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NASA Launches Micro Solar Sail
greyarea67 writes with news that NASA has successfully used a "microsatellite" (a term given to satellites weighing between 10kg and 100kg) to deploy a "nanosatellite" (a term given to satellites weighing between 1kg and 10kg). The deployed object, the first of six in the microsatellite's payload, was the NanoSail-D flight unit. NanoSail-D masses 4kg and is "about the size of a loaf of bread" until it deploys its solar sail.
"...when the NanoSail-D sail is deployed it will use its large sail made of thin polymer material, a material much thinner than a single human hair, to significantly decrease the time to de-orbit the small satellite without the use of propellants as most traditional satellites use. The NanoSail-D flight results will help to mature this technology so it could be used on future large spacecraft missions to aid in de-orbiting space debris created by decommissioned satellites without using valuable mission propellants."
...Sail to the Moon...
San Antonio ??
Someone else will probably beat me to this short bout of pedanticism questioning how micro and nano are applied in this situation (micro-ton?) and highlighting the fact that there are three orders of magnitude separating the micro and nano scale.
Is 1563649 a prime number?
"NanoSail-D flight results will help to mature this technology so it could be used on future large spacecraft missions to aid in de-orbiting space debris created by decommissioned satellites without using valuable mission propellants."
"NanoSail-D flight results will help to mature this technology so it could be used on future MILITARYmissions to aid in DELIVERING
WARHEADS without INFRARED DETECTION."
The story editors need to read Pentagongate.
Yours In Moscow,
Kilgore Trout
...why were satellites designed so that they would still remain in orbit after "death." Are there still dead satellites in orbit because of malfunction, did engineers not foresee this problem (hard to believe), or was it not feasible to include deorbit mechanisms in design?
"about the size of a loaf of bread", "much thinner than a single human hair". How many football fields will this satellite travel? How many Statue of Liberties high will this thing orbit?
Does this qualify as a "solar sail"? It seems more like it's a fractional atmosphere parachute. Solar sails are intended to interact with solar wind particles, but it would seem to be almost useless in an orbital situation, half the orbit you'd be head into the solar wind, half you'd have it at your back accellerating you. In either case, the solar wind is an exceedingly small force, which is why solar sails are proposed on the scale of square miles+. The solar wind would be dwarfed by stray atmospheric particles in earth orbit.
This seems like they're using the term "solar sail" when they mean something completely different.
I give it a millimeh (a term given to bemused indifference ranging between 0.0001 and 0.001 mehs).
Actually, you can use a solar sail to accelerate yourself out of earth orbit. It's just a matter of orienting the sail parralel to the sun's radiation vector when it's head on, and perpendicular to it when it's in a position to increase your orbital velocity.
Actually, if the object is in low Earth orbit, it wouldn't be encountering very much solar wind regardless of whether the satellite is in Earth's shadow or not. The planet's magnetic field deflects most of the solar wind away at an altitude far above the orbits of most satellites.
Even so, your point is valid; this is not, by any definition, a solar sail. It is a parachute.
OK, it might be easier to test a solar sail by de-orbiting something faster, and it's important to not contribute further to orbital debris. But the interesting direction is UP! Get the thing from low-orbit to a higher orbit with the solar sail, like the Japanese have started to do with the IKAROS satellite. Can we get from LEO to geostationary with a solar sail? Can we use it to maintain an orbit without propellant? That means less mass for delta-V to lift out of the atmosphere, and thus less cost but maybe a long time to achieve the final orbit.
Bruce Perens.
While you will get a balanced force for a sail that is normal to the sun, once you move it slightly off normal, and account for shadow periods, you'll get an unbalanced force that will have a deterministic secular effect on the orbit. And it will be non-normal unless you're actively maintaining the attitude.
Also, the sail is definitely not small. Its 100 square feet for a tiny satellite. Obviously if you wanted to use one as a failsafe mechanism for a large GEO comm bird you'd need something larger.
I agree. It seems atmospheric drag would have a far greater affect than solar winds and or light.
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'This seems like they're using the term "solar sail" when they mean something completely different.'
Inconceivable!
While you will get a balanced force for a sail that is normal to the sun, once you move it slightly off normal, and account for shadow periods, you'll get an unbalanced force that will have a deterministic secular effect on the orbit. And it will be non-normal unless you're actively maintaining the attitude.
All of which would be swamped by the effects of atmospheric drag. This thing is a parachute, not a solar sail.
When our name is on the back of your car, we're behind you all the way!
Depends on your altitude and attitude. In this orbit, yes, atmospheric drag is going to have a stronger effect, but in higher orbits, the solar effects could be effective for a well-designed system to facilitate disposal. I may try and look at that later if I have some free time (I'm actually doing simulations of spacecraft atmospheric passes right now...).
But I agree at this altitude the sail is deployed to enhance atmospheric drag and is mischaracterized by the summary as a solar sail. TFA says nothing about it being a solar sail.
TFA says nothing about it being a solar sail.
actually, TFA uses exactly the term "Solar sail" to describe this project.
