haha Lucky me I actually had a wine glass ready for the experiment!

Thanks, I hope you enjoyed it. :-)

And don't forget about the Unicorn Dreams.

Marianne Williamson approves that technology

Great, I"m glad you enjoyed it!

Yeah, it's best to just link to Scott and then get out of his way. :-)

Thanks for watching!

Yeah, it was fun to research that part, I actually didn't know how they worked at all before digging into it.

@@frasercain I find the reaction wheels especially fascinating. Solves the cold gas thruster fuel issue from back in the day.

I thought “...powered by unicorn dreams” explained it nicely. 😂😁😳🤡🤪😜

Oh yeah, it's a monster.

Thanks a lot!

Glad you enjoyed it.

I can't even think about it. It's going to succeed! :-)

Don't worry. It'll be like in the movie Contact. They're building AT LEAST two of them simultaniously if anything goes wrong...

If it blows up in 2027, we might get a replacement by 2067.

Of course, we now know that the launch, deployment and entry into service were epic beyond even the wildest of dreams. I too was glued, could hardly bear to watch it! NASA did an analysis of the launch provided by Ariane 5, and the accuracy was astonishing. For a mission with a required lifetime of 5 years and a hoped-for 10, the launch it got has given it a fuel life of 20years. If ever there were an example of scientists / engineers rightly saying, "wait and see", this has surely got to be it. Their combined efforts turned a $10billion 5 year science program (the minimum mission aim) into a $10billion 20 year science program (if it lasts, which it probably will). If it gets to the 20 year mark, that's 4 times as much science, or 25% of the price per astronomical observation / paper / finding compared to that authorised by the funding bodies. It's a bit like spending only $2.5billion for 5 years' lifetime. Had anyone said JWST was going to come in at the $2.5billion per 5 year mission duration price point in the run up to launch, there would have been much disbelief! Ariane's gift to the JWST, and the telescope's own engineers' efforts in making hundreds of little things deploy perfectly really, really paid off. I'm deeply impressed. With the reaction wheels, I understand that a fairly recent discovery was made. The failures are probably due to electrostatic discharge. As the craft spends time in space, protons (from the solar wind) douse the spacecraft. Some lodge in the structure, but the point is that the reaction wheels (that are usually on very good bearings) are in effect electrically insulated from the rest of the craft by the grease in them. As the protons build up, a voltage difference also builds up, and eventually is able to spark across the thin smear of grease separating the wheel from the spacecraft. This instantly welds the bearing together. The inertia of the wheel just as instantly breaks the weld. Now, the bearing surface has a small defect. And so on. The fix? make electrical contact between the wheel and the spacecraft often enough to prevent discharge across the bearing. Simples! I've no idea if JWST benefitted from that, but hopefully wheel failure starts to become a thing of the past.

I guess once you're down to to sub-micron accuracy, you can use ion sputtering and lasers to add or remove atoms where necessary!

Thanks for watching!

They continuously spin. They need to be used in a way that averages out their spin-ups and spin-downs or fuel needs to be used to allow them to get back into their operational sweet spot. This is called desaturation if you want to look it up and learn more.

They're constantly spinning, but then they change the speeds on the different wheels to get the torque they need to shift into a new direction.

Law of conservation. It takes way more energy to spin up/down the wheels, while it takes less to keep them spinning and just change the amount of spin rate as needed to produce the necessary force vectors to enable reorientation of the spacecraft.

I think the current launch date is pretty safe at this point.

MrGoesBoom the thing about JWST is the technology it’s going to use and the engineering to deploy. Had to be developed most of it did not exist before JWST. So a big R&D development was needed.

I guess you mean like the new technology in the USS Ford and the F-35!

@@nightlightabcd No, old-ish technology that successfully performed for 20 years after launch.

No they're switching the type of gyros used. Fraser didn't cover the reaction wheels on the JWST. You need mass to store momentum to react with - resonating quartz hemispheres won't do that. Using magnetic bearings, I would have thought that reaction wheels would last centuries, unfortunately it seems not to be the case.

Andy Lee Robinson Frazer didn’t cover it however they changed the type from metal inline reaction wheels to a new ceramic and it appears the new ones don’t fail for the same reason

I mentioned the reaction wheels on JWST. They're the same as the ones on the Chandra X-Ray observatory. It's the gyros which are based on crystals, the same tech as Cassini.

