Maximum G's.

[Maxter]

I am currently working on a project that sim's at around 200 g's.
What are the practical limits of the various electronics? I'm not worried about the airframe....all aerospace quality carbon.
How would you protect them? What batteries have you used? Commercial dual deploy computers vs Eggtimers etc. GPS units?
What is the maximum you have flown?
Pictures and data would be a great help.

Thanks!

 

[Cl(VII)]

There was a project in the 200 G range that was widely discussed in this thread: https://www.rocketryforum.com/showthread.php?44148-Disappearing-Act-Minimum-mass-I1299-rocket

I don't believe the OP is around here anymore. I haven't gone much over 60-70 Gs myself, and haven't had any problems with Egg things or commercial stuff. Just support any wires by lashing them to something fixed with tape or zipties. 200 Gs is a different beast obviously. Lots of small things get real "heavy" at 200 Gs.

 

[cerving]

Tie everything down securely for sure. Don't use 9V batteries, and tape all of your connectors together before securing them (you should be doing this on all flights anyway...). For an Eggfinder, I strongly recommend running a bead of epoxy between the bottom of the little brown GPS patch antenna and the metal can that it sits on, using RocketPoxy, West, Aeropoxy, or a similar industrial grade epoxy.

I'd love to hear what rocket/motor you're using to hit 200 G's, and what your anticipated altitude is. 200 G's ain't easy to do...

 

[markkoelsch]

200g is really out there. I think it was Mike Fischer who has done something in that acceleration range. As I recall, he took out a carbon fiber airframe, and ended up going to aluminum airframe.

You will lose GPS lock. How long it takes to reestablish lock is the question. I would include some type of RDF transmitter.

Mounting the electronics is an issue. What works for most flights may not work here. Picture the flight computer or battery breaking free and being broken by the acceleration.


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[ksaves2]

200g is really out there. I think it was Mike Fischer who has done something in that acceleration range. As I recall, he took out a carbon fiber airframe, and ended up going to aluminum airframe.

You will lose GPS lock. How long it takes to reestablish lock is the question. I would include some type of RDF transmitter.

Mounting the electronics is an issue. What works for most flights may not work here. Picture the flight computer or battery breaking free and being broken by the acceleration.


Sent from my iPad using Rocketry Forum

Ditto, Folks report that discrete components get ripped right off the boards. I've heard of (but not seen) electronics boards potted entirely in epoxy. Surface mount stuff I believe with their lower mass
is an advantage here. If you notice spec sheets most GPS chipsets don't guarantee anything above 4G's! and of course there are the speed limits imposed on the GPS units in and of themselves.
Keith Packard from Altus Metrum one time mentioned that the Doppler effect also has an effect on the GPS as far as position decoding is concerned. I didn't realize that but it makes sense.
Yeah, I've used J&B to secure EggFinders and Proline 4500 too. Good luck. Kurt

 

[OverTheTop]

Keith Packard from Altus Metrum one time mentioned that the Doppler effect also has an effect on the GPS as far as position decoding is concerned.

Not sure of the exact numbers but I suspect Doppler effect would be greater variation on the Tx side, from the satellites, rather than on the ground side Rx (rocket). The satellite velocities would make far more impact on that figure than our boost velocity, even taking into account geometries.

 

[Maxter]

Thanks for the reply's. I'm still in design stage, will be using an ex motor, and will work up to maximum limits. I've got several other projects to finish first.

 

[OverTheTop]

Don't forget you can glue down the wires to the sled using something like Loctite 401 CA adhesive. Really an easy way to stop them flapping around. Does not need to be a continuous bead, just stitched at relevant intervals and corners.