Impact of Foam Crack On Shuttle Launch Still Uncertain

A close-up image of the piece of foam that broke off from the shuttle's external fuel tank. CREDIT: NASA

This story was updated at 4:09 p.m. EDT.

CAPE CANAVERAL, Fla. - NASA managers decided Monday to continue preparing for the planned July 4^th launch of the space shuttle Discovery, even as engineers evaluate a piece of foam insulation that popped free from the spacecraft's fuel tank.

A team of engineers is poring over a small piece of foam about three inches long which cracked, then fell, from a bracket connecting a 17-inch feed line that supplies super-cold liquid oxygen to Discovery's engines from its orange external tank.

The foam piece is small, weighing just 0.0057 pounds, less than half of the upper limit - 0.013 pounds - for acceptable debris during a shuttle launch, NASA said.

"It looks like this small piece of bread crust," said John Shannon, NASA's deputy shuttle program manager, during a press briefing here at the Kennedy Space Center (KSC). "What we decided to do was continue with the plan that we were on."

That plan, Shannon said, is to complete the loading of cryogenic fuel aboard Discovery to power the spacecraft during its planned STS-121 spaceflight. Meanwhile, tank engineers will analyze whether Discovery can fly with the lost foam on July 4, or if the shuttle will require inspections and repairs at its Pad 39B launch site.

Results from that study will be presented during a Mission Management Team (MMT) meeting at 6:30 p.m. EDT (2230 GMT), which is led by Shannon, where a final decision will be made.

"Getting to it is not an issue, but it would be a schedule hit to us," said NASA launch director Michael Leinbach. "We cannot accomplish getting access to this area and also support the launch tomorrow morning. It's just not possible.

Discovery is currently scheduled to launch Tuesday at 2:37:51 p.m. EDT (1837:51 GMT) on NASA's STS-121 mission to the International Space Station. The planned spaceflight is NASA's second shuttle flight since the 2003 Columbia accident.

Shannon said Discovery's STS-121 crew has been notified of the foam concern. The mission's commander Steven Lindsey asked several questions during a short MMT meeting earlier today, with the rest of the crew briefed later, he added.

Falling foam

Fuel tank foam loss has been a great concern for NASA since the loss of the space shuttle Columbia, which suffered a heat shield breach by a chunk of the insulation and was destroyed during reentry - its seven-astronaut crew lost - on Feb. 1, 2003.

Since then NASA engineers worked to streamline the amount of foam on shuttle fuel tanks, replacing some insulation with heaters after the Columbia accident and removing one large section altogether after the 2005 launch of Discovery's STS-114 mission.

The piece of foam found by inspectors Monday fell from the topmost of a series of brackets connecting a liquid oxygen feedline to Discovery's external tank. That top bracket is just above and to the right of the bipod fitting that mates Discovery to its fuel tank.

"It looks like it just came off all in one nice piece from the crack," Shannon said.

By NASA's current understanding, Sunday rain showers - which led to that day's launch scrub - led to condensation on a bracket joint that froze into ice from the super-cold liquid oxygen inside the nearby feedline.

That ice later pinched into the surrounding foam as Discovery's external tank warmed and expanded, a normal occurrence as engineers emptied the 526,000 gallon vessel of its super-chilled liquid oxygen and liquid hydrogen.

John Chapman, NASA's external tank project manager, said inspectors discovered the crack during a routine examination conducted after every launch scrub.

The piece fell sometime during that three-hour inspection, and was seen by engineers as they moved the protective Rotating Service Structure into place around Discovery, he said.

Current concerns

NASA officials said that the liberated piece of tank foam seen today could not have damaged Discovery's heat shield during a launch.

"It would not have been an issue," Shannon said. "It is less than half the size that we think can cause damage to the orbiter."

Shuttle managers don't believe the foam loss will impact the ability of Discovery's fuel tank to withstand the heating stresses it will experience during launch. Analysis is still underway to determine whether any other cracks or damage are afflicting tank bracket.

The potential of ice to form over the area exposed by the foam loss is also a concern, since major foam loss or ice debris could be a hazard for the black, heat-resistant tiles lining Discovery's belly.

"I do know that we have more insulation in this area than we absolutely needed," Chapman said, adding that analysis is underway to evaluate the ice concern. "I expect that that analysis will show [we're] good."

NASA's STS-121 MMT meeting will meet at 6:30 p.m. EDT (2230 GMT) today. The results of that meeting are expected to be released later this evening.

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