Discussion
This looks like an interesting technology, although obviously not for manned flight
https://jalopnik.com/a-startup-just-launched-a-roc...
https://jalopnik.com/a-startup-just-launched-a-roc...
Sounds interesting but my first thought (before I got to the comments at the bottom) was the same as Tom's:
Tom Metcalf said:
I would assume that there is a counterweight to balance out the rocket so this thing doesn’t shake itself to pieces. That is all well and good until the rocket is released. Then the rotor has only the counterweight and will shake like mad until it stops. How would they get around this?
Can't see this being financially viable, at least on Earth.
Great engineering exercise, but number of issues:
1. Very limited payload capability (needs to be able to handle the G-Force, big one will be 10,000g).
2. Small payloads only.
3. Still needs an expendable rocket.
4. Lots of R&D to do.
5. Limited orbit insertion, fixed device, maybe they can add something to change the inclination, but more cost obviously.
With expendable rockets it makes sense, but as reusability is gaining traction, especially full reusability, it's going to make less commercial sense.
Great engineering exercise, but number of issues:
1. Very limited payload capability (needs to be able to handle the G-Force, big one will be 10,000g).
2. Small payloads only.
3. Still needs an expendable rocket.
4. Lots of R&D to do.
5. Limited orbit insertion, fixed device, maybe they can add something to change the inclination, but more cost obviously.
With expendable rockets it makes sense, but as reusability is gaining traction, especially full reusability, it's going to make less commercial sense.
I always loved they idea of a catapult to orbit launcher from reading the idea in Heinlein's classic, The moon is a harsh misstress.
This video https://youtu.be/Rb6sxy3f7VE?t=91 is the reality check that humans are just too squishy to enable that in any reasonable length of accelerator.
This video https://youtu.be/Rb6sxy3f7VE?t=91 is the reality check that humans are just too squishy to enable that in any reasonable length of accelerator.
It would be very interesting to know the two key technologies:
1) The release mechanism. Capable of holding huge forces but releasing cleanly and critically, repeatibly to within a resonably short period of time (ms timeframes, clearly trivial from an electronics and control perspective but v.difficult at full mechanical scale
2) The balance / inertial compensation mechanism. Rebalancing the rotating system in sync with the payload leaving the end of the arm sounds hard to me.
What is interesting is that their mock up photo's and renders show the control cabins right next to the launcher, which would be rather stupid as for anything envolving this much energy release..........
1) The release mechanism. Capable of holding huge forces but releasing cleanly and critically, repeatibly to within a resonably short period of time (ms timeframes, clearly trivial from an electronics and control perspective but v.difficult at full mechanical scale
2) The balance / inertial compensation mechanism. Rebalancing the rotating system in sync with the payload leaving the end of the arm sounds hard to me.
What is interesting is that their mock up photo's and renders show the control cabins right next to the launcher, which would be rather stupid as for anything envolving this much energy release..........
Max_Torque said:
It would be very interesting to know the two key technologies:
1) The release mechanism. Capable of holding huge forces but releasing cleanly and critically, repeatibly to within a resonably short period of time (ms timeframes, clearly trivial from an electronics and control perspective but v.difficult at full mechanical scale
2) The balance / inertial compensation mechanism. Rebalancing the rotating system in sync with the payload leaving the end of the arm sounds hard to me.
What is interesting is that their mock up photo's and renders show the control cabins right next to the launcher, which would be rather stupid as for anything envolving this much energy release..........
I was thinking about 2, I can't work out a way to do it without just dropping something from the other side of the arm at the same time you release the projectile. 1) The release mechanism. Capable of holding huge forces but releasing cleanly and critically, repeatibly to within a resonably short period of time (ms timeframes, clearly trivial from an electronics and control perspective but v.difficult at full mechanical scale
2) The balance / inertial compensation mechanism. Rebalancing the rotating system in sync with the payload leaving the end of the arm sounds hard to me.
What is interesting is that their mock up photo's and renders show the control cabins right next to the launcher, which would be rather stupid as for anything envolving this much energy release..........
The plus side is that your accurate release system will work on the both sides and you can mount something heavy close to the hub on the counter balance side and have much less KE to deal with.
