title: Alois Brunner

text: He fled West Germany only in 1954, on a fake Red Cross passport, first to Rome, then Egypt, where he worked as a weapons dealer, and then to Syria, where he took the pseudonym of Dr Georg Fischer. In Syria, he was hired as a government adviser. The exact nature of his work is unknown. Syria had long refused entry to French investigators as well as to Nazi hunter Serge Klarsfeld, who spent nearly 15 years bringing the case to court in France. Simon Wiesenthal tried unsuccessfully to trace Brunner's whereabouts. However, communist East Germany, led by Erich Honecker, negotiated with Syria in the late 1980s to have Brunner extradited and arrested in Berlin. The government of Syria under Hafez al-Assad was close to extraditing Brunner to East Germany, but the fall of the Berlin Wall in November 1989 severed contacts between the two regimes and halted the extradition plan.


title: Alois Brunner

text: In the "Bunte" interview, Brunner was quoted as saying he regrets nothing and that all of the Jews deserved their fate. In a 1987 telephone interview with Chuck Ashman, published in the "Chicago Sun Times", Brunner was reported to have said: "All of [the Jews] deserved to die because they were the Devil's agents and human garbage. I have no regrets and would do it again." (While the attribution of this quotation to Brunner was never directly disputed, Ashman was a controversial figure among his peers as journalists, and had previously been convicted of check fraud.) In an interview with Austrian neo-nazi Gerd Honsik, Brunner denied claims of gas chambers.


title: Alois Brunner

text: Until the early 1990s, he lived in an apartment building on 7 Rue Haddad in Damascus, meeting with foreigners and occasionally being photographed. In the 1990s, the French Embassy received reports that Brunner was meeting regularly and having tea with former East German nationals. According to "The Guardian", he was last seen alive by reliable witnesses in 1992.


title: Alois Brunner

text: In December 1999, unconfirmed reports surfaced that Brunner had died in 1996 and been buried in a Damascus cemetery. However, he was reportedly sighted at the Meridian Hotel in Damascus by German journalists that same year, where he was said to be living under police protection. The last reported sighting of him was at the Meridian Hotel in late 2001 by German journalists.


title: Alois Brunner

text: In 2011, "Der Spiegel" reported that the German intelligence service Bundesnachrichtendienst had destroyed its file on Brunner in the 1990s, and that remarks in remaining files contain conflicting statements as to whether Brunner had worked for the BND at some point.


title: Alois Brunner

text: In 1961 and 1980, letter bombs were sent to Brunner while he was a resident in Syria. As a result of the letter bomb he received in 1961, he lost an eye, and in 1980, he lost the fingers on his left hand when the parcel blew up in his hands. A 2018 article in "Newsweek" by journalist Ronen Bergman disclosed that the 1961 bomb was sent by Military Intelligence Unit 188, a branch of the Israel Defense Forces and was the first target of a new method of letter bomb that was developed for deployment against ex-Nazi scientists working for Gamal Abdel Nasser in developing missiles targeting Israel. The article, excerpted from Bergman's book "Rise and Kill First", says that Brunner was located by Israeli spy Eli Cohen. According to information released by the Israeli intelligence agency Mossad, it was behind the 1980 bomb.


title: Alois Brunner

text: Germany and other countries unsuccessfully requested his extradition. He was twice sentenced to death "in absentia" in the 1950s; one of those convictions was in France in 1954. In August 1987, an Interpol "red notice" was issued for him. In 1995, German state prosecutors in Cologne and Frankfurt posted a $330,000 reward for information leading to his arrest.


title: Alois Brunner

text: On 2 March 2001, he was found guilty "in absentia" by a French court for crimes against humanity, including the arrest and deportation of 345 orphans from the Paris region (which had not been judged in the earlier trials) and was sentenced to life imprisonment. According to Serge Klarsfeld, the trial was largely symbolic—an effort to honour the memories of victims. Klarsfeld's own father, arrested in 1943, was reportedly one of Brunner's victims.


title: Alois Brunner

text: In 2004, the television series "Unsolved History", in an episode titled "Hunting Nazis", used facial recognition software to compare Alois Brunner's official SS photograph with a recent photo of "Georg Fischer" from Damascus, and came up with a match of 8.1 points out of 10, which they claimed was, despite the elapse of over 50 years in aging, equivalent to a match with 95% certainty.


title: Alois Brunner

text: In 2005, Brazilian police were reportedly investigating whether a suspect living in the country under an assumed name was actually Alois Brunner. Deputy Commander Asher Ben-Artzi, the head of Israel's Interpol and Foreign Liaison Section, passed on a Brazilian request for Brunner's fingerprints to Nazi hunter Efraim Zuroff, head of the Simon Wiesenthal Center in Jerusalem, but Zuroff could not find any.


title: Alois Brunner

text: In July 2007, the Austrian Justice Ministry declared that they would pay €50,000 for information leading to his arrest and extradition to Austria.


title: Alois Brunner

text: In March 2009, the Simon Wiesenthal Center acknowledged the "slim" possibility of Brunner still being alive. In 2011, some media reports included him on a list of "World's Most Wanted" criminals.


title: Alois Brunner

text: In 2013, the Simon Wiesenthal Center described Brunner as "the most important unpunished Nazi war criminal who may still be alive". Brunner was last seen in 2001 in Syria, whose government had long rebuffed international efforts to locate or apprehend him, but was presumed dead .


title: Alois Brunner

text: In April 2014, Brunner was removed from the Simon Wiesenthal Center's list of most-wanted Nazi war criminals.


title: Alois Brunner

text: On 30 November 2014, the Simon Wiesenthal Center reported receiving credible information that Brunner had died in Syria in 2010. He would have been 97 or 98 years old. Partly due to the ongoing Syrian Civil War, the exact date and place of death were unknown.


title: Alois Brunner

text: According to the director of the Wiesenthal Center, Efraim Zuroff, the information came from a "reliable" former German secret service agent who had served in the Middle East. The information was also reported in the press. The new evidence revealed that Brunner was buried in an unknown location in Damascus around 2010, unrepentant of his crimes to the end. Zuroff said that, owing to the civil war in Syria, the exact location of Brunner's grave was unknowable.


title: Alois Brunner

text: In 2017, the French quarterly review "" published an investigation about Brunner's last years in Syria by journalists Hédi Aouidj and Mathieu Palain. Three former security guards in charge of the protection of Brunner recounted how the Assad family used him to train intelligence services staff, then kept him under house arrest in a Damascus basement throughout the 1990s until his death in December 2001. One of the former guards said that Brunner, who went by the name of Abu Hussein, "suffered and cried a lot in his final years", "couldn't even wash" and ate only "an egg or a potato" a day. According to the report at the time of his death, Brunner had converted to Islam. Brunner was buried in secret, at night in the Al-Affif cemetery in Damascus. Serge Klarsfeld called the report "highly credible".


