Development of Feedwater Supply Assembly for Spacesuit Cooling

Washington University in Saint Louis Department of Mechanical Engineering and Materials Science

Campus Box 1185One Brookings DriveSaint Louis, MO 63130

Development of Feedwater Supply Assembly for Spacesuit Cooling

Final Report

Team Lead / Flyer

Kaitlin BurlingameUndergraduate Senior

Mechanical Engineering/Biomedical Engineering

(407) [email protected]

Flyer

Alex FrancisciUndergraduate Sophomore

Electrical Engineering/Computer Science


Flyer

Julia GreenbergerUndergraduate Senior

Systems Science & Engineering


Flyer

Jessica LoyetUndergraduate Senior

Mechanical Engineering(618) 792-0567

[email protected]

Flyer

Andrew WiensUndergraduate JuniorElectrical Engineering/Computer Engineering


Ground Crew

Tyler BarkinUndergraduate Senior

Mechanical Engineering(516) 232-6378

[email protected]

Faculty Supervisor

Dr. Guy GeninAssociate Professor of

Mechanical Engineering & Materials Science(314) 935-5660

[email protected]

NASA Mentor

Ian Anchondo(281) 244-5375

[email protected]

1. Table of Contents

1. Table of Contents.................................................................................................................... 22. Introduction.............................................................................................................................. 33. Abstract................................................................................................................................... 44. Background and Design Goals.................................................................................................55. Design Process....................................................................................................................... 6

5.1 Sensor Designs.................................................................................................................65.2 Bladder Designs................................................................................................................7

6. Final Design Concept...............................................................................................................97. Test Method.......................................................................................................................... 10

7.1 System Overview............................................................................................................117.1.1 Containment Box..........................................................................................................117.1.2 Test Bed...................................................................................................................... 127.2 Trial Description..............................................................................................................147.3 Test Bed Operation.........................................................................................................14

8. Results and Data Analysis......................................................................................................158.1 Bellows Performance.......................................................................................................158.2 IR Sensor........................................................................................................................ 188.4 Flow rate......................................................................................................................... 218.5 Low level alert.................................................................................................................22

9. Evaluation of Design Concept................................................................................................2310. Difficulties of Design Implementation....................................................................................2411. Suggestions for Future Solutions..........................................................................................2712. Outreach............................................................................................................................. 2913. Conclusion........................................................................................................................... 2914. Bibliography......................................................................................................................... 2915. Acknowledgements..............................................................................................................30Appendix A: IR Sensor Data......................................................................................................30Appendix A: IR Sensor Data......................................................................................................34

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2. Introduction

Washington University in St. Louis’s (WUSTL) Reduced Gravity Team was selected to conduct research through

NASA’s Systems Engineering Educational Discovery (SEED) program. As part of the SEED program, each

selected team, with the assistance of a NASA mentor and a faculty mentor, develops an experiment to test

onboard a reduced gravity aircraft. The team writes all necessary documentation, builds the experiment,

builds the test bed, flies the experiment on the reduced gravity aircraft, and, after, conducts data analysis to

answer their research questions.

The WUSTL team, consisting of six students from a variety of engineering disciplines, was assigned the project:

Development of Feedwater Supply Assembly for Spacesuit Cooling. Our team was tasked with designing a

Feedwater Supply Assembly (FSA) for the next spacesuit’s Advanced Portable Life Support System (APLSS). After

several months of planning and ground testing, our team tested our design in April aboard the Zero-G Corporation’s

modified Boeing 727 aircraft which creates a microgravity environment.

The primary objective of our project was to design, prototype, and test a novel Feedwater Supply Assembly that met

a set of criteria provided by our NASA mentor. The FSA prototype was tested in two separate microgravity flights.

Through the project, we aimed to create a functional FSA prototype and learn more about the design process and

feasible design characteristics for a FSA.

As part of the microgravity test flights we also sought to conduct science and engineering outreach to K-12 students.

This year, we gave outreach presentations to local students and conducted outreach experiments demonstrating the

characteristics of gravity. In addition, photos and videos are available on our website.

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3. Abstract

An astronaut’s spacesuit provides protection from the extreme temperatures and lack of oxygen in outer space

during an Extravehicular Activity (EVA). Engineers at the NASA Johnson Space Center are currently working to

design a life support system for the next generation spacesuit called the Advanced Portable Life Support System

(APLSS). The APLSS is worn as a backpack and consists of three main subsystems: the oxygen system, the

ventilation system, and the thermal system. Water for use in the thermal loop is stored in a water bladder system

called the Feedwater Supply Assembly (FSA). Washington University’s Reduced Gravity Team had the opportunity

to design, build, and fly a FSA as part of NASA’s Systems Engineering Educational Discovery Program. Essential

to the FSA is a low level alert that sends a signal to the CM as a warning when there is enough water left for 30

minutes of cooling. In the microgravity trials, we tested the FSA’s ability to meet the required outflow rate, send a

low level alert to the CM when the bladder reaches a specified low volume, and recharge, allowing the bladder to

function for multiple EVAs. Our initial design had seven bellow shaped bladders manifolded together and mounted

to an aluminum frame. An aluminum plate across the top of the seven bladders helped maintain a constant height

in all seven bladders by sliding in the aluminum corner channels. Infrared (IR) sensors mounted in the corners of the

aluminum frame would take height measurements which would be averaged, and, along with knowledge of the

bladder diameters, would allow the volume of water in the bladders to be calculated. For the prototype, a smaller

version of the design with only three bladders and one IR sensor was used. In addition, guide wires were placed

around the bladder to constrain them and minimize bowing. In 1-g and 2-g, the bladders bowed, but in microgravity

(0-g) they filled and depleted without bowing. While the IR sensor’s distance measurements were not precise, the

measurements were repeatable, having the same voltage for a given distance across trials. More than half of the

trials had a flow rate of greater than 3 lb/hr, demonstrating that our system met the required outflow and inflow rates.

Comparing the flight video to the data collected by the laptop also showed that the low level alert operated as

intended. Our FSA design did not meet all of the given requirements and therefore was not an ideal design for the

APLSS, but its testing did demonstrate that using bellows shaped bladders and IR sensors are viable design

choices for the FSA. The lessons learned from this project will be used as NASA engineers move forward to finalize

the APLSS FSA design.

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4. Background and Design Goals

An astronaut depends on their spacesuit for protection from the extreme temperatures and lack of oxygen in outer

space during an Extravehicular Activity (EVA). Spacesuits must provide life support, but also allow the crew

member (CM) to move with minimal restrictions. Because the spacesuit is integral to the CM’s performance during

EVA, engineers are continuously improving the spacesuit’s design.

