# Can you "condense" a magnetic field and use a precision magnetic "beam" for space travel?

1. Apr 11, 2015

### caesartherome

Hey all,

So I've been writing a hard science fiction novel and need real answers from someone who understands the fields better than I ( I have no formal education outside basic highschool classes in physics)
The problem I have is I'm not a fan of faster than light travel but I need a way for the explorers to travel great distances quickly.
My idea is this: A precision magnetic field, or simply a "beam" that is pointed at a corresponding station and the resulting magnetic attraction pulls the craft towards it.
I have no idea if that sort of thing is possible.
So I would like to know
1) How fast is magnetic attraction for extremely powerful magnets? And would those speeds offer the explorers the ability to travel great distances in a reasonable time frame?

2) Is a "precision magnetic beam" even theoretically possible?

3) What sort of calculations can I use to make the technology seem realistic?

4) If a system like this existed, would it affect any planetary magnetic fields?

5) A zero g environment means the system would only need to ping it's target station to retain it's speed, which removes the necessity for vast amounts of combustible fuel, but how could they slow down effectively without hitting the planet or the station?

I apologize if I put this in the wrong section, again I'd really like some input on this from people who understand it better than I.

Any help is Aprreciated.

Thanks again.

-Theron.

2. Apr 11, 2015

### TESL@

Last edited: Apr 11, 2015
3. Apr 11, 2015

### PWiz

Usually when authors want to make their characters jump distances (light years, actually), they use wormholes. The problem with regular travel (i.e. actually moving through space from one spot to another, regardless of the method of propulsion) is that the traveler ages considerably less than those at the destination/origin. In extreme cases, the other individuals die of old age by the time the traveler completes the journey (with him/her aging just a few years). Does this matter in your story? What distances are we talking about over here? Do you plan on making your characters travel very close to the speed of light?

4. Apr 11, 2015

### caesartherome

I'd like to keep everybody the same age if possible and try to stick to realistic possibility as much as possible.

I'm leaning towards creating a solar system that's recently been discovered. Some where in the range of 5-15 light years.
The events take place after the moon and mars are colonized so mankind is familiar with the local solar system.

I'd like the explorers to travel as close as possible, at whatever speed magnetic attraction occurs, so I'm limited by that technology, I'll have to warp the story and setting around that.

5. Apr 11, 2015

### PWiz

Magnetic fields extending over 15 light years trying to accelerate a spaceship to near-light speeds does not seem like a very good idea to me. If you want to be realistic, IMO you should just allow mankind to discover how to manufacture very small quantities of exotic matter to make wormholes. You'll then overcome the aging issue (and the need for insanely strong mangetic fields).

6. Apr 11, 2015

### phinds

Changes in magnetic fields propagate at c, but are PHENOMENALLY weak at any kind of distance. Use for space travel is a total non-starter.

7. Apr 11, 2015

Staff Emeritus
Speed of light. No.

No.

That pretty much removes the need to answer the remaining questions.

8. Apr 11, 2015

### DaveC426913

Concur with above. I think magnetism falls off as the cube of the distance, so vanishingly small after a short distance.
Also, it is unilateral in its targets, which means before a spaceship would even feel it, you'd be pulling buildings out of the ground.
And finally, there's no way to direct it. The closest you can is to sort of shield something from it by enclosing a target in a cage of soft iron, which will route the field lines around the target.

9. Apr 12, 2015

### Staff: Mentor

In the manner you describe no. Something along similar lines is beamed propulsion, there are concepts that involve firing charged particle beams at a spacecraft which it uses to accelerate via a magnetic sail:
http://en.m.wikipedia.org/wiki/Magnetic_sail

Note that without some form of FTL your characters will not be getting around the Galaxy in a hurry.

10. Apr 12, 2015

Staff Emeritus
Suppose we had an iron spaceship, and stuck a magnet in front of it attached to a stick...

<evil grin>

11. Apr 13, 2015

### caesartherome

Dang, I figured I could at least get a bit farther than regular rocket fuel.

Oh well, I'll think of something !

12. Apr 13, 2015

### caesartherome

I was hoping it'd be at least possible because "mag-jump" sounds really cool to me!

13. Apr 13, 2015

### Staff: Mentor

What's your setting like? Perhaps we can suggest a suitable fictional form of transport that would be based on realistic science but speculative enough to fit in your story.

