Space Fountain

[Jolly Roger]

“Orbital Railroads: Beanstalks and Space Fountains” By Paul Lucas

http://www.strangehorizons.com/2003/20030714/orbital_railroads.shtml

Note: The quote below was edited extensively to fit in this post (and to stress the Space Fountain). Click the above link to read the entire article.

“The space elevator will be built about 50 years after everyone stops laughing.” –Arthur C. Clarke

The main obstacle keeping the human race from colonizing the solar system is the first 160 kilometers. Climbing out of Earth’s gravity well is difficult, dangerous, and extremely expensive. Today, it costs over $10,000 to put just a single pound of payload into orbit, and a single flight of the Space Shuttle costs over a half billion dollars.

Yet this is not a situation unique in the history of exploration. In the early 1800s, overland travel across the American Frontier was equally arduous and wallet-heavy. … Some … thought it might take over 800 years to colonize the American West.

Yet by the end of that century a new technology — the railroad — had accomplished the task in only a few short decades. Our difficulties in achieving orbit might be solved by a similar method — by building a railroad track straight into space.

Originally proposed … in 1960, the concept of Space Elevators [sometimes nicknamed Beanstalks] has been taken up by many science fiction writers over the years, … and countless science article speculations. It is currently under serious preliminary study at NASA…

The basic principle of a Space Elevator is fairly simple … If you anchored an incredibly strong wire to Earth’s surface at the equator … you would end up with a perfectly-straight railroad track right into space….

Once the cable is set up, elevators can ride up and down it via electromagnetic rails, delivering cargo straight into orbit…

The Space Elevator is a simple, straightforward idea with one very serious complication: the structural stresses put on the elevator cable would be truly enormous… one material meeting these requirements has recently been synthesized, albeit only in microscopic quantities…

Once the technology matures, orbital interface travel from surface to space is estimated to be reduced to less than a thousand dollars a ton for cargo, or a rate equivalent to a passenger train for human riders.

Today it costs about $22,000 per kilogram [$10,000 per pound] to put cargo into Low Earth Orbit because of the enormous energies standard rockets must generate in order to reach orbital velocity. Using today’s energy costs, it would take about 75 cents per kilogram [~34 cents per pound, or ~$700 per ton] for a Space Elevator to do the same thing.

A Space Elevator would pay for its initial set-up costs in a few decades. The builders could even make money by selling the delta-V of the Space Elevator to outbound ships, flinging them into space from the far end of the cable…

…. a … Space Elevator could … cost … $10 billion dollars for initial set-up costs.

…. Today, carbon nanotubes cost about $500 per gram of mass, or roughly $500 million dollars per ton. A Space Elevator cable will, of course, weigh many thousands of tons…

[AN ALTERNATIVE]

An alternative method to the Space Elevator for building a railroad into space is the Space Fountain…

A Space Fountain uses a continuous stream of electromagnetically accelerated metal pellets to hold things up at extreme altitudes…

Small metallic pellets by the millions would be shot up to a “deflector” station far overhead, which would use magnetic field scoops to catch the pellets, curve them back down with an electromagnetic accelerator, then shoot them back down to the ground… The pressure exerted on the magnetic fields of the scoop and curved EM accelerator by the continuous stream of pellets would keep the station aloft.

The … Space Fountain … uses a continuous … stream of pellets to constantly exert pressure on the station it is holding up…

…. the pellets and the suspended station never actually make physical contact; the magnetic fields of the scoop and curved accelerator act as a kind of buffer, preventing any physical damage from the pellets screaming at the station at over 4 km/second. Yet the pellets exert pressure on the magnetic fields as they pass through them, and this force is in turn passed on to the physical structure of the station, holding it aloft.

Using this technique, it is thought the fountain could hold up a full-sized, fully-equipped space station … at … heights of 40,000 kilometers plus. However, the higher the station, the higher the required start-up and maintenance energy… For the purposes of building a tower capable of launching vehicles into orbit, 40 to 200 kilometers … may be more than sufficient…

…. once the system is set up, the energy needed to maintain it would be much less than its start-up energy… some energy will eventually be lost over time, but this can easily be continually compensated for … at a small fraction of the energy needed for the system’s initial set-up… even if all power were cut to the pellet stream, it would still function normally for a while, and it might take up to several hours for the suspended station … to feel even a wobble.

