Physics: Principles and Problems


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For use with Chapter 6
Forces

Sailing to the Stars
Posted April 11th, 2001

Hundreds of years ago, Johannes Kepler made the suggestion that ships could sail through space using "heavenly breezes" much like ships do that sail across the sea using the wind. Because there's a vacuum in space, there are of course no breezes in space. However, there are winds - solar winds. Solar winds are photons and particles that radiate out from the Sun. Scientists at NASA's Jet Propulsion Laboratories (JPL) are developing a way to harness these winds with huge solar sails.

These sails need to be incredibly thin and lightweight to be easily transported into space. The sails would be sent into space in a small container and then deployed when their location has been reached. The sails would then be propelled by photons and microwaves. When the sails are deployed near Earth, which is relatively close to the Sun, the powerful radiation from the Sun will push the ship deep into space.

Once the ship traveled beyond the influence of the solar winds, it could continue "coasting" at an incredibly high speed beyond the solar system. Scientists calculate a ship propelled by these sails could reach the nearest star in approximately 40 years.

New Materials Developed
Special materials have been developed to make the sails. It uses a special carbon composite that was developed by Energy Science Laboratory in San Diego, California. The compound is strong enough to resist the intense heat of the radiation in space (up to 2,500 Kelvin) and being pelted by micrometeors, yet thin enough to meet the lightweight requirements to send it into space.

The material was tested at JPL and at Wright-Patterson Air Force Base in Dayton, Ohio. They were able to produce an acceleration that was several times as powerful as the force of gravity.

These sails could achieve speeds much faster than can be achieved through traditional spaceflight. It would also be a source of "fuel" - which is directed from outside of the ship - and allow the ship to travel farther than is possible now.

The Planetary Society, which was founded by scientist Carl Sagan among others, plans to send a test probe into space that will use this technology. Their craft will have 30-yard sails and will cost about $4 million. If the test flight is successful, perhaps in a few short decades, it might be possible to travel beyond the solar system.

Activity
Use the Internet sites given here to research these space sails. In a small group, build a model of these spacecraft and explain it to the class.

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Physics: Principles and Problems