NASA looking into whether ICE contributed to disaster
(Johnson Space Center, Houston-AP) -- NASA is looking into the role ice may have played in the "Columbia" disaster.
They're checking to see if the piece of foam insulation that hit the shuttle shortly after liftoff may have been weighted down with ice.
The extra weight would have made the 20-inch piece of foam more destructive than NASA ever imagined.
NASA's theory is that heavy rains in Florida in the days before the shuttle lifted from Kennedy Space Center may have somehow gotten inside the foam. The theory holds that the rainwater froze between the foam and the cold fuel tank hull, weighing down the foam.
Speculation on what caused the shuttle to disintegrate centers on possible damage to the thermal tiles on the shuttle's wing from the falling piece of foam.
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Ron Dittemore in a news conference:
RE: Ice or Icey Insulation hitting wing upon launch
"We talked about ice. Ice can form on the tank, given the right environmental conditions. However, we have strict criteria on allowable ice. In some cases, ice is O.K., dependent on where it is located on the tank and the thickness of the ice. In other areas of the tank, ice is completely unacceptable.
And the way we control that is to send an ice team out to the launch pad after we have loaded the propellant in the external tank, and this ice team completely inspects the external tank exterior, looking for ice, looking for sheets of ice, looking for thickness of ice.
And in each case, the ice team returns back to the launch complex and briefs the mission management team on their report. And if we believe the conditions of icing are unacceptable, then we delay, or we scrub.
So one of the main criteria for us to be go for launch is to make sure there is no unacceptable levels of ice.
A question was asked recently about the debris impact analysis that we have performed, that we preformed during the mission. I mentioned to you that we assumed a piece of debris of the size of 20 inches by 16 by 6, with a weight of about 2.67 pounds, which we believe to be a very conservative weight. And when you pick up these pieces of tile, you'll understand what I mean. But we were trying to bound our analysis, so we were very conservative on the weight.
In addition to the weight, the air velocity at 82 seconds into the flight, the local air velocity is 750 feet per second. Even though the vehicle is traveling somewhere in the neighborhood of 2,300 feet per second at this time, the local air velocity between the orbiter and the tank is around 750 feet per second. That's the transport mechanism.
In our analysis, we assumed 1,500 feet per second. So roughly, in this case, double the amount that we believe exists at the time of the debris falling off of the tank.
So to be conservative, again, we doubled the local air velocity. We were conservative on the weight of the material, and we were using a tool that we knew overpredicted damage. So it's difficult for us to believe as engineers, as management and as a team that this particular piece of foam, debris, shedding from the tank, represented a safety of flight issue.
So we're looking somewhere else."
Excerpt from NASA News Conference. . .more excerpted transcripts located here: nytimes.com
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Here is what I have been writing about the ICE Theory:
Feb 4: Message 18535809
Feb 1: Message 18523455
While the Purple Streak theory is fascinating, I am sticking with the theory that ice dislodged from the fuel tanks, striking both the critical leading edge tiles and a number of additional tiles on the left wing. . . and that this action doomed Columbia, since re-entry would have been impossible.
Rande Is |