14. Apr 13, 2015

### caesartherome

The setting is the first manned mission to study life on an exo planet named Athena which orbits a super giant and has a singular tidal locked moon that has life as well, but only around the areas where it's not to hot or cold. Sol has been respectively colonized with the general mars colonies and moon bases etc and Athena was originally placed about 5 light years from Earth ( it's a completely fabricated solar system of course).

My original plan, if this was possible, was to make a man made metal that allowed pilots to manipulate the magnetic field.
So relatively close as far as light years are concerned but they apparently won't be getting very far at all ;)

I'd like to shy away from hyper drives, light drives or the "graviton" technology. I really don't want it to sound like pseudoscience but I'd also like to stretch the rules as much as possible.

The propulsion system is only there to describe the trip in a realistic way, the main idea of the book is the biology and geology of Athena and Luna B.

I've tried the "photon drive thing" and the only way I figured that could make sense is artificial man made particles that give photons the ability to act like they have mass without actually having them, in other words space magic.

So basically no space magic haha.

15. Apr 13, 2015

### Staff: Mentor

Not sure what you mean by needing photons to act like they have mass. A light sail can impart momentum, though for any reasonable acceleration you're going to need a laser as the light source powered from the solar system. Did you check out the beamed propulsion link I posted above? It wouldn't be too handwavey given the subject matter to propose really mature magnetic sail technology. Essentially the space craft projects a really strong magnetic field around itself, back in the solar system a powerful array of particle beam generators fire charged particles at the craft. As the particles hit the field they impart momentum boosting it up.

You could propose something like that for speeding up to a cruise speed and perhaps multi-stage nuclear/fusion/antimatter propulsion for slowing down. Whilst technically it might require prohibitory amounts of fuel and power this is science fiction. Most readers will give these sorts of things a pass.

16. Apr 13, 2015

### caesartherome

Well I did have a system of gates that stayed in position in open space that acted like "train tracks" that didn't exactly send the magnetic field the entire distance. Instead it'd ping the "radiostation" as I call them and the ships traveled through these and allowed the ship to maintain the magnetic attraction for greater and more precise distances than a realistic magnetic has.

17. Apr 13, 2015

### PWiz

So you had gates at regular intervals covering a distance of 15 light years?? Wait, is this like a well-established 'galactic motorway' of some sort in your story? I mean do people in your story regularly use it for coming and going?

18. Apr 13, 2015

### caesartherome

Yes and no, the original discovery was an accident. They were essentially just probing open space and found the system.
As far as localized travel yes, they use them for trade routes to the colonies and random mega space stations that dot the localized system and open space.
I guess the best way to describe it is like when Americans first branched out to explore the west and had small homesteads and pioneers in the far reaches of the land. They sent the gates pre conctructed into space whenever they had the chance so some gates haven't even been traveled thru or even locked into the system yet.

I've got the destination and the story solid from there, it's just the begining and the realism behind the trip I'm having trouble with.

I'm thinking about scrapping the distance completely and playing off of the "nemesis idea" of a second sun near ours.

19. Apr 13, 2015

### Staff: Mentor

So you're imagining a scenario where strung out between planets are a line of magnetic gates that pull a ship in and throw them out the other side? That's unworkable for a few reasons;

1) There's no way to direct a magnetic field as a beam, a craft would have to come very close to such a gate.

2) Planets in a solar system aren't just sitting at rest to each other, they're all orbiting the sun at different speeds. Even if you managed to get a line of gates strung out perfectly between two planets within a very short amount of time they would be spread out into completely different places.

The closest feasible technology resembling this would be some sort of magnetic mass driver/rocket sled (scroll down on the last link). You could have some sort of megastructure in orbit of each planet that's a form of coil gun; accelerating a craft and shooting it out. The speeds achieved would be impressive but not ground breaking, a 1000km tube accelerating at 20gs would only impart 19kmps by the time the craft exited. Respectable but that's something rockets could achieve.

20. Apr 13, 2015

### DaveC426913

This would work wonderfully as a retro-Vernesque or Wellsian story.

I just finished reading Stephen Baxter's The Time Ships - a sequel to Wells' The Time Machine - it picks up the very moment Wells' epic story leaves off. In it, he explains that the time machine was powered by Plattnerite, a mysterious glowing substance whose properties are never clearly explained. (It's the equivalent of the "magic potions" that so often drive Gilbert and Sullivan* stories. Doesn't matter how it works, only that it does.)

*did I get that right?