They're not reaction wheels, they're gyros, they just help detect the drift.

@@frasercain I found that a bit unclear. The problem with the old probes was wear on the reaction wheels. This technology seems to be about measuring motion instead of causing motion. That doesn't sound like it solves the issue with the reaction wheels.

Sure, Phobos would be a great place to build a base to travel down to the surface of Mars and back up again. Not that useful for going anywhere deeper into the Solar System.

@@frasercain And it would be great for long term in-situ resource utilization because in about 50-100 million years the Mars colonies are not going to want it falling onto them.

Very little. There would be some stars closely orbiting Kevin that, depending on where they were in their orbits, could get launched on a trajectory careening through the galaxy or settle down into an orbit around the new barycenter. The galaxy on the whole, however, massively outsizes Kevin. 1.5 trillion to 4.3 million. That's more than 5.5 orders of magnitude. 1:350,000

Markle2k - Its name is “Kevin”?

@@BugRibThe reverse Python seems to think so. It's a bit less clinical than Sag A* so why not humor him?

Hah, the Kevin reference is from an old video that we did. We wanted to give the black hole a better name. If Sag A* disappeared it wouldn't make really any difference to the Milky Way. It's not an anchor, the dark matter halo that surrounds the Milky Way is what really holds it together. Sgr A* is less than 1% the mass of the Milky Way. kzfaq.info/get/bejne/fsCiaceC3Jmxpmg.html

Engineering is capable of incredible things. You just need someone to pay for it to be designed and build.

It's surrounded by electrodes that keeps it resonating.

I mention Everyday Astronaut's raptor engine video in the next one. Always happy to send people over to other articles and videos when I can.

You mention what other people you got information from, they will hear of it, and they will mention you. This is how things work on the internet.

I'm not sure precisely how, but I would guess it has something to do with the amount of energy it takes to keep the wheel spinning.

It’s always too tempting to add hardware upgrades. And then you are suddenly building a completely new probe ;)

Sometimes called “Mission Creep”. Just one more sensor over here, and we should also add a redundant solar cell over there, and best if we also increase the size of the antenna just a wee bit... Unrestrained, this tendency can turn a golf cart design into an 18 wheeler “semi” 😳.

It would certainly be cheaper to build a second version of a telescope, but then it wouldn't allow you to answer the new scientific questions that astronomers have. It's always a balance.

It's using the wheels that Chandra and Aura are using. So a different manufacturer

@@frasercain Magnetic bearings?

There are two types of gyros discussed in this video. Large mechanical gyroscopes can be used to adjust the attitude of a spacecraft. But smaller HRG's discussed in this video are strictly sensors, similar to ring laser gyros. It seems that this video confuses those two.

You don't, Webb has reaction wheels too

,@@frasercain yes six reaction wheels which are mounted on vibration isolators like in Chandra X-ray observatory.

prusak26 Hubble is a leftover Cold War spy satellite. Just different optics (which were wrong) and not pointing to space. They literally built the space shuttle program around them to launch and service them. I bet there’s a bunch of clones out there where you just need to swap the optics and flip them around if Hubble broke down. Hubble is outdated but free to use so interesting things are being done with it. A lot of military R&D money went into it, probably more than NASA’s annual budget because spy satellites were crucial at that time.

@@Hamachingo That was my hypothesis too, that the mirror was focused to the Earth surface and not infinity. I appears that turned out to be significant!

Hamachingo the x-35 program is a mini shuttle but it’s secret what it does in space for years at a time.

We just covered it on Universe Today: www.universetoday.com/143150/milky-ways-black-hole-just-flared-growing-75-times-as-bright-for-a-few-hours/

@@frasercain Yeah, I have already seen it. It's awesome. Thanks!

Yes, they're used to turn in any direction. As long as you have three, you can turn in each axis.

Here's an article from NASA that explains the protocols they use: www.nasa.gov/content/dtn

@@frasercain 404 Page Not Found :)

Yes, we're still waiting for the image from the center of the Milky Way.

Interesting, I'm not familiar with that tech.

Now i know what i didn't see: the flow resistance when the fluid is in a pipe. That would loose too much energy to make it viable...

