I built a number of these things in my youth, timer based and so on. Th wireless and pi are of course unnecessary, as was the digital countdown display I used in my youth.
The big thing that kills these attempts is the power to the ignitor. Ignitors need a lot more power than just 2-4a. While that will do it - eventually - it takes time for the wire to heat up enough to ignight the ground up match heads or whatever they coat it with. SO you have this elaborate countdown - in your case run by the pi - it gets to zero - then nothing happens for 15 seconds while the ignitor heats up and eventually ignites. Quite a letdown. What I found worked was running very thick short cables from a car battery next to the rocket to alligator clips on the ignitor and a massive relay. You want the ability to dump 100A into the ignitor for that 300-500 ms so that there's no heatup period. In fact, we got it to where we could just use plain old thin bent copper wire, forget the ignitor completely the wire would glow cherry red and ignite the engine. Ted -----Original Message----- From: PLUG <[email protected]> On Behalf Of Mark Phillips Sent: Sunday, December 24, 2023 11:59 AM To: Portland Linux Users Group <[email protected]> Subject: [PLUG] Looking for some WiFi AP Security Advice I am working on a project and need some security advice. The project is a wireless model rocket launcher. It consists of a Raspberry Pi 2 W (Debian Buster) connected to a daughter board with circuitry to control the current to ignite the igniter, a TP-Link Wifi AP, and a cell phone. There is a web site (apache and flask) running on the Pi that allows the user to control the circuits on the daughter board to launch the rocket. The typical location for launching the rockets is in a large field far from any buildings or trees. Typically, there is no WiFi Internet connectivity and cell service is problematical. There are quite a few people attending the launch. There are also times when this launcher will be used in a more urban environment (like a high school field), so there may be WiFi and cell access to the Internet. I want to make the system "unattractive" to the high school students or anyone else who thinks it would be cool to hack the launcher during a launch. I want to set up some sort of secure connection between the cell phone and the web site running on the Pi. My main concern is an attacker connecting to the web site and igniting the rocket while the user is connecting the wires to the igniter. Model rocket motors generate an exhaust gas with a temperature of ~3,000 F. Also, the igniter needs 2-4 A dc for 300 - 500 msec to ignite the rocket motor. I have put these security layers in place. 1. 16 character password to access the WiFi AP network 2. MAC address filtering on the WiFi AP 3. Self signed SSL cert for the web site 4. 16 character password to access the web site 5. Standard flask cookie security for CSRF 6. 8 character code to enable the launcher (the equivalent to a physical launch key) 7. A physical switch on the launcher that disables the ignition circuit - for use when attaching the igniter leads to the rocket engine. However, there is no guarantee that the user will use this switch everytime he/she loads a new rocket on the launcher. There is a timer attached to the switch so that when the switch is put in the "on" position, the igniter circuit will not be enabled for another 10 seconds...enough time to run like h*ll away from the launcher....;) I am not a security guru, so I am not really sure what my options are. Do you have any other suggestions on how I can make this system more secure? Am I doing anything that is unnecessary? Thanks! Mark
