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NASA tests solar sail technology
cnn ^ | 05/16/05

Posted on 05/16/2005 5:56:33 PM PDT by KevinDavis

CNN) -- A solar sail that scientists believe could power missions into deep space has passed its first major test.

(Excerpt) Read more at edition.cnn.com ...


TOPICS: Miscellaneous; News/Current Events
KEYWORDS: nasa; solarsail; space

1 posted on 05/16/2005 5:56:34 PM PDT by KevinDavis
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To: RightWhale; Brett66; xrp; gdc314; anymouse; RadioAstronomer; NonZeroSum; jimkress; discostu; ...

2 posted on 05/16/2005 5:57:15 PM PDT by KevinDavis (Let the meek inherit the Earth, the rest of us will explore the stars!)
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To: KevinDavis

Robert L. Forward would have been proud.


3 posted on 05/16/2005 6:03:34 PM PDT by WestVirginiaRebel (Carnac: A siren, a baby and a liberal. Answer: Name three things that whine.)
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To: KevinDavis

I wonder if you can sail upwind like a sailboat ;)


4 posted on 05/16/2005 6:04:39 PM PDT by ProudVet77 (Warning: Frequent sarcastic posts)
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To: KevinDavis
the Planetary Society, a non-profit U.S. group dedicated to promoting space exploration, hopes to launch its first solar sail from a Russian submarine in the next few weeks.

Wonder why this makes me slightly uncomfortable...?

5 posted on 05/16/2005 6:20:04 PM PDT by TXnMA (ATTN, ACLU & NAACP: There's no constitutionally protected right to NOT be offended -- Shove It!)
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To: ProudVet77
I wonder if you can sail upwind like a sailboat ;)

Short answer: Yes.

6 posted on 05/16/2005 6:21:12 PM PDT by marktwain
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To: KevinDavis
[...the Planetary Society, a non-profit U.S. group dedicated to promoting space exploration, hopes to launch its first solar sail from a Russian submarine in the next few weeks.]




On it's way to.....Neptune?
7 posted on 05/16/2005 6:26:14 PM PDT by spinestein (Newsweek lied, people died.)
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To: spinestein; All

Who knows.. I wish the best of luck to them.....


8 posted on 05/16/2005 6:27:16 PM PDT by KevinDavis (Let the meek inherit the Earth, the rest of us will explore the stars!)
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To: KevinDavis

[Solar sail propulsion uses energy from the sun in the same way that a sailing boat is powered by the wind.]


There may be a similarity, but it's hardly "the same way"


9 posted on 05/16/2005 6:28:04 PM PDT by spinestein (Newsweek lied, people died.)
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To: spinestein; All

I think it would be pushed by solar winds..


10 posted on 05/16/2005 6:28:48 PM PDT by KevinDavis (Let the meek inherit the Earth, the rest of us will explore the stars!)
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To: WestVirginiaRebel

"Dragon's Egg" was my favorite story of his.


11 posted on 05/16/2005 6:30:07 PM PDT by spinestein (Newsweek lied, people died.)
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To: marktwain
I wonder if you can sail upwind like a sailboat ;)

Short answer: Yes.

Long answer: No. A sailboat can tack upwind because it uses a keel, daggerboard, or centerboard as leverage against the water. Raise the centerboard on a sailboat, and it will only go directly down wind.

Since there is nothing for an analogous keel to work against in space, you cannot tack upwind.

If said spacecraft had another means of propulsion, such as a solar powered ion engine, or some such, that could be used for upwind or cross wind maneuvering, but that wasn't the question.

12 posted on 05/16/2005 6:42:47 PM PDT by Yo-Yo
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To: ProudVet77

I want to know what the centerboard is going to bite into!


13 posted on 05/16/2005 6:51:47 PM PDT by Redleg Duke (Don't let Terri's death be in vain!)
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To: KevinDavis
Okay, great - it unfolded, in gravity, in a vacuum chamber. Wonderful.

This thing is 400 sq.m. and tares 23kg? That's about 66' square and 50 lbs. Doesn't seem very light to me. The article talks about spans of 80-160 m. (6400-25600 sq.m.) "depending on [sic] the mass of the craft" (OB-viously).

Has anybody seen anything anywhere concerning the pressure of raw sunlight at 1 AU? Can't be much. No matter what the velocity boost from a rocket, the acceleration can't amount to a lot.

