Limits to accelerate a spacecraft by spinning it in a circle

Main Question or Discussion Point

The basic concept is to have your space probe(s) - likely nanocraft [1] on a spinning object in space which allows you to preserve the momentum you give it while accelerating it faster. Then once you are at a speed you can simply release the nanocraft in the direction you want it to go in.

More specific example:
Spin a 10m wheel at 30m/s^2 until it reaches say 10,000 m/s on the outside of the wheel. On the edge of the wheel are 4 nanocraft that are released when it reaches that speed.

If there are limits with having a full object spin we could have a series of tracks possibly accelerating the next one via maglev, then stabilizing the previous ones to be able to accelerate the outer one again.

I'm trying to better understand the feasibility of these ideas, and I am guessing some one has already thought of them and evaluated them. Would love if anyone can point me in the direction of more information if this has already been evaluated.

If not, I'd like to start learning the limits so I can evaluate it, my questions so far:
1. How fast can you spin something in space? The only obvious limit I've gotten so far would be if it's a single mass object spinning you don't want the middle to get to the speed of light - I'm guessing there is another limit somewhere?
2. How fast can we practically spin something in space using a motor (flywheel in space*)?
3. What kind of problems do we need to watch out for on our nanocraft so they will keep working and be able to release at the correct time?

Maglev/track idea introduces new questions like:
4. Will the tracks stay stable enough accelerating in opposite directions to not require power to keep them close together (I don't see a remotely practical way to power the outside track)
5. At what velocity would maglev acceleration no longer be effective at? Can we get to Project starshot speeds? At what rate does it decrease?
6. My estimate of the acceleration I can get from maglev was 30m/s^2 from reading that many trains could cause several G forces of acceleration - need a better number here.

I also might not even know the right question to ask, so feedback very appreciated! Happy to break this up into subforums, but figured it made sense to start here.
Thanks!

[1] This entire concept was inspired from their idea described here: http://breakthroughinitiatives.org/initiative/3
* I've found a few papers about flywheels which seem to be the closest thing, but I've never found them describing the speed on the outside of the wheel (or the size for that matter). Maybe I'm just looking for the wrong terms?
 

Answers and Replies

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Spinning disks are limited to about 1-2 km/s with current materials, if you try to spin them faster they break. Carbon nanotubes might get a bit more speed. This does not depend on the disk radius and tapered disks don't reach much more either.

Accelerating something on a maglev track doesn't have this limit, but very high accelerations are still problematic with it. The acceleration to stay on the track can be significantly higher than realistic accelerations to increase the speed.
 
CWatters
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Bear in mind conservation of momentum applies. How do you propose to spin the arm? You could use solar panels and contra rotating arms but that still means if you fling one nanocraft directly away from earth you push the launcher in the other direction (eg towards earth). If you want to keep reusing the launcher you need to keep pushing it back to its original orbit.

The cost of a launch usually depends on the mass. You want to minimise the amount of "wasted mass" needed to get the "wanted mass" to the destination.
 
Mech_Engineer
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Spin a 10m wheel at 30m/s^2 until it reaches say 10,000 m/s on the outside of the wheel. On the edge of the wheel are 4 nanocraft that are released when it reaches that speed.
In this example, the acceleration at the outside of the disc would be about 20,000,000 m/s^2, or about 2 million g's. This is easily the biggest limitation, you'd have to increase the diameter of the disc by several orders of magnitude to make it feasible for orbital speeds.
 
etudiant
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Bear in mind conservation of momentum applies. How do you propose to spin the arm? You could use solar panels and contra rotating arms but that still means if you fling one nanocraft directly away from earth you push the launcher in the other direction (eg towards earth). If you want to keep reusing the launcher you need to keep pushing it back to its original orbit.

The cost of a launch usually depends on the mass. You want to minimise the amount of "wasted mass" needed to get the "wanted mass" to the destination.
Would it make sense to launch pairs of nanocraft in opposite directions, to address these concerns?
 
Would it make sense to launch pairs of nanocraft in opposite directions, to address these concerns?
That's what I was thinking. I was also not planning to try this anywhere near a planetary body.
 
CWatters
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Might work but which is more useful in orbit... 1kg of fuel or 1 kg of mass you only sent up so you have something to throw in the wrong direction (which might be downwards)?
 

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