The next time the space shuttle flies it will carry more than 250,000 commemorative postal covers that the U.S. Postal Service will sell to stamp collectors and dealers for as much as $15 apiece.

The stamped envelopes will be placed in canisters in the cargo bay of the space shuttle Challenger when it makes its third flight into the Earth's orbit, scheduled for late August.

It will be the first time that NASA has agreed to persistent Postal Service requests that it fly into space postal covers that can be distributed to collectors.

"We have this opportunity in part because the payload we were prepared to fly will not fly until next year," Air Force Lt. Gen. James A. Abrahamson, NASA associate administrator, said in an interview.

NASA sources said that the space agency has resisted such requests from the Postal Service since 1971, when the three Apollo 15 astronauts secretly carried 100 souvenir stamped envelopes to the moon and later gave them to a German stamp dealer who sold them for $150,000. The astronauts, David R, Scott, Alfred M. Worden and James B. Irwin, were to get $21,000 of the proceeds, but decided to turn down the money.

"We can't live with that scandal forever," one NASA source said. "We decided it was time to forget it."

The envelopes will feature the patch designed for the next shuttle flight, a tribute to the space agency's 25th anniversary, and a $9.35 overnight express stamp depicting the head of an eagle with the Earth behind it. The stamp will be canceled with the date of issue, which will be the day that the shuttle launches.

The Postal Service said it has not decided on a price for the covers, but said each will sell for more than the $9.35 it charges for its overnight express delivery. Stamp dealers said that they had heard that the price for each cover would be between $12 and $15.

"There is a lot of interest among dealers and collectors in this stamp," said Bernard Steinke of the John W. Kaufman stamp-dealing firm. "First flights carrying commemorative covers have been popular all over the world ever since air mail service began back in the '20s and '30s."

The Postal Service said that distribution plans were being discussed.

One NASA source said that the Postal Service asked the space agency to carry at least 250,000 of the covers to discourage development of a black market that would drive up their price. The source said, "Any less than 250,000 would only make the covers more valuable than the Postal Service thinks they should be."