title: Mary Matalin

text: Mary Joe Matalin (born August 19, 1953) is an American political consultant well known for her work with the Republican Party. She has served under President Ronald Reagan, was campaign director for George H. W. Bush, was an assistant to President George W. Bush, and counselor to Vice President Dick Cheney until 2003. Matalin has been chief editor of Threshold Editions, a conservative publishing imprint at Simon & Schuster, since March 2005. She is married to Democratic political consultant James Carville. She appears in the award-winning documentary film "" and also played herself, opposite her husband, James Carville, John Slattery, and Mary McCormack in the short lived HBO series "K Street".


title: Mary Matalin

text: Matalin grew up in the Chicago suburb of Burnham, Illinois, the daughter of Eileen (née Emerson), who ran beauty salons, and Steven Matalin, a steel mill worker. Her paternal grandparents were Croatian immigrants and her mother was of Irish descent. Matalin originally intended to follow her mother into the beauty salon profession, and briefly considered becoming a model. Instead, Matalin attended Thornton Fractional North High School and attended Western Illinois University for college and Hofstra University School of Law, where she dropped out after one year.


title: Mary Matalin

text: Matalin's first campaign was Illinois Lieutenant Governor Dave O'Neal's bid for the U.S. Senate in 1980, a race O'Neal lost to Alan Dixon. After O'Neal's loss, Matalin began her career with the Republican National Committee, where she would remain for nearly two decades as a key Republican strategist. Leaving briefly to attend Hofstra University School of Law, Matalin dropped out after just one year, and in 1984 returned to the RNC. She rose quickly, as an aide to Richard Bond and Chief of Staff to RNC co-Chairperson Betty Heitman in 1985. A year later, Matalin gained national attention when she joined George H. W. Bush's 1988 presidential campaign, working as both Deputy Political Director and Midwest Regional Political Director in the primaries. After the election, Matalin was appointed Chief of Staff to then RNC Chairman Lee Atwater. In that capacity, she would in effect run the RNC for nearly a year, as Atwater—his health declining due to an inoperable brain tumor—spent 170 days in the hospital between his diagnosis in early March 1990 and eventual death on March 29, 1991.


title: Mary Matalin

text: In 1992, Matalin served as the deputy campaign manager for political operations on Bush's reelection campaign. Ironically, she served in this role while dating her future husband, James Carville, who was chief strategist for the Clinton campaign.


title: Mary Matalin

text: Matalin was a host of CNN's "Crossfire" political debate show, and in 1993, she co-hosted "Equal Time", which aired on the CNBC business television channel. Matalin was also the host of her own talk radio show in the 1990s, "The Mary Matalin Show", which was carried on the CBS Radio Network. She is currently on the nationally syndicated radio program "Both Sides Now w/ Huffington & Matalin", hosted by Mark J. Green and aired weekends on 120 stations.


title: Mary Matalin

text: Matalin worked in various roles in the George W. Bush administration. She resigned on December 31, 2002.


title: Mary Matalin

text: Matalin also appeared alongside her husband James Carville in HBO's 2003 television show "K Street" where she and her husband played versions of themselves as they lobbied real and fictional politicians. The show was directed by Academy Award winner Steven Soderbergh and featured a cast of fictional and real characters working in the political sphere.


title: Mary Matalin

text: In March 2005, Matalin was hired as chief editor of a new conservative publishing imprint, Threshold Editions, for CBS-owned Simon & Schuster. On August 1, 2008, this division released "The Obama Nation", written by Jerome Corsi, who co-authored "". Other notable titles published by Threshold Editions includes Dick Cheney's "", Karl Rove's "Courage and Consequence" and a number of Glenn Beck books including "Cowards", and "".


title: Mary Matalin

text: In April 2006, she was appointed Treasurer of Virginia Republican Senator George Allen's re-election committee. She worked on the presidential campaign of Fred Thompson until January 2008, when Thompson dropped out of the race.


title: Mary Matalin

text: In 2008, Matalin joined the Board of Directors at The George Washington University's Cheney Cardiovascular Institute. Matalin also serves on numerous other boards including The Water Institute of the Gulf (TWIG), Conscience Cause, The New Orleans Jazz Orchestra (NOJO) and the Tulane President's Council.


title: Mary Matalin

text: Matalin appears in the 2008 award-winning documentary on Lee Atwater, "". Speaking about Lee, she says, "They had to kill the messenger because they couldn't kill the message. They had to turn him into the Boogie Man. Satan incarnate."


title: Mary Matalin

text: On April 26, 2009, Matalin returned to CNN as a political contributor, joining her husband, James Carville on a special "First 100 Days" edition of "State of the Union with John King".


title: Mary Matalin

text: In 2010, Matalin and husband James Carville were named co-chairs of Super Bowl XLVII Host Committee, held in 2013 in New Orleans.


title: Mary Matalin

text: In 2012, Matalin and husband Carville began appearing together in "Cocktail Party" commercials for Maker's Mark Kentucky Straight Bourbon.


title: Mary Matalin

text: Believing that farm animals should be treated humanely, Matalin teamed up with PETA to produce a video in 2013, encouraging Indiana lawmakers to vote against "ag-gag" bills that would ban unapproved videotaping on farms and businesses.


title: Mary Matalin

text: On May 5, 2016, Matalin announced she has changed her party registration to Libertarian, as that party represents her "Jeffersonian, Madisonian [...] constitutional principles" better than the Republican Party, after the GOP lost two successive presidential elections and was "falling apart." While maintaining the change was not because of Donald Trump becoming the presumptive Republican nominee, she criticized Trump for "his high school boy antics with women." She endorsed Austin Petersen for president in May 2016.


title: Mary Matalin

text: She was named PETA's "Person of the Year" in December 2016. The organization cited her willingness to fight for the humane treatment of monkeys and farm animals, and "for setting a tremendous example of compassion that all Americans can follow."


title: Mary Matalin

text: On November 25, 1993 (Thanksgiving Day), Matalin married James Carville, a political strategist for candidates of the Democratic Party, in New Orleans. They have two daughters.


title: Mary Matalin

text: Matalin and Carville have gone on record saying they do not talk politics at home. The best example of contention between the two, aside from appearances on talk shows, is the 1993 movie "The War Room". In the 1992 political campaign, Matalin and Carville were staffing opposing campaigns. Matalin wrote the best-selling book "All's Fair: Love, War and Running for President" with Carville and co-author Peter Knobler. In April 2004, she published the book "Letters to My Daughters". In 2008, Carville and Matalin moved their family to New Orleans. On April 26, 2009, "The Times-Picayune" carried a joint op-ed "Point of View" by Matalin and Carville on their reasons for settling in New Orleans. Matalin and Carville are profiled in the Politics chapter of the book "The Compatibility Matrix".


title: The Crystal Method

text: The Crystal Method is an American electronic music act formed in Las Vegas, Nevada, by Ken Jordan and Scott Kirkland in the early 1990s. They were pioneers of the big beat genre and their music has appeared in numerous TV shows, films, video games, and advertisements. Their 1997 debut studio album "Vegas" was certified platinum in 2007, and saw follow-ups "Tweekend", "Legion of Boom", "Divided by Night", and "The Crystal Method". In 2017, Ken Jordan retired from music and left the group, with Scott Kirkland adopting The Crystal Method as a solo moniker.


