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Microthrusters For Small Satellites
An anonymous reader writes "A research team led by Paulo Lozano at MIT's Space Propulsion Lab and Microsystems Technology Lab have shown off a microthruster array capable of powering small satellites. The tiny, flat design could obviate the need for bulky propellant tanks. 'To explain how the thruster works, Lozano invokes the analogy of a tree: Water from the ground is pulled up a tree through a succession of smaller and smaller pores, first in the roots, then up the trunk, and finally through the leaves, where sunshine evaporates the water as gas. Lozano's microthruster works by a similar capillary action: Each layer of metal contains smaller and smaller pores, which passively suck the ionic liquid up through the chip, to the tops of the metallic tips. The group engineered a gold-coated plate over the chip, then applied a voltage, generating an electric field between the plate and the thruster's tips. In response, beams of ions escaped the tips, creating a thrust. The researchers found that an array of 500 tips produces 50 micronewtons of force — an amount of thrust that, on Earth, could only support a small shred of paper. But in zero-gravity space, this tiny force would be enough to propel a two-pound satellite.'"
Do we have satellites in zero-gravity? Hmmm.
How large, in zero-gravity, is a 2 pound satellite?
Something that weighs 2 pounds in orbit would have to have a huge amount of mass. I'm pretty sure they meant 1 kilogram which is a unit of mass. Science writing is really going downhill it seems.
Not really - ion propulsion trades "energy squared" for "propellant flow rate". So the large fuel tank (100 kg, say) has been replaced with a much smaller one, around 1 kg, for the same thrust. Here's the trade details:
1. Trading a 350 Isp Hydrazine thruster for a 35,000 Isp ion drive - it uses 1/100th the propellant for the same total impulse (thrust*time)
2. The thrust decreases dramatically typically - but for small satellite station-keeping that doesn't matter
3. The power requirement/N thrust gets ridiculous - from about 3.5KW/N to 350KW/N
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But in zero-gravity space, this tiny force would be enough to propel a two-pound satellite.
Or a one-pound satellite. Or a ten-pound satellite. Or a hundred-kilogram satellite. Or a planet.
systemd is Roko's Basilisk.
There are three factors that are important for any propulsion system:
1) Thrust - check
2) Wheight - probably very low, hopefully not too important
3) Specific impulse - how much fuel do you need to get that thrust? The higher the velocity of the exhaust, the less fuel you need for a given thrust. And that is exactly what is missing from all sources. Who knows what they had to compromise with in order to scale the whole thing down?
But this thruster seems to be just a new variant on the ion thruster, albeit in a compact form
Thank you for being the first person to post something useful and constructive on the thread. Shame I had to scroll through the usual pedantic know-it-all minutiae about units and mass and weight to get to it.
I swear, /. is going severely downhill in the quality of discussion these days.
Drill baby drill - on Mars
If the analogy doesn't fit, you must (shut the hell up)
For large sets, this will be our guide even unto death, for the LORD will work for each type of data it is applied to...
Actually, I'd been wondering if an array of large-diameter nanotubes could be used to eject ions faster and more efficiently.
In the torque-free environment of space, any amount of force will overcome inertia in an appreciable way. Gravity gradients, solar pressure, lunar and solar gravitational influences, atmospheric drag.
All they're saying is that 50 microNewtons is about the right size for small satellites, regardless of how many pounds-force that satellite might be at sea level. More than likely this is intended for attitude control maneuvers rather than orbit changes, but even in the latter case, small thrusts for long periods in space can be used.
And yes, I am an aerospace engineer.
if you had a sense of humour, you'd be familiar with the sound a 2 pound satellite makes over your head (even in a low earth orbit)
You can't handle the truth.
"The tiny, flat design could obviate the need for bulky propellant tanks."
And instead, replaces them with bulky electrical power sources. There's no free lunch - whether the thrust comes from electricity or from reacting chemicals, it's got to come from somewhere.
Though, if you actually read TFA, you find there actually is a "fuel tank" built into the thruster... But, as the tank is very small, means a very limited lifetime.
Specific Impulse. Discussing a new thruster without giving Isp is about as useful as announcing a "revolutionary networking technology" without giving a bits per second figure: interesting hack, but is it vaguely practical?
The trade is getting energy from substantial mass of fuel which also acts as reaction mass, for energy from the sun and a small reaction mass. Whether the power supply is heavy depends on how much thrust is produced. Granted the sun is heavy, but for satellite uses you don't have to take it with you.
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It depends Is 2 pounds the satellites mass or its weight?
Sleep your way to a whiter smile...date a dentist!
you know what's funny, it's how stupid you are while thinking that you have said something intelligent or insightful.
There is pound-mass and there is pound-force, but that is irrelevant even, because the joke had nothing to do with it, so you are also very dim.
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