We've done a few already, but I'll chat with him.

I'm not sure there's a separate braking mechanism, they just change the spin rate of the electric motors.

Someone's a fan of resonating crystals.

@@frasercain you have no idea

I was going to cover them too, but it was making the video a little long

Fuckin' oath, mate!!! For starters, NO nation on Earth needs to spend more than 100B on their military. For the U.S., that means an extra 500 billion per year for space tech. For China it's an extra 20 billion (and increasing). Other nations can also limit their military spending and devote the rest to space tech. Governmental spending tells you- in no uncertain terms- what that government (and by extension, the society they govern) really cares about. To actually see a shift in governmental spending priorities, we'd need to convince whole societies to care more about exploring space than killing other people. THAT is gonna be a hard sell, especially to the usa...

I think we always feel like things are too slow, but really, the pace is accelerating these days.

JWST will be using thrusters to keep itself perched at L2. That's why it only has a lifetime of about 10 years. It's at L2 because this keeps the Earth, Moon and Sun all in the same area, so it can keep them all shielded from its observations.

I mentioned in the video that James Webb has the same kind of reaction wheels as Chandra. It just has a different kind of gyros than Hubble.

Ha Ha you would be less wobbly

Planets will orbit the common center of gravity in a system, so you need something there, like a star. But there could be rogue planets which have been kicked out and they're wandering the galaxy without a star.

You still need the reaction wheels to keep it oriented.

@@frasercain so in other words they are just wearless IMUs, wich is nice, but they in no way do anything to mittigate the wear problem on the reaction wheels.

@@frasercain Thanks! - so, since the reaction wheels are needed anyway, this does away with the need for the gyroscopes, so at least 3 less moving parts to fail :)

No, as long as the 4 are all in different orientations, then you can get the torque you need if one goes down.

They do. For the smaller spacecraft, they only have the reaction wheels.

Yep, works brilliantly. They're called "rocket engines".

@@sharkuc lol

Thanks a lot. But only do it if you can afford it. :-)

@@frasercain I will be able to by the end of September. Your videos are great. I need more stuff

The HRGs? None have ever worn out.

Yup. You would rotate but you wouldn't go anywhere.

@@frasercain what you mean you wouldn't go anywhere? my trajectory wouldn't change you mean? I know that but would I turn around or slow/speed up my rotation?

We talked a bit about about this in this video: kzfaq.info/get/bejne/Z9eoY7p7lrLaeZc.html

There's no backup. :-(

Likely a flat earther or moon hoax believer or some nut like that

Either a flat earther or someone who made a reaction wheel for the Kepler.

they don't know how to English and they get confused: I like dis - I dis like

There is a high instance of mental disorders in the populace. Some people are bound to be negative, due to internal reasons, rather than anything to do with the video.

There are always a few space-haters that show up.

The more massive the spacecraft, the more massive you want your reaction wheels to be able to turn it.

This might be a solution to the problem. They only recently discovered what's causing the reaction wheel failures.

You are storing angular momentum in spinning reaction wheels. You cannot de-spin the wheel without spinning up the satellite (conservation of angular momentum) unless you use RCS to counter the spin up of the satellite. This de-saturating of the wheels has to be done periodically using up RCS fuel.

Spinning up the satellite would be the point, at least until the satellite has reached the target alignment, and then you reverse and stop. For example, let's say a spacecraft has a flywheel as massive as the rest of the craft. Then, motors on board the craft rotate the wheel 180° and stop. Wouldn't the resulting action-reaction be that the craft is now pointing 90° opposite to the turn, and the the wheel pointing 90° in the direction of the turn? Of course, sending up so much deadweight would be a bad idea, but the same idea should be fine with a less massive wheel; the wheel would just need to be spun more. What am I missing?

You'll see it. NASA's last investigation into Northrop Grumman was pretty intense, and they've got a launch date they're certain about - 2021.

Launch was originally planned for 2007.

If there were a set at either end of the spacecraft, it may rotate around that point and allow it to move linearly by flipping around alternating sets of reaction wheels.

I think the rotations would combine in place and wouldn't alter the linear velocity tho

Yes! Set Protonic Power to full, Aim it at the galaxy! Mah Ha Haa!

