LightSail 2

LightSail 2 is a project to demonstrate controlled solar sailing using a CubeSat developed by The Planetary Society, a global non-profit organization devoted to space exploration.^[3] The spacecraft core measures 10 by 10 by 30 centimeters, and its kite-shaped solar sail deploys into a total area of 32 square meters (340 sq ft).^[4]

LightSail2 is currently scheduled to be launched as part of a US Air Force Space Test Program package (STP-2) on a Falcon Heavy rocket in early 2018.^[2]

On May 20, 2015, a nearly identical demonstration spacecraft, LightSail 1 (formerly called LightSail-A^[1]), was launched, and deployed its solar sail on June 7, 2015.

History

NASA's NanoSail-D with sail deployed.

In 2005, The Planetary Society attempted to send a larger solar sail named Cosmos 1 into space, but the spacecraft's Russian Volna launch vehicle failed to reach orbit.^[5] In 2009, the Society began working on a CubeSat-based solar sail based on NASA's NanoSail-D project,^[6] which was lost in August 2008 due to the failure of its Falcon 1 launch vehicle.^[7] (A second unit, NanoSail-D2, was successfully deployed in early 2011.)

By 2011, the LightSail project had passed its critical design review, which was conducted by a team including JPL project veterans Bud Schurmeier, Glenn Cunningham, and Viktor Kerzhanovich, as well as Dave Bearden of Aerospace Corporation.^[8] The original estimated cost of the LightSail project was US$1.8 million, which was raised from membership dues and private sources. The prototype spacecraft LightSail 1 (or LightSail-A) was built in San Luis Obispo by Stellar Exploration Inc.^[5]

In March 2016, The Planetary Society announced they decided to use the convention on naming the spacecraft with the program name followed by a sequential number; the test flight or LightSail-A, became LightSail 1, and the upcoming larger spacecraft is now called LightSail 2.^[1]

Design

As a solar sail, LightSail 2's propulsion is dependent on solar radiation alone. Solar photons exert radiation pressure on the sail, producing a small degree of acceleration. Thus, the solar sail will be propelled by pressure from sunlight itself, and not by the charged particles of the solar wind.^[9] The Planetary Society expects LightSail 2's orbit to increase by as much as a kilometer per day.^[10]

A diagram showing LightSail 2's orbital configuration.

Structure

LightSail 2's modular design is based on a modular three-unit CubeSat, a small satellite format created for university-level space projects. One CubeSat-sized module carries the cameras, sensors and control systems, and the other two units will contain and deploy the solar sails.^[11]

The spacecraft contains four triangular sails, which combine to form a rectangular-shaped surface. The sails are made of Mylar, a reflective polyester film.^[12]

LightSail 1 flight

A preliminary technology demonstrator spacecraft, LightSail 1 (formerly LightSail-A^[1]), was launched as a secondary payload aboard a United Launch Alliance Atlas V rocket at 15:05 UTC on 20 May 2015 from Cape Canaveral Air Force Station, Florida.^[13][14][15] The mission delivered the satellite to an orbit where atmospheric drag was greater than the force exerted by solar radiation pressure.^[16]

Two days after the launch, however, the spacecraft suffered a software malfunction which made it unable to deploy the solar sail or to communicate.^[17] On 31 May 2015, The Planetary Society reported having regained contact with LightSail 1.^[18][19] After the solar panels were deployed on 3 June 2015, communications with the spacecraft were lost once more on 4 June. In this case, a fault with the battery system was suspected.^[20] Contact was then reestablished on 6 June,^[21] and the sail deployment was initiated on 7 June.^[22] At a conference on 10 June 2015, after photos of deployment were downloaded, the test flight was declared a success.^[23] The spacecraft reentered the atmosphere on 14 June 2015, ending the test flight.^[24][25]

Lightsail 2

LightSail 2's goal is to test whether solar sails are a viable form of spacecraft propulsion for CubeSats. The spacecraft team will measure whether there is any increase in LightSail 2's altitude after the spacecraft is deployed from a partner spacecraft, Prox-1, at an altitude of 720 kilometers.^[11] Prox-1 and LightSail 2 are secondary payloads aboard the first operational SpaceX Falcon Heavy launch, which will carry the STP-2 payload for the U.S. Air Force.^[26]

