Rail gun engine the future of space travel?

[Lordmaddog]

It runs on nothing but electricity and recycled metal projectiles and unlike almost all engines  I have ever seen it's placed on the front of the craft.

This is how it works.

A metal sphere starts in the loading chamber (blue) and is injected onto the rail (brown) by the electromagnets. Using megawatts of energy, the sphere is sped up to almost mock ten and at the same time melted into a liquid. The now liquid projectile shoots into the reaction chamber and slams into the plunger (red) imparting its kinetic energy and momentum generating thousands of newtons of forward thrust. The liquid projectile shatters into thousands of tiny droplets that bounce around the reaction chamber until they find their way into the reforming chamber ( silver) were thanks to zero G, heat and the laws of attraction they rejoin with themselves  and other projectiles to forum a perfect sphere roughly the same size as when they were first shot. The newly formed sphere then floats around the reforming chamber until it has cooled enough to once again become magnetic.  At this point it is pull down into the loading line by electromagnets and using a electromagnetic systme similar to a gauss rifle it is shuttled back into the loading chamber where it can be shot once again.

NOW before any one starts shouting BS, brakes blah blah laws of physics I am fully aware that the recoil of the projectile speeding up should cancel out the thrust gained by said projectile slamming into the plunger but just like the EM drive for some reason it works.

You can test this your self by taking two paper clips stretching them out and gluing them to a piece of paper beside each other then glue some type of light weight back stop at the end. Now take either a capacitor or a high voltage battery and attach the positive to one of the paper clips and negative to the other. Then just take a third paper clip and push it onto your rails it will shoot down them and slam into your back stop causing you paper to slid across the counter top. The more powerful the voltage the farther the paper will travel. 

 

[DoctorDavinci]

Ummm, you're forgetting the battery otherwise it is a one shot deal ... That would get heavy fast as you increase the size of this contraption

Plus the mass of the ship could be an issue when compared to the mass of the projectile required to make this idea work ... you gonna need some reinforcing of the structure of said ship in order for it to survive the impact and that will add more mass which will require a larger projectile mass 

Then there is survivability of the crew to consider ... don't want them breaking their necks due to a whiplash effect

Sounds like an interesting science project but not sure it would be scalable 

[Vanamonde]

Moved to Science & Spaceflight, since it's not about KSP. 

[YNM]

 

 

8 hours ago, Lordmaddog said:

recycled metal projectiles

What, from the pulverized remains in the air ?

8 hours ago, Lordmaddog said:

unlike almost all engines  I have ever seen it's placed on the front of the craft.

Goddard put "our standard™ engine" on the front.

Engine is that tiny nozzle high up, fuel down low.

 

Also, you're proposing catching your own spewed bullet. That's about as useful as rocking to and fro on a tied chair and expecting the tie to vaporize. Try catching a real bullet I say without making a hole of any sort in the catcher.

Edited March 7, 2018 by YNM

[Lordmaddog]

1 hour ago, DoctorDavinci said:

Ummm, you're forgetting the battery otherwise it is a one shot deal ... That would get heavy fast as you increase the size of this contraption

 

You would probably power it with a nuclear.

1 hour ago, DoctorDavinci said:

Plus the mass of the ship could be an issue when compared to the mass of the projectile required to make this idea work ... you gonna need some reinforcing of the structure of said ship in order for it to survive the impact and that will add more mass which will require a larger projectile mass 

Then there is survivability of the crew to consider ... don't want them breaking their necks due to a whiplash effect

Sounds like an interesting science project but not sure it would be scalable 

Yes for any thing bigger then a probe the engine would have to be rather large and projectiles weighing in at hundreds of pounds meaning it would take any were from 50 MW to 600MW to power. Though it be more efficient then the EM drive and it wouldn't take years to do a burn.

1 hour ago, DoctorDavinci said:

Then there is survivability of the crew to consider ... don't want them breaking their necks due to a whiplash effect

 

 While there would defiantly have to be test I don't believe the G force would be much more then what an astronaut is subjected to during launch. However the jerking nature of it would defiantly be annoying.

I also believe it be possible to make an atmospheric model of this engine that recast the projectiles on the fly using mechanical methods and a coolant like liquid nitrogen. That or just launching the projectiles at a much slower speed and a faster pace so they don't deform and need recasting.  

Edited March 7, 2018 by Lordmaddog

[KerikBalm]

This will not work, your experiments with paper, and static friction present are meaningless.

[Canopus]

Yeah this won‘t work.

[MatterBeam]

Excuse me.
Your 'propellant' is recovered for re-use?
In other words... there is no nozzle and you are trying to design a reactionless engine?

[Streetwind]

3 hours ago, Lordmaddog said:

You can test this your self by taking two paper clips stretching them out and gluing them to a piece of paper beside each other then glue some type of light weight back stop at the end. Now take either a capacitor or a high voltage battery and attach the positive to one of the paper clips and negative to the other. Then just take a third paper clip and push it onto your rails it will shoot down them and slam into your back stop causing you paper to slid across the counter top. The more powerful the voltage the farther the paper will travel. 

