SHOOT -- Superfluid Helium On-Orbit Transfer
The Cryogenics & Fluids Branch has developed a practical application the fountain effect, a superfluid helium pump. After testing on the ground, the pump flew in the space shuttle as the Superfluid Helium On Orbit Transfer (SHOOT) project. The thermomechanical pump is basically a fountain effect demostration, except that the helium flow, rather than spouting out through a small hole, goes instead through a tube that leads into another storage dewar. Royal mail letter box near me. SHOOT flew on the space shuttle mission STS-57 in June, 1993.
- Helium is abundant in space, where it's produced as a product of the fusion reaction inside stars such as the sun. The naturally occurring helium on Earth, though, comes from a different sort of process. Deep inside the Earth, radioactive elements such as uranium and thorium decay and turn into other elements.
- Helium-3 occurs as a primordial nuclide, escaping from Earth's crust into its atmosphere and into outer space over millions of years. Helium-3 is also thought to be a natural nucleogenic and cosmogenic nuclide, one produced when lithium is bombarded by natural neutrons, which can be released by spontaneous fission and by nuclear reactions with.
Mining Helium In Space
Zero 2 Infinity wants to launch passengers 40 kilometers into space with helium balloons at a much lower price, at just over $130,000.
The porous plugs used in SHOOT were manufactured by Coors, a company which has been making porous filters for many years. Lately, they have branched out as a manufacturer of dilute ethanol solutions, which they filter by pumping them through their own porous filters.
The thermomechanical pump has advantages over a traditional mechanical pump for pumping superfluid helium in space. A mechanical pump, with moving parts, has a risk of mechanical wear, and thus of breakdown. The risk of breakdown is more of a problem in space, where repairs may be more difficult and costly than on earth.
Helium Hydride Found In Space
A mechanical pump also may mix bubbles of helium vapor in with the liquid. On earth, there is not a risk of mixing helium vapor into the liquid because the pump can be set at the bottom of the helium tank, where it will be completely covered by liquid. In zero gravity, however, there is no up or down. Thus, the liquid helium does not pool at the bottom of the tank, and a mechanical pump would have nowhere to sit where it would see only liquid. A thermomechanical pump, since it can pump only superfluid helium, does not mix bubbles of vapor in with the liquid.
There is another system used to pump fluids in space which would not work with superfluid helium. In this system, the liquid is held inside a flexible membrane inside a tank. Pressurized gas is used to compress the flexible membrane, forcing the liquid out. There are at least two problems with using this for superfluid helium. Since helium has the lowest boiling point of any gas, there would be no gas that could be used for this. Also, it would be difficult (if not impossible) to find a material for the membrane that would remain flexible at liquid helium temperature.
SHOOT used two dewars, connected by a tube. There was a thermomechanical pump at each end of the tube, that is inside each liquid helium dewar. This setup is shown below in schematic form.
DIn the diagram, I've drawn the valves as simple lines pivoted on an axle running through the center of the line. Of course, the real valves were more complicated. Also, I've shown one valve as open and the other as closed, just to illustrate the way I'm indicating closed and open valves in these diagrams.
To pump superfluid helium from the left-hand dewar to the right-hand dewar, the heater of the pump in the left-hand dewar was turned on.
DTo pump superfluid helium from the right-hand dewar to the left-hand dewar, the heater of the pump in the right-hand dewar was turned on.
DWe also have an animated version of the SHOOT schematic diagrams.For more information (including technical references) check our
SHOOT webpage.
The story of liquid helium in space continues in
Nvidia quadro fx 4800 for mac pro. helilum in space, part 2.
Helium Balloon In Space
Helium Balloon In Space Station
- Introduction to Cryogenics
- Crogenics & Fluids Home Page
Helium In Space
|