Spacecraft Gyroscopes And Reaction Wheels. You Can Never Have Enough

It’s amazing to think there are telescopes up in space, right now, directing their gaze at distant objects for hours, days and even weeks. Providing a point of view so stable and accurate that we can learn details about galaxies, exoplanets and more.

And then, when the time is up, the spacecraft can shift its gaze in another direction. All without the use of fuel.

It’s all thanks to the technology of reaction wheels and gyroscopes. Let’s talk about how they work, how they’re different, and how their failure has ended missions in the past.

06:49 Scientists May Have Figure Out Why So Many Spacecraft Were Failing –

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Kepler Reaction Wheel Failure Cripples Spacecraft, but Mission Thrives


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  1. I am sure your getting things a bit mixed up, Gyroscopes dont keep the satellite in position, they measure changes in position and relay that to the reaction wheels to make a change. I think what you mean is that the crystals have replaced the gyroscopes ?

  2. To rotate the spacecraft, why do the wheels need to be continuously spinning? What if instead there was a just a very heavy wheel that the spacecraft would spin/rotate around when needed, stepper motor style? Do continuously spinning wheels give finer control or require less energy to use?

  3. You say crystals are used to detect changes in rotation, fine but how they correct for it? use reaction wheels again ??? sorry I think something has been left out

  4. NASA could have built the Hubble out of erector set pieces. THINK of the time, effort and money saved not having to machine, fabricate and weld parts and doodads.

  5. Aren't we so lucky that the men and women of NASA and other space agencies and scientists work so hard to advance our species by searching for the real answers about our universe rather than accepting the bronze age answer of "god did it"? So sad that so many, especially in America, deny science on a daily basis for those bronze age fairy tales.

  6. So, gyroscopes resist movement because of their momentum – effectively detection AND correction in one? The resonant crystal is an incredibly accurate and reliable way to detect motion – but what then corrects that motion?

  7. Hey Fraser, Just learned that Sagittarius A* flared up again with record brightness 75 brighter and 40 times brighter than our sun. Can you please make an episode on this phenomenon? I got extremely excited about learning about this event. Thanks!

  8. Fraser, I love your videos. About that JWST orbit though, why and how? Why make it orbit several (10^5) km away from L2? It won't be in earth's shade, which if it was, would make the heat shield easier. And how can it "orbit" L2? I understand L2 as gravitationally meta-stable, like a ball on a hill. When you are that far away from L2, what provides the restoring force to keep it from rolling down the gravitational hill?

  9. Hi Fraser,

    I have a question for your question show. When communicating over the Internet, HTTP is used to ensure that all parts of a message have arrived. But how does communication with space probes like New Horizons work? As far as I understand, it took several months for all the images and data to reach Earth as it passed Pluto. What kind of method / protocol is there to make sure that all data arrives, regardless of distance and interference? Many probes have also deliberately crashed and sent data on the way down and then you cannot ask them to send the message again. 😉

  10. Serious Question: How many events of Universe we might have lost because of delay in James Webb Telescope?

    They say out Human history is like an eye blink on universal Time scale.

    But Neutron Star collision which we detected was of ?short duration only.

    Is time of Universe scale so slow that many Events last for millions of years for us to detect and analyze or
    there are also events that last for very short time.

  11. Can you do a video about heavy earth movers in outerspace? Does NASA work with Caterpillar (or any other company) to make a Bulldozer, etc. that will work on the Moon or Mars? It seems to me, if you want to build a permanent settlement , you must be to work the soil.

  12. I like your references to other people's content. It feels like a friendly community here 🙂

    On Wikipedia's article "Kepler: History," it mentions there was more noise from the stars and spacecraft than was expected, and thus the mission needed to be extended just to meet it's initial goals. What was this issue? Can you frame this in terms of Type-G stars and exoplanets with Earth type orbital periods?

  13. what if we had refueling orbits? private companies could develop standardized docking mounts that satellites can incorporate in their design.. LIke gas stations, space missions could pay a premium to refuel in space, thereby extending their mission.

  14. After all this time and all that money and all of defense contractor maleficence, stupidity and just plain laziness…. its hard to believe that JWST wont be a disappointment, if not a spectacular failure…..

  15. The 'reaction wheel' debacle kinda reminds me of the Venera Lens Cap debacles…
    Speaking of which, I wonder how many Soviet engineers were executed over those whoopsies. Maybe somewhere on their gravestones it says "Couldn't work a lens cap to save his life…"

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