May 14th , 2010

1. May 14th, 2010 FMSTR

2. Introduction and Background Concept Design Detailed Design Testing / Results 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 • An optical mass gauge is a viable option Normal Gravity Microgravity Source: NASA

3. Introduction and Background Concept Design Detailed Design Testing / Results Alternative Methods Multipin Plug Vapor Cryo-Liquid Diodes Optical mass gauge will not require settlement or acceleration of spacecraft

4. Introduction and Background Concept Design Detailed Design Testing / Results 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. • Approach: • Build prototype version of sensor • Test in laboratory (with water) • Vibration test • Flight test on a sounding rocket

5. Introduction and Background Concept Design Detailed Design Testing / Results System Layout 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.

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

7. Introduction and Background Concept Design Detailed Design Testing / Results 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

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

9. Introduction and Background Concept Design Detailed Design Testing / Results 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 G-switch All wires secured with nylon harnessing.

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

11. Introduction and Background Concept Design Detailed Design Testing / Results 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

12. Introduction and Background Concept Design Detailed Design Testing / Results 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

13. Introduction and Background Concept Design Detailed Design Testing / Results Vibration Testing Z-Axis X/Y-Axes • Two Tests: • Sine Sweep: 10-2000 Hz • Random • Resonance at: 200Hz • Max Accel: 25G • Outcome: Vibe-Test Passed • Zero parts damaged • Optics remained in alignment • (some power loss)

14. Introduction and Background Concept Design Detailed Design Testing / Results Fringe Counting Methods (Method 1/3) Fractional Method 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 X Y B C A D 1 3 4 5 2 N 0 η β Find the fraction of sine wave that exists before the first peak and after the last peak.

15. Introduction and Background Concept Design Detailed Design Testing / Results Fringe Counting Methods (Method 2/3) Frequency Method #1 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 X Y B C A D 1 3 4 5 2 N 0 Find an average wavelength between the first two peaks and the last two peaks. Divide the average wavelength by the range.

16. Introduction and Background Concept Design Detailed Design Testing / Results Fringe Counting Methods (Method 3/3) Frequency Method #2 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 E B C A D 1 3 4 5 2 N 0 Find the average wavelength between all of the peaks. Divide the average wavelength by the range.

17. Introduction and Background Concept Design Detailed Design Testing / Results Results Uncertainty: +/- 0.95 mL 10.33 mL

18. Introduction and Background Concept Design Detailed Design Testing / Results Full Mission Simulation Test 5 minutes operation 45 seconds pause • 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)

19. Introduction and Background Concept Design Detailed Design Testing / Results Overall Analysis • 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. Introduction and Background Concept Design Detailed Design Testing / Results Lessons Learned • 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. Introduction and Background Concept Design Detailed Design Testing / Results 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