Light sailing is a proposed method of spacecraft propulsion using radiation pressure from starlight to power sail-equipped craft. The first light sail demonstration mission, IKAROS, launched in 2010 and successfully used sunlight to propel the craft. The upcoming LightSail 2 mission in 2019, led by The Planetary Society, aims to raise the orbit of its small craft using solely sunlight. The most ambitious light sailing proposal is Breakthrough Starshot's goal of using ground-based lasers to accelerate tiny nanocraft to 1/4 the speed of light to reach Alpha Centauri within decades. Light sailing could enable less expensive and more far-reaching space exploration if these pioneering attempts are successful.

1. Light sailing: the future of interstellar travel or science
fiction?

2. What is light sailing?
Light sailing is a way of space travel. The idea is to equip
a spacecraft with a giant sail made of highly reflective
material such as aluminium. When massless light particles
(photons) from the Sun or another star bump into the sail,
some of the photons will bounce off the surface and their
momentum will be transferred to the craft. In the absence
of the atmosphere this tiny “push” will be enough for
moving, maneuvering and accelerating a spacecraft to a
great speed over a long distance.
Keep in mind that a light sail spacecraft is propelled NOT
by solar wind, like wind sail, but exclusively by the
radiation pressure.
The advantages of this technology are huge! No need to
produce or carry fuel for the maneuvers and unlimited
propellant supplies mean that space exploration can be
less expensive and we can finally go places that up until
now were well out of our reach.

3. IKAROS: light sailing debut in 2010
Japanese Space Agency JAXA was the first organization
to show that light sailing technology can work. Back in
2010 they successfully launched the first light sail
spacecraft called ”Interplanetary Kite-craft Accelerated by
Radiation Of the Sun”, or IKAROS for short.
The spacecraft was propelled by the sunlight and solar
energy stored in its tiny solar cells provided power for the
payload. The mission was designed to last 6 months, but
IKAROS worked way longer. The kite-craft made its last
contact with the Earth in May 2015.

4. LightSail 2: the upcoming 2019 launch
Not only government space agencies are interested in the light
sailing. Private companies have their eyes on the technology too.
The Planetary Society, an American non-government organization,
is about to test their most recent crowdfunding project LightSail 2.
If all goes as planned, then tomorrow, on June 24 2019, LightSail
2 spacecraft will be launched into orbit around the Earth aboard
SpaceX Falcon Heavy rocket. LightSail 2 is a tiny probe about the
size of a loaf of bread. Its sail, when fully deployed, is 32 square
meters large.
The objective of the upcoming mission is to try and raise the orbit
(i.e. distance from the Earth) of the spacecraft using only the push
on the sunlight. At the end of its 60 day journey LightSail2 will
plunge into the Earth’s atmosphere.
Watch the LightSail2 animation to learn more about the spacecraft
and its mission.
The spacecraft’s predecessor, LightSail 1, had lots of problems
during its short one month operation in 2015. Still, the Society’
pilot mission achieved its primary goal, sail deployment, and
pointed out what needed to be improved.

5. Breakthrough Starshot: aiming for the stars
When it comes to light sailing, Breakthrough
Initiatives have the most ambitious plans of all. Their
starshot project is an idea-in-development to send a fleet
of centimeter size spacecrafts to Alpha Centauri, the
closest star system to the Sun. The nano-crafts will be
accelerated to the ¼ of the speed of light by a laser beam
on Earth. At that speed they will reach their destination in
“just” 30 years.
By the way, the Starshot idea was featured in the
children’s fiction book “The Jamie Drake equation” by
Christopher Edge. You will find more information about the
book and the real science facts in it in our blog post “The
Jamie Drake Equation” book.
Will these pioneering attempts to sail through space
eventually lead to human interstellar travel? We cannot
wait to find out!

6. For more information
•Book our inflatable star dome to experience interstellar
travel without even leaving the Earth!
•Send you questions, comments and ideas to our portable
planetarium team. We would love to hear from you!