Maybe no one should have been surprised when former ace test pilot and "Right Stuff" legend Charles (Chuck) Yeager, ever the laid-back individualist, failed to show up for work with the space shuttle investigation to which President Reagan appointed him 46 days ago.

But there have been questions about Yeager's absence from the seven public hearings of the high-visibility presidential commission probing the Jan. 28 explosion of Challenger.

In a telephone interview late Wednesday from his home in California, Yeager said he has been "in touch every day" with the "very smart" commission "getting briefed and giving my opinions."

"I took the job on the condition that I honor commitments I made earlier." Those commitments included a trip abroad, from which he has just returned, he said, and a trip to New Orleans this weekend to address the Congress on Aerospace Education.

As for the critics, he chuckled, "Let 'em keep on worrying . . . . Just because I'm not there to be harassed by reporters doesn't mean I'm not involved . . . . It's not necessary for me to sit there and be seen."

Yeager reportedly was present for at least one of the commission's first closed meetings. "I don't put the highest priority on open sessions," Yeager said. "Closed, yes."

He said he plans to join activities of the commission, headed by former secretary of state William P. Rogers, as soon as his schedule permits.

Yeager, 62, a retired Air Force brigadier general, dismissed most of the criticism of the National Aeronautics and Space Administration in the news media as "Monday morning quarterbacking . . . . It gets me a little ticked off sometimes. That accident was no different from any other military or civilian aircraft accident."

He also said NASA was "not a bit premature" in including civilians such as school teacher Christa McAuliffe on shuttle crews. "McAuliffe and the congressman Rep. Bill Nelson (D-Fla.) and the senator Jake Garn (R-Utah) were trained. They knew how to go to the bathroom and eat their food in space and that's all you need to know . . . . Obviously NASA was trying to make a point that the shuttle was safe and routine."

But he added, "One thing I'd like to have seen happen is I'd like to see the guys who fly the shuttle be more involved in the design and development stages . . . . They shouldn't have to be told," for example, about design problems and temperature concerns connected with the solid-rocket booster O-rings which are the leading suspect as the cause of the accident. "They should know it because of aggressive knowledge of what's going on."

Yeager, the man who first broke the sound barrier in 1947, has in the past taken occasional potshots at NASA and the early astronauts, including Neil A. Armstrong, the first man on the moon. Armstrong is vice chairman of the Rogers commission.

In "Yeager," his best-selling autobiography published last year, he describes Armstrong as one of the arrogant civilian fliers who refused to "take any advice from a military pilot."

In an interview last year, Yeager told The Post that "it would be fun to fly that thing," referring to the shuttle. But he added, "I wouldn't particularly care about laying in the back amongst mission specialists barfin' in their beer."

But this week, he said, "Everybody's sorta forgotten the real intent of the shuttle -- to cut back on cost. The way to do that is frequent use, and that's why NASA had an aggressive launch schedule."

Commission head Rogers "is a very smart guy, running a very smart commission," Yeager said, "and it's getting to the bottom of the cause of the accident."

"The shuttle program will come out a lot better," he said, adding that there is already enough data to show what actions need to be taken. The mechanical flaw can be fixed through "redesign," he said, and NASA's apparent management and communications problems "can be straightened out in a hurry. All it takes is strong leadership."