, as started from the previous FESART study and EXPERT preparatory activities, have the objective to optimize the vehicle shape with respect to the mission requirements and to confirm and / or revise the available aerothermodynamic data bases.

Preliminary Aero/TD databases generation and shape optimization has been performed by means of CFD tools sharing the

Figure 3. EXPERT main components.

Figure 4. Shape optimization.

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activities between the Aerodynamics Group of the Aerospace Engineering Department of TU Delft (The Netherlands), the Aerothermodynamics and Propulsion Department of CIRA Research Center (Italy), SENER (Spain) and ESTEC. Shape optimization and aerothermodynamic analyses had also the objective to confirm and possibly optimize the location of the scientific payload sensors while Aero/TD database generation had also the objective to generate necessary additional data to cover those unavailable from previous Phase A activity. A major set of the aero-thermodynamics output has been needed for the definition of the structural and thermal loads as input to the mechanical hardware and thermal protection item design activities while the aerodynamic data set has been

necessary for trajectory and mission consolidation and flight mechanics performance evaluation.

The aero-thermodynamic activities had the objectives to analyse the performance and the behaviour of the EXPERT in all flight regimes from hypersonic down through supersonic, transonic and subsonic by using CFD tools and engineering techniques. Outputs included forces, moments and aerodynamic derivatives, heat fluxes, pressure and local effects due to flow transition and wall catalycity efficiency.

The results of the computational work have been used for the definition of Phase C/D wind tunnel tests planning and campaigns (forces / moment and heat flux measurements in hypersonic and plasma facility as well dynamic stability parameters definition in transonic regime) aimed to the finalization of the Aero/TD databases. Furthermore, both CFD work results and wind tunnel tests data will be the reference data for the definition of the cost and planning for the post-flight activities after the 1st EXPERT flight.

EXPERT reference trajectories show external heat flux and thermo-mechanical loads which are severe with respect to thermal protection material characteristics and performance. Priority has been given to reference mission 1 (5 Km/s) and mission 2 (6 Km/s). The major output of the aerothermodynamic work package, the heat fluxes in real gas conditions (with thermochemistry and catalysis effects) and their time variation, has basically led to the confirmation that the selected TPS architecture and material are suitable for the survivability of the vehicle and meet the mission and measurements requirements, provided that the mission trajectory is suitably selected in accordance to the achieved vehicle mass to accommodate on-board the requested set of payloads. Presently the baseline mission is conservatively the 5 km/s with an overall vehicle outfitted mass up to almost 400 kg.

Furthermore, as EXPERT has to demonstrate a high level of accuracy associated with both the re-entry operation and in flight test measurements, the vehicle system must rely upon an aerothermodynamic database covering all the heating aspects and phenomena (surface material catalysis effects, boundary layer transition from laminar to turbulent, etc.) both for the complete vehicle and locally for the critical element (flap and its cavity and gaps, experiment sensors).

All the computations presented hereinafter refer to the EXPERT_4.4B geometry. Such a geometry is characterized by the main properties reported in fig. 5.

The reference trajectories are shown in fig. 6. A number of NS-NE Laminar 2D-axisymmetric computations have been foreseen in order to estimate the nose

heating along the trajectory. The computations have been performed for two points of such trajectory: o Point with maximum heat flux (P1:M=16.28 h=37.18 Km)

Table 1. CFD workplan.

Figure 5. . EXPERT_4.4B geometry.

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o Point with high heat flux and low pressure (P2:M=18.20 h=53.7 Km), potentially critical for passive/active oxidation

The reference computations are performed with the most reliable models, that are Park model for chemistry and Yun-Mason transport model. Both non catalytic and fully catalytic assumptions are made. The effects of the chemistry and transport models have been then estimated using respectively Dunn-Kang and a fit-based model. Adiabatic wall with radiative equilibrium (e=0.85) condition have been used for all the computations.

The values of wall heat fluxes and temperature at the stagnation point have been compared with the prediction of

the DKR simplified relation; for the catalytic wall assumption a good agreement has been achieved whereas for the NC wall conditions a scaling coefficient of 0.72 has been determined.

A rough estimation of the transition can be performed with the Space Shuttle criterion based on the local values

of Mach and Reynolds number (considering the momentum thickness as the reference length) along the wall.