Engineers at the NASA Johnson Space Center are currently working to design a portable life support unit that will be

completely packaged by September 2012. In the new spacesuit design the APLSS will replace the Portable Life

Support System (PLSS) that is used in the Extravehicular Mobility Unit (EMU), which is the spacesuit currently in

operation. The APLSS is worn as a backpack and consists of three main subsystems: the oxygen system, the

ventilation system, and the thermal system. The oxygen system provides the CM with pressure regulated oxygen.

The ventilation system circulates oxygen in the suit while removing potential contaminants and carbon dioxide. The

thermal loop system regulates the temperature of the suit by absorbing heat generated by the CM through the Liquid

Cooling Ventilation Garment (LCVG) [Barnes, Chullen, Conger, Leavitt 2010]. The LCVG is a specially designed

body suit with attached flexible tubing that is donned prior to the space suit. Water runs through the flexible tubing

and absorbs the heat generated by the CM [NASA.gov]. The heated water is evaporated into the vacuum of space

later in the thermal loop. Water for use in the thermal loop is stored in a water bladder system called the Feedwater

Supply Assembly (FSA) [Barnes, Chullen, Conger, Leavitt 2010].

In the EMU, the flexible bladder which holds the water used in the thermal loop is contained in a hard tank internal to

the backpack. This hard tank adds mass and takes up more volume in the backpack. Since the EMU FSA is

located in the backpack, it is pressurized by the backpack’s oxygen. In the APLSS, the FSA will be internal to the

suit. Moving the FSA internal to the suit means the new FSA design must fit within very small volumetric constraints

and that it will now be pressurized to the same levels as the suit’s interior (3.5-8 psi). Furthermore, an ideal design

for a new FSA would also take into account the comfort of the CM and be designed so that it is not ridged or

otherwise uncomfortable or constraining. The water bladder must also be transparent to allow the CM to visually

inspect the bladder for contaminants prior to EVA.

The goal of our project was to design, prototype, and test a FSA with a low level alert mechanism. The low level alert

mechanism is essential to the FSA because it sends a signal to the CM as a warning when only a small volume of

water remains. The low level alert should be triggered when there is only enough water left for 30 minutes of cooling.

The thermal loop controls the inner suit temperature for the crew member, and it is therefore important to know

when the water source for the thermal loop is getting low. The low level alert gives the CM time to end the EVA

before the water level becomes dangerously low. The FSA and its low level alert must function in microgravity (0-g)

and therefore the system cannot require gravity to collapse the bladders or trigger the sensors. In the microgravity

trials, we tested the FSA’s ability to send a low level alert to the CM when the bladder reaches a specified low

volume, meet the required outflow rate, and recharge, allowing the bladder to function for multiple EVAs.

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5. Design Process

In order to design a viable FSA, several physical requirements needed to be met. These requirements were as

follows:

Hold enough water for 8-10 hours of cooling (approximately 10 lb with a rate of 1-3 lb/hr of usage)

Fit within a 14” x 16” x 2” space

Made of a flexible material

Provide a reliable low level alert to the crew member

In addition to these requirements, it was also desirable to have a constant read out on the amount of liquid left in the

bladder.

With these design constraints in mind, we brainstormed and studied in closer detail several ideas. A total of four

ideas made it beyond our initial brainstorming stages. These four ideas are the following:

Flexible air bladder within a water bladder

Hard outer casing with flexible inner water bladder

Pressure infuser bag over an IV bladder

Bellows style bladders in an aluminum frame

5.1 Sensor Designs

Each of these ideas also had associated methods of monitoring the water level, including infrared sensors, Hall

effect sensors, conductive elastic material, and pressure gauges. In several of the designs that we considered, the

bladder would be compressed in the depth dimension so that the water bladder would be two inches thick inflated

and flat when deflated. Hall effect sensors detect the strength of a magnetic field making them a good fit for

concepts where the change is depth of the bladder is small and the magnetic field can be easily measured. Our idea

called for placing an array of magnets on one side of the bladder and an array of Hall effect sensors on the other

side. By taking readings from the array of sensors it would be possible to not only determine how much water was

remaining and the flow rate, but even, to a limited degree, to have a three dimensional image of how the bladder

was deflating. Hall effect sensors would not work for bladders which deflate vertically because a magnetic field drops

off at the cubed root distance from the magnetic source meaning a huge magnetic force would be needed at one

end of the bladders in order for a Hall effect sensor to sense it at the other end. This large magnetic field might

interfere with other critical systems and would require a large amount of electricity or a very heavy permanent

magnet.

Another sensor idea that we tried to apply to each of our concepts was the use of a conductive, resistance changing,

stretch fabric. This fabric is designed to take an electrical current and to output different resistance values depending

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on how much it is stretched. Our idea was to develop a bladder that fit the dimensions of the space and then to

stretch this fabric over the surface of the bladder. As water exited the bladder the resistance value would change

and allow us to monitor quantity of water remaining and the flow rate of the water. We did not choose this option

because of our final bladder design choice, the bellows style bladders. The complex nature of our final bladder

design choice would have made stretching the fabric very difficult. This sensor would have worked well on a bladder

that compressed in the depth dimension because it would not require the fabric to stretch too much. It appeared that

the fabric would not be able to stretch the desired distance on our final design because the bellows style bladders

were expected to have a minimum height of approximately 1 inch and a fully inflated height of 6 inches. In fact, the

bladders were actually able to expand to at least 7 inches, and in initial tests, where the bladders were not

connected to the fluid loop, were able to achieve 9 inches. Though the idea was not tested, it was presumed that the

fabric did not have a stretch ratio even close to 1 to 6.

5.2 Bladder Designs

The first bladder design concept, a flexible air bladder within a water bladder, pushed water out of the water bladder

by inflating an empty air bladder within the water bladder. As more water was needed, the inner air bladder could be

inflated more using an external compressed air tank which would fill more of the space within the water bladder

thereby pushing more water out. The back pressure on the pump could be monitored with a pressure gauge, which

would also be used to control the amount of air added to the inner air bladder. Since the positive displacement pump

required a 3psi back pressure, once the pressure gauge monitoring the back pressure dropped below this critical

level, it would trigger a process that would then add additional compressed air to the inner bladder, thereby

increasing the internal pressure of the system and consequently the back pressure on the pump. The low level alert

would be monitored by pressure gauges, or with the elastic conductive material described above. As the material

was stretched, its resistance would change, triggering the low level alert at a certain resistance. We did not choose

this design due to the complexity of the control system and the need for compressed air.

The second idea was similar to the first in concept. This design consisted of a hard outer casing, made of aluminum

with a flexible water bladder inside. As more water was needed, or a higher back pressure on the pump was

required, compressed air would be added to the aluminum case, compressing the water bladder within. The low

level alert would be triggered by Hall effect sensors. We did not choose this design due to its complexity, need for

compressed air, rigid design, and weight.

