# The Zero Delta V Challenge

## Recommended Posts

You're thinking in of real world terms, KSP is different.

##### Share on other sites

My entry, a perhaps not too convincing a demonstration. But you can try this yourself.

I hyperedited myself into a perfectly circular 75656 meter orbit, which does not change height regardless of how many revolutions it go through. By transferring fuel from the lower to the higher tank, my center of mass shifted higher and my orbit height is now 75711.

Javascript is disabled. View full album
Edited by goduranus
##### Share on other sites

@ gorudanus

a) It was not me that banned stuff that didn't conform with classical physics. It was the OP.

What I said applies to KSP, because KSP tries it's best to follow classical physics and in orbital mechanics it does a quite good job. In both KSP and RL, if your final velocity has changed direction or module, Delta V has changed because Delta V means literally change of velocity. And in orbital mechanics ( both in KSP and in RL ) you only have a certain velocity ( direction and module ) in a certain place in a very well defined and unique orbit that is given by the Kepler laws . So if your orbit changes and you are in the same place, your velocity has to be different ( either direction or module ) ...

On the post you made after ( ninja'ed :/ ) :

Nobody said that what you did was not possible in KSP. What it was said was that it didn't conform with classical mechanics and that implied a Delta v different of zero, due to a change of orbit. Because of those two reasons, your solution does not conform with the OP "challenge"

Edited by r_rolo1
##### Share on other sites

if your orbit changes and you are in the same place, your velocity has to be different ( either direction or module ) ...

What if your place changed, but the direction and magnitude of your velocity stay the same. What's happened to your orbit?

Edited by goduranus
##### Share on other sites

Then you are in a different orbit .. unless your are under acceleration from a different source than the gravity well, thus you are not in a orbit at all, but on a trajectory Also, you might not be under any force ( including a gravitational one ), but then you are also not in a orbit.

Edited by r_rolo1
##### Share on other sites

I think everyone's way over-analyzing this. The OP probably originally intended to demonstrate changing an orbit without anything that KER or Mechjeb would call Delta-V. Possibly using decouplers or catapults or the fuel tank COM trick. Yes, it is impossible to change your orbit without using any Delta-V in the literal sense.

If you're under the influence of gravity then maintaining both your speed and direction uses up Delta-V to cancel out the force of gravity.

##### Share on other sites

I think everyone's way over-analyzing this. The OP probably originally intended to demonstrate changing an orbit without anything that KER or Mechjeb would call Delta-V. Possibly using decouplers or catapults or the fuel tank COM trick. Yes, it is impossible to change your orbit without using any Delta-V in the literal sense.

If you're under the influence of gravity then maintaining both your speed and direction uses up Delta-V to cancel out the force of gravity.

Basically, don't use any fuel

##### Share on other sites

Actually, thinking more seriously, why part welder is excluded from the mod list? I've never used one so i'm not sure about implications, but it sounds strange enough to be a hint for the OP's puzzle. Is it just to stop us from easily copy parts? And so the idea would be to exaggerate some small effect with big part numbers, like using 1000 small decouplers etc...

edit: also since Op didn't specify what kind of "ship" to use... what about shooting a kerbal with a part explosion

Edited by Nao
##### Share on other sites

Part welder is obviously excluded because welded parts allow you to create much longer ships.

##### Share on other sites

The Deceptively Simple Challenge: Using NO delta V whatsoever, achieve (or prove) an escape orbit from LKO.

(Before you come back with "It can't be done!", yes it can. You see the effect every single time you launch).

This might be the most important hint. Any ideas what he's referring to?

Also, the restriction against "things that break classical physics" doesn't leave many options. Either the mechanism has to break classical physics OR it has to impart delta-v somehow. The only third option is to us n-body gravitation (with its Lagrange points, etc), but that's not part of stock Kerbal physics, and even there it's not clear to me that an n-body zero delta-v solution would work from low Kerbal orbit (although it arguably could from high orbit).

So back to zero delta-v while not breaking classical physics. If we use a stack separator between two equal-mass halves, the net delta-v will be zero because the resulting delta-v vectors imparted into each half will cancel each other out. So the total delta-v of the system remains zero. Not sure if that falls within the "NO delta V whatsoever" requirement, but arguably it does. And it wouldn't violate classical physics at all. So then you just need a very big cascading series of separations. Not clear to me if it would be feasible to build a sufficiently big series of separators to boost you from LKO to escape velocity, however.

##### Share on other sites

It may refer to the method of using fuel transfer to shift centre of mass. The camera defaults to pointing at the ship's CoM, on many rockets you can see it shift as you burn off fuel. However, it's a KSP bug not grounded in real physics - but there's always a chance ihtoit didn't realise that.

The loltall launch clamp method I gave is also based on something you notice in every launch - Kerbin's rotation.

##### Share on other sites

Please follow the challenge guidelines and supply us with information about your attempt, OP. Or at the very least clarify what is meant by "zero delta V."

## Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

×   Pasted as rich text.   Paste as plain text instead

Only 75 emoji are allowed.