Finnish Scientists Push Experimental Solar Sail Effort

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  Space News Business

Finnish Scientists Push Experimental Solar Sail Effort

By JEREMY HSU
Space News Correspondent
posted: 28 April 2008
01:42 pm ET





New York –
An electrically
charged solar sail with a possible “turbo” option may be ready for its first space trials in three years if scientists in Finland have their way.

 

The Finnish invention would use long, positively
�charged tethers to ride the solar wind, without the need for any sort of fuel or propellant.

 

“A flight out of the solar system to measure the gas, dust, plasma and magnetic field in the undisturbed interstellar space would perhaps be the ‘flagship’ thing to do,” said Pekka Janhunen, a researcher developing the sail at the Finnish Meteorological Institute.

The solar sail’s debut would involve a smaller model with
8-kilometer
�long tethers riding in a highly elliptical Earth orbit. That would allow Janhunen and others to gauge the force of the solar wind on the spacecraft with an accelerometer.

 

“The mission would validate and calibrate our theory and enable us to design full-scale missions with accurate and experimentally verified numbers for predicted thrust,” Janhunen said
.

 

Two solar panels would power an electron gun that keeps the spacecraft tethers charged, creating propulsion from the similarly charged solar wind pushing against the sail. Researchers are looking into aluminum or copper alloy wires for the tethers.

 

The maiden mission also would
test a concept to increase the thrust from the solar wind, called radio frequency electron heating.

The subscale mission also would
test a “turbo” charge for the solar sail. Radio-frequency waves could excite the solar wind particles through electron heating, which might boost the thrust created. The concept is difficult to simulate or analyze in theory, but should be easy to test in space,
Janhunen said.

 

Whether the first test gets off the ground depends on securing almost 5 million euros ($7.9
�million)
. Researchers from Finland, Germany, Sweden, Russia
�and Italy
currently are developing various components of the solar sail.

 

Previous efforts to deploy and test solar sails foundered due to launch failures and mishaps. A joint Russian-U.S. effort in 2005 was doomed by rocket booster failure less than
2 minutes after launch. Two previous Russian efforts in 2001 and 1999 also failed, though Japan successfully deployed a small solar sail prototype in 2004.

 

Other sail concepts have suggested using microwaves beamed from Earth to push spacecraft up to record speeds, instead of riding the solar wind.

 

However, a successful solar sail could have big payoffs by making deep space missions cheaper without fuel requirements. A fleet of solar sail spacecraft
also could lower significantly
the cost of transporting material within the solar system.

 

“Fetching water ice from asteroids to produce rocket propellant on Earth orbit would probably be one sensible application of that capability,” Janhunen told Space News
. “Producing rocket fuel on orbit means that one doesn’t have to lift it from Earth, which could make all space activities cheaper – except for those in low Earth orbit.”

Solar sails alone will not pave the way for further space exploration –
�other developments such as cheaper and more reusable launch vehicles are necessary. But proving solar sail technology would help extend mankind’s reach into the solar system.

 

“Starting the long-awaited asteroid resource utilization could be significant for the longer-term well-being and survival of our civilization on this planet,” Janhunen said.

Comments: jhsu@space.com