Falconsat-II Engineering Model
Environmental testing. Kirtland AFB, Albuquerque, NM.
April 19 - 26, 2001.
Falconsat-II was built at the Air Force Academy in Colorado Springs by cadets and faculty. This is the Engineering Model, which was built this spring to test the basic design and our ability to make some of the parts and integrate them. In the Fall of 01 we will build a Qualification Model which will also be thoroughly tested but will be very close to the design that is put into space. In the Spring of 02 we build the flight model for a launch on the Space Shuttle in early 03.
We put the engineering model of Falconsat-II in a big shipping case and loaded that into the back of my pickup for the trip to Albuquerque. We arrived about midnight, unloaded the satellite case and the boxes of support equipment into the environmental test facility and headed for the hotel. Next morning we unpacked it and started some testing. Later that day we put it into a bake-out chamber that pulls a vacuum and heats it to 40C. This picture was taken while moving it between the test area and the bake out chamber. The right side in this photo is a test solar panel built by cadets. The flight model of the satellite will have one of these on each side. The side closest to me (you can see my reflection in it) is covered with thermal tape that will cool the satellite. For this engineering test model the other two sides are bare. On the top right you can see the test S band transmit antenna and on the side closest to my head you can see the test uplink VHF antenna. On the bottom you can just see the ring that will be clamped to a mount in the payload bay of the Shuttle. For launch, a clamp is released and springs push the satellite away from the Shuttle. The satellite is hanging from a 7 ton crane, you can see the clevis pin and cable at the top middle. The satellite weighs about 35 lbs. and is about 14" on each side.
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Here is a better look at the top of the satellite. The three square holes are the science sensors which make up the experiment we are carrying into space. The experiment is called MESA and measures holes or bubbles in the plasma field of the upper ionosphere at an altitude of about 360 km. These holes can disrupt communications with satellites in higher orbits so they are of great interest to space weather scientists. No satellite has measured them with the precision we hope to achieve with FS-II.
You can also see here the S band (2.4 GHz) antenna the satellite will transmit through; it's the one that looks like a cocktail drink umbrella. The thing that looks like a spring on the left side of the picture is a first attempt to build an antenna for the satellite receiver. It's a difficult problem because there isn't room to make it as long as it should be.
The big brass alligator clip and yellow wire are the ground connection. We have to be very very careful about static electricity so the satellite is grounded as are all the people working on or touching it. You can just make out the red band around the wrist of the cadet working on it and the coiled wire that runs from it to a smaller alligator clip attached to the big brass one.
The connectors in the top that have labels next to them covered with yellow tape are for the connections to our test equipment and portable ground station.
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One of the tests we did was illuminate the solar panel with a full spectrum sun lamp and measure the voltage and current it produced. The panel generated just what we expected and there was much singing and dancing. Here is one of the technicians that work in the lab pointing the sun lamp at the satellite. This lamp is quite bright and can injure your eyes. He is wearing UV protecting glasses, as were all of us that were near it.
And here is what the side of the satellite looks like when illuminated by the sun lamp. Gives you an idea of how bright the sun is on the satellite in space. The round object on the end of a pole at the bottom right is a meter to measure the intensity of the light. We adjusted the lamp to produce the same amount of light as the sun while the satellite is in orbit.
Here we are taking off the plastic cover that protects the solar cells while moving the satellite around or working on it. That cover has to come off any time it goes into a chamber to be tested or onto the shake table to be vibration tested. Elsa Bruno is holding the cover while I remove the bolts that hold it on. The solar array is very delicate and very expensive. If we bump it there is a good chance a cell will crack, which could disable the entire string of cells that together make up the array. These are rejected cells we are using on the engineering test model, but if new would cost about $15,000. Even on this model if we mess up a cell we blow our ability to obtain the test data along with several weeks of work. So we are being very careful.
When working around a satellite you plan every move and move in slow motion. It's kind of like working under water. One false move and you can cripple a very expensive piece of equipment and possibly blow your opportunity to launch it.
Cadet Chris Charles and Jim are hooking up the cables needed to test the satellite. Cables run between the satellite and our ground support equipment which was located on a couple of tables next to the satellite. Jim is wearing a full clean room outfit here, including a mask covering the facial hair, because we have the satellite opened up and need to assure the inside stays clean. You can see one side has been removed here so we can connect some cables inside and so we could inspect it. There is a lot of extra wire in this engineering model because we used a wiring harness that wasn't built specifically to fit into this hardware. That is why you see loops of wires taped and glued down with RTV in this picture. For the Qualification and Flight models we will build a custom wire harness that will fit exactly where it needs to go to connect all the electronics modules together. RTV is expensive space rated bathroom caulk. The tape is Kapton and is space rated. It doesn't leave a residue, stays on in extremes of temperate and doesn’t come off in a vacuum. It, like the RTV, is quite expensive.
Discussing cleaning and avoiding contamination with cadet Doug McHam, who is the lead on the power system team. We spent a lot of time showing this cadet group how contamination happens and how to avoid it. I had some stuff in my hand that we found on one of the modules after it had been cleaned.
The FS-II EM with two sides removed. We had to take off two to be able to reach some of the spots we wanted to attached thermocouples. The thermocouples are put inside and outside the satellite in many places (we attached 23 for the thermal vacuum test) so we can see how hot and cold various parts get when we move the environment in the chamber between about +40C and -20C. These measurements, along with those taken inside the module boxes by the satellite telemetry, will be put into a computer thermal model of the satellite which will then be used to determine what coatings (if any) we need to put on the outside to keep it the right temperature in space. The cables hanging off the top go to the portable ground station and test equipment. In the picture you can see the basic structure of the satellite. There is a base plate with a four sided column in the middle. The electronics module boxes are mounted to the four sides of the column, which does not reach to the top plate. There are four side panels mounted to the bottom plate, and a top plate bolted to the sides. The entire structure was machined at the AFA from solid chunks of aluminum about 3" thick. You can see that square holes have been milled out of the sides in a sort of waffle pattern. This retains the strength while significantly reducing weight and mass.
Cadets get instruction in placing thermocouples on and inside the satellite prior to the start of the thermal-vacuum testing.
The first group of cadets who participated in the test program in front of the satellite just prior to putting it in the TV chamber. At this point, a job well done.
After thermal-vac testing it was time to do the vibration testing. Here the satellite is on the shake table and we are again measuring the output of the solar panel.
Two cadets from the second group stare intently at the PCs showing the test results.
The method of attaching the cells to the side panel of the satellite needs some work. Here you can see on of them cracked during vibration testing. A better fabrication method is in the works.
After testing was completed it was back into the shipping case and back to the AFA for further testing and evaluation.
Next step is to review all the data from this test of the Engineering Model, do a lot of paper work for NASA, then start on the Qualification Model in the Fall of 2001.