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Hubble to resume science operations using three gyros

Engineers have apparently figured out the issues with one of the Hubble Space Telescope’s three gyroscopes, and plan to resume science operations today using all three gyros.

After analyzing the data, the team has determined science operations can resume under three-gyro control. Based on the performance observed during the tests, the team has decided to operate the gyros in a higher-precision mode during science observations. Hubble’s instruments and the observatory itself remain stable and in good health.

This is excellent news. If it had been determined that the funky gyro was no longer functional, the telescope would have shifted into what the engineers call “one-gyro mode.” By using only one of the two remaining gyros, Hubble’s life could be extended. However, while it would allow the telescope to point and continue observations, the images would no longer be as sharp.

Genesis cover

On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.

 
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9 comments

  • MDN

    Great news!!! Hubble is the modern day Lazarus and this story reminds me of this classic Monty Python scene…

    https://m.youtube.com/watch?v=uBxMPqxJGqI

  • Dick Eagleson

    NASA should promptly approve Jared Isaacman’s offer to conduct a free Hubble repair and reboost mission as the second of his planned Polaris exploits.

  • Chris

    Another question for the aeronautical engineers out there:
    In prior stories here on B-t-B and elsewhere there were proposals to provide interfaces on satellites to allow for refueling and to allow a tug to push or pull the satellite into a corrected or other orbit.
    An example:
    https://spacenews.com/u-s-space-force-and-astroscale-to-co-invest-in-a-refueling-satellite/

    Would it be advantageous to provide the same standardization and maintenance capabilities in satellites w.r.t. the gyro set?
    I.e. Make the (3-axis) gyro set a swappable unit with standardized power and signal cabling that can be changed by a repair satellite.. This could include upgrades (although I assume the best ring-laser-gyro is always used?)
    Provisions would need to be made to allow for calibration of the new unit and any other commissioning.
    Does this make sense or is the gyro set a component that is too robust to consider for such design?

    Thanks.

  • Edward

    Chris,
    Most satellites and probes are planned and launched with an expected mission lifespan. Even when NASA extends a mission, such as the Voyager probes, there is a process to get funding and Deep Space Network access. Geostationary commercial communication satellites are generally expected to last about 15 years, and their propellant supplies, solar arrays, and other components are planned to last somewhat longer. This is not a problem for the satellites that use technologies that become obsolete, but a few satellites use technologies that remain valid for longer periods. Thus, for most of these satellites, fifteen years is all that is needed for their gyros and reaction wheels to last.

    The smallsats of today are generally designed to last only a few years, perhaps fewer than five, most for fewer than ten years. They are inexpensive to make, inexpensive to launch, and their technologies are usually becoming obsolete even as they are being prepared for launch. They and their hardware are not intended to last very long.

    Hubble, however, was expected to last far longer. The mirrors were not expected to degrade much over the period of decades, and there was the Space Shuttle to service it regularly. Hubble was designed to be serviced, maintained, and upgraded with new hardware, including instruments, and several instruments have been replaced with updated versions or different instrumentation to perform different observations. Hubble was designed to last many more than just three decades. This is why we are so concerned about the lifetime of its gyros and other hardware. If we still had the Shuttle, or if we had another vehicle to service it, the gyros would not be a problem, as they would have been replaced already. Its slowly degrading orbit would not be a concern, as it would have been boosted years ago.

    Bearings have a hard life in space. First, they have to survive the rigors of ground testing, which often have mechanical shocks when pyrotechnic release mechanisms are tested. Then they have to survive the vibrations of launch. Then they have to survive the shocks of the flight pyro releases. It does not end there. Space is a different environment, and even radiation can affect the mechanical operations of bearings. Gyros and reaction wheels (sometimes called momentum wheels) use bearings, which degrade with time.
    https://www.youtube.com/watch?v=KibT-PEMHUU (Scott Manley, 7 minutes)

    Would it be advantageous to provide the same standardization and maintenance capabilities in satellites w.r.t. the gyro set?

    For most satellites and all deep space probes (unserviceable): no. For some satellites and any space station expected to last several decades: yes.

    Does this make sense or is the gyro set a component that is too robust to consider for such design?

    It makes sense, but Manley points out that ceramic bearings have not failed, yet, and may be robust enough for long space missions.

  • Chris

    Thanks Edward

    So the metal bearings were getting a welding shot – and inside the Faraday cage.

    Not wanting to draw this out too long but…
    That begs the question of how strong the ceramic bearings are -especially in shock. Perhaps this could restrict the launch and operational mechanical envelope it experiences.

    I have a bearing in my hip. Not metal, but metal with a ceramic coating – Smith & Nephew. This tech may be a more robust choice I wonder.
    The other thought is -I know its a vacuum – air bearing. There would be many challenges here but the “weightlessness” may reduce the pressure required for the bearing. The air gap may also be arced across – but it will not have the electrolytic properties of the grease. Far fetched. Thinking out loud – in text. Sorry.

