Giving CubeSats Electric Propulsion 74
eldavojohn writes "Thirteen picosatellites were launched back in June of 2006 with the price coming down dramatically in the years since. But the Rubik's cube sized devices have no mobility, meaning once they're put in orbit, they stay in that orbit. The big problem is that traditional chemical propulsion systems are too large for ten-centimeter sided cubes weighing a kilogram. A new electric propulsion system designed by Paulo Lozano of MIT might change that. "
"The article explains how it works: 'Lozano's design relies on electrospraying, a physics process that uses electricity to extract positive and negative ions from a liquid salt that is created in a laboratory and serves as the system's propellant. The liquid contains no solvent, such as water, and can be charged electrically with no heat involved. Whereas other electric propulsion systems charge the ions in a chamber on the satellite, the ionic liquid in Lozano's design has already been charged on the ground, which is why his system doesn't need a chamber. Electricity is then converted from the main power source of the CubeSat, typically batteries or a solar panel, and applied to a tiny structure roughly the size of a postage stamp. This thin panel is made of about 1,000 porous metal structures that resemble needles and have several grams of the ionic liquid on them. By applying voltage to the needles, an electric field is created that extracts the ions from the liquid, accelerates them at very high speeds and forces them to fly away. This process creates an ionic force strong enough to produce thrust.'"
Re:why even use propelant ? (Score:4, Interesting)
Larger satellite use magnetorquers to orient themselves in orbit. To use magnetics as a drive system, your spacecraft would have to be long so you could pulse a magnetic field down the length of it (think of it as a rail gun in reverse).
Ion drive (Score:3, Interesting)
Sounds like a variant of an ion drive [wikipedia.org], which have been around since the 50's.
Re:PACKING RATIO (Score:5, Interesting)
Cubesats are never the primary payload. They're individually tiny, so they're launched in bunches as a secondary payload along with something else much bigger. Their cubical shape makes for easy fabrication of both the satellite itself and the spring-loaded launcher that they're packed in for the launch. Since they're basically freeloading on some other launch, using empty space that would otherwise be completely wasted, their own form factor doesn't really matter much. They fit in the odd bits of leftover space that a typical satellite leaves inside a rocket faring.
Re:why even use propelant ? (Score:3, Interesting)
And the usual answer to that is to unreel a tether after achieving orbit. In theory a picosatellite could contain a tether on a small spool. Admittedly getting such a thin tether to unwind properly might be difficult...