The third design was also similar to the first design, but instead used multiple bladders, or, in this case, IV bags

inserted into pressure infuser bags. As the pressure infuser bags were inflated, they would compress the IV bags

filled with water. Both the IV bag and the pressure infuser can be found pre-fabricated, simplifying the design and

reducing costs. In addition, the design was flexible which would make it fit more comfortably in the suit. A preliminary

prototype of this design was completed, but it was not chosen because the number of prefabricated IV bags and

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pressure infuser bags needed in order to provide the needed amount of water (10 pounds) would not fit within the

allotted volume. This design could be feasible in the future if the bags were custom made to fit the volume.

The last design, which was the design we chose and built, called for 7 bellow shaped bladders manifolded together

and mounted to an aluminum frame. The bladders ideally would have had an outer diameter of 2” with an inner

diameter of 1.5” and a height of 15.5” (which would have given a capacity of 260 in3 or 9.5 lbs of water). An

aluminum plate across the top of the seven bladders would help maintain a constant height in all seven bladders by

sliding in the aluminum corner channels. The top plate would also provide an attachment point for four bungee cords

which would provide compression to the bladders and force water out. At the bottom of the frame would be another

aluminum plate with 7 holes cut into it so that the outlets of the bladders could pass through, while providing support

to the bottom of the bladders, as well as the anchor point for the four bungee cords. The water outlets of all bladders

flowed into the water manifold which had a singular water outlet which attached to the rest of system. Infrared (IR)

sensors mounted in the corners of the aluminum frame would take height measurements which would be averaged,

and, along with knowledge of the bladder diameters, would allow the volume of water in the bladders to be

calculated. This design was chosen due to its simplicity in concept. It also has the added benefit of being purely

manufactured, allowing for flexibility in the build process in order to get the exact system desired. Figure 1 shows

this design in more detail.

Figure 1. Preliminary FSA Design

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6. Final Design Concept

The initial design required several modifications as the prototyping and testing process progressed. These

modifications included addressing the following issues:

Top plate did not raise and lower evenly

Bellow bladders bowed outwards when compressed

Insufficient funding to fabricate seven full scale bladders

Figure 2 shows an initial prototype of this design.

Figure 2. Initial FSA prototype

In order to overcome these difficulties, several solutions were implemented. First, since the funding was not

sufficient to build a full scale prototype, three bladders were fabricated instead of seven. Additionally, they were only

6” tall instead of the full 15.5” and had a 0.75” inner diameter instead of 1.5”. The reason for choosing three

bladders was to be able to test the idea of manifolding multiple bladders together, while still minimizing costs.

To prevent the top plate from moving unevenly, side blocks were added at the ends of the top plate. In Figure 2, the

top plate is the piece being held. These blocks at first provided too much friction for the bungee cords to overcome,

so grease was added and the blocks were loosened slightly. These blocks allowed the top plate to travel up and

down the frame more easily, but the bungee cords still caused the top plate to move unevenly and their compressive

force caused the bladders to bow more severely. After further testing and discussion, it was realized that the pump

could empty and fill the bladders unassisted and that the internal pressure of the suit (3.5-8 psi) would provide the

needed back pressure to the positive displacement pump. Since the additional back pressure provided by the

bungee cords was no longer necessary, they were removed from the FSA.

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The last issue encountered, the bowing of the bladders, was solved by adding a total of eight “guide wires” around

each bladder. The wires in this design were twine, but other materials could also be used. These changes can be

more clearly seen in the picture of the final prototype shown in Figure 3.

Figure 3. Final FSA Design

7. Test Method

The primary test objectives during the two reduced gravity flights were (1) to determine the FSA’s ability to signal a

low water level alert at water discharge rates of 1-3 lb/hr at the minimum and (2) to recharge water back into the

bladder for repeated use.

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7.1 System Overview

The system used during the test consisted of the containment box, the Feedwater Supply Assembly, a water loop

with associated instrumentation, and a data acquisition system.

7.1.1 Containment Box

The containment box was a walled, sealed glove box that housed all subsystems besides the data collection

equipment and which had for four attachment points to the aircraft. The box was made of ¼” thick

Polycarbonate, and all edges were lined with 1/8” thick angle aluminum, as shown in Figure 4. The

Polycarbonate was attached to the angle aluminum using ¼-20 bolts and locking nuts. The outside

dimensions of the box were 24” x 24” x 24”. The seal ensured that no water escaped the box and entered the

main cabin of the aircraft. A putty sealant was used to seal the box. The attachment points to the aircraft were

brackets placed on the outside of the box. Two holes in the box were fitted with gloves which were sealed to

the wall, thus maintaining the overall seal of the box. All fasteners holding the box together were sealed. A

structural analysis was completed to ensure all attachment points to the plane could sustain all expected g-

loads. The analysis proved a solid containment box design.

Figure 4. Containment box model

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7.1.2 Test Bed

The test bed supported the operation and monitoring of the FSA by creating a fluid loop where fluid could be

discharged from and pumped back into the water bladder. The only fluid in the system was water which was doubly

contained by the fluid loop and the containment box. The test loop was composed of the FSA, a positive

displacement pump, a water reservoir, valves, and pressure sensors. The components were connected with flexible

nylon tubing. A spatial layout of an early concept of the test bed can be seen in Figure 5.

Figure 5. Spatial layout of test bed

The final test bed layout is shown in Figure 6. It should be noted that the waste water reservoir shown in Figure 5

was converted to a spare water reservoir in the final design because using one reservoir allowed the water in the

test bed to be reused in all of the trials. Furthermore, an additional valve and additional pressure gauge were added

to the final design.

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Figure 6. Final test bed layout

The test bed was instrumented with two pressure sensors. These pressure sensors monitored the pressure around

the fluid loop, measuring the back pressure going into the pump and the pressure drop through the fluid loop. The

pressure sensors were monitored by a data acquisition system (DAQ) controlled by a LabView program.

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Initially, the installation of a flowmeter and a temperature sensor into the test bed was also considered. The

flowmeter would have directly measured the flow rate from the FSA, making it easy to verify that the design met the

flow requirement. However, flowmeters usually create large pressure losses in the system because the fluid must

flow through the sensor. Since it was possible to indirectly measure the flow rate in other ways, the flowmeter was

eliminated from the design to decrease the pressure loss. Indirect methods to measure flow included taking the

derivative of the IR sensor’s distance measurements, using the distance measurements to calculate the change in

volume from the beginning to the end of the trial, or calculating the change in volume by measuring the volume of

water displaced to the water reservoir over a certain period of time. The temperature sensor would have measured

the fluid temperature running through the loop, allowing specific properties of the water (such as exact density) to be

easily determined. However, the temperature sensor would also have caused a small pressure loss in the system

and been an added cost and complexity to implement. Instead of including the temperature sensor, a thermometer

was used to monitor the air temperature, which was judged to be accurate enough to provide temperature

information needed to calculate the necessary fluid properties because the temperature of the fluid was not

changing by a large amount compared to the surrounding temperature.