title: The Crystal Method

text: The Crystal Method originally had two members, Ken Jordan and Scott Kirkland. Before The Crystal Method was formed, Jordan and Kirkland started working on music while working at a grocery store. Jordan was also a local DJ in Las Vegas as well as the college radio program director at UNLV. Jordan taught Kirkland how to DJ, and when Jordan moved to Los Angeles to work for a producer, Kirkland took over his job DJing at the local club. Kirkland also moved out to Los Angeles, and they formed The Crystal Method in 1993.


title: The Crystal Method

text: While working as a production duo for a rapper, a person named Crystal would handle transportation needs. The rapper repeatedly referred to her method of transportation as "The Crystal Method." The pair adopted the name based on the layout of the three words and the sound of the name.


title: The Crystal Method

text: By the early '90s, both Ken Jordan and Scott Kirkland had moved from Las Vegas to Los Angeles. Jordan and Kirkland bought a house together, in La Crescenta, Glendale, California, which had a small underground shelter beneath the front lawn. Originally intending to turn the shelter into a studio, it proved to be an unrealistic idea and the duo set up a studio in their house which was located near a 210 Freeway overpass. They subsequently named their studio The Bomb Shelter. They were interviewed on the front lawn of the house in the documentary "Better Living Through Circuitry".


title: The Crystal Method

text: After The Bomb Shelter was built, a tape of The Crystal Method's music found its way to British DJ Justin King. King was interested in starting a record label that would showcase American electronic dance acts. Together with Steve Melrose, King formed the record label City of Angels Record Label. The first official release from the City of Angels label was The Crystal Method's "Now is the Time". The Crystal Method were signed to Outpost Recordings in 1996.


title: The Crystal Method

text: After the band signed with Outpost, they began working on their debut album. The group's final single on the City of Angels Record Label was "Keep Hope Alive". Their next single was "Come2gether", from the "" soundtrack.


title: The Crystal Method

text: On September 8, 1997, The Crystal Method released their debut studio album, "Vegas". "Vegas" peaked at number 92 on the "Billboard" 200. It was certified gold by the RIAA in 1998, then platinum in 2007.


title: The Crystal Method

text: The album's release was supported by its four singles; "Keep Hope Alive", "Trip Like I Do", "Busy Child", and "Comin' Back".


title: The Crystal Method

text: A reworking of "Trip Like I Do", called "(Can't You) Trip Like I Do", was also included as a collaborative effort with Filter on soundtrack to the film adaptation of "Spawn" in 1997 and on the soundtrack of Michael Benveniste's "Tedd Can" chronicles.


title: The Crystal Method

text: In 1999, the band recorded their second studio album, "Tweekend", which featured more guest artists than "Vegas". The album was released in July 2001, and peaked at number 32 on the Billboard 200, which remains the group's highest album chart position to date.


title: The Crystal Method

text: Featured guests from the album include Rage Against the Machine guitarist Tom Morello, Stone Temple Pilots vocalist Scott Weiland, and others, like Doug Grean, DJ Swamp, Ryan "Ryu" Maginn, and Julie Gallios. Four singles were released from "Tweekend": "Wild, Sweet and Cool", "Murder", "Blowout", "Name of the Game".


title: The Crystal Method

text: Jordan and Kirkland formerly ran a radio show called "Community Service" which aired Friday nights on radio station Indie 103.1, in California. They played music and hosted guests including Death in Vegas and Unkle.


title: The Crystal Method

text: A year after the release of "Tweekend", The Crystal Method released a continuous mix album based on their radio show, titled "Community Service". The album does not feature any new studio material from The Crystal Method, but is composed of remixes of bands like P.O.D., Rage Against the Machine, and Garbage, plus remixes of songs from "Tweekend". Their remix of P.O.D.'s "Boom" from this album, also appeared in the video game "Amplitude".


title: The Crystal Method

text: "Community Service" peaked at number 160 on the Billboard 200, number five on the Top Electronic Albums chart, and number 15 on the Top Independent Albums chart.


title: The Crystal Method

text: After the release of "Community Service", The Crystal Method went back into the studio to record their third album, "Legion of Boom". During the recording, they used the house as their recording studio instead of The Bomb Shelter.


title: The Crystal Method

text: In December 2003, the single "Born Too Slow", with vocals from John Garcia and guitar by Wes Borland was released. "Legion of Boom" was released on January 13, 2004, and peaked at number 36 on the Billboard 200. It sold over 25,000 copies in its first week. The track was also part of the soundtrack of the 2003 video game "", used prominently in its demo.


title: The Crystal Method

text: The other single released from "Legion of Boom", "Starting Over", featured vocals from Rahzel. No other singles were released but other songs, including "Weapons of Mass Distortion", "Bound Too Long" and "Realizer", appeared in various movies and TV shows. "I Know It's You" appeared in the trailer for the film "", and includes vocals from Milla Jovovich.


title: The Crystal Method

text: In 2005, the album was nominated for the Best Electronic/Dance Album Grammy, the first year that category existed. It lost to "Kish Kash" by Basement Jaxx.


title: The Crystal Method

text: Around this time, Jordan and Kirkland formed their own record label, called Tiny E Records. Also in 2005, Jordan and Kirkland composed an original theme for the TV series "Bones", which remained in use for seven seasons before Jordan and Kirkland remixed the theme which has been in use since the beginning of season 8.


title: The Crystal Method

text: In 2004, The Crystal Method collaborated with Alan Parsons, on his fourth solo album since the demise of the Alan Parsons Project, "A Valid Path", on the song "We Play The Game".


title: The Crystal Method

text: On April 5, 2005, The Crystal Method released their sequel to "Community Service", titled "Community Service II", another continuous mix of electronica songs and remixes of music by artists including The Doors, Unkle, New Order and Smashing Pumpkins. The album peaked at number 31 on the Top Independent Albums chart and number 8 on the Top Electronic albums chart.


title: The Crystal Method

text: A 5 track EP, "Community Service II Exclusives", was released through the iTunes Store. It included one new track, "Badass", and full versions of four tracks from "Community Service II". It was removed from the iTunes store not long after it was released.


title: The Crystal Method

text: The group composed and performed the score for the film "London", which was released in February 2006. The soundtrack album included excerpts from the score, two Crystal Method vocal tracks—"Smoked" and "Glass Breaker", which were also released as a single—and songs by artists like Evil Nine, The Out Crowd, and The Perishers.


title: The Crystal Method

text: Shortly after the release of the "London" soundtrack, The Crystal Method was approached by Nike to take part in a series of music releases specifically designed to be listened to while running. The group's contribution, ""—the first in the series—was initially released digitally, in June 2006, with the physical release following a year later. "Drive" peaked at number 23 on the Top Electronic Albums chart. The album, a 45-minute continuous mix, starts off slow, increases in tempo, and slows at the end, following the arc of a typical distance run. In 2006 the track "Robogirl" released by the duo appeared on "Dance Dance Revolution: SuperNOVA".


