Diametric Drives...limits and how they work

[Spacescifi]

Diametric drives are theoretical, but would be really nice to have for space travel.

 

How they work: Vessel separates into halves, and the rear half is attracted to the front half, but the front is repelled and therefore flies forward while the rear keeps up the chase.

Both halves fly in tandem continously. It's like a runaway kinetic reaction of sorts.

My be more aptly named Unending Chase drive.

Limits: You want the rear halve, the one you land on or take off from, to be heavier or at least as heavy as the top halve when separate. As obvious problems happen otherwise (crushing on landing). Also I think if the leading halve is heavier than the halve that is supposed to push the pushing halve may not push as well...reduce overall thrust etc.

Awesome stuff you can do: Since you take your reaction mass with you wherever you go you never have to refuel...unless the diametric is powered by some fuel reaction.

Also you can pitch, yaw, and roll while accelerating, since both halves will continue to fly in the same direction so long as your reaction control thrusters are working OK. Would look weird with two halves chasing each other with a small gap between them, but would still occur.

Correct me if I have anything wrong.

You may add to information on diametric drives and how well they would fly, pros and cons etc.

Edited May 6, 2021 by Spacescifi

[insert_name]

[magnemoe]

55 minutes ago, insert_name said:

Well it works with docking ports in KSP. 

In short you have two docking ports around 4 structural panels apart for max effect, set magnetism on front to 0% back to 200% and you get an constant force, it stacks so using 8 or 64 is that much stronger, you only need one forward port even if combining 64 at rear  

Edited May 6, 2021 by magnemoe

[mikegarrison]

2 hours ago, Spacescifi said:

Correct me if I have anything wrong.

LOL. Only "everything". This is completely impossible.

In theory, if you had access to negative mass then you could do this. But you don't have access to negative mass.

Edited May 7, 2021 by mikegarrison

[Spica]

2 hours ago, Spacescifi said:

the front is repelled and therefore flies forward while the rear keeps up the chase.

Try applying Newton's third law to this problem, you'll find that this is impossible for real matter.

Newton's third law and momentum conservation come hand-in-hand, and there's no way you'll be able to violate either, in any situation.

[SpaceFace545]

Even an EM Drive makes more sense than this.

[Spaceman.Spiff]

Lol this doesn’t work at all. Just because you can do it in KSP doesn’t mean it works IRL. 

[SpaceFace545]

23 minutes ago, Spaceman.Spiff said:

Lol this doesn’t work at all. Just because you can do it in KSP doesn’t mean it works IRL. 

Well I jammed some airbrakes and landing gear together in ksp so that means that we could make airplanes fly by meshing their landing gear and spoilers together.

[Spaceman.Spiff]

3 minutes ago, SpaceFace545 said:

Well I jammed some airbrakes and landing gear together in ksp so that means that we could make airplanes fly by meshing their landing gear and spoilers together.

Genius! 

[kerbiloid]

A Paddle Orion drive.

Spoiler

 

[Starman4308]

To be more clear and helpful:

The problem with this is Newton's Third Law of Motion: all actions are matched by an equal and opposite reaction.

If A pushes on B, then B pushes on A.

If A pulls on B, then B pulls on A.

If the rear half of your spacecraft is attracted to the front half, then the front half is attracted to the rear half. You can't have one side pushing and the other side pulling. Otherwise, you get a universe without conservation of momentum or conservation of energy.

It's why spacecraft usually use rockets*: with nothing substantial in the environment to push off of, the only thing they can push off of is themselves: thus, plumes of rocket exhaust exiting one way, the spacecraft accelerated the other way.

*With the exception of things like solar sails, but those wouldn't work in an idealized vacuum.

Edited May 7, 2021 by Starman4308

[SpaceFace545]

6 minutes ago, kerbiloid said:

A Paddle Orion drive.

  Hide contents

 

You have a big net behind the Orion drive which scoops up the broken nuke and fragments of uranium, you then use a conveyor to send it too a factory which rebuilds the nuke and you just shoot it out again.

[kerbiloid]

6 minutes ago, Starman4308 said:

with nothing substantial in the environment to push off of, the only thing they can push off of is themselves

As the rocket can't push from anything, including the hot gas cloud of the burnt fuel, it's the hot gas cloud expanding in all directions, but hitting the rocket wall at one side and a hole at the opposite side.

So, the gas cloud pushes the rocket away,

Spoiler

And as the conservation laws require zero balance, so from the pov of the gas cloud, the rocket and the hole have same masses, lol.

 

[DDE]

I wonder how many people will be getting this reference.

[magnemoe]

4 hours ago, kerbiloid said:

A Paddle Orion drive.

  Hide contents

 

That would work,  the changeling part here would be to make an reusable nuclear bomb or any sort of bomb  

 

[RCgothic]

This is a variant of the "collect the exhaust" idea that we've been over previously.

An object cannot propel itself by pushing on itself.

[kerbiloid]

4 hours ago, magnemoe said:

That would work,  the changeling part here would be to make an reusable nuclear bomb or any sort of bomb  

 

We can just attach the nuke with a rubber band and not explode it.

And make it out of resin. A resinuke.

[SpaceFace545]

1 hour ago, kerbiloid said:

We can just attach the nuke with a rubber band and not explode it.

And make it out of resin. A resinuke.

Or you can give your craft a giant fan that uses deep space hydrogen as it's propulsive medium.

[JoeSchmuckatelli]

7 minutes ago, SpaceFace545 said:

Or you can give your craft a giant fan that uses deep space hydrogen as it's propulsive medium.

Works best when you use the fan to blow that hydrogen to fill the equally giant sail attached to your ship!

[mikegarrison]

This is actually a really popular idea in science fiction. One of the FTL tropes that gets used a lot is the one where a ship generates a black hole at its nose and then "falls into it". Of course, this is the same thing as the magnet car up above, except that it uses gravity instead of magnetism.

[cubinator]

16 hours ago, Spacescifi said:

Diametric drives are theoretical

They're downright imaginary. Such a thing would be a glitch, a programming error in our universe. If you found a way to make one, you should also file a bug report to God.

 

Otherwise, yes, Mr. Troll Face up there demonstrates the concept nicely.

Edited May 7, 2021 by cubinator

[kerbiloid]

50 minutes ago, SpaceFace545 said:

Or you can give your craft a giant fan that uses deep space hydrogen as it's propulsive medium.

Then it will be Medusa.

Spoiler

 

 

[SpaceFace545]

4 minutes ago, kerbiloid said:

Then it will be Medusa.

more like a slow space airplane but yeah

[YNM]

17 hours ago, Spacescifi said:

rear half is attracted to the front half, but the front is repelled

Plain contradiction already, just from the wording.

There's a reason tractor-trailers work, because the rear follows the front's motion, even if the only machine driving the whole thing is located on the front.

You need something that'd either be completely separated or is already completely separated and you can impart force on it. (there's a reason the road under said tractor-trailer doesn't follow the vehicle at all.)

Edited May 7, 2021 by YNM

[SpaceFace545]

17 hours ago, Spacescifi said:

Vessel separates into halves, and the rear half is attracted to the front half, but the front is repelled and therefore flies forward while the rear keeps up the chase.

Well no. If the attraction and repulsion was balanced then the two halves would just "hover" above each other. If the attraction was greater than the repulsion then the two halves would come back to each other. And if the repulsion was greater than the attraction the two halves would slide apart.