The test bed components were connected with clear flexible nylon tubing and white acetyl quick disconnect fittings

and instant tube fittings. Metal tubing was also considered for the project because it was less likely to leak than the

flexible tubing and could resist higher pressures. Metal tubing also would have been free of plasticizers which can

damage the pump if they leach into the system. Despite this advantage, the flexible tubing was chosen because it

was much easier to change the configuration of the tubing if the test bed changed. The flexible tubing was also

easier to assemble and while it had a lower pressure limit, the limit was sufficient for the experiment. The flexible

tubing was specifically chosen to be plasticizer free to protect the pump.

7.2 Trial Description

The trials were divided into two different types of tests in order to record data to analyze the three major objectives of

this FSA design. The first type of test tested the FSA’s low level alert by filling the bladders of the FSA to slightly

above the low level amount and then depleting the bladders completely. Testing a small amount of volume change

gave us more data points for verifying the low level alert mechanism than testing the bladders to their full time every

time. The second type of test tested recharge by completely refilling the bladder and then testing nominal flow by

allowing the bladder to fully deplete.

7.3 Test Bed Operation

There were two modes of operation for the test bed: depleting and filling the bladders.

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Depleting the Bladders: Valves were opened which allowed water to flow from the FSA through the pump to the

water reservoir. As water was pulled out of the bladder by the pump, the bladders collapsed vertically.

Filling the Bladders: Valves were opened which allowed water to flow from the water reservoir through the pump

to the FSA manifold. To fill the mechanical compression system with water, water was pumped into the system

through the water manifold at the bottom of the system. As water was pumped in, the bladders were filled with water

and expanded in the vertical direction which pushed up on the top plate of the system.

8. Results and Data Analysis

8.1 Bellows Performance

The bellows functioned in many interesting ways depending on the pull of gravity at any given moment. When filled

with water in standard Earth gravity (1-g) acceleration, the bellows experienced some bowing due to the weight of

the water and top plate (see Figure 7, plate not visible).

Figure 7. Water bladders in 1-g

In order to limit this bowing, guide wires were used to constrain the bladders (see Figure 7) in order to obtain more

accurate data on water flow and the quantity of water in the bladders.

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The efforts at preventing the bowing were less successful under the weight of the water and top plate in twice

standard gravity (2-g) acceleration, as shown in Figure 8, but still prevented the bladders from simply flopping

loosely and possibly becoming punctured on any pointed surfaces.


Our FSA was designed for microgravity conditions and therefore the behavior of the bladders in 0-g was the most

significant of the gravity levels for our application in the APLSS. Fortunately, in 0-g, the bladders behaved exactly as

desired and moved easily and flawlessly straight up and down, as shown in Figure 9. It should be noted that the top

blue line visible in Figure 9 was the maximum height (approximately seven inches) of the bladders when filled in 1-g

before the bladders expanded out in a bowing fashion and were no longer able to expand up. In 0-g trials the

bladders were able to reach more than two and a half inches higher than that mark.

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The average change in height for a depletion trial was 3.02 in, which is equivalent to a change in volume of 0.59 lb.

The range in height changes for depletion trials was from 1.42 to 5.79 in. The average time for a depletion trial was

9.46 sec, with a range from 4 to 15.8 sec. The average change in height for a filling trial was 3.39 in, which is

equivalent to a change in volume of 0.66 lb. The range in height changes for filling trials was from 1.42 to 6.90 in.

The average time for a filling trial was 11.9 sec, with a range from 4 to 19.6 sec. The mass flow rate for each trial is

calculated in Section 8.4, and data for each individual trial can be found in Appendix B. The length of the 0-g period

and time that it took the operators to prepare the experiment for the trial to begin was different for every trial.

Therefore, it is most likely that the variety of filling times and height changes is due to the different amounts of time

available to perform the trials. While there is a variety, the smaller height changes and trial times are more likely

associated with the low level test where the bladders were filled with about one third to one half pound of water each

trial. The longer trials and larger height changes are more likely associated with the full fill and deplete tests where

the bladders were completely filled and depleted in 1-2 trials.

On occasion during the filling and depletion process of our test the bladders seemed to become temporarily stuck.

We believe the plate attached to the top of the bladders may have been catching on the guide rails on one side or

the other causing the top plate height at each end to differ slightly causing the top plate to become wedged between

the guide rails. Because the bladders were attached to the top plate, the top plate getting stuck made the bladders

stop until the push or pull on the water in the bladders freed the top plate by raising or lowering one end or the other

until both ends of the top plate were more even in height.

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Both before and during flight, the bladders tended to fill unevenly. The bladder closest to the inlet/outlet of the water

manifold (bottom right of Figure 9, out of image) would tend to be shorter than the other two both during filling and

during depletion. This difference could have been due to its location on the manifold or due to restrictive linear

motion on the bladders.

This effect happened in every trial but one in all recorded video footage of the second flight (22 parabola trials) and

happened more than 95% of the time in all ground trials filling the bladders with the pump. In the one flight trial

where this did not happen, the bladder was descending from a fully inflated height trial. The height difference was

never more than 0.5 inches because the top plate was designed to not allow significant differences in height

between the bladders. To our best determination, this effect began when the bladders were first filled with the final

fluid loop design. The effect never caused an issue with testing and therefore the cause was never resolved.

Apart from the height differences, the bladders functioned very well in 0-g and provided good data because of

negligible bowing or flexing in 0-g.

8.2 IR Sensor

Our flow rate and volume measurements during the experiment were determined by the IR distance sensor used to

generate the low level alert. The IR sensor measured the distance of the top plate from the top of the frame.

Therefore, a larger distance measured with the IR sensor meant that the top plate is farther from the top of the frame

and there is less water in the bladders. Because the behavior of the IR sensor was critical for our experimental

results, the IR sensor’s response patterns under different operating scenarios must first be investigated.

First, the IR sensor was very sensitive to the material on the reflective surface. When attempting to measure the

distance to a bare brushed aluminum plate, the IR sensor produced no meaningful data. This was remedied by

putting adhesive white paper on top of the aluminum, which produced reliable and reproducible distance

measurements.

Second, the IR sensor produced many undesirable voltage spikes during normal operation. The leftmost graph in

Figure 10 shows an example of this behavior during a trial in 0-g while the bladder was being filled with water. Since

shielded cable was used for all of our analog voltage measurements and we saw no similar spikes in our other

channels, electrical noise was not a likely source for these voltage spikes. Furthermore, this behavior was observed

both in microgravity and during ground testing, so environmental conditions onboard the microgravity aircraft were

not a likely cause. The voltage spikes may have been due to spurious infrared light either from reflections from

surrounding objects or from ambient light sources causing the sensor to occasionally read incorrect distance

measurements for a brief moment.