330340M [Kg]

-5.2-7.4γ [deg]

65Ve [Km/sec]

Mission 2Mission 1

Figure 6. Reference trajectories.

X (m)H

eatF

lux

(W/m

2)

Y(m

)

0 0.5 1 1.50

500000

1E+06

1.5E+06

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FCWPCWNCWqDKR0.804 * qDKR0.72 * qDKRGeometry

Ve=6Km/sec g=5.2°M=330 Kg

Point P1 - M=16.28

Figure 7. Heat fluxes and catalysis effect.

x (m)

Ret

heta

/Me

0 0.5 1 1.50

100

200

300

400

M=10.36M=12.41M=15.68M=16.28M=16.80M=17.18

MISSION 2

Figure 8. Transition estimation for mission 2.

Figure 9. Pressure Coefficient distribution at �T=1°, �T=5° and �=45° at Mach=3.

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The flow should be fully laminar when the ratio Reθ/Me is lower than 100 and fully turbulent when this ratio is higher than 200, but nothing can be said in the middle, where the boundary layer could be transitional.

This criterion has been determined through an experimental campaign for the Space Shuttle. In order to estimate what is the maximum value of the tolerable surface roughness to avoid transition, the Reda

criterion, derived from the Space Shuttle re-entry conditions, has been applied. The Reda correlation related the disturbance parameter δ

κχ = , where k is the height of the roughness element and δ the boundary layer thickness, to the transition

parameter Meθψ Re= with a certain constant C (=30 for the

Space Shuttle), i.e.: ��

���

�=δκθ C

MeRe

then it is possible to

estimate CMeδκ θRe=

This correlation has been applied to the computed CFD results for the mission 1 and mission 2.

The aerodynamic coefficients have been estimated for the

new shape of the capsule. CFD simulations at α=0 have been performed on a quarter of the capsule due to the double-symmetry of the flowfield with respect to the plane y=0 and z=0; computational grid for the cases at angle of attack equal to 1 and 5 (symmetry only with respect to the plane y=0) has been obtained doubling grid #1 respect to the plane z=0.

Each simulation has been performed on three different grid levels in order to reach a fully converged solutions.

C. TPS and hot structures The Thermal Protection System (TPS), in tight synergy with the Thermal Control System (TCS), has the

function of ensuring to EXPERT the adequate thermo-mechanical environment during the complete mission: o withstand the severe thermal heating

experienced during the ballistic re-entry without any degradation of the materials characteristics and unacceptable erosion from the externally located payload sensors point of view;

o provide a continuous outer mould line (OML) without any bowing that could potentially induce transition from laminar to turbulent;

o maintain the internal structure within its allowable limits;

o prevent hot air sneak flows during the re-entry phase;

o provide all cut-out areas and supporting structure for payload sensors fixation.

In order to cope with the extremely high thermal heating, the TPS architecture is mainly based on the hot structure approach according to the following solutions:

o a C-SiC nose cap in correspondence of the hottest sections of EXPERT. The Ceramic Matrix Composite (CMC) nose is expected to withstand the peak temperature that occurs in correspondence of the stagnation. The design approach followed for the EXPERT nose is mainly based on the X-38 solution that couples external ceramic parts to internal flexible insulation located just beneath in order to maintain the cold structure (namely the colander, used for sensors mounting) always at a temperature compatible with the sensors characteristics and with the heat flux allowed to enter the internal environment;

Figure 10. Computational grid for αααα=0

Figure 11. TPS architecture

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o flat and rounded lateral surfaces of EXPERT are made of a metallic hot structure TPS concept. The external metallic surface in PM1000 is directly exposed to re-entry aerothermal heat fluxes. The length of the metallic surfaces was tuned in order not to exceed the allowed heat flux limit (225 Kw/m2). In addition to the high temperature resistance capability, PM1000 panels also provide the needed mechanical stiffness to counteract the dynamic pressure during re-entry as well as the fast depressurization load at VOLNA second stage separation. Similarly to the nose hot structure, high temperature insulations are attached below the metallic TPS to limit the heat flux entering the internal environment;

o the hot structure configuration has at the same time to be connected to the internal cold structure avoiding as mach as possible to transmit conductively the heat load. This is achieved by means of proper brackets sizing also capable to ensure the required mechanical performances.

