SpaceX sets a roughly 40 Hz floor for satellite resonance

Transcript

Transcribed by machine (Whisper) from the episode’s audio, so a word may be off here and there.

1. 40:54

   The more you know. Science. So, Philip, we're back at the vibe table, and we're about to do some testing. Do you want to explain this? Yeah, so we need to simulate the launch environment. And so in order for SpaceX to allow us to launch on a rocket with multiple tenants, they want to make sure that both nothing's going to fly off from any individual satellite in launch, But also, they don't want any satellite to resonate at a certain frequency, which throws the whole stack off.

2. 41:23

   And so the point of the VibeTable is to put the satellite through every different frequency and amplitude that the satellite is going to experience during launch, and also this shock test, so that we make sure nothing flies off and we also make sure that we don't have resonance at a certain frequency. How long do you run it for? It depends on the test, but the launch environment itself is about seven minutes.

3. 41:43

   and so there are some tests we would run for a few minutes most tests we run for a shorter period especially what they call uh the sort of um yeah like random vibe we run a bit longer but there is the shock test we run for shorter have you ever sat on a vital i have never sat on that i have to say yeah people i've touched them before but we were at zipline and we went into their testing room and they had a vibe table and these like rc propeller like rc fans oh yeah to test the drones with and they would fly them in front of it and see if anything would you know be fragile or break if there were any, like, fractures and it ended up just being me walking through RC bands.

4. 42:37

   No way. Which is, I think they go like 80 miles an hour. Wow. Yeah. Crazy. Oh, there you go. Oh. So this is a very low frequency test. We're doing it at low frequencies, mainly so that you can see what it looks like when it moves, but when it moves faster, basically you won't be able to see it moving. that's... they're moving at least 50 hertz, so 50 times back and forth per second, and this is basically a huge solenoid, so a huge magnet that's pulling this thing in and out. It's basically speeding up now. So we lock in? Yeah, we're good.

5. 43:22

   so the hardware we have on the table at the moment is part of our thermal management system called the accumulator so as the so we have liquid cooling on star cloud 2 and all of our future vehicles as the liquid heats up it wants to expand and so you have to have a component which allows that expansion to take place otherwise you'll burst your your cooling system so that's what the accumulator does it's uh it allows for that thermal expansion of the fluid to manage the pressure inside the cooling system.

6. 43:51

   And that's what we have on the table right now is the accumulator for StarCloud 2. We get... yeah, go for it. Yeah, yeah. There you go. So... Oh my god! Cloud's crazy! Yeah, so this is... right now the test it's doing is what's called a sine sweep. It's where we're going to go through every different frequency and amplitude that the satellite will experience during launch so it starts very low frequency we're doing this low frequency normally we wouldn't even start this low but we wanted to be able to see that it's moving here as it gets faster and faster it won't really be able to see the moving of it what is the worst thing that a vibe table has done the worst thing that a vibe table well has a vibe table like ever like as a magnet like shot out or anything? No, the actual vibe tables themselves are pretty safe. The worst thing that can happen

7. 44:59

   with a vibe table is whatever you're testing can explode. So, for example, underneath StarCloud 2, we have this xenon tank for the thrusters. And if the xenon tank explodes, it's about half the explosive power of a hand grenade. Great. That's awesome. That's really good to know. yeah okay that's why we're not doing that test today so yeah so does everyone leave the building when you test that literally everybody leaves the building so we had we put this entire satellite uh on this by the way you can see it's in two axes so the solenoid actually can flip up and we can test it like this so that we can test uh in different accesses but yeah when we fire that tester we have to everybody has to leave the building i doubt the toy manufacturer that has storage across the street has any idea what's going on in here they have no idea but they are

8. 45:54

   far enough away that we know that uh they're good they're safe yeah why is everyone running out yeah yeah that's first mode uh okay okay so what they're testing for is this first mode it's the first frequency at which is resonating and when you can hear it making this clicking sound that means we've hit the first mode of this thing here. What SpaceX requires is that you don't have a first mode below a certain frequency. I think it's around 40 Hertz so it cannot resonate at anything less than 40 times a second and the reason for that is let's say it would resonate like twice a second then the whole thing is gonna go like this back and forth and that will move all the other payloads in the stack. That's a really good point. So what is the process to get your space prop or any kind of components up into space tested to make sure that it's