On Fri, 4 Sep 1998, Midgley John wrote:

> 1. Simple, small, fast, (helmet-mounted?) vario - no integrated GPS!

Again, refer to my previous post, crude INS with piezo accelerometers is
the way to go.

> 2. For free-fall parachuting - you just passed 3,000' (2,000', whatever)
> going too fast - BEEP! pull now!

Same answer as above, imho, but I was under the impression that free
jumping has a limit on the speed at which you can pull with certain
umbrellas. So this is better answered by a speedometer (heated thermistor
probably). The height problem is solved by a VERY special barometric
device that is a SAFETY device and is mounted on the harness proper.

> 3. I have a friend into model rockets - how high do they get?

Almost everything that you can build @ home, including SMT, is too heavy
to ride on all but the heaviest model rockets. However, the apogee can be
read by a very small Tx that is actuated by a G-loss sensor (a switch that
closes or opens when there is no gravity). The triangulation measurement
relies on three ground stations. Contact your local Armed Forces for
suitable equipment ;)

It is possible to try to use a small strain gauge or piezo force sensor
and an integrator with a small known weight (ball bearing) plus a zero
gravity sensor to achieve this, but I suspect that it will be heavy and
complex. If the rocket does not fly vertically you also need a speedometer
that works at apogee.

Peter