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Cosmos Solar Sail Getting Close To Launch
digitalcaffeine writes "The Guardian is reporting that US and Russian scientists are planning to launch a spacecraft that will use solar sails to move about in space. This venture, called Cosmos 1, is backed by the Planetary Society and Cosmos Studios. The spacecraft, finally due for launch in late 2004 or early 2005, will use a converted SS-N-18 submarine launched ballistic missile fired from beneath the Barents Sea to get it into a 800 x 1000 km elliptical orbit. It will then unfurl its 15m sails and start moving about. So, for all the governments that have been working on a similar project, the first solar-sailed spacecraft is going to be from a private venture." An update on the official site notes that "The world's first solar sail craft is nearing completion. All electronic systems are now flight qualified and were delivered to the spacecraft for final assembly and testing" - we previously reported on the Cosmos Project and the efficacy of solar sails.
weren't these things in the news last week? yup
Earlier this month the Japanesesuccessfully deployed two solar sails.
You're thinking of the Bussard Ramjet. Solar sails use the momentum of light as thrust, as opposed to sucking up interstellar gas. This has all been covered before, recently even, in a Slashdot article about the Japanese solar sail project.
I want to delete my account but Slashdot doesn't allow it.
They can be hard to stop its true, except when approaching another star, which is the ultimate goal for the technology. The wind from Star B pushes back, slowing it down. When it achieves proper orbit speed, it furls the sails.
Within the solar system, the idea is you get the solar wind to push hard enough to achieve a certain speed, then you furl the sails and it coasts into the new orbit.
Moo.
It doesn't seem like it's being put into orbit high enough to avoid this kind of damage. Obviously they thought of this... are the holes inconsequential?
Pretty much. The material is so thin, holes made by space debris won't be larger than the debris itself, and most of the stuff up there is sandgrain size or smaller. Given the size of the sail, a bajillion pinholes won't reduce the effective area much.
"They redundantly repeated themselves over and over again incessantly without end ad infinitum" -- ibid.
Within the solar system, the idea is you get the solar wind to push hard enough to achieve a certain speed, then you furl the sails and it coasts into the new orbit.
Umm, no.
What you want to do is find the optimal use of the available thrust, which is to accellerate continously. The first half of the trip is increasing your velocity relative to your target, and the second half is decreasing velocity to match the target. If you have some other means of slowing down at the end, such as aerobraking or a chemical rocket for orbit insertion, you can spend more of the time speeding up.
-jcr
The only title of honor that a tyrant can grant is "Enemy of the State."
1: Rocket propelled probes so far don't decelerate (much?); they just enter orbit with careful aiming.
2: Tacking in a water-based sailboat uses the water to prevent lateral motion. Try sailing without any sort of keel/centerboard or asymmetric hulls or rudder--you can't go towards the wind this way. Hmmm...I wonder if chemical or ion propulsion could be used as lateral resistance with solar sails in an analog to hybrid gas/electric cars...would there be any economy or advantage to that?
It's much worse than that. Solar sails don't convert the energy of the light, they just receive momentum from the light as it bounces off. The momentum is equal to the energy of the light divided by the speed of light.
This was not a solar powered craft, it was just a test launch using a less than impressive rocket, to test how the sail(s) would unfold in a space environment. A good test, a great project, but not a solar powered craft in any sense of the imagination.
karma capped
well the real world is not full of optimal situations.
Every interplanetary mission to date has been pretty damn close to optimal from an orbital-mechanics standpoint. It's too expensive to go, otherwise.
be happy with creating an orbit with your sail and then furling them up.
You furl them up when you get to your target.
-jcr
The only title of honor that a tyrant can grant is "Enemy of the State."
1) The 5 year solar sail propelled mission to Pluto - is there a way to decelerate as you reach Pluto? Actually, is it really 5 years constant thrust or does the solar sail's thrust decrease as an inverse square law as you get more distant from the sun?
2) Can you sail "upstream" into the solar wind? Is it possible to tack and jibe in a solar sail propelled craft?!
The answer to 2 is no. On the water, you use a rudder to redirect the force on the sail in a different direction. In space, there is no "water" for a rudder to work in, so you can't make any headway against the wind. As a result, the answer to 1 is that you can't slow down using the wind. You could always cut the sail and let the Sun's gravity slow you...
And for those of you wanting a quick description on how sailing "into the wind" works, here it is: If you turn your flat sail at an angle (a1) to the wind (a1 < 90 degrees), it will be pushed in the direction of a1. Now, if you have a rudder starting at a right angle to the sail, you can turn it an angle (a2) toward the wind - this will redirect the force on the sail to push the boat in the direction of a2 (where a2 < 90 degrees). So, if a1+a2 > 90 degrees, you can sail "into the wind".
Tacking into the wind requires a keel, and there's no corollary with a solar sail. You can use the sail to slow down, though, decreasing your orbital energy and bringing you towards the sun.
Why yes, I AM a rocket scientist!
A solar sail has three forces acting on it. Gravity, pulling it towards the primary (planet or the sun), light, pushing it in the direction it aims the sail, and solar wind, pushing it away from the sun. How much you can balance these to "brake" (say, by tacking against solar orbit and moving back towards the sun) is still a matter of speculation.
But the solar sail is *always* accelerating under these forces. If you get a "gust" you simply reduce sail for a while and adjust trim until you're back on the original course. Unlike a rocket, which has a fixed amount of acceleration and if it needs to change its course it can end up lost in space with no fuel, so long as the sail's intact making corrections is merely a matter of time.
