Hi Ben,
First off, great episode. I'm really liking the new format for the show and want to say keep it up. Second, I wanted to point out that for an electronic fire control system like this, it really should be a two-stage ARM-FIRE sequence. By only having the single low-side MOSFET as the primary ignitor switch, there is no fault or transient tolerance. In a MOSFET, there exists a parasitic capacitor between the Drain and Source (the Coss parameter in the datasheet) and depending on the MOSFET can be several thousand picofarads. If there is no dV/dT limit placed on the power supply voltage rail, during power-up the MOSFET can sink a large amount of current ( i = c*dV/dT) which could potentially ignite the rocket if on the launch pad. Also, it should be noted that the pull-down Gate resistor needs to be a releatively low impedance (a couple hundred ohms) to help provide transient protection.
A safer approach would be to have a seperate "Arming" switch that switches power to the ignitor MOSFET independently of the primary ignitor switch. I'm thinking something like a Key switch to enable a high-side P-Channel FET to enable/apply power to the ignitor MOSFET. See Figure 1 below.
Figure 1
R2/C1 form a dV/dT control for when key switch S1 is armed. The exact values will depend on the chosen MOSFETs Q1 and Q2. Plus the key switch will add a level of authenticity like missile silos 
.
Shawn
| Sheet1.pdf |
