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Chato lox tank helium removal for propellant scavenging presentation 2009

System studies have shown a significant advantage to reusing the hydrogen and oxygen left in
these tanks after landing on the Moon in fuel cells to generate power and water for surface
systems. However in the current lander concepts, the helium used to pressurize the oxygen tank
can substantially degrade fuel cell power and water output by covering the reacting surface with
inert gas. This presentation documents an experimental investigation of methods to remove the
helium pressurant while minimizing the amount of the oxygen lost. This investigation
demonstrated that significant quantities of Helium (>90% mole fraction) remain in the tank after
draining. Although a single vent cycle reduced the helium quantity, large amounts of helium
remained. Cyclic venting appeared to be more effective. Three vent cycles were sufficient to
reduce the helium to small (<0.2%) quantities. Two vent cycles may be sufficient since once the
tank has been brought up to pressure after the second vent cycle the helium concentration has
been reduced to the less than 0.2% level. The re-pressurization process seemed to contribute to
diluting helium. This is as expected since in order to raise the pressure liquid oxygen must be
evaporated. Estimated liquid oxygen loss is on the order of 82 pounds (assuming the third vent
cycle is not required).

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Chato lox tank helium removal for propellant scavenging presentation 2009

  1. 1. National Aeronautics and Space Administration LOX Tank Helium Removal for Propellant Scavenging Dr. David J. Chato Abstract: System studies have shown a significant advantage to reusing the hydrogen and oxygen left in these tanks after landing on the Moon in fuel cells to generate power and water for surface systems. However in the current lander concepts, the helium used to pressurize the oxygen tank can substantially degrade fuel cell power and water output by covering the reacting surface with inert gas. This presentation documents an experimental investigation of methods to remove the helium pressurant while minimizing the amount of the oxygen lost. This investigation demonstrated that significant quantities of Helium (>90% mole fraction) remain in the tank after draining. Although a single vent cycle reduced the helium quantity, large amounts of helium remained. Cyclic venting appeared to be more effective. Three vent cycles were sufficient to reduce the helium to small (<0.2%) quantities. Two vent cycles may be sufficient since once the tank has been brought up to pressure after the second vent cycle the helium concentration has been reduced to the less than 0.2% level. The re-pressurization process seemed to contribute to diluting helium. This is as expected since in order to raise the pressure liquid oxygen must be evaporated. Estimated liquid oxygen loss is on the order of 82 pounds (assuming the third vent cycle is not required). www.nasa.gov 1
  2. 2. National Aeronautics and Space Administration LOX Tank Helium Removal for Propellant Scavenging Test Dr. David J. Chato Presented January 8th 2008 at AIAA Aerospace Sciences Meeting, Orlando, FL 2 www.nasa.gov
  3. 3. National Aeronautics and Space Administration Introduction: • Helium used to pressurize the oxygen tank since this produces significantly lighter gas residuals at stage burn-out. • Helium substantially degrade fuel cell power and water output • This experiment investigates methods to remove maximum amount of helium pressurant while retaining the maximum amount of the oxygen residuals. www.nasa.gov 3
  4. 4. National Aeronautics and Space Administration Objectives • Understand the amount of residual helium in LOX tanks after landing • Demonstrate the ability to remove the majority of the helium via venting without losing significant quantities of oxygen • Measure the oxygen/helium content of the remaining gases as they would be sent over time to the fuel cell system www.nasa.gov 4
  5. 5. National Aeronautics and Space Administration Approach • Thermodynamic analysis of the system processes will be performed to predict expected helium concentrations before and after various venting scenarios. • Ground testing will be conducted to validate the analysis predictions and correct the analysis. Tests will be conducted at SMiRF at GRC. www.nasa.gov 5
  6. 6. National Aeronautics and Space Administration Test Tank in Handling Fixture www.nasa.gov 6
  7. 7. Table 2 Close Rang Diode Rake Mean distance Height from Tank Relative from datum Bottom Fill (in) (in) Volume of total Tank) 30% 46.5 21.5625 21.3125 21.0625 20.8125 20.5625 20.3125 National Aeronautics and Space Administration Temperature Diode Location Table 1 Broad Range Diode Rake Relative Fill Volume of Total Tank* Height from bottom of tank (in) Distance from datum* (in) 5% 6.35 61.21 10% 9.57 57.99 20% 15.32 52.24 30% 21.03 46.53 40% 26.75 40.81 50% 32.47 35.09 60% 38.19 29.37 70% 43.91 23.65 80% 49.63 17.93 90% 55.51 12.05 95% 59.41 8.15 www.nasa.gov 7
  8. 8. to vacuum pum p 3 e from tank bottom 5 National Aeronautics and Space Administration Gas Sample System 5 5 www.nasa.gov 8
  9. 9. National Aeronautics and Space Administration Tests Completed Test ID Number Starting Pressure (psia) Ending Pressure (psia) Notes 8 50 20 Liquid Nitrogen Checkout 12 50 20 18 100 20 Gas sample data not available 21 150 20 24 50 20 Cyclic vent Three vents total 27 50 20 29 50 20 Direct vent, No gas sample holds www.nasa.gov 9
  10. 10. Test 12 Start Test 12 End Test 27 Start - Test 27 End National Aeronautics and Space Administration 0 d6 50 E Test Results for Vents from 50 psia 100 - Test 29 Start - f - Test 29 End G Test 24 Cycle 1 Start - -0- - Test 24 Cycle 1 End 0 0 30 60 Height from tank bottom www.nasa.gov 10
  11. 11. National Aeronautics and Space Administration Test Comparison for Vents from 50 psia and 150 psia 100 A Test 27 Start d 0 Test 27 End E 50 Test 21 Start E — t — Test 21 End x 0 0 30 60 Height from tank bottom www.nasa.gov 11
  12. 12. Test 12 Start Test 12 End Test 27 Start - Test 27 End National Aeronautics and Space Administration 0 d6 50 E Test Results for Vents from 50 psia 100 - Test 29 Start - f - Test 29 End G Test 24 Cycle 1 Start - -0- - Test 24 Cycle 1 End 0 0 30 60 Height from tank bottom www.nasa.gov 12
  13. 13. National Aeronautics and Space Administration Test Results for Three Cycle Vent Test 100 0 as 0 c0 50 c0 U E0 0 0 30 60 Height from Tank Bottom (in) www.nasa.gov 13
  14. 14. National Aeronautics and Space Administration L 200 L Temperature Profiles During Three Cycle Vent 400 0—Start of Cycle 1 — —*— — End of Cycle 1 Start of Cycle 2 — ^— — End of Cycle 2 e Start of Cycle 3 — ^— —End of Cycle 3 0 0 30 60 Height from Tank Bottom (in) www.nasa.gov 14
  15. 15. National Aeronautics and Space Administration 100 as 02 50 E7 Time History of Three Cycle Vent 60 .y C. 30 L HHLa n He Middle He Bottom o Gas Analyzer 0 _!L_ Pressure history __^ 0 6:00 AM 12:00 PM 6:00 PM 12:00 AM Time (hours:minutes) www.nasa.gov 15
  16. 16. National Aeronautics and Space Administration Preliminary Results • Significant (>90%) Helium is found in the tank after draining • Although a single vent cycle reduces the helium large quantities remain • Three vent cycles are sufficient to reduce the helium to small (<0.2%) quantities • Repressurization seems to contribute to diluting helium • Propellant loss estimated at 82 lbm assuming third vent cycle is not required www.nasa.gov 16

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