Those examples were naval ships. When you can float a huge data center in water and dump all the waste heat you want, it doesn't matter that the Perc vm used is 2.5x as slow as the sun vm. Or that it uses even more ram than a normal java vm which is already a lot. This is running on a microcontroller.
Both fair points. Hard real-time is absolutely doable with GC if it is deterministic. It has throughput and memory penalties to get low and predictable latencies but it is regularly done. I have written soft real time java myself. And other than avoiding garbage like you would do with any low latency code with GC, it was idiomatic. But that one change does increase cognitive burden to the point I didnt find it any more productive than C++. If I had needed reflection I might have felt differently.
I've done lots of hard real time c++. It certainly has development time overhead, but the memory usage was the same as idiomatic c++, just everything was preallocated at max usage. No throughput hit either, if anything it was faster because of no allocations.
I've done safety critical that wasn't MISRA. But you have reminded me that for years we were leaving optimization off so we could verify full code and branch coverage in the assembly. At which point Java is almost certainly faster, though we never would have fit in memory with Java. Eventually we started turning optimization on and it was harder to verify but not impossible.
Not to accuse spaceX of anything, but I've witnessed companies sell 'hyper-localised weather" where they take public weather information and average the nearest two datapoints to you.
So I always take 'secret' 'proprietary' data and algorythms with a bit of salt, as almost every time I dug into them, it was all spin on previous public stuff.
In this case, SpaceX is actually landing those Falcon boosters pretty reliably now. So maybe their secret proprietary stuff isn't as advanced as they make it out to be, but whatever they're doing it does seem effective.
