Larger and more efficient than the F-1 engine that powered the Saturn V to the Moon, the Aerojet M-1 was the largest and most powerful liquid-hydrogen-fueled liquid-fuel rocket engine to be designed and component-tested. The M-1 offered a baseline thrust of 6.67 MN, 1.5 million lbf, and 8 MN, 1.8 million lbf, as its immediate growth target.

Why Built The AeroJet M-1?

The AeroJet M-1 Rocket Engine was designed at a time when NASA was looking at the possibility of manned missions to Mars in the 1960s. Therefore, the need was for a booster capable of lifting over 1 million pounds of payload into orbit.

How It Works

The M-1 used the gas-generator cycle, burning some of its liquid hydrogen and oxygen in a small combustor to provide hot gases for running the fuel pumps. The hydrogen and oxygen turbopumps were completely separate, each having their own turbine; whereas the alternative was to run both off a common power shaft. The hydrogen pumps produced 75,000 horsepower and oxygen pumps produced 27,000 h, 20,000 kW, of power.

Rather than having a gas-generator engine dump the exhaust from the turbines overboard, the M-1 took the exhaust which was relatively cool and directed it cooling pipes on the lower portion of the engine skirt. This meant that liquid hydrogen was needed for cooling only on the high-heat areas of the engine, the combustion chamber, nozzle and upper part of the skirt, reducing plumbing complexity considerably. The gas entered the skirt area at about 700 °F (371 °C), heating to about 1,000 °F (538 °C) before being dumped through a series of small nozzles at the end of the skirt. The exhaust added 28,000 lbf (120 kN) of thrust.

The engine was started by rotating the pumps to operating speed using helium gas stored in a separate high-pressure container. This started the fuel flow into the main engine and gas generator. The main engine was ignited by a spray of sparks directed into the combustion chamber from a pyrotechnic device. Shutdown was achieved by simply turning off the fuel flow to the gas generator, allowing the pumps to slow down on their own.

Over the three year lifespan of the project, the use of separate turbopumps and other components allowed the M-1 to be built and tested with my different configurations. The project saw a total of eight combustion chambers were built, two were uncooled test units, eleven gas generators, four oxygen pumps, as well as four hydrogen pumps that were in the process of being complete.

Item History

AThat booster was to be the Nova, and it was to be powered by multiple engines each producing 1.5 million pounds of thrust. Aerojet General designed the M-1 engine to meet this challenge. Using liquid hydrogen and liquid oxygen for fuel, the M-1 was the largest rocket engine ever designed, but it never got past component testing before being cancelled in 1966. The M-1 components on display are on loan from the National Air & Space Museum.

By 1966 it was clear that present funding levels for NASA would not be maintained in the post-Apollo era. The Nova design studies ended that year, and the M-1 along with it. The last M-1 contract expired on August 24, 1965, although testing continued on existing funds until August 1966. Studies on the J-2T ended at the same time. Although the HG-3 was never built, its design formed the basis for the Space Shuttle Main Engine.

References And Further Reading

http://www.astronautix.com/m/m-1.html

https://airandspace.si.edu/collection-objects/aerojet-general-m-1-engine-reports-1962-1968