Astronomy – Sailing on a sunbeam

Up here on the Coast, we are used to seeing yachts skimming across the water, using just the power of the wind to propel them. Now imagine soaring through space in a yacht, using just the force of sunlight to move it.

Over the past few weeks, this dream has become a reality when a small spacecraft named LightSail 2 sailed into the history books, becoming the first spacecraft in Earth orbit propelled solely by sunlight.

Solar sailing works by using a shiny sail to reflect particles of light, called photons. The photons bounce off the sail and provide a tiny amount of momentum which push the craft forward like the wind blowing into a yacht’s sails.

Although the momentum generated is very small, because there is no air resistance in space, it can accelerate ships to potentially much higher speeds than traditional propulsion.

In this case, over two weeks, LightSail manged to raise its orbit by 3.2km using only the power of the sun.

LightSail 2’s orbit-raising phase will last about a month. Then the spacecraft will begin ‘de-orbiting’. In about a year, it will enter the atmosphere and will burn up.

LightSail 2 is a tiny craft (10cm x 10cm x 30cm) – just about the size of a loaf of bread. This houses the computer controls and radio equipment.

The spacecraft has four triangular sails made of Mylar, which combine to form a rectangular-shaped surface 32sqm in size (about the size of a boxing ring).

LightSail 2 is able to orient itself against the Sun using Earth’s magnetic field as a guide.

Much like the sailing we see on the coast, by “tacking” in and out of the Sun’s rays, it can control the force on its sail and then be able to change its orbit.

The LightSail project is run by The Planetary Society, which was founded in 1980 by the internationally renowned astronomer, Carl Sagan. It is a non-governmental, non-profit foundation, involved in research, public outreach, and political advocacy for engineering projects related to astronomy, planetary science, and space exploration.

LightSail 2 was funded using crowd sourcing and cost US$7 million over 10 years and was paid for by approximately 40,000 individual donors, including $1.24 million raised from a successful Kickstarter campaign. The launch costs were covered by the US Air Force Research Laboratory’s University Nanosat Program.

So what does this mean for our future? We could use solar sailing to visit the inner planets – Mars, Venus, and Mercury. We could also use it as a kind of shuttle, sending supplies to either a lunar or Mars base. Already, the European Space Agency has proposed using solar sailing to visit Mercury, which is extremely difficult to reach using rockets due to its proximity to the sun.

The Breakthrough Starshot project announced in April 2016, aims to develop a fleet of 1000 light sail nanocraft carrying miniature cameras, propelled by ground-based lasers and send them to Alpha Centauri at 20 percent the speed of light. The trip would take 20 years.

Perhaps one day, we will be able to take a cruise on a solar sail spaceship to visit one of the inner planets, or maybe we could hold space regattas, or even the space equivalent of the America’s Cup. One thing is certain, it is going to be an exciting journey getting there.