11–20 of 28 posts
Earlier quoted context omitted.
Did Shuttle fly with these bodge-wired boards or were these used for development on the ground?
I don't know if these boards were flown. They were coated with conformal coating (which I hate for reverse-engineering), which is usually omitted from prototypes. I believe that bodge wires are okay for flight if they are done properly.
Earlier quoted context omitted.
Yes, the low density and TTL chips (instead of MOS) helped against radiation. When the Shuttle computers moved to semiconductor RAM, they needed extensive error correction, as well as a process that constantly fixed bit errors, as the memory would get multiple errors per flight due to cosmic rays. As far as redundancy, it's complicated. During critical flight phases, four computers would run the main software (PASS,…
what a treasure-trove of historical technical info you have do you know anything about the military's secret space-shuttle still in operation? I'm sure it's either been very modernized or runs on completely different design since it's supposedly remote-control
oh that is absolutely fascinating to see in detail I wonder if the very low density (relatively speaking to today) make them more robust against gamma-rays and other radiation problems once outside the atmosphere? if I remember correctly, and it's been decades of course four of the computers ran in parallel with the exact same instructions in case one failed or came up with a wrong answer and the fifth computer was t…
Yes, the low density and TTL chips (instead of MOS) helped against radiation. When the Shuttle computers moved to semiconductor RAM, they needed extensive error correction, as well as a process that constantly fixed bit errors, as the memory would get multiple errors per flight due to cosmic rays. As far as redundancy, it's complicated. During critical flight phases, four computers would run the main software (PASS,…
Thanks so much for the information. I am familair with the voting logic (I've worked on systems that implemented the same thing, odd-number of processor cores and the majority wins).
One question, were any "misbehaving" processor or actuation requests ever logged? As in, were there examples where one actuator or CPU didn't agree in the Shuttle flights?
Earlier quoted context omitted.
Yes, the low density and TTL chips (instead of MOS) helped against radiation. When the Shuttle computers moved to semiconductor RAM, they needed extensive error correction, as well as a process that constantly fixed bit errors, as the memory would get multiple errors per flight due to cosmic rays. As far as redundancy, it's complicated. During critical flight phases, four computers would run the main software (PASS,…
Hi kens, Thanks so much for the information. I am familair with the voting logic (I've worked on systems that implemented the same thing, odd-number of processor cores and the majority wins). One question, were any "misbehaving" processor or actuation requests ever logged? As in, were there examples where one actuator or CPU didn't agree in the Shuttle flights?
[1] Search for "GPC" in the Mission Summary report: https://newspaceeconomy.ca/wp-content/uploads/2023/05/space-...
Glass capacitors!!!! I didn't even know this existed! and made by Corning!
Earlier quoted context omitted.
I don't know if these boards were flown. They were coated with conformal coating (which I hate for reverse-engineering), which is usually omitted from prototypes. I believe that bodge wires are okay for flight if they are done properly.
That's amazing. My bodge-wired work won't last 10 miles in the trunk of my car.
oh that is absolutely fascinating to see in detail I wonder if the very low density (relatively speaking to today) make them more robust against gamma-rays and other radiation problems once outside the atmosphere? if I remember correctly, and it's been decades of course four of the computers ran in parallel with the exact same instructions in case one failed or came up with a wrong answer and the fifth computer was t…
Yes, the low density and TTL chips (instead of MOS) helped against radiation. When the Shuttle computers moved to semiconductor RAM, they needed extensive error correction, as well as a process that constantly fixed bit errors, as the memory would get multiple errors per flight due to cosmic rays. As far as redundancy, it's complicated. During critical flight phases, four computers would run the main software (PASS,…
Glass capacitors!!!! I didn't even know this existed! and made by Corning!
Earlier quoted context omitted.
Yes, the low density and TTL chips (instead of MOS) helped against radiation. When the Shuttle computers moved to semiconductor RAM, they needed extensive error correction, as well as a process that constantly fixed bit errors, as the memory would get multiple errors per flight due to cosmic rays. As far as redundancy, it's complicated. During critical flight phases, four computers would run the main software (PASS,…
How did the voting work? The first thing I thought was, what happens in a tie (2-2) vote?
Mission STS-9 had two computer failures, causing landing to be delayed by 7 3/4 hours. They carried a sixth computer as a backup for following missions.
As far as how the voting works, each computer has a signal indicating what it thinks the status is of each computer, including itself. (Computers can detect many failures from self-checking, such as parity errors.) Each IOP uses these votes to determine the "redundant set", calculating the votes in hardware. The status is also displayed to the astronauts in a 5×5 grid. Astronauts can power down a computer or reboot it.