<\/p>\n
\u00a0\u00a0\u00a0\u00a0\u00a0On November 1 , 2022, an Earth orbiting probe ended its three and a half year mission with a firey plunge through the atmosphere.\u00a0 Amazingly, the mission was slated to last a year, so the sponsoring organization, The Planetary Society, got a lot more bang for their buck.\u00a0 Launched\u00a0 on June 25, 2019, the Lightsail 2 mission was the culmination of a series of events that actually can be traced back to 1976.\u00a0 It was the brain-child of Planetary Society co-founders Carl Sagan (1934-1996), Bruce Murray (1931-2013), and Louis Friedman (1941).\u00a0 Current PS CEO Bill Nye was a student in Sagan\u2019s class at Cornell in the spring of 1977 when Professor Sagan spoke about a plan the trio had pitched to NASA.\u00a0 Their idea was to send a lightsail powered craft with a large solar sail (nearly a kilometer long on each side) on a ten year mission to catch up to Halley\u2019s Comet to collect data and pictures up close.\u00a0 NASA passed on the concept but the rejection began another series of events that are still reverberating in the field of space exploration nearly a half century later.<\/span><\/p>\n \u00a0\u00a0\u00a0\u00a0\u00a0They were disappointed their concept was not embraced by NASA, but the rejection planted a seed:\u00a0 Why not form a non-governmental nonprofit organization to advocate for projects relating to astronomy, planetary science, and space exploration?\u00a0 Founded in 1980, The Society\u2019s goals have grown to include the search for both near-Earth objects and extraterrestrial life.\u00a0 The Planetary Society\u2019s mission statement reads:\u00a0 \u201cEmpowering the world\u2019s citizens to advance space science and exploration.\u201d\u00a0 They are actively engaged in advocating within NASA to fund space exploration and actively lobby Congress to support NASA\u2019s mission.\u00a0 In an age before the term \u2018crowdfunding\u2019 had even been coined, The Society had garnered enough support by 2009 to move the Lightsail program forward.<\/span><\/p>\n \u00a0\u00a0\u00a0\u00a0\u00a0So, what exactly is a light (or solar) sail? \u00a0 The concept can be distilled into a simple phrase, \u2018light for flight\u2019.\u00a0 Solar sails (also known as lightsails, light sails, and photo sails) are a form of spacecraft propulsion that uses radiation pressure exerted by sunlight on large surfaces to move a craft through space.\u00a0 It is analogous to sailing a boat where the pressure of the wind on a large surface area (the sail) propels a sailboat over the water.\u00a0 It is a low-cost method of sending exploratory craft on long duration missions in and beyond our solar system.\u00a0 In the frictionless vacuum of space, even the small, constant push of solar radiation on a solar sail can generate a great deal of speed without the weight or cost of burning chemical fuel.\u00a0 The concept has been around for a while, but it took some missteps before The Society was able to send out their first test craft for a true shakedown cruise.<\/span><\/p>\n \u00a0\u00a0\u00a0\u00a0\u00a0The Society\u2019s first attempt to launch a solar sail took place in 2005.\u00a0 To orbit the Cosmos 1 crowdfunded solar sail, The Society made arrangements to launch this first effort aboard a Russian Volna booster.\u00a0 A rocket malfunction prevented Cosmos 1 from reaching orbit and it eventually found a home at the bottom of the Barents Sea.\u00a0 NASA began their own solar sail program with the launch of a test probe called NanoSail-D on August 3, 2008.\u00a0 An issue with one of the first SpaceX Falcon 1 launch vehicles also prevented NS-D, like Cosmos 1, from reaching orbit.\u00a0 NASA\u2019s second attempt was launched in 2010 but the satellite containing the probe failed to deploy.\u00a0 In January 2011, the NanoSail-D package was unexpectedly ejected from the satellite and it deployed its sails a few days later.\u00a0 It managed to circle the Earth for 240 days gathering data about atmospheric drag before its orbit decayed and the probe burned up on re-entry.<\/span><\/p>\n \u00a0\u00a0\u00a0\u00a0\u00a0The Japanese are credited with orbiting the first spacecraft to successfully use solar sails in interplanetary space.