Startram - maglev train to low earth orbit

[bananas]

"it should be possible using only existing technology ... Sandia National Laboratories has carried out a '"murder-squad" investigation of the Startram concept, whose purpose is to find any flaw in a proposed project. They gave Startram a clean bill of health."

http://www.gizmag.com/startram-maglev-to-leo/21700/

Startram - maglev train to low earth orbit

By Brian Dodson
01:58 March 9, 2012


The Startram orbital launch system would transport passengers and cargo into space in a magnetic levitation (maglev) train
Image Gallery (7 images)

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If the entire Startram tube is at sea level, on exiting the tube the spacecraft will suddenly be subjected to several hundred g's due to atmospheric drag - rather like hitting a brick wall. To reduce this effect to a tolerable acceleration, the end of the Startram vacuum tube must be elevated to an altitude of about 20 km (12 miles). At this height, the initial deceleration from atmospheric drag will be less than 3 g's, and will rapidly decrease as the spacecraft reaches higher altitudes.

This new requirement begs the question - how do we hold up the exit end of the Startram vacuum tube? Well, the tube already contains superconducting cable and rings. Powell and Maise realized that the tube could be magnetically levitated to this altitude. If we arrange that there is a superconducting cable on the ground carrying 200 million amperes, and a superconducting cable in the launch tube carrying 20 million amperes, at an altitude of 20 km there will be a levitating force of about 4 tons per meter of cable length - more than enough to levitate the launch tube.

<snip>

Sandia National Laboratories has carried out a '"murder-squad" investigation of the Startram concept, whose purpose is to find any flaw in a proposed project. They gave Startram a clean bill of health. Estimates suggest that building a passenger-capable Startram would require 20 years and a construction budget (ignoring inflation and overoptimism) of about $60 billion.

Why take on such an enormous project? Simple - $50 per kilogram amortized launch costs. The total worldwide cost of developing and using rocket-based space travel is more than $500 billion. The Space Shuttle program cost about $170 billion. The International Space Station has cost about $150 billion to date. As yet, we are making very little commercial use of near-Earth space beyond deployment of communication and imaging satellites. Reducing the LEO insertion costs a hundredfold should finally start our commercial exploitation of the special resources of space. Not to mention making orbital hotels a travel goal for middle-class tourists!

[johnd83]

1. This is an interesting idea, but...

I am an engineer who has studied both spaceflight dynamics and electro-magnetics at the graduate level and in my opinion this idea is largely impractical for two reasons: it will require insane amounts of energy to operate and will be extremely unstable. The forces involved in moving a mass at orbital speeds will make sending a rocket down a tube basically impossible without it impacting the walls or creating high G-forces on the rocket. The amount of energy required to suspend the track in the air is also incredible and is way beyond our ability to generate practically. However, this idea would actually work pretty well on the moon where there is no atmosphere. An interesting approach is to launch only people into earth orbit and build spacecraft on the moon where it is easy to launch into orbit. It will still be expensive (although less-so with simpler rockets like SpaceX) to put people into Earth orbit but it would be cheap to launch equipment off the moon.

Edit: few more thoughts...

1. Once you are in orbit you can use something like VASIMR that is nuclear powered and mass efficient but doesn't have the thrust to get into orbit.
2. Rockets are expensive because each one is effectively a prototype. If economy of scale ever gets going and some reasonable reusabillity is implemented the price should come down.
3. Fuel is only 2% of a launch cost.
4. The shuttle program was a technological disaster that made getting into space way more expensive than it should have been.

[bananas]

2. On the moon, the tube wouldn't have to be suspended, it could just lay flat on the surface

and it wouldn't have to be a tube, just rails.
The reason for a tube is so they can evacuate it to reduce drag,
and the reason for elevating the tube is also to reduce drag when the craft exits the tube.
On the moon, there's no atmosphere, so it could be simplified a lot.

[johnd83]

3. Right, that is why it makes sense on the moon.

The velocity needed is also a lot lower. Once you get off the surface you can cruise around on nuclear propulsion. It would also be nice to launch nuclear material on the moon instead of in our atmosphere because rockets tend to explode.

[tridim]

4. As crazy as this sounds, it still doesn't sound as crazy as a space elevator.

Of course building such a thing would be a major problem. There are no 12 mile high cranes.

[quakerboy]

5. What am I missing here

So they want to use an electromagnet to float something 20 KM.

What happens to anything even mildly magnetic in between, or slightly off to the side? If the magnetic field is 20km+ up, wouldn't it have similar range to the sides and down? What happens when a guy with a belt buckle or a diet high in Iron walks under the ramp, over the ground level cable? Sure seems like the answer would be that without a tether, he too would go flying into space.

Or when there is a power glitch and the whole thing drops 20k. I could be wrong, but I get the feeling their "murder squad" investigation was not overly thorough, maybe only looking at "could it get something to space?", as opposed to "is this a good idea, and what could go wrong?".