D. Cold structure The cold structure is the primary structural support for

payloads, service equipment, parachute system and TPS. The cold structure is basically made of Al sandwich

panels assembled in a symmetric tower shape. The axis of symmetry is coincident with the launch direction. The configuration is shared-out in radial panels, that confers axial and shear stiffness, and transversal panels providing bending stiffness. The sandwich technology was preferred for reasons of simplicity and effectiveness in terms of ratio stiffness / weight.

In the internal zone of the cold structure a central bay was carried-out to accommodate the canister parachute system.

The cold structure is also a primary load path during the launch and the separation phases being directly connected to the launcher through the bottom panel that plays a key role for the overall structural performance. A conical adapter provided with the necessary pyrolock devices accomplishes this mechanical interface.

E. Thermal Control Scope of the TCS (Thermal Control System) is to provide a suitable environment to the internal structure and

equipment / payloads, ensuring reliable thermal performance of all internal equipment / payloads and structures during all mission phases including post landing, keeping their temperature level within the applicable design ranges.

EXPERT is a ballistic capsule mainly subjected to the high temperature aerothermal fluxes during the reentry phase. There are three main sources of heat for EXPERT internal thermal environment:

o the thermal interfaces with TPS (radiative and conductive). Radiative is when the TPS acts as a barrier to the external aerothermal fluxes creating an internal radiative environment temperature controlled. From this point of view the TPS is considered as a boundary for the TCS. The internal side of TPS has a natural hemispherical emissivity of 0.42, providing some radiative coupling between internal units/structures and the TPS. Conductive is when the fixation points of the internal structure to the TPS act as a source of conductive flux entering the internal environment;

o the internal equipments/payloads are subjected to the convective exchanges with the air entering the capsule during reentry;

o the heat dissipation load generated by electronics. The TCS design is based on conventional passive solutions like doublers, thermal filler, paints, thermal

washers/stand-offs. The EXPERT passive thermal control system consists of:

o black paint or high emissivity coatings on all the internal structures and on all the equipment/payloads to increase the internal radiative exchange and to reduce the internal thermal gradient;

o all the electronic boxes (equipment/payload) are placed on the supporting honeycomb panels via the interposition of thermal filler to increase the conductive exchange to the underlying panels;

Figure 12. Cold structure architecture

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o use of aluminum thermal doublers under some electronic units to be controlled until touch down is foreseen to reduce the temperature gradient and to postpone in time the peak temperature, by locally increasing the thermal capacity;

o linear de-coupling of the TPS from the internal structure is foreseen through low conductivity attachment points;

o no radiative decoupling (as use of low emissivity shields at TPS internal side level) is envisaged in the current design.

o No need of thermal heater due to the summer launch season (current baseline) o Thermocouples are used for internal equipment and other local items monitoring during test/flight as

required.

F. Avionics and Software The avionics architecture includes the on-board data handling and mission management functions. The EXPERT OBDH subsystem provides the timer sequence reference and the command issuing for the Mission

profile events. It is also able to store on the EXPERT memory the payload and system data collected during flight. Other main functions are the execution of the navigation function, the interface to the System and the payload users, the provision for activation commands, and the data storing function using flash-type crash-resistant mass memory units.

The EXPERT power subsystem provides for electrical power generation, distribution and regulation to EXPERT system and payload items, according to the mission profile and for about 700 Wh total energy amount.

The EXPERT on-board software design will be strictly related to the EXPERT avionics architecture, in the sense that it can be considered as part of it being designed to run on the relevant Data Handling Unit (DHU). The overall EXPERT On-Board SW architecture embeds a set of Computer Software Configuration Items (CSCI's) supporting the implementation of the EXPERT automated control and monitoring functions. These CSCI's are classified either in software or in firmware.

At this stage of the EXPERT phase B the On-Board SW Architecture is composed of mainly two CSCI's which control the EXPERT functions:

o the Mission Application SW, actuating the following macro-functions: - Autonomous activation and SW modes co-ordination; - Separation monitoring; - Mission phase determination; - Polling of the on-board units; - Formatting and storage of the gathered data - Management of the stored data - Distribute and control power to on-board units; - Control of the parachute opening process; - Ground test support and verification.

o the Navigation SW, actuating the following macro-functions:

Figure 13. Avionic architecture

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- Acceleration & Angular Rate Monitoring; - Parachute triggering and control mode logic; - Landed condition logic.

