>
>I'd be curious, Dave, to know what the problems with
>accelerometers are that you mention.


You can read acceleration pretty easily.
SRB's are noisy, but integration solves that.
Accelerometers will show the engine burn and coast characteristics pretty
well, but they have no idea which way is up.  Unfortunately, it's not
uncommon, especially during a problem launch, for the airframe to be
horizontal at burnout, doing mach at 6' altitude.  You can have this happen
due to booster failure, fin failure, weathercocking, or a shear layer.

If we factor out the at-rest acceleration of gravity, what you expect is a
large acceleration, transiting to a surprisingly large negative
acceleration at burnout, which decays during coast to near zero. If the
flight is mostly horizontal, that zero doesn't occur!

One sensor that does not get fooled about "up" and "down" is a three axis
magnetometer.
At launch, you back up in the data till just before launch, and call that
vector "up" (or rotate it till it's conveniently 0,0,0)

Aluminum launch rod highly recommended!

--
Where's dave? http://www.findu.com/cgi-bin/find.cgi?kc6ete-9

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