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Diametric Drives...limits and how they work


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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 by Spacescifi
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  On 5/6/2021 at 11:00 PM, insert_name said:

trollscience.jpg

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Well it works with docking ports in KSP. 
KAeLJE4h.png
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 by magnemoe
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  On 5/6/2021 at 10:56 PM, Spacescifi said:

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

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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.

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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 by Starman4308
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  On 5/7/2021 at 4:53 AM, Starman4308 said:

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

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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,

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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.

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  On 5/6/2021 at 10:56 PM, Spacescifi said:

Diametric drives are theoretical

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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 by cubinator
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  On 5/6/2021 at 10:56 PM, Spacescifi said:

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

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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 by YNM
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  On 5/6/2021 at 10:56 PM, 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.

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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.

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