Nerva eight years from flight
Nuclear powered rocket in test stage
JACKASS FLATS, NEV. (UPI)—The United States is moving ahead with the development of a rocket engine that harnesses nuclear energy instead of fire to propel men and machines through space with twice the efficiency of the best of today's rockets.
Tests last year in the desert, where prospector's donkeys once roamed, climaxed a research program dating back to 1955 and showed that the engine named Nerva works.
The biggest hurdle now facing the world's only known nuclear rocket project is obtaining the money needed to build and test the final flyable engine design and financing construction of a rocket stage to carry it.
David S. Gambriel, deputy manager of the Joint Space Agency Atomic Energy Commission (AEC) project, said American taxpayers already have spent $1.2 billion on the nuclear rocket program. He estimated $750 million more will be needed to get the engine qualified for flight in 1978 or 1979 and $800 million will be needed to build the stage.
The potential of atomic energy in space is virtually unlimited.
The potential of atomic energy in space is virtually unlimited.
Nerva is still eight years from flight, but already it is being planned for a number of jobs. It could ferry men and equipment between the Earth and moon at a fraction of today's costs, it could carry heavy payloads to stationary orbit high above Earth, and it could propel unmanned probes and eventually manned ships to the planets.
"It can go anywhere, far beyond the limits we can visualize right now," Gabriel said in an interview at the nuclear propulsion office in Las Vegas, 90 miles south of the desolate test site.
"It's an entirely new kind of propulsion capability."
The only similarity between today's rockets and Nerva is that they both expel hot gases to produce thrust. They go about generating the gases in completely different ways. The chemical engines used in all the big rockets of the United States, Russia and other countries produce thrust by burning two substances—oxygen or something containing oxygen and a fuel.
The nuclear engine uses the heat generated by nuclear fission in a reactor to vaporize liquid hydrogen and expel it at twice the velocity of chemical rockets.
Engineers measure rocket efficiency in terms of specific impulse—the length of time in seconds one pound of propellant will produce one pound of thrust. Nerva, using the lightest of the elements, has a specific impulse of 825 seconds. The best chemical rocket, burning the heavier mixture of oxygen and hydrogen, can generate one pound of fuel for 456 seconds.
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Thus, the nuclear engine can carry out specific missions with less propellant than a chemical rocket and therefore carry more payload at less cost per pound. Or it can go farther, faster and maneuver more with a given amount of propellant.
The hydrogen in Nerva is heated to about 4,000 degrees by passing through a reactor four feet in diameter and six feet tall not much bigger than a household hot water heater.
Development of a flyable reactor and its uranium fuel elements to withstand tremendous heat for long periods of time has been a difficult and expensive task and the effort had discouraging results in the early 1960s. Reactor endurance then was on the order of five to 10 minutes.
Last year, a ground version of the Nerve engine ran for a total of 3 hours and 48 minutes during a series of tests at the foot of the reddish Calico Mountains at the Nuclear Rocket Development Station.
It was started and stopped 28 times and it produced up to 55,000 pounds of thrust. Two charred wooden light poles remain at the concrete and aluminum test stand as the only evidence of the great heat generated.
Once the testing was completed, a heavily shielded yellow and black railroad car of the test center's "Jackass and Western" moved the Nerva engine to a radiation "hot bay" in a nearby building where the engine was remotely taken apart by men peering through a six foot glass window.
There is no radiation hazard from a nuclear engine before it has been run. But once the reactor starts the chain reaction of nuclear fission to heat the hydrogen radiation becomes a problem.
In space, a shield would protect astronauts from the engine's radiation. And after the rocket has done its job, it would be left in a sufficiently high orbit to keep it away from Earth for the 10 years that might be needed before radiation levels became harmless.
safety has been extensively studied, and he said the Nerva could be launched from Cape Kennedy with an "essentially zero probability of an accident." Even if something did go wrong, a nuclear explosion would be impossible.
Gabriel said nuclear rocket
Nerva would be used as an upper stage of a Saturn 5 rocket or it would be carried into space by an advanced launcher. It would never be operated in Earth's atmosphere.
Dr. Thomas O. Paine, administrator of the National Aeronautics and Space Administration (NASA), told Congress May 19 that Nerva in a reusable rocket stage will have a key role in the space transportation system proposed for the 1980s and beyond.
As now envisioned, the ingredients of that system will be a space shuttle powered by chemical engines to ferry men and supplies between the ground and Earth orbit, the nuclear rocket to shuttle between Earth orbit and lunar orbit and a space tug to fly between moon orbiting station and the lunar surface.
The idea behind such a plan is that space transportation costs would be greatly reduced. With lower prices the reasoning follows that more would be done in space. With more missions, the system's development costs would be amortized over a reasonable length of time.
As it now stands, however, only the Nerva engine assembly is an approved project. NASA, which is working on the engine itself, has $38 million in its budget for
the new fiscal year for the program and the AEC will provide $43 million for work on the reactor.
The Aerojet General Corp. of
Sacramento, Calif. is prime contractor on Nerva and the Westinghouse Astronuclear Laboratory of Pittsburgh is the main subcontractor for the reactor.
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