Thus, significant technology development may be required for application of SDI/BMD propulsion technologies for planetary missions. RESEARCH CENTER PROPELLANT TYPE O/F MEAN DENSITY (g/cc) REF. I sp (s) NASA NTO/MMH EARTH STORABLE 1.65 1.15 317 NASA O 2 /CH 4 SPACE STORABLE 4 0.86 330 NASA O 2 /H 2 REFRIGERATED 6 0.36 423 USAF CIF5/N 2 H 4 SPACE STORABLE 2.66 1.47 329 USAF OF 2 /C2H 4 SPACE STORABLE 4 1.14 375 USAF N 2 F4/N 2 H 4 SPACE STORABLE 3.23 1.01 358 (none) F 2 /N 2 H 4 SPACE...