Space

Slingatron to hurl payloads into orbit

Slingatron to hurl payloads in...
Artist's concept for a slingatron space launcher to hurl payloads into space
Artist's concept for a slingatron space launcher to hurl payloads into space
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The five-meter slingatron
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The five-meter slingatron
Slingatron Mark II
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Slingatron Mark II
An artist's concept for a full scale Slingatron space launcher about 200-300 meters in diameter
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An artist's concept for a full scale Slingatron space launcher about 200-300 meters in diameter
Model slingatron used to demonstrate the principle
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Model slingatron used to demonstrate the principle
Different stage of slingatron development
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Different stage of slingatron development
Slingatron Mark I
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Slingatron Mark I
Cutaway view of the five-meter slingatron
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Cutaway view of the five-meter slingatron
Inside the Mark II slingatron
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Inside the Mark II slingatron
Artist's concept for a slingatron space launcher to hurl payloads into space
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Artist's concept for a slingatron space launcher to hurl payloads into space
Comparison of a sling and slingatron
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Comparison of a sling and slingatron
The principle is the same as that of sloshing wine in a glass
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The principle is the same as that of sloshing wine in a glass
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People have been shooting things into space since the 1940s, but in every case this has involved using rockets. This works, but it’s incredibly expensive with the cheapest launch costs hovering around US$2,000 per pound. This is in part because almost every bit of the rocket is either destroyed or rendered unusable once it has put the payload into orbit. Reusable launch vehicles like the SpaceX Grasshopper offer one way to bring costs down, but another approach is to dump the rockets altogether and hurl payloads into orbit. That's what HyperV Technologies Corp. of Chantilly, Virginia is hoping to achieve with a “mechanical hypervelocity mass accelerator” called the slingatron.

Invented by Derek Tidman in the 1990s, the slingatron replaces rockets with a more sophisticated version of the sling famed in the story of David and Goliath, and still used today by enthusiasts to hurl pumpkins across fields.

Comparison of a sling and slingatron
Comparison of a sling and slingatron

A sling works by spinning in a circle about the user’s head. The thong on the sling keeps the stone in place and the slinger spins it faster and faster before releasing it. The limiting factors are the speed of the slinger’s arm and the strength of the thong. The slingatron uses a slightly different principle. If it tried to spin the entire machine fast enough to hurl a projectile into orbit, the forces generated would tear the slingatron to bits. Instead, as its name implies, it acts more like a cyclotron, which is a very simple particle accelerator.

A cyclotron is a flat, hollow metal cylinder inside of which is a vacuum. There are also a pair of magnetic or electrostatic plates of opposing charges. An atomic particle, such as a proton, is introduced into the center of the cyclotron and is attracted to the negative plate. The polarity of the plates flips and the proton rushes toward the other plate. As the frequency of the flipping is increased, the proton moved faster and faster in a series of ever widening spirals until it reaches the rim of the cyclotron and shoots out a window at extremely high velocity, though the machine itself never moves.

The principle is the same as that of sloshing wine in a glass
The principle is the same as that of sloshing wine in a glass

The slingatron achieves the same result mechanically. Instead of using charged plates or spinning around, a spiral tube gyrates in circles around its axis. It is similar to the way someone swirls wine in a glass, so that the wine spins around the glass although the glass itself doesn't spin at all. If the glass is swirled at a low frequency, the wine swirls in a leisurely fashion, but by increasing the frequency slightly, the wine is soon shifting up the sides of the glass and slopping over the brim.

Inside the slingatron is a spiral tube, or a series of connected spiral tubes, depending on the design, that gyrates on a series of flywheels spread along its length. As the slingatron gyrates, a projectile is introduced into the tube and the centripetal force pulls the projectile down it. As the projectile slides through larger and larger turns of the spiral, the centripetal forces increase as the the frequency of gyrations increases to up to 60 cycles per second. By the time the projectile shoots out the muzzle in the rim of the slingatron, it is traveling at kilometers per second.

Friction is an obvious problem with such a setup, but this is reduced at first by a Teflon skin, which rapidly wears away, and then by means of a substance, such as a polycarbonate, with a low boiling temperature, wrapped around the projectile. As the projectile spins around inside the tube, the substance vaporizes and forms a frictionless layer of gas. In addition, unlike conventional payloads, the projectile needs a heat shield for leaving the atmosphere.