\u00a0 Their IKAROS craft (Interplanetary Kite-Craft Accelerated by Radiation Of the Sun) took flight on May 20, 2010 and flew along with the Japanese Space Agency\u2019s (JAXA) Akatsuka probe to Venus.\u00a0 After the primary goals were met, JAXA continued gathering data with the probe until contact was finally lost in 2015.<\/span><\/p>\n \u00a0\u00a0\u00a0\u00a0\u00a0After the failure of the 2005 Cosmos 1 vehicle, roughly 50,000 donors contributed enough for The Planetary Society to make another attempt to orbit a solar sail in 2015.\u00a0 The program, now known as LightSail, launched the LightSail 1 test flight on June 1, 2015.\u00a0 Though LightSail 1 reentered the Earth\u2019s atmosphere only 14 days later, it provided a wealth of data the Society would use in the development of the LightSail 2 vehicle.\u00a0 As a further demonstration of light sail technology, LightSail 2 was designed to show that a small spacecraft could carry, deploy, and utilize relatively large solar sails for propulsion.<\/span><\/p>\n \u00a0\u00a0\u00a0\u00a0\u00a0LightSail 2 was carried into orbit packaged as a \u2018CubeSat\u2019.\u00a0 Picture a container roughly the size of a loaf of bread containing a Mylar solar sail.\u00a0 When fully extended, the solar sail covered an area of some 344 square feet (roughly 18.5 feet by 18.5 feet).\u00a0 According to Jason Davis (as reported in <\/span>The Planetary Report, Vol 43, Number 1, March 2023 Equinox Edition<\/span><\/i>), \u201cUsing a momentum wheel and three electromagnetic torque rods, the spacecraft oriented itself each orbit to get a slight push from sunlight.\u00a0 At LightSail 2\u2019s starting altitude of 450 miles, Earth\u2019s atmosphere is still thick enough to create drag and slow down a spacecraft.\u00a0 Using solar sailing, LightSail 2 slowed its decay rate and even overpowered drag on some occasions, showing that the technology is ready for wider use.\u00a0 LightSail 2 may be gone, but the future of solar sailing is bright.\u201d<\/span><\/p>\n \u00a0\u00a0\u00a0\u00a0\u00a0The technology demonstrated by LightSail 2 is now being analyzed as scientists and engineers examine more ways to utilize solar sails.\u00a0 For example, a spacecraft put in orbit to circle the poles of a planet would require constant acceleration to maintain its position.\u00a0 Such a \u2018pole sitter\u2019 probe would use the unlimited thrust provided by a solar sail to conduct long term studies of polar processes taking place on Earth, the Moon, and other planets.<\/span><\/p>\n \u00a0\u00a0\u00a0\u00a0\u00a0Solar sailing would also allow a spacecraft to be parked between the Earth and Sun.\u00a0 From this vantage point, the craft could monitor the Sun for solar storms like the one that caused the spectacular displays of northern lights in late March 23. \u00a0 These ejections of high-energy particles from the Sun can disrupt power grids, cause communication blackouts, and harm astronauts in space.\u00a0 Parking a vehicle to observe solar activity while being propelled by solar sails would allow for protective measures to be taken if they sound the alarm when a solar storm is first detected.<\/span><\/p>\n \u00a0\u00a0\u00a0\u00a0\u00a0The use of solar sails won\u2019t be limited to spacecraft exploring our own solar system.\u00a0 Solar sailing can propel spacecraft to distant destinations more quickly than conventional chemical rocket fuel propulsion.\u00a0 Missions to our outer planets and the halo of ancient objects orbiting the Sun well beyond Pluto (called the Oort Cloud), will become more cost effective.\u00a0 A new type of space telescope could be orbited to the outer reaches of the solar system where the Sun\u2019s gravitational field can be used like a magnifying lens to image and study distant exoplanets in high resolution.\u00a0 The \u2018jewel in the crown\u2019 of solar sailing would be sending a craft to our closest stellar neighbor, Proxima Centauri.\u00a0 An organization known as Breakthrough Starshot has proposed a mission that could send a small probe to this star system in as little as 20 years.\u00a0 Their version of solar sailing would use laser pulses to push the solar sail probe up to 20 percent the speed of light.