Fun fact: this actually works... on Earth.

The reason this works is because the acceleration along the rail is gradual, whereas the impact at the backstop is an instant transfer of kinetic energy. As a result, the friction between the device and the countertop will nullify a portion (if not all) of the expected backwards motion of the device during the rail acceleration phase. The device should be sliding backwards about half its length and then come to a full stop. But what happens instead is that the device slides backwards less or not at all, because there is friction working against this movement. Then, as the projectile hits the backstop, the device receives roughly the same amount of forward momentum in an instant that it experienced as gradual backwards momentum before. Friction still exists, but since the momentum transfer is instantaneous, it is much more easily overcome. The end result is a net positive forwards momentum which makes the device slide a small distance across the countertop.

If the connection to the battery is solid (i.e. the wires are welded or twisted on instead of merely touching the rails), then the material resistance to deformation of the wires works the same as friction - it more easily resists the gradual acceleration than the instant impact event, and there is potential for a spring effect adding a little bit of extra forward momentum.

In space, in the absence of friction, this would not work. You'd just get a device that is shifted forward by half the length of the rail every time it fires, without actually gaining speed in the process.

 

Edited March 7, 2018 by Streetwind

[p1t1o]

 

3 hours ago, Lordmaddog said:

...blah blah laws of physics...

Come on man...

**thumbs down**

 

 

[Starman4308]

First error: the watt is a unit of power, not energy. Power is a rate of energy over time; a flow of one watt is one joule per second.

Second: Mach 10 sounds impressive until you compare it to rocket propellants. Assuming a standard value of Mach 1 = 343 m/sec, Mach 10 is 3430 m/sec, which is in the realm of a high-performance kerolox/methalox engine, but still much slower than hydrolox engines. You're basically requiring huge power and cooling sources for something you could do with a good old-fashioned rocket... once you delete the catcher that would give you a thrust of zero.

Third: As has been mentioned, violations of laws of physics, amateur experiments on Earth do not necessarily correspond to space, etc.

Fourth: I've seen no reliable evidence to suggest the EM drive works, and given its violation of the laws of physics, I'm very much inclined to believe it doesn't work.

Edited March 7, 2018 by Starman4308

[p1t1o]

5 minutes ago, Starman4308 said:

Fourth: I've seen no reliable evidence to suggest the EM drive works, and given its violation of the laws of physics, I'm very much inclined to believe it doesn't work.

News has definitely been quiet on that front for a while...

[DAL59]

This wouldn't work.  Newton's laws.  Depending on your KSP version, it could work though

 

[Scotius]

The only way you can make this contraption work, is to install a nozzle and let the projectile work as a traditional reaction mass. Even then it won't be really effective. As you described it? No.

[Spaceception]

Read the title, the first thing that came to mind - they did that in The Expanse book. I think it was the fourth

[p1t1o]

Bear with me here...

***

There is a version of this design that would work, and a version of it is explored quite elaborately in the Book "Seveneves" by Neal Stephenson.

What you do is physically seperate the "gun" from the "return system", put the return system on the craft and leave the gun at the launch point.

Then up the fire rate by several orders of magnitude.

Power supply and propellant stay at the point of launch.

Stream of projectiles hits ship, impact provides thrust.

Ship returns steady stream of projectiles, recoil provides further thrust.

Pretty good aim is necessary.

In ground-to-orbit applications this is sometimes called a "space fountain".

In Seveneves this is further advanced by using a continuous chain of links rather than discrete projectiles.

***

So in essence, it DOES work, but the spacecraft remains stationary. You use the force of the projectiles to stretch the spacecraft to encompass the entire distance from origin to destination

It helps if most of the spaceship is empty space.

 

Edited March 7, 2018 by p1t1o

[Green Baron]

11 hours ago, Lordmaddog said:

A metal sphere starts in the loading chamber (blue) and is injected onto the rail (brown) by the electromagnets. Using megawatts of energy, the sphere is sped up to almost mock ten and at the same time melted into a liquid.

It uses megawatts of power, not energy. And how is it melted ? More megawatts for heating ? Because the acceleration might deform the sphere, but not melt it. Btw. the acceleration generates a whole lot of backward thrust on the system.

11 hours ago, Lordmaddog said:

The now liquid projectile shoots into the reaction chamber and slams into the plunger (red) imparting its kinetic energy and momentum generating thousands of newtons of forward thrust.

Yes, exactly (if you see it as a closed system and neglect any losses) the same "thrust" (better: impulse) it gained before thorugh acceleration. Not more, not less. So in the end it ends up where it began.

11 hours ago, Lordmaddog said:

The liquid projectile shatters into thousands of tiny droplets that bounce around the reaction chamber until they find their way into the reforming chamber ( silver) were thanks to zero G, heat and the laws of attraction they rejoin with themselves  and other projectiles to forum a perfect sphere roughly the same size as when they were first shot.

