RSF%SU-AI@sri-unix.UUCP (12/09/83)
From: Ross Finlayson <RSF@SU-AI>
n088 1802 08 Dec 83
AM-SHUTTLE 2takes
Shuttle Lands Safely After Computer Malfunctions
By JOHN NOBLE WILFORD
c. 1983 N.Y. Times News Service
EDWARDS AIR FORCE BASE, Calif. - The space shuttle Columbia landed
safely Thursday, but almost eight hours late, after a cascade of
malfunctions struck and spread concern for the spaceship's critical
navigation system.
The six-man crew rode the winged spaceship, carrying the Spacelab,
to a landing here at 6:47 p.m., EST. This brought to a successful
conclusion the longest shuttle mission, a 10-day flight, and the
first test of the European-built Spacelab as an orbital research
facility.
At the moment of touchdown, Mission Control told the crew:
''Columbia, welcome home. Beautiful landing!''
For a time, however, there was doubt as to when the Columbia would
be coming home, Thursday or possibly a day later. The suspense built
in the morning, the result of a mysterious sequence of failures. A
thruster firing jolted the spaceship. A computer failed and then
another computer failed. These were computers handling guidance and
navigation functions. Finally, a navigation measuring system also
shut down.
After hours of trouble-shooting, Mission Control in Houston decided
it was safe to attempt the landing, even though engineers still did
not understand the source of the malfunctions.
The two pilots and four scientists aboard the Columbia remained cool
through the day. The crew members were John W. Young, Maj. Brewster
H. Shaw Jr. of the Air Force, Dr. Owen K. Garriott, Dr. Robert A.R.
Parker, Dr. Byron K. Lichtenberg and Dr. Ulf Merbold of West Germany.
This is the largest crew to fly in a spacecraft.
The descent from orbit apparently went without flaw, despite the
earlier equipment problems. But just as Young brought the nose wheels
of the Columbia to the ground, one of the suspect computers failed
again.
When the Columbia came to a stop, John Blaha, the spacecraft
communicator at Mission Control, said to the crew: ''We've got some
good news and bad news. The good news is we've got lots of beer
waiting for you. The bad news is we drank it eight hours ago.''
The spaceship was originally scheduled to land at 10:58 a.m. This
was a one-day extension of the mission decided on because of the
Columbia's smooth performance, until the final hours, and because the
spacecraft had ample reserves of fuel and oxygen.
This was the first time in nine flights that a space shuttle has
failed to land on time because of mechanical problems. The third
flight, in 1982, had to stay aloft an extra day because of a
sandstorm at its New Mexico landing base. The seventh flight, last
June, stayed up a couple of extra orbits and changed landing sites
because of rainy weather at the Kennedy Space Center in Florida.
The flight of the Columbia had been remarkably free of trouble until
the multitude of malfunctions struck Thursday morning. It was 5:13
a.m., EST. The Columbia was 155 miles up in orbit within radio range
of a tracking station at Cape Canaveral, Fla., where the shuttle was
launched Nov. 28.
An automatic firing of jet thrusters in the nose rocked the
spaceship. Nothing quite so jarring had ever occurred on a shuttle.
Young, the commander, estimated that the force was 19 or 20 times
greater than the normal force of the earth's gravity.
''It really hit the vehicle hard,'' Young reported to Mission
Control. ''It was really an impact. It was probably as high a
magnitude type thing as we have seen.''
At precisely the same time, the computer handling the spaceship's
guidance and navigation systems shut down. This was the No. 1 general
purpose computer, one of four identical computers on board that bear
the burden of controlling the craft's complex systems. Any one of the
four is capable of taking over for the others. In addition, a fifth,
independent computer is available as a backup system.
The No. 2 computer immediately took over from the troubled No. 1
computer. Five minutes later, in another thruster firing, the No. 2
computer also shut down, apparently because it became overloaded. For
about one minute, the Columbia had no computer-
operated guidance and navigation capability.
Mission control then commanded the No. 3 computer to the rescue. It
had been turned off during the problem; the No. 4 computer was
handling the spaceship's environmental control systems and other
tasks.
