The ARINC scheduler, RTOS, and redundancy have been used in safety-critical for decades. ARINC to the 90's. Most safety-critical microkernels, like INTEGRITY-178B and LynxOS-178B, came with a layer for that.

Their redundancy architecture is interesting. I'd be curious of what innovations went into rad-hard fabrication, too. Sandia Secure Processor (aka Score) was a neat example of rad-hard, secure processors.

Their simulation systems might be helpful for others, too. We've seen more interest in that from FoundationDB to TigerBeetle.