|The first space shuttle since the February
2003 Columbia disaster is set to take off in mid-July with a seven-member
crew headed for the International Space Station and dozens of upgrades
meant to ensure they complete the mission safely.
Discovery launches within the July 13-31 window from Cape Canaveral,
Fla., its enhanced safety measures will include a new external
fuel tank designed to keep foam pieces of any significant size
from breaking off and possibly seriously damaging the shuttle.
Foam debris was determined to have caused of the Columbia accident.
During liftoff on Jan. 16, 2003, a briefcase-sized chunk of foam
pealed off the external fuel tank and punched a hole in the protective
heat shield on Columbia's left wing.
As the orbiter maneuvered toward Earth on Feb. 1 after its two-week
scientific mission, hot gases generated during re-entry seeped
through the hole in the wing, melted the aluminum structure underneath
and caused the shuttle to destabilize and disintegrate in the
skies above Texas, killing all seven astronauts aboard.
The investigation into Columbia's demise was triggered that day
-- a mechanism put in place after the Challenger explosion in
And in the summer of 2003, the Columbia Accident Investigation
Board declared the cause of the accident the foam strike. The
CAIB gave the National Aeronautics and Space Administration a
series of benchmarks it had to meet before launching another shuttle.
The board's 15 return-to-flight recommendations included mechanical
safety upgrades and procedures, but also changes in the NASA environment
to foster communication among the agency's ranks.
here for the full investigation report.)
independent board, called the Return-to-Flight Task Group, led
by retired Air Force Lt. Gen. Thomas Stafford and former astronaut
Richard Covey, monitored NASA's compliance with the CAIB recommendations.
The panel, made up of members from industry, academia and the
government, visited NASA sites and contractor facilities, conducted
interviews, collected information from outside experts, attended
NASA meetings and observed NASA tests to conduct its reviews,
according to the panel's spokesman Dave Drachlis.
The eventual retirement of the space shuttle, set for 2010 under
President George W. Bush's directive, had little impact on the
task group's assessment activities, which focused on NASA's compliance
to the CAIB report, Drachlis said.
The task group determined at its last meeting on June 27, 2005
that NASA had met all but three of the recommendations: eliminating
the chance that foam and ice could break off the external tank
and damage the orbiter, making the shuttle more resilient to debris
hits, and coming up with a practical way astronauts could fix
the heat shield in orbit.
Although NASA hadn't reached full compliance in its efforts to
address those critical safety needs, the task force still deemed
the shuttle ready to return to use.
"We feel that it is a safe vehicle to fly," panel member
Joseph Cuzzupoli said.
Both the CAIB and oversight panel emphasized that risk can never
be eliminated. "We have often heard the safest shuttle is
one that never leaves the ground," the Return-to-Flight Task
Group wrote in its Jan. 28, 2005 report.
The Columbia Accident Investigation Board found NASA's culture
to be as much responsible for the shuttle disaster as technical
Chairman retired Navy Adm. Hal Gehman said in a NewsHour interview
when the board's final report came out in August 2003 that NASA
had emphasized cost constraints and sticking to schedules over
not just safety, but research and development as well.
"As that process kind of morphed itself over the years,
questions like why is this happening and this is a violation of
our rules but should we continue to live with it, those questions
aren't even asked anymore," Gehman said. "Instead questions
like are you going to make the schedule and can you get the cost
controls -- and those are the kinds of questions that will get
here for the full interview with Gehman.)
In response, NASA promised to create a culture that fostered
communication, encouraged employee ownership over work, ensured
procedures are fully understood and followed, and integrating
checks and balances of technical and safety standards.
The long-term cultural changes that the space agency needed to
make did not have to be completed, just plotted out, before the
next shuttle launch.
According to Return-to-Flight (RTF) spokesman Drachlis, "The
CAIB realized that cultural changes occur over time and did not
specifically address cultural changes in its RTF recommendations.
"They did, however, recommend organizational changes that
might begin to drive behavioral changes that could eventually
affect culture over the long term," he said. "The CAIB
expectation was that a plan for those organizational changes would
be in place prior to the next space shuttle flight. In fact, most
of the organizational changes have been or are in the process
of being implemented."
Redesigned fuel tank
One of the main modifications necessary before the space shuttle
could fly again was the creation of an external fuel tank that
would not shed its foam insulation on lift-off. In January 2005,
NASA rolled out its new tank.
However, subsequent engineering tests showed the shuttle could
still be vulnerable to ice breaking off the external fuel tank,
so program managers at NASA delayed the shuttle's target launch
Although the oversight panel said NASA fell short of eliminating
the risk of falling foam, NASA Administrator Michael Griffin announced
in late June 2005 that Discovery would launch as planned in July
and proceed with its mission to restock the International Space
Station and monitor and test the new safety devices.
on the new 154-foot, bullet-shaped tank proved foam chunks no
larger than .03 pounds -- about the size of two marshmallows --
would fall from the tank during shuttle launches.
"This is the safest, most reliable tank NASA has ever produced,"
said Sandy Coleman, NASA's external tank program manager, in a
telephone news conference from Marshall Space Flight Center in
Huntsville, Ala., according to the Associated Press.
The external fuel tank contains engine propellants liquid hydrogen
and oxygen, which -- in their supercooled state -- can cause ice
to form on the tank's metal skin. The foam was intended to prevent
ice from forming and breaking off, possibly injuring the orbiter.
The fuel tank, which is jettisoned 8.5 minutes into the shuttle's
flight, also no longer has two ramp-shaped wedges of foam once
placed around metal struts connecting the tank to the orbiter.
The investigation revealed it was one of these wedges of foam
that slid off the left side of the tank and crashed into Columbia's
Instead, the tank now has electric heaters to prevent ice formations
and a video camera to monitor the tank during launch. NASA now
has one person spray the foam on the tank while another person
watches, along with a videotape and high-fidelity mockup to check
the procedure, said Neil Otte, NASA's chief engineer for the external
tank, reported the Washington Post.
Additional safety measures
Another requirement in the resumption of shuttle flights is the
ability of astronauts to repair damage to the orbiter in space.
Discovery's astronauts plan to test two methods of repairing
the reinforced carbon-carbon heat shield -- with a caulk gun to
seal small cracks and with a "wash" that acts like a
heat reflector on damaged tiles -- on test panels in the open
The crew also will test plugs for reinforced carbon-carbon by
screwing flexible patches over holes in the heat shield.
If the shuttle is damaged beyond repair, NASA must be prepared
to send a rescue mission, the recommendations say. NASA said it
would not launch a shuttle unless a second shuttle can be prepared
and launched within the timeframe that the International Space
Station can provide accommodations, including food, water and
oxygen, for the stranded crew.
In addition, NASA is using new sensors, images and cameras to
more thoroughly monitor the shuttle's heat shield, and getting
at least three useful views during liftoff to help engineers identify
any damage that would need to be repaired while the shuttle is
Additional Outside Links:
return to flight Web site
Columbia Accident Investigation
-- By Larisa Epatko, Online NewsHour