title: The Crystal Method

text: In 2007, ten years after its original release, the group's debut album, "Vegas" was certified platinum by the RIAA. One month later, a special edition of the album was released, with a second disc including remixes and video.


title: The Crystal Method

text: In late 2008, the group remixed their song "Now Is the Time". Where the original version featured samples of Jesse Jackson, this "Vote '08 Remix" used samples of Barack Obama, marking the presidential election.


title: The Crystal Method

text: Following the release of "Legion of Boom", The Crystal Method began construction of a new, full-sized recording studio in Los Angeles—Crystalwerks. When it was finished, they began work on their fourth studio album, "Divided by Night".


title: The Crystal Method

text: On April 14, 2009, The Crystal Method released the digital single "Drown in the Now". A second single, "Black Rainbows", was released via Beatport two weeks later.


title: The Crystal Method

text: The "Divided by Night" tour started in Boston on May 6, and the album was released the following week. It peaked at number 38 on the Billboard 200, number two on the Top Electronic Albums chart, and number four on the Top Independent Albums chart, and also granted the duo another Grammy nomination. The album features guest artists including LMFAO, Peter Hook (of New Order), Matisyahu, Meiko, Justin Warfield, Emily Haines (of Metric), and Jason Lytle.


title: The Crystal Method

text: "", released in August 2009, included a number of Crystal Method songs and remixes, including "Drown in the Now" and "Now Is the Time".


title: The Crystal Method

text: Originally scheduled for a June, 2013, release, their eponymous fifth studio album "The Crystal Method" was delayed by a surgery to remove a cyst in Scott Kirkland's brain. The album was released on January 14, 2014.


title: The Crystal Method

text: When approximately halfway creating the next album process, Scott Kirkland received news that he had developed "what's called a benign posterior fossa arachnoid cyst that needed to be removed from my head." He explains, "It's a simple procedure as far as brain surgery goes, but they still had to cut into my skull and noodle around in there. The surgery wasn't as bad as the infection afterwards, which landed me in the ICU for ten days. Thankfully, I made it out okay. In hindsight, as weird as it sounds, I think we were able to make a better record because we came through this." Following his 2013 recovery, Scott regrouped with Ken Jordan and continued working on the album.


title: The Crystal Method

text: In late 2013, the duo were asked to compose the score and opening theme of "Almost Human", a science fiction crime drama airing on Fox. The same year, two of the Crystal Method's songs, "Play for Real" and "Over It", were featured in the 2013 racing game "".


title: The Crystal Method

text: In early 2017, Ken Jordan decided to retire from music, and left The Crystal Method, however Scott Kirkland continues to produce and play shows under the moniker as a solo project.


title: The Crystal Method

text: In 2017, Scott as The Crystal Method went on tour with Tool, and collaborated with Tool bass player, Justin Chancellor, on a side project called Bandwidth.


title: The Crystal Method

text: On July 17, 2018, Scott Kirkland announced the next Crystal Method album was titled "The Trip Home" and would be released on September 28, 2018. Kirkland also announced the first single, "Holy Arp", would be released on July 27, 2018.


title: The Crystal Method

text: On September 7, 2018, Kirkland announced the second single "There's a Difference" featuring Franky Perez, which released the same day.


title: The Crystal Method

text: On November 26, 2018, Kirkland and Jean-Michel Jarre announced that they would be collaborating on a track on Jean-Michel Jarre's next electronica album.


title: The Crystal Method

text: On February 18th, 2022, The Crystal Method announced a follow-up album to "The Trip Home" titled "The Trip Out" while simultaneously releasing their first single "Post Punk" featuring DJ Hyper and Iggy Pop.


title: The Crystal Method

text: The second single "Watch Me Now" featuring Koda & VAAAL debuted April 11th, live on NBC's "American Song Contest". The album was released on Ultra Records on April 15th, 2022.


title: Solar sail

text: Solar sails (also known as light sails and photon sails) are a method of spacecraft propulsion using radiation pressure exerted by sunlight on large mirrors. A number of spaceflight missions to test solar propulsion and navigation have been proposed since the 1980s. The first spacecraft to make use of the technology was IKAROS, launched in 2010.


title: Solar sail

text: A useful analogy to solar sailing may be a sailing boat; the light exerting a force on the mirrors is akin to a sail being blown by the wind. High-energy laser beams could be used as an alternative light source to exert much greater force than would be possible using sunlight, a concept known as beam sailing. Solar sail craft offer the possibility of low-cost operations combined with long operating lifetimes. Since they have few moving parts and use no propellant, they can potentially be used numerous times for delivery of payloads.


title: Solar sail

text: Solar sails use a phenomenon that has a proven, measured effect on astrodynamics. Solar pressure affects all spacecraft, whether in interplanetary space or in orbit around a planet or small body. A typical spacecraft going to Mars, for example, will be displaced thousands of kilometers by solar pressure, so the effects must be accounted for in trajectory planning, which has been done since the time of the earliest interplanetary spacecraft of the 1960s. Solar pressure also affects the orientation of a spacecraft, a factor that must be included in spacecraft design.


title: Solar sail

text: The total force exerted on an 800 by 800 metre solar sail, for example, is about at Earth's distance from the Sun, making it a low-thrust propulsion system, similar to spacecraft propelled by electric engines, but as it uses no propellant, that force is exerted almost constantly and the collective effect over time is great enough to be considered a potential manner of propelling spacecraft.


title: Solar sail

text: Johannes Kepler observed that comet tails point away from the Sun and suggested that the Sun caused the effect. In a letter to Galileo in 1610, he wrote, "Provide ships or sails adapted to the heavenly breezes, and there will be some who will brave even that void." He might have had the comet tail phenomenon in mind when he wrote those words, although his publications on comet tails came several years later.


title: Solar sail

text: James Clerk Maxwell, in 1861–1864, published his theory of electromagnetic fields and radiation, which shows that light has momentum and thus can exert pressure on objects. Maxwell's equations provide the theoretical foundation for sailing with light pressure. So by 1864, the physics community and beyond knew sunlight carried momentum that would exert a pressure on objects.


title: Solar sail

text: Jules Verne, in "From the Earth to the Moon", published in 1865, wrote "there will some day appear velocities far greater than these [of the planets and the projectile], of which light or electricity will probably be the mechanical agent ... we shall one day travel to the moon, the planets, and the stars." This is possibly the first published recognition that light could move ships through space.


title: Solar sail

text: Pyotr Lebedev was first to successfully demonstrate light pressure, which he did in 1899 with a torsional balance; Ernest Nichols and Gordon Hull conducted a similar independent experiment in 1901 using a Nichols radiometer.


title: Solar sail

text: Svante Arrhenius predicted in 1908 the possibility of solar radiation pressure distributing life spores across interstellar distances, providing one means to explain the concept of panspermia. He apparently was the first scientist to state that light could move objects between stars.


title: Solar sail

text: Konstantin Tsiolkovsky first proposed using the pressure of sunlight to propel spacecraft through space and suggested, "using tremendous mirrors of very thin sheets to utilize the pressure of sunlight to attain cosmic velocities".