Both the a.m. CSCI's run on the same HW platform and manage the on-board data as gathered from the system units (e.g. accelerometers, gyros, temperature sensors, FTM instrumentation, specific devices).

All the data are stored on board in dedicated mass memory unit. They are kept up to the end of the mission allowing the ground team to dump them from the memory for post flight analyses.

The EXPERT On-Board SW run on an appropriate real-time operating system in order to allow the management of the navigation functions. Presently a 25 Hz sampling is foreseen.

The EXPERT On-Board SW architecture is based on the software control concepts and as such the software interfaces interconnecting busses are based on the following concepts and protocols:

o Processing Frame Concept o MIL-STD-1553B, Notice 2 o CCSDS Recommendation, CCSDS 701.0-B-2 o RS422 and MIL-1553 Standard Protocols.

G. Descent and recovery system The guideline for the EXPERT’s descent and landing system design is to have a cheap and reliable system. For

this reason, the EXPERT’s parachute is conceived as easier as possible, although most of more complex kind of solutions appear as very effective and with interesting properties.

The baseline solution uses a three stage circular parachutes, with a mortar ejecting system. The parachute is conceived with a first stabiliser parachute (SP), a drogue parachute (DP) and a main parachute (MP).

In order to avoid the possible instability during the re-entry transonic phase, EXPERT is equipped with a small circular supersonic parachute with almost no drag capability but able to be opened at mach 2. The SP is foreseen to be left only after the transonic phase with a reference mach of 0.7-0.82 and during this phase it can extract the DP bag. The drogue parachute is conceived to be opened at 13.5 km with a speed of 250 m/s and its main scope is to reduce the velocity in order to get the aerodynamic conditions compatible with the main parachute opening. These conditions are 67 m/s at 2500 m altitude. Moreover the DP extracts the MP’s bag. The final stage of the D&L system is designed in order to minimise the shock at landing and to guarantee the survivability of the payloads as well as safe retrieval of the data mass memory. The reusability of the system was not guaranteed. The design landing velocity is 6 m/s.

H. Operations aspects The mission analysis has pointed out the major flight events contained in the mission profile, as shown in fig. 14

and hereafter summarized: o the EXPERT re-entry capsule is launched from a submarine by a VOLNA launcher; o during the ascent phase the capsule is initialised and oriented by VOLNA 3rd stage and then separated; o upon separation from the 3rd stage, the capsule becomes an autonomous system been able to perform a

controlled ballistic flight with an atmosphere re-entry finally assisted by the landing system; o during the ballistic flight, the scientific payloads execute their own experiments and the capsule is in

charge to acquire and record housekeeping and payloads data; o once the scientific phase is completed, the capsule executes the procedure to safely land in the

Kamchatka peninsula landing site. The mission execution aspects have to be considered in the frame of all the mission phases: transportation to

launch site - pre-launch integration - launch & initialisation - ballistic flight - atmospheric re-entry - parachute descent - recovery operations - post flight activities.

The module is delivered at the Russian Assembly and Test Facility approximately 3 weeks before launch. An autonomous post delivery checks out is performed before integration with the launch vehicle. After this activity, the integrated rocket is transported to the loading place to be loaded into the submarine silo. The take off is made when the submarine has reached the position in the Pacific Ocean area estimated such that the landing in the Kamchatka military basis is guaranteed taking into account the foreseen dispersion effects. A set of ground operations requirements are developed in supporting of the EXPERT pre-launch activities, to address requirement to the GSE in order to perform the ground testing, and to define the Launch Site Support required in terms of cost and planning.

The flight execution includes all the phases from “Launch” to “Parachute Descent”. On the basis of the functional requirements and of the mission scenarios, the operational modes & modes transitions as well as the system nominal / off-nominal scenarios have been developed. The modes and scenarios definition allows for

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identification and description of the functions availability and the amount of the resources which can be used at system level for each phase of the mission.

The mission timeline definition has been part of the mission scenario analysis. The results have been also used as input to the power, thermal and data budgeting.

