Discovery that the space shuttle Challenger's nose section and crew cabin probably survived the explosion on Jan. 28 raises again the question of crew safety. But it's very likely that the addition of escape systems, such as parachutes, for the crew compartment will have to wait until the next generation of orbiters is designed.
Asked if the crew sections in the current shuttles could be equipped with parachutes, a spokesman for Rockwell International, which manufactured the shuttles, says the question is moot. The orbiters, he explains, were built to a design picked by the National Aeronautics and Space Administration (NASA) in the early 1970s. That design can't take a parachute system.
Even if it were possible to incorporate an escape system in any replacement for Challenger, if the Reagan administration asks for one, it might be unwise to do so, argues chief astronaut John Young.
He told a presidential investigating panel last week that for ``the next vehicle that we develop, there should be an escape system.''
But he advised against incorporating such a system into a fourth shuttle. ``Anytime we get multiple configurations between vehicles, we've got a systems training problem that is phenomenal. And somehow it doesn't make much sense to me that we'd end up with one vehicle that has an escape system on it and three that didn't.''
In the case of the Challenger accident, investigators conclude that a soft landing for the crew compartment would have done little good.
They believe the crew died quickly from the stresses of the initial shuttle system breakup.
Only about 14 to 16 percent of the total spacecraft system has been found. Yet chief wreckage analyst Terry J. Armentrout explained to the press Tuesday that his investigators have learned a great deal about what happened when the explosion suddenly ended Challenger's ascent to orbit.
Mr. Armentrout, director of the National Transportation Safety Board's accident investigation bureau, said the biggest surprise is the estimated small size of the explosion. He said that hydrogen and oxygen mixed and burned when the main fuel tank ruptured, producing flame and steam that gave the impression of a far larger explosion than actually occurred.
``There was evidence of an explosion visually,'' he explained, ``but the explosion of the entire shuttle is not something we're seeing. The external tank did not explode. With all its potential, it would have been a much greater fireball.''
NASA investigators say they believe that the accident developed when hot gases leaked through the lower joint of the right booster rocket and burned through the lower support that ties the booster to the external tank. The rocket then pivoted, forcing its nose into the external tank.
But the explosive force of the ensuing fireball was not enough to blow up the shuttle, Armentrout said. Instead, aerodynamic forces tore the structure apart.
The absence of burn marks, except on the tail section of the shuttle, and clean lines of breakage indicate that the nose section with crew compartment came away intact. It probably broke up when it hit the ocean after its nine-mile fall, Armentrout said.
Investigators estimate that shuttle fragments hit with speeds of between 140 and 180 miles an hour.