Tiny Spacecraft Point to Future Sails

by Paul Gilster on April 28, 2011

Spacecraft no more than an inch square will fly aboard the next (and last) Shuttle flight to the International Space Station. The work of Mason Peck (Cornell University), the micro-satellites weigh in at less than one ten-millionth of the mass of the original Sputnik, yet can accomodate all the systems we associate with a spacecraft — power, propulsion, communications — on a single microchip. We’ve looked at Peck’s work in previous Centauri Dreams essays (see this one on ‘smart dust’), but it’s great to see some of his concepts put into an actual mission plan for testing in Earth orbit.

What Peck has in mind with the spacecraft he calls ‘Sprite’ is ultimately to create a satellite with different flight dynamics from other spacecraft. Sure, we can miniaturize our electronics and create satellites with small form factors — CubeSats come to mind — but Peck’s craft call up a different analogy:

“Their small size allows them to travel like space dust,” said Peck. “Blown by solar winds, they can ‘sail’ to distant locations without fuel. We’re actually trying to create a new capability and build it from the ground up. We want to learn what’s the bare minimum we can design for communication from space.”

Not that the three Sprite chips scheduled for launch tomorrow (April 29) are going to be making any such journeys. They will be mounted on the Materials International Space Station Experiment (MISSE-8) pallet, which will in turn be attached to the ISS. The idea is to expose the chips to space conditions to see how their systems hold up. The MISSE-8 panel will be returned to Earth after a few years, but while they are in space, the three prototypes, built by Cornell students under Peck’s direction, can be tracked individually from their transmissions.

Image: Three prototypes of the chip satellites, named ‘Sprite,’ will be mounted on the International Space Station and are designed to blow in the solar wind and collect data. Credit: Mason Peck / Cornell University.

To see what Peck has in mind for future applications, consider the behavior of dust in our Solar System. We know that for particles at these scales, solar pressure and electrostatic forces are as significant as gravity in producing unusual orbits. Some dust actually leaves the Solar System on an interstellar trajectory, while other particles achieve stable orbits around the Sun, and some particles simply fall to the surface of planets. Peck has been talking for years now about putting the orbital dynamics of extremely small bodies (up to 100 µm in size) to work on tiny spacecraft like Sprite. Such a self-sustaining spacecraft should be able to take advantage of not only photon momentum but the solar wind, unconstrained by the need to carry onboard fuel.

For now, the Sprites being sent to the ISS will have a narrower target, to collect information about the solar wind’s chemistry, radiation and particle impacts on the chips. But they are demonstrations of our ability to pack power, attitude control, communications and more onto a microchip capable of traveling in a non-Keplerian orbit. And what they point to is a different take on the solar sail, one in which it is miniaturized and integrated with onboard spacecraft systems. Such a tiny sail is capable of things that a more conventional design is not. Consider what happens in the presence of a magnetic field, as outlined on this Cornell website:

By artificially charging a spacecraft that is orbiting a planetary magnetic field, we can achieve Lorentz Augmented Orbits (LAO). Here, a spacecraft’s rotating magnetic field transfers energy and momentum to and from a planet via the Lorentz force. LAO offers opportunities that solar-pressure propulsion does not because it requires a magnetic field to operate. This interaction enables energy change maneuvers at outer planets, notably Jupiter with its dense magnetic field, where solar-pressure is too weak to be of much benefit. We show that high charge-to-mass ratios are significantly easier to achieve and maintain at reduced length scales.

And when it comes to reaching the surface of another world, such spacecraft come into their own:

Exogenic dust gently lands on the surface of the Earth while its larger meteorite cousins rapidly ablate in the upper atmosphere. At extremely small length scales, the surface area of the dust can efficiently radiate away the heat generated by aerodynamic friction, even at entry velocities. We seek to use similar geometries and scales to design a passive entry vehicle capable of safely gliding or fluttering down to the surface of neighboring planets.

Peck even considers interstellar possibilities for future generations of Sprites, in which a chain of the tiny spacecraft move away from the Solar System and report data back to Earth through communications relays between each subsequent craft. The tests aboard the ISS are the first chance for the Sprite concept to prove its survivability in space, and Centauri Dreams congratulates Cornell students Zac Manchester, Ryan Zhou and doctoral candidate Justin Atchison on completing the prototypes that will fly aboard Endeavour. Success there could lead to a whole new way of thinking about propellantless propulsion and micro-scale spacecraft.

