 |
 |
||
 |
|
||
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
||||||||
 |
Planetary News: Human Spaceflight (2006)Discovery Still on for July 4 Blast-Off
By A.J.S. Rayl |
|||||||
Discovery's latest (foam) wrinkle
This images shows Space Shuttle Discovery and the location of the cracked foam that was found after de-fueling Sunday night and fixed. Credit: NASA |
Discovery is "go for launch" today despite a piece of broken -- and now repaired -- foam on the shuttle's 15-story-tall external fuel tank.
If it lifts off, Discovery will become the first shuttle to launch on Independence Day.
NASA's 7-member "Ice Team" was at the launch pad, 39B, at Kennedy Space Center in Florida this morning to take the final safety survey, inspecting the exterior, fuel tank and other hardware on the shuttle for any evidence of ice or debris. All systems onboard the space shuttle were reported to be functioning normally, they said, and Discovery is ready for launch.
Currently, there is an 80-percent chance of favorable weather forecast for launch time. If the weather cooperates, Discovery will liftoff at 11:38 a.m. Pacific Daylight Time (2:38 p.m. Eastern Daylight Time) for the International Space Station (ISS).
The Mission Management Team Today's gave today's countdown the green light last night following analysis of an area of cracked insulation foam spotted on an upper section of the external tank. During a routine inspection Sunday night after the draining of the external fuel tank, which must be done if the stand-down is any longer than 24 hours, a crack was discovered in the foam near a bracket that holds the liquid oxygen feedline in place. The approximately 3-inch-long, triangular foam chunk broke away from a bracket holding a liquid-oxygen fuel line in place. Engineers think that maybe it was "pinched" off as the 0.1-inch-thick aluminum tank contracted and expanded during filling and emptying.
The engineers also said they believed that the piece of foam, had it come off during launch, would not have seriously damaged the shuttle. It would have missed the fragile leading edges of the wing and instead hit the thermal tile on the underside of the craft.
According to the official NASA statement, "[e]xtensive inspection showed that the area around the crack is intact and there is no concern for overheating around the bracket, as there is adequate foam still in place around the strut. Additional borescope inspection of the tank revealed that the metal bracket itself has no cracks."
In the three and a half years since Columbia disintegrated on reentry, NASA spent $40+ million on the investigation that determined the loss was caused by foam from the fuel tank braking off and hitting the leading edge of the left wing during lift-off, exactly as some engineers had anticipated and feared, and tens of millions more working the problem. A good part of the fix came with crews removing 35 pounds of insulating foam in two large chunks along the side of the tank that engineers decided would not endanger the launch of the shuttle.
Yet, foam remains the shuttle's greatest enemy right now and there is no way to completely stop the foam from flying off, NASA officials have said. Losing foam does not immediately signal failure and, actually, is expected, according to the official NASA documents. The size of the foam and location of the loss is what counts. The goal is to make sure only tiny "harmless" pieces known as "popcorn" break off during launch.
This latest incident comes on the heels of the controversial decision last month to launch Discovery even though the top safety officer and chief engineer voted "no go" because of the foam issue and about a year after Discovery launched the Return to Flight following the Columbia disaster and was hit by a 1-pound chunk of foam that peeled away during launch, narrowly missing the right wing, and grounding the remaining 3 spacecraft in the fleet again.
The source of last year's foam was removed, however, many engineers have urged NASA Administrator Michael Griffin to remove even more tank insulation before attempting another mission, specifically from the ice frost ramp that covers a number of brackets and lines down the side of the fuel tank. Griffin, however, said that he wants to leave them in place to see how the shuttle performs during this mission.
But at a June 16-17 flight readiness review, Bryan O'Connor, chief safety and mission assurance officer, and Chris Scolese, chief engineer, voted "no-go" for launch. At the end of the 2-day review, the other 23 shuttle management team members gave the green light for launch, outvoting the two dissenters. The majority contended that even if foam flew, it would not endanger the 7 astronauts inside. Although O'Connor and Scolese went on record as recommending a delay, they did not oppose the launch, because the space station would serve as a safe haven for the Discovery crew if their ship were damaged. "We do not believe we are risking the crew," Griffin said at a press conference following the go-for-launch decision.