Another important aspect of the EXPERT design consisted in the identification and planning of the whole set of operational tasks to be performed during both the recovery and post-flight operational activities.

The recovery on the Kamchatka peninsula is supported by recovery means onboard the landing vehicle and the Russian forces ground recovery team. Two helicopters of the polygon equipped with radio technical detection equipment fly in 2-3 km altitude along the boundary of the landing zone for visual acquisition and retrieval of the landed vehicle.

The post-flight analysis objectives are to extract reliable data from the flight measurements in order to reconstruct trajectory and dynamic state. This data allow subsequent verification of numerical prediction tools and assessment of the ground facilities with respect to the ground flight extrapolation rules. A preliminary report including the express-analysis results of the VOLNA flight are followed by a final report, including detailed information on the launch results.

III. Scientific Payload During the Phase B of the EXPERT Program, a coordination

and synthesis role of the overall Scientific Experiments to be housed on the capsule has been carried out by CIRA. The phase-B activities were performed using the data supplied by the European Principal Investigators (P.I.), devoted to the development of their own experiments; an assessment of the conceptual design of the P/L instrumentation and of the P/L requirements with respect to system specification and harmonisation at system level, and the definition of the P/L Flight Test Measurement (FTM) sequence have been carried out.

Also a payload-specific technical support to the EXPERT Program was given for what concerned the assessment of the payload interface requirements including thermal, mechanical, electrical, data, contamination, operations and programmatics.

The experiments (or P/Ls) officially involved in the EXPERT program, together with the Principal Investigator (P.I.), are reported in table 2.

All these experiments are focused to improve, using state-of-art instrumentation, the understanding of the following critical Aerothermodynamics phenomena:

o Transition, o Catalysis, o Real gas effects on shock wave boundary layer interactions,

Figure 14. Mission profile

Table 2. List of payloads.

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o Micro-aerothermodynamics, o Shock layer chemistry and Blackout.

Special attention is given to the design of the flight measurement sensors themselves, their integration into the TPS as well as to the measurement of the free stream parameters during re-entry using an Air Data System.

P1

Objective: Indirect measurement of the free stream speed vector and free stream density during atmospheric portion of the flight. Instrumentation: 5 integrated pressure/heat flux sensors, mounted directly into the TPS nose.

P2 Objective: Measurement of stagnation and cone heating (temperatures and heat fluxes). Instrumentation: PIREX sensors and thermocouples.

P3

Objective: Measurements of the gas species concentration close to the surface and of surface heat flux Instrumentation: thermocouples, pyrometer and spectrometers.

P5

Objective: Physical understanding of natural and roughness-induced boundary-layer transition during the re-entry atmospheric flight. Instrumentation: Thermocouples, Calorimeters and combined heat fluxes-pressures sensors.

P6

Objective: Physical understanding of shock-wave boundary-layer interaction (SWBLI) with flow reattachment on control surfaces during the re-entry atmospheric flight. Instrumentation:Thermocouples,Micropyrometer and combined heat fluxes-pressures sensors.

P7

Objective: Measurement of Flight SWBLI effects on flat faces (20 deg), and design of a representative experiment in the CIRA Scirocco Facility. Instrumentation: Thermocouples, piezoresistive press. transducer and combined heat fluxes-pressures sensors.

P8

Objective: In-Flight Measurements of pressures and heat fluxes on closed flaps by using infrared and temperature sensitive paint techniques shielded inside the closed flaps. Instrumentation: Thermocouples, cameras, IR camera, excitation light source, strain sensors, pressure sensors

P9

Objective: Non-intrusive measurement of the shock-layer chemistry, through electron beam fluorescence (EBF) techniques. Instrumentation: Spectrometer, Electron gun, UV Camera, Hi-Voltage power supply

P10

Objective: Non-intrusive measurement of the shock-layer chemistry, through UV-Visible-IR Spectroscopic measurements (RESPECT ). Instrumentation: Spectrometer

P11

Objective: Measurement of the boundary layer characteristics and electron density profiles, through Pitot and Langmuir probes. Instrumentation: 32 Pressure transducers, 2 Voltmeter, Scanning valve multiplexer and DAS A/D converter

P12 Objective: Measurements of base-flow characteristics and RCS interactions, through pressure sensors and thermocouples. Instrumentation: Pressure and temperature sensors

