5. 522, Space Propulsic Prof. Manuel martinez-Sanchez ecture 7: Bipropellant Chemical Thrusters and Chemical Propulsion Systems Considerations (Valving, tanks, etc) Characteristics of some monopropellants( Reprinted from H Koelle, Handbook of Astronautical Engineering, McGraw-Hill, 1961.) Sity s Sensitivit Nitroglycerine 1.60 54964942244Yes Ethyl nitrate 1030394659224Yes Hydrazine 1.01 2050 3952230 Tetranitromethane 1.65 3446 3702180Yes Hydrogen peroxide 1.45 18393418165No Ethylene oxide 0.87 1760 3980189No 1.06 4265201Ye Catalyst Bed Propellant Decompositi Monopropellant concept. SPACECRAFT PROPULSION, by Ch D, Brown AlAA Education Series, 1996 16.522, Space P pessan Lecture 7 Prof. Manuel martinez Page 1 of 12
16.522, Space Propulsion Lecture 7 Prof. Manuel Martinez-Sanchez Page 1 of 12 16.522, Space Propulsion Prof. Manuel Martinez-Sanchez Lecture 7: Bipropellant Chemical Thrusters and Chemical Propulsion Systems Considerations (Valving, tanks, etc) Characteristics of some monopropellants (Reprinted from H. Koelle, Handbook of Astronautical Engineering, McGraw-Hill, 1961.) Flame Chemical Density temp, F D C* ,fps Isp,S Sensitivity Nitromethane 1.13 4002 5026 244 Yes Nitroglycerine 1.60 5496 4942 244 Yes Ethyl nitrate 1.10 3039 4659 224 Yes Hydrazine 1.01 2050 3952 230 No Tetronitromethane 1.65 3446 3702 180 Yes Hydrogen peroxide 1.45 1839 3418 165 No Ethylene oxide 0.87 1760 3980 189 No n-Propyl nitrate 1.06 2587 4265 201 Yes
Standoff Catalyst Bed Heater Propellant valve Thrust Chamber Typical monopropellant thruster.( Courtesy Hamilton Standard. Image adapted from SPACECRAFT PROPULSION, by Ch D. Brown AlAA Education Series, 1996 16.522, Space P pessan Lecture 7 Prof. Manuel martinez Page 2 of 12
16.522, Space Propulsion Lecture 7 Prof. Manuel Martinez-Sanchez Page 2 of 12
Weight(Ibs) 6 0 80 100 120140 Thrust(lbs) Monopropellant thruster weight Image adapted from SPACECRAFT PROPULSION, by Ch D Brown AIAA Education Series, 1996 Thruster we A least-square curve fit of the weight of nine different thruster/valve designs with thrust levels from 1 to 150 lb produces the following relation W=0.34567F053235 The figure above shows the correlation; the correlation coefficient is 0. 97. For low thrust levels, the thruster weight approaches the valve weight an effect that Equation(4.5)will not predict. Use 0. 4lb as a minimum thruster/valve weight for low thrust levels. Note that figure above is for a thruster with single valves 16.522, Space P pessan Lecture 7 Prof. Manuel martinez Page 3 of 12
16.522, Space Propulsion Lecture 7 Prof. Manuel Martinez-Sanchez Page 3 of 12 Thruster Weight A least-square curve fit of the weight of nine different thruster/valve designs with thrust levels from 1 to 150 lb produces the following relation: 0.55235 W F t = 0.34567 The figure above shows the correlation; the correlation coefficient is 0.97. For low thrust levels, the thruster weight approaches the valve weight, an effect that Equation (4.5) will not predict. Use 0.4lb as a minimum thruster/valve weight for low thrust levels. Note that figure above is for a thruster with single valves
MONOPROPELLANT SYSTEMS Pressurant Propellant agm Capillary Bladder Collapsible Cylinder Zero-g propellant control devices Image adapted from SPACECRAFT PROPULSION, by Ch D. Brown AlAA Education Series, 1996 1)Capillary devices, which use surface tension forces to keep gas and liquid separated These are particularly useful for bipropellant systems like the space Shuttle and viking Orbiter because they are compatible with strong oxidizers 2)Diaphragms and bladders, which are physical separation devices made of elastomer or Teflon. These are used by Voyager, Mariner 71, and Magellan Elastomer types are not compatible with oxidizers. 3)Bellows, a metal separation device, used by Minuteman 4)Traps, a check valve protected compartment, used by transtage 16.522, Space P pessan Lecture 7 Prof. Manuel martinez Page 4 of 12
16.522, Space Propulsion Lecture 7 Prof. Manuel Martinez-Sanchez Page 4 of 12 1) Capillary devices, which use surface tension forces to keep gas and liquid separated. These are particularly useful for bipropellant systems like the space Shuttle and Viking Orbiter because they are compatible with strong oxidizers. 2) Diaphragms and bladders, which are physical separation devices made of elastomer or Teflon. These are used by Voyager, Mariner 71, and Magellan. Elastomer types are not compatible with oxidizers. 3) Bellows, a metal separation device, used by Minuteman. 4) Traps, a check valve protected compartment, used by Transtage
H Tank a Tank B N2H4 Valve 3A Valve 3B Filter園 Branch a Filter Branch B Valve TCV IB Line heaters TCV 2B Catalyst Bed leaters Thruster Pair Temperatur ① Normally open pical 12 Places Pressure normally Closed System functional schemati Image adapted from SPACECRAFT PROPULSION, by Ch D. Brown AlAA Education Series. 1996 16.522, Space P pessan Lecture 7 Prof. Manuel martinez Page 5 of 12
16.522, Space Propulsion Lecture 7 Prof. Manuel Martinez-Sanchez Page 5 of 12