NASA says the first space shuttle to fly since the Challenger accident will be equipped with the equivalent of a fireman's pole so astronauts can slide to safety if the craft has to ditch in the ocean.

The National Aeronautics and Space Administration chose the pole escape method Thursday over an alternative that would have used rockets to propel the crew away from the shuttle Discovery in an emergency.By sliding down the pole, the astronauts would clear the shuttle's tail before parachuting into the sea.

For all the strength that allows the shuttle to withstand the buffeting that accompanies a climb or descent through the atmosphere, the vehicle probably could not survive a crash landing on the ocean.

"The telescoping pole was selected as it has shown to be safer, simpler to operate, lighter weight and easier to support than the tractor rocket system," said Arnold D. Aldrich, a top shuttle program official.

Barbara Selby, a NASA spokeswoman, said the 101/2-foot pole already is being installed in Discovery and will be ready for the first flight, scheduled for Aug. 4.

The aluminum and steel pole weighs 241 pounds, 70 pounds lighter than the rocket system.