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Figure 10. Example of IR sensor behavior

To remedy this problem, an effective way to smooth the data in LabView was found. Since the spikes occurred less

often than not, the noise was eliminated by taking the median of all the recent data points. In our system, shown in

Figure 11, the number of data points was set arbitrarily at 40. During accumulation and depletion scenarios, the

delay caused by the smoothing algorithm was always less than one second, since the midpoint of 20 was within the

25 points per second captured by our data acquisition box.

The effectiveness of this system can be seen in the rightmost graph of Figure 10 above, which shows the smoothed

distance measurements produced from the raw voltage input on the left. As shown in Figure 11, the voltage output

was converted to a real distance measurement with an equation given in the manufacturer’s datasheet. This

equation corrected the sensor’s nonlinear voltage output.

Figure 11. LabView system

Another interesting trend in the output from the IR sensor is also apparent: the bladder seems to have expanded

and contracted in discrete steps during both accumulation and depletion. Furthermore, these discrete steps appear

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to have been constant from trial to trial, independent of the bladder’s starting position. Figure 12 shows that this

phenomenon was constant across all trials from both Flight 1 and Flight 2.

Since the voltage steps occurred uniformly and at the same voltage levels across all trials, mechanical factors such

as pump flow behavior and assembly imperfections were eliminated. For example, if the pressure generated by the

pump was pulsing and not constant, as is the case with many positive displacement pumps, the voltage steps

should have drifted over time due to the initial water level and other factors changing across trials. These trends

were not seen in the data. Likewise, imperfections in the aluminum frame or bladder assembly were an unlikely

source because the voltage steps were very regular, occurring roughly every 20 millivolts across all trials, and no

regularly-occurring obstructions were visibly observed in the aluminum guide rails or the bladders themselves.

Figure 12. All accumulation and depletion trials

This unusual behavior was probably due to a limitation of the Sharp® GP2Y0A21YK IR sensor. The Sharp distance

sensor that was used relied on a CCD image sensor with a finite number of pixels. Measuring an analog value such

as distance with a finite number of elements such as the pixels in the CCD image sensor causes the kind of

quantization error experienced in the experiment. Sources confirmed this theory. Although the output of the sensor

was analog, the actual voltage output changed in steps of roughly 20 mV [source: “Sharp Distance Sensors”]. This

reflects the trend in Figure 10, where the output changes in roughly 10 discrete steps between 0.8V and 0.1V, and

likewise for each tick on the Y axis.

Although the output had a resolution of only 20 mV, Figure 12 shows that the voltage levels produced were the

same across trials and across flight days. In other words, while our distance measurements were not precise, our

measurements were repeatable, having the same voltage for a given distance across trials. This was important,

because the low level alert needed to trigger at the same level each time.

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8.4 Flow rate

The pump used in the experiment was able to completely fill up the bladders and deplete them within a single

parabola’s time. For this reason, it was not necessary to run the pump at full speed during the trials. Rather, the

controller was set at a rate where the entire bladder was depleted or filled during one or two weightless periods.

Figure 13 shows the volume of water in the bladder and the duty cycle of the pump during one parabola as

measured by the infrared distance sensor and the pulse-width-modulated pump speed controller. In this trial, the

pump was held at 70% of full speed and the volume increased from approximately 25 mL to approximately 275 mL

at a constant rate.

Figure 13. Relationship between water volume and pump duty cycle

Initially, flow rate calculations were attempted by taking the derivative of the volume, which was calculated from the

distance measurements. Since the bladders had an accordion shape, our volume equation modeled the bladder as

a cylinder with a radius equal to the average of the inner and outer diameter of the bladder. The height of the

cylinder was found by subtracting the sensor’s measured distance to the top of the bladders h(t) from the constant

height of the sensor above the base. Since the measured distance is the only quantity changing with time, the

equation simply reduces to the derivative of the measured distance multiplied by a constant. The basic and derived

flow rate equations are shown below.

FR= ddtV (t )

FR=π ravg2 ddth(t)

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𝐹𝑅=𝜋𝑟𝑎𝑣𝑔2𝑑The nature of our IR sensor caused problems with this approach, however. Since the IR voltage output changed in

steps, and because the derivative of a step is very large to infinity while the derivative of an unchanging quantity is

zero, the flow rate function remained at zero and produced large spikes after every step caused by the sensor.

Thus, the flow rate calculations did not reflect the real flow rate of the system, and could not be used.

Although it was not possible to use the derivative of the IR sensor’s distance measurement to calculate the flow rate

with any kind of accuracy because of the IR sensor’s stepwise output, it was possible to estimate the flow rate by

calculating the overall change in volume in each trial and dividing by the trial length. For trials where the bladders

were being depleted, the average flow rate was 3.82 lb/hr, and the flow rate ranged from 2.35 to 5.33 lb/hr. For trials

where the bladders were being filled, the average flow rate was 3.45 lb/hr, and the flow rate ranged from 1.45 to

4.75 lb/hr. More than half of the trials had a flow rate of greater than 3 lb/hr, demonstrating that our system met the

required outflow and inflow rates. Flow rate data from each trial can be found in Appendix B.

The overall average flow rate for depletion trials was greater than the average flow rate for filling trials, but since the

pump power level was not consistent across all of the trials, the difference in averages does not necessary indicate

that filling the bladders took more time than emptying the bladders. To compare flow rates at a constant pump

power, all of the trials with 70% pump power were compared. At 70% pump power, the average flow rate for

depletion trials was 4.30 lb/hr and the average flow rate for filling trials was 3.63 lb/hr. This different indicates that for

the same pump power, the bladders fill slower than they empty. The water travels along a different path from the

water reservoir to the FSA than it does from the FSA to the water reservoir. It is possible that there is a larger

pressure drop in the path to the FSA which causes the same pump power to deliver less flow to the bladders.

Another possible explanation for this difference is that there was an imperfection in the frame that caused the

bladders to move more slowly emptying than filling.

8.5 Low level alert

The effectiveness of the low level alert system was also studied. Two requirements for a valid low level alert system

are repeatability and reliability. The alert must happen at the same volume level across trials, and the alert must

always happen without failure.

During the two flights in microgravity conditions, the low level alert system did not fail to engage during any of the

trials. Further, as shown in Figure 13, the volume reading from our IR sensor did not provide much resolution due to

the fact that the output voltages were in steps of 20 mV. However, as Figure 12 shows, the volume readings across

multiple trials were the same, that is, the voltage readings did not change.

22

Furthermore, comparing the flight video to the data collected by the laptop also show that the low level alert

operated as intended. To do this analysis, the video’s timestamp was synchronized to the data by comparing the

time of each bladder accumulation and depletion cycle to the time that the pump was engaged as indicated by the

data log. The approximate height of the bladders was found from the video by using the lines behind the bladders,

which marked every 0.5 inches (12.7 mm) vertically. Blue lines marked approximate levels for the low level alert (in

both 0-g and 1-g) and full (in 1-g) while black lines provided additional measurement capability.

