SpaceX doesn’t mark the spot for NASA’s NanoSail-D spacecraft

William Atkins
Wednesday, 13 August 2008 22:32

Science - Space

A solar sail spacecraft, also called a light sail spacecraft, uses light sources, such as from the Sun, as its means of propulsion.

Such craft use large membrane mirrors to capture light. For our solar-powered  experiments here on Earth, the radiation pressure from the Sun at the Earth, a distance of around 93 million miles (150 million kilometers), is about 10^-5 pascals.

A pascal is a unit of pressure (P). It is a measure of the perpendicular force (F) applied over a unit area (A); or P = F/A. One pascal is equal to one newton per square meter or one joule per cubic meter.

As light (for example, sunlight) goes further out into space, its radiation pressure decreases by the square of the distance from the light source (such as the Sun).

Thus, particles of light coming off of the Sun push against the solar sails on such spacecraft--which provides the "thrust" it needs to travel in space.

Although such pressure is very small compared with the thrust generated by a traditional rocket engine, a solar sail does not require a reaction mass (a mass against which thrust is applied) and it continues to generate power as long as light impinges on the extended solar sails.

For information on the history of solar sails, please go to the NASA website “A Brief History of Solar Sails.”

For additional information on voyages to planets in our solar system using solar-powered vehicles, please go to the "Solar Sail " website of China's Tsinghua Space Center. It states that a trip from the Earth to Mars would take over five years with the use of a solar sail, while a trip to Venus would take about three years.