Skip to content
79,433 pages · 13,741 images · since 1994 Browse A–Z Today in space history
Encyclopedia Astronautica The full story of spaceflight
Encyclopedia entry

PPM

Spacecraft · USA

Original archive entry. The text, images and links below are kept as they were written.

PPMS
PPMS
IMIS Primary Propulsion Module
Credit: © Mark Wade

American space tug. Study 1968. The Primary Propulsion Module was the definitive 1960's design for a nuclear thermal rocket stage suitable for interplanetary operations.

The basic NERVA stage was modified to allow for docking and assembly in orbit, storage and reliquefaction of its liquid hydrogen propellant for periods of up to three years on long voyages to Mars and Venus, and to feed propellant to lower stages as needed.

Detailed mass breakdown was as follows:

  • Liquid hydrogen propellant: 174,600 kg
  • NERVA nuclear thermal engine system: 14,500 kg
  • Propellant tank: 22,700 kg
  • Stage equipment: 2700 kg
  • Meteoroid shield: 19,000 kg
  • Interstage structures: 5200 kg
  • 11% growth and contingency allowance: 6800 kg
Country
USA
Engines
Nerva-1
Propellants
Nuclear/LH2
Agency
Boeing
Bibliography
253