Talk:Solar sail

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I'm apparently having difficulty with the wording of this bit:

The radiation pressure from the Sun against an absorbing sheet with a mass of 0.8 g/m² is equal to its weight with respect to the Sun's gravity, independent of its distance to the Sun. This mass/area ratio is doubled in the case of perfect reflection.

"doubled" in this case seems to mean that the radiation pressure from the Sun against a perfectly reflecting sheet of 1.6 g/m² is equal to its weight with respect to the Sun's gravity, whereas it should actually be 0.4 g/m² since reflecting photons gives twice the momentum that absorbing them would. So I changed it to "halved", and Patrick reverted with an explanation that seems to be in complete agreement with what led me to make the change in the first place. So I plead confusion. :) Bryan 00:45, 16 Sep 2004 (UTC)

The radiation pressure on an absorbing sheet, regardless of mass, is equal to the gravity on a mass of 0.8 g/m², so there is a balance if that is the actual mass. If the radiation pressure is doubled then it can support a larger weight.--Patrick 07:01, 2004 Sep 16 (UTC)

Ah, lightbulb. That was a very dumb mistake for me to make, but once I made it it really buried itself deeply in my head. Sorry about that. :) Bryan 15:11, 16 Sep 2004 (UTC)

No problem, that can happen to everybody.--Patrick 19:51, 2004 Sep 16 (UTC)

What happened to the Japanese prototypes?

The section on 'current progress' mentions the Japanese prototypes launched in August. Could somebody add something about what happened to them, and whether they were successful? The Singing Badger 17:10, 30 Sep 2004 (UTC)

Please note, "attitude" is correct, stop changing it

This must be the umpteenth time I have had to change "altitude" back into "attitude". Yes, "attitude" is perfectly correct, it controls the direction the spacecraft is turning. There is little need for "altitude" control in space, for one, because there isn't really a "height" in space - its all subjective, but certainly attitude is needed because direction is far more important. Solar sails aren't really meant to be manoeuvred through the atmosphere, where altitude applies, either. Can you people please stop doing this? Its VERY VERY EXASPERATING. "Attitude" IS a valid word for spacecraft. -- Natalinasmpf 14:14, 22 Jun 2005 (UTC)

How about putting some HTML comments <!-- like this --> into the text at places where "attitude" keeps getting changed, explaining that the usage is correct? That way any editor who goes in to change it will definitely see it. I've used this approach before in other articles and it seems to work pretty well. Bryan 06:34, 23 Jun 2005 (UTC)

Hmm, I'll see where I could place it. I just don't want the comments to be too invasive, but it seems worth it anyway.