14 posted on 05/16/2005 6:52:52 PM PDT by solitas (So what if I support a platform that has fewer flaws than yours? 'Mystic' dual 500 G4's, OSX.3.7)
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To: KevinDavis; Yo-Yo

[Sunlight exerts a very gentle force. The power of sunlight in space at Earth's distance from the sun is between 1.3-1.4 kilowatts per square meter. When you divide 1.4 kilowatts by the speed of light, about 300 million meters per second, the result is very small. A square mirror 1 kilometer on a side would only feel about 9 Newtons or 2 pounds of force.
Fortunately, space is very empty and clean compared to Earth, so there is plenty of room for a 1 kilometer wide sail to maneuver, and there is no noticeable friction to interfere with your 9 Newtons of thrust. A sailboat on Earth wouldn't be going anywhere with that little force because of drag from the water and air. Some rockets can push millions of times harder, but the sail keeps pulling so long as light shines on it. Months or years after the rocket runs out of fuel, the sail is still pulling.]


15 posted on 05/16/2005 6:56:11 PM PDT by spinestein (Newsweek lied, people died.)
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To: solitas; All

That was from this site:

http://www.ugcs.caltech.edu/~diedrich/solarsails/intro/intro.html


16 posted on 05/16/2005 6:58:00 PM PDT by spinestein (Newsweek lied, people died.)
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To: Redleg Duke
I'm a keelboat sailor myself. ;)
But also I wonder how you get more pressure on one side of a sail than the other in a vacuum. Does the solar wind keep the telltales lifted on the leeward side of the sail. ;)
17 posted on 05/16/2005 6:59:01 PM PDT by ProudVet77 (Warning: Frequent sarcastic posts)
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To: KevinDavis

I much prefer the m2ps (mini-magnetosphere plasma propulsion, which is studied by a Dr. Winglee. It uses plasma to make a huge "virtual solar sail". Charged particles from the solar wind push against it. A tiny helicon can make a "sail" 15km in diameter.


18 posted on 05/16/2005 7:14:57 PM PDT by Ahban
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To: Yo-Yo
Since there is nothing for an analogous keel to work against in space, you cannot tack upwind.

The analogy to the force applied to the keel of a boat is gravity. Angle the sail to increase the vector sum in the direction of the orbit, the mean distance from the Sun increases. Reverse the angle to decrease the vector sum in the direction of orbit, the mean distance to the Sun decreases. Remember that the light is reflected off of the sail, so the sum of the impulse is the sum of the incoming and outgoing vectors. As I recall, the optimum angle between the sail and a line to the Sun would be 35.3 degrees.

19 posted on 05/16/2005 7:25:15 PM PDT by marktwain
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To: solitas

Not much. At first.

But there's nothing to slow that 'not much' down, so every second you have your 'sail' unfolded, you add that much more.

Second after second after second. Minute after minute. Hour after hour.

I read a dissertation on it, literally decades ago. It's not the initial velocity thrust that works for you in this case, it's the longevity and the consistancy of the thrust, weak though it may be. Literally days, weeks, months of low but constant thrust, constantly compounding.

Still like Project: ORION better, though. It goes 'boom', big time.

= )


20 posted on 05/16/2005 8:31:52 PM PDT by Mr. Thorne ("But iron, cold iron, shall be master of them all..." Kipling)
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To: ProudVet77
I think that the "sailing analogy" can only hold up so far.

This is definately for the trading tub that can only go before the "wind".

I am reminded of a SciFi novel I read once where they used "magnetic winds" to travel between stars and planets. They were currents in space and the ships used the magnetic fields of the planets to land and take-off, thus limiting them to landing fields between the poles and the 45 degree latitudes.

21 posted on 05/17/2005 5:00:22 AM PDT by Redleg Duke (Don't let Terri's death be in vain!)
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To: marktwain
The analogy to the force applied to the keel of a boat is gravity.

No, that analogy is more like sailing a raft in a straight river with an upstream wind. Raise the sail, you go one direction. Lower the sail, you drift with the water in the other direction. You still only have two directions to travel in.

You can change which radial you are riding on by using gravity of passing planets to change your direction, but once you are outside their influence you will either be heading directly away from or directly towards the Sun.

You can do the same maneuvers that current spacecraft use, where you do several loops around the sun to gain momentum. I don't dispute any of that. I just disputed that you can tack upwind with a solar sail like you can in a sailboat.

Nor can you carve banked turns in a Viper fighter ala Battlestar Galactica circa 1978.

22 posted on 05/17/2005 6:51:31 AM PDT by Yo-Yo
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To: Yo-Yo
You can change which radial you are riding on by using gravity of passing planets to change your direction, but once you are outside their influence you will either be heading directly away from or directly towards the Sun.

I don't doubt that you are a competent sailor. It is true that there is not a one to one analogy between water sailing and solar sailing. But you need to brush up on orbital mechanics. Some parts are counter intuitive. It is simply untrue that a solar sailing craft is limited to only going directly away from or directly toward the Sun. A solar sailing craft can go anywhere in the solar system that it has sufficient time to travel to. Certainly, with current technology, that would be anywhere from Mars inward, and probably a lot more.