P13 Objective: Slip-flow characteristics, through sensitive skin friction measurements Instrumentation: Slip flow sensors

P14 Objective: Measurements of blackout, using reflectometers (embedded antennas). Instrumentation: reflectometry antennas (flush)

P15

Objective: Test of a winglet made of an UHTC leading edge attached to a ODS alloy support. Instrumentation: Thermocouple, fluxmeters, high temperature resistant fiber glass

P16 Objective: Test of an enhanced radiation cooling system Instrumentation: Thermocouple, pressure transducer, cooled plate

Table 3. Payload objectives and instrumentation.

In table 3 the main objective of each experiments, together with the main instrumentation to be housed on the EXPERT capsule, are summarized.

As said before, a Payload optimization activity is currently on going, taking into account both programmatic aspects and scientific returns. However, hereafter the main technical characteristics of the nominal considered Payloads set (not optimized) are summarized, showing in the following figures comparative graphs relevant to the mass, required electrical power and estimated data rate for telemetry.

Fig. 15 reports a bar-chat relevant to Payload masses. A 10% margin has been generally assumed except where

different indication have been provided by PIs. The overall mass of the whole set is in the order of 100 [kg].

Fig. 16 shows the bar-chart relevant to the electrical power required by each payload. Again a 10% margin has been generally assumed and an overall power request of about 335 [W] is foreseen. The highest request is from P/L

Payload Masses

0

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16Payload

Mas

s [k

g]

Figure 15 Payload mass distribution.

Payload Electrical Power

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Figure 16 Electrical power distribution.

Payload Electrical Power

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Figure 17 Data budget distribution.

American Institute of Aeronautics and Astronautics

12

n°9. The downlink data for telemetry required by each Payload, including margin, have been reported in Fig. 17. For

the P/L n°8 it has been considered only the Thermocouples, due to the high data rate related to the camera. A total of about 136 [Mbps] flow rate is foreseen (including the system margins). The acquisition time for each P/L is 119 [s], except for the P/L 9 for which the acquisition time is 25 [s].

Acknowledgments Alenia Spazio, CIRA and ESA would like to thank the Industrial Team and the Payload Community for the

contribution and the support during EXPERT Phase B study, and in particular: o Alcatel ETCA, Bradford Eng., Dutch Space, Oerlikon Contraves Italia, Plansee, SABCA, SONACA,

Space Application Services, Spacebel, Syderal, Technology Univ. of Delft and Vitrociset inside the industrial team; and

o SRC-Makeyev Design Bureau, for the launch & recovery systems and services.

Bibliography [1] J.Muylaert, H.Ottens, L.Walpot, F.Cipollini, G.Tumino, M.Caporicci, L. Basile, A. Schettino, A. Mohammed ,

A. Hoonaert, J. Bonnet, M. Lefebvre, A. Luc-Bouhali, Flight Measurement Technique Developments for EXPERT, the ESA in flight Aerothermodynamic Research programme, IAF 2004

[2] M. Caporicci, C. Reimers, H-J. Heidmann, P. Berthe, L. Basile, M. Bottacini, Potential European Crew And Logistics Vehicles – 2010 And Beyond, IAF 2004

[3] J. Muylaert, L. Walpot, H. Ottens, G. Tumino, W. Kordulla, G. Saccoccia, M. Caporicci, C, Stavrinidis, Preparing for Re-entry with EXPERT: the ESA In-flight ATD Research Programme, 3rd AAAF International Symposium on Atmospheric Re-entry Vehicles and Systems, Arcachon, France 2003.

[4] A. Sansone, A. Schettino, A. Del Vecchio, EXPERT Phase B - Scientific Payloads Contribution to the EXPERT System Specification Document, CIRA-TS-04-326, july 2004

[5] F. Massobrio, R. Viotto, M. Serpico, A. Sansone, M. Caporicci, J-M. Muylaert, EXPERT: An Atmospheric Re-Entry Test-Bed, IAC-04-C8.02

[6] F. Massobrio, L. Basile, M. Caporicci, A. Sansone, M. Serpico, EXPERT, the European eXPErimental Re-entry Testbed, 4th International Symposium on Atmospheric Reentry Vehicles & Systems, 2005