The message from the Russian Space Agency to NASA was clear Sunday: No way can your leaking shuttle come near our Mir.
With time running out, NASA ordered Discovery’s astronauts to repeatedly shut down and repressurize a leaking jet in a long-shot effort to stop the drainage and permit a close encounter today with Russia’s orbiting Mir station. It didn’t work.
The thruster was still leaking a trail of icy fuel when the crew awoke early today, about 700 miles and 13 hours before the scheduled meeting.
Russian officials insist that, unless the steering jet stops spewing fuel, Discovery must stay at least 400 feet from Mir - 365 feet farther than planned. They fear the small chunks of frozen propellant might damage critical optical sensors on a Soyuz capsule attached to the station and needed by the three Mir cosmonauts to return to Earth next month.
Mission operations director Randy Stone said National Aeronautics and Space Administration engineers believe the leaking nitrogen tetroxide would not attach to anything and poses no danger.
But the Russians aren’t convinced, “and it’s their call,” he said.
“They don’t fully understand all of the capabilities of our vehicle. … It’s mostly just the very methodical and conservative engineering approach that they take to things when they don’t have a full knowledge of the system,” Stone said.
“It’s probably the same approach that I would take if I were on the other side,” he said.
The original plan called for Discovery and its crew of six to fly within 35 feet of the station as a dress rehearsal for the first shuttle-Mir docking in June.
NASA wanted to see how well the shuttle handled next to a 100-ton station and test navigation and communication systems.
“Obviously, the closer we can get the better it will be,” said Discovery pilot Eileen Collins. “But even if we only go to 1,000 feet … we will still be getting a lot of good information.”
At the end of his workday, shuttle commander James Wetherbee thanked flight controllers for all their hard work.
“You all know how much I would like to approach to 10 meters (33 feet) because I think it’s valuable. However, if we can’t then we’re confident … it’s the right answer,” he said.
Months before the mission, the U.S. and Russian space agencies agreed that Discovery would forgo the close encounter if any one of seven critical steering thrusters failed.
One of those key thrusters began leaking Saturday, but the five Americans and one Russian aboard Discovery stopped the seepage by turning the jet off and repressurizing it.
They tried the same thing Sunday on the thruster that began leaking shortly after Friday’s liftoff, but to no avail.
Later, they reduced the pressure even more in a last-ditch attempt to eliminate contaminants and thereby close that jet’s valve.
Again, no luck.
While the leaking jet is not crucial for a close approach to Mir, it’s linked to two other jets, one of which is.
To turn off one jet in the cluster knocks out all three.
Stone said if the leak continues - and it probably will - all three jets in that cluster would be shut off, thus eliminating the leak but keeping Discovery at a distance of 400 feet.
NASA could wait until early this afternoon when Discovery is 400 feet from Mir to make that decision, because the approach is the same whether the shuttle zooms in close or hovers at a distance. Most likely, a decision would come earlier in the day.
“I hope we’re not still debating it at 400 feet,” Stone said.
He added that NASA had not given up yet on the close approach.
If this were the June docking mission, the linkup would proceed as planned despite a leaking shuttle jet because of the crucial need to switch Mir crews, Stone said.
Seven Atlantis-Mir dockings are planned through 1997.
After that, NASA plans to start building an international space station with Russia and other countries.