January 2017 Astronautics

New oceans beckon for solar sail technology

NanoSail-D2 was a small satellite which was used by NASA to study the deployment of a solar sail in space. It was a three-unit CubeSat measuring 30 x 10 x 10 cm.
NanoSail-D2 was a small satellite which was used by NASA to study the deployment of a solar sail in space. It was a three-unit CubeSat measuring 30 x 10 x 10 cm.
Les Johnson George C. Marshall Space Flight Center in Huntsville, Alabama, USA

Solar sailing is finally becoming a reality. After many false starts, launch vehicle failures and funding cuts, NASA, The Planetary Society, ESA and JAXA have all flown solar sails in space and are planning ambitious new missions for the future. The promise of propellant-less propulsion offered by solar energy is becoming a reality.

As their name implies, solar sails ‘sail’ by reflecting sunlight from a large, lightweight reflective material that resembles the sails of 17th and 18th century ships and modern sloops. Instead of wind, the sail and the ship derive their thrust by reflecting solar photons. It is a common misperception that solar sails use the solar wind for propulsion. This is incorrect. The solar wind is composed of atoms, typically hydrogen and helium, and their interaction with the solar sail produces no significant thrust. Photons have no rest mass but, thanks to quantum mechanics, they do have momentum. And, like any particle with momentum, they can impart some of it to an object that either absorbs or reflects them. Reflecting photons is preferable because it imparts approximately twice the momentum as absorption.

The physics of solar sail propulsion is relatively easy to understand. Newton’s Second Law of Motion says that Force is equal to mass times acceleration. The force (F) of sunlight at a given distance from the Sun can therefore cause a spacecraft of mass (M) to accelerate with acceleration A, F = MxA, an equation familiar to introductory physics students everywhere.

Read more about solar sails and their impact on the future of fueled spacecraft in the full version of the article, available now to our subscribers.

To continue reading this premium article, subscribe now for unlimited access to all online content

If you already have a login and password to access www.room.eu.com - Please log in to be able to read all the articles of the site.

Popular articles

See also

Space Environment

Life in the extremes: confessions of an astrobiologist

Astronautics

A boom and a (possible) bust in small spacecraft production

Space Security

The peaceful use of space

Popular articles

Space Security

Humanity is moving towards a new reality

Multi-dome lunar base being constructed, based on the 3D printing concept. Once assembled, the inflated domes are covered with a layer of 3D-printed lunar regolith by robots to help protect the occupants against space radiation and micrometeoroids. Space Environment

Surviving radiation for space colonisation

Special Reports

Urgent action needed to keep satellites safe in orbit