    In any case, thanks for the answer and the depth of answer with the video.
    (No need to reply… I was just texting out loud.)

  • Doubting Thomas

    In 2009 all six Hubble gyros were replaced (swapped out) in a 10 hour spacewalk by Col. Michael T. Good and Dr. Michael J. Massimino operating from the shuttle Atlantis.

    Animation on effort is below.

    https://svs.gsfc.nasa.gov/10234/

    I wish that one of the robotic arms from the Space Shuttle would be place in a Starship for on orbit servicing of satellites with special focus on keeping Hubble science going for as long as possible. Keep that Starship in orbit for re-service missions and man the Ship as needed for said missions. Refuel ship and replenish as needed.

    Surely some of the $187 Billion of endowments from the Ivy Leagues could be used to fund this for the continuation of Hubble science. Throw in some of the $23 Billion from MIT and $4.9 Billion from CalTech and $3 Billion from Georgia Tech if you need a little more

  • GeorgeC

    The Shuttle might not be around but the people who did the last Hubble repair are. So I am sure they can figure out sone way to do it again
    https://en.wikipedia.org/wiki/Mike_Massimino

  • Edward

    Chris,
    So the metal bearings were getting a welding shot – and inside the Faraday cage.

    Yeah, weird stuff happens in vacuums and in space.

    Not wanting to draw this out too long but…
    That begs the question of how strong the ceramic bearings are -especially in shock. Perhaps this could restrict the launch and operational mechanical envelope it experiences.

    Bearings are a fascinating topic. Generally, they are an interference fit, which means that the balls are compressed within the races. Even the relatively soft steel balls can form micro-cracks that can lead to failure. The life of bearings suffers with higher loads and especially with higher speeds. Your hip is low on both, and likely is not an interference fit.

    Ceramics are high strength materials, but they are brittle, like glass. A crack can propagate quickly. We will have to see how they perform over long periods of use. Weird stuff could happen with them, too.

    Twenty years ago, in order to reduce shock-induced damages the commercial communication satellite manufacturer I worked for was exploring release mechanisms that did not rely on pyrotechnics. SpaceX’s fairing separation works on hydraulics, also to reduce shocks, and they are working on shockless separation for Starship, too. I think the Falcons already use hydraulics to separate the upper stage from the booster. Whenever I talk about the incentive for free market commercial space companies to improve efficiencies, this is an example of what I mean.

    The other thought is -I know its a vacuum – air bearing.

    Excellent! Now you are thinking out of the box.

    Start with the bizarre or impossible and see if you can find a way to make it work or to do something similar. I hate when TV shows and movies have brainstorming sessions and for every idea someone come up with someone else says, “you can’t because …” At the end of the brainstorming, everyone is dejected because all the ideas were shot down and disaster is sure to ensue.* They should keep the ideas in mind and think of ways to get around the pesky “can’t” part. Maybe a combination of impossible ideas can work around each other’s “can’t.”

    Gravity Probe-B used spinning spheres to measure the effects they sought to see. They had to be affected minimally by any stray forces or effects, and they definitely could not contact their housing walls. They were centered in their instrumented housings using electrostatic suspension ( https://web.stanford.edu/~sbuchman/publications-PDF/The%20Gravity%20Probe-B%20Relativity%20Gyroscope%20Experiment%20Development%20of%20the%20Prototype%20Flight%20Instrument.pdf **). Gyros do not have high loads, so a similar method could conceivably be used. However, there were a lot of electronics needed to make this work, so it may not be worth the expense or the onboard power. Or maybe it could, because there were strict requirements for that experiment ( https://www.sciencedirect.com/science/article/abs/pii/S0273117799009837 ) that a mere “air” bearing would not have.

    I don’t know whether an “air bearing” would work like a journal bearing, but perhaps some experimentation has been done in this field. Perhaps in free fall, some gas can perform like grease in a journal bearing. Perhaps teflon could sufficiently reduce friction. There are always possibilities, as Spock once said.
    _______________
    * Of course, at the end of the story, they surprise the audience with some unexpected, bizarre, out of the box solution that no one came close to thinking of during the brainstorming, but that’s Hollywood for you. Rather than help teach problem solving techniques, they would rather entertain us with the unexpected, satisfying, happy ending. *Sigh*

    ** See Figure 1. They used electrostatic effects to keep the sphere centered in the housing cavity. If you make it all the way to Figure 6, the drag-free proof mass was another sphere that, instead of being kept centered by electrostatic effects was kept centered by moving the satellite. This way, it was the proof mass that was in an orbit unaffected by aerodynamic drag, thus by making the satellite keep up with this proof mass, the whole satellite was in the orbit that it would have been in had there been no atmospheric drag.

  • Edward and Chris: I can’t locate it (though it is likely in my bibliography for The Universe in a Mirror) but I have read at least one paper about the gyroscope technology used on Hubble, and I am pretty sure it does not use ball bearings as you are discussing. That paper talked about the design improvements developed from the original gyros used when Hubble was launched.

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