@@alan2here And I'll call Marvin the Martian to get his Uranium PU38 Space Modulator.

Me too. But the reaction wheels it's using seem to have fewer problems, so let's hope.

Nice. Way beyond my KSP skillz.

L1/2/3 are metastable, which means that you need less fuel to remain in a Lagrange point, but you'll still drift away. It all depends on the orbits of all the objects and the interactions.

I imagine the greater the mass of the object, the more resistant it will be to any disturbances that push it away from the L-points.

Nope, the astronauts can really only stay on the station for a few months. The Soyuz return vessels have an expiration date before they're not considered safe.

I talked about gyros and reaction wheels in this episode.

The crystal is for keeping it fine tuned, it still has reaction wheels for large movements.

I haven't been able to find out anything more about them.

​@@frasercain I probably shouldn't make jokes about such things. I expect Lavrentiy Beria would have indeed executed them for embarrassing the Soviet Union. I mean, their engineers were real-life Macgyvers, able to (in the 70s) take a shoebox, a necktie, a rusted pipe and some pebbles, and turn it into a nuclear submarine with super-cavitatiing torpedoes that can travel at 200 knots!! The poor schmucks were given sub-standard turds and were expected to be able to weave it into gold. Lens-Cap-Gate was just an unfortunate series of events that would probably have been an amusing anecdote for everyone, had it not been so expensive. So, 'yeah,' I think Lavrentiy Beria happened to them. One unfortunate engineer after the other, shuffled off for the financial loss as well as any potential loss of the kind of international prestige that the Cold War embodied... TLRD:-----> Thanks for looking into it. I'm convinced- unfortunately- that many of the engineers assigned to the Venera missions would have suffered from impossibly high rates of fatal accidents.

Hah, that's the very next episode. Stay tuned

@@frasercain 🙌🙌

Ali Syed I think that by the time there ready for a refuel there would be so much better technology out there to replace them. So just let them deorbit and put up next best thing.

It's never enough.

My guess is a minimum of 2/two engineers is required for 4/four or less reaction wheels, and an extra engineer for every 2/two wheels after that. (5/five OR 6/six wheels would need 3/three engineers) But this would only be the case for up to ten wheels or so.

@@superdupergrover9857 don't forget the 20 people standing around watching for no good reason you see in every video of a spacecraft of any sort been built cheers james D

Is this a space version of the lightbulb joke?

@@superdupergrover9857 I guess that answers my question why don't they use more spare reaction wheels for a contingency in telescopes!

Almost certainly.

Why do you think that a limited speed of gravity makes gravity non-gravitational?

@@Theo0x89 Om thinking about if something happens at one end of a galaxy it can take 100 of thousands of years to react with the rest of the galaxy and it just seems strange to me that the galaxy can form and rotate.

​@@trattpersson6366 Sure, the gravity of an object in the galaxy takes a long time to reach a star somewhere else, but the sum of the gravitational forces acting on the star stays pretty much the same as long as it doesn't get too close to another star and no large disturbance like a galaxy collision occurs.

Now that I think about the huge amount of time everything takes in cosmic scales it kinda makes sense. I think I get confused with my human perception of time.

It's thought that they scooped up all the material in place and then drifted outward.

Aww, poor Skylab.

Andrew Pusey The crystals are both the instrument and the reaction mechanism.

Like... the Wrestler? Yikes!

@@frasercain Yh, u look strong enough, get 2pac california love as your entrance music and get fired up. U may win

From memory, I don’t believe so. Something about aperture, focal length and so on.

They've done it for calibration, but the telescope moves too quickly to actually return any usable pictures.

The theme continues. :-)

Noooo!

In case you're not trolling, those are kaleidoscopes. Absolutely not the same thing as gyroscopes!

@@ahaveland Trolling? It's a joke.

To get good images you need to hold the telescope steady. Imagine you have a camera and you want to take a photograph. If you hold it on target, you will get a better exposed and focused shot compared to holding it by the strap and swinging it around.

Until after it launches.

I thought it was mostly about how reaction wheels work, how they're different from gyros and the new tech that'll be in James Webb. Was there a part that needed more clarification?

I hope they give me credit for the Unicorn Dreamliner spacecraft.