Inside the Mark II slingatron
Inside the Mark II slingatron

The goal is to build a slingatron big enough to fire a projectile at 7 km/s (15,600 mph, 25,000 km/h), which is enough to put it into orbit. Actually, it will have to be traveling faster than that when it leaves the muzzle because it has to travel through the atmosphere, where it will lose some velocity. There’s also a need for a small rocket on board for final orbit insertion and course corrections, which highlights the strengths and weaknesses of the idea.

With rapid turnarounds and thousands of launches per year while all of the launch system remains on Earth, the developers say the slingatron promises lower costs for getting payloads into orbit. Unfortunately, the G-forces involved are tremendous with the projectile subjected to up to 60,000 times the force of gravity.

It’s questionable whether any rocket system could survive such stresses and there’s certainly no chance of a slingatron being used on a manned mission because it would turn an astronaut into astronaut pudding. Only the most solid state and hardened of satellites built along the lines of an electronic artillery shell fuse would have a chance of survival. The developers say that a larger slingatron would reduce the forces, but even with a reduction by a factor of 10,000, it would still be restricted to very robust cargoes. This makes it mainly attractive for raw materials, such as radiation shielding, fuel, water, and other raw materials.

The five-meter slingatron
The five-meter slingatron

Currently, there have been three one-meter (3.2 ft) prototypes built ranging from a tabletop demonstrator to a semi-modular design capable of firing a 0.5 lb (226 g) projectile at 100 m/sec (328 ft/sec). HyperV Technologies Corp. has launched a Kickstarter campaign that aims to raise $250,000 to build the modular Slingatron 5, which will be 5 m (16.4 ft) in diameter. It is designed to launch a 0.25 lb (113 g) projectile at 1 km/s (0.62 mi/sec) and later be capable of launching a one-pound (453 g) payload at 2 km/s (1.24 mi/s). Eventually, the team hopes this will lead to a full-scale version capable of launching a payload into orbit.

In addition to the Slingatron 5 demonstrator, the developers also hope to host the Slingatron Applications Workshop to discuss further applications of the technology and related topics.

The video below outlines how the slingatron works.

Source: Kickstarter

View gallery - 11 images
43 comments
Charles Hoss
we need a good , long tube on the side of a big mountain , and accelerate the projectile in vacuum - this would mean far lower Gs , longer acceleration , bigger projectile , cheaper reach to orbit . let me see , starting from 0 height , up to 10kms , we may choose a 45 degree angle . the resulting distance would be a bit over 14kms . adding an angle at the bottom , curving the trajectory will give us a cannon with a 20-30km long tube . this way the accereation could stay even stay within the human limits . besides that the shuttle used most of it's fuel in the first few kms , to go through this atmosphere , accelerating etc . getting it to 10kms, at say 5km/s as a start would make it far more efficient .
Jules Tipler
Love ideas like this, it's all about thinking laterally. I look forward to hearing more on this subject over the coming years.
flink
@Károly: Robert Heinlein's been there, done that: Starman Jones, 1953.
The slingatron's an evolutionary deadend for initial launch propulsion system from a gravity well that has an atmosphere.
It might be useful out of atmosphere for shooting small cargoes between planetary orbits, though.
Nathan Jeffree
Well if the scientists can work out how to overcome gravity then this technology could become more practicle. That said, i can really see this technology being used as a weapon instead. Think about it ...
Jeff Rosati
How quickly will this be weaponized ...
Joshua Smallwood
Impractical for launching scientific / mechanical payloads into orbit, but I do very much like the idea of sending up raw material, resources and system components (while a rover might not survive a launch, it's individual wheels, arms, etc (disassembled) should be more than capable, being little more than solid bits of metal).
John Zulauf
Or this, "Ram Accelerator" which I worked on for my Master's -- with nearly 3km/s achieved in a laboratory basement sized device in the '80s.
http://www.tbfg.org/papers/Ram%20Accelerator%20Technical%20Risks%20ISDC07.pdf
Neil Cox
I hate that my instinct is to weaponize this concept, but it has good potential with military applications. The Mark II launches 1/2 pound at 100m/s which puts it in light cannon territory, but without the need for a traditional propellant it could be considerably more quiet. If you could continuously feed payloads into the machine without spinning it down essentially have an electric automatic cannon.
Nathan Holmes
I'm not quite sure how you could launch something into Earth orbit with a device like this. Even if you discount air resistance, any projectile would either follow an elliptical path and land somewhere else on the planet, or reach escape velocity and end up orbiting some other body.
Bob Ehresman
A hypervelocity gun. Somehow I imagine this will become a missile defense weapon long before it is a launcher.