1. May 14th, 2010 FMSTR

2. The Problem and Proposed Solution No current, acceptable solution exists to determine liquid volume in a tank exposed to microgravity, without some form of stratification, tank stirring or spacecraft acceleration Normal GravityMicrogravity An optical mass gauge is a viable option Introduction and Background Concept Design Detailed Design Testing / Results Source: NASA

3. Alternative Methods Alternative MethodBasicsRequirement Capacitive SensorPermittivity of the cryogenic fluid is related to the volume within the tank. Settling / Stratification Flexible Cryogenic Temperature and Liquid-Level Probes A strip of silicone diodes are brought to a certain temperature. Time constants allow for fluid volume measurement. Settling / Stratification Cryo-LiquidVapor Diodes Multipin Plug Optical mass gauge will not require settlement or acceleration of spacecraft Introduction and Background Concept Design Detailed Design Testing / Results

4. Approach: Build prototype version of sensor Test in laboratory (with water) Vibration test Flight test on a sounding rocket Our Objective Objectives: Develop a sensor using an existing measurement technique to accurately determine the liquid volume in a tank in any gravitational environment. Demonstrate its accuracy and reliability on board a sounding rocket mission. Introduction and Background Concept Design Detailed Design Testing / Results

5. Two tanks w/ different volumes of liquid are independently exposed to Gas Cell. Amount of liquid in each can be determined; The two tanks represent fuel/fluid levels at different periods during a mission. System Layout Introduction and Background Concept Design Detailed Design Testing / Results

6. Solid Model of Flight-Ready Prototype Power Supply HeNe Laser Photo Diode Detector Valve 1 Tank 1Tank 2 Valve 2 Piston Gas Cell Servo Laser output into Fiber Introduction and Background Concept Design Detailed Design Testing / Results

7. Major Design Changes The switch from diode laser to a Helium-Neon laser Diode laser does not have the coherence length that we require (only 0.1 mm) A coherence length equal to at least the sensing path length is needed ( > 5 cm) The coherence length for a typical HeNe laser is 20+ cm Introduction and Background Concept Design Detailed Design Testing / Results

8. Specifications 9.5 inches 4.75 inches Introduction and Background Concept Design Detailed Design Testing / Results Payload occupies a half-canister (shared with UNC payload)

9. Specifications Final Weight: 2.90kg (6.39 lbf) Dimensions: 24.15 x 24.15 x 12.1 cm Processor: ATmega328; 1KHz sampling rate Memory (storage): 2GB All wires secured with nylon harnessing. G-switch Introduction and Background Concept Design Detailed Design Testing / Results

10. Construction Gas cell contains Air, determined that xenon or argon are not needed for accurate results in our system. Introduction and Background Concept Design Detailed Design Testing / Results

11. Piston Assembly Servo to drive piston: 486 oz-in Torque Titanium gears Weight: 0.15 pounds ~170 lbf linear force Programmable Pressure test on Piston and Servo completed at 40 psi, maintained pressure Introduction and Background Concept Design Detailed Design Testing / Results

12. Vibration Mount Analysis and Manufacturing Sierra Nevada Corp. required the team to procure its own vibration table mount Suggested that FEA be performed on mount to ensure the first mode is outside of the test range (>2000Hz) Finite Element Analysis showed the first mode was at 3943Hz Introduction and Background Concept Design Detailed Design Testing / Results

13. Vibration Testing Two Tests: Sine Sweep: 10-2000 Hz Random Resonance at: 200Hz Max Accel: 25G Introduction and Background Concept Design Detailed Design Testing / Results

14. Fringe Counting Methods (Method 1/3) 1 2 345 A BC D XY ηβ 0 N η = { location of first peak (A) } β = N – { location of last peak (D) } α = number of visible peaks Fraction of sine wave before first peak: W = η / X Fraction of sine wave after last peak: Z = β / Y Total (fractional) fringe count: T = α + W + Z Fractional Method Find the fraction of sine wave that exists before the first peak and after the last peak. Introduction and Background Concept Design Detailed Design Testing / Results

15. Fringe Counting Methods (Method 2/3) 1 2 345 A BC D XY 0 N Find wavelength between first two peaks and the last two peaks: {X, Y} Find the mean wavelength: μ = ( X + Y ) / 2 Divide range by mean wavelength to obtain fringe count: Total (fractional) fringe count: T = N / μ Frequency Method #1 Find an average wavelength between the first two peaks and the last two peaks. Divide the average wavelength by the range. Introduction and Background Concept Design Detailed Design Testing / Results

16. Fringe Counting Methods (Method 3/3) 1 2 345 A BC D 0 N Find peak locations: { A, B, C, D, E } Formulate a difference array (distance between each peak): D = { B – A, C – B, D – C, E – D } Take an average (mean wavelength): μ = Mean[D] Divide range by mean wavelength to obtain fringe count: Total (fractional) fringe count: T = N / μ Frequency Method #2 E Find the average wavelength between all of the peaks. Divide the average wavelength by the range. Introduction and Background Concept Design Detailed Design Testing / Results

17. Results 10.33 mL Introduction and Background Concept Design Detailed Design Testing / Results

18. Full Mission Simulation Test Introduction and Background Concept Design Detailed Design Testing / Results - Payload paused for 45 seconds after G-switch activation, then the system operated for 5 minutes before shutting down - Initial pause is to prevent potential system damage during high-G environment - All data was recorded to microSD card - Results were successful (good fringe visibility) 45 seconds pause 5 minutes operation

19. Overall Analysis Introduction and Background Concept Design Detailed Design Testing / Results Are you ready for launch? YES Are you happy with the results? YES What work still needs to be completed? Integration with UNC to ensure both payloads will successfully fit within the canister and meet C.O.G. constraints

20. Lessons Learned Introduction and Background Concept Design Detailed Design Testing / Results - Everything takes ~5x longer than you expect - Need a lot of time for testing due to unexpected issues - Detailed early planning leads to success later in the project

21. Conclusions Introduced problems with measuring liquids in zero-g Project work completed, testing results Measured small liquid volume within 1.9% error Testing complete, ready for integration with UNC Introduction and Background Concept Design Detailed Design Testing / Results