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New LightSail 2 spacecraft will boost solar-sail interplanetary missions

LightSail 2, set to launch no earlier than June 13, 2018, will be visible to observers on the ground as the orbits of the Earth for a month or more.

(Credit: The Planetary Society)

A new solar-sailing spacecraft will appeal to all the (future) occupants of the interplanetary craft. The Planetary Society’s LightSail 2 spacecraft will be a test bed for future missions that wish to make use of solar-sailing, including NASA’s proposed cubesat, the Near-Earth Asteroid Scout (NEA Scout).

LightSail 2 will launch no earlier than June 13 from the Kennedy Space Center near Orlando, Florida, with the help of SpaceX’s new and powerful Falcon Heavy rocket. The spacecraft’s ultimate destination will be in the middle-Earth in an orbit of about 725 kilometres (450 miles) — roughly double the height of the International Space Station.

The mission’s ultimate goal is to test out “flight by light”, such as The Planetary Society calls solar sailing in space. This type of drive makes use of the gentle pressure of photons streaming from the sun to move the spacecraft around. The biggest advantage is that the spacecraft does not need to carry fuel. On a small satellite, like a cubesat, said Bruce Betts, chief scientist of The Planetary Society, every gram of weight counts. [The Evolution of Solar Sails in Photos]

“We have waited for a launch where we could get to a greater height, it [the Earth], where solar pressure will dominate over the atmospheric drag,” said Betts Space.com.

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“We will try to do controlled solar sailing … every half [Earth] orbit, we are being pushed by the sunlight, and for the other half of the job, we will be edge-on to the sunlight,” said Beets, who is also The Planetary Society, director of science and technology.

Improvements of LightSail 1

The Planetary Society’s LightSail 1 was launched on 20 May 2015, together with the Air Force’s supersecret X-37B space plane. It survived only less than a month in a low orbit around the Earth. While its important mission objective of the deployment of the sail, the test flight had several problems along the way.

Just two days after the launch, a software glitch delayed the plans for deploying the solar sail to 7 June. The spacecraft sent an image 9 June, showing that the sail is unfurled with success, by achieving its primary mission objective. But then, more problems arise.

“Before engineers could get a photo of the other side cameras, LightSail’s radio began transmitting a continuous, nonsensical signal, and the spacecraft is not responding to commands,” said the Planetary Society’s Jason Davis in a blog post on June 15, 2015. The spacecraft also stopped broadcasting on 10 June, shortly before it entered into the atmosphere, as originally planned.

“We learned a lot of LightSail 1,” Betts said. “It has taught us a lot about the spaceship, and after the various issues, we have a large number of improvements.”

Some of the most important improvements will help LightSail 2 make more efficient use of the particles coming his way. The most dramatic hardware difference is a momentum wheel, or a fast-rotating wheel that helps LightSail 2 maintain position in the space. The attitude determination and control software is different from LightSail 1 of the equipment. The cameras were also upgraded to transmit higher-quality images of the sails.

Other improvements are intended to make the spacecraft more robust. Instead of “waiting to re-start somewhere, magically happen,” Betts said, there are timers on board with automatic settings to restart processes, or, in the worst case, a reboot of the entire spacecraft in case of problems. More information will be included in the radio signal to provide controllers with information about the spacecraft’s health status. Engineers also have reflectors to the position of LightSail 2 easier to track from the ground.

The interplanetary craft

A few other spacecraft have been tested, from solar sails in space. The most striking example is the Japanese Ikaros (Interplanetary Kite-craft Accelerated by Radiation Of the Sun), which passed with the help of a solar sail in 2010, during the Japan’s Akatsuki mission to Venus. It is the only spacecraft that used this method to go as far in the deep space — in 2012, Ikaros receiving the Guinness World Record as the first solar sail spacecraft between the planets. [Solar Sails the Future of Space travel?]

NASA also deployed a solar sail, the NanoSail-D2 in a low Earth orbit in 2010; that the mission is more focused on the sail of the implementation, and how the sail behaved in a low orbit around the Earth. (The agency planned a solar-sail mission dubbed Sunjammer, but it was cancelled for the launch.)

This means LightSail 2 the add of vital importance, in the real world of information about how solar sails behave in the space. The team is in contact with another solar sail experimental team: the NEA Scout team, which will use a solar sail to fly by an asteroid. “They are planning on using a solar sail with a similar type of design and features to LightSail 2,” Betts said.

NEA Scout is scheduled to be at a dozen other small missions on board of the Orion’s exploration mission-1, which will also be the first test flight of NASA’s Space Launch System, and is currently scheduled for no earlier than 2019. NEA Scout is expected to fly past an asteroid called 1991 VG, although the decision to fly through the asteroid hasn’t been finalized yet.

Solar-sailing is a possible propulsion method for the distant future interstellar missions because fuel does not need to be transported. NASA has played around with various mission-concept ideas. The privately-funded Breakthrough Starshot initiative plans for the use of a laser in combination with a sailto sending a small probe to the Earth the nearest star, Alpha Centauri.

Original article on Space.com.

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