\u00a0 Unlike conventional rockets that would take hundreds of years to make such a trip, a solar sail probe could be visiting Proxima Centauri in our lifetime.<\/span><\/p>\n \u00a0\u00a0\u00a0\u00a0\u00a0In the meantime, NASA is taking more interest in solar sailing.\u00a0 When the Artimus 1 rocket was launched in November 2022, it carried a CubSat containing their own NEA Scout probe (short for Near-Earth Asteroid Scout).\u00a0 The plan was to visit Asteroid 2020 GE, thus becoming the smallest asteroid to be visited by a spacecraft.\u00a0 NEA-Scout\u2019s solar sail was two and a half times larger than the one deployed by LightSail 2.\u00a0 It would have departed the Earth\/Moon system to perform a slow flyby of the asteroid.\u00a0 Unfortunately, NEA-Scout never \u2018phoned home\u2019 and the mission was lost before it really began.<\/span><\/p>\n \u00a0\u00a0\u00a0\u00a0\u00a0NASA had another more ambitious solar sail mission on the drawing board called Solar Cruiser. \u00a0 Like the vehicle mentioned earlier, this craft would have utilized a solar sail the size of six tennis courts to park between the Earth and Sun on solar storm watch.\u00a0 Soon after the loss of the NEA-Scout probe, NASA announced it was not longer pursuing Solar Cruiser.\u00a0 The only future testing NASA has scheduled is slated for late in 2023 when it launches ACS3.\u00a0 The Advanced Composite Solar Sail System will be used to test future solar sail technologies.\u00a0 They will use carbon fiber booms (which are 75 percent lighter than metal booms and less prone to buckling) to support a solar sail of some 860 square feet (nearly 30 feet on a side).\u00a0 The mission\u2019s principal investigator, W. Keats Wilkie wants to see the technology of solar sailing \u2018mature\u2019 so scientists will begin to see the value for future exploration.\u00a0 Wilkie says, \u201cOnce we start flying these, we\u2019ll get people who say, \u201cHey, this isn\u2019t science fiction any more.\u2019\u201d<\/span><\/p>\n \u00a0\u00a0\u00a0\u00a0\u00a0The French aerospace company Gamma recently launched the first of two probes, dubbed Alpha and Beta, to test a boomless technology first employed by the JAXA IKAROS craft.\u00a0 While little information has been shared since the Alpha test, their concept is to use a spinning core to deploy the solar sails without the need for rigid booms.\u00a0 Gamma hopes to provide low cost solar sailing platforms for scientific explorations to Venus, the outer planets, and even the Oort Cloud beyond Pluto.\u00a0 Co-founder Andrew Nutter would like to see their probes hitch a ride on energetic rocket launches like the ones needed to travel to the Moon, for instance:\u00a0 \u201cIt allows us to launch as a rideshare on many different missions without needing a private launch, reducing launch cost.\u201d<\/span><\/p>\n \u00a0\u00a0\u00a0\u00a0\u00a0One disadvantage of using solar sails for deep space propulsion is the angle they need to maintain to keep sunlight providing thrust.\u00a0 If their trajectory requires the angle between the solar sail and the Sun to be 35 percent, for example, thrust is lost.\u00a0 A version of a solar sail called a \u2018diffractive sail\u2019 might overcome some of these limitations.\u00a0 According to Davis, \u201cThese sails use tiny gratings that diffract incoming light through the sail like a prism rather than reflecting it.\u00a0 The diffracted light has a force component that pushes the sail in a direction perpendicular to the incoming solar photons, allowing the sail to capture the full force of the Sun\u2019s rays.\u00a0 Unlike the Mylar sails used on LightSail 2, diffractive sails would be nearly transparent and the light passing through them would give them a rainbow-like appearance.<\/span><\/p>\n \u00a0\u00a0\u00a0\u00a0\u00a0Amber Dubill is the principal investigator for the John Hopkins University Applied Physics Laboratory.\u00a0 She sees the potential of diffractive solar sails:\u00a0 \u201cWe think we can overcome a lot of the challenges that are keeping traditional solar sailing from becoming widely implemented much more across the board.\u201d\u00a0 Another area being studied is the electric sail, or E-Sail.\u00a0 A small, spinning core with 20 thin, positively charged wires extending up to 12 miles out from the craft would generate even more speed than a traditional sail.