centrifugal reaction drive (NEW ENGINE TYPE)

[MC.STEEL]

After looking at spining habitation cans to provide gravity,it struck me!As the spinning can accelerates stuff,then why not use it for flinging reaction mass!

And without further ado i present to you the:

centrifugal reaction drive^tm (suggest a better name if you come up with one)

This drive works by (yes you guessed it) accelerating a liquid through means of centrifugal force.

I have made some calculations (with spincalc of course) that the characteristics are for an initial prototype of:

4 meters radius of can

428 RPM of angular velocity.

that achieves a Centripetal Acceleration of 8035 m/s (i am assuming that the CA will be the exhaust velocity).

The exhaust velocity is around that of a solid core NTR! not bad eh

As for thrust,the amount of reaction mass being injected into the engine will effect its trust.(it may or may not effect the ISP)

And as some final words.I am sorry if my calculations are flawed in some way.Also sorry for the scruffy sketch i just scribbled it in real quick.

Edited April 27, 2014 by MC.STEEL

[SargeRho]

...It's a rocket engine without the combustion stuff.

[MC.STEEL]

...It's a rocket engine without the combustion stuff.

More like a washing machine turned into a rocket engine

[DerpenWolf]

Funny thing is I've though about using this method for propulsion as well (also using a similar technique for magnetically accelerating projectile to stupid speeds before release, basically a particle accelerator that accelerates a steel ball). Such a device would likely need a pretty tough structure and probably a good amount of equipment to get it going fast enough (pretty dang fast) but apart from that it could probably work

Edited April 26, 2014 by DerpenWolf

[Tex_NL]

So what you're suggesting is basically a centrifugal pump on steroids?

[R0cketC0der]

I think the tangential velocity is the exhaust velocity of this so you'd only get an exhaust velocity of 180m/s. To get an exhaust velocity of 8035m/s you would need too have 19128 RPM and a material that doesn't break at 1.5 million gees.

[MC.STEEL]

Now why would it be tangential velocity (I utterly fail to understand what " tangential velocity" means)?

Please explain.

[xenomorph555]

How would you connect the injection, exhaust pipe to the wheel without them spinning?

How to solve liquids floating in the middle of the wheel pipes?

Size/weight problems.

[MC.STEEL]

How would you connect the injection, exhaust pipe to the wheel without them spinning?

How to solve liquids floating in the middle of the wheel pipes?

Size/weight problems.

The injection pipe will be connected to the external hull and not the centrifuge itself witch has side walls that do not close it off.

The water will be fed in with slight pressure.(i hope it will stay on the surface long enough to catch inertia)

Or maybe even angle it

Size and weight will not be a problem (except if you build a really big one but that is unececary because you can spin it really fast)

[ZetaX]

How do you even get those >8km/s¿ The correct value is indeed the tangential one, but I do not even see where you get your number from.

[Tex_NL]

The injection pipe will be connected to the external hull and not the centrifuge itself witch has side walls that do not close it off.

The water will be fed in with slight pressure.(i hope it will stay on the surface long enough to catch inertia)

Or maybe even angle it

Size and weight will not be a problem (except if you build a really big one but that is unececary because you can spin it really fast)

If you're going to feed in liquid at the outer edge it won't work. The pressure involved with a 8+km/s exhaust will be insanely high. If you're going to feed in liquid at an even higher pressure you're better off feeding that straight into the exhaust. Best place to feed in new liquid is at the center allowing it to be flung outward and creating a low pressure at the center sucking in even more liquid.

[Guest]

The exhaust velocity would indeed be around 180m/s. That would give Isp of about... 18s. Centripetal acceleration doesn't convert to EV directly. It doesn't even have the right unit, you gave it in m/s, but the unit of acceleration is m/s^2. There's something wrong in there.

Also, when you've got 18s Isp, CGTs give more than that. So you're better off carrying a bottle of high-pressure nitrogen instead of all that stuff.

[rtxoff]

Also accelerating something in that way produces torque which you will have to counter....

[Tex_NL]

The torque issue can be solved by adding a second wheel. Just spin it in the other direction.

[sgt_flyer]

Well, that's just a centrifugal pump that's one of the most used pumps in rocket engines. And they need a gas generator + turbine to be driven for a reason. We don't have limitless and lightweight energy source avaible to drive the pump. (And if we had this energy, i'm sure we could use it for engines even more efficient - vasmir like engines &co. )

And there's limits to those pumps - in the form of vortices and cavitation, which can be extremely destructive. (Basically, cavitation is a 'void' created behind the blade of the pump - when this void forms, the liquid will come back fast and slam the blade - and the impact force can weaken and shatter a lot of materials. (A easy 'cavitation' example, is seen with shattering the bottom of half filled bottles by hitting it on the top.)

[KASASpace]

The only problem with this that I see, is that you would need some seriously strong materials for the Centrifuge. It has to have an Angular Velocity at the outer edge, of approximately 4.55 km/s to match up with RL-10s. But, that means you would need either a really big centrifuge, or a really strong.

Perhaps both.

And if done, I recommend Carbon-Nanotubes.

- - - Updated - - -

The torque issue can be solved by adding a second wheel. Just spin it in the other direction.

Adding mass.

[Ravenchant]

Another option would be to drop the rotating parts entirely and use a cyclotron/synchrotron instead. Accelerating charged particles instead of a centrifuge would give you insanely high ISPs (effectively limited by size), but at the cost of huge power requirements and a TWR approaching 0.

[DJEN]

I don't think this will be efficient at all.

[Tommygun]

Centrifugal machine gun?:

http://en.wikipedia.org/wiki/Centrifugal_gun

[KvickFlygarn87]

And without further to do

Enough to make me LOL. It's "without further ado", what you said was totally weird and the opposite feeling that the image gives us.

[MC.STEEL]

Ok now i know what tangential speed is and i can indeed say that it will have an ISP of 17.

Then what is moving at centripedal velocity?

[Tex_NL]

I've spotted another minor yet design breaking flaw in your idea.

The entire contraption is spinning rather fast and the exhaust is stationary. How do you eject the liquid? How do you prevent leakage between the outside of the spinner and the exhaust?

[Seret]

Congrats, you just invented a common type of pump.

[Rickenbacker]

Isn't this exactly how water scooters work? They pump water out the back to propel themselves forwards.

[KASASpace]

I've spotted another minor yet design breaking flaw in your idea.

The entire contraption is spinning rather fast and the exhaust is stationary. How do you eject the liquid? How do you prevent leakage between the outside of the spinner and the exhaust?

Actually, only the centrifuge should be spinning, the engine "bell" should be stationary.