Sling stage

[Buzz light fear]

Had an idea to make a ligh stage that instead of thrusting the thing forward it spun it on a long stick an then decoupled and flung the payload faster than the same stage could have done

[Terwin]

All you need to do is sling your sling-stage away from your ship faster than the exhaust velocity of your engine.

As you can include the decoupler and other structural components, you might even manage with marginally less velocity on your sling stage.

Of course there is no guarantee the in-game physics will actually work as expected...

Last time I checked, you can slowly move/raise your altitude with a simple 2 tank design: 

1) transfer all fuel into the tank closer to your destination(tank A),

2) rotate the empty tank(tank B) around the center of gravity(in or near tank A) until an arrow starting at tank A an pointing at tank B is also pointing at your destination

3) return to step 1

note: rotating your ship keep your center of gravity, but pumping fuel moves it, so you slowly crawl towards your destination with no fuel cost, and only the energy cost of rating your craft using reaction wheels.

[MiniMatt]

Sounds like you've independently had the same idea as @Cunjo Carl's Spin to Win Challenge - and it's a freakin' genius idea

[Buzz light fear]

Thanks mini Matt I thought I was and was trying to save on mass and fuel for a mission and use the least delta-v to get going fast

[Buzz light fear]

4 hours ago, Terwin said:

All you need to do is sling your sling-stage away from your ship faster than the exhaust velocity of your engine.

As you can include the decoupler and other structural components, you might even manage with marginally less velocity on your sling stage.

Of course there is no guarantee the in-game physics will actually work as expected...

Last time I checked, you can slowly move/raise your altitude with a simple 2 tank design: 

1) transfer all fuel into the tank closer to your destination(tank A),

2) rotate the empty tank(tank B) around the center of gravity(in or near tank A) until an arrow starting at tank A an pointing at tank B is also pointing at your destination

3) return to step 1

note: rotating your ship keep your center of gravity, but pumping fuel moves it, so you slowly crawl towards your destination with no fuel cost, and only the energy cost of rating your craft using reaction wheels.

Could you make a demo video 

[Terwin]

1 hour ago, Buzz light fear said:

Could you make a demo video 

Probably not, but fortunately, Scott Manley already has:  

 

[Buzz light fear]

Does that mass shifting ting actually work in real life just curious 

[magnemoe]

20 minutes ago, Buzz light fear said:

Does that mass shifting ting actually work in real life just curious 

No it don't, in real world that would change orbit up and down.

However you could put an wire between an space shuttle, extended it and then cut it, this increase satellite speed and Ap, shuttle loose speed and deorbit 

[cfds]

4 hours ago, magnemoe said:

No it don't, in real world that would change orbit up and down.

The better explanation is: The centre of mass of the spaceship stays on its orbit but the single parts of the ship get moved around with respect to this centre of mass.

[Buzz light fear]

5 hours ago, cfds said:

The better explanation is: The centre of mass of the spaceship stays on its orbit but the single parts of the ship get moved around with respect to this centre of mass.

To bad I was hoping for it to work for a propulsion but it is just a unrealistic game exploit 

[MaxwellsDemon]

Isaac Newton* always wins.

 

___________

* as amended by Einstein

[Buzz light fear]

10 minutes ago, MaxwellsDemon said:

Isaac Newton* always wins.

 

___________

* as amended by Einstein

True man 

[Cunjo Carl]

3 hours ago, Buzz light fear said:

To bad I was hoping for it to work for a propulsion but it is just a unrealistic game exploit 

Believe it or not, there is a space drive proposed on this very effect of moving the mass around. Called the woodward drive, it moves the mass by moving an extremely intense electromagnetic field. Because of e=mc^2 that field will exhibit a mass at different places at different times so the ship can inchworm through space, always pushing/pulling off the heavy part. It, uh, probably won't work, but it's a fun thought exercise, and totally analogous to our Kerbal pump ship.

Here's a wiki article! https://en.wikipedia.org/wiki/Woodward_effect

I will posit that Isaac Newton always wins, but mostly because he was head of the Royal Society at the time and got to write the history books (see Leibnitz). If you read the Principia (probably better not to, it's bizarre), Newton actually attributes the three laws to others, which was kindof a surprise to me. These days, in science, I feel like we can safely amend the statement to: "Wikipedia always wins".

Have fun breaking KSP!

Edited August 3, 2016 by Cunjo Carl

[moogoob]

Back to the original topic (since we're starting to talk reactionless drives)... is a simple "sling" propulsion method useful? The only time I've seen such a thing used was in Firefly (or possibly the film), where a spinning sling fired a grenade thing.

