Altimeter MOSFET deployment switches turning on when power is applied

[rocket_troy]

If you limit the current at the FET through gate voltage control, the FET will have to dissipate the power. This would be ok for a 1 sec fire command (probably)
For your solenoid driver application, you'd have been better fully driving the FET in PWM mode(not limiting the gate voltage) and having a capacitor across the solenoid to do a basic D-A conversion at the coil and reduce the voltage. ( don't forget a good diode across the coil for back emf) PWM at 100Hz should work well-ish. That will reduce your FET losses. My go-to FET is the IRFZ44N.
50 Volts 50Amps TO220 package. There is also a Logic driven version of it that's happy to be driven by 5v logic. IRFZ44NPBF I can send you down a couple if you want to have a go.

Yeah, I finished up settling for the old RC arrangement. It was a toss up between that and going down the PWM route, but I just didn't have enough experience with PWM to feel comfortable driving heavy solenoids with it. I've controlled RC servos with it from micros, but that's minor league stuff in comparison I'd imagine.

TP