Behind the excitement of the coming spaceflight of Senator John
Glenn is quiet apprehension about hidden dangers. Safety experts
agree that the space shuttles, like temperamental hot rods, must
run regularly or become balky and their launching crews rusty.
But the shuttles have flown little of late. So Senator Glenn's
flight is seen, at least in theory, as unusually risky. In
response, the space agency is taking precautions like having
ground crews do many more dry runs meant to sharpen their
skills. It says these rehearsals will offset any dangers, though
some private experts say the odds of disaster still might be
unusually high. ''We've been concerned,'' Dr. Seymour C. Himmel,
a senior member of NASA's Aerospace Safety Advisory Panel, said
in an interview. ''When you have a hiatus like this you have to
keep your skills honed.'' Dr. M. Granger Morgan, head of
engineering and public policy at Carnegie Mellon University,
agreed. ''There are concerns whenever an organization that has
to perform a high-reliabil