Giving CubeSats Electric Propulsion

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.'"

Comments

Launched, yes. Orbited, not so much.

[$RANDOMLUSER]

The engines on the the DNEPR-1 launched on 26 July 2006 shut down 86 seconds into the flight. It crashed approximately 25 km downrange. So, quite a bit of "bang" for your buck.

Re:Launched, yes. Orbited, not so much.

[Avacar]

This should be part of the intro - none of these satellites currently exist. They were all blown up during their failed launch.

Actually that's incorrect. My predecessors had a cubesat on the DNEPR-1 launch; yes it blew up. That said, it was neither the first rocket to carry cubesats, nor by any means the last. TFA is correct in saying there are at least a dozen of these satellites in orbit right now, although many are now past their operation a life, and are waiting to naturally burn up. Saying that "none of these exist" is a bit of a misnomer as well, since there are cubesats waiting for launch in labs all around the world; I myself have two that will likely be going up in about three years from now.

TFA is correct, however, in saying that no cubesat currently has a propulsion system. It is wrong, however, in saying that no one else is working on this problem; in fact that is the very topic of my own research. I'd be much more impressed, however, if we could see simulations of the corrected orbits, estimated increases in lifetime, and, best yet, a working prototype. Claiming you can do this is bold; it is not an easy problem. Chemical rockets, and even 'standard' electric propulsion are become well-characterized solutions. Cubesat propulsion is on a completely different level, based on both the weakness of the thrusters, and the relatively low masses of the satellites. I feel this is a bit premature to be posted on the front of slashdot; this should have gone up in the 4-5 months TFA claims it will take to get a working prototype. That said, I applaud the novel approach. I hope it works, 'cause I know I'd buy one.

Re:CubeSats are a revolution

[wizardforce]

This is where electrodynamic tethers and laser brooms come in handy.

Re:CubeSats are a revolution

[QuantumG]

Well, despite what the article says, most CubeSats are launched into deteriorating orbits which eventually burn up.

As for radar, yes, it's nice to be able to get ground confirmation and CubeSats are more than big enough to do that, especially considering they are deployed on-orbit in clusters.

Re:Pico

[Anonymous Coward]

Having recently attended a small satellite conference, I learned that when it comes to satellites, micro- refers to satellites under 100 kg, nano- refers to satellites under 10 kg, and pico- refers to satellites under 1 kg. Since the nominal mass of a 1-unit CubeSat is 1 kg, they are typically called picosatellites.

Re:CubeSats are a revolution

[xquercus]

The cubesat platform has provided a means for quite a few orbiting radio amateur experiments.

Re:Pico

[twostar]

Picosatellite is just a general classification in the satellite community of 1kg. "Small" satellites are anything from 500kg down. Notice it's not Pico- kg but pico-satellite. http://en.wikipedia.org/wiki/Small_satellite

Re:CubeSats are a revolution

[Kral_Blbec]

FTA

The Air Force and other government agencies are interested in using CubeSats that can move between different orbits in space, and more specifically, that have the propulsion required to reenter Earth’s atmosphere and destroy themselves at the end of their mission (thereby keeping them from becoming “space junk”).

Re:Pico

[Areyoukiddingme]

Uh, Yoda would have said "Sense it makes, no?"

Too large for a Rubik's cube

[Jeremy Erwin]

Each edge of a Rubik's cube is 5.7 cm long. The cubesats are 5.5 times as large.

Re:CubeSats are a revolution

[khallow]

ISP of 3500 s and 5.6 micronewtons of thrust. Not bad for a station keeping device on a 10 cm cube (generates roughly 3 m/s of delta v over a month, if the cube is dense as solid iron), but it's going to be vastly slow (unless, of course, you have an array of them) for other uses.

Re:why even use propelant ?

[Niffux]

DTUsat-I, a CubeSat attempted this a few years ago. Unfortunately contact was never established with the satellite so it has not actually been tested, but the physical construction is fairly simple.
More info.