title: Solar sail

text: Friedrich Zander (Tsander) published a technical paper in 1925 that included technical analysis of solar sailing. Zander wrote of "applying small forces" using "light pressure or transmission of light energy to distances by means of very thin mirrors".


title: Solar sail

text: JBS Haldane speculated in 1927 about the invention of tubular spaceships that would take humanity to space and how "wings of metallic foil of a square kilometre or more in area are spread out to catch the Sun's radiation pressure".


title: Solar sail

text: J. D. Bernal wrote in 1929, "A form of space sailing might be developed which used the repulsive effect of the Sun's rays instead of wind. A space vessel spreading its large, metallic wings, acres in extent, to the full, might be blown to the limit of Neptune's orbit. Then, to increase its speed, it would tack, close-hauled, down the gravitational field, spreading full sail again as it rushed past the Sun."


title: Solar sail

text: Carl Sagan, in the 1970s, popularized the idea of sailing on light using a giant structure which would reflect photons in one direction, creating momentum. He brought up his ideas in college lectures, books, and television shows. He was fixated on quickly launching this spacecraft in time to perform a rendezvous with Halley's Comet. Unfortunately, the mission didn't take place in time and he would never live to finally see it through.


title: Solar sail

text: The first formal technology and design effort for a solar sail began in 1976 at Jet Propulsion Laboratory for a proposed mission to rendezvous with Halley's Comet.


title: Solar sail

text: In 2018, diffraction was proposed as a related solar sail propulsion mechanism with the advantage of less waste heat.


title: Solar sail

text: The force imparted to a solar sail arises from the momentum of photons. The momentum of a photon or an entire flux is given by Einstein's relation:


title: Solar sail

text: where p is the momentum, E is the energy (of the photon or flux), and c is the speed of light. Specifically, the momentum of a photon depends on its wavelength


title: Solar sail

text: Solar radiation pressure can be related to the irradiance (solar constant) value of 1361 W/m at 1 AU (Earth-Sun distance), as revised in 2011:


title: Solar sail

text: An ideal sail is flat and has 100% specular reflection. An actual sail will have an overall efficiency of about 90%, about 8.17 μN/m, due to curvature (billow), wrinkles, absorbance, re-radiation from front and back, non-specular effects, and other factors.


title: Solar sail

text: The force on a sail and the actual acceleration of the craft vary by the inverse square of distance from the Sun (unless extremely close to the Sun), and by the square of the cosine of the angle between the sail force vector and the radial from the Sun, so


title: Solar sail

text: Note that the force and acceleration approach zero generally around θ = 60° rather than 90° as one might expect with an ideal sail.


title: Solar sail

text: If some of the energy is absorbed, the absorbed energy will heat the sail, which re-radiates that energy from the front and rear surfaces, depending on the emissivity of those two surfaces.


title: Solar sail

text: Solar wind, the flux of charged particles blown out from the Sun, exerts a nominal dynamic pressure of about 3 to 4 nPa, three orders of magnitude less than solar radiation pressure on a reflective sail.


title: Solar sail

text: Sail loading (areal density) is an important parameter, which is the total mass divided by the sail area, expressed in g/m. It is represented by the Greek letter σ (sigma).


title: Solar sail

text: A sail craft has a characteristic acceleration, a, which it would experience at 1 AU when facing the Sun. Note this value accounts for both the incident and reflected momentums. Using the value from above of 9.08 μN per square metre of radiation pressure at 1 AU, a is related to areal density by:


title: Solar sail

text: The lightness number, λ, is the dimensionless ratio of maximum vehicle acceleration divided by the Sun's local gravity. Using the values at 1 AU:


title: Solar sail

text: The lightness number is also independent of distance from the Sun because both gravity and light pressure fall off as the inverse square of the distance from the Sun. Therefore, this number defines the types of orbit maneuvers that are possible for a given vessel.


title: Solar sail

text: The table presents some example values. Payloads are not included. The first two are from the detailed design effort at JPL in the 1970s. The third, the lattice sailer, might represent about the best possible performance level. The dimensions for square and lattice sails are edges. The dimension for heliogyro is blade tip to blade tip.


title: Solar sail

text: An active attitude control system (ACS) is essential for a sail craft to achieve and maintain a desired orientation. The required sail orientation changes slowly (often less than 1 degree per day) in interplanetary space, but much more rapidly in a planetary orbit. The ACS must be capable of meeting these orientation requirements. Attitude control is achieved by a relative shift between the craft's center of pressure and its center of mass. This can be achieved with control vanes, movement of individual sails, movement of a control mass, or altering reflectivity.


title: Solar sail

text: Holding a constant attitude requires that the ACS maintain a net torque of zero on the craft. The total force and torque on a sail, or set of sails, is not constant along a trajectory. The force changes with solar distance and sail angle, which changes the billow in the sail and deflects some elements of the supporting structure, resulting in changes in the sail force and torque.


title: Solar sail

text: Sail temperature also changes with solar distance and sail angle, which changes sail dimensions. The radiant heat from the sail changes the temperature of the supporting structure. Both factors affect total force and torque.


title: Solar sail

text: In Earth orbit, solar pressure and drag pressure are typically equal at an altitude of about 800 km, which means that a sail craft would have to operate above that altitude. Sail craft must operate in orbits where their turn rates are compatible with the orbits, which is generally a concern only for spinning disk configurations.


title: Solar sail

text: Sail operating temperatures are a function of solar distance, sail angle, reflectivity, and front and back emissivities. A sail can be used only where its temperature is kept within its material limits. Generally, a sail can be used rather close to the Sun, around 0.25 AU, or even closer if carefully designed for those conditions.


title: Solar sail

text: Potential applications for sail craft range throughout the Solar System, from near the Sun to the comet clouds beyond Neptune. The craft can make outbound voyages to deliver loads or to take up station keeping at the destination. They can be used to haul cargo and possibly also used for human travel.


title: Solar sail

text: For trips within the inner Solar System, they can deliver payloads and then return to Earth for subsequent voyages, operating as an interplanetary shuttle. For Mars in particular, the craft could provide economical means of routinely supplying operations on the planet according to Jerome Wright, "The cost of launching the necessary conventional propellants from Earth are enormous for manned missions. Use of sailing ships could potentially save more than $10 billion in mission costs."


title: Solar sail

text: Solar sail craft can approach the Sun to deliver observation payloads or to take up station keeping orbits. They can operate at 0.25 AU or closer. They can reach high orbital inclinations, including polar.


title: Solar sail

text: Solar sails can travel to and from all of the inner planets. Trips to Mercury and Venus are for rendezvous and orbit entry for the payload. Trips to Mars could be either for rendezvous or swing-by with release of the payload for aerodynamic braking.


title: Solar sail

text: Minimum transfer times to the outer planets benefit from using an indirect transfer (solar swing-by). However, this method results in high arrival speeds. Slower transfers have lower arrival speeds.


