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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

Weight305 lb
Vacuum Thrust16,500 lb
Expansion Ratio61:1
Oxidizer/Fuel Ratio5:1
Isp444.4 sec
Propellant Mass856.7 lb (142.8 lb LH2, 713.9 lb LOX)
Propellant Volume32.33 ft3 LH2, 10.03 ft3 LOX

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 Mass1553.6 lb (597.5 lb MMH, 956.1 lb N2O4)
Propellant Volume10.87 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:

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