Posted on 09/16/2002 1:10:49 PM PDT by RightWhale
Proposal: Removing Earth's Radiation Belts
By Leonard David
posted: 07:00 am ET 16 September 2002
Here's a cinch of an idea: How about a little Van Allen Belt tightening?
By using highly charged orbiting space tethers, the Earth's cocoon of menacing and deadly radiation belts might be easily and largely aced out.
For one, satellites in the future could live longer not having to fend off the frenzy of energetic particles. Moreover, human-carrying spacecraft would be far safer zooming about in Earth orbit or speeding outward to distant destinations.
The novel concept is called the High Voltage Orbiting Long Tether (HiVOLT) System - a proposal from Tethers Unlimited, Inc. of Lynnwood, Washington.
Beltless Earth
With the launch in 1958 of America's first satellite -- Explorer 1-- a team of scientists led by James Van Allen of the University of Iowa, first detected an inner radiation zone around our planet. It was later dubbed the Van Allen Belt.
Numbers of follow-on spacecraft charted the full extent of radiation belts surrounding Earth.
These are regions of high-energy radiation particles trapped by our planet's magnetic field. Cosmic rays, solar storms, and other processes have led to the creation of inner and outer Van Allen Belts. There's a bottom line to a top-level problem associated with Van Allen Belts: The space radiation environment presents a significant impediment to both human and robotic exploration and development of space.
That's a view shared by Robert Hoyt, Robert Forward, and Bryan Minor - all of Tethers Unlimited.
Hoyt as President, CEO, and chief scientist of the firm, tips his hat to early thinking on high voltage tethers to scatter radiation in space by Valentin Danilov of Krasnoyarsk State University in Russia.
Forward, a long-time tether advocate and space visionary, further fleshed out the idea. He theorized that several tethers could lessen radiation levels within the Van Allen Belts. The Tethers Unlimited team began working on the nitty-gritty details of how their HiVOLT System could operate, making the Earth, in a sense, beltless.
Discharging job
In the HiVOLT system, a long -- nominally some 62 miles (100 kilometers) long conducting, uninsulated tether would be deployed from a satellite in an equatorial, slightly elliptical orbit. A power supply on the satellite would then be used to charge up the tether to a large voltage relative to the space environment. This voltage would create a region of strong electric field near the tether.
Radiation belt particles randomly encountering the tether have their pitch angle increased or decreased. As a net result, there are particles that leave the belt immediately. They decay into the Earth's upper atmosphere.
Tethers Unlimited research shows that five HiVOLT tethers could reduce the equatorial flux of radiation particles to approximately one percent of its initial value - doing its "discharging" job of knocking out particles within about six months.
If workable, immediate benefits
Initial research funding that spawned the HiVOLT idea came from the Air Force Research Laboratory at Kirtland Air Force Base in Albuquerque, New Mexico.
If HiVOLT can be proven workable, Hoyt told SPACE.com, there are several immediate benefits.
"Current satellites are designed to survive long periods despite the space radiation environment. HiVOLT operations would permit spacecraft to last longer. They wouldn't be exposed to such an abusive environment," Hoyt said. Future satellites could potentially be designed with less expensive components and lower levels of redundancy, he said.
Hoyt and his fellow researchers point out that energetic particles will steadily degrade electronics, optics, solar panels and other critical systems by breaking chemical bonds, disrupting crystalline and molecular structures, and by causing localized charge effects.
Higher energy particles in solar events and cosmic rays cause single-event disruptions or damage to electronics. At present, spacecraft systems operating in Earth orbit must be hardened to withstand this radiation environment.
As for humans, radiation particles pose a significant threat, Hoyt said. Zipping through tissue, radiation particles can deposit their energy by ionizing water and proteins, causing cellular damage, modifying DNA, RNA, and proteins in ways that can lead to cancers, immune system disorders, and other maladies, he said.
More study needed
Hoyt is quick to point out that the HiVOLT System needs more study. "There are still some fundamental questions," he said.
For one, is the nature of the interaction of a very high-voltage tether structure with the tenuous plasma present at the altitudes where the system would operate?
A plasma sheath could develop around the tether. If that occurs, the range of the high-voltage tether would be impacted. That same sheath might also affect how much power is necessary to pump into the tether, keeping it at high voltage, Hoyt said.
"Some ground experiments could be done," Hoyt added, "but hopefully those would lead to a low-cost flight experiment to demonstrate the basic principles."
Hoyt and his team are now writing proposals, search for needed research funds to carry out more feasibility work on the HiVOLT System.
Long line of tethers
Tethers Unlimited is not short on ideas about utilizing lengthy tethers.
Among work projects, the group is developing the "Terminator Tether," a low-cost, lightweight system to rapidly deorbit low Earth orbiting satellites at the end of their functional lives.
The research team has also studied the use of rotating tethers. These orbiting tethers may provide a cost-effective means of transporting payloads between low Earth orbit, the Moon's surface, and Mars, with near-zero propellant requirements.
Then there is a small electrodynamic tether system to provide long-duration thrust to a small satellite without consuming precious propellant.
Also, the firm is delving into long-life tethers. The Hoytether can provide reliable high strength, long-life tethers for a variety of uses.
To perform as predicted
NASA research scientist, Les Johnson, Manager of In Space Transportation Technologies at NASA's George C. Marshall Space Flight Center in Huntsville, Alabama , said a range of tether applications are worth exploring and exploiting.
One notion is the Momentum Exchange, Electrodynamic Reboost (MXER) tether propulsion system. This long, rotating tether would snag payloads sent its way, then hurl that cargo toward a final locale.
"It will be a while before MXER tethers are in use as a reusable, in-space facility. Though their potential payoff is very high, there are many issues that remain to be resolved before we can commit to fielding them," Johnson told SPACE.com. "Once we put them in use, however, we will be able to dramatically reduce the size of launch vehicles and increase the mission-level performance of interplanetary spacecraft."
"Electrodynamic tethers are another issue entirely," Johnson said. "I believe we could be using electrodynamic tethers for deorbit applications within the decade and, potentially, as a reboost system for the International Space Station or other large, Earth-orbiting spacecraft," he said.
"The key is to demonstrate that they not only perform as predicted, but that they are reliable and cost-effective," Johnson concluded.
They probably won't last long enough to worry about cleaning them.
Zap! For sale, cheap, one used lightning rod.
The earth's magnetic field will still be there but the contents --charged particles of high energy-- will be drained, which happens naturally anyway. For military applications this might be useful to restore near earth space to somewhat usable conditions quickly after a space radiation attack.
Kinda risky for the Van Allen pants?
This has somewhat of an 'inside joke' feel to it, to my non-technical, somewhat skeptical mind.
;^)
OK, you physicists confused this engineer. How are you shutting off the charged particle source? Is someone gonna turn off the sun? That is where all the charged particles originate from.
This idea is science fiction, and poor science fiction in my opinion.
It's an engineering problem. Sure there is physics involved, plasma fields and Jacobians and all that stuff. But the source will keep pumping charged particles forever for all practical purposes. However, the source is sporadic. Sometimes there is a lot, sometimes there isn't. Once the particles are trapped in the Van Allen Belt as it is today, they stay for a long time. If they were drained quickly, then the level would drop and stay low until the next solar outburst. So, overall, over time, the density of charged particles will be reduced. It's still a sci-fi idea, but a space tether ought to be launched just to see what it does. Who knows, it might work or it might just scare people into learning a little about the universe besides what is on cable tonight.
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