title: Solar sail

text: The minimum transfer time to Jupiter for "a" of 1 mm/s with no departure velocity relative to Earth is 2 years when using an indirect transfer (solar swing-by). The arrival speed ("V") is close to 17 km/s. For Saturn, the minimum trip time is 3.3 years, with an arrival speed of nearly 19 km/s.


title: Solar sail

text: The Sun's inner gravitational focus point lies at minimum distance of 550 AU from the Sun, and is the point to which light from distant objects is focused by gravity as a result of it passing by the Sun. This is thus the distant point to which solar gravity will cause the region of deep space on the other side of the Sun to be focused, thus serving effectively as a very large telescope objective lens.


title: Solar sail

text: It has been proposed that an inflated sail, made of beryllium, that starts at 0.05 AU from the Sun would gain an initial acceleration of 36.4 m/s, and reach a speed of 0.00264c (about 950 km/s) in less than a day. Such proximity to the Sun could prove to be impractical in the near term due to the structural degradation of beryllium at high temperatures, diffusion of hydrogen at high temperatures as well as an electrostatic gradient, generated by the ionization of beryllium from the solar wind, posing a burst risk. A revised perihelion of 0.1 AU would reduce the aforementioned temperature and solar flux exposure.


title: Solar sail

text: Such a sail would take "Two and a half years to reach the heliopause, six and a half years to reach the Sun’s inner gravitational focus, with arrival at the inner Oort Cloud in no more than thirty years." "Such a mission could perform useful astrophysical observations en route, explore gravitational focusing techniques, and image Oort Cloud objects while exploring particles and fields in that region that are of galactic rather than solar origin."


title: Solar sail

text: Robert L. Forward has commented that a solar sail could be used to modify the orbit of a satellite about the Earth. In the limit, a sail could be used to "hover" a satellite above one pole of the Earth. Spacecraft fitted with solar sails could also be placed in close orbits such that they are stationary with respect to either the Sun or the Earth, a type of satellite named by Forward a "statite". This is possible because the propulsion provided by the sail offsets the gravitational attraction of the Sun. Such an orbit could be useful for studying the properties of the Sun for long durations. Likewise a solar sail-equipped spacecraft could also remain on station nearly above the polar solar terminator of a planet such as the Earth by tilting the sail at the appropriate angle needed to counteract the planet's gravity.


title: Solar sail

text: In his book "The Case for Mars", Robert Zubrin points out that the reflected sunlight from a large statite, placed near the polar terminator of the planet Mars, could be focused on one of the Martian polar ice caps to significantly warm the planet's atmosphere. Such a statite could be made from asteroid material.


title: Solar sail

text: The MESSENGER probe orbiting Mercury used light pressure on its solar panels to perform fine trajectory corrections on the way to Mercury. By changing the angle of the solar panels relative to the Sun, the amount of solar radiation pressure was varied to adjust the spacecraft trajectory more delicately than possible with thrusters. Minor errors are greatly amplified by gravity assist maneuvers, so using radiation pressure to make very small corrections saved large amounts of propellant.


title: Solar sail

text: In the 1970s, Robert Forward proposed two beam-powered propulsion schemes using either lasers or masers to push giant sails to a significant fraction of the speed of light.


title: Solar sail

text: In the science fiction novel "Rocheworld", Forward described a light sail propelled by super lasers. As the starship neared its destination, the outer portion of the sail would detach. The outer sail would then refocus and reflect the lasers back onto a smaller, inner sail. This would provide braking thrust to stop the ship in the destination star system.


title: Solar sail

text: Both methods pose monumental engineering challenges. The lasers would have to operate for years continuously at gigawatt strength. Forward's solution to this requires enormous solar panel arrays to be built at or near the planet Mercury. A planet-sized mirror or Fresnel lens would need to be located at several dozen astronomical units from the Sun to keep the lasers focused on the sail. The giant braking sail would have to act as a precision mirror to focus the braking beam onto the inner "deceleration" sail.


title: Solar sail

text: A potentially easier approach would be to use a maser to drive a "solar sail" composed of a mesh of wires with the same spacing as the wavelength of the microwaves directed at the sail, since the manipulation of microwave radiation is somewhat easier than the manipulation of visible light. The hypothetical "Starwisp" interstellar probe design would use microwaves, rather than visible light, to push it. Masers spread out more rapidly than optical lasers owing to their longer wavelength, and so would not have as great an effective range.


title: Solar sail

text: Masers could also be used to power a painted solar sail, a conventional sail coated with a layer of chemicals designed to evaporate when struck by microwave radiation. The momentum generated by this evaporation could significantly increase the thrust generated by solar sails, as a form of lightweight ablative laser propulsion.


title: Solar sail

text: To further focus the energy on a distant solar sail, Forward proposed a lens designed as a large zone plate. This would be placed at a location between the laser or maser and the spacecraft.


title: Solar sail

text: Another more physically realistic approach would be to use the light from the Sun to accelerate the spacecraft. The ship would first drop into an orbit making a close pass to the Sun, to maximize the solar energy input on the sail, then it would begin to accelerate away from the system using the light from the Sun. Acceleration will drop approximately as the inverse square of the distance from the Sun, and beyond some distance, the ship would no longer receive enough light to accelerate it significantly, but would maintain the final velocity attained. When nearing the target star, the ship could turn its sails toward it and begin to use the outward pressure of the destination star to decelerate. Rockets could augment the solar thrust.


title: Solar sail

text: Similar solar sailing launch and capture were suggested for directed panspermia to expand life in other solar system. Velocities of 0.05% the speed of light could be obtained by solar sails carrying 10 kg payloads, using thin solar sail vehicles with effective areal densities of 0.1 g/m with thin sails of 0.1 µm thickness and sizes on the order of one square kilometer. Alternatively, swarms of 1 mm capsules could be launched on solar sails with radii of 42 cm, each carrying 10,000 capsules of a hundred million extremophile microorganisms to seed life in diverse target environments.


title: Solar sail

text: Small solar sails have been proposed to accelerate the deorbiting of small artificial satellites from Earth orbits. Satellites in low Earth orbit can use a combination of solar pressure on the sail and increased atmospheric drag to accelerate satellite reentry. A de-orbit sail developed at Cranfield University is part of the UK satellite TechDemoSat-1, launched in 2014. The sail deployed at the end of the satellite's five-year useful life in May 2019. The sail's purpose is to bring the satellite out of orbit over a period of about 25 years. In July 2015 British 3U CubeSat called DeorbitSail was launched into space with the purpose of testing 16 m deorbit structure, but eventually it failed to deploy it. A student 2U CubeSat mission called PW-Sat2, launched in December 2018 and tested a 4 m deorbit sail. It successfully deorbited in February 2021. In June 2017, a second British 3U CubeSat called InflateSail deployed a 10 m deorbit sail at an altitude of .


title: Solar sail

text: In June 2017 the 3U Cubesat URSAMAIOR has been launched in low Earth orbit to test the deorbiting system ARTICA developed by Spacemind. The device, which occupies only 0.4 U of the cubesat, shall deploy a sail of 2.1 m to deorbit the satellite at the end of the operational life.


