Project Years: 2022-2023
Contributors: Owen Busch
Altium365 Project: https://americas-starr-university-of-alberta.365.altium.com/designs/607E4B4C-F050-44CB-A011-97D16F26849D#design
Github Repo: None
The Altimeter Power Distribution Board was the sister project to the GPS Power Distribution Board. Its role was essentially identical to the GPS Power Distribution Board, but had higher current switches to supply enough current when the altimeters fired their e-matches. The two projects had significant schematic similarities, but the PCBs were significantly different. Unfortunately, we were concerned about controlling flight critical components with untested SRAD components, and the board was never manufactured.
The Altimeter Power Distribution Board would probably have worked fine. The size of the terminal blocks may have been too large. At the time, trusting an SRAD board to provide power to flight critical COTS boards was deemed too risky. While arming altimeters would be very convenient, it complicates the arming procedure and acts as a point of failure in a flight critical system.
However, the same can be said for the GPS Power Distribution Board. For most altimeters, wireless arming is not necessary and is mainly a nice-to-have. But, when you have an altimeter connected to a second stage ignitor the person arming could be seriously hurt if that altimeter were to cause the second stage to ignite.
So, the power distribution pathway for flight critical components should be as simple as possible. This means altimeters and GPS trackers should be armed by a single screw switch, magnetic switch, or wireless arming switch, and not a chain of multiple arming methods. Physical arming methods should be prioritized over more complex methods (magnets, wireless), except when an argument can be made for making the arming procedure safer. Additionally a physical and wireless arming method should be combined for second stage ignitors, where the physical method is used to physically disconnect the ignitor and electrically shunt it, rendering it inert.
In light of this review, we decided to revive the wireless arming method for Albireo’s second stage Blue Raven altimeter. This would become the first revision of the Wireless Arming Switch. Similar design constraints were considered in both designs.