11–20 of 112 posts
It is fascinating that they solve robustly 50 times per second a control problem and handle gracefully numerical issues. Granted they have dedicated hardware to do so that fast, but it never stops to amaze me.
They're not running a dependency-ridden NodeJS backend with MongoDB and random cloud services? How are they even able to get to space?
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!
Earlier quoted context omitted.
There is a Reddit AmA by SpaceX software team that has some important details!
A direct link would be very much appreciated
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
For a SpaceX mission, there isn't a lot that can go wrong in 2 hundredths of a second that you could have magically resolved if you saw it 1 hundredth of a second earlier (i.e. at a 100hz rate).
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 found this also interesting. I can see how it simplifies the mathematics to use a fixed time interval. Can anyone experienced comment if 10Hz is very different or the same as vehicle control systems such as a modern car? Also, are these systems fixed or floating point? Fixed time intervals would help keep numerical instability of floats in check (however I'd really hope this is more formally understood for such a s…
Nowadays I work with satellite SW. Most of the control loops are pretty slow. The fastest ones are those controlling gyros and reaction wheels that run in 5 or 10Hz
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
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 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…
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 things the same, and so do proportionally stronger thrusters.
But being off by one meter can destroy a small drone just as well as a large spacecraft, so you don't have the luxury of scaling your margin of error by significant amounts.
The only reason larger objects appear more stable to humans is because we, and the environment[1], tend to apply relatively weaker forces to them, and also you don't tend to notice they're already moving at 5m/s because of their size.
[1]Larger objects will better compensate for "truly random" forces, if their size causes them to encounter more of them, canceling them out and/or they're generally small.