- Posted by doEEEt Media Group
- On June 2, 2021
Vibration tests are intended to reproduce the vibrations experienced by the satellite during the launch phase in order to make sure that the satellite will not suffer during this phase.
Vibration Testing is a very specialized field where Alter Technology is a highly qualified laboratory performing numerous tests in EEE Parts. To do this kind of service, we have extended and qualified laboratory accreditations that bring to your needs secure and safe work. These include the ones related to Small spacecraft and units. The applicable standards are:
- ISO 19683 refers to ISO 15864.
- Launcher’s requirements
Vibration Laboratory Equipment
Vibration tests need the use of a shaker that vibrates on one axis. This shaker is characterized by its force, and therefore the acceleration profile to which the EUT can be exciting depends on the mass of the EUT (F=m·a).
The acceleration profile is measured with a set of accelerometers and registered with a data acquisition system
In the case of CubeSats, a test pod is needed to reproduce how the CubeSat is attached to the launcher. In the following picture, we can see a test pod for a 3U CubeSat plus an interface plate.
Typical vibration tests include quasi-static, sine sweep, and random tests in all 3 axes, with eigenmode survey (low-level sine sweep) and possibly functional tests after each test to check for structural and functional damage.
- Quasi-static vibration tests are in fact, a proxy to static acceleration tests intended to reproduce the first stage of the flight when the launcher is accelerating. However, static acceleration can be simulated just in centrifuge stations, which are scarce, complex, and expensive. Therefore, this test is often replaced by the quasi-static profile, consisting of a series of “bumps” at a low frequency and duration of several minutes.
- Sine sweep intends to excite and stress every single vibration mode in a given frequency range (typically low, 5-100Hz to excite the structure of the CubeSat) with a high acceleration level to make sure that all failure modes of the structure are tested.
- Random vibration intends to reproduce the mechanical environment inside the fairing, which is a broad spectrum and difficult to reproduce exactly.
- Low-level sine sweep is intended to detect changes in the vibration spectrum of the CubeSat, which are indicative of a displacement of the equipment, loosening of screws, or cracks in the structure.
A typical vibration test flow is shown in the following figure:
Concerning the test levels, the launcher fixed these because the vibration levels are typical of each launcher. In CubeSats, they are often deployed from a container provided by a third party, which can also influence the vibration profile.
If the satellite under test is a flight model, it is important to ensure cleanliness during the vibration tests. Two approaches are possible: to place the satellite and the shaker table under a laminar flux of clean (ISO8) air or to perform the tests with the CubeSat inside a tight bag. The first option is preferred because, in the second one, holes have to be practiced in the bag to pass the cables, which can be a potential inlet for contamination.
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