[AR] Re: The Laws of Motion have just changed!
- From: James Bowery <jabowery@xxxxxxxxx>
- To: arocket <arocket@xxxxxxxxxxxxx>
- Date: Sat, 16 Mar 2019 19:38:44 -0500
On Thu, Mar 14, 2019 at 10:13 PM Henry Spencer <hspencer@xxxxxxxxxxxxx>
wrote:
James Bowery <jabowery@xxxxxxxxx> wrote:
As to 70,000 RPM being a well-explored regime, you're absolutely
correct. The problem is there are a lot of variables other than
frequency that go into system behavior.
The problem is, there have been *many* high-speed rotating devices built,
covering quite a wide range of the design space. And while their behavior
certainly can be complicated, there's been nary a hint of any new physics
being required.
This isn't absolutely definitive; sometimes interesting things happen only
when details are exactly right -- resonance phenomena in particular are
often fussy. But the way to bet is that there aren't any big surprises
hiding there by now.
The excursions during failures (even though concentrated into modes)
expand the "design space" quite a bit. IIRC, this guy's device exhibited
the anomalous behavior during a failure that he, I believe, verified by
taking it apart before putting it back together for subsequent tests. He
had something like a ball bearing on the end of an arm attached at right
angles to the motor's axis to produce the vibration he was using to do
vibration isolation. It had a variable resistor to change the rate of
vibration. As he changed the rate during a stress test, it worked as
expected until the phenomenon occurred. His inspection revealed the ball
had flown loose and was being batted around the inside of the metal box
containing it at a high speed.
Now, I'm sure there have been lots of systems with loose parts that get
batted around at high rates of speed, so one would _think_ that something
like this had been observed before, but it _is_ a rather obscure part of
the "design" space that is not likely very well explored.
(Surprises for people familiar with the science and technology, that is.
Well-understood but complicated things can easily look bizarre and
inexplicable to a novice, especially one who's naively extrapolating
experience with simpler systems into a regime where complications set in.)
Yes, he may have misinterpreted the initial experience. However, when he
reportedly took it out to a playground and ran multiple tests on a fishing
line with a stopwatch and took measurements -- it was well beyond such
trivial explanation save one:
Fraud.
I admit, I do have my moments when I wonder why this guy just happened to
call in on my first day of joining a launch service company after I had
just royally pissed off NASA with the Launch Service Purchases Act of 1990.
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