The video footage shows that the low level alert occurred consistently at a bladder height of roughly 0.5 inches

(12.7mm) above depleted. This was slightly below the arbitrarily-chosen threshold of 1.0 inches (25.4 mm). A

number of factors could have caused this difference, including data inertia introduced by the running median

algorithm (see Section 8.2) and imprecision in the value of the arbitrary threshold used to generate the alert.

However, although the exact alert level differed from our target in practice, the level was indeed repeatable and

reliable. Analysis of the data showed that the alert occurred consistently during each depletion trial. Additionally,

comparing the data to the video showed that the low level alert occurred at approximately the same volume for each

trial. The center bladder for each of the first three bladder depletion trials at the instant the low level alert triggered is

shown below in Figure 14. This shows that the alert occurred at approximately the same level each time.

Depletion Trial 1 Depletion Trial 2 Depletion Trial 3

Figure 14. Center bladder the instant the low level alert occurred for the first three bladder depletion trials in Flight 1.

9. Evaluation of Design Concept

Overall, our design met a large number of the criteria and goals of the project. Our bladder and fluid loop test bed

design were able to hold water, fill and deplete the bladders, validate the bladder design, and test the viability of an

IR sensor to measure the volume of water in the bladders and to provide a low level alert.

However, we were unable to accomplish some of the necessary criteria and desirable functionalities. Our design

was not able to hold the desired quantity of water and it was not a “soft” design which could comfortably fit to the

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back of an astronaut. We also did not have the capability to rigorously test the durability of our design, including tests

such as changing the bladder orientation and over pressurizing the bladders.

One aspect of actual design that our concept failed to anticipate was that the bladders were made of such flexible

polyurethane that they were unable to expand vertically beyond a certain point when filled with water in 1-g. This

would have been desirable because it would mean that in 0-g the bladders would have been able to expand

vertically without need of a constraint system. (Though not tested, it was suspected that the bladders would flop

around in 0-g as they were filled with water which would have made testing impossible.) Our system depended on

having the bladders expand vertically because an IR distance sensor was being used to measure the height of the

bladders to determine the volume of water in the bladders. However, given the flexibility of the bladder’s initial

design, the FSA was retrofitted with a constraint system to ensure ideal testing conditions, as shown in Figure 9.

After a point when the primary design could no longer change, we realized that it was not necessary to be able to

compress the bladders as part of the design; therefore, some of the initial ideas which we developed might have

worked equally as well, or better, than the design that was tested. Section 5 describes two types of sensors and

several of our initial ideas that we believe might have been equally well suited to be FSA designs as the design we

picked. It should be noted that all of the designs for FSAs described in Section 5 were designed with the need of

compression in mind and so the equally we suited designs would have been those same designs described but

without the compression features.

10. Difficulties of Design Implementation

In designing the bladder many design considerations had to be taken into account. The bladder needed to be

robust, hold a large quantity of water, be flexible, preferably be transparent and compress in such a way that most of

the water could be removed. In addition, as design decisions were made, it became increasingly difficult to stay

within the volume requirements while still being able to hold the desired amount of water.

The primary bladder shape, a cylinder, was chosen because it was likely that a cylinder would be able to provide the

strength needed in order for the bladder to take back pressure. Generally a cylindrical shape is stronger than a

square shape because pressure is distributed across a rounded surface without seams. With a square shape,

pressure is distributed to the edges and corners which are the weakest places because the sides are attached

together at the edges and two pieces of material attached together are rarely stronger than a single piece. We did

not end up testing the ability of the bladder to take back pressure outside of the extra stress created by the 2-g

sessions of our test flights. Our final bladder was made out of thinner polyurethane than we anticipated and so we

do not believe it would have performed well in a pressure stress test.

The bellows design we picked, which allowed us to hold a large quantity of water and get most of the water back

out, was driven mostly by one of our initial compression ideas which was to have the bladders compressed in a

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vertical fashion. Because of the vertical compression we needed a tall (initially specified to be 15.5 inches tall)

bladder that could collapse on itself as water was pushed out. Our natural solution was a bellows style bladder

which could fold in on itself to a very small height yet could expand to a very tall height.

In order for the bellows to be flexible and transparent we chose to use polyurethane because it seemed to provide

the flexibility and ability to be transparent along with having a slight stretchiness which we thought would be useful in

the event of over pressurization to help alleviate stress on the bladder’s joints. As described above, the joints of a

bladder are the weakest points and by making our design a bellows we introduced many possible weak points. To

try a maintain the strength of one piece of polyurethane we decided that the best option for construction of the

bladders was to have the seams made using the radio frequency technique which uses high energy radio

frequencies to heat the polyurethane and then with the addition of pressure, seals two pieces of polyurethane

together as if they were one piece.

Though we were seeking a flexible bladder we thought that the bellows design would allow for stiffer polyurethane to

be used as most of the flexibility would come from the bellow joints. The stiffer polyurethane would give the bladder

structure and ensure that the bladder would be able to rise and fall without bowing. Due to our monetary and

manufacturing constraints we were unable to get stiffer polyurethane and so our bladders were overly flexible

causing undesirable bowing as described in section 8.1.

Finding a manufacturer for these bladders was difficult because of their scale and unique design. We at first

attempted to find a suitable mass produced product which either could stand alone as the bladder or which we could

disassemble to get a component like our bladder design. Unfortunately all of the commercially made products we

found did not have the right diameter (two inches) which was necessary to meet the design specifications for the

FSA. The closest items we found were a hand gas siphon and a water bottle that used the same compressive

design.

Not being able to find our bladder in a mass produced product we turned to custom manufacturing companies.

Initially we sought to have the bladder manufactured overseas on the presumption that the cost of manufacturing

would be cheaper, despite the shipping cost, because of the large number of overseas prototype manufacturers. We

searched Alibaba.com which is a website specializing in providing a central meeting place for customers seeking

overseas manufacturing. Unfortunately most companies required large lot sizes (from 100 to 5000 pieces or more)

which would have provided us with too many bladders at a price far outside of our budget.

We then looked at domestic bladder manufacturers. Many domestic manufactures turned us down because of the

complexity of our design and because of the scale of our design (many manufacturers did not have the capability to

make a cylindrical shape as small in diameter as two inches). We finally found one company that was willing to take

the project but in order to make the bladders they would have needed to design and make specialty dies to allow

them to form the bellows shape. The dies cost alone was almost outside of our budget and the price of each bellows

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was also so high that we would only have been able to afford one or two (total quote for four ten inch tall bladders

was approximately $2500). Similarly, for one large rectangular bladder the price was outside of our range

(approximately $2000).

