On the face of it, nuclear power for space vehicles has a lot going for it. The National Aeronautics and Space Administration already uses nuclear power for deep space vehicles not likely to get enough power from solar arrays for on-board gear. The Soviets do, too. And the efficiency of nuclear rockets would be more than twice as great as chemical-fueled rockets. So it is not surprising that in June a panel of experts led by former astronaut Thomas Stafford urged NASA to complete a technical evaluation of nuclear engines.
Applying this reasoning to the nuclear engines reportedly described in a Pentagon study of potential next-generation ballistic missiles, however, the concerns multiply. The proposed Light Strategic Missiles, powered by nuclear-heated ammonia, would replace the existing missiles in U.S. silos as they are retired early in the next century. Smaller but more potent than conventional rockets, light missiles could better survive a first-strike attack.
The Federation of American Scientists, which opposes orbiting reactors, brought the study and its proposals to light. The scientists, worried that the higher-thrust nuclear rockets could boost the number of warheads a missile could carry, noted also the risk of polluting the atmosphere during the testing phase of the new devices.
The rockets would have two stages. A chemical first stage would loft the missile to the upper atmosphere; then a reactor-powered upper stage would gasify ammonia to expel it from its rocket nozzle. Here's the kicker: once the upper stage ran out of ammonia, the proposal is to simply withdraw the reactor control rods, letting it go critical. Poof! No large debris.
That's not to say no debris will exist. The weapons-masters think the radioactive fallout produced, most of it highly radioactive materials with short half-lives, will not last long in the atmosphere. What if they're wrong? After the fact would be much too late to find out.
There are many safety concerns to be raised about scattering a bunch of controlled nuclear bombs across the Great Plains to loft other bombs into the sky, but the idea of intentionally exploding some in the air during trials beforehand is likely to deal this plan a fatal blow. Immediate objections should come over the electromatic pulse from such blasts. That could disrupt sensitive electronics gear over a large part of the world.
Finally, adding even more nuclear warheads to the arsenal, at a time the major powers are at last achieving success in cutting the warheads already in existence, is a bad idea. It took too long to persuade such non-nuclear club members as South Africa, thought to be hiding nuclear capability, to support non-proliferation. What the world doesn't need now are more new missiles.