The fatal explosion of the space shuttle Challenger was an accident waiting to happen if estimates of solid rocket booster failure in a 1983 Air Force report are true, says Rep. Edward Markey, D-Mass.

In a letter to NASA sent yesterday, Markey asked the agency for its assumptions in estimating lower risks and for factors on which those assumptions were based.

The Air Force report estimated that one of the solid rocket boosters on board the space shuttle would fail in every 35 shuttle launches, The Boston Globe reported today.

The report's estimate of the likelihood of failure was about 10 times greater than the estimate officially used by the National Aeronautics and Space Administration, the newspaper said.

The report said more optimistic estimates "have no quantitative justification at all" and that this was clearly acknowledged in an earlier NASA-commissioned study on which the disputed estimates were based, the Globe said.

Markey said the Air Force report, written by Teledyne Energy Systems Inc., based its estimates on "historically documented failure rates" in solid rocket boosters used for Air Force, Navy and NASA missile programs.

If the Air Force estimates are true, they "strongly suggest that a catastrophic accident was a virual certainty and an accident waiting to happen," Markey wrote.

He said two future shuttle missions were to use plutonium-powered generators. NASA estimates there is only one chance in 100,000 of a breach in the material holding the plutonium and that a breach would have minimal effect on public health, the Globe said.

In his letter, Markey asked for estimates of the explosive force needed to breach the generator, a list of ways in which that could happen and an estimate of the explosive force on the Challenger flight.

Mark Weinberg, spokesman for the presidential commission investigating the Challenger disaster, told the Globe yesterday night he did not know whether William P. Rogers, commission chairman, had received Markey's letter.

"Any matter brought to our attention by the congressman will receive careful and thorough attention," Weinberg said.

The seven crew members of the Challenger were killed when it exploded shortly after lift-off Jan. 28, and a possible leak in the right booster is considered a possible cause.

Of 14 potentially hazardous failures that could lead to a catastrophic loss of a shuttle, failure of a solid rocket booster was the most likely to occur, according to the Air Force report.