Spacecraft violently shake, rattle, and roll on their way into space aboard a giant explosion. Therefore, they must also be tested to make sure they can withstand those forces before getting to their orbit for deployment. One of NASA’s major observatories recently completed part of its trials, with the core portion of the Nancy Grace Roman Space Telescope successfully completing its shock and vibration testing a few weeks ago.
The testing took place at NASA’s Goddard Space Flight Center, where the core portion is being assembled. Eventually it will be combined with an “outer” portion to complete the whole telescope, and which will undergo its own set of testing as a full assembly. However, at least for now, the sub-components are undergoing individual testing as they are being put together.
Sub-components onboard the core portion include the spacecraft for navigation / control, instrumentation, and the actual telescope itself. The outer portion consists of the parts like the aperture cover, the barrel assembly, and the telescope’s sun shield. It recently completed thermal vacuum testing, which ensured that it could hold the appropriate temperature when subjected to the vacuum of space.
Fraser discusses how one part of the Roman Space Telescope - it's coronagraph - will change how we find exoplanets.Shock and vibration testing is a different beast though. It requires the assembly to be shaken through all the potential frequencies that it could experience during its journey into orbit. Cory Powell, the lead structural engineer on the project, describes the testing as “like an earthquake, but with key differences.” The team starts with low frequencies, sweeping up to higher ones that would shake the structure rapidly. “It’s a very complicated process that takes extraordinary effort to do safely and efficiently,” Powell says.
Part of the reason for that is the assembly will be tested beyond the limits it will theoretically experience during launch. Engineers always design systems with “tolerancing” - essentially they calculate what the highest expected value of a parameter would be that the system would experience, then they design it to withstand more than that. For example, if a telescope is expected to warm up to a maximum of 175 C, then the engineers should pick components that are rated up to at least 200 C, to give some “cushion” in their design. In the case of Roman’s shock and vibration testing, the system was tested to about 125% of the expected stresses it will be subjected to during lift-off.
Another confounding factor for this specific test is the liquid that will be inside the spacecraft. Roman will carry approximately 295 gallons of propellant to assist with it’s operations when in space. But liquid does some weird things when it’s shaken in a container, and those are sometimes hard to predict, even for advanced fluid dynamics modeling systems. Roman’s engineers loaded its propellant tanks with 295 gallons of deionized water for this test, to ensure that the sloshing, which essentially adds additional force as the water pushes one way or another, wasn’t enough to overly stress any part of the structure.
Video discussing some of the tests Roman has been going through. Credit - NASA Goddard YouTube ChannelTesting seemed to go well, with no major failures during the active test. However, the core portion was returned to the clean room at Goddard for further inspection. Any flaw such as hairline fractures or a loosened bolt could be a cause for concern, and might require some redesign or adjustment of the system. It remains to be seen if any such issues occurred, but the team will keep moving on with further testing as they research it.
Next up for the core portion are some electronics tests. Then it will move on to the thermal vacuum testing the outer portion just completed. In November, the two portions will be joined together, at least if all goes according to plan. And the final step would be actually launching, which is currently planned for May of 2027, though could be as early as the fall of 2026. That does depend on whether or not all the tests, including the final ones of the combined spacecraft go well. Hopefully Roman’s engineers did their design calculations correctly, and soon we’ll get another massive space telescope collecting data that can change the way we see the universe.
Learn More:
NASA / Eureka Alert - Core components for NASA’s Roman Space Telescope pass major shake test
UT - Roman's Telescope and Instruments are Joined
UT - The Nancy Grace Roman Space Telescope Could Study Dying Planets
UT - Construction of Roman Continues With the Addition of its Sunshade