Slashdot Mirror
NASA's Foam Test Offers Lesson in Kinetic Energy
Puneet submitted a followup story on the foam test that NASA conducted to get an idea of what sort of damage could be caused by foam falling off the shuttle fuel tank at launch. As it turns out: a lot.
> F = Ma
It's not really force/acceleration that's important, it's kinetic energy and momentum:
Kinetic Energy = 0.5 * mass * (velocity^2)
Momentum = mass * velocity
So a 1g spec of dirt travelling at 20,000mph has the same momentum as a 1KG block travelling at 20mph - something best avoided!
They've talked about firing foam samples at wing mockups at hundreds/thousands of miles an hour, 'cause (I think) the Shuttle was flying at that speed when it was hit. But wasn't the foam also flying at that speed? Shouldn't the actual velocity of the foam hitting the wing edge be fairly minimal?
You are probably somewhat right, the velocity of impact is something like the speed of the shuttles ascent - speed of the foams ascent. However to maintain a 500 MPH ascent requires a considerable amount of constant energy. The foam probably decelerated much quicker than you are thinking.
The videos are here (where the panel visibly ripples after the impact) and here.
The accompanying slide presentation has the details: the 1.7 pound foam block was fired at 531 mph and, where it struck a T-seal between two panels, displaced them and caused a 4/10 inch gap. This fake wing was made of fiberglass, but given the results, a test with actual shuttle wing material from the Space Shuttle Discovery is planned for today.
Here are some of the headlines from news.google.com:
Shuttle Wing Under Gun
Investigator Amazed by Shuttle Foam Force
Foam theory faces pivotal test
Tests Show Foam Causing Wing of Shuttle to Deform
Foam chunk was shuttle's undoing, tests indicate
The article says he is the Director of NASA Ames research center, not that he *is* a rocket scientist. He is not a rocket scientist. His bio (http://www.arc.nasa.gov/about_ames/hubbard.html) from NASA shows him to be a long time administrator, with his original scientific background in radiation detection materials and devices.
So will people *PLEASE* quit insulting rocket scientists.
. there used to be a sig here.....
Almost. But you converted your 200 feet into miles -- which you weren't supposed to do. Using the correct numbers, you get (733^2)/400 = 1344 = about 42 g's. Since air resistance is proportional to a (very large) velocity, that doesn't seem too farfetched.
How can we continue to believe in a just universe and freedom to eat crackers if we have no ale?
What's really funny (and what provides an additional clue that this is an urban legend that's been around the block a few times) is that in most versions of the legend, it is a group of American engineers who have to clue in their foreign counterparts (their nationality varies too) that they have to thaw the birds first. If there's one universal in comedy, though, it's making fun of foreigners.
"FDA staff reviewers expressed concern about the number of patients who were left out of the study because they died."
The insulating foam for the space shuttle that broke off and possibly destroyed the shuttle was a new formula since 1997 that has been problematic since it replaced a freon based foam. Although the freon-based foam worked better, the new foam was used instead rather than getting an exemption. So, if the foam is the root cause, it appears political correctness was more of a concern than using the best material for the job, possibly costing the lives in the process. Here's an article on the subject
Vote for Pedro
Define "more concentrated". Density of the two materials will not effect the force exerted on them if they have the same mass (unless the feathers are spread between here and low earth orbit.)
If a kilogram of bricks is put on a scale beside a kilogram of feathers on a scale, the readout from the two scales (aka, the weight) will be equal.
The metric system isn't silly with respect to mass and weight, it keeps them seperate. Kilograms are a unit of mass, and get used day to day because they more accurately reflect the common man's need for such a unit. People are generally interested in buying an AMOUNT of a material, instead of an AMOUNT THAT EXERTS A CERTAIN FORCE. Weight, on the other hand, is expressed in Newtons, and is generally used for scientific or engineering applications.
For example, if I bought a kilogram of sugar on the moon, I would be getting the same amount of sugar as if I had bought a kilogram of sugar on Earth. A pound of sugar on the moon would be five to six times as many granules of sugar as a pound of sugar on Earth, however.
I don't mean to sound like I'm flaming here or anything, but the popular confusion of mass and weight, especially in the Imperial unit system, really bothers me.