http://news.cnet.com/8301-17938_105-57609227-1/stamp-size-thrusters-could-propel-small-satellites-into-space/?ttag=fbwp
[quote]MIT professor Paulo Lozano is designing prototype "microthrusters" that would propel pint-size satellites in orbit and into deep space.
The director of MIT's Space Propulsion Laboratory believes such microthrusters and the scaled-down satellites they would power could radically reduce the cost of space missions compared with conventional spacecraft technology.
So-called CubeSat satellites are roughly the size of a Rubik's Cube. Dozens of CubeSats have been put into orbit over the past decade, often as part of university research projects.
But instead of letting them burn up in Earth's atmosphere as their orbits decay, Lozano wants to equip them with tiny thrusters to prolong their usefulness -- and give them new functionality.
The Lego brick-size microthrusters would be installed on CubeSats to propel them in various directions. When a voltage is applied, a liquid propellant in the microthruster emits a stream of ions through tiny nozzles. The charged particles propel the satellite forward.
Four thrusters in this solar-powered ion electrospray propulsion system (iEPS) could provide attitude control and main propulsion for standard "1U" CubeSats, which measure about 4 inches to a side and weigh 2.2 pounds.
"Less than 150 g of propellant would be required by a 1U CubeSat to reach Earth's escape velocity from [low Earth orbit] and explore interplanetary space," the lab says on its Web page.
It might be possible to send a fleet of CubeSats to explore the moons of Jupiter, for instance, for the same price as sending a large spacecraft.[/quote]
What's not to love about this? With a bunch of these, we can essentially explore deeper into space at an insanely small cost! (Well, when compared to the cost now...)
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The high specific impulse still comes at the cost of stupid long amounts of time to build up speed.