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New propulsion technology reported

Posted by: Ekkehard Augustin - Thu Nov 01, 2007 11:40 am
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New propulsion technology reported 
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Post New propulsion technology reported   Posted on: Thu Nov 01, 2007 11:40 am
The technology is known already as the article says.

According to the article "DARPA Readies Demonstration of Radically New In-Space Propulsion" ( www.space.com/businesstechnology/071029 ... darpa.html ) a
Quote:
ground demonstration of an unconventional propulsion system that uses the heat of the sun to produce enough thrust to push a 10-15 kilogram satellite into a new orbit
is aimed to be completed next year
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or so
.

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If the ground demo goes well, DARPA would look to press on with an in-space demonstration on a dedicated microsatellite.


It's called
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the High Delta-V Experiment, or HiDVE for short
.

The issue
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U.S. Air Force Lt. Col. Fred Kennedy, DARPA's HiDVE program manager, believes that solar thermal propulsion, which uses the warmth of the sun to heat an onboard liquid such as water or ammonia to very high temperatures, and vent it through a nozzle can change that.
to me sounds as if the propellants may be possible that can't be used by other propulsions.

Quote:
The key enabling technologies for such a system, according to Kennedy, include very high temperature materials and innovative solar receiver and concentrator designs.

In late September, DARPA selected two firms, Pratt & Whitney Rocketdyne and SpaceDev, to spend the next six months working on competing solar thermal propulsion designs.


Quote:
"It's essentially a steam kettle," he said. "What you are trying to do is construct a very, very small, perhaps thimble-size, heat exchanger and flow a low molecular weight fluid through it – be it water, ammonia or methane – heat it up to very high temperatures, typically 2,000 to 3,000 degrees Celsius, exhaust it through a nozzle, and that's how you get your thrust."

How much thrust? "You might be able to achieve specific impulses of 400 meters-per-second or better this way," Kennedy said, noting that the space shuttle's liquid hydrogen-fueled main engines deliver 455 meters-per-second of specific impulse.

"You can get close to cryogenic performance on a very small vehicle," Kennedy said of solar thermal's potential.




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Post    Posted on: Thu Nov 01, 2007 1:12 pm
Hmm.. one comment on the last quote.. the Shuttle's main engines deliver 455 seconds of specific impulse and therefore have an exhaust velocity of 4550 meters-per-second.

Solar thermal propulsion is not really a new propulsion technology, the only point is that it wasn't used until now.

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Post    Posted on: Fri Nov 09, 2007 4:15 pm
The military needs some surge capability on some of its craft--so as to make a pass earlier than ground targets have timed out in the hopes of hiding.

However, solar thermal will make such craft better targets for a variety of reasons.

Cold-gas thruster spacecraft with large tankage (via Ares V of course) would be a stealthier choice provided the bus is covered in radar absorbing paint--as Polyus looked to have.


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Post    Posted on: Wed Mar 04, 2009 7:07 pm
What is the farthest distance from the sun this technology might be appied at?

and what ablout using it at Venus or Mercury? Venus would get the chemicals back because of Erth-like gravity - from mercury it would be blown into space I suspect. Might it be possible to install a collector there?



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