Atoms to Marsby Cyrus Ance
Atoms to Marsby Cyrus Ance
Atoms to Mars
During the cold war US Intelligence agencies were puzzled by a facility going up at the Soviet's remote atomic testing facility in Semipalatinsk, Kazakhstan. They could see sophisticated equipment and giant metal spheres being trucked in, but had no idea what was going on. Their considered opinion was that the Soviets were trying to build a particle ray gun which could shoot down incoming ICBMs. With the end of the Cold War and the collapse of the Soviet Union the facility at Semipalatinsk was high on the list of places the US wanted to get a look at. They were startled when the Russians and Kazakhs welcomed a visit, and even more startled at what they found.
The facility was part of the Soviet space program and was the development site for a nuclear rocket motor (1) designed for a mission to Mars. A rocket motor basically takes in some sort of reaction mass and gives it an enormous momentum kick. Since momentum is conserved the motor and whatever it is driving moves off in the opposite direction. The higher momentum kick the motor gives to the reaction mass the higher the acceleration the motor can achieve. The problem of a long space flight is that either it has to accelerate slowly making for a very lengthy journey, or one has to have a motor that can deliver a large acceleration. A conventional chemical fuel rocket has to carry an enormous reaction mass for a long space flight. A nuclear rocket, which has access to nuclear energy which is millions of times more abundant than chemical energy, is a major savings for a long space flight as it needs much less fuel than a chemical rocket. The fuel starts out mildly radioactive, thus there is minimal risk of a lift-off accident.
This was recognized by both the Soviets and Americans in the late 1950's and both started nuclear rocket motor programs. As early as 1959 the Soviet program was focused on a Mars mission in spacecraft called the TMK, carried by a 123 meter tall nuclear rocket called the N-1. The cost would have been enormous and it never really got off the drawing board. After the US moon landing in 1969 the Soviet Mars mission was rethought as a way to leap frog over the US program. The new idea was to assemble the TMK Mars spacecraft in orbit. The Soviets had developed the conventional Energia heavy-lift rocket and it was thought that six payloads could deliver 600 tons to earth orbit, which would be enough for the TMK. The nuclear rocket would no longer have to get the craft out of the depths of the Earth's gravity well, and was downsized and renamed Baikal-1.
Development proceeded during the 1970's. One of the key technical innovations were new nuclear fuels that were carbides of plutonium and uranium that could withstand the high temperatures and deliver maximum power. Cooling was provided by highly volatile liquid hydrogen. The combination of liquid hydrogen and the enormous temperatures of the nuclear reactor made for a dangerous testing environment, but testing was begun on a prototype nuclear motor called IRGIT in 1978. By all accounts things looked good, but in 1980 Soviet priorities shifted with the election of Ronald Reagan and a renewed arms race with the Americans. In 1987 the last Soviet leader Mikhail Gorbachev proposed a joint mission to Mars presumably on a Soviet nuclear rocket, but Reagan showed little interest. Funding for the nuclear rocket motor has been non-existent since the break up of the Soviet Union with IRGIT still needing development. The Russians and Kazakhs claim that a mission to Mars based on IRGIT would cost $14-20 billion. While NASA and the European Space Agency think the cost would be more like $100 billion.
At the moment NASA is working with Los Alamos National Lab on the development of the Safe Affordable Fission Engine (SAFE), a uranium powered nuclear rocket motor, and is unwilling to spend any money on the Russian-Kazakh motor. There are many other hurdles to overcome for a journey to Mars. It is probably technically feasible to launch a mission in 2018, the next good opportunity when Earth and Mars will be close, but today it seems unlikely that such a mission will happen unless real work starts soon. The next good opportunity would be 2032.
This column is based on an article by Richard Stone that appeared in the 15 August 2003 issue of Science.