There are no breaks, but you CAN use it to manuver in any direction that is not 'up wind'.
No.
http://www.ugcs.caltech.edu/~diedrich/solarsails/
Solar sails can tack, because slowing your orbital velocity moves you closer to the Sun. If you put the sail at an angle such that majority of the light pressure opposes your direction of motion, you will move inward.
So to slow down, you just alter the angle of the sail. Easy enough.
The key question is the weight of the craft. On the Planetary Society website they state that the mass of their craft is 100kg. Sunlight in Earth orbit is able to exert about 9.12 microNewtons of force per square metre. So a sail 15m^2 will be pushed by up to 137 microNewtons. This tiny force applied to the weight of the craft would be able to achieve an acceleration about 1.4microns per second^2. This is a tiny acceleration so it will take a long time to get anywhere but eventually the change in speed will add up. For example, it would take a year to accelerate to 155km/h (approx. 100miles per hour)
They also state some example accelerations but they seem to imply the weight of the craft of only 275 grams so they must be talking about a sail accelerating alone without a payload. The much lower mass makes a huge difference. Such a light craft could achieve 16km/s in a year and make a journey to any planet in the solar system within 5 years.
How? The flight path is always away from the Sun when you're on your way to pluto.
No solar sail could ever fully oppose the Sun's gravity unless it was, I dunno, half the size of Jupiter's orbit or something. OK, maybe not that large. But it'd be huge.
All you're doing is adding to your orbital speed by tilting the sail to accelerate along that direction. So you slowly spiral outwards.
To return, you just do the opposite: slow your rotation, and you spiral inward. You'll have to be careful to alter orbit at several points to circularize it (so you're not going at an insane speed when you hit the inner solar system), but it can be done.
My first thought was the same.
My second thought said 'no'. This had something to do with the way the sails work.
The wind blows against the sail and behind the sail a lower air-pressure (wing effect) pulls the boat forward. But there is also a pushing effect against the sail... So this was BS.
But why does a sailboat sail into the wind? Resistance of the water. It's the shape of the boat, combined with the rudder combined with the resistance of the water that resolves in a forward force. This only works is the bost has enough speed or else it will drift away with the wind.
Well, probably this isn't the whole story, but since the 'water' element lacks in space there is nothing to give the needed friction to sail against the solarwind.
Or at least that's what I think.
Privacy is terrorism.
For the sub launch, another poster helpfully posted the following information:
Near Earth, Solar Sails are particularly suited for high orbital inclination satellite missions. Weather forecasting and global positioning systems would directly benefit from satellites orbiting the poles. Most satellites take advantage of the natural speed of Earth's rotation to boost them into an orbit relatively close to the equatorial plane. Changing the plane requires a large fuel burn for a conventional rocket and greatly increases launch costs. With its small but continuous thrust, a solar sail can reach polar orbits without a massive fuel payload, making them more accessible to scientific research.
It would appear that the scientists want to insert the satellite into a polar orbit, which is confirmed by the fact that the launch point will be the Barents Sea, part of the Arctic Ocean. Since this location is a rather inhospitable region for a conventional launch, the scientists have rather ingeniously selected a submarine launch. The Russian military is highly likely to be the provider making this available for a "reasonable" price, since the mission is scientific in nature. Thus it poses no threat to them, while providing profit where it is much needed.
The reason for using a ballistic missle is that Russia is brimming with extra ballistic missles. They've been decommisioning hundreds, if not thousands of former nuclear missles over the last couple decades. This does not mean they've destroyed the entire missle, merely that the nuclear warheads have been removed, and they're no longer housed in silos or subs for launch against other countries. Since the rockets were designed to carry nuclear payloads, they are both powerful and highly reliable. This obviously makes them an ideal platform for carrying anything into orbit which they can be fitted to carry.
This situation is really a win-win propostion. The scientists get a powerful, highly reliable launch platform and rocket in an inhospitable launch location for likely a rather sweet price. The Russian military gets rid of a decommisoned rocket they just had laying around anyway, and gets to run one of their subs through a launch test complete with the actual launching of a rocket, plus they make a profit on the deal.
// harborpirate
// Slashbots off the starboard bow!
The 15m figure is the length of one of eight triangular vanes that make up the sail. According to the FAQ the total area is 600 square meters.
...on the feasibility of solar sails can be found in one of Robert A. Heinlein's collections: "Expanded Universe."
Solar sails delivering a 0.001G acceleration are feasible - and yes, you *want* constant acceleration, not kick and coast. At that lousy 1/1000G you get a round trip to Pluto in about 3.5 years. Of course that puts the asteroid belt much, much closer...
3 1/2 years is the same time scale wind-powered ships were on in the 1600-1800's. It made the whole Earth accessible then. The solar sails can make the whole Solar system accessible. Moreover, those sails could be modified in place to - oh, let's say - boil off a bit of front end of a convenient asteroid, for convenient insertion into high-Earth orbit for refining and manafacturing.
And it's a damn good way to use up those old boosters! Recycling rules!
Best,
Mal the Elder
These launchers do fail occasionally, just like any other launcher in the business. In fact, this specific type of launcher has failed on the previous attempt to launch a solar sail by the same group!
...it did fail us on July 20 when the 3rd stage motors failed to provide the necessary velocity change and the rocket computer shut overrode the command to separate the spacecraft from the booster...
Yes, it will most likely be visible. You can see satellites every evening. The sail is bigger than the solar panels of most satellites.
Stop worrying about the risks of nuclear power and start worrying about the risks of not using nuclear power.
Snopes
Link
Wikipedia
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