Another question that came to mind, if you are able to magnetically push something 20 KM up, over the course of 1000 miles, and hold it there, Why not just magnetically lift the thing you want in one much smaller spot, but higher? Start on top a mountain (We are going big here, so I'm gonna say Everest, 9 KM up to start with). Build a mag system to lift it another 30 km. That's almost 40 km of the 200 or so for Low earth orbit. I bet that would drop the fuel cost to get the rest of the way quite significantly. Of course, what would we have to do to power that system. or the one they have designed?

Also, given that the mall of America expansion is set for 2 billion, and Apple has stashed something like 100 billion, I think their 60 billion is very over optimistic.

[bananas]

7. Good questions - I wonder if the report from Sandia National Labs is available. nt

[Angleae]

6. They plan on cooling 20km of superconducting cable how?

Also how do they plan on generating 200 million amps?

[tridim]

8. Doc Brown's plutonium?

[ElboRuum]

12. They intend on generating 1 million amps...

...200 times.

I should think that obvious.

[Fumesucker]

13. Research continues apace on warm superconductors..

And a superconducting cable of whatever length is for most practical purposes a dead short, the "zero" resistance of superconductivity is awfully close to actual zero. It won't take much voltage at all to push extremely high amperages through a superconducting cable because of the vanishingly small resistance of the cable so the wattages might not be as high as you might be led to think by the high current.

If it only takes a microvolt to push the 200 million amps then the total wattage will be only 200 watts.

If you have a transformer with a one million turn primary and a single turn secondary when you put 200 amps into the primary the secondary will see 200 million amps at least in theory.

That's pretty much how a soldering gun works, multi turn primary single turn secondary that gets hot fast at the thin part.

[caraher]

14. With superconductors the voltage drop is essentially zero

The real problem is that there's a critical magnetic field above which superconductors stop being superconductors, and since big currents entail big magnetic fields (indeed, the whole point of this setup is to generate a huge magnetic field that repels the Startram) you can run into trouble pushing that much current through a superconducting cable.

So yeah, it may not be possible to drive 200 MA through a superconducting cable, but the real limit may not be power anyway but quenching (sudden local heating resulting from a transition out of the superconducting phase).

[Fumesucker]

15. I was answering a couple of questions about cooling the superconductor and generating 200 MA

Didn't get into other aspects of the design problems.

Personally I suspect the launch loop or Lofstrom loop is a more doable device but I'm strictly a layman on this stuff so my opinion is worth very little.

http://en.wikipedia.org/wiki/Launch_loop

[phantom power]

9. "If we arrange that there is a superconducting cable on the ground carrying 200 million amperes"

that is a big-ass arrangement.

[Motown_Johnny]

10. a small version for payloads might be practical

basically a large rail gun

but I am not sure that this will be viable for humans (or anything living) within my lifetime

It seems to me that a space elevator would make more sense and be a similarly difficult project. Building something 12 miles high that can deal with those speeds can't be much easier than the elevator that is designed for much much lower speeds.

[ElboRuum]

11. "This new requirement begs the question..."

...er, no it doesn't.



Some time ago someone pointed out to me the actual meaning of begging the question and how it is so rampantly misused as in the above article. I am as guilty as any other in this regard. I know better now.

But because of this fine and noble soul, as dedicated to language as anyone I've ever met, I can no longer see such a thing WITHOUT MY BRAIN SCREAMING OUT IN SHARP EMBITTERED AGONY.

I think I hate that guy now.

[Dead_Parrot]

18. Don't worry about it...

...you'll end up correcting people who use "who" when they meant "whom".

Madness awaits.

[caraher]

16. Simple question regarding this concept:

In the 2nd gen version of this they use a maglev concept to keep the thing in the air. They base this on maintaining a current of many MA along the tube and on the ground. OK.

Where does the current come from/where does it go? On the Startram web page they have a textbook illustration of two parallel wires carrying currents in opposite directions, but those will always be part of some complete circuit. So how do you complete the circuit without messing everything up?

With the ground component of the system one could presumably route your cable such that the return path is very far from the launch tube (we're thinking big already, so what's a hundred km or so of extra superconducting cable?). But the part that's in the air needs to return current at the airborne end of the tube, and you can't just shunt it back down through the tube because that current would experience a downward force through its interaction with the same field you're using to keep the whole thing airborne. I suppose you might run it down the long tether(s) at the ends, but then you're adding some pretty big forces to those as well.

[caraher]

17. OK, I found what I think is the answer...

I found their patent and there they show a very different-looking system that has the advantage that I can at least see how it might actually work! In the patent, you basically have two loops, one on the ground and one in the sky, with a substantial horizontal separation between the parallel legs. This clearly allows for a return current and, if the spacing is substantial, a net repulsive force.