In the near future, revolutionary space hardware could put an exciting spin on spaceflight.
NASA is putting money into Momentum-eXchange/Electrodynamic Reboost tether technology -- MXER for short -- an innovative concept that if implemented would station miles and miles of cart-wheeling cable in orbit around the Earth. Then, rotating like a giant sling, the cable would swoop down and pick up spacecraft in low orbits, then hurl them to higher orbits or even lob them onward to other planets.
MXER is part space technology, part celestial square dancing - the ultimate dos-à-dos swing machine. The hope is to harness momentum while dramatically lowering the cost of launching space missions.
Working on the railroad
Last month, NASA picked over a dozen industry, government and academic groups to tackle novel propulsion ideas that could transform exploration and scientific study of the solar system.
Under the auspices of the In-Space Propulsion (ISP) Program, NASA is footing the bill on five research areas: aerocapture; advanced chemical propulsion; solar electric propulsion; solar sail technologies; and space-based tether propulsion. The program is managed in the Office of Space Sciences at NASA Headquarters.
"The MXER Tether System will serve as a fully-reusable transportation hub in orbit. It's like a 'space railroad'," said Robert Hoyt, President and Chief Scientist for Tethers Unlimited, Inc./ScienceOps. TUI was awarded funds to look into a MXER tether system based on deployment of a 62-mile (100-kilometer) long cable in orbit around the Earth.
A tether pick-up service for Earth-launched payloads offers cost-cutting pluses.
By eliminating the need to launch an upper-stage rocket along with each satellite, Hoyt said that the MXER Tether System means satellites can be boosted into space atop smaller, less expensive rockets. Propulsion costs for space missions would drop by a factor of ten or more, he said.
Failsafe survival
TUI is based in Lynnwood, Washington and is actively working on tether concepts for NASA, the U.S. Department of Defense, and commercial customers. TUI's ScienceOps Division provides scientific computing services, including development, validation, and optimization of scientific software and algorithms.
Hoyt said that over the next two years the group's strong focus is on developing a high-strength tether suitable for MXER applications. In addition, special TetherSim computer code will be upgraded to enable in-depth simulation of the rendezvous and capture problems of handling payloads with a MXER tether.
TUI is collaborating with the Air Force Research Laboratory's Materials Laboratory to further earlier progress on a patented "Hoytether". That work centers on creating a failsafe, multi-line tether structure. All the better to survive many years of exposure to the space environment and any nasty run in with debris.
"It's sort-of like a one-hundred kilometer long fish-net stocking in space, only it's incredibly strong, and it can withstand many years of bombardment by orbital debris," Hoyt said.
Hard work ahead
Along with Tethers Unlimited, NASA has also awarded MXER tether technology contracts to the Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, as well as Lockheed Martin in Denver, Colorado and Tennessee Technological University (TTU) in Cookeville, Tennessee.
Work on MXER is rapidly moving ahead. For example, TTU faculty and students are readying a tether momentum exchange experiment - but it won't leave Earth. A scaled model is being devised to exhibit how to capture and release a payload with a rotating tether in a microgravity environment.
The tether research will occur inside a KC-135 aircraft under the guidance of NASA through the Reduced Gravity Student Flight Opportunities Program.
How soon MXER could be up and running in space is another matter.
"Realistically, I believe it will take about 7-10 years of hard work to get a MXER flight demonstration into orbit," Hoyt told SPACE.com. Under the new In-Space Propulsion contracts, research teams will be busy over the next couple of years using simulations and ground tests to show that the technical challenges of MXER tethers can be solved, he said.
"If those efforts are successful, I expect that it would take about 5 years to get a flight program off the ground," Hoyt senses.
Next page: High risk, high payoff
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