Maglev Catapult Launch Systems

To achieve an initial acceleration for the early part of your launch velocity profile, it would be easier to push off the solid earth than to accelerate via action-reaction thrust. The coupling would be much better and would improve as your payload gets heavier.

Why then not try a maglev launch catapult with say, an inclination of 30 degrees? This could be particularly good for heavy payloads, like a Moonshot.

So this would be an open-air maglev railtrack, accelerating your heavy launch vehicle from zero to Mach 3. The railtrack would start inland and terminate at the seashore as a pier.

Imagine then your heavy launch vehicle consisting of a scramjet-driven first stage, and a conventional rocket as an upper stage.

So this would be Two-Stage-to-Orbit (TSTO), or technically 3-stages if you count the catapult as a stage.

With this ground catapult taking care of the zero-to-Mach3 acceleration, then your launch vehicle would be capable of accommodating a much larger payload than would otherwise be possible. The routine launch costs would be dramatically lowered after the heavy sunk-in capital costs for the maglev. This would achieve the lowest-cost access to orbit.

What are the pro's and cons of this approach?

cons:
-) your maglev railtrack would have to be quite long if you want to keep g forces low enough for humans to endure.
-) because of that length and your proposed 30° angle you would have to built a HUGE structure to achieve this.
-) how do you stop the maglev train after your "first" stage lifts of, if the track just ends on the peer?
-) noise. going supersonic on the ground won't let you build this near populated areas
-) heat? Not sure about this, but I guess your "train" would probably need some form of at least basic TPS if you want it to go mach3.

This is an excellent idea, which is why people have been considering it for decades. Rockets use a huge amount of their fuel just getting through the first few kms of the atmosphere. The 2 best locations in my opinion are the western slopes of Kilimanjaro and Chimborazo. They are both very close to the equator and both have excellent geography for building a track like this. Both of them will allow you to build a track of about 11-12km with a slope of about 20-30 degrees. If the maglev track has enough power to accelerate the launch vehicle at 3Gs (30m/s^2), a speed of 840m/s could be achieved after 28 seconds, just before it leaves the track. I think it's important not to break the sound barrier on a system like this, at least not until it's been tested with a dummy load. An additional benefit is that the launch vehicle would have an altitude of about 6000m when it leaves the track. Hopefully someone else can do the math to calculate how much fuel/cost this would save per launch. If more velocity is required, the track could be extended by digging a tunnel at the start of the track and moving the initial starting point underground, possibly even below sealevel.

The downside is the financial cost of building something like this. It would be enormous, maybe less than the ISS, but still enormous. It would also require the cooperation of Tanzania or Ecuador. On top of that there is the small issue that both of these mountains are volcanic. They have both been dormant for many hundreds of years, but a significant construction project could disrupt the bedrock enough to cause some fresh activity.

johno

I'm calculating 10 miles of track required to get to Mach3 while enduring 3 G's. There are maglev railway lines that are far longer than this.

Yeah, that 30-deg inclination would be difficult, unless you could curve it up a mountainside, or something. Given that your launch vehicle would be aerodynamic, it could have some lifting control-surfaces that might help it to negotiate the curved track towards the end that tilts it into a more inclined orientation. The magnetic field strength along this curved section would be the strongest, to help negotiate the curve (ramp?)

If your sled shoots off the track along with the launch vehicle, it would then fall off from beneath it, and then it could release some parachutes to allow it to be recovered safely. Just have it fall into some lake, and then have it transported back for re-use.

As for noise, there are plenty of deserted areas where test ranges are built.

Sure, you can have thermal shielding for your sled, and for the launch vehicle. Why is that a con? The scramjet stage would probably need it for re-entry anyway, since it's going to return for re-use.

John Hunter is probably one of the global authorities on this sort of launch system.

http://www.youtube.com/watch?v=1IXYsDdPvbo

Ah yes, that's pretty close to right. I made a mistake in my previous post, thinking that 840m/s was subsonic. I was mixing up km/hr and m/s.