Fortunately the company that gave us these quotes has a sister company which already had a die in the correct

diameter. They would have needed to extend the die in order to make the bladders taller than six inches which is

what caused us to choose the six in height. In the end we were able to get the bladders for approximately $80 each

but not with the stiffness we desired.

Our recommendation for purchasing bladders that are ideal for the design is to use a domestic manufacturer that

has the desired polyurethane and if they do not have a die, to have one custom made. This ensures that the final

bladder will be able to be self-supporting which we found to be the largest issue with our bladders.

Another difficulty for manufacturing our FSA design was that the frame, top plate, and guide wires need to be very

precisely machined and fitted. Any imperfections or misalignments will cause the top plate to become caught which

will prevent the bladders from filling or emptying.

For the prototype, the guide wires were made out of twine. However, while running the experiment, the wires started

to fray as the top plate rubbed on the wires. The wires should be made out of a material that does not wear down

easily but does not have a rough edge that could puncture the bladders when they bow.

The operation of our FSA design had relatively few complexities. There was only one moving part and the sensor

continuously reported the fluid level. Empty bladders could be refilled by pumping water through a single port in the

manifold and did not require manipulation of any mechanism on the FSA. The bladders were transparent which

allowed for easy inspection. The main difficulty in the operation of our design was the possibility of the top plate and

bladders becoming stuck during depletion (although in our tests the top plate always freed itself). There would be no

way to adjust the FSA during the EVA, so if the top plate becomes stuck, the FSA might no longer function and the

thermal loop would not have a water supply. Additionally, the rigid metal frame could be uncomfortable for the

astronaut in the back of the suit or painful to the astronaut should they fall backwards onto it in a microgravity

environment.

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11. Suggestions for Future Solutions

After designing and testing our system, we discovered several ways in which our design could have better fit the

constraints of the original project, thereby making it more successful.

Because our initial design allowed for the addition of extra compressive forces on the water bladders using bungee

cables, our design focused around a metal frame that acted as a guide rail for a plate which pressed down on the

tops of the bladders. Furthermore, our bladders were made of fairly flexible polyurethane which, under the pressure

of water in 1-g, would bow out of shape when filled with too much water. Because the metal frame was already in

place, we used it to add constraining wires that prevented the bladders from bowing. Later, discovering that it was

not necessary for us to compress the water in the bladders, we realized that if we had used stiffer polyurethane we

could have removed the need for the frame entirely. If the polyurethane used is stiff enough, it will be able to support

the weight of the water and not bow. In 0-g bowing was not an issue because gravity was not pulling on the water,

but the flexibility of the bladders might have still been an issue without the constraint system. Without the constraint

system the bladder would probably wave around in 0-g whenever water was pulled from or put into the bladders

which was not desirable for testing our low level alert system and which would also not be desirable in a final suit

design. However, stiffer polyurethane would also solve this problem because it would not bend easily but the

bellows-style design would allow it to compress and fill in a vertical direction only.

One issue we came across in our design is that even if we had the funds to purchase a full array of seven bladders,

we would not have been able to fit the necessary volume of water into seven 15.5 inch tall bellows bladders. (The

original total design was limited to a space of 14 inches wide, 16 inches tall and 2 inches deep.) To fit the desired

volume of water within the given space we would recommend using a rectangular bellows style bladder wither outer

width and depth of 14 inches and 2 inches, and an inner width and depth of 12 inches and ¾ inches respectively.

With these dimensions the bladder need only be 15.5 inches tall which fits neatly within the space allotted. One

major design issue we discussed with a rectangular bladder is that it would not stand up as well as a cylindrical

bladder to excessive back pressure in the event of a system malfunction. In addition, the corners and edges of a

rectangular bladder would be subject to pressure concentrations which could lead to earlier bladder failure. Similarly,

bellows style bladders could still work but the dimensions would need to be slightly larger than those described in

our original design (seven bladders each with an outer diameter of 2 inches, inner diameter of 1.5 inches, and height

of 15.5 inches).

We determined that the IR sensor was not ideal for giving a perfectly accurate low level alert for two key reasons.

First, the IR sensor had limited resolution; second, the IR sensor required a mounting point on a ridged frame to

measure the change in height of the bladders. Furthermore, the IR sensor was not very good at measuring flow rate

due to the step phenomenon. Though the flow rate issue did not interfere with the low level alert, measuring flow

rate seemed like a desirable metric to be able to monitor. While the sensor that we used would not work for the FSA,

it is likely that a different IR sensor with higher resolution would work for designs with a rigid mounting point.

27

Instead, we recommend using a pressure sensor attached to the bladder manifold in parallel with the bladders.

When a bellows style cylindrical bladder is compressed, a column of water remains in the center of the bladder

which, without the suction of a pump or gravity, will not come out. If water is drawn from the bladders before this

point, a pressure sensor attached to the manifold in parallel with the bladders should give a constant reading of a

negative pressure because water is being pulled out by the pump. However, when the bladders have discharged all

but that final column of water, and the pump pulls on that water, the pressure reading from the pressure sensor

should begin to rise above that initial constant. This will happen because the bladder is already at its natural shortest

size and pulling more water out will require more pressure in order to pull the bladder (which is resisting) in.

This solution addresses the two major problems that we found with the IR sensor. The pressure sensors would have

better resolution and would also not require a mounting position that required a ridged frame. The pressure sensors

would not be able to give any indication of flow rate, but this was not a requirement for the design.

The point where the negative pressure begins to increase could be the low level alert if there is enough total water

remaining in the all of the bladder’s columns combined such that if the pump keeps pulling on the remaining water it

will last long enough to allow an astronaut to get back to a refilling station or vehicle. In other words, the column of

remaining water could be engineered to be a certain volume which would be enough for a low level amount

(assuming the pump is powerful enough to make use of a decent percentage of that water and that the process

does not put excessive extra stress on the bladders such that they malfunction).

An alternative would be to engineer the bladders such that at the bottom they are made from even stiffer

polyurethane than the rest of the bladder which would also make it harder for the pump to draw out the water at the

point when the less stiff part of the bladder is already compressed completely.

Though the test bed we designed allowed us to test the full range of metrics we wished to measure, there are

several areas where it could be improved to provide even better data. First, using solenoid valves in place of the

manually operated valves would improve ease of testing by allowing the tester to use a computer to open and close

the valves which would increase the available testing time in each 0-g window. In our tests, we had to start the motor

a little after 0-g and shut it off a little before exiting 0-g because a tester had to manually shut the valves which took

time. Secondly, the pump could be automated such that it came on and stayed at a predetermined flow rate for a

predetermined amount of time to test various filling and depletion scenarios repeatedly. Because our pump was

manually controlled it was nearly impossible to guarantee the same pump speed and duration from test to test which

prevented exact replication of the conditions of any one test. Finally, our design used pressure sensors with a range

from 0 to 100 psi (and corresponding voltage readings from one to six volts) because sensors with a smaller range

were either temporarily unobtainable or outside of our budgetary means. Therefore, we recommend that in a future

test bed that sensors with a smaller range are used so that more precise voltage readings can be taken and

therefore more accurate data can be captured.

