SPACE CENTER, Houston--Space shuttle Challenger Pilot Michael J. Smith exclaimed "Uh-oh!" at the moment the spacecraft exploded, and some of the crew apparently lived long enough to turn on emergency air packs, the National Aeronautics and Space Administration (NASA) said yesterday.

Smith's remark, heard on a tape of the shuttle's intercom system, was the first indication that any of the seven astronauts killed may have been aware of the January 28 disaster, the worst in the history of space exploration.

The astronauts probably survived the explosionand breakup of the shuttle orbiter and could havehad 6 to 15 seconds of "useful consciousness"inside the crew compartment after the blast, saidDr. Joseph Kerwin, an astronaut-physician whoinvestigated the cause of death for the crew.

The force of the crew compartment hitting theocean was so destructive, however, that theprecise cause of death for the crew could not bedetermined, he said.

The intercom tapes were recovered from thewreckage of the Challenger and analyzed by NASAand IBM engineers.

The tape, a transcript of which was released byNASA on yesterday, offered no verbal evidence thatany crew members other than Smith knew anythingwas abnormal prior to his single exclamation 73seconds after launch--the very second that groundcontrollers lost all communication with the craft.

Previously, the last known words from theChallenger were those heard from Commander DickScobee to ground controllers, when he responded"Roger, go at throttle up," confirming that theshuttle's main engines had been raised to fullpower.

School teacher Christa McAuliffe and missionspecialists Ronald McNair and Gregory B. Jarvisare not heard on the recording.

NASA said the three "could monitor all voiceactivity but did not make any...comments."

As recently as July 17, NASA said its reviewsof the voice tape indicated that the crew wasunaware of the events preceding the breakup of theorbiter.

NASA said yesterday, however, that furtheranalysis showed that Smith's final comment offeredthe first potential indication of crew awarenessof the accident.

Smith's exclamation could indicate "there was amoment of awareness," said Admiral Richard H.Truly, associate administrator for space flight.

Four of the air packs were recovered and threehad been turned on, with an analysis of gauges ontwo of the air packs showing threefourths toseveneighths of the air had been breathed, Kerwinsaid.

One of the air packs that had been turned onbelonged to Smith, Truly said. It was not knownwho the other two activated air packs belonged to,and the recovered air pack that was not turned onbelonged to Scobee, NASA said.

Smith and Scobee could not easily have turnedon their air packs without getting out of theirlaunch couches, Truly said.