Railgun or Coilgun Launched Booster Rockets?

[Spacescifi]

This actually is for scifi.

 

I curious which is a better option. Railguns or coils?

Railguns: Smaller, but rails wear out and must be replaced.

 

Colls: Need a long length to get a lot of acceleration, otherwise okay.

 

Both require plenty of power....which won't be a problem since scifi is involved.

 

Objective: Launch booster rockets to rendezvous in mid-air to a waiting spaceship that has exhausted it's propellant boosters and is hanging in midair waiting for a refill.

 

Why?

Spoiler

Scifi spaceships generate spherical resisto-gravity fields that work this way:

If you cut engines on ascent with the resisto-gravity field up, eventually you will slow your ascent to  a stop in midair but WILL NOT fall back down unless you turn off the field. 

That is how the boosters can reach it for rendezvous, by reaching the field and joining up to give it a final boost into space.

In space scifi vessels use scifi vacuum reaction engines (don't ask how), so rockets are only for atmosphetic boost to space. They drop the unneeded boosters back to Earth, which usually land spaceX style.

The whole reason I want to launch boosters magnetically is to save propellant for boosting the spaceship they  adjoin to into space past the Karman line.

I do not worry about orbital velocity, because once in space vessels would rely on scifi vacuum reaction drives for orbit and any other space speed adjustments.

 

Other questions: Launching any projectile magnetically transfers heat to the projectile in the process no?

 

Not to mention atmospheric heating from air friction. Might need to solve it by having sweating hulls for the missiles that sweat out a coolant of sorts.

So likely be launched with a booming sound and a thin vapor trail from the sweating coolant, followed by rocket igniton of boosters to reach the waiting vessel hanging in midair.

 

So what do you know on these options regarding which is preferable and boosters being designed to survive magnetic launch and reach the vessel in midair?

 

EDIT: Actually this is easier than the IRL plan a former president received but never went ahead and built, but it could have worked.

https://www.popsci.com/technology/article/2010-11/nasa-engineers-propose-combining-rail-gun-and-scramjet-fire-spacecraft-orbit/

 

This project would require higher speeds though.

 

 

Edited May 20, 2021 by Spacescifi

[JoeSchmuckatelli]

There was a thread a while back about some people trying to use, effectively, a rotor to throw stuff at space.

I remember a bunch of critiques about it, things like atmospheric density and actual weight to orbit making it a pipe dream.

Probably a similar situation

[Spacescifi]

17 minutes ago, JoeSchmuckatelli said:

There was a thread a while back about some people trying to use, effectively, a rotor to throw stuff at space.

I remember a bunch of critiques about it, things like atmospheric density and actual weight to orbit making it a pipe dream.

Probably a similar situation

 

Normally it would be a pipe dream...hence the scifi resisto-gravity field.

Still less cheaty than falling straight up or neutralizing gravity altogether.....keeps rocketry relavent since I wish it to be.

Allows you to refuel in midair without using propellant or moving.

Consider the vessel to weigh oh I dunno...the same as a fully loaded seaship navy destroyer...so about 9,500 long tons (9,700 tons).

 

The actual scramjet rail launch proposed during Obama I agree would be hard but not impossible.

Edited May 20, 2021 by Spacescifi

[SOXBLOX]

Boost a gas station to altitude (with rockets), have ships tank up while the station hovers magically, and land the station (with rockets) to refuel it.

[magnemoe]

I say an railgun sounds more like very high acceleration over an short distance.  More like an traditional gun and you can fire an missile out of an gun. 
An coil gun has lower acceleration, linear engines are already pretty common.  Less g forces but you need an longer track. 
So I say it depend on your setting,  one problem with the coil gun is that the launch orientation is fixed to the track direction.
However an rail gun in an rotating turret is size limited, battleship turrets are massive and  has 16" guns. 

[kerbiloid]

A 100 km high tower with railgun on top.

[KSK]

4 hours ago, kerbiloid said:

A 100 km high tower with railgun on top.

Or you could wrap the coil gun around the tower.

’yo dawg, I heard you like coil guns, so here’s a coiled coil gun.’

[KSK]

Back on topic, I’d go with a coil gun.  Replacing rails sounds like a pain if this thing is being used a lot and lower accelerations allows for  more flexibility with  booster designs and/or whatever cargo pod is being strapped to the top of them doesn’t need to be made rugged enough to withstand railgun accelerations.

 

[wumpus]

Even Spinlaunch  is only trying to get a "first stage replacement": release at about mach 6 and only require vastly smaller engines and fuel.

But the drag losses on that are still huge.  But you might have a realistic railgun (no longer than 10-20km at least) if you don't try to get to orbital velocity on the surface of Earth.

A much more plausible (but requires a lot of tech to be developed in parallel) would be to use a railgun to accelerate your spaceplane to supersonic speeds.  Then use a scramjet to get to ~3km/s (maybe 4km/s by the time the tech is ready).  Use traditional hydrolox for the rest.  Staging is optional, and more likely if you limit your scramjets to ~2km/s  (within current tech proof of concept: see the x-43).

Most of the problems  are discussed here: 

 

Edited May 21, 2021 by wumpus

[K^2]

18 hours ago, JoeSchmuckatelli said:

There was a thread a while back about some people trying to use, effectively, a rotor to throw stuff at space.

I remember a bunch of critiques about it, things like atmospheric density and actual weight to orbit making it a pipe dream.

Probably a similar situation

Sort of, but linac is a lot cleaner. Rotation gives you an illusion that you can accelerate gently over time. But reality is that you are still moving in exact opposite direction from one side of the loop to the other. Which means you have to have accelerated in between. A circular rail just trades linear acceleration for centripetal, and you still have to deal with extreme G forces.

With a linear accelerator, what you see is what you get. If you can build a rail 1km long, then you have 1km to get to whatever target speed you have in mind. Unfortunately, 1km is really, really not a lot for speeds we want to build up.

In terms of practicality, not to rehash all the conversations again, unless you can get your cargo up to something like 10km/s  at a significant angle up, a sea level rail-assisted launch just isn't helpful. If you want to get any sort of benefit from rail launch, the exit point has to be in rather thin atmosphere. As supporting something like this with a static structure is pretty much impossible, we kind of end up all the way back at launch loop concept. Which, you know, is a thing, but not exactly on currently achievable scale.