Since then, Griffin has vigorously defended his decision to launch the shuttle over the dissenting objections saying that engineers have lowered the risk of damage to the spacecraft from falling fuel tank foam as much as they can.
Discovery's cracked foam
These images shows the location of the 3-inch triangular piece of cracked foam and the foam that was replaced after de-fueling Sunday night. Credit: NASA |
Meanwhile, the space agency is still deeply troubled. The dilemma that NASA confronts is that the space shuttle is to be retired, as it stands now, in 2010 -- with a growing number of vocal observers and insiders lobbying to retire it now. But the agency has a commitment to its international partners to finish the construction of the half-built space station. To accomplish that goal, NASA will have to successfully launch 16 missions in the next 4 years, or about 4 launches every year beginning next year, a highly ambitious and aggressive agenda – and probably not realistic by most veterans' reckonings.
In addition, NASA must build a replacement for the shuttle system -- the so-called Apollo on steroids CEV program is now underway -- and it is attempting to do so at a cost to science, research and exploration that many in the space community believe could deleteriously impact the future of this civilization. Drastic cutbacks have been instituted across the board and NASA's focus has become "dangerously myopic," according to Louis Friedman, executive director of The Planetary Society.
Despite the disagreements about the shuttle and the foam and the cutbacks and the CEV program, the launch today is on. Some are steadfastly confident; others are crossing their fingers.
While N. Wayne Hale Jr., manager of the Space Shuttle Program, who was promoted from deputy chief of the Flight Director Office for Shuttle Operations after the Columbia disaster, commented in past weeks that the dissenting opinions on this launch were in effect good because they indicated "every voice is heard" and that "the agency has really changed," there are others in the ranks who disagree.
The director of engineering at Johnson Space Center (JSC) Charles Camarda, a former shuttle astronaut and veteran aerospace engineer, said in an e-mail to colleagues and reporters last week, that he was taken off duty for the launch of Discovery, on which he flew last year, and was reassigned as a result of his objections to fly Discovery this time without additional work and review.
Another engineer at JSC, who requested anonymity for fear of his job, said: "Nothing has changed. NASA does a lot of insane things and not always because we don't know they're stupid, but because they are political decisions," he said. Consider the foam issue and where the tanks are built, at the Michoud Assembly Facility, in New Orleans, he said. Essentially, the tanks are built and the foam is then sprayed on at this facility (which is not a clean room) and the tanks are then stored there outdoors. "Now, if you really wanted to make sure something was going to stick, shouldn't you choose a dry environment, like Arizona, instead of Louisiana where the ambient humidity alone ensures nothing ever really dries?" [Hurricane Katrina damaged the Michoud facility and NASA's Stennis Space Center in Bay St. Louis, Mississippi, where shuttle engines are tested. NASA estimated repair and recovery costs to those facilities of about $1.1 billion last year.]
Named for two famous sailing ships commanded by Henry Hudson and James Cook, Discovery first flew in 1984. As STS 121, its mission is to deliver 5,000 pounds of supplies, including, food, water, and a new oxygen-producing machine carried in the payload bay inside the multi-purpose logistics module Leonardo, built by the Italian Space Agency. The mission will be the 115th shuttle flight and the 18th U.S. flight to the station.
Steven Lindsey commands the crew of 5 American astronauts, pilot Mark Kelly and mission specialists Michael Fossum, Lisa Nowak, Stephanie Wilson, and Piers Sellers, and Thomas Reiter, a European Space Agency astronaut who will be staying on with the Expedition 13 crew on the ISS. While docked, the STS-121 crew is tasked with testing new equipment and procedures to improve shuttle safety, as well as make repairs to the station.
[ what is this? ]