\u00a0 As the positively charged photos from the Sun encounter these wires, they \u2018plus\u2019 and \u2018plus\u2019 forces would repel each other.\u00a0 A trip to the edge of the Sun\u2019s influence, called the Heliopause, could be accomplished in half the time as a mission using traditional solar sails.<\/span><\/p>\n \u00a0\u00a0\u00a0\u00a0\u00a0Though the LightSail 2 mission lasted much longer than The Society had planned, in the end, it was brought back to Earth by atmospheric drag.\u00a0 The force of the thickening air molecules pushing against the sail eventually tore it apart.\u00a0 Data from its demise will not only help with future solar sail designs, it may also aid in cleaning up some of the 25,000 objects in Earth orbit larger than four inches across.\u00a0 Scientists point out that should there be alien civilizations looking for planets harboring advanced life forms, they need only observe the swarm of working and derelict satellites orbiting the Earth to find us.\u00a0 The damage this debris field can pose for the International Space Station and satellite networks can not be ignored.\u00a0 If LightSail 2\u2019s legacy includes helping us declutter our near space by intentionally deorbiting space junk, then that will make its mission a double success.<\/span><\/p>\n \u00a0\u00a0\u00a0\u00a0\u00a0A company called Vestigo Aerospace is currently studying the concept aided by personnel who also worked on the LightSail program.\u00a0 They would like to equip all satellites with drag sails.\u00a0 When a satellite reaches the end of its mission life, the drag sail would be deployed to hasten their reentry into the Earth\u2019s atmosphere.\u00a0 With this much junk orbiting the Earth, we are well beyond the time when such \u2018end of mission\u2019 planning should have been required for all new spacecraft.\u00a0 Interest in this project by companies like Vestigo tells us it is better late than never to begin cleaning up the Earth\u2019s near space.<\/span><\/p>\n \u00a0\u00a0\u00a0\u00a0\u00a0As Davis states at the end of his excellent history of solar sailing, \u201cThe co-founders of The Planetary Society believed that sailing on sunlight could revolutionize space travel.\u00a0 As the LightSail 2 mission ends, the baton is being passed to the next generation of solar sailors.\u00a0 Who knows what distant shores they will visit as they explore our cosmic ocean?\u201d\u00a0<\/span><\/p>\n Top Piece Video:\u00a0 Dare we say\u00a0Sail On Solar Sailor<\/em>?<\/p>\n","protected":false},"excerpt":{"rendered":" \u00a0\u00a0\u00a0\u00a0\u00a0On November 1 , 2022, an Earth orbiting probe ended its three and a half year mission with a firey plunge through the atmosphere.\u00a0 Amazingly, the mission was slated to last a year, so the sponsoring organization, The Planetary Society, got a lot more bang for their buck.\u00a0 Launched\u00a0 on June 25, 2019, the […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[11,8,9],"tags":[],"class_list":["post-2803","post","type-post","status-publish","format-standard","hentry","category-education","category-from-the-vaults","category-woas"],"_links":{"self":[{"href":"https:\/\/www.woas-fm.org\/index.php?rest_route=\/wp\/v2\/posts\/2803","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.woas-fm.org\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.woas-fm.org\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.woas-fm.org\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.woas-fm.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=2803"}],"version-history":[{"count":3,"href":"https:\/\/www.woas-fm.org\/index.php?rest_route=\/wp\/v2\/posts\/2803\/revisions"}],"predecessor-version":[{"id":2806,"href":"https:\/\/www.woas-fm.org\/index.php?rest_route=\/wp\/v2\/posts\/2803\/revisions\/2806"}],"wp:attachment":[{"href":"https:\/\/www.woas-fm.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=2803"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.woas-fm.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=2803"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.woas-fm.org\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=2803"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}