Better still, a Tramway to Space

[maglifter]

Forget space elevators and pipelines to space, the tramway is far more realistic.

A big 1500 mile tube suspended with superconducting cables, floating in the air, reaching 70000ft, containing a maglev track.

http://www.startram.com/main.html

"StarTram - Ultra Low-Cost To Orbit

The current cost of launching payloads to LEO orbit is very high, on the order of $10,000 per kilogram. The launch costs to GTO and GEO are considerably greater. Major research efforts are underway on advanced reusable launch vehicles that could potentially reduce launch costs to LEO to ~$1000 per kilogram. However, the technology for these reusable vehicles is very demanding and it is not clear whether this goal can be achieved.

The cost of the energy required to accelerate a kilogram of payload to orbital speeds, i.e., 8 km/sec., is actually very small, on the order of 50 cents. If there were no atmosphere on Earth, payloads could be accelerated to orbital speed on Earth’s surface, using a superconducting Maglev suspension to levitate and propel the payload. The resultant total cost (energy plus facilities) to launch payloads would be extremely small, on the order of a few dollars per kilogram.

The heating and air drag forces that would occur in the presence of Earth’s atmosphere prevent such a launch system from being practical. However, if the spacecraft were accelerated in a low pressure tunnel and then launched into Earth’s atmosphere at high altitude where the atmospheric density is very low, then it would be possible to launch payloads at a very low cost.

Plus Ultra has investigated a radically new concept for magnetically levitating and accelerating spacecraft to orbital speeds and launching them at high altitudes. The Plus Ultra concept, termed StarTram, accelerates the spacecraft to 8 kilometers per second in a long (~1000 km) low pressure tunnel on the surface. After the levitated spacecraft has reached orbital speed, it transitions into an upwardly curved low pressure launch tube, along which it travels to an altitude of ~70,000 feet. The cylindrical launch tube is magnetically suspended by the magnetic repulsion forces between a set of superconducting cables attached to it, and a second set of superconducting cables, located on the surface beneath the launch tube. The two sets of superconducting cables carry oppositely directed, zero loss supercurrents.

The launch tube is stabilized vertically and laterally by a set of high tensile strength, lightweight tethers that anchor the tube to the ground, and prevent sway or movement from wind forces (Sidebar 1). The spacecraft exits through a fast opening shutter at the upper end of the launch tube into the low-density atmosphere at 70,000 feet and rapidly ascends to orbit. At the launch altitude, the atmospheric heating rate and drag forces are low enough (Sidebar 2) that the spacecraft can safely ascend into Earth orbit.

StarTram has the potential to increase the present launch volume of a few hundred tons per year to orbit to many thousands of tons per year, at a unit cost that is well below $100 per kilogram."

 

[errorist]

Why not build it up the side a very tall mountain? It should get you out of the very heavy air near sea level?

 

[hitssquad]

Mount Everest is only 29,035 ft. You might start there, but you would still have another 40,000 feet to go.

 

[maglifter]

I've always wondered why it wouldn't be possible to use a hypersonic scramjet with maglev launch assist.

You build a long maglev tube, make a vacuum of it, and then launch the scramjet. At the end of the tunnel, when the jet has reached mach 5 or 6, you open a diaphragma, and POP, the scramject sucks in air and propels itself to mach 10.

 

[Astronuc]

A maglaunch tube inside a mountain still has the column of air above the launch point.

Mount Everest is a bit impractical - one would has to bore into the mountain - and that requires getting heavy equipment (e.g. tunnel boring machine) to the site. Mountain climbers to Everest have to hike up glaciers to get to the highest base camps which are still quite aways from the summit.

Itinerary - http://www.alpineascents.com/everest-dtd.asp
Climb overview - http://www.alpineascents.com/everest.asp
Everest Maps - http://www.alpineascents.com/everest-map.asp


Besides 70000ft is no where close to space. On October 4, 2004, SpaceShipOne rocketed to an altitude in excess of 328,000 ft.

Maybe the OP meant 700,000 ft. But then one might as well go with a space elevator.

 

[cronxeh]

or.. or.. why not scotch tape a scramjet to a hot air balloon and then release it from 65000 feet?

 

[NateTG]

or.. or.. why not scotch tape a scramjet to a hot air balloon and then release it from 65000 feet?

I think that was the canuckistani X-prize project approach. Of course you'd have to get a working scramjet first.