23 posted on 05/17/2005 8:06:58 PM PDT by marktwain
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To: Yo-Yo
You can change which radial you are riding on by using gravity of passing planets to change your direction, but once you are outside their influence you will either be heading directly away from or directly towards the Sun.

I don't doubt that you are a competent sailor. It is true that there is not a one to one analogy between water sailing and solar sailing. But you need to brush up on orbital mechanics. Some parts are counter intuitive. It is simply untrue that a solar sailing craft is limited to only going directly away from or directly toward the Sun. A solar sailing craft can go anywhere in the solar system that it has sufficient time to travel to. Certainly, with current technology, that would be anywhere from Mars inward, and probably a lot more.

24 posted on 05/17/2005 8:16:24 PM PDT by marktwain
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To: marktwain
It is simply untrue that a solar sailing craft is limited to only going directly away from or directly toward the Sun.

Did you read this part of my posting?:

You can change which radial you are riding on by using gravity of passing planets to change your direction, but once you are outside their influence you will either be heading directly away from or directly towards the Sun.

You can do the same maneuvers that current spacecraft use, where you do several loops around the sun to gain momentum. I don't dispute any of that.

Did you read this part of my posting?

I just disputed that you can tack upwind with a solar sail like you can in a sailboat.

To refresh your memory, this was the original question that I was responding to:

wonder if you can sail upwind like a sailboat ;)

To which you replied:

Short answer: Yes.

Which is blatantly untrue. You cannot "sail" upwind like a sailboat. There are other ways to get upwind, but you cannot sail upwind like a sailboat.

25 posted on 05/18/2005 9:12:42 AM PDT by Yo-Yo
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To: Yo-Yo
Which is blatantly untrue. You cannot "sail" upwind like a sailboat. There are other ways to get upwind, but you cannot sail upwind like a sailboat.

Perhaps we are disputing over semantics here. A sailboat can sail upwind. It uses the energy of the wind to move against the wind. A solar sail spaceship can sail upwind. That is, it uses the energy of the "wind" (sunlight coming from the sun) to move against the "wind" toward the sun. To me, that is clearly "sailing" upwind. This is not precisely the same as a sailboat tacking against the wind, but then, all of what we are talking about is an analogy.

The analogy that you used of a sailing vessel on a river is not correct, because while a craft on the river will move downstream without wind, a solar sailing craft will not fall toward the Sun without wind, because it does not depend on the "wind" to keep it in place. It must use the energy of the "wind" to move to an orbit either closer or further away from the Sun.

You can change which radial you are riding on by using gravity of passing planets to change your direction, but once you are outside their influence you will either be heading directly away from or directly towards the Sun.

This statement seems to be stating that aside from gravitational assists from "passing planets" a solar sail spaceship can only move directly toward or away from the Sun. In fact, perhaps the least likely motion of a solar sail spaceship is on a radial directly toward or away from the Sun. This is what led me to suggest that you needed to brush up on orbital mechanics.

One of the common errors of people who have not studied solar sails is to think that the craft can only go toward or away from the Sun. This is not the case, except in the general sense that all orbits, other than a perfectly circular one, go toward or away from the Sun. While you may not belong to the class of "people who have not studied solar sails", I only wished to correct that notion for the people who have not, and not to offend your sensibilities.

It is the lurkers who benefit most from these discussions, after all.

26 posted on 05/19/2005 4:59:02 AM PDT by marktwain
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To: spinestein

"Months or years after the rocket runs out of fuel, the sail is still pulling.]"

No way to reach another star with it, right?


27 posted on 08/17/2005 6:35:54 PM PDT by strategofr (What did happen to those 293 boxes of secret FBI files (esp on Senators) Hillary stole?)
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To: marktwain; Yo-Yo; Redleg Duke; ProudVet77
I have a background in physics and experience sailing and the following information is guaranteed 100% correct, and will also answer this thread's persistent question about "sailing upwind" in space.

A solar sail powered spacecraft can only travel directly away from the source of light if it has no other means of propulsion.

If this spacecraft then uses the gravity of a close planet to change its velocity (speed and/or direction) this has nothing to do with its method of propulsion by light pressure, but rather with its incidental path through space in the gravity field of that planet. These two things are not related in any way.

The analogy of a sailboat powered by atmospheric wind is a useless one with regard to solar sailing because a sailboat's direction of travel can be altered to include a vector component that is towards the wind when the keel is used as a lever against the physical medium of the water.

There is no physical medium for a spacecraft to fly through so this lever effect cannot take place.
28 posted on 08/18/2005 6:46:28 PM PDT by spinestein (The facts fairly and honestly presented, truth will take care of itself.)
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To: spinestein

Thanks, spinestein. You fishing old articles? That was from back in May!


29 posted on 08/19/2005 7:19:47 AM PDT by Yo-Yo
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