Flight controllers were mystified. They ordered the No. 2 computer
back on, and it worked. They tried to re-start No. 1, but it did not
work. It was presumed dead. The No. 2 computer resumed its guidance
and navigation duties, as the No. 3 computer was switched off; it
held the vital re-entry programs and had to be kept available for any
updating of those instructions.
Still, no one understood the cause and nature of the malfunctions,
or whether they were linked or independent problems. Mission Control
decided to postpone the landing. Theoretically, it would be possible
to land the shuttle without the computers but it is believed that, in
practice, a human pilot could not execute commands fast enough to
make the maneuvers necessary for re-entry into the earth's atmosphere.
''We need time to better understand the problem before we commit to
re-entry,'' Mission Control informed the crew.
Two more landing opportunities were available in the evening, at
5:17 or an orbit later at 6:47. Blaha, the spacecraft communicator at
Mission Control, asked Young if he had any preference.
''I have no druthers,'' Young replied, though he noted that the
later landing would give him a chance to take a nap. He had been up
all night at the controls.
Young had one suggestion, though. ''I recommend we close the forward
R.C.S.,'' he said, referring to the reaction control system
thrusters, ''and not run any more of those rascals.''
There was even a chance that the landing would have to be postponed
until Friday morning. NASA officials said the crew had ample fuel and
oxygen to stay in orbit at least two more days, if necessary. The
crew had run out of only one item: paper for the teleprinter that
brings them written operational instructions.
While hundreds of engineers at Houston analyzed data from the
Columbia's computers, searching for clues to the malfunctions,
another gremlin struck. This time it was one of the three inertial
measuring units that failed. This system senses the spaceship's
acceleration, position and angle of attack to provide reference data
needed by the computers in issuing commands to the propulsion system.
Shaw, who had taken over the controls while Young slept, reported at
about 9 a.m. ''fault signals'' from the inertial unit. Attempts to
re-start the system were futile.
Soon afterward, Mission Control elected to wait and attempt the
landing on the final opportunity of the day. Even though the cause of
the problems ''is not obvious with analysis,'' Blaha told the crew,
it was decided to go ahead with ''de-orbit preps.''
Flight engineers reconfigurated the computers so that if the No. 2
machine failed again, the No. 5 computer would take over immediately
and guide the ship home. The interconnections between the various
machines were also adjusted to ''minimize the impact'' on them if No.
2 should fail.
And so the crew closed the Columbia's cargo bay doors, sealing in
the Spacelab, and prepared to fire the two orbital maneuvering
engines for re-entry. Closed-circuit television from Mission Control
showed the anxiety on the faces in front of the many consoles. The
voices were calm, however, as were those of the crew of the Columbia.
In the Columbia's 166th revolution of the earth, Gary Coen , the
flight director, polled all the systems specialists in Mission
Control and, at 5:14, announced the decision to ''go'' for returning
to the earth as planned. Coen was chain-smoking.
The crew received reassuring news 15 minutes later. Blaha, the
spacecraft communicator, reported that engineers had completed their
analysis of computers 2, 3 and 4. ''The data from the memory dumps
checked out A-O.K.,'' he said.
The Columbia was out of radio contact when it began its return. At
5:52, while over the Indian Ocean southeast of India, the craft's two
orbital maneuvering engines ignited and fired two and a half minutes
to slow down the craft. The Columbia began falling out of orbit.
It would be almost 45 anxious minutes before Mission Control - or
anyone other than the six crewmen - would know if the computers were
working and navigating the Columbia through the many thruster firings
and body-flap settings necessary to keep it on course. It was out of
range of any tracking stations.
By the time word came, the Columbia had plunged into the atmosphere
over the Aleutians and was off the west coast of the United States.
Mission Control began receiving tracking data at 6:31. All was well.
As the spaceship glided over the desert here, its thrusters vented
puffs of vapor into the blue sky. A double sonic boom rocked the
desert floor. Young took over manual control and steered the craft
into a sharp left turn and made a complete circle before heading in
for the touchdown.
He brought the Columbia in at a shallower angle than before,17
degrees instead of the usual 19 degrees, because of its heavy load,
the 17-ton Spacelab.
Though the touchdown was smooth, just as the nose wheels eased onto
the desert runway the No. 2 computer had its second failure.
But the mission was over.
nyt-12-08-83 2103est
**********