Regarding reusable vehicles:
Everything that gets launched into space that has to come down again is really a wasted effort, doubly so for things like the space shuttle that go into orbit because they also need fuel to slow themselves out of orbit to come back down.

 

[maglifter]

I think that was the canuckistani X-prize project approach.

I didn't know Israel was called Canuckistan.

But anyway, the maglauncher is not as crazy as you think, since it will be a practical means to get rid of the first stage of ordinary rockets. ESA and NASA are working on it. Their maglauncher will be 2.4 miles long, just to get rid of the first stage. The Startram, on the contrary, is pure fiction.




And Cronxeh, you were kindly asked to stick to making your LPG powered airplane, remember?

 

[Astronuc]

I haven't dismissed the mag-launch concept - but putting in Everest would be very difficult, if not impossible.

Ideally - put it in a mountain as close to the equator - Andes perhaps - as possible.

In the US, the mountains are pretty much limited to 14,000 range - from sea-level.

But still there is the air column in the launch tube.

The question is - how much acceleration in 14,000 ft (or there abouts).

On the other hand, non-living cargo (supplies) can be shot at > 10 g.

People cargo need lower g's, so may be an improved shuttle design is useful.

 

[NateTG]

Any surface-launched object will initially be in an orbit that collides with the Earth unless it is traveling at escape velocity. That means that any gun-launched satelite will have to have additional significant rocket boosters.

Regarding G-forces and materials: In the 70's Gerrard Bull was using artillery to shoot weather probes to high altitude, and did some research into gun-to-space type technology, and apparently had little trouble hardening all of his equipment to handle 40G by encasing delicate components in resin.

The pie-in-the-sky gun launch scenario would involve a very large light gas gun and 4000G's. At those forces, special electronics would be necessary.

It's pretty easy to caculate the approximate acceleration that you'd need to get for a particular distance. If the length of the barrel is $d$ and the muzzle velocity is $v$ then the acceleration is going to be:
$$a=\frac{v^2}{2d}$$
So, let's say you want to have a maximum acceleration of 10G's ($\approx 100 \frac{m}{s^2}$) and a muzzle velocity of 5000 m/s. Then you're looking at a length of about 120,000 meters.
If you can handle 1000G's (which is reasonable for raw materials) you can get the same muzzle velocity in 1,200 meters.

I remember going through and calculating things like power consumption for a device like this, and deciding that it would probably be worth building it near a good power source rather than trying to find a high altitude location since cable losses are significant.

 

[hitssquad]

Chemical spin-traps to protect astronauts from high-g effects

non-living cargo (supplies) can be shot at > 10 g.

People cargo need lower g's

Not necessarily. If the problem is nerve death, spin-traps (such as the chemicals PBN and N-t-butylhydroxylamine that life-extensionists use today to preserve the youthfulness of their brains and other organs) and other mitochondrial protectors might allow rocket-passeners to survive unharmed without blood in their brains for a few minutes. Also, astronaut brains might be supercooled - again, to protect against high-g-induced brain death - on the launchpad with cold breathable-liquids such as perflourocarbons.

 

[maglifter]

Lots of confusing messages

I think some concepts are being confused here:

1. a maglauncher is a simple maglev track, a few miles long (2 - 3 miles) from which a spaceplane is launched, horizontally. We're talking 1 g here. Nothing big. Nasa is building it. (see this interesting presentation: http://science.ksc.nasa.gov/shuttle/nexgen/Nexgen_Downloads/Spaceport_Visioning_Final_Report.pdf )
Such a maglauncher is merely used to give the spaceplane a headstart, in order to reduce the hassle of the first stage of an ordinary rocket launch.

2. a stratram is a very long (near) vacuum tube, with a maglev track, on which the carrier gradually moves to extremely high speeds, before it pierces a diaphragm and enters the atmosphere at high altitude.

3. Bull's mega guns are: nonsense.


Ok.
-A maglauncher is feasible, cheap, and it's being built.
-Startram is fiction, fun and will never be built, just like the space elevator.
-Mega guns are not fun, not useful and have been built by hundreds of amateurs. One of which was assassinated in Iraq.

 

[russ_watters]

Mount Everest is only 29,035 ft. You might start there, but you would still have another 40,000 feet to go.

Aerodynamic resistance is a surprisingly small piece of the energy required to get into orbit - and at 70,000 feet, you're above >95% of the atmosphere.

Still, getting a ramp up to 70,000ft requires construction materials unlike anything even unlikely to be available in the forseeable future. A launch ramp up the rockies, however, puts you above half the atmosphere.