For the full size application we have a 10 tonne rocket being launched at 2300m/s at a distance of 50m from the hub, if we dropped our counter weight from 2m away from the hub it would be doing 92m/s but it would mass 250 tonnes. This is quite a lot of kinetic energy to deal with, however it is not without precedent.
You could drop off something like a bag of sand or water that would exit the centrifuge via one of those blink doors and pound itself into a tunnel in the ground, or it could be a steel mass that catches an arrestor wire, the mass is about 7 times that of a carrier aircraft and it is going about 50% faster.
Looking at the design of the prototype system they do just look to have designed an absolute brick s
thouse of a bearing though. The out of balance forces are "only" 100,000 tonnes for the full system!I could imagine that they have a sort of dual bearing system where they have a long duration high speed bearing for running in balance which is then de-loaded (mounts are released) as the projectile is released. The out of balance bearing is then a massive hydro static bearing that isn't particularly low drag but only needs to operate for a fraction of a second as the counter weight is moved inwards to re-balance the rotor.
As a comparator I estimate that a piston journal bearing on a massive two speed diesel is resisting a few thousand tonnes of load (admittedly at a lower RPM) so given that the bearing on the arm could be 10 times larger in diameter it isn't totally unfeasible to resist these loads.
Edited by Talksteer on Wednesday 17th November 18:17
Aunty Pasty said:
Can't really see this working scaling up. The forces on the arm at the full size version will be tremendous not to mention the speed that the end of the arm will be travelling at. Any wobble and the whole thing will tear itself apart in a spectacular fashion.
They have literally built a 1/3 scale prototype and they can probably do basic analysis.The prototype is capable of around 5x the energy of the shot they did last week. This would be a 700-800m/s shot if they use the same projectile.
In my previous post I went through the mitigations, they have obviously picked one or more of them.
I would have thought that principal issues would be:
1: They have to build their 2 stage rocket and make it cost effective.
2: They have to create their own standard for satellite design.
3: They have to get it working before everyone designs around fully reusable architectures.
4: They have to get enough customers to justify their fixed capital and development costs.
Their 10 tonne 2&3 stage rocket is going to be about 80% the mass of Rocket Lab's electron. That costs ~$1-2 million in manufacturing cost. This should be cheaper as it is pressure fed but it's still got the same avionics and payload deployment equipment.
If they can get their cost down to their quoted $500k they will be the cheapest individual launch on the market. Much less than any other small sat launcher and we'll within the budget of all sortseof users.
They won't be cheaper in $/kg than a reusable or semi reusable rocket but if that rocket is anything less than fully loaded they will be comparable. You also send the payload directly to the orbit that you want and launch at a very rapid cadence, I could see small constellation operators really liking this.
It would also work really well on the moon in which case it would be by far the cheapest way to get Luna resources to LEO.
I think it’s amazing it is possible, when you look at the speed of the rotating object; when it lets go it won’t even be travelling straight, if you know what I mean, it’ll be sliding sideways? If it works low cost will obviously be the key attraction. But anyway, it leads me to think - just how much stuff do we want to send up into space? With all these companies working on different solutions.
Talksteer said:
I was thinking about 2, I can't work out a way to do it without just dropping something from the other side of the arm at the same time you release the projectile.
The plus side is that your accurate release system will work on the both sides and you can mount something heavy close to the hub on the counter balance side and have much less KE to deal with.
For the full size application we have a 10 tonne rocket being launched at 2300m/s at a distance of 50m from the hub, if we dropped our counter weight from 2m away from the hub it would be doing 92m/s but it would mass 250 tonnes. This is quite a lot of kinetic energy to deal with, however it is not without precedent.
You could drop off something like a bag of sand or water that would exit the centrifuge via one of those blink doors and pound itself into a tunnel in the ground, or it could be a steel mass that catches an arrestor wire, the mass is about 7 times that of a carrier aircraft and it is going about 50% faster.
Looking at the design of the prototype system they do just look to have designed an absolute brick sthouse of a bearing though. The out of balance forces are "only" 100,000 tonnes for the full system!
I could imagine that they have a sort of dual bearing system where they have a long duration high speed bearing for running in balance which is then de-loaded (mounts are released) as the projectile is released. The out of balance bearing is then a massive hydro static bearing that isn't particularly low drag but only needs to operate for a fraction of a second as the counter weight is moved inwards to re-balance the rotor.
