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The software that flies SpaceX rockets and starships

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Re: The software that flies SpaceX rockets and starships

#31

Interesting 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

Telemetry can be packaged up and sent out at higher than the control loop rate (if needed). There's nothing keeping you from having a buffer that stores up higher frequency data that gets read off and sent off as a blob each control loop.

Re: The software that flies SpaceX rockets and starships

#32

Interesting 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

I would assume something like an engine controller or some other control loops might run internally at a much higher frequency. But the main control loop which orchestrates all components is able to run at lower frequency.

Re: The software that flies SpaceX rockets and starships

#33
post #27

Earlier 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,…

[flagged]

Re: The software that flies SpaceX rockets and starships

#35

> ...when you plan to reuse booster rockets and shuttles on future missions. Shuttles? I'm aware of the general term shuttle as a vehicle for going back and forth, but here I'm certain that the better term would be craft, capsule, or Dragon. Certainly not shuttle.

A space shuttle is by definition a reusable spacecraft that carries people and cargo between Earth and space.

You mean the shuttle has been replaced by something newer and hence is an obsolete word?

Re: The software that flies SpaceX rockets and starships

#37
post #6

Earlier quoted context omitted.

I thought that too initially, but if you think about the physics it makes sense.. the larger the mass the more stable the object, the lower the frequency of acceleration needed to adjust it's trajectory. Also even though it's dynamic, it's not articulated or anything like dynamic robots. Take the opposite, a little quad copter, very low mass, will need very high frequencies. I used to manually fly miniature remote co…

> 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.

Re: The software that flies SpaceX rockets and starships

#38
How 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 there got to be one in the world.

Re: The software that flies SpaceX rockets and starships

#39
post #8

If someone from SpaceX is reading (after 5pm, of course), can we get a more nitty-gritty of what's going on software-wise on your end? I'd love to see what control and embedded wizardry you guys are up to.

There is a Reddit AmA by SpaceX software team that has some important details!

Yep, this and there is a Quora question somewhere I think iirc.

It's mostly LabView I think, which is an interesting choice given all the hate it gets.

For those that don't know, LabView is a graphical (drag and drop) language for the most part where you interconnect various hardware components together. The advantage is that a lot of labs need to plug a lot of devices and sensors to run an experiment and LabView has support for a large amount of hardware. So you connect it all and can graphically view what the outputs are doing in chart form. The downside is that I don't think it's always very easy to specify exactly what you want to do, and code can pretty easily become spaghetti. There are a lot of horror stories about engineers having to maintain someone else's code.

Edit: -Flight software is C++ -Launch is mostly LabView and yes, they have LabView running in mission control

Re: The software that flies SpaceX rockets and starships

#40
post #38

How 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…

iirc all flight systems are in triplicate and all data is checked against the others, then a quarum is needed from the 3 to make a decision.

other rockets use rad hardened computers that make decisions on their own, but for cost and time, I believe SpaceX just triplicated all necessary systems and votes out and reboots any system that gets bit flips.

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