New Delhi: The Planetary Society has announced that its experimental LightSail 2 spacecraft successfully raised its orbit around Earth powered only by sunlight.
Like a sailboat propelled by winds, the LightSail 2 spacecraft – which is roughly the size of a loaf of bread and completely crowdfunded – uses a sail that is propelled by photons streaming out from the Sun. With this accomplishment, the spacecraft has become the “highest-performing solar sail to date.”
We just raised our orbit around Earth using sunlight alone, something that’s never been done before.#LightSail2 is now the highest performing solar sail to date and it’s 100% crowdfunded by our members and backers! pic.twitter.com/9bLxTNgbJs
— Planetary Society (@exploreplanets) July 31, 2019
Jason Davis, digital editor for the Planetary Society, wrote in a blog post that in the last four days, LightSail 2 had raised its orbital high point, known as the apogee in technical parlance, by about 2 km. This change, the organisation said, “can only be attributed to solar sailing”.
He added that the low point of its orbit had dropped by a similar amount, “consistent with pre-flight expectations for the effects of atmospheric drag on the spacecraft”.
Bruce Betts, the LightSail programme manager and chief scientist of the Planetary Society, was quoted in the same post as saying: “Our criteria was to demonstrate controlled solar sailing in a CubeSat by changing the spacecraft’s orbit using only the light pressure of the Sun, something that’s never been done before.”
CubeSats are a type of standardised spacecraft usually not much bigger than a cereal box, The Verge wrote.
According to New York Times, the technology could be instrumental in pushing future space probes through the solar system. At present, a majority of space missions are powered by an engine that consumes fuel to provide acceleration in bursts. When the spacecraft isn’t accelerating, it is coasting. How the LightSail 2 differs is that photons from the Sun “bounce against the spacecraft’s 344-square-feet of sails.”
Photons don’t have mass but they do have momentum, corresponding to the energy they carry. This generates a small amount of force, roughly the same as “the weight of a paper clip pushing down on your hand,” the NYT wrote.
Because the Sun shines constantly, the LightSail’s sails are pushed forward continuously and the spacecraft gradually builds up its speed.
The Planetary Society, a non-profit organisation, has been working on the LightSail programme for a decade. The project kicked off in the 1990s, but its first planned prototype, Cosmos 1, was destroyed during a faulty launch on a Russian rocket taking off from a submarine in 2005. The Planetary Society got its the next prototype, LightSail 1, into space in 2015, but technical problems kept it from climbing high enough to be steered by sunlight.
The LightSail 2 spacecraft was launched on June 25 and has since been in a low-Earth orbit, according to The Verge.
Last week, it deployed four triangular sails – a thin, square swath of mylar about the size of a boxing ring. After launch, engineers on the ground have been remotely adjusting the orientation of the sails to optimise the LightSail 2’s ability to harness solar photons.
Solar sailing isn’t new but the Planetary Society wanted to show that the technique could be used for smaller satellites, which are harder to manoeuvre through space. A majority of the satellites, as senior science reporter Loren Grush explained on The Verge, have to rely on thrusters to be mobile. These are “tiny engines that combust chemical propellants to push a vehicle through space.” However, this increases the cost of satellites as well as their launch mass.
Smaller satellites like CubeSats cannot accommodate thrusters most of the time, nor can they be closely manoeuvred once they are in space. But with this mission, the Planetary Society has demonstrated that solar sails can guide CubeSats through space. It is set to share the data it receives from this mission to allow other groups to build on this technology.
The solar sail technology could reduce the need for expensive, cumbersome rocket propellants and slash the cost of navigating small satellites in space.
“We strongly feel that missions like Lightsail 2 will democratise space, enable more people, more organisations around the world to send spacecraft to exciting and remarkable destinations in the solar system that will lead us to answer that deep question: ‘Where did we all come from?'” Reuters quoted Nye as saying.
(With inputs from Reuters)