Thanks for the ping.
Artist's concept of ProSEDS (NASA)
It sounds like a space kite! Where have I seen that before? Oh yeah--
Mark W.
Posted on 02/05/2002 5:49:22 AM PST by vannrox
| Source: | NASA/Marshall Space Flight Center (http://www.msfc.nasa.gov/) | ||
|
|
|||
| Date: | Posted 2/5/2002 | ||
Propellant-Free Space Propulsion Technology Marks Critical Milestone At NASA's Marshall Space Flight Center
Propellant-free propulsion technology has taken a critical step toward reality, completing a series of systems tests at NASA's Marshall Space Flight Center in Huntsville, Ala.The Propulsive Small Expendable Deployer system – called ProSEDS – is a tether-based propulsion experiment that draws power from the space environment around Earth, allowing the transfer of energy from the Earth to the spacecraft.
Inexpensive and reusable, ProSEDS technology has the potential to turn orbiting, in-space tethers into "space tugboats" -- replacing heavy, costly, traditional chemical propulsion and enabling a variety of space-based missions, such as the fuel-free raising and lowering of satellite orbits.
The initial flight of ProSEDS, scheduled for early summer, will mark the first time a tether system is used for propulsion. To be launched from Kennedy Space Center, Fla., ProSEDS will fly aboard an Air Force Delta II rocket and demonstrate an electrodynamic tether's ability to generate significant thrust.
"We achieved an important milestone with our tests in November," said ProSEDS project manager Leslie Curtis of the Marshall Center's Space Transportation Directorate. "Using a vacuum chamber to represent the space environment, we successfully simulated the first 16 hours of the experiment's initial flight."
In orbit, ProSEDS will deploy from a Delta-II second stage a 3.1-mile-long (5 kilometers), ultra-thin bare-wire tether connected with a 6.2-mile-long (10 kilometers) non-conducting tether. The interaction of the bare-wire tether with the Earth's ionosphere will produce thrust, thus lowering the altitude of the stage.
Although the mission could last as long as three weeks, the first day is the most critical, because the primary objective of demonstrating thrust with the tether should be achieved during the experiment's first 24 hours.
During the mission profile tests last November, engineers from the Marshall Center, along with their partners in academia and industry, tested the experiment's multiple systems as if the flight were actually taking place.
"We took ProSEDS through every step of the mission's first 16 hours," Curtis said. "We operated its hardware, batteries, cables and software, activated and deactivated systems, and collected and transmitted data as we would during an actual flight."
During the tests, all subsystems functioned as designed, including the hollow cathode plasma contactor, a critical component that enables the tether system to complete its electrical circuit.
During the flight, the process of collecting energy will begin when the electromagnetic portion of the tether collects electrical current along the tether's length as it moves through the Earth's magnetic field. To keep the current flowing, the plasma contactor reconnects the electrons with the invisible, electrically charged plasma that surrounds the Earth, emitting the electrons back into space so it can complete its circuit.
"We were pleased to see the plasma contactor perform well throughout the test, even under conditions outside its expected operating range," said Curtis. "It demonstrated the robustness of its design and the performance range of the ProSEDS operating system." The contactor was designed and built by the Electric Propulsion Laboratory in Monument, Colo.
Additional testing of ProSEDS hardware leading to its launch will include thermal testing, tether deployment and final system verification with flight software.
NASA's industry team for the ProSEDS experiment includes the University of Michigan in Ann Arbor, Alpha Technologies of Huntsville, Ala., Electric Propulsion Laboratory of Monument Colo., the Smithsonian Astrophysical Observatory in Cambridge, Mass., Tether Applications Inc. of Chula Vista, Calif., and Triton Systems Inc. in Chelmsford, Mass.
The ProSEDS experiment is managed by the Space Transportation Directorate at the Marshall Center.
Editor's Note: The original news release can be found at http://www1.msfc.nasa.gov/NEWSROOM/news/releases/2002/02-017.html
If this can do that, let's hope it doesn't become another one.
What they're talking about here is the use of electricity and the Earth's magnetic field.
However, tethers potentially provide another form of "propulsion," in the sense that the top or bottom ends of the tether are going the "wrong speed" for their altitude -- the system moves at the velocity of the center of mass. You can use the position on the tether to raise or lower an orbit.
If you raise something to the top of the tether and let it go, it's going faster than orbital velocity for that altitude. Letting it go raises the orbit. (Which is what happened to the Tethered Satellite piece after the line broke.)
Likewise for downward -- it's going too slow for the altitude, so letting it go lowers the orbit. (Which is what happened to the Shuttle when the line broke.)
This approach probably works best when you have a massive center structure with tethers extending up and/or down, and relatively light deployables.
Same with tethers. They are only "momentum transfer" devices, providing modest increases in velocity which is given to the payload at the tether's expense...ultimately paid by a small dimunition of the Earth's momentum.
Neither technology will work for boosters or deep-space propulsion. In this sense they are just stupid stunts.
--Boris
Thanks for the ping.
Artist's concept of ProSEDS (NASA)
It sounds like a space kite! Where have I seen that before? Oh yeah--
Mark W.
I'm surprized no one has yet pointed out that the tether will make for one heck of a visual spectical. This should be a Do-Not-Miss sight if it's anything close to the way that TSS-1 looked as it went over.
Truly one of the most beautiful sights in the heavenlies to see with the naked eye. I'm not kidding, folks. Don't miss a chance to see this one.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.