As a comparator I estimate that a piston journal bearing on a massive two speed diesel is resisting a few thousand tonnes of load (admittedly at a lower RPM) so given that the bearing on the arm could be 10 times larger in diameter it isn't totally unfeasible to resist these loads.
They don't need to drop anything.The plus side is that your accurate release system will work on the both sides and you can mount something heavy close to the hub on the counter balance side and have much less KE to deal with.
For the full size application we have a 10 tonne rocket being launched at 2300m/s at a distance of 50m from the hub, if we dropped our counter weight from 2m away from the hub it would be doing 92m/s but it would mass 250 tonnes. This is quite a lot of kinetic energy to deal with, however it is not without precedent.
You could drop off something like a bag of sand or water that would exit the centrifuge via one of those blink doors and pound itself into a tunnel in the ground, or it could be a steel mass that catches an arrestor wire, the mass is about 7 times that of a carrier aircraft and it is going about 50% faster.
Looking at the design of the prototype system they do just look to have designed an absolute brick s
thouse of a bearing though. The out of balance forces are "only" 100,000 tonnes for the full system!I could imagine that they have a sort of dual bearing system where they have a long duration high speed bearing for running in balance which is then de-loaded (mounts are released) as the projectile is released. The out of balance bearing is then a massive hydro static bearing that isn't particularly low drag but only needs to operate for a fraction of a second as the counter weight is moved inwards to re-balance the rotor.
As a comparator I estimate that a piston journal bearing on a massive two speed diesel is resisting a few thousand tonnes of load (admittedly at a lower RPM) so given that the bearing on the arm could be 10 times larger in diameter it isn't totally unfeasible to resist these loads.
Edited by Talksteer on Wednesday 17th November 18:17
Imagine a weight on the release arm. At the instant of projectile release, the weight is allowed to move outwards, leaving the new centre of mass at the hub.
AW111 said:
Talksteer said:
I was thinking about 2, I can't work out a way to do it without just dropping something from the other side of the arm at the same time you release the projectile.
The plus side is that your accurate release system will work on the both sides and you can mount something heavy close to the hub on the counter balance side and have much less KE to deal with.
For the full size application we have a 10 tonne rocket being launched at 2300m/s at a distance of 50m from the hub, if we dropped our counter weight from 2m away from the hub it would be doing 92m/s but it would mass 250 tonnes. This is quite a lot of kinetic energy to deal with, however it is not without precedent.
You could drop off something like a bag of sand or water that would exit the centrifuge via one of those blink doors and pound itself into a tunnel in the ground, or it could be a steel mass that catches an arrestor wire, the mass is about 7 times that of a carrier aircraft and it is going about 50% faster.
Looking at the design of the prototype system they do just look to have designed an absolute brick sthouse of a bearing though. The out of balance forces are "only" 100,000 tonnes for the full system!
I could imagine that they have a sort of dual bearing system where they have a long duration high speed bearing for running in balance which is then de-loaded (mounts are released) as the projectile is released. The out of balance bearing is then a massive hydro static bearing that isn't particularly low drag but only needs to operate for a fraction of a second as the counter weight is moved inwards to re-balance the rotor.
As a comparator I estimate that a piston journal bearing on a massive two speed diesel is resisting a few thousand tonnes of load (admittedly at a lower RPM) so given that the bearing on the arm could be 10 times larger in diameter it isn't totally unfeasible to resist these loads.
They don't need to drop anything.The plus side is that your accurate release system will work on the both sides and you can mount something heavy close to the hub on the counter balance side and have much less KE to deal with.
For the full size application we have a 10 tonne rocket being launched at 2300m/s at a distance of 50m from the hub, if we dropped our counter weight from 2m away from the hub it would be doing 92m/s but it would mass 250 tonnes. This is quite a lot of kinetic energy to deal with, however it is not without precedent.
You could drop off something like a bag of sand or water that would exit the centrifuge via one of those blink doors and pound itself into a tunnel in the ground, or it could be a steel mass that catches an arrestor wire, the mass is about 7 times that of a carrier aircraft and it is going about 50% faster.