title: Solar sail

text: IKAROS, launched in 2010, was the first practical solar sail vehicle. As of 2015, it was still under thrust, proving the practicality of a solar sail for long-duration missions. It is spin-deployed, with tip-masses in the corners of its square sail. The sail is made of thin polyimide film, coated with evaporated aluminium. It steers with electrically controlled liquid crystal panels. The sail slowly spins, and these panels turn on and off to control the attitude of the vehicle. When on, they diffuse light, reducing the momentum transfer to that part of the sail. When off, the sail reflects more light, transferring more momentum. In that way, they turn the sail. Thin-film solar cells are also integrated into the sail, powering the spacecraft. The design is very reliable, because spin deployment, which is preferable for large sails, simplified the mechanisms to unfold the sail and the LCD panels have no moving parts.


title: Solar sail

text: Parachutes have very low mass, but a parachute is not a workable configuration for a solar sail. Analysis shows that a parachute configuration would collapse from the forces exerted by shroud lines, since radiation pressure does not behave like aerodynamic pressure, and would not act to keep the parachute open.


title: Solar sail

text: The highest thrust-to-mass designs for ground-assembled deploy-able structures are square sails with the masts and guy lines on the dark side of the sail. Usually there are four masts that spread the corners of the sail, and a mast in the center to hold guy-wires. One of the largest advantages is that there are no hot spots in the rigging from wrinkling or bagging, and the sail protects the structure from the Sun. This form can, therefore, go close to the Sun for maximum thrust. Most designs steer with small moving sails on the ends of the spars.


title: Solar sail

text: In the 1970s JPL studied many rotating blade and ring sails for a mission to rendezvous with Halley's Comet. The intention was to stiffen the structures using angular momentum, eliminating the need for struts, and saving mass. In all cases, surprisingly large amounts of tensile strength were needed to cope with dynamic loads. Weaker sails would ripple or oscillate when the sail's attitude changed, and the oscillations would add and cause structural failure. The difference in the thrust-to-mass ratio between practical designs was almost nil, and the static designs were easier to control.


title: Solar sail

text: JPL's reference design was called the "heliogyro". It had plastic-film blades deployed from rollers and held out by centrifugal forces as it rotated. The spacecraft's attitude and direction were to be completely controlled by changing the angle of the blades in various ways, similar to the cyclic and collective pitch of a helicopter. Although the design had no mass advantage over a square sail, it remained attractive because the method of deploying the sail was simpler than a strut-based design. The CubeSail (UltraSail) is an active project aiming to deploy a heliogyro sail.


title: Solar sail

text: Heliogyro design is similar to the blades on a helicopter. The design is faster to manufacture due to lightweight centrifugal stiffening of sails. Also, they are highly efficient in cost and velocity because the blades are lightweight and long. Unlike the square and spinning disk designs, heliogyro is easier to deploy because the blades are compacted on a reel. The blades roll out when they are deploying after the ejection from the spacecraft. As the heliogyro travels through space the system spins around because of the centrifugal acceleration. Finally, payloads for the space flights are placed in the center of gravity to even out the distribution of weight to ensure stable flight.


title: Solar sail

text: JPL also investigated "ring sails" (Spinning Disk Sail in the above diagram), panels attached to the edge of a rotating spacecraft. The panels would have slight gaps, about one to five percent of the total area. Lines would connect the edge of one sail to the other. Masses in the middles of these lines would pull the sails taut against the coning caused by the radiation pressure. JPL researchers said that this might be an attractive sail design for large crewed structures. The inner ring, in particular, might be made to have artificial gravity roughly equal to the gravity on the surface of Mars.


title: Solar sail

text: A solar sail can serve a dual function as a high-gain antenna. Designs differ, but most modify the metalization pattern to create a holographic monochromatic lens or mirror in the radio frequencies of interest, including visible light.


title: Solar sail

text: Pekka Janhunen from FMI has proposed a type of solar sail called the electric solar wind sail. Mechanically it has little in common with the traditional solar sail design. The sails are replaced with straightened conducting tethers (wires) placed radially around the host ship. The wires are electrically charged to create an electric field around the wires. The electric field extends a few tens of metres into the plasma of the surrounding solar wind. The solar electrons are reflected by the electric field (like the photons on a traditional solar sail). The radius of the sail is from the electric field rather than the actual wire itself, making the sail lighter. The craft can also be steered by regulating the electric charge of the wires. A practical electric sail would have 50–100 straightened wires with a length of about 20 km each.


title: Solar sail

text: A magnetic sail would also employ the solar wind. However, the magnetic field deflects the electrically charged particles in the wind. It uses wire loops, and runs a static current through them instead of applying a static voltage.


title: Solar sail

text: Magnetic sails bend the path of the charged protons that are in the solar wind. By changing the sails' attitudes, and the size of the magnetic fields, they can change the amount and direction of the thrust.


title: Solar sail

text: The most common material in current designs is a thin layer of aluminum coating on a polymer (plastic) sheet, such as aluminized 2 µm Kapton film. The polymer provides mechanical support as well as flexibility, while the thin metal layer provides the reflectivity. Such material resists the heat of a pass close to the Sun and still remains reasonably strong. The aluminum reflecting film is on the Sun side. The sails of "Cosmos 1" were made of aluminized PET film (Mylar).


title: Solar sail

text: Eric Drexler developed a concept for a sail in which the polymer was removed. He proposed very high thrust-to-mass solar sails, and made prototypes of the sail material. His sail would use panels of thin aluminium film (30 to 100 nanometres thick) supported by a tensile structure. The sail would rotate and would have to be continually under thrust. He made and handled samples of the film in the laboratory, but the material was too delicate to survive folding, launch, and deployment. The design planned to rely on space-based production of the film panels, joining them to a deploy-able tension structure. Sails in this class would offer high area per unit mass and hence accelerations up to "fifty times higher" than designs based on deploy-able plastic films.


title: Solar sail

text: The material developed for the Drexler solar sail was a thin aluminium film with a baseline thickness of 0.1 µm, to be fabricated by vapor deposition in a space-based system. Drexler used a similar process to prepare films on the ground. As anticipated, these films demonstrated adequate strength and robustness for handling in the laboratory and for use in space, but not for folding, launch, and deployment.


title: Solar sail

text: Research by Geoffrey Landis in 1998–1999, funded by the NASA Institute for Advanced Concepts, showed that various materials such as alumina for laser lightsails and carbon fiber for microwave pushed lightsails were superior sail materials to the previously standard aluminium or Kapton films.


title: Solar sail

text: In 2000, Energy Science Laboratories developed a new carbon fiber material that might be useful for solar sails. The material is over 200 times thicker than conventional solar sail designs, but it is so porous that it has the same mass. The rigidity and durability of this material could make solar sails that are significantly sturdier than plastic films. The material could self-deploy and should withstand higher temperatures.