Accelerating at 30m/s^2 (3Gs) requires 34 seconds to get to 1020m/s (Mach 3). The average velocity over this time is 510m/s. So the total distance traveled is 17340m or 17.34km. That's approx 11 miles.

johno

So anyway, the technology that would be developed as part of such a project could eventually make its way back to the civil sector, for better mass transportation systems like maglev trains, etc.

Actually the technology for maglev civil mass transport is already available. What's missing is the political will to build them.
The advancements (regarding speed) of conventional rail systems in the last ~15 years are another major factor contributing to that lack of will to build maglev trains (their speed advantage isn't as big anymore as it used to be).

Just take a look at the German Transrapid: if you have the money you could theoretically order one right now.
http://www.transrapid.de/cgi-tdb/en/basics.prg

Well, maglev transportation is supposed to be very energy-efficient, which is important in these days of peak oil, high energy prices, and climate change.

Airlines are taking the biggest hit in the entire transportation sector, due to the rising cost of fuel. Maglev trains could one day become a viable successor for rapid long-distance mass-transit. The technological spinoffs might also be have good ripple effects across the economy.

trying to keep it in a low enough G profile for human transport may not be worth it. as you mentioned the track would have to be 10+ miles long. the amount of power needed to levitate and then accelerate a payload over those distances without chemical rockets would still be quite high.

the Sled Track at Holloman AFB is (last I heard) working on eventually replacing its current track (10 miles) with a maglev. even without this they've hit mach8+.

anywho, if you focused on this system more as a payload delivery system, where you were not so limited on G accelerations, you could get a payload mass to mach5 in a much shorter distance, and probably (overall) less energy consumption. mach 5, hit the scramjets and go. If you are using a secondary propulsion, like the scram jet, I dont see the point in raising it to 30 degree elevation, let the vehicle do the pitch up maneuver.

now placing the sled track at high elevation.... that i can see as being productive


here's a question i would have though..... what about building another mass accelerator in orbit, for lobbing the cargo from earth orbit out to lunar orbit/lagrange point, etc. again, use it for the initial acceleration and have another engine (VASIMR, for example) take over for the rest of the flight/and for decelleration. makes me wonder how much "recoil" there would be, if any, and if there was, how would you compensate for that.

lol considering it is monday morning, i hope this made at least some sense and was just a smattering or wods on the page

good info mFL

I'd say that you could build your track to accommodate both unmanned cargo payloads and manned payloads. It's just that the manned payloads would be launched at lower G's, while the unmanned payloads could be launched at higher G's depending upon the type of payload. But the same track could be used for all.

Well i think you would get get quite a bit of recoil unless you have figured a way to negate our Mr Newton or has inventor convinced you in another thread but i think you could balance it out by doing alternate direction accelerations at different points in the orbit ie opposite sides of the planet in relation to your objective and a few on board gyroscopes but the disadvantage would be that the payloads would take different amounts of time to arrive i think.

Bah, once you're off the ground, it's not worth it to use any catapults, since your catapult would be forced to have thrusters to deal with the recoil.

I wonder if it would be possible to combine the maglev catapult idea with the high-altitude floating platform idea, to get a catapult that extends all the way to about 40 km up.

You'd have to be able to cope with the fact that there's no stiffness in it though, since it would be jiggling all over the place. I'm not quite sure how you'd design such a thing, or what it might look like.

i shudder at the thought...lol

wouldn't the amount of perceived recoil be variable though? depending on the mass of the orbital accelerator. take for instance, if you fire a 30-06 round from a M1 garand, vs a much lighter rifle, the amount of recoil the shooter perceives would be less than w/ the M1 due to its mass. maybe i'm just thinking of it wrong...

though for any 'recoil' on such a platform... could orbital position be used to compensate? i.e. drop from a higher orbit to a lower orbit, then use a propulsion system to slowly bring it back up to a firing orbit? don't know enough about orbital mechanics myself, so i figured i'd ask

@ sanman
might just be easier to do a space elevator at that point