Posted on 02/05/2002 5:49:22 AM PST by vannrox
| Source: | NASA/Marshall Space Flight Center (http://www.msfc.nasa.gov/) | ||
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| 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
Until you realize that a net thrust of only 0.5 lbs is quite noticeable for a 250,000 lb Shuttle. For a 5,000 lb vehicle, that same tiny mouse-fart would provide 120 km of orbit raising per day in low earth orbit.
By comparison, it would require over 60 lb of hydrazine per day to get the same result.
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.
Which will undoubtedly be fuel for the next generation of enviros: "The United states has just 3% of the world's population, but uses almost 100% of the Earth's momentum....."
Neither technology will work for boosters or deep-space propulsion. In this sense they are just stupid stunts
In the same way that spy, weather, and communication satellites are stupid stunts?
How much delta-V can be provided by such systems?
The key to access to space is in the earth-to-orbit phase.
You have no spy, weather, or comm sats without ETO. $10,000 a pound and you are worrying about mouse farts.
--Boris
Electro-magnetic repulsion. Pump a current through a loop. Result, a magnetic field. Put one magnetic field in proximity with a second (the tethered system and the Earth's magnetic field). Depending on polarity you either get repulsion or attraction. The total thrust is very small, but since there is very little resistance, you still move away from the Earth or towards the Earth with every orbit.
Buck Rogers stuff that is for real. The only thing is ya gotta be patient.
It seems you are missing the big picture - while this system provides only maneuvering-level thrust, it saves the delta cost of lifting maneuvering fuel required for the duration of the mission into orbit - yes at $10k per pound.
it would require over 60 lb of hydrazine per day to get the same result
For a platform that could take advantage of large and frequent orbit changes (read: spysats) you're talking huge bumps in mission savings/capability/life.
Should you doubt it, would you care to place a small wager, say 10% of the projected savings on an selectable-orbit, years-long-duration, zero-service, Keyhole sized satellite? I'd be willing to take the payoff in $10s, $20s, or pennies. I'd even be willing to pay for leasing the truck fleet for delivery of the payout out of the proceeds.
I'm not sure what that mouse has been eating, but it roars.
</As a matter of fact, I am a rocket scientist>
In LEO, the 120 km/day corresponds to a delta-V of about 65 m/sec per day, which is a heck of a lot. And it's not a consumable, meaning that I can replace that 65 lb of propellant/day with 65 lb of payload.
The key to access to space is in the earth-to-orbit phase.
Well, yes. But one measure of satellite capability is the ratio of payload to propellant. If I don't have to carry 500 lb of prop, I can use the volume and mass for carrying payload.
For near-earth satellite application, a tiny amount of thrust is all you need.
The problem with low-orbit satellites is that there is still a tiny bit of atmosphere up there. The drag from that will cause the satellite to eventually spiral in and burn up. With propellant-free thrusters, you can keep the satellite up as long as you have electric power (meaning as long as the solar panels hold up)
Also, you may be able to get bigger satellites into orbit with smaller rockets, if all you have to do is get the satellite into low-orbit, and let the tether-thruster carry it into the higer orbit that you want. So it takes a few weeks to get there, so what?
Going through some of my old bookmarks. I thought that you would enjoy this.
"- yet one more step towards machines that have no need for humans?"
This could mean safer space travel for humans. A system designed from this could be used on the space station.
Holtz
JeffersonRepublic.com
It really tickles me when an expert's credibility gets completely blown out with one post.
Thanks, I had missed this.
Thanks, vannrox, for the ping.
Kevin, a ping list candidate?
Still just a stupid stunt, and no response has shown otherwise.
More like a flea fart.
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