 

[maglifter]

Russ, you seem to know quite a bit about this. I don't.

Could you help me with this? Suppose you want to launch 3 people from a maglev track up to 100km altitude (merely a parabola with a top of 100km) (the X-prize criteria).

-how long should such a track be?
-would it make any considerable difference if you were to build it on a mountain slope with the track end at 5km altitude?
-and what would be the advantage of building it on a mountain right on the equator ? (I've never quite understood why equatorial launches are best).

Thx!

 

[Astronuc]

Equatorial lauches take maximum advantage of the rotational speed of the Earth's surface. And one would want to lauch eastward, as the shuttle and other manned craft do.

One can do a simple trajectory calculation and figure with or without air resistance, what the initial velocity would need to be from some height H (~ 2-3 km) to 100,000 km, and then what the acceleration over H would have to be to get that velocity.

Or suppose, one starts off on a level track, the acclerates through a curve to the final 2-3 km lauch tube. Then one has to calculate that tolerable accelerations in the three sections.

Re:

spin-traps (such as the chemicals PBN and N-t-butylhydroxylamine that life-extensionists use today to preserve the youthfulness of their brains and other organs) and other mitochondrial protectors might allow rocket-passeners to survive unharmed without blood in their brains for a few minutes. Also, astronaut brains might be supercooled - again, to protect against high-g-induced brain death - on the launchpad with cold breathable-liquids such as perflourocarbons.

No thanks.

 

[cronxeh]

its doable. not maglev. $4-6 million. got cash?

 

[Kenneth Mann]

I haven't dismissed the mag-launch concept - but putting in Everest would be very difficult, if not impossible.

Difficult yes, impossible no. Actually, the whole idea of space access is difficult, and we're just looking for the best trade-offs. Mountain launch seems quite promising in this light. We just need to study it more carefully to determine if it is a winner. Also, why does it have to be Everest? There are many mountains over 25,000 feet high, (over a hundred, if my recollection is correct) most of them in the general area of the Himalayas, the Hindu Kush, etc.

Ideally - put it in a mountain as close to the equator - Andes perhaps - as possible.

Actually, the Equator is ideal only for Equatorial applications, such as Earth Synchronous insertions. Everest and those mountains around it are at about 28 degrees North, the same as Canaveral, and wouldn't you know, the inclination to the Moon is 28 degrees. (Ideally accessible from either North or South). To the Ecliptic, it's about 23 degrees. I'd be careful selecting Andean mountains. Some of them are in the mid-twenties range, but if I recall correctly some may be volcanic.

But still there is the air column in the launch tube.

Nothing's perfect, but then do we really need a purely ballistic insertion? We really want to find an approach that is more economical over the very long term. For this, we need simply to appreciably increase our effective specific impulse, and if we cheat a bit by off-loading part of the job from Today's purely rocket-based approach, then we are ahead in the game. The drawback is, this will only work if we commit to a large-scale move into the space environment, thus amortizing the very large up-front costs of a mountain-based launcher. What might be investigated is, using something like a Scramjet, multiple-use booster with small rockets for the very upper ranges.

 

[Kenneth Mann]

Aerodynamic resistance is a surprisingly small piece of the energy required to get into orbit - and at 70,000 feet, you're above >95% of the atmosphere.

Still, getting a ramp up to 70,000ft requires construction materials unlike anything even unlikely to be available in the forseeable future. A launch ramp up the rockies, however, puts you above half the atmosphere.

I agree with this. Why even consider 70,000 feet. All we really need is enough boost to get us to a point and velocity at which we can light off something like a Scramjet, and which will put the vehicle into a mode from which it can safely glide down in case of some sort of systems failure at launch. Mach 1, 2 or the like may be quite enough.

KM

 

[Kenneth Mann]

PostScript

If we are really interested in using the Maglev launcher concept where it is of best advantage, we could consider setting up one on the Moon (after we have bases there). There we can simply run the track along the surface (covered or underground, if we don't want to continually have to clean off dust encrustation) wherever we can find a long enough stretch of relatively flat surface. (Actually, we'd probably have to do a lot of landscaping just to get a flat enough stretch of surface.)

Then we could use it to sling out "stuff" to the planets, etc. (We'd have to wait for a monthly window for each launch track. The Moon is only five degrees off the Ecliptic, so we might be able to fudge this a bit.)

KM