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Shuttle Launch Pad Damaged During Discovery's Launch
pumpkinpuss writes "Launch pad 39A at the Kennedy Space Center suffered unusual damage during the shuttle Discovery's blastoff Saturday. Pictures from a NASA source show buckled concrete and numerous concrete blocks or bricks, presumably from the flame trench, littering a road behind the pad."
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The shuttle shit a brick?
Do not look into laser with remaining eye.
Given how scary space travel is, it's no surprise that the astronauts left behind a trail of bricks all over the pad.
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38A continues to beat on the ceiling with a broom and indicate that NASA should "[K]nock off that unholy racket!"
Many. It was built for the Apollo program, first used in 1967 - and handled almost all of the Saturn V Apollo launches bar one (so ~ 16). After that it has, along with 39B been handling Shuttle launches - and so presumably taken close to, if not more than 50% of them (so around 60+). Hence we could be looking at around 70-80 launches - launches of the heaviest kind.
39B has already started to be refurbished for Project Constellation, launching the Ares Saturn like rockets. The plan is that 39A will follow suit after the last of the space shuttle missions are finished.
about 50 meters above the launch pad.
Making things hot and cold in rapid succession can cause fatigue due to the materials expanding and contracting. Things exposed to the elements, such as this, also have to deal with moisture.
I don't know what these bricks are made of (CNN says they are special bricks but TFA says they are concrete), but I bet water was trapped in between the cracks and crevices of these bricks and then suddenly boiled when it was heated by rocket exhaust. The steam rapidly escapes from the bricks and makes the cracks a little bigger. This occurs over and over again, each time the cracks get a little bigger. Finally, the cracks become big enough that the bricks can't stand the stress anymore. They get heated one more time and explode. It only takes one brick to explode to cause a chain reaction, and wipe out a bunch of them.
This is of course, the simplest explanation. I would hope NASA would have thought of this before. It happens all of the time with the freeze and thaw cycles in highways and bridges. However, sometimes the simplest explanation is the best.
One of our competitors trademarked the term "hypothesis". From now on, we will call them "boneheaded ideas".
according to the all-knowing wiki, http://en.wikipedia.org/wiki/Launch_pad_39A/ there have been 82 launches.
Thermal cycling. Cracks can occur in many structural materials while *cooling*, not while heating. Next time try heating a piece of glassware to an unholy temperature, and then dropping it into an ice water bath.
Disregard the age of the pad; This mission was the heaviest for the shuttle. It was taken all the way to the max. Basically, this one took longer to take off, chewing away at the pad that was designed and built LONG ago to handle such loads.
It depends on your definition of "nearby".
With nearly 10 million pounds of thrust, I imagine there are still significant blast pressures on that pad even when the shuttle is a kilometer or more above it. For comparison, the blast danger area for other aircraft behind a 747 at full takeoff thrust is more than half a kilometer. If you don't believe that, there's a Top Gear episode that amply demonstrates the fact.
Random and weird software I've written.
STS-124 is carrying Kibo, making it a rather heavy liftoff. It would have taken Discovery a little longer than usual to get away from the pad, subjecting it to a longer duration acoustic/vibration environment.
Also, it wasn't that far off the pad when the bricks were flying off according to this image. (Same photo as TFA, but a little farther out)
Kurt Vonnegut: "If you can do a half-assed job of anything, you're a one-eyed man in the kingdom of the blind."
My friends own a commercial concrete contractor, and current concretes are WAY more advanced than I'd ever have thought.
These days, concrete is like any other advanced man-made composite. The knowledge about cement, water, sand and aggregate types and mixes have been refined to the nth-degree. Then start add-mixing plasticizers, hardners, cure retarders / accelerators, humidity control agents, etc.
The really advanced stuff is like epoxy. Normal concrete is ~3,000psi. My friend was pouring 12,000+ psi concrete for a large structural member in a sub-foundation. The form blew out, and concrete flowed out the hole and setup - within a few hours, even jackhammers became ineffective - it was like drilling steel. They wound up bringing in heavy demo equipment to get out what should have only taken a few men.