Among the papers on this work, Atchison and Peck, “A Millimeter-Scale Lorentz-Propelled Spacecraft,” AIAA AIAA Guidance, Navigation and Control Conference and Exhibit (2007) is the place to begin. It’s available online. A Cornell University news release is also available.

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Eniac April 28, 2011 at 19:17

This is a cool concept, but not without a few caveats:

Light sails of any kind or size can only have appreciable acceleration if they are no more than a few microns thick in the direction of the light. I don’t think microchips can be made thin like that at this time, but perhaps in the near future.

Being thin at the same time excludes shielding from radiation, so these sprites will have to be resistant in some other way. Near-relativistic velocities are out of the question, I think. The interstellar medium, tenuous as it is, is too dense for a micron-sized object to punch through at a considerable fraction of c, unscathed.

Lastly, small size severely limits the amount of radio power that can be generated, so the relay chain concept, which I love, is probably easier to realize with large probes. I do not think a microchip could possibly “phone home” even from Earth orbit, much less from outside the solar system.

Alex Tolley April 28, 2011 at 19:59

Initially I thought that this was a very limited idea. The types of data transmitted would be extremely few and the bandwidth almost non-existent. The idea that these devices could navigate the radiation belts of Jupiter without frying seemed absurd.

But on reflection, this is a classic “just good enough” cheap technology that might challenge macro probes. Chip sizes and capabilities will continue to get a Moore’s law impetus, and we’ve seen increasingly more sophisticated chip based devices, from physical sensors to chemical labs. Print these out by the billions and let the survivors send data from where they may, might be a very interesting example of “Fast, Cheap and Out of Control”.

Millions rolling over Mars in te winds looking for life with simple molecular sensors might be an example, as might others doing something similar in Jupiter’s atmosphere.

And I love this as an example of one explanation of the Fermi paradox. Tiny, almost invisible sensors like these may already be everywhere, if we but looked very carefully…

David April 28, 2011 at 20:41

Couldn’t the chips be on the rim of the sail?
How fast could our current laser technology push such a sail
How fast could a Saturn five blasing off from an asteroid accelerate a chip?

Adam April 29, 2011 at 5:55

Alex T
Alien micro-probes we can see would indicate an amateur effort. It’s the ones we can’t see that are really impressive :-)

ljk April 30, 2011 at 11:06

One signal herds microbot swarm

By John Roach

With the application of a single electrical signal, researchers can control swarms of tiny robots to assemble themselves into structures.

“We are controlling these robots kind of like remote controlled cars,” Igor Paprotny, a postdoctoral scientist at the University of California at Berkeley who is co-leading the research effort, told me Friday.

Instead of one controller transmitting a signal to steer one car, the signal controls several cars at once, sending each in a slightly different direction.

Full article here:

http://cosmiclog.msnbc.msn.com/_news/2011/04/29/6556989-one-signal-herds-microbot-swarm?email=html

Rob Henry April 30, 2011 at 20:25

Alex Tolley, your offhand speculation on our planet being observed through nanobots is worth a glance if it is testable. It would be more worthy the easier the test, and that set me wondering.

Given that the most of the interesting information is on our surface, could we expect that the absorption of light is coupled to an unusual non-biological chemical reaction in places of interest? Should we look for extremely low intensity radio signals of low Shannon entropy emanating from unpopulated regions of the Earth? Given that these probes could be more optimally configured if they transmitted to the Moon rather than Earth’s L4 or L5 could we expect there to be an easier to detect data collection and retransmission point smack in the centre of the Moon’s near side?

Alex Tolley May 1, 2011 at 23:41

@Rob Henry.

“Should we look for extremely low intensity radio signals of low Shannon entropy emanating from unpopulated regions of the Earth?”

I assume low entropy rather than high entropy encoded signals to stand out from the background? Could such signals be distinguished from human transmissions? Perhaps they could use some other transmission mechanism, e.g. quantum entanglement? Is there a way to test such a speculation?

Shawn May 11, 2011 at 1:57

I’ve been reading Centauri Dreams for several years now. I’m actually working on one of Dr. Peck’s other projects, and attended a presentation on this one by Zac just a couple of weeks ago. It’s really interesting to see this up here.

Another part of what this mission is supposed to demonstrate is the chip’s communication abilities.

Paul Gilster May 11, 2011 at 7:34

Shawn, great to have you here, and please feel free to weigh in any time on your work with Dr. Peck as it relates to space issues. I’ve discussed his work a few times in the past — these stories are in the archives. Great work you’re doing at Cornell, so keep us posted on any new developments please!

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