3 ms·

One thing I've often wondered about NASA's triple redundancy: what system calculates or determines the consensus? Is it also a programmable computer, just small

• akira2501 6y ago
  Usually the driven element itself. From [0]: "One reason why the redundancy management software was able to be kept to a minimum is that NASA decided to move voting to the actuators, rather than to do it before commands are sent on buses. Each actuator is quadruple redundant. If a single computer fails, it continues to send commands to an actuator until the crew takes it out of the redundant set. Since the Shuttle's other three computers are sending apparently correct commands to their actuators, the failed computer's commands are physically out-voted79. Theoretically, the only serious possibility is that three computers would fail simultaneously, thus negating the effects of the voting. If that occurs, and if the proper warnings are given, the crew can then engage the backup system simply by pressing a button located on each of the forward rotational hand controllers." [0]: https://history.nasa.gov/computers/Ch4-4.html#:~:text=Its%20five%20general%2Dpurpose%20computers,such%20as%20ascent%20and%20descent https://history.nasa.gov/computers/Ch4-4.html#:~:text=Its%20....
  • jasonwatkinspdx 6y ago
    Just as a follow up spacex has written a bit about their systems, which follow the same "actuator is the judge" approach: https://space.stackexchange.com/a/9446 https://space.stackexchange.com/a/9446