In their defense, there seems to be three distinct goals for this project that have been combined into a single experiment, and then reported on badly.
One project is the ejecting of the pico-satellite from the micro-satellite.
Another is testing the deployment process for the "solar sail".
lastly, there's testing the hypothesis of increasing drag on to reduce oribital decay time.
Add one sloppy bit of science reporting, mix thoroughly, print results. (...profit!)
Actually, you can use a solar sail to accelerate yourself out of earth orbit. It's just a matter of orienting the sail parralel to the sun's radiation vector when it's head on, and perpendicular to it when it's in a position to increase your orbital velocity.
While maybe possible in theory, it's hard to imagine it being practical. ignoring the size issue and the clutter in earth orbit, the amount of time it would take for a solar sail to escape the earth gravity well seems like it would be incredibly long.
I've always heard solar sails proposed as the long term/low cost option for propulsion AFTER having been boosted out of the well by conventional propulsion.
Solar winds are deflected by the Earth's magnetic field at a distance of roughly 60,000km. In contrast, the orbits of geostationary satellites are only 35,000 km.
When our name is on the back of your car, we're behind you all the way!
Correct me if I'm wrong but most of the force from a solar sail is from reflectance of photons, not solar wind particles, thus why understanding the reflectivity of your surfaces is critical to understanding solar radiation pressure effects.
I dont think in most cases you even bother to consider the solar wind as far as trajectory analysis goes (obviously its more important for electronic protection).
Hopefully the micro solar sail will give us enough power until Kirk returns with some humpbacks.
What you want is a way to get SOMETHING to slow down. You can get that by getting something ELSE to speed up. Find two satellites you want to toss, connect with a tether cable, spin them up, cast one forward in orbit and the other backward. Presto, the backward one de-orbits, the other may attain escape and go elsewhere (lots of choices). Cost? only the cost of rotational energy - a tiny amount compared to anything else, can be got from a solar panel. (No propellent cost at all).
You can get out of a circular Earth orbit with a solar sail, if you want, by altering the albedo of different parts of the sail (this is how the Japanese sail steers itself). Air particles are a larger effect than light pressure below about 1000km altitude, so NanoSail-D could never do this.
Also, getting out of LEO this way is really, really slow, and results in you spending a long time in the van Allen belts. You can harden your electronics against this but you would avoid it if you can, hence why the Japanese deployed their sail after trans-Venus injection.
If we can put a man on the moon, why can't we shoot people for Apollo-related non-sequiturs?
No, in this particular mission it isn't really being used as a solar sail at all. The material used for the sail is, in fact, what a solar sail would be/will be made out of. The idea of this mission is to demo the structural properties of the material so that there is some scientific data on hand that can be used for reference when designing future missions. This particular bird is, as you are saying, simply using solar sail material to act as an atmospheric parachute to induce drag. Ideally, after this mission flies, NASA will put together a bird with a real solar sail made of the exact same material that will use it for navigation due to interaction with the sun.
Also, this mission will be used to test out NASA's deployment mechanism for proposed solar sails. From a mechanical engineering standpoint, it's actually a pretty cool mechanism.
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While maybe possible in theory, it's hard to imagine it being practical. ignoring the size issue and the clutter in earth orbit, the amount of time it would take for a solar sail to escape the earth gravity well seems like it would be incredibly long.
What you find difficult or easy to imagine is not an arbiter of reality. It has zero epistemic value, and it's a little weird you would bring it up.
I find it hard to imagine anyone would be dumb enough to engage in a war of choice in Iraq, but one demonstrably exists. I find it hard to imagine that people think what they find hard or easy to imagine has any bearing whatsoever on what is real, but clearly lots of people think that.
Science has been transforming the world for three hundred years, and is based on the discipline of publically testing ideas by systematic observation, controlled experiment, and consistent, precise mathematics. It works because it recognizes that what anyone can or cannot imagine is irrelevant to what is real.
In the case of solar sails, they can lift a satelite out of Earth orbit in days to weeks, depending on the initial orbit. From geostationary it's a couple of days. From LEO it's more in the month-ish range.
Typical solar sail configurations should be able to produce 1/1000 of a g: 0.01 m/s^2. So 1 m/s delta v after 100 seconds, 36 m/s after an hour, 3600 m/s after 100 hours (4 days), 36000 m/s after five or six weeks. For missions to other planets that would last years, that's a trivial amount of time.
Imagine that!
Blasphemy is a human right. Blasphemophobia kills.
No, I'm the one who's wrong here. As you say, solar sails work from radiation pressure, not solar wind. It's a common (and understandable) mistake made by about half the websites that talk about solar sails. (Although, if light can push a sail around, I think stream of particles
The radiation pressure on a ten foot square works out to 8.5*10^-5 newtons. In comparison, the atmospheric drag on the shuttle was 0.4 newtons. Assuming this satellite has a tenth of the surface area of the shuttle, the drag would be 0.04 newtons, or about 500 times the force of the solar sail effect.
When our name is on the back of your car, we're behind you all the way!