They're not running a dependency-ridden NodeJS backend with MongoDB and random cloud services? How are they even able to get to space?
No Kubernetes and Blockchain ?
The software that flies SpaceX rockets and starships
41–50 of 112 posts
Re: The software that flies SpaceX rockets and starships
#42How are distributed realtime systems like a rocket is synchronized? Are there central timeservers and allocated transmission slots and timestamped query-response action messaging or is it just small individual realtime nodes making their own decisions? I’ve been wondering about this for a year or so because I can’t seem to find one that matches my description, other than concept drawings on NIST 4D/RCS paper, but the…
There's typically a central time source sending a 1Hz pulse into the main computer(s). The sensors will use something like Time Triggered Ethernet, RS-485, or a MIL-1553 bus.
Re: The software that flies SpaceX rockets and starships
#43Interesting that they are doing updates at only 10 and 50Hz. I had kinda assumed they'd be looking at much higher frequencies for telemetry especially for things like the rocket motor metrics
Keep in mind that this is _reaction time_. As in, if something happens to an engine how fast do I need to react to safe it before it spreads to other things. Turns out that 20ms response time is plenty appropriate.
Are there any processes in combustion dynamics faster than 20ms? You bet there are, and when the engine is being tested they are instrumented with high speed probes, because during development/testing you want to _understand_ what’s going. When you are flying you want to stay in control first and foremost.
Of course, it would be awesome to have everything on high speed data acquisition channels. But there is a very limited telemetry budget and everyone is fighting for it. So compromises have to be made.
There probably are high speed probes on the rocket, such as strain gages. And if an engineer thinks that having a high speed engine metric would be _critical_ to do postmortems then it will most likely be included.
So, I would say that assigning telemetry budgets it’s a holistic process where multiple teams fight/cooperate to share that budget and prioritize absolutely critical data channels.
Re: The software that flies SpaceX rockets and starships
#44How are distributed realtime systems like a rocket is synchronized? Are there central timeservers and allocated transmission slots and timestamped query-response action messaging or is it just small individual realtime nodes making their own decisions? I’ve been wondering about this for a year or so because I can’t seem to find one that matches my description, other than concept drawings on NIST 4D/RCS paper, but the…
There's typically a central time source sending a 1Hz pulse into the main computer(s). The sensors will use something like Time Triggered Ethernet, RS-485, or a MIL-1553 bus.
Yeah this is in line with my experience. However there are concerns about the accuracy of quartz clocks as temperatures fluctuate, this poses a problem for some orbital patterns.
Re: The software that flies SpaceX rockets and starships
#45Earlier quoted context omitted.
If it crashes and Dragon is in manual mode, then what?
How about a response from SpaceX software guy that works on Dragon software, including these displays: > Dragon is a fully autonomous vehicle, so it is capable of completing the trip to and from the ISS without any interaction from the crew. But the displays and button panel do provide the crew with capabilities should they need to take action due an unexpected scenario or emergency. As for the tablets and displays,…
"Spam in a can."
Re: The software that flies SpaceX rockets and starships
#46How are distributed realtime systems like a rocket is synchronized? Are there central timeservers and allocated transmission slots and timestamped query-response action messaging or is it just small individual realtime nodes making their own decisions? I’ve been wondering about this for a year or so because I can’t seem to find one that matches my description, other than concept drawings on NIST 4D/RCS paper, but the…
A popular solution is PTP [0]. Once you have synchronized hw clocks you lay your software synchronization on top of that.
Re: The software that flies SpaceX rockets and starships
#47How are distributed realtime systems like a rocket is synchronized? Are there central timeservers and allocated transmission slots and timestamped query-response action messaging or is it just small individual realtime nodes making their own decisions? I’ve been wondering about this for a year or so because I can’t seem to find one that matches my description, other than concept drawings on NIST 4D/RCS paper, but the…
fprime is what you're after; it's the embedded flight hardware that runs on the Mars 2020 drone.
https://nasa.github.io/fprime/Architecture/FPrimeArchitectur...
Re: The software that flies SpaceX rockets and starships
#48How are distributed realtime systems like a rocket is synchronized? Are there central timeservers and allocated transmission slots and timestamped query-response action messaging or is it just small individual realtime nodes making their own decisions? I’ve been wondering about this for a year or so because I can’t seem to find one that matches my description, other than concept drawings on NIST 4D/RCS paper, but the…
fprime is what you're after; it's the embedded flight hardware that runs on the Mars 2020 drone. https://nasa.github.io/fprime/Architecture/FPrimeArchitectur...
fprime is more of a set of libraries and daemon architectures, not really hardware time synchronization.
Re: The software that flies SpaceX rockets and starships
#49Re: The software that flies SpaceX rockets and starships
#50Earlier quoted context omitted.
> the larger the mass the more stable the object Not really. Only when scaling mass, margin of error, and forgetting thrust/gravity. And even if you scaled mass, thrust, and margin of error proportionally, you'd still have an object exactly as stable as before (force X applied to the small object gives you the same acceleration as proportionally scaled force Xs applied to a larger object). Gravity accelerates all thi…
A spacecraft may need to be super accurate at docking, but outside of that precision is far less important.
Docking is also done extremely slowly.