Last year, as the Russian space station Mir suffered a fire, a collision and several major equipment failures, the top safety official for astronauts at the Johnson Space Center in Houston warned that the East-West program of shuttle visits and stays on Mir by NASA astronauts was "a disaster waiting to happen" and that the American on board the Russian outpost might soon die in a space catastrophe.

"Mir is crumbling," Col. Blaine Hammond of the Air Force told officials of the National Aeronautics and Space Administration in two blunt letters, saying he had "grave concerns" for the safety of any American astronaut on the rickety outpost.His assessment was all but ignored, Hammond said Wednesday in an interview on ABC's "Prime Time Live" and American astronauts have continued to live and work aboard Mir. Hammond left the agency early this year after concluding that his career had hit a dead end.

Hammond's letters, which he discussed in the interview, mark the first time the public has heard cries of alarm from within the normally laconic astronaut corps. The letters also provide a revealing portrait of Mir's hidden woes, including the routine leakage of large amounts of dangerous fluids that American astronauts have had to mop up.

Defending their actions, NASA officials noted that the Mir program has had no catastrophes and has continued to function relatively smoothly. Seven American astronauts have worked aboard Mir in the past three years, they noted. The last, Dr. Andrew Thomas, is scheduled to return to Earth early next month.