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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."
Anyone know how many times launch pad 39A has been used for previous shuttle/rocket launches?
This guy's the limit!
The shuttle shit a brick?
LC39A was used the first time almost 41 years ago by Apollo 4. It was used for more than 80 launches since then. Maybe it's time to replace it?
http://en.wikipedia.org/wiki/Kennedy_Space_Center_Launch_Complex_39
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!"
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".
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.
Looks like the ISS occupants got their new toilet parts just in the nick of time.
XJS*C4JDBQADN1.NSBN3*2IDNEN*GTUBE-STANDARD-ANTI-U
Aside from the astronauts, the closest personnel to a shuttle launch are 1650 meters away. The forward fireman team are in an armored personnel carrier and dressed in reflective fire suits.
.... that'll buff right out.
You're not old until regret takes the place of your dreams.
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."
Or dip a dead rat into a vat of Liquid Nitrogen, and drop him into a watering dish!
Whee!
"Flyin' in just a sweet place,
Never been known to fail..."
the rockets are causing the damage, so the damage occurs while the rockets are nearby, right?
Well, the rocket exhaust isn't the only high-pressure fluid rushing out through the flame trench in the launch process.
The Sound Suppression Water System dumps about 300,000 gallons of water into the launchpad base and exhaust flame ports in the first 20 seconds after engine ignition, so that flow can't be good for the stability of the flame trench insulating blocks as they start to work loose.
Welcome to the Panopticon. Used to be a prison, now it's your home.
In your glassware example, you heated the piece of glassware slowly, so the thermal gradient was low. In other words the entire piece of glassware was roughly the same temperature while it was heated. When you dropped it into ice water the outside became much colder than the inside because the change in temperature was sudden. I recommend you read this article.
Remember, heat transfer is not instantaneous.
One of our competitors trademarked the term "hypothesis". From now on, we will call them "boneheaded ideas".
My bad, I didn't mean to imply cracks cannot occur while heating :) Was merely trying to dispel the myth that things only break while being heated.
Put that piece of glassware (say, a pie dish) on your stove burner, and turn the burner on high. That plate will shatter soon enough; I've seen it happen.
The meek may inherit the earth, but the strong shall take the stars.
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.
http://engineer.tamu.edu/news/story/?p_news_id=1220
No, the safety zone that that keep in back of an airliner like the 747 is not due to the engines. It is due to what they call wing tip votices. This is caused by the high presure air rolling around the ends of the wing into the low pressure zon on the top of the wing. The plane leaves a 'wake" that is like two horizonal toranados.
The 747 would have this same kind os wake evn if all four engines were shut down.
We dont know what happended to the pad yet. my guess is something to do with the combination of heat and old age.
Since I haven't seen this mentioned elsewhere, this NASA article talks about the refactory materials and specifications of the flame tunnel...
Obligatory quote:
here are some closeup photos of the pad damage.
The photos show the debris field, holes blown through the security fence by flying debris and the bricks on the walls of the flame trench ripped away. Interesting stuff.
Thats an explosion! Light bulbs are filled with an inert gas. Otherwise the filament evaporates too quickly.
Try heating a light bulb over a gas flame. A Vacuum tube will suck the melting glass envelope in, but light bulbs actually explode!
I know this because I actually have seen it tried, and the hot glass from the bulb actually burnt me badly. (Then came the research into why it exploded!)
LightBulb
I'm now confused; so did someone spit on the launch pad, drop their marbles on it, did a lightbulb shatter - or was it hit by a frozen rat?
AT&ROFLMAO
We used 4000PSI concrete when forming the promenade (walkway around ~themiddle of a stadium) of the Yale Bowl in 2006. 3000PSI is some low grade shit, we were using that on fill ins only, almost all slabs I've ever been on were 4000PSI, so I have to assume that the shuttle pads are atleast 6-7000, bare minimum.
My best guess is vibrations from launch transmitted through the ground, and possibly shifting of the soil around the flame trenches, are the culprit. I'm thinking along the lines of an undetected void forming over the decades in the soil giving way.
That gets my vote too. Anyone who has been there for a launch can tell you that the vibrations from two miles away are incredible. That and Florida is basically a large sand dune.
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