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View Full Version : Relativistic Navigation Needed for Solar Sails



Argos
2009-Aug-20, 02:09 PM
Interesting (http://www.technologyreview.com/blog/arxiv/24007/).


By one calculation, a solar sail with a radius of about a kilometer and a mass of 300 kg (including 150 kg of payload) would have a peak acceleration of about 0.6 g if released on a parabolic trajectory about 0.1 astronomical unit (AU) from the sun (where the radiation pressure is higher).That kind of acceleration would take it beyond the Kuiper belt to the heliopause, the boundary between the solar system and interstellar space (and a distance of 200 AU), in only 2.5 years (...) ordinary Newtonian physics just doesn't cut it for this kind of journey.

cjameshuff
2009-Aug-20, 04:02 PM
Interesting (http://www.technologyreview.com/blog/arxiv/24007/).

They seem somewhat lacking in a sense of scale. They talk about a million km as though it were a lot of distance, when they're talking about the probe going 30 thousand times that distance from the sun. That's 6.9 arcseconds off course, and less than 13 m/s of error.

It's interesting that the effects are that notable, but it's not like the craft will fly wildly off course due to relativistic effects. Given how sensitive the outbound trajectory will be to trajectory errors on the way in, if it is to fly past a specific target, the craft will probably have to correct bigger errors on its way out. If it's not doing such a flyby, the error is likely not an issue.

Argos
2009-Aug-20, 04:06 PM
Sure. By 'interesting' I meant the whole thing: solar sails, relativity, Oort Cloud, interstellar flight, etc.

cjameshuff
2009-Aug-20, 06:56 PM
Sure. By 'interesting' I meant the whole thing: solar sails, relativity, Oort Cloud, interstellar flight, etc.

Certainly. And it's good to see the potential for high speed solar sail missions get more attention, when people tend to focus on the simpler but painfully slow approach of just spiraling outward, often being unaware that faster approaches are possible. It just seemed odd how they represented it as some kind of obstacle, saying things like "such a journey may not be smooth sailing, particularly when it comes to navigation", when the error in velocity they gave is about equal to that achievable by a human sprinter.

samkent
2009-Aug-21, 12:49 AM
That's great for craft leaving the solar system but how do you get back to the inner planets?

Argos
2009-Aug-21, 02:32 PM
That's great for craft leaving the solar system but how do you get back to the inner planets?

You donīt. Thatīs the design for a one-way trip.

mugaliens
2009-Aug-23, 12:57 AM
Fortunately, we've got formulas, programming, and computers which can handle all that relativistic stuff.

trinitree88
2009-Aug-24, 03:16 PM
That's great for craft leaving the solar system but how do you get back to the inner planets?

sam. You wait for a passing solar sail coming from another solar system, switch to hailing frequencies, flash your Federation I.D. card, and Scotty will beam you aboard.

edit: It is kind of odd that none of the putative alien spacecraft reported throughout the years carry that geometry....mostly radial /spherical symmetry...