Solar Sails?

My dad brought up solar sails up at dinner tonight, he siad the sails would trap sunlight and propel a ship at the speed of light. Is this even possible. Anyone out there knowagable on the topic

Originally posted by TKainZero
My dad brought up solar sails up at dinner tonight, he siad the sails would trap sunlight and propel a ship at the speed of light. Is this even possible. Anyone out there knowagable on the topic

Yeah they are possible, they will be testing one very soon actually as a proof of concept. By the way the sails do not "catch" the solar wind, but when the photons and other particles hit the sail a small amount of momentum is transfered, and thrust is created. It's wierd how massless particles can create thrust isn't it. Here is a link you should check up on, and there is always google.

www.ugcs.caltech.edu...

www.planetary.org...

Yes it�s a popular idea for future space travel because the ship wouldn�t need to carry all of its propellant on board the ship. NASA has been working on it for some time now.

www.nasa.gov...

But light soes have mass, everything has mass no matter how small it is.

You said a solar sail will be tested soon, what typw will it be, when will this happen, is the solar sail they are testing one of the types on the site?

Originally posted by TKainZero
But light soes have mass, everything has mass no matter how small it is.

Not true. The only reason photons can travel at the speed of light is because they are massless.

en.wikipedia.org...
All electromagnetic radiation, from radio waves to gamma rays, is quantised as photons: that is, the smallest amount of electromagnetic radiation that can exist is one photon whatever its wavelength, frequency, energy, or momentum. Photons are fundamental particles. Their lifetime is infinite, although they can be created and destroyed. Photons are commonly associated with visible light, which is actually only a very limited part of the electromagnetic spectrum. Photons have zero invariant mass but a definite finite energy. Because they have energy, the theory of general relativity states that they are affected by gravity, and this is confirmed by observation.

Please click on the link for a much more detailed analisys. Here are a couple more links on some fundamental particles.

en.wikipedia.org...
en.wikipedia.org...
en.wikipedia.org...

Also here is the link on the solar sail test happening soon.
www.space.com...

Wow, i guess it has no mass, but it it has no mass how can light be bent, or how can i be used in the soiar sail.

Originally posted by TKainZero
Wow, i guess it has no mass, but it it has no mass how can light be bent, or how can i be used in the soiar sail.

Read the link it will go more indepth then I could. The reason it can be bent is because it has finite energy. This energy can be tinkered with by many different means. And remember gravity is nothing more the space being bent by mass. So even if it was going straight if space is bent then the course of the photon would be bent as well because the topography of space has changed. Think of it like a sea and no matter how hard you try you can't go from point A to point B in a completely straight line, due to waves and dips in the water. The same is true of space. Weird ain't it.

There was a few years back now a UK scientist, if I remember his name I should be able to repost with a link as I don't know the terminology to search for it, who was investigating the big bang theory and the universe moving outward etc etc. He theorised that if there was a continuous movement in a direction then this motion should be able to be "caught" and used as a propellent. Bit like space wind I spose for a simple term.

May be something researchers are still looking at in conjunction with solar sails. The travel would not necessarily be fast, but more for the use of long distance probes etc.

Could be my memory playing tricks on me, but I am sure this is true, apologies if I am just remembering an old episode of something on Sci-Fi

one question that occured to me is, solar power would be ok to get us moving out into space, but how far could it take us? How far can we go before our sun just becomes another star in space? If a craft were moving and then had to stop , where would we get our light source from, with the next star being lightyears away? I assume that some power could be stored to provide momentum again, but wouldn't there be a risk of being stranded between solar systems? ok for probes , but not for manned craft maybe. Or is starlight strong enough to be used?

Thats east. Gigawatt Lasers should do the trick.

Light has mass. If it didn't, then why can't it escape the gravity of Black Holes? After all, gravity is the force that attracts all objects in relation to their masses.

Originally posted by TJ11240
Light has mass. If it didn't, then why can't it escape the gravity of Black Holes? After all, gravity is the force that attracts all objects in relation to their masses.

