So this is one of the two thermal vacuum chambers that we typically use for our CubeSat testing. This larger chamber and then there’s one behind it that’s a smaller chamber are the two. This one uses liquid nitrogen. And the other one uses just some type of coolant, like in your car that you’d find. So this one requires 24/7 supervision when it’s running with the liquid nitrogen. But the purpose of this large chamber is to create a vacuum and then change the temperature inside the vacuum so that the satellite can experience the hot and colds of space, or of the low earth orbit that we typically fly in.
So what you see here is a big shroud, that’s the black painted portion on the door and right here. And welded to that shroud are coils which a liquid is pumped through that is cooled by the liquid nitrogen. So it’s a closed loop system that can reach temperatures from minus 60 up to plus 80 degrees. The other chamber back there can do minus 20 Celsius up to 125 Celsius. So we have a shroud that gets cooled and heated and we also have what’s called a platton, which is this table that slides out, that we sit our satellite on; it is also cooled and heated by the same system. You can see the pipes running through here. So a typical test that we’ll do is called “A Day In the Life Test,” so we want to put it through its paces, make sure that it will do not only survive in space but that it’s going to do what it’s supposed to do in space.
When you’re in orbit, you have a lot of other things to think about that you don’t when you’re here on earth. And we need to make sure that the thermal properties, the thermal profile that we design to is actually realistic so like we did with the vibration testing, with accelerometers, to measure the acceleration. On this one we have thermo couplers, which are pretty much just thermometers, that we attach to the satellite in the newly designed areas or all over the satellite depending on the maturity of the satellite. Then we heat and cool the chamber. We’ll do what’s called T-Vac cycling or thermal vacuum cycling, where we’ll start out at room temperature, we’ll pump the chamber down to vacuum, usually we have to be at 1X10 to the minus 4 tor. Once we get down to that vacuum, then we start the cooling and heating. So we usually will go hot first, so that we can bake out any contaminants, the launch provider doesn’t want you to attach a dirty satellite. So, by cooking it or by raising the temperature initially, a lot of the contaminants, or any kind of contaminants will bake out. Then we’ll go down cold and we’ll do a functional test, we’ll run a few different scripts to make sure that it can perform when it’s really cold. The main thing we’re looking at during the cold cycle is battery testing; making sure that the batteries stay above a certain temperature. A lot of batteries cannot be charged below a certain temperature. The ones that we typically use are zero Celsius, so we have to make sure that any kind of heaters we have kick on at the right time and that we’re not charging the batteries when they shouldn’t be. And then on the opposite side of that, when we are in the hot side, we make sure that things aren’t getting too hot, that we are dissipating our heat through radiators or through other methods.
In space, you don’t have the convection of heating, the thermal convection, you have mainly radiation. But it’s good because space is nice and black so it likes to absorb, earth also puts off some heat. So there’s a lot of thermal aspects we that have to take into consideration and so our satellites spend a lot of time in these types of chambers. Because we can do a lot of testing on the bench but there are a lot of differences between doing a test on the bench and doing a test in the chamber. We’ll do typically two or four hot to cold cycles before we complete. Once we’ve completed all of our thermal vacuum testing, then we are usually not allowed to open our satellite up again; that’s what’s considered breaking configuration and if we do that, we would have to start both thermal vacuuming and vibration testing all over again.