From Space News :
Small satellites could soon get a boost from a novel in-space propulsion system under development at the U.S. Defense Advanced Research Projects Agency (DARPA).
Called the High Delta-V Experiment, or HiDVE for short, the program aims within the next year or so to complete a 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. If the ground demo goes well, DARPA would look to press on with an in-space demonstration on a dedicated microsatellite.
While spacecraft designers are constantly finding new ways to pack more capabilities into small satellites, matching these little wonders with an affordable launch remains a challenge. Typically, very small satellites have to make due with secondary launch opportunities and frequently are dropped off in non-optimal orbits. Since very small satellites more often than not are built without any meaningful propulsive capability, they must remain there.
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. “We’re trying to say you can throw up little systems … drop them off in an orbit you wouldn’t want them to be in, and let them perform orbit transfers to get them where they need to be,” Kennedy said.
The key enabling technologies for such a system, according to Kennedy, include very high temperature materials and innovative solar receiver and concentrator designs.
This idea has an ancient pedigree to be sure. Greek inventor Heron would be impressed that his principles are employed 2000 years later in moving “artificial moons” (I don’t know what he would’ve called them).
Isaac Asimov used the concept in some of his stories and it has been tossed around as a cheap method of interplanetary propulsion. One such idea was if a vein of water was ever found on the Moon, it could be mined. Then the water would be shot to an orbiting ship using a linear accelerator. The water would be pumped into a huge inner-tube looking, flexible tank. Pump the water through an upgraded nuclear reactor like in a submarine (kudos to Q9). The super-heated steam is shot out through a nozzle and voila, delta-v into a Mars injection Hohmann orbit!
More putt-putt tech! Where’s Zephram Cochran when you need him!