Cryogenics vs. Hypergolics for the Ascent Stage
We need a delta-v from the ascent engines of about 6,136 ft/s.
LH2/LOX Cryogenic Propellants
|Vacuum Thrust||16,500 lb|
|Propellant Mass||856.7 lb (142.8 lb LH2, 713.9 lb
|Propellant Volume||32.33 ft3 LH2, 10.03 ft3
N2O4 / MMH Hypergolic Propellants
|Engine ||Kaiser Marquardt R-40A|
|Weight ||22.5 lb|
|Vacuum Thrust ||870 lb|
|Propellants ||MMH / N2O4|
|Expansion Ratio ||20:1 |
|Oxidizer/Fuel Ratio ||1.6:1|
|Isp ||281 sec (range from 281 to 306 sec)|
|Propellant Mass||1553.6 lb (597.5 lb MMH, 956.1 lb N2O4)|
|Propellant Volume||10.87 ft3 MMH, 10.56 ft3 N2O4|
These propellants might actually freeze (freezing point is 261K for
N2O4, 220.7K for MMH), but
a tiny heating coil would be a trivial addition. Other than that, they
are much easier to store than the LH2/LOX propellant,
and their tankage will occupy a smaller volume.
Further Work Needed:
Copyright © 2007 Artemis Society International, for the
contributors. All rights reserved.
- Detail hypergolic engine
Should work with cryogenics as well, for use in the descent stage
- Calculate cryogenics boiloff, total fuel required
- Calculate tankage masses
- Determine storage
Such as insulation, heating, leak control, etc.
- Determine approximate risk for both systems
- Determine overall cost for both systems
Such as cost of materials, cost of getting the extra mass to the lunar
- Combine cost and risk; decide on ascent stage fuel
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Updated Sun, Dec 20, 1998.