Saturday, May 12, 2007

The Wonder of NASA

NASA makes me wonder sometimes. I'm just now reading Bill Harwood's (CBS News) excellent space update email (highly recommended), and there are a couple things in there that just make me laugh out loud.

I have the utmost of respect for NASA, and I love following it's doings and workings, but sometimes the way they do things or put things just puts a huge smile on my face.

Some examples:
The shuttle Atlantis' hail-damaged external fuel tank has been repaired, NASA officials said today, clearing the shuttle for rollout to launch pad 39A next week. ... Rollout to the launch pad is scheduled to begin at 4 a.m. on Wednesday, May 16.
Why so early? What's the matter with 8 a.m.? Maybe NASA just has a lot of morning people. That just made me laugh.
NASA managers had hoped to launch Atlantis on mission STS-117, the first of five planned 2007 shuttle flights, March 15. But during a freak storm that thundered over the launch pad on Feb. 26, the shuttle's external tank was blasted by hail, suffering thousands of pits and gouges in its foam insulation. Wind gusts reached 62 knots and hail up to 1.5 inches in diameter was found at the pad.

... Of that total, between 1,400 and 1,500 were tightly clustered at the very tip of the tank near its carbon composite nose cap. Rather than make individual repairs in that area, a broad area of foam was sanded down to eliminate the pits and then filled in with sprayed-on insulation. That fresh insulation was then milled to the proper slope and to an acceptable thickness by a cleverly engineered "pencil sharpener" device that rotated about the top of the tank.
Can you imagine a pencil sharpener the size of the shuttle's external tank?! I can just see the headline now: NASA Fixes Shuttle with World's Largest Pencil Sharpener!

Again, really quite impressive. And I understand how scientists come up with these analogies. It's just striking me as quite humorous this morning. :)
To make sure the required repairs could stand up to the aerodynamic and thermal rigors of launch, engineers re-assessed the flight performance of past PDL repairs, simulated damage sites using steel balls to impart hail-like crush forces and then subjected repairs to a hot-gas wind tunnel at Marshall.
In other words, the job of the guys at Huntsville is to re-create (a) the hailstorm, and then (b) liftoff conditions.
During the first 110 seconds of ascent, atmospheric friction raises the tank's temperature to some 650 degrees in some places and heating continues throughout the climb to space. Along with thermal concerns, foam debris falling off the tank could threaten a Columbia-type impact to Atlantis' heat shield.

"As you accelerate this vehicle supersonically in the lower atmosphere, you build up quite a bit of heat, several hundred degrees," Hale said. "But you increase in temperature all the way up and even in second stage, when you are almost at orbital altitudes, you continue to put heat in.
I knew there was a lot of heat on re-entry, but I didn't realize there was also heat (though not nearly as much) on exiting the lower atmosphere.
The hail storm, Chapman said, "left the external tank team with a tremendous amount of work to do. This team has been essentially working 24/7 since the storm, doing engineering analysis, testing and repair of the tank. In my estimation, they have done a fantastic job. This has truly been unique. We've had hail damage before, but never to this magnitude."
Bravo to the hard workers at NASA. That's 75 days these hundreds of folks have been working on the external tank!
But Chapman cautioned that shuttle watchers should be prepared for a somewhat strange-looking tank when Atlantis heads for the pad next week. The foam used for the large-area sprays and the PDL-type repairs is a much lighter color than the insulation sprayed on at the factory.
That would be me. I'm guessing it will be reminiscent of the VAB building and the patchwork done there after the 2004 hurricanes.
Launch is targeted for 7:37:56 p.m. on June 8.

NASA plans to hold a two-day flight readiness review May 30 and 31 to assess the status of launch preparations and to set an official launch date.

Assuming a rollout to the pad on May 16, engineers will only have three contingency days between then and June 8 to deal with unexpected problems.
Countdown to launch: T-minus 27 days!

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