Spinning Solar Max defies Challenger
Johnson Space Center, Houston
Astronauts in the space shuttle Challenger are having mixed success in opening a new era in Earth orbit. At this writing on Sunday, they had abandoned their first attempt to retrieve the Solar Maximum Mission satellite (Solar Max), after astronaut George D. Nelson failed to dock with it. In his futile efforts to halt the satellite's spin, Dr. Nelson actually made it spin and tumble a little faster. So satellite controllers at the Goddard Space Flight Center turned the Solar Max magnetic stabilization system back on, and the system, which grabs on to Earth's magnetic field, was trying to halt that motion.
As Goddard controllers noted, the system doesn't have much muscle and may take 10 hours to stop the spinning. This gives mission controllers and the astronauts time to assess the situation and plan a second retrieval attempt, if possible.
Meanwhile, the astronauts had been having a virtually flawless mission up to the botched Solar Max retrieval and have several important successes behind them.
These began with a perfect launch at 8:58 a.m. Eastern standard time Friday from Pad 39A at the Kennedy Space Center. This launch was on a tight schedule. Calculations by the rendezvous team, based on the latest tracking of Solar Max, allowed a launch window of only 7 minutes, 45 seconds to put Challenger on a proper rendezvous course.
On Saturday, the astronauts deployed the Long Duration Exposure Facility (LDEF) right on time at 12.26 p.m. EST. This is the largest (30 feet by 14 feet) and most massive (21,400 pounds) object the shuttle and its mechanical arm have yet handled. It was valuable practice both for handling Solar Max and for future missions when equally massive objects, such as the space telescope, will be launched.
Now LDEF is drifting along its planned orbit 288 miles high and, like the shuttle's orbit, inclined 28.5 degrees to the equator. Astronaut Joe H. Engle, commander of the mission that is to pick up LDEF some 10 to 11 months from now, says he is excited at the prospect of trying to retrieve it.
Success in retrieving Solar Max, however, is also important for this subsequent retrieval mission. It would give confidence and experience in this satellite management strategy. If the Solar Max retrieval has to be scrubbed, the LDEF retrieval plans will have to be painstakingly reviewed.
After Challenger left LDEF, mission commander Robert L. Crippen and shuttle pilot Francis R. Scobee gradually took the shuttle to higher altitudes until they made a perfect rendezvous with Solar Max Sunday morning. At this writing, they were taking up a ''station keeping'' position near the satellite while the situation was being reviewed. Among other concerns, the shuttle's attitude control fuel was running close to the ''red lines'' for this phase of the mission. These are fuel reserve limits that should not be exceeded at any point. It was unclear whether or not this would curtail a second retrieval attempt.
But mission specialists Nelson and James D. van Hoften were scheduled to have far more strenuous activity with Solar Max. Objects may be weightless in space, but they still have their mass and momentum. It takes strength to manipulate the bulky space suits. And even with the help of the jet-powered Manned Maneuvering Unit (MMU) with which Dr. Nelson tried to halt the rotation of Solar Max, carrying out this task and the repairs can be exhausting, according to Frank Cepollina, manager of the Solar Max rescue project.
He says the astronauts appear to be up to this demanding work, although at the end of each EVA (ExtraVehicular Activity) they should be be ready to rest. That is why the work has been broken into two well-separated sessions - a strategy that allows the kind of schedule slippage that now has occurred.
Indeed, Challenger started out with enough consumables on board so that the entire mission could easily be extended two days beyond the presently planned return to Cape Canaveral at 8:10 a.m. Thursday. Whether or not the attitude control fuel now is sufficient to maintain such a cushion was not known at this writing.
This mission, if fully successful, was to record several ''firsts'' for the shuttle program:
* Direct ascent to orbit without entering an intermediate parking orbit.
* The largest, most massive payload yet handled.
* Shuttle rendezvous.
* On-orbit satellite repair.
The former three bench marks have already been realized. It is only the last - and most important goal - which, at this writing, was in doubt.