Reundant Avionics for Recovery

[Raais]

Greetings,

In the last few years, I have successfully launched some rockets using COTS avionics to handle deployment and recovery. I have been using an Altiduo, but now I believe it is time to take a step forward and create my own avionics system with its own data collection and deployment system.

I would like to have both avionics, the COTS one, and my own working together to ensure redundancy in case of failure. However, I am facing some challenges and do not know how to proceed. Initially, I thought it would be as simple as using two ematches instead of one, with each connected to the two different avionics. However, I am concerned about using two ematches on the same BP hole and the potential problems it may cause (less amount of BP, not exploding both of them...). Another option is to connect both avionics to the same ematch, but that would obiously compromise the redundancy of the system, and to be honest I am sure how to connect the Altiduo and my own recovery system to the same ematch.

I am reaching out to gain different perspectives on how to implement a redundant COTS recovery system and would appreciate any ideas or experiences you could share. Thank you!

 

[AndrewGil]

When I am doing a redundant recovery solution I typically have two BP charge wells on both side of my AV bay. Meaning that each flight computer has its own BP charge, so I would have a total of 4 BP charge wells on the rocket. Usually I will make the "backup" computer have a slightly hotter BP charge then the primary, insuring a good separation. So in total I have 4 charge wells, 4 ematches, 2 batteries, and 2 flight computers, or if you want to call them altimeters.

 

[Steve Shannon]

Greetings,

In the last few years, I have successfully launched some rockets using COTS avionics to handle deployment and recovery. I have been using an Altiduo, but now I believe it is time to take a step forward and create my own avionics system with its own data collection and deployment system.

I would like to have both avionics, the COTS one, and my own working together to ensure redundancy in case of failure. However, I am facing some challenges and do not know how to proceed. Initially, I thought it would be as simple as using two ematches instead of one, with each connected to the two different avionics. However, I am concerned about using two ematches on the same BP hole and the potential problems it may cause (less amount of BP, not exploding both of them...). Another option is to connect both avionics to the same ematch, but that would obiously compromise the redundancy of the system, and to be honest I am sure how to connect the Altiduo and my own recovery system to the same ematch.

I am reaching out to gain different perspectives on how to implement a redundant COTS recovery system and would appreciate any ideas or experiences you could share. Thank you!

Do not attempt to use a single electric match. You can either use two separate charges or two ematches in the same charge. If necessary use a larger charge well to accommodate the additional match.
Personally I prefer two separate charges. I’ve seen a few instances where the first charge doesn’t quite get the chute out and the second charge does. Lots of people add a delay to one altimeter to prevent the two charges from igniting at exactly the same time and possibly over pressuring the body tube..

 

[Handeman]

The two systems should be completely separate from each other. That is the only way they are truly redundant. As @AndrewGil said, "4 charge wells, 4 ematches, 2 batteries, and 2 flight computers".
I also add about 50% more BP to the backup than the primary. My Backup is set to delay firing for 1 second after apogee and 50 ft lower for main deploy.

I use the same brand and model altimeters for both redundant systems so apogee detect and altitude for each is very close You may need to increase the apogee delay and main altitude deployment difference if you are using two different brands of altimeters because of the difference in circuit design, hardware used, and firmware. They probably won't be detecting the same apogee or altitude.