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12. Outreach

Our team conducted several outreach presentations to K-12 students where we shared our experiences as well as

spoke more generally about NASA and engineering. Through these presentations, we aimed to get students excited

about science, engineering, and space, encourage them to pursue careers in science and engineering, and share

our research with the general public. Our team worked with a weekend engineering program for high school girls at

Washington University and with the Schoolroom at St. Louis Children’s Hospital. We also spent several days

working with a middle school engineering class in downtown St. Louis. In addition to talking about our experiences,

we discussed lunar exploration and the students designed, built, and tested their own lunar landers. During all of our

outreach presentations, we asked the students to think of an experiment that they would want to see in 0-g. Based

on these suggestions, we took a toy top and a Slinky on the plane as physics demonstrations. All videos, photos,

and explanations to go along with these demonstrations are available on our website to allow more schools to

benefit from our outreach program.

13. Conclusion

During the course of our project, the Washington University team successfully designed, prototyped, and tested a

concept for the APLSS Feedwater Supply Assembly. Our FSA design did not meet all of the given requirements and

therefore cannot be directly integrated into the APLSS. However, our research did demonstrate that using bellows

shaped bladders is a viable design choice for the FSA and that, with certain designs, an IR sensor can work to

produce accurate low level alerts. In addition, we learned important information about how the bellows bladders

function in 0-g and about the material thickness that is necessary for designing future bladders in that shape. We

also developed a successful test bed design that could be used for future tests of other FSAs. The concepts that we

considered and tested in our project are also being considered by the NASA engineers working on the APLSS, and

the lessons learned from our project will be used as they move forward to finalize the APLSS FSA design.

14. Bibliography

Barnes, B., Chullen, C., Conger, B., Leavitt, G. (2010). Proposed Schematic for an Advanced Development Lunar Portable Life Support System, in Proceedings of the 40th International Conference on Environmental Systems, July 11-15, 2010. The American Institute of Aeronautics and Astronautics.

Burlingame, Kaitlin et al, “Development of Feedwater Supply Assembly for Spacesuit Cooling,” 2012 Test Equipment Data Package, February 2012.

"Learn about Spacesuits." NASA.gov. NASA, n.d. Web. 6 June 2012. <http://www.nasa.gov/audience/foreducators/spacesuits/home/clickable_suit_nf.html>.

"Sharp Distance Sensors." N.p., Oct. 2009. Web. 1 June 2012. <http://askrprojects.net/lego/sharp.html>.

Wight, Samuel, “Effects of Lunar Stimulant on Solar Panels: The Effects of Vibration and Lotus Coating on Solar Cell Dust Retention”, 2010 Test Equipment Data Package, February 2010.

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15. Acknowledgements

We would like to thank the JSC Education Office and Reduced Gravity Office for making this opportunity possible for

us. In addition, our NASA mentor Ian Anchondo and faculty advisor Professor Guy Genin were extremely

supportive throughout all phases of the project. We are also very grateful for the help and advice of Pat Harkins and

Jim Linders from the Washington University Engineering and Chemistry machine shops in our machining work and

design of the fluid test loop.

The Missouri Space Grant Consortium provided funding to make this opportunity possible for our team. Our

university Space Grant Consortium contact, Dr. Richard Axelbaum, helped us with finances and offered support

throughout the project. We are also grateful for funding from the Washington University School of Engineering

Projects Review Board.

Appendix A: IR Sensor Data

The IR sensor data from each trial during both flights are shown below. The measured distance from the top plate is shown as a function of time as the trial progresses.

30

31

32

33

Appendix A: IR Sensor Data

The results from each trial during both flights are shown below. Time is the duration of the trial. Speed is the percent

of max power used in that trial. h1 and h2 are the distance from the top plate as measured by the IR sensor. h1 is

the initial distance and h2 is the final distance. dx is the total change is height over the trial. Volume is the amount of

water displaced during the trial. Flow rate is the average mass flow rate for the trial. Average values across all trials

are given at the bottom of the table.

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Table 1. Results for Emptying Trials

Day Trial Time (s) Speed (%) h1 (mm) h2 (mm) dx (mm) dx (in)Volume

(lb)

Flow rate

(lb/hr)1 1 7.64 70 293 366 73 2.88 0.56 4.391 2 9 90 147 229 82 3.23 0.63 4.191 3 10.68 70 149 256 107 4.22 0.82 4.611 4 12.28 69 220 343 123 4.85 0.94 4.611 5 6 70 292 351 59 2.32 0.45 4.521 6 5 69 301 359 58 2.29 0.44 5.332 1 10 63 308 365 57 2.25 0.44 2.622 2 6 59 308 344 36 1.42 0.28 2.762 3 9 70 307 353 46 1.81 0.35 2.352 4 7 86 313 352 39 1.54 0.30 2.562 5 12 60 161 233 72 2.84 0.55 2.762 6 15.8 59 234 324 90 3.55 0.69 2.622 7 4 90 323 365 42 1.65 0.32 4.832 8 15 98 205 352 147 5.79 1.13 4.512 9 16 93 195 334 139 5.48 1.07 3.992 10 6 59 308 366 58 2.29 0.44 4.45

Avg 9.46 73.44 254 330.75 76.75 3.02 0.59 3.82

Table 2. Results for Filling Trials

Day Trial Time (s) Speed (%) h1 (mm) h2 (mm) dx (mm) dx (in)Volume

(lb)

Flow rate

(lb/hr)1 1 7.64 70 293 366 73 2.88 0.56 4.391 2 9 90 147 229 82 3.23 0.63 4.191 3 10.68 70 149 256 107 4.22 0.82 4.611 4 12.28 69 220 343 123 4.85 0.94 4.611 5 6 70 292 351 59 2.32 0.45 4.521 6 5 69 301 359 58 2.29 0.44 5.332 1 10 63 308 365 57 2.25 0.44 2.622 2 6 59 308 344 36 1.42 0.28 2.762 3 9 70 307 353 46 1.81 0.35 2.352 4 7 86 313 352 39 1.54 0.30 2.562 5 12 60 161 233 72 2.84 0.55 2.762 6 15.8 59 234 324 90 3.55 0.69 2.622 7 4 90 323 365 42 1.65 0.32 4.832 8 15 98 205 352 147 5.79 1.13 4.512 9 16 93 195 334 139 5.48 1.07 3.992 10 6 59 308 366 58 2.29 0.44 4.45

Avg 9.46 73.44 254 330.75 76.75 3.02 0.59 3.82

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Documents

Development of Feedwater Supply Assembly for Spacesuit Cooling