A shuttle astronaut made a speedy but smooth descent from launch pad 39B Friday in the first manned run of a slidewire basket emergency escape system that could prove vital in the event of a pre-launch crisis.

With an ambulance standing by, Charles Bolden, co-pilot of the last successful shuttle mission in early January 1986, climbed into one of the escape baskets at about 2:10 p.m. and rode to the ground 195 feet below. The basket, hung under a 1,200-foot cable, hit a top speed of more than 50 mph just before hitting a net that slowed it to a stop.

"I told somebody I thought if we put our kids in there, they'd ask for their money back," Bolden said of the less-than-dramatic ride. "It wasn't a thrill ride. It was a very, very gentle ride all the way down.

"Personally, I think all of us involved feel very good about it. I think it was a very, very highly qualified success."

The test was a major milestone in a $1.5 million post-Challenger effort to beef up safety at pad 39B, where the shuttle Discovery currently is undergoing checkout prior to launch in early September.