Tiny solar sail 'Cubesat' launching with X-37B space plane on Wednesday

[MechAg94]

http://www.foxnews.com/science/2015/05/19/tiny-solar-sail-cubesat-launching-with-x-37b-space-plane-on-wednesday/

I saw this headline on Fox News.  

LightSail is equipped with a solar sail that, once deployed, will cover an area of 344 square feet. But the spacecraft isn't going high enough to do any real sailing on this mission; atmospheric drag will likely pull LightSail down two to 10 days after it unfurls its sail (a move planned to occur 28 days after the cubesat starts flying freely).

But that's just fine, Planetary Society representatives say. This first LightSail flight is a shakeout cruise designed to test out the cubesat's attitude-control and sail systems ahead of a true solar sailing trial with a second LightSail craft in Earth orbit next year.

Some interesting testing though it appears this test won't actually test the sail.

[AJ Dual]

It's going to test deployment etc. of the sail, and as noted, test changing it's orientation etc. (teeny battery/solar powered reaction wheels, or do it with light pressure?) It's not in a high enough orbit, and it's surface area to mass ratio is going to make it a drag-magnet for the residual atmosphere that's still up there, and has many times more impact than the sun's light-pressure.

Even the second one next year isn't going anywhere spectacular. I think they just want to see if they can steer it and lift it to higher orbits etc. just using light pressure.

A series of shakedowns and proof-of-concepts to see what breaks/fails and does or doesn't work before they invest in a bigger sail that'll actually go somewhere. And the interesting thing is much like a sailboat, you can "tack", and fly into the sun. Do things like lift yourself into a higher outbound trajectory, but one that falls back into the inner Solar System if that's where you wanted to go, or angle the sail to cancel out your forward orbital momentum so you "drop" inward towards the sun.

So not just only outbound trajectories are possible. Or it could fling itself inward to pick up speed, then accelerate closer in by Mercury or Venus and then apply full sail on the outbound swing etc.

[KD5NRH]

Isn't beer required for sailing?  How's it going to carry enough for a multi-day trip?

[insert light beer pun here]

[MechAg94]

Isn't beer required for sailing?  How's it going to carry enough for a multi-day trip?

[insert light beer pun here]

Near Beer.  We drink it down here and that is near enough. 

[RoadKingLarry]

Isn't beer required for sailing?  How's it going to carry enough for a multi-day trip?

[insert light beer pun here]

Beer or rum. Either works for me.

I've drawn a blank trying to remember which sci-fi author used the light sail gimmick so many decades ago. One story I remember bits of was that rich guys had light sail space yachts and raced them around the solar system.

[Regolith]

Beer or rum. Either works for me.

I've drawn a blank trying to remember which sci-fi author used the light sail gimmick so many decades ago. One story I remember bits of was that rich guys had light sail space yachts and raced them around the solar system.

Sounds like something David Weber would write...

[Phyphor]

Larry Niven and Jerry Pournelle used it in The Gripping Hand.  One of the characters had a racing yacht.

[RoadKingLarry]

The bit I'm thinking about was a short story but it may have been Niven. I'll have to do some digging.

[AJ Dual]

Larry Niven and Jerry Pournelle used it in The Gripping Hand.  One of the characters had a racing yacht.

I don't remember the racing yacht reference, but I do remember the big plot point in the Mote in God's Eye, being the spot of launch-laser and the light-sail the Motie's tried using to escape their home system the "slow way", because they were stuck there, as the jump-point for the FTL drive was inside the big red-giant one system over, and without the shield tech, their ships kept burning up.

Then when the Motie's light-sail got to the next system, inhabited by humans, they spaced themselves, presumably to try and preserve the secret of the various castes of their race, and the implied threat their unlimited population growth created.

[Headless Thompson Gunner]

I'm a bit curious how they sail "upwind" in space.  Back on good ol' earth, sailing upwind requires playing the wind against the water, it's the lateral resistance of the keel in the water that makes progress upwind possible.  What serves that role in space?.

[Phyphor]

I don't remember the racing yacht reference, but I do remember the big plot point in the Mote in God's Eye, being the spot of launch-laser and the light-sail the Motie's tried using to escape their home system the "slow way", because they were stuck there, as the jump-point for the FTL drive was inside the big red-giant one system over, and without the shield tech, their ships kept burning up.

Then when the Motie's light-sail got to the next system, inhabited by humans, they spaced themselves, presumably to try and preserve the secret of the various castes of their race, and the implied threat their unlimited population growth created.

Yeah, now that I think of it, the light sail in Gripping Hand was more of an in-passing reference.

The yacht in the story is the ship that carried Blain's daughter & her boyfriend(?) to the Mote with the Crazy Eddie Worm.

[AJ Dual]

I'm a bit curious how they sail "upwind" in space.  Back on good ol' earth, sailing upwind requires playing the wind against the water, it's the lateral resistance of the keel in the water that makes progress upwind possible.  What serves that role in space?.

You do it by bouncing the sunlight in the direction of your orbital motion to slow you down so you "fall" inward towards the sun in a tighter orbit. So you can change your trajectory "in" towards the sun.

It's really just Newtonian like any other rocket thrusting against it's orbital motion to "fall inward". So say a solar sail probe is launched from Earth, and its mission is closer to the Sun or Mercury, Venus etc. and unless it's got a massive boost from an upper stage, once kicked out of orbiting around Earth itself, it's still mainly in something close to Earth's orbit around the sun. So by bouncing sunlight in the opposite direction, it is essentially retro-braking and falls inward. Bouncing the light the other way would increase it's orbital velocity and it would spiral outward towards the outer Solar System.