Looking at the design of the prototype system they do just look to have designed an absolute brick s
thouse of a bearing though. The out of balance forces are "only" 100,000 tonnes for the full system!I could imagine that they have a sort of dual bearing system where they have a long duration high speed bearing for running in balance which is then de-loaded (mounts are released) as the projectile is released. The out of balance bearing is then a massive hydro static bearing that isn't particularly low drag but only needs to operate for a fraction of a second as the counter weight is moved inwards to re-balance the rotor.
As a comparator I estimate that a piston journal bearing on a massive two speed diesel is resisting a few thousand tonnes of load (admittedly at a lower RPM) so given that the bearing on the arm could be 10 times larger in diameter it isn't totally unfeasible to resist these loads.
Edited by Talksteer on Wednesday 17th November 18:17
Imagine a weight on the release arm. At the instant of projectile release, the weight is allowed to move outwards, leaving the new center of mass at the hub.
1: Conservation of rotational inertia, as you drop the mass down the arm you will increase the moment of inertia of the whole system and slow down the rate of rotation very rapidly. As the mass travels up the arm it will apply a massive bending load
2: For arguments sake if the mass was the same mass as the projectile it would accelerate up the arm until it left the top with the same radial velocity as the tip of the arm.
3: We would then have to stop this balance weight at the top resulting in an even greater imbalance briefly to the rotor
There is no way of moving the balance without at some point having to react that load on the bearing which means you have to design it to operate out of balance at least briefly, unless that is you drop mass to balance the rotor
To put this in perspective, to get a 200kg payload into orbit with a two stage rocket with pressure fed tanks and ~300s isp we are looking at a 5-10 tonne vehicle when boosted to 2.3km/s. This means that we have an out of balance force of 50-100,000 tonnes.
Lets say we use hydraulics to shift the counterweight on the other side in a few meters (probably be easiest to just shift whole arm). We need to apply a force of 50-100,000 tonnes. Even with 4000 bar ultra high pressure hydraulics we need cylinders with an equivalent diameter to 5m!
We could reverse this and instead drop at very heavy weight say 100 tonnes 5m, this would cut down on the bending moment problem. We could release the mass let it free fall a short distance before catching it with a force equal to the out of balance force before bring it to a stop at 5m radius. We would still need a massive hydraulic cylinder or crush core to do this and there are still issues of shock loads and damping.
Having done some more calcs I think the only option for for a mass drop would be a solid block of steel (and therefore catch it at least on an operational system as you are chucking £100,000 of steel), the container required to contain a liquid would have to be far too thick to throw away with the liquid and we cannot release a liquid into the vacuum chamber.
The prototype doesn't really tell us much about how they will deal with the out of balance loads as the bearing loads are in the range of hundreds of tonnes and as such within the loads seen in conventional bearings.
eliot said:
thunderfoot’s take on it:
https://youtu.be/9ziGI0i9VbE
Not even going to watch (don't feed the trolls and the Youtube algorithm does't catch contemptuous views), the guy is pompous and not actually an engineer.https://youtu.be/9ziGI0i9VbE
He "debunks" a whole load of marketing lead fluff projects but when he actually turns his attention to projects which are ambitious but funded and being worked on by large amounts of competent engineers he is very Duning-Kruger and his limitations as a thinker/engineer shine through.
I don't think he understands the engineering process as he frequently criticizes prototypes and engineering tests for not being essentially a finished product.
Here is a point by point take down of his Hyperloop video from a few years ago.
https://www.youtube.com/watch?v=kx52A-v65Q8&li...
I used to do gas turbine design before I went into nuclear so I well understood than he has no idea what he is taking about with his view of pressure in terms of absolute numbers and not as a function of pressure ratios.
eliot said:
So you think the hyperloop will be built, run in a vacuum at the speeds stated or just that TF’s analysis of it wrong?
To me the hyperloop and indeed this spin launch dont seem to pass the sniff test - but i’m not an engineer or scientist.
Thing these days the engineering is pretty irrelevant tbh. We can pretty much engineer anything, the limiting factor is the cost and reliability.To me the hyperloop and indeed this spin launch dont seem to pass the sniff test - but i’m not an engineer or scientist.
Take the hyperloop, today, we are struggling to install conventional rail, which needs some concrete sleepers and a bit of ballast to build the track. If we can't make that work finanically speaking, how does anyone propose a system of hugely greater cost and complexity could be made to "work"??
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