??? No, if you have zero g than the drops just stay where they are. They find no way nowhere ... And why would heat and which law of attraction (?) let the particles rejoin ? Btw., where do the drops come from if you don't heat the thing ? If at all you might have a deformed projectile and/or impact area and that's it. I feel this part needs some more explanation ?

11 hours ago, Lordmaddog said:

The newly formed sphere then floats around the reforming chamber until it has cooled enough to once again become magnetic.  At this point it is pull down into the loading line by electromagnets and using a electromagnetic systme similar to a gauss rifle it is shuttled back into the loading chamber where it can be shot once again.

This needs an experimental part for verification ;-)

11 hours ago, Lordmaddog said:

 but just like the EM drive for some reason it works.

The EM drive does not work. There is no reproducible proof, every measurement could be explained by uncertainties in the setup or measurement errors.

11 hours ago, Lordmaddog said:

You can test this your self by taking two paper clips stretching them out and gluing them to a piece of paper beside each other then glue some type of light weight back stop at the end. Now take either a capacitor or a high voltage battery and attach the positive to one of the paper clips and negative to the other. Then just take a third paper clip and push it onto your rails it will shoot down them and slam into your back stop causing you paper to slid across the counter top. The more powerful the voltage the farther the paper will travel.

That's a different thing, as the electromagnet that shoots the needle imparts a reciprocal force on the table it stands on.

[mikegarrison]

10 hours ago, Vanamonde said:

Moved to Science & Spaceflight, since it's not about KSP. 

It may not be about KSP, but that doesn't mean it's about science either.

Do we have a forum for reactionless drives and perpetual motion machines?

[sevenperforce]

Fun fact: a long, long time ago, some guy proposed mounting a machine gun with a steel plate above it, and firing continuously so that the impact of the bullets would force the plate upward. The bullets were supposed to fall back down and be re-collected for reloading. He, of course, forgot that the recoil of the machine gun would counteract any thrust gains. But it didn't keep him from selling tickets to fly to the moon.

[mikegarrison]

2 hours ago, p1t1o said:

Bear with me here...

***

There is a version of this design that would work, and a version of it is explored quite elaborately in the Book "Seveneves" by Neal Stephenson.

What you do is physically seperate the "gun" from the "return system", put the return system on the craft and leave the gun at the launch point.

Then up the fire rate by several orders of magnitude.

Power supply and propellant stay at the point of launch.

Stream of projectiles hits ship, impact provides thrust.

Ship returns steady stream of projectiles, recoil provides further thrust.

Pretty good aim is necessary.

In ground-to-orbit applications this is sometimes called a "space fountain".

In Seveneves this is further advanced by using a continuous chain of links rather than discrete projectiles.

***

So in essence, it DOES work, but the spacecraft remains stationary. You use the force of the projectiles to stretch the spacecraft to encompass the entire distance from origin to destination

It helps if most of the spaceship is empty space.

 

Yes, the space fountain. A huge megastructure that will fail catastrophically if it ever loses power. Who wouldn't love that?

[StrandedonEarth]

This would be akin to mounting an electric fan on a sailboat blowing into the sail, and expecting it to move the boat (when there’s no other wind).

Or like this:

 

Edited March 8, 2018 by StrandedonEarth

[Starman4308]

2 hours ago, StrandedonEarth said:

This would be akin to mounting an electric fan on a sailboat blowing into the sail, and expecting it to move the boat (when there’s no other wind).

Technically speaking this works; not nearly as well as pointing it in the other direction. I think part of it is that once the sail stops the air blown by the fan, that air then has to get out the way of more incoming air, and that imparts a small net force.

Still, that doesn't salvage the OP's concept. I get that he tested it, and that's great, but there's a reason that scientists put a lot of time into careful experiment design to exclude alternate possibilities like "maybe it has something to do with surface friction from the table it's set on".

[Bill Phil]

4 hours ago, StrandedonEarth said:

This would be akin to mounting an electric fan on a sailboat blowing into the sail, and expecting it to move the boat (when there’s no other wind).

Difference there is that you can use already present air to move. Not really doable in space.

[Green Baron]

8 hours ago, Starman4308 said:

Technically speaking this works; not nearly as well as pointing it in the other direction. I think part of it is that once the sail stops the air blown by the fan, that air then has to get out the way of more incoming air, and that imparts a small net force.

But there is loss through friction, the force from the propeller would be greater than the pressure on the sail, so maybe it'll move slowly in the direction the propeller pulls it.

Of course, i'll throw the mechanical stuff overboard and go sailing :-)

[sevenperforce]

On 3/7/2018 at 12:38 AM, Lordmaddog said:

It runs on nothing but electricity and recycled metal projectiles and unlike almost all engines  I have ever seen it's placed on the front of the craft.

The great thing about this engine is you can place it anywhere on your craft, pointed in any direction, and you'll still end up producing the same amount of thrust.