Saturday, April 01, 2006

Why Men are not Really Necessary II continue the theme of "Are Men Necessary?" (my lovely wife, surrounded by huge hulking maleness, is not convinced), more evidence that the answer is....

Even if they are, WTF?

Here is how it went down: We (my sons and I; always their fault, not mine) were reading about the famous urban legend of the JATO rocket car, also famed Darwin Award retraction.

So...we got to thinking. We had some toy cars, and we had some rocket engines. And some of the toy cars and rocket engines were of the same RELATIVE scale as the JATO

Well, you can see for yourself: the engine is attached using a bunch of masking tape. The engine is an ESTES type B, pretty small (may be 3 Newton-seconds)

Now, there are two problems, as even a quick glance reveals. The car is large enough that there is angular force being generated around an axis that passes somewhere through the middle of the car. More simply, the engine is mounted (just as in the JATO story) in a way that might very well induce rotation as well as forward motion.

Second, the tape is a pretty half-assed attachment technique. At a minimum, we should have used duct tape, and covered the front so it couldn't scoot out from under the tape.

Well, the rotation test is the problem to be solved: would the car begin to fly, or would it spin? Spin....that's the answer. Movie evidence (a short .avi file)

A question: how big would the rocket engine have to be for its mass to dominate? It is not clear that JATO car would ever have gotten off the ground, instead of just being force nose first into a horrific forward roll on the highway.

Another test, soon: Much bigger car, D-type rocket engine (12-15 Newton-seconds). Stay tuned.

UPDATE, from NP, who being male is also unnecessary:

I have no idea if you guys watch Mythbusters or not but they did this myth in the first season. They got some pretty good data.

I will see if I can find a video but here are some links with more info on the full scale test.

Link 1

Link 2

1 comment:

Unknownprofessor said...

Ain't testosterone grand? Next thing you know you'll be trying to see how fast you can get a charcoal grill lighted with liquid oxygen.

Keep up the good work. You're reaising those boys right.