[rtkwe]

They don't do 3x calculations and voting but they do often have redundant computers they can switch over to in case of failure. Curiosity had to switch to it's 'B-side' computer back in 2013 when A-side had a memory issue. Even when not carrying humans it's still a billion/million dollar mission that probably wouldn't be replicated for a while if ever (within the researchers life times at least) that could be scuttled by a softwer bug.

If anyone is interested JPL publishes their code standards doc for C: https://lars-lab.jpl.nasa.gov/JPL_Coding_Standard_C.pdf

[kevin_thibedeau]

Most spacecraft have some form of redundancy to guard against single point failures. It's a waste of money to send up failure prone hardware. Amateurs building cubesats, probably not, but the big players aren't going to take that sort of risk.

[marsRoverDev]

You are right, they have redudnancy in all cases - but it isn't usually software written by multiple teams with different hardware.