[Corona688]

15 hours ago, Buzz light fear said:

Does that mass shifting ting actually work in real life just curious 

It most definitely would not, it violates conservation of momentum.

[MaxwellsDemon]

58 minutes ago, moogoob said:

Back to the original topic (since we're starting to talk reactionless drives)... is a simple "sling" propulsion method useful?

I don't see how this could work.  A sling (at least the way I'm thinking it's meant) is at basis a variety of lever; there's no place to put the fulcrum in space.  (Unless we're talking 'gravity assist' slinging, that is.)

[moogoob]

Projectile------------------------------------------fulcrum (CoM)-----COUNTERWEIGHT

Like that. Light projectile, heavy counterweight. Get the whole thing spinning, then release projectile, sending counterweight and projectile heading in opposite directions; the projectile being much faster due to lower mass.

[Buzz light fear]

42 minutes ago, moogoob said:

Projectile------------------------------------------fulcrum (CoM)-----COUNTERWEIGHT

Like that. Light projectile, heavy counterweight. Get the whole thing spinning, then release projectile, sending counterweight and projectile heading in opposite directions; the projectile being much faster due to lower mass.

Thanks you are thinking what I was thinking

[Cunjo Carl]

You guys are on to a good idea! There's a whole slew of real-life designs proposed for things just like that, working on a variety of different principals. They're generally called tethers, though the name can change depending on the use and mechanism. Here's a wiki article!

https://en.wikipedia.org/wiki/Momentum_exchange_tether  Wiki always wins.

It's also possible to do this in KSP (much to my delight) and we've got a few flinging Kerbals across the cosmos right now. Thanks to @MiniMatt for linking it above.

7 hours ago, MaxwellsDemon said:

I don't see how this could work.  A sling (at least the way I'm thinking it's meant) is at basis a variety of lever; there's no place to put the fulcrum in space.  (Unless we're talking 'gravity assist' slinging, that is.)

It feels like it, right? If there's no solid points in space where could there be to put the fulcrum? It turns out, though that the ship's center of mass behaves as the fulcrum. As the whole ship spins around its center of mass, parts of it can get flung away by centrifugal force, speeding away in a hopefully-useful direction. It's not altogether intuitive, but it winds up that it works! How you get the momentum tether spinning when there's nothing to push off of is one of the chief problems, and everyone's got their own ideas. KSP is nice to provide us with several excellent options to toy with, like the (non-physical) reaction wheels.

5 hours ago, moogoob said:

Projectile------------------------------------------fulcrum (CoM)-----COUNTERWEIGHT

Like that. Light projectile, heavy counterweight. Get the whole thing spinning, then release projectile, sending counterweight and projectile heading in opposite directions; the projectile being much faster due to lower mass.

This setup is my favorite because it's the most energetically favorable. The least energy/angular-momentum put in leads to the most fling coming out. For whatever reason, most proposed designs for momentum tethers seem to be fully symmetrical. Not sure why.... In any case, the counterweight design works, so if you had a mind to, you could go make one in KSP right now!

 

I should add that many momentum tether designs aren't just for flinging things. They're for catching incoming ships, too. That would be a terrifying mode of travel. Cheers!

Edited August 4, 2016 by Cunjo Carl

[MaxwellsDemon]

9 hours ago, moogoob said:

Projectile------------------------------------------fulcrum (CoM)-----COUNTERWEIGHT

Like that. Light projectile, heavy counterweight. Get the whole thing spinning, then release projectile, sending counterweight and projectile heading in opposite directions; the projectile being much faster due to lower mass.

Ah, I see.  You're still going to have to put the energy into the system in order to get it (or at least most of it) back out, of course-- TANSTAAFL.

[moogoob]

7 hours ago, MaxwellsDemon said:

Ah, I see.  You're still going to have to put the energy into the system in order to get it (or at least most of it) back out, of course-- TANSTAAFL.

Yup! You need to spin it up - adding angular momentum. That angular momentum gets turned into the regular kind when the projectile is released.

[MaxwellsDemon]

So is the idea that you can add the momentum slowly, say with a high-isp engine, and then release it all (effectively) at once?   Okay, I'm starting to understand.   Took me a bit to get my head around it...

[steuben]

or a reaction wheel farm, which might be better for reuse. But, yes that is the idea.

[swjr-swis]

Or hamsters kerbals in a giant wheel, running for their lives snacks.

[Buzz light fear]

How about try sending some thing to minmus using a tether it would be more efficient than using the thrusters on the vehicle does it take less energy to spin some thing than to just excelerate it with the normal engines