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View Full Version : Discussion: Solar Sail Launch Delayed to 2004



Fraser
2003-Oct-17, 04:22 PM
SUMMARY: The Planetary Society announced this week that they will be pushing back the launch of the Cosmos 1 solar sail from October to some time in 2004. This will give the mission team more time to test various aspects of the spacecraft to make that it works properly when it does launch. Their previous launch of a solar sail failed when the Volna rocket carrying it failed to deploy the spacecraft. If successful, this prototype vehicle will help demonstrate that the light from the Sun can be used for propulsion.


Comments or questions about this story? Feel free to share your thoughts.

imported_James
2003-Oct-18, 10:59 PM
I have yet to get a satisfactory answer as to how a solar sail works. There is a fact that suggests solar sails will not work. The solar sail is said to rely upon a transfer of momentum from photons. I have a problem with this since photons are massless. That means photons have no momentum to transfer. I believe that if the solar sail exhibits any acceleration, it will be from the particles in the solar wind, not photons.

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Haglund
2003-Oct-19, 09:43 AM
Here's a website about solar sails, the first one the main site, the other an explanation on how they work.
http://www.ugcs.caltech.edu/~diedrich/solarsails/
http://www.ugcs.caltech.edu/~diedrich/sola...ntro/intro.html (http://www.ugcs.caltech.edu/~diedrich/solarsails/intro/intro.html)

zephyr46
2003-Oct-20, 12:15 AM
There was a story recently about how the solar wind was gently blowing satelites out of aliginment, buildling satelites to capitalise on the effect (http://www.spacedaily.com/news/ngst-02a.html), and another story about asteroids being effected by the solar wind (http://www.spacedaily.com/news/asteroid-03m.html). Why focus on photons when there are observable effects of a plasma stream that, today was blowing 573 kmps (http://sohowww.nascom.nasa.gov/)?

Fraser
2003-Oct-20, 01:10 AM
Solar sails have been effectively tested in the laboratory - a place where there is no solar wind.

Here's NASA's Solar Sail site with lots of details about their research:
http://solarsails.jpl.nasa.gov/

Photons don't have mass, but they do have momentum, which they can transfer to the things they collide with.

zephyr46
2003-Oct-21, 04:05 AM
Whatever, the sooner we get somthing up there cruising the better. :)

imported_James
2003-Oct-21, 05:42 AM
Originally posted by fraser@Oct 20 2003, 01:10 AM
Photons don't have mass, but they do have momentum, which they can transfer to the things they collide with.
I have a problem with massless momentum.

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IonDrive
2003-Oct-28, 11:38 PM
Originally posted by James+Oct 21 2003, 05:42 AM--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (James @ Oct 21 2003, 05:42 AM)</td></tr><tr><td id='QUOTE'> <!--QuoteBegin-fraser@Oct 20 2003, 01:10 AM
Photons don&#39;t have mass, but they do have momentum, which they can transfer to the things they collide with.
I have a problem with massless momentum.

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Photons are actually calculated to have no mass when they are NOT moving. but since they are moving at light speed they can have "mass" then.
That&#39;s why particles with "no mass when not moving" (sorry, again I don&#39;t know the appropriate term in "Atomphysician") HAVE to move at light speed, by the way.
You might have heard that when objects move at a velocity which is a substiantial fraction of light speed in relation to a spectator, they gain mass in the eyes of that spectator, which kind of derives from their kinetic energy.
So since photons move at exactly light speed :D , their "mass" is identical with their energy, and that&#39;s where they get their momentum from.

Yes that means that UV and X ray photons "weigh" more than those from visible light, that&#39;s why they can do serious damage to living tissue. Like an anvil falling on your head would do more damage than an apple; and if you don&#39;t believe that ask Newton and Tom from "Tom and Jerry"&#33; :lol:

imported_James
2003-Nov-16, 07:07 AM
IonDrive:
Eloquently put, but I still do not buy into the massless momentum. Until there is some conversion of energy into mass, photons have none of the properties of mass.

Since photons can not exist at what you consider "at rest", you must consider the photon "at rest" in its natural condition.

I think that this misunderstanding is the result of not knowing what a photon is. I have heard it described as a quantum of energy, ElectroMagnetic Force, ElectroMagnetic Energy, ElectroMagnetic waves, light, light waves, radio waves, gamma rays, etc. While descriptive, these descriptions do not really tell what a photon is.

Another point to consider is that even the highest powered laser has no recoil. That means if the light sail works, you could power the laser with an onboard reactor to generate thrust by aiming it at the light sail.

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Matthew
2003-Nov-16, 08:22 AM
Check out Solar Sails. (http://www.universetoday.com/forum/index.php?showtopic=985&st=0)

imported_James
2003-Nov-17, 02:42 PM
Been there, done that. I made similar comments there. Despite all that, I am really getting impatient about the deployment of the solar sail as that would be the definitive test of the theory that a photon has the properties of mass. Until I am proven wrong, I will hold to the theory that a photon has none of the properties of mass. Mass can not go the "speed of light" and a photon can not go any slower. This demonstrates the lack of common properties.

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