Vibration Test Equipment Shaker Head & Slip Table Demo
Vibration Test Equipment Shaker Head & Slip Table Demo - 22 Sep 2021
Hi, my name is Chris Sheffield and this is AFIT’s Environmental Test Lab. In here we do testing on our small satellites. On this half of the room we do vibration testing and on that side of the room we do thermal vacuum testing. So this side, we make sure it can survive launch and then that side we make sure it can survive in space.
So what we have right here is the vibration table. Right here is a slip table and back here is the shaker head. So the vibration system is pretty much just a big speaker. Right now, the speaker is facing upwards and it will shake that small satellite up and down. We can also rotate the shaker head down, attach it to the slip table and we can shake in the other axes. The point of this is so that we can test in all three axes. So we’ve got “Z,” we can do “X,” and then we can rotate the satellite like that and we can do “Y.” So for vibration testing, the purpose, like I said, was to survive launch. So the launch provider, say it’s SpaceX or NASA or whoever, will provide us the profile for their rocket and that way we can simulate the actual vibrations that it will experience on launch.
So during the testing, the first thing we do is we attach accelerometers, which are just sensors that pick up the acceleration of the moving object. So we attach an accelerometer to important parts of the satellite or newly designed parts of a satellite. So let’s say we would attach one on a camera because we want to make sure that it doesn’t break lose and is flopping around in the satellite. Another way we do it is with high speed video. And high speed video allows us to actually see what’s going on real time, so that we can then slow it down and then see how things are shaking. We can see if wires are rubbing, stuff like that.
So the first part of the vibration testing is a sign sweep. A sign sweep is characterizing the satellite to understand how it is supposed to respond to vibration after it’s initially built. Then, we go through the actual launch profile, which is a very, I mean, as you can see in launch videos, a very violent event. So we do that for about a minute or two minutes, depending on the ride that we get. After the random vibration testing, we do another sign sweep so that we can compare the before and after sign sweeps. So once we have the sign sweeps, let’s say there is a huge difference between the initial and the after, then we know we shouldn’t turn the satellite on just yet. We may do some more inspections, make sure there’s not stuff actually flopping around. One version I’ve had to use in a program was what they called a tilt test. This was a big organization and they had a machine, not just a person but they would rotate it back and forth to hear for pieces missing. Want to make sure you don’t turn it on if there’s metal parts that are touching other metal parts that it shouldn’t be or circuit cards, stuff like that.
So for the high speed video, what you can see is you have the connectors on one side, an antenna on the top and then the board stack in the middle. And since this video was shot at ten thousand frames per second, and it allows us to see the actual motions that are occurring. From this video, we were able to redesign to a better model that stiffened up the top to make sure the antenna wasn’t bouncing around as much and we removed the connectors on the board on the bottom because of the weight that they were adding. By removing those and just soldering straight into the boards, we enabled us to lose that mass and then there was no more flopping on that canalever board.
Here at AFIT, in the Center for Research and Assurance, we have successfully launched or successfully tested in this facility, four satellites that have launched and they have ranged from a 1U, which is this model right here and the model in the video. And actually, the model here is the second revision of that model in the video. We got a ride so we didn’t need to add solar panels. So we were able to shorten it down a little bit and stiffen it up. Another one that we did was called “SkyPad.” It’s not a true CubeSat form, but it’s about a 2U, and this launched in 2020. One of the first ones that we tested in this facility was a 3U, which is this one right here. And this one is actually a USAFA, or the Air Force Academy satellite, called “Falcon Sat 8.” And so they did all of the testing here, they came out and did their functional techs, we put it through the environmental testing, and that launched and they’re talking to it. We also, the first launch that we were a part of was also a 3U, named “Alice,” and that launched back in 2013.
So from 2013 – 2020, we’ve had four successful launches. The first one, unfortunately, did not respond, but since then we’ve communicated with all of them. In the coming years, in 2022, spring of 22, we will be launching a 6U, and that’s that model right here. And then in 2023, we will be launching another different mission 6U. We are also in the middle of producing 12U CubeSats and doing research for that kind of size. So what you have right here is called a CSD, or a Canisterized Satellite Dispenser. So this 6U slides into this canister, like a Jack-In-the-Box, gets shot out when the door opens. Once we know that we can survive launch, then we go over to the other side of the room and we make sure it can survive in space.