Another Shuttle? Not Now

President Reagan is near a decision on whether to build a fourth shuttle to replace the Challenger, which was destroyed last January. Though the National Aeronautics and Space Administration has urged him to say yes, the space agency has not made a persuasive case for doing so.

The entire shuttle program was predicated on the assumption that the shuttle would become America’s sole launch vehicle into space and that all conventional rockets would be phased out. The argument was that the shuttle’s reusability would make each launch so cheap that expendable rockets would not be able to compete.

For several years it has been clear that that goal would not be met, either as a financial matter or as a technological one. In the early 1980s the Air Force concluded that it needed to retain conventional rockets to be assured of being able to loft its satellites when it needed to--not when the shuttle’s on-again-off-again schedule permitted.

The space community is now in agreement that rockets are the best way to loft most satellites, and that the shuttle should be reserved for activities where the presence of human astronauts is required. Conventional rockets are relatively simple compared to the shuttle, and have a much better record of success than the spaceplane has in getting satellites into orbit. In the last few years satellite launches were kept on the shuttles only because without them there wasn’t enough for the shuttle fleet to do to keep busy.

But once the decision is made to put most satellite launches back onto rockets, be they government or commercial, important consequences follow.

The first is that the country does not need a second shuttle-launching facility at Vandenberg Air Force Base, north of Santa Barbara. Recognizing this, the Air Force will mothball its $3-billion Vandenberg shuttle facility.

The second consequence is that the country doesn’t need as many shuttles. If four orbiters were required to handle all satellite launches, surely the country can make do with three once the satellites go back onto rockets.

The space agency says that without a fourth shuttle it will have to delay the completion of the space station, which is now scheduled to go into operation in the mid-1990s. Perhaps that’s not such a bad idea, since no one has yet said what the space station is going to be used for. In any case NASA has not explained why three shuttles freed of launching satellites cannot do the work of four shuttles burdened with many of them. Remember, these spaceships don’t come cheap. NASA estimates that replacing Challenger and its assorted equipment would cost $2.8 billion. That seems a high price to pay just to have another shuttle around.

If there’s a better case to be made for replacing Challenger, NASA ought to say what it is. In the meantime, it seems wiser to spend the money building and developing conventional rockets while keeping the shuttle fleet at three.