No it isn't. Gravity is a deformation in the fabric of spacetime cause by mass and momentum I believe. You should really click the links I posted. Light DOES NOT HAVE MASS, IT JUST HAS ENERGY AND MOMENTUM.

the solar sail will have very slow excelleration...

Let me kick in my two cents� as well:

TkainZero says:

�Solar Sails? My dad brought up solar sails up at dinner tonight, he siad the sails would trap sunlight and propel a ship at the speed of light. Is this even possible. Anyone out there knowagable on the topic �

The idea for solar sails has been around for at least a half-century; we know that the basic theory is and have validated it; we know how involved engineering aspects of a solar sail-propelled craft would be. It�s tough, but nothing tougher than what we have already done.

The sail would possibly be made of something like aluminized Mylar, only about ten times as strong and weighing one tenth as much. It might be a disc a couple kilometers in diameter -- we are talking big sail here.

Light (photons) don�t impart very much mass-moving energy on something like a sail, but there are lot of photons, a large area to collect them, and the fact that, although you build up speed slowly, there might be a constant acceleration of 0.1G. That doesn�t sound like much, but it means that your speed is getting faster -- faster. As long as you stay within, say, the orbit of Jupiter, you will be able to build up a lot of speed, which won�t go away by itself.

That�s why, if you were a solar sailor, you�d calculate the best ways to use planets� gravity to pick up speed, shed some of it, �bank" around the planet to move you from one spot to another. Our unmanned outer solar system probes do that regularly now.

pantha says:

�one question that occured to me is, solar power would be ok to get us moving out into space, but how far could it take us? How far can we go before our sun just becomes another star in space? If a craft were moving and then had to stop , where would we get our light source from, with the next star being lightyears away? I assume that some power could be stored to provide momentum again, but wouldn't there be a risk of being stranded between solar systems? ok for probes , but not for manned craft maybe. Or is starlight strong enough to be used?�

Pantha, the further you go from the sun, the fewer protons there are. As a matter of fact, the fall-off in photons and solar wind increases as the square of the distance from the sun. Once you get out beyond, say, the orbit of Jupiter or Saturn, you won�t have much sun-energy to collect and use.

But it doesn�t matter, because it�s not like you need a steady stream of photons. Remember, in space, there�s not much resistance against a spaceship�s flight, so once they start going, they will stay at that same direction and same speed (what�s called the �axis-velocity vector�) until something happens to change it, like they crash into a planet, or swing around it in orbit.

What this means is that the spacecraft, if it�s designed right and uses the right math, could get into a high (if you consider 0.1 G acceleration as �high�) velocity, maybe use Jupiter and Saturn as an opportunity to pick up some velocity thanks to old Mr. Gravity, would have you exiting the Solar System at a speed close to 0.3c, or thirty percent of light speed. This means you could get to the star Proxima Centauri in about 12 years (although the time would be shorter for you because of Einstein�s Special Theory).

So you won�t get much additional energy when you�re outside the Solar System, and starlight isn�t worth very much. But remember you�re already going at a third the speed of light, and there isn�t anything to slow you down!

if the sail collected light, then wouldnt it collect light from all soures, including other stars, if that happen how could it move at all.

"if the sail collected light, then wouldnt it collect light from all soures, including other stars, if that happen how could it move at all."

Because the amount of sunlight from the sun is greater than light from the stars --- or even reflected light from a nearby planet -- by a very high factor.

Nifty solar sail simulator java thingy on the net link below:

www.ec-lille.fr...

[edit on 21-12-2004 by UofCinLA]

Originally posted by Off_The_Street
"if the sail collected light, then wouldnt it collect light from all soures, including other stars, if that happen how could it move at all."

Because the amount of sunlight from the sun is greater than light from the stars --- or even reflected light from a nearby planet -- by a very high factor.

But what would happen when we got closer to other stars than to our own is what i wanted to know?

TKainZero, you ever hear of a method that NASA uses to slow down its spacecraft call Aerocapture? I'm sure a similiar method could be worked out with Solar Sails. BTW Once you get far enough out from our sun we need to use lasers to keep to acceleration going.