That would consume development and testing resources that could be put to better use. For example:
The Backup Flight System (BFS) was separately developed software running on the fifth computer, used only if the entire four-computer primary system failed. The BFS was created because although the four primary computers were hardware redundant, they all ran the same software, so a generic software problem could crash all of them. [...] While the BFS could run in parallel with PASS, the BFS never engaged to take over control from PASS during any shuttle mission.
This very system was responsible for the failure of the first shuttle launch. It turns out that there was a 1⁄64 chance that the clocks in the primary system and the clocks in the BFS would fail to synchronize on startup, and the very first scheduled launch hit the jackpot: the clocks didn’t sync, and NASA had to scrub the mission, and spend weeks figuring out what went wrong.
Interesting, I didn’t know that! Wikipedia says “A launch attempt two days earlier was scrubbed because of a timing problem in one of Columbia’s general-purpose computers.” and NASA says “Launch April 10 postponed due to timing skew in orbiter’s general purpose computer system. Backup flight software failed to synchronize with primary avionics software system.”, but this article explains the problem in extreme detail.
That would consume development and testing resources that could be put to better use. For example:
That is called Crazy Prepared.
This very system was responsible for the failure of the first shuttle launch. It turns out that there was a 1⁄64 chance that the clocks in the primary system and the clocks in the BFS would fail to synchronize on startup, and the very first scheduled launch hit the jackpot: the clocks didn’t sync, and NASA had to scrub the mission, and spend weeks figuring out what went wrong.
Interesting, I didn’t know that! Wikipedia says “A launch attempt two days earlier was scrubbed because of a timing problem in one of Columbia’s general-purpose computers.” and NASA says “Launch April 10 postponed due to timing skew in orbiter’s general purpose computer system. Backup flight software failed to synchronize with primary avionics software system.”, but this article explains the problem in extreme detail.