Space Fountain structures … will … be built with multiply-redundant support streams … with up to … eight per individual structure, each with its own independent power supply…

To be continued…

[Jolly Roger]

Continued…

…. the Space Fountain … can literally be built from the ground up. The ground station and the deflector station … would both be fully constructed on the ground, and the station placed on top of the ground station with their accelerators aligned. Then [as] the fountain is powered up slowly, the force of the pellet stream eventually lifts the station… The process can be suspended at any altitude … indefinitely, allowing for calibrations, maintenance, new construction, and so on.

If the support streams are sufficiently over-powered … the fountain can also be used to support … elevators or walls along its length… electromagnetic accelerators/decelerators can be built vertically along the stream as the fountain is slowly built up, drawing upon the force of the pellets passing through magnetic fields for support. [As] the wall sections (and any internal structure they themselves may support) are held aloft by the internal stream passing through them, they are under no extraordinary structural stress…

Thus Space Fountains can be used to create truly gigantic structures and towers as well as used merely to hold a space station aloft. And, unlike a Space Elevator, it would not require any extraordinarily expensive materials to hold together; modern-day alloys and composite materials would do just nicely.

The most obvious use for such a super-high structure would of course be as an orbital launch tower; line the outer walls with electromagnetic accelerators and shoot a payload up the side. A fountain tower about 40 kilometers high would be sufficient to launch passenger-carrying vessels to orbit…

A fountain tower could also be used as a super-sized arcology, research facility, industrial center, or more as a fountain 100 kilometers high and 100 meters wide at its base would have about 7.85 … cubic kilometers of volume…

Space Fountains would … have to be demonstrated on a “small” scale, first used in building kilometer-high transceiver towers and such for radio and television broadcasts. The technology can then be scaled up to support super-highrises, and then finally a true Space Fountain…

Though their initial construction costs may seem exorbitant, [Space Fountains] will quickly pay for themselves not just by making orbital travel cheaper and easier but by making space-based economies truly viable for the first time in history. They are just too good an investment for future generations to ignore.

But … within our lifetimes … [because of] long-standing conservatism …. exotic concepts such as the elevator and fountain could prove to be a very hard sell.

However … the advantages may be well worth the investment. After all, just as many who saw the first steam engines never thought they would transform a continent, so too are most people today unaware that the opening of the solar system to mankind is just a single railroad track away.

A “small”, relatively inexpensive, 40 kilometer Space Fountain could be built with existing materials and technology. Its power requirements could be supplied by Focus Fusion reactors. Their helium ion exhaust may even provide the “pellets” required to keep the tower aloft.

One possible site for this Space Fountain would be the Oklahoma Spaceport (formerly the Clinton-Sherman Airpark) near Burns Flat [there’s a mental picture! 😉 ], Oklahoma. It is located central to the contiguous United States and North America, and has much of the infrastructure needed for a space facility.

This could really open up space in a big way.

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

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

[DaveMart]

Very interesting – and am I right in thinking that this could be tested on a small scale by hobbyists?
Presumably though, you would need to reach a fair size before it would serve any useful function as an energy store, which would seem to me to be the easiest early application.
Anyone like to hazard a guess of how big you would have to build to get something useful?
Or could you build very lightweight mobile phone masts using this technology, a few tens of meteres tall?
Regards,
DaveMart

[Alex Pollard]

The Earth is electrically charged with respect to space, for a start there is an electric field of 150V/m (downward) at the Earth’s surface. There are continual electrical exchanges between the upper atmosphere and space – “sprites” and “elves”. I would anticipate unexpected electrical effects when firing a stream of metal projectiles through the atmosphere. Mind you, such effects could perhaps be harnessed to power the process.

[Brian H]

Did I miss it? How does one get access to the suspended station with the Fountain? Ride the stream?

[Jolly Roger]

Brian H wrote: Did I miss it? How does one get access to the suspended station with the Fountain? Ride the stream?

Yes, you did miss it.

If the support streams are sufficiently over-powered … the fountain can also be used to support … ELEVATORS or walls along its length… ”

The most obvious use for such a super-high structure would of course be as an orbital launch tower; line the outer walls with electromagnetic accelerators and shoot a payload up the side.

Either take an internal elevator, or stop the external payload at the top. If you don’t mind the exercise, you could also take the stairs. It’s only 40 KILOMETERS!

