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Nuclear Thermal Propulsion- For Manned Missions to the Moon, Mars and BeyondDick Malenfant , N-DO From 1955 to 1973 the United States was involved in a program to apply the concentrated energy of nuclear power, in conjunction with the propulsion efficiency achievable with hydrogen as a propellant, to ambitious space missions. The program originated in the fifties as a ground-launched heavy-lift vehicle for ballistic missiles with thermonuclear warheads. As high-yield multi-stage weapons were reduced in size and weight, this particular application disappeared. However, the efficiency that can be achieved with low molecular weight propellant led to the obvious application of nuclear thermal propulsion to large payload space missions. The laboratory was the key player in the development of nuclear rockets. A significant milestone was achieved in 1969 with the successful demonstration of Phoebus 2A. This rocket engine, designed for operation at 5,000 MW, but limited to ~4100 MW by an undercooled pressure vessel clamp, produced about 250,000-lb thrust with an exit gas temperature of ~3,000 °K (~3,500°F or ~2,000°C) resulting in a specific impulse, Isp, of ~900-950 s. Liquid hydrogen coolant/propellant, with a density of 0.07 g/cm3 (4.4 lbs/ft3) was pumped through the reactor at ~350 lbs/s (~80 ft3/s). This required a pump operating at ~3,500 rpm that would not raise the temperature of the liquid hydrogen at -253°C due to friction resulting in cavitation and possible destruction of the pump itself. The program involved a massive effort of materials development, high-and-low temperature physics, strength of materials, nuclear reactor design, and facilities design and construction.Several reasons are given for the demise of the program. I believe that the successful manned moon mission of 1969 that satisfied President Kennedy’s goal, stated in his inaugural address, for a manned moon mission in the decade of the sixties, resulted in a major shift of priorities. The termination of the program was traumatic. On January 9, 1973 the staff at Los Alamos working on the Rover Program were directed to prepare their resumes. I know the date well – my son was born on January 9, 1973! The progress throughout the program was so rapid that very few formal reports were written. Observations were generally made by individuals in informal group Progress Reports. Entire file cabinets of documents from several organizations, both inside and outside of the laboratory, were declassified, if necessary, and destroyed. Diagnostic hardware and equipment was destroyed, sent to salvage, or buried at the Nevada Test Site or at TA-54. This presentation will include details of several aspects of the Rover Program and be illustrated with photographs and videos rescued from the 16 mm film archives. The Rover Program was successful. However, its very success forced a decision of what to do now – and the country was not ready, and possibly could not justify or afford, ambitious manned space missions to the moon and beyond. Just perhaps in your lifetimes – but not mine – you will experience a resurrection of the technology that makes ambitious space missions possible. Links: |
The P/T Colloquium is
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