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Relativistic Navigation Needed For Solar Sails
KentuckyFC writes "Last year, physicists calculated that a solar sail about a kilometer across with a mass of 300 kg (including 150 kg of payload) would have a peak acceleration of roughly 0.6g if released about 0.1AU from the Sun, where the radiation pressure is highest. That kind of acceleration could take it to the heliopause — the boundary between the Solar System and interstellar space — in only 2.5 years; a distance of 200 AU. In 30 years, it could travel 2500AU, far enough to explore the Oort Cloud. But the team has discovered a problem. Ordinary Newtonian physics just doesn't cut it for the kind of navigational calculations needed for this journey. Because the sail has to be released so close to the Sun, it becomes subject to the effects of general relativity. And although the errors these introduce are small, they become magnified over the course of a long journey, sending the sail roughly 1 million kilometers off course by the time it reaches the Oort Cloud. What these guys are saying is that if ever such a sail is launched (and the earliest estimate is 2040), the navigators will have to be proficient in a new discipline of relativistic navigation."
Pioneer 10 has been off-course for a while now. Maybe the trick for reaching the Oort Cloud is to aim for 1 million kilometers to the left.
Would that be an RTG powered ion thruster? or do you make holes in the sail that are opened and closed by tiny articulated motors?
Tsukasa: All I really want, is to be left alone...
The probability of it getting all the way there without one single part of the 1 KM sail getting hit by any single piece of space rock or other debris: 0%
Dream on, space sailors. It's an idiotic idea and always will be.
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It can't work like a sailboat does... steering partly into the wind, or changing the sail angle to alter the thrust exerted. There's no resistive force to work against, so it just kind of goes where it is taken.
SIG: HUP
Why not? Reel in the shrouds on one side and lengthen them on the other and the whole sail is tilted with respect to the capsule, and you start to change course. You can't tack (I think) but a broad reach should work.
None of them can see the clouds; The polished wings don't care.
Actually, if they're roughly a million km apart, and you miss one by a million km... you're in the vicinity of another one.
Now missing by *half* a million km... that'd suck.
I can understand why it would be nice to start off a solar-sail-based craft at one-tenth AU from the Sun; more light pressure = more acceleration. Thing is, it will almost certainly be starting out from Earth. You'd need to accelerate it just to drop it down to 0.1 AU. Wouldn't it be more efficient to use that acceleration to throw it outward instead of inward? Anyone care to calculate this?
The only force acting on a solar sail is outwards from the sun. If the sail is angled the force would be reduced (less cross-sectional area), but the direction of the force would remain the same. A sailboat can only turn because it has a keel that exerts force against the relatively-motionless water normal to its direction of motion. There is nothing to push against in space.
The only way to move in a direction other than away from the sun is to employ alternate propulsion, or to somehow find another source of light (such as the concept of getting sunward force by detaching a reflector that bounces sunlight back at the far side of the sail). Keeping everything aligned would be very tricky.
No, the real question is HOW ARE WE GOING TO GET THE SOLAR SAIL THERE. .1 AU from the sun? How hot is that? And dragging the solar sail all the way there will take a fair amount of energy, no?
Something I've always wondered about solar sails is, can they go towards the sun or what?
Pfft, and give up the chance to have an unknown exotic effect named after you? Small price to pay my friend! Did you think all those crazy radiations and particles from Star Trek were named after unmanned probes???