See also

• IKAROS, a Japanese solar sail, launched in May 2010
• NanoSail-D2, the successor to NanoSail-D, launched in November 2010
• Near-Earth Asteroid Scout, a solar sail planned to launch in 2018
• Sunjammer, a solar sail that was cancelled before launch in 2014

References

SpaceX
Vehicles	Rockets Current Falcon 9 Full Thrust In development Falcon 9 Block 5 Falcon Heavy ITS launch vehicle Retired Falcon 1 Falcon 9 v1.0 v1.1 Cancelled Falcon 1e Falcon 5 Falcon 9 Air Test vehicles Grasshopper (retired) F9R Dev1† (destroyed) DragonFly Spacecraft Dragon Dragon 2 Interplanetary Spaceship ITS tanker Reusable hardware Noteable Recovered boosters B1019 Reused boosters B1021 B1029 Reused capsules C106
Engines	Merlin (1A, 1B, 1C, 1D, Vacuum) Kestrel Draco SuperDraco Raptor Methalox thruster
Missions	Falcon 1 Demo 1† (FalconSAT-2) Demo 2† (DemoSat) Flight 3† Trailblazer PRESat NanoSail-D Explorers Ratsat RazakSAT Falcon 9 Demonstration flights Dragon Spacecraft Qualification Unit NASA COTS Demo Flight 1 Dragon C2+ Dragon ISS logistics CRS-1 CRS-2 CRS-3 CRS-4 CRS-5 CRS-6 CRS-7† CRS-8 CRS-9 CRS-10 CRS-11 CRS-12 CRS-13 CRS-14 CRS-15 CRS-16 CRS-17 CRS-18 CRS-19 CRS-20 (missions contracted up to CRS-26) Commercial satellites SES-8 Thaicom 6 Orbcomm OG2 × 6 AsiaSat 8 AsiaSat 6 ABS-3A / Eutelsat 115 West B TürkmenÄlem 52°E Orbcomm OG2 × 11 SES-9 JCSAT-14 Thaicom 8 ABS-2A / Eutelsat 117 West B JCSAT-16 Amos-6† Iridium NEXT 1–10 EchoStar 23 SES-10 Inmarsat-5 F4 BulgariaSat-1 Iridium NEXT 11–20 Intelsat 35e SES-11 Iridium NEXT 21–30 Koreasat 5A Hispasat 30W-6 Iridium NEXT 31–40 Paz SES-16 / GovSat-1 Bangabandhu-1 Scientific satellites CASSIOPE DSCOVR Jason-3 FormoSat-5 SAOCOM 1A Military satellites NROL-76 X-37B OTV-5 Falcon Heavy Demo Flight ArabSat 6A USAF STP-2 DSX FormoSat-7 LightSail 2 GPIM DSAC ISAT Moon tourists ViaSat 3 Red Dragon
Launch sites	Orbital Cape Canaveral, Florida CCAFS Launch Complex 40 Kennedy Launch Pad 39A Vandenberg, California Launch Complex 4E Brownsville, Texas Boca Chica Kwajalein, Marshall Islands Omelek Island† Suborbital McGregor test site New Mexico test site†
Landing sites	Autonomous spaceport drone ships Landing Zone 1, Cape Canaveral Launch Complex 4W, Vandenberg
Other facilities	Headquarters and factory (Hawthorne, California) Rocket development and test facility (McGregor, Texas) Satellite development facility (Redmond, Washington) Regional offices (Chantilly, Houston, Seattle, Washington DC)
Contracts	Commercial Orbital Transportation Services (COTS) Commercial Resupply Services (CRS) Commercial Crew Development (CCDev) Commercial Crew integrated Capability (CCiCap)
R&D programs	SpaceX reusable launch system development program Falcon 9 first-stage landing tests Interplanetary Transport System Red Dragon SpaceX satellite constellation
People	Elon Musk (CEO, CTO) Gwynne Shotwell (President & COO) Tom Mueller (Vice President of Propulsion Development)
Italics indicate unflown vehicles and future missions or sites. † denotes failed missions, destroyed vehicles and abandoned sites.