Yes, this is all “riding the stream”.

[Brian H]

Jolly Roger wrote:
…

Yes, this is all “riding the stream”.

I wonder also what the pellet speed* is, and what the aerodynamic phenomena around the “stream” would be like. Sounds pretty drastic. Sure mess up any birds (or planes**) flying into it! Also be interesting to see what would happen during a severe thunderstorm, or even a tornado, in the vicinity.

*At escape velocity, wouldn’t the pellets burn up due to friction, both leaving and entering the atmosphere?

**Or satellites. A directed version of this would make a super satellite-smasher. Or ABM or AA defense.

[Jolly Roger]

Brian H wrote:

…

Yes, this is all “riding the stream”.

I wonder also what the pellet speed* is, and what the aerodynamic phenomena around the “stream” would be like. Sounds pretty drastic. Sure mess up any birds (or planes**) flying into it! Also be interesting to see what would happen during a severe thunderstorm, or even a tornado, in the vicinity.

*At escape velocity, wouldn’t the pellets burn up due to friction, both leaving and entering the atmosphere?

**Or satellites. A directed version of this would make a super satellite-smasher. Or ABM or AA defense.

I respectfully suggest that you read the Wikipedia article

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

Its source material may contain more particulars about calculations of the pellet stream mass, velocity, etc. Severe weather scenarios may also have been discussed in the source material. I do not know.

As I understand it, the pellet stream would be encased in a vacuum tube for the lower 100 kilometers or so. Air in the tube would be removed to reduce friction with the pellets.

Birds and planes would have to crash through the tower superstructure and would be pretty messed up before they even hit the pellet stream.

The Space Fountain is based on “rail gun” weapon technology. Research into anti-aircraft, ABM and anti-satellite applications may be applicable to the SF and vice versa.

[Brian H]

Yes, just read it, but still have some problems with the logic. A vacuum cylinder will remain so only if its top is out of the atmosphere, or if it is sealed. In the latter case, the pellets cannot exit. One could build both up & down towers simultaneously, with the top station spanning them and providing the seal, but the “build up from the ground” process seems far more problematic than it is being depicted.

[Charles Wilcox]

Alex Pollard wrote: The Earth is electrically charged with respect to space, for a start there is an electric field of 150V/m (downward) at the Earth’s surface. There are continual electrical exchanges between the upper atmosphere and space – “sprites” and “elves”. I would anticipate unexpected electrical effects when firing a stream of metal projectiles through the atmosphere. Mind you, such effects could perhaps be harnessed to power the process.

Alex, I thought this too, but recently did a search and the proponents of the systems take it (somewhat simplistically) into account: The Space Elevator – Chapter 10: Challenges: Electrocmagnetic Fields. ( Sorry I couldn’t find a more “reputable” website with this info. )

[JoeL]

The main Space Fountain (and related concepts) stumbling block that hasn’t been addressed is that whatever reduction in weight is experienced by the structure will be experienced as a downwards force on whatever turns the pellets around. Unless the pellets will be turned around over a much greater distance than the building is tall, the same limitations on material properties will be encountered. However if the building is to be tall enough to make low orbit cheap and easy, a vertical underground shaft deep enough to effect a manageable rate of change in momentum would proabably penetrate into the earth’s mantle.

[Jolly Roger]

JoeL wrote: The main Space Fountain (and related concepts) stumbling block that hasn’t been addressed is that whatever reduction in weight {that} is experienced by the structure will be experienced as a downwards force on whatever turns the pellets around.

You seem to be assuming that the entire weight of the structure is supported by the top deflector station. That will not be the case. “Lifting Stations” will be positioned at regular intervals up the pellet stream. These will be pellet decelerators, and momentum will be transferred from the pellet stream to the lifting stations. A section of vacuum tube will be suspended from the lifting station above it. Each lifting station will only be responsible for lifting the weight of the section of vacuum tube between itself and the one below it.

Sections of vacuum tube will be loosely connected in some sort of sealed sliding arrangement that allows a little relative movement of lifting stations and tube sections.

Other structures, such as walls, elevators, etc. will be attached to lifting stations.

… a vertical underground shaft deep enough to effect a manageable rate of change in momentum would probably penetrate into the earth’s mantle.

You seem to be assuming that the base decelerator has to be linear. Current designs assume that the pellet path can be bent 90 degrees.

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