Work to ready the shuttle Discovery for its Fourth of July trip to the launch pad was on track Saturday, a move that will come none too soon for 26-year-old Dan Drake.

Drake will be at the controls of Discovery's squat 6-million-pound crawler-transporter at one minute past midnight Sunday when he is scheduled to begin the shuttle's glacial 4.2-mile trip to launch pad 39B."There's a little extra pride there, it being on the Fourth," the Lockheed crawler driver said in an interview. "It's kind of like a flag waving deal. You know, we've been sitting here for 21/2 years waiting to do this again, and everybody's been kind of pushing to get it done.

"We think we should have done it a little sooner. But I think it's great that it's going on the Fourth."

Discovery, scheduled for launch on the first post-Challenger mission in early September, is mounted on a mobile launch platform in the Vehicle Assembly Building at the Kennedy Space Center where engineers are going through final tests to verify connections between the shuttle and its various components.

A NASA spokeswoman said Saturday the work was on track for an on-time roll-out and a Fourth of July trip to the launch pad, the first operational shuttle roll- out since the ill-fated Challenger made its final trip to launch pad 39B on Dec. 22, 1985.

"The weather looks OK for Sunday midnight," said Lisa Malone. "That's the best time of the day to go because you've got less chance for lightning and rain."

The shuttle and its mobile launch platform weigh about 11 million pounds. To get the assembly to the pad, NASA uses one of two crawler transporters built in the early 1960s to carry Saturn 5 moon rockets to the launch pad. The giant machines were modified for the shuttle program.

Drake, who enjoys telling people he is only two years older than the crawlers he drives, is a veteran of more than a dozen shuttle roll-outs, and he clearly enjoys his work.