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News Office
Massachusetts Institute of Technology

Contact:
Elizabeth Thomson, MIT News Office
(617) 258-5402, thomson{at}mit.edu 
or
Deborah Halber, MIT News Office
(617) 258-9276, dhalber{at}mit.edu

FEBRUARY 3, 2003

MIT experts reflect on shuttle tragedy
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CAMBRIDGE, Mass. -- As the nation mourned the loss of seven astronauts 
and NASA's investigation of Saturday's space shuttle disaster focuses 
on possible failure of the vehicle's thermal protection system, MIT 
experts reflected on the science, engineering and humanity behind the 
loss. 

"This is a tragedy for our nation and our community," said Professor 
Edward F. Crawley, head of MIT's Department of Aeronautics and 
Astronautics. The department held an impromptu memorial service in the 
Seamans learning laboratory in Building 33 on Monday.

"When something like this happens, we have to reflect on the 
tremendous bravery of these individuals," he said to more than 100 
people who came to share a moment of silence for the crew of the 
shuttle Columbia. Aware of the inherent risks in "sitting atop a 
controlled explosion and the fiery heat of reentry," they made the 
"ultimate sacrifice" in the name of space exploration and the quest 
for knowledge, he said.

As NASA and others investigate the cause of the disaster, MIT experts 
applied their knowledge of the space shuttle's engineering to the 
first bits of information on potential causes.

The thermal protection system -- which includes the tiles that cover 
the shuttle's surface and protect it from the fierce heat of reentry 
into the Earth's atmosphere -- is under close scrutiny.

The tiles are "a potential failure mode that NASA has been very much 
aware of from the beginning, and near the top of the list of concerns 
in the early '80s," said Charles M.  Oman, senior research engineer in 
aeronautic and astronautics.

Over the years, ideas and methods under discussion for fixing tiles in 
orbit have even included requiring crew members to replace missing or 
damaged tiles with a trowel and glue during space walks. "As NASA's 
confidence grew as missions went by, the predicted 'zipper effect' 
didn't seem to be occurring," Oman said. The zipper effect is where 
one lost tile creates a chain reaction that causes failure of 
downstream tiles in the airflow. "It creates a hot spot that melts the 
underlying aluminum structure.  It may turn out that that's what 
caused this, but we'll have to wait and see," said Oman.

Oman said that based on video from a West Coast astronomer, chunks 
were coming off the vehicle as it crossed California, which would 
support the idea that the tiles were at fault.

The loss of protective tiles from the underbelly of the space shuttle 
Columbia or even a series of cracks in the section containing the 
protective tiles due to impact of a foreign object during liftoff 
might have caused Saturday's catastrophe, according to Subra Suresh, 
head of MIT's Department of Materials Science and Engineering.

At about the point over Texas where the space shuttle disintegrated, 
it would have been exposed to the highest temperatures and thermal 
stresses of reentry, said Suresh, the Ford Professor of Engineering. 
Suresh is an expert on the materials aspects of failure.

The ceramic tiles are made of a material that is known to be resistant 
to reentry temperatures and protect the shuttle. However, said Suresh, 
if a series of tiles were damaged by a foreign object during liftoff, 
"that might have exposed the shuttle to those high temperatures, which
could have led to a catastrophic event." He cautioned that all of this 
is speculation pending further details.

Since Columbia flew 28 missions, there could also be the possibility 
of damage due to thermal fatigue. Thermal fatigue is a weakening of 
the interface between the shuttle and the tiles caused by repeated 
exposure to very high temperatures followed by thermal shock, or a 
quick cooling when the craft lands. Thermal fatigue and thermal shock, 
however, are very difficult to assess given the level of information 
available at this time, Suresh said. 

While there were no MIT alumni or experiments on this mission, Oman 
was acquainted with astronaut Laurel Clark.  Her husband, Jon Clark, 
is a flight surgeon, a colleague of Oman at the Johnson Space Center, 
where Oman conducts experiments on the human health effects of space 
travel.

"They were very much a Navy couple," Oman said. Laurel, also a flight 
surgeon, "was interested in flight safety questions. She started out 
in submarine medicine and studied how the body reacts to increased 
pressure and the closed environment of a submarine. She was also an
accomplished scuba diver.

"She applied to be an astronaut and was astonished to be selected, but 
we who knew her weren't surprised. Clearly, in terms of her 
background, she had the right stuff. She believed devoutly in the 
value of human space flight and that's her legacy," he said. She would 
not have wanted humans to be barred from space because of the Columbia
accident, Oman added. 

David W. Miller, associate professor of aeronautics and astronautics 
and director of the Space Systems Laboratory at MIT, agreed that 
humans in space are critical. "Humans in space play a very important 
role as observers in the laboratory environment of the International 
Space Station," he said. "My own terrestrial lab here has plenty of
equipment, but the best piece of 'equipment' are humans who understand 
the problem and observe what may be going wrong or right with the 
experiment." 

Miller thinks that NASA will have to think about alternative access to 
the International Space Station.  He suggested "some kind of mixed 
fleet of two parallel systems, not necessarily of equal capacity -- 
perhaps something like a Soyuz."

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