NASA to Launch World's Largest Solar Sail in 2014

**Sparking Neuron** · 02 Feb 13,, 14:41

This is going to be great. NASA will launch a solar sail powered space craft next year. Solar sail takes virtually no fuel. It drives a body by the kinetic energy of photons that hit it from a major light source(say sun), simply put, light takes place of wind. This system doesn't give a kick as powerful as other fueled engines but over a long distance it will always win the race. Because it doesn't run on fuel, it never runs out of fuel and keeps accelerating to speeds that conventional engines can never reach.
Theoretically, this would give us access outer space in a more reliable way. Imagine Columbus on a rowing boat

The largest solar sail ever constructed is headed for the launch pad in 2014 on a mission to demonstrate the value of "propellantless propulsion"— the act of using photons from the sun to push a craft through space.

Dubbed Sunjammer, the giant solar sail measures about 124 feet (38 meters) on a side and boasts a total surface area of nearly 13,000 square feet (1,208 square m, or one-third of an acre). The project is under the wing of NASA's Space Technology Program, within the agency's Office of the Chief Technologist.

NASA has contracted with a team of high-tech "solar sailors" at L'Garde Inc. of Tustin, Calif., to build Sunjammer.

NASA to Launch World's Largest Solar Sail in 2014 | Space.com

**Doktor** · 02 Feb 13,, 14:45

I thought they got cut off in funds.

**Chogy** · 02 Feb 13,, 16:26

The solar sail is a fascinating concept. Indeed, the acceleration is very light, but continuous, and over time, it'll really get you moving. Unfortunately, you lose thrust as you fall away from the sun and the light intensity decreases. This is one reason (low light flux) that any probe much past Mars needs a nuclear battery rather than solar cells.

The current problem with solar sails is materials and mass. The size of a "real" sail, rather than this proof of concept, would have to be spectacularly large. Still, if they are going to give this a shot, I am happy to see it.

**citanon** · 02 Feb 13,, 20:13

This is the great. I'm of the opinion that in 50 or 100 years we'll be flying raw materials (asteroids) into the inner solar system from the asteroid belt (going downhill in the gravity well), processing them using automated plants (some built right into the asteroid as it makes its journey inward) powered by abundant solar energy, and then using the solar winds to carry refined products, processed materials and manufactured goods back out to earth and the outer areas of the solar system for use.

**Monash** · 04 Feb 13,, 02:42

Great project but I must admit I've never quite "got" the idea behind light sails where the impact of photons imparts an acceleration force the target. I know it works I just can't figure out how it works. Since I have always read that photons are mass-less particles and that momentum is a product of the mass and velocity of a given object I don't quite see how a photon striking a sail imparts momentum, energy sure but not momentum. Take the classic science fiction idea of the laser propelled solar sail. I can see how the laser would impart energy and heat up the sail but not how it imparts acceleration. Other particles no problem, hit a physical or magnetic sail with any "massive" particle and you impart momentum. The only thing I can think of is that that I am misinterpreting the concept of mass and that photons do in fact possess it. Anyone with working knowledge of physics care to assist a layman?

**citanon** · 08 Feb 13,, 23:44

Originally Posted by Monash

Great project but I must admit I've never quite "got" the idea behind light sails where the impact of photons imparts an acceleration force the target. I know it works I just can't figure out how it works. Since I have always read that photons are mass-less particles and that momentum is a product of the mass and velocity of a given object I don't quite see how a photon striking a sail imparts momentum, energy sure but not momentum. Take the classic science fiction idea of the laser propelled solar sail. I can see how the laser would impart energy and heat up the sail but not how it imparts acceleration. Other particles no problem, hit a physical or magnetic sail with any "massive" particle and you impart momentum. The only thing I can think of is that that I am misinterpreting the concept of mass and that photons do in fact possess it. Anyone with working knowledge of physics care to assist a layman?

Maybe this will help:

Relativistic Momentum

Or not.