title: Solar sail

text: There has been some theoretical speculation about using molecular manufacturing techniques to create advanced, strong, hyper-light sail material, based on nanotube mesh weaves, where the weave "spaces" are less than half the wavelength of light impinging on the sail. While such materials have so far only been produced in laboratory conditions, and the means for manufacturing such material on an industrial scale are not yet available, such materials could mass less than 0.1 g/m, making them lighter than any current sail material by a factor of at least 30. For comparison, 5 micrometre thick Mylar sail material mass 7 g/m, aluminized Kapton films have a mass as much as 12 g/m, and Energy Science Laboratories' new carbon fiber material masses 3 g/m.


title: Solar sail

text: The least dense metal is lithium, about 5 times less dense than aluminium. Fresh, unoxidized surfaces are reflective. At a thickness of 20 nm, lithium has an area density of 0.011 g/m. A high-performance sail could be made of lithium alone at 20 nm (no emission layer). It would have to be fabricated in space and not used to approach the Sun. In the limit, a sail craft might be constructed with a total areal density of around 0.02 g/m, giving it a lightness number of 67 and a of about 400 mm/s. Magnesium and beryllium are also potential materials for high-performance sails. These 3 metals can be alloyed with each other and with aluminium.


title: Solar sail

text: Aluminium is the common choice for the reflection layer. It typically has a thickness of at least 20 nm, with a reflectivity of 0.88 to 0.90. Chromium is a good choice for the emission layer on the face away from the Sun. It can readily provide emissivity values of 0.63 to 0.73 for thicknesses from 5 to 20 nm on plastic film. Usable emissivity values are empirical because thin-film effects dominate; bulk emissivity values do not hold up in these cases because material thickness is much thinner than the emitted wavelengths.


title: Solar sail

text: Sails are fabricated on Earth on long tables where ribbons are unrolled and joined to create the sails. Sail material needed to have as little weight as possible because it would require the use of the shuttle to carry the craft into orbit. Thus, these sails are packed, launched, and unfurled in space.


title: Solar sail

text: In the future, fabrication could take place in orbit inside large frames that support the sail. This would result in lower mass sails and elimination of the risk of deployment failure.


title: Solar sail

text: Sailing operations are simplest in interplanetary orbits, where altitude changes are done at low rates. For outward bound trajectories, the sail force vector is oriented forward of the Sun line, which increases orbital energy and angular momentum, resulting in the craft moving farther from the Sun. For inward trajectories, the sail force vector is oriented behind the Sun line, which decreases orbital energy and angular momentum, resulting in the craft moving in toward the Sun. It is worth noting that only the Sun's gravity pulls the craft toward the Sun—there is no analog to a sailboat's tacking to windward. To change orbital inclination, the force vector is turned out of the plane of the velocity vector.


title: Solar sail

text: In orbits around planets or other bodies, the sail is oriented so that its force vector has a component along the velocity vector, either in the direction of motion for an outward spiral, or against the direction of motion for an inward spiral.


title: Solar sail

text: Trajectory optimizations can often require intervals of reduced or zero thrust. This can be achieved by rolling the craft around the Sun line with the sail set at an appropriate angle to reduce or remove the thrust.


title: Solar sail

text: A close solar passage can be used to increase a craft's energy. The increased radiation pressure combines with the efficacy of being deep in the Sun's gravity well to substantially increase the energy for runs to the outer Solar System. The optimal approach to the Sun is done by increasing the orbital eccentricity while keeping the energy level as high as practical. The minimum approach distance is a function of sail angle, thermal properties of the sail and other structure, load effects on structure, and sail optical characteristics (reflectivity and emissivity). A close passage can result in substantial optical degradation. Required turn rates can increase substantially for a close passage. A sail craft arriving at a star can use a close passage to reduce energy, which also applies to a sail craft on a return trip from the outer Solar System.


title: Solar sail

text: A lunar swing-by can have important benefits for trajectories leaving from or arriving at Earth. This can reduce trip times, especially in cases where the sail is heavily loaded. A swing-by can also be used to obtain favorable departure or arrival directions relative to Earth.


title: Solar sail

text: A planetary swing-by could also be employed similar to what is done with coasting spacecraft, but good alignments might not exist due to the requirements for overall optimization of the trajectory.


title: Solar sail

text: The following table lists some example concepts using beamed laser propulsion as proposed by the physicist Robert L. Forward:


title: Solar sail

text: Both the Mariner 10 mission, which flew by the planets Mercury and Venus, and the MESSENGER mission to Mercury demonstrated the use of solar pressure as a method of attitude control in order to conserve attitude-control propellant.


title: Solar sail

text: Hayabusa also used solar pressure on its solar paddles as a method of attitude control to compensate for broken reaction wheels and chemical thruster.


title: Solar sail

text: MTSAT-1R (Multi-Functional Transport Satellite)'s solar sail counteracts the torque produced by sunlight pressure on the solar array. The trim tab on the solar array makes small adjustments to the torque balance.


title: Solar sail

text: A joint private project between Planetary Society, Cosmos Studios and Russian Academy of Science in 2001 made a suborbital prototype test, which failed because of rocket failure.


title: Solar sail

text: A 15-meter-diameter solar sail (SSP, solar sail sub payload, "soraseiru sabupeiro-do") was launched together with ASTRO-F on a M-V rocket on February 21, 2006, and made it to orbit. It deployed from the stage, but opened incompletely.


title: Solar sail

text: On August 9, 2004, the Japanese ISAS successfully deployed two prototype solar sails from a sounding rocket. A clover-shaped sail was deployed at 122 km altitude and a fan-shaped sail was deployed at 169 km altitude. Both sails used 7.5-micrometer film. The experiment purely tested the deployment mechanisms, not propulsion.


title: Solar sail

text: On February 4, 1993, the Znamya 2, a 20-meter wide aluminized-mylar reflector, was successfully deployed from the Russian Mir space station. It was the first thin film reflector of such type successfully deployed in space using the mechanism based on centrifugal force. Although the deployment succeeded, propulsion was not demonstrated. A second test in 1999, Znamya 2.5, failed to deploy properly.


title: Solar sail

text: On 21 May 2010, Japan Aerospace Exploration Agency (JAXA) launched the world's first interplanetary solar sail spacecraft "IKAROS" (Interplanetary Kite-craft Accelerated by Radiation Of the Sun) to Venus. Using a new solar-photon propulsion method, it was the first true solar sail spacecraft fully propelled by sunlight, and was the first spacecraft to succeed in solar sail flight.


title: Solar sail

text: JAXA successfully tested IKAROS in 2010. The goal was to deploy and control the sail and, for the first time, to determine the minute orbit perturbations caused by light pressure. Orbit determination was done by the nearby AKATSUKI probe from which IKAROS detached after both had been brought into a transfer orbit to Venus. The total effect over the six month flight was 100 m/s.


title: Solar sail

text: Until 2010, no solar sails had been successfully used in space as primary propulsion systems. On 21 May 2010, the Japan Aerospace Exploration Agency (JAXA) launched the IKAROS spacecraft, which deployed a 200 m polyimide experimental solar sail on June 10.<ref name="jaxa.jp/press/2010/06/20100611_ikaros_e"></ref> In July, the next phase for the demonstration of acceleration by radiation began. On 9 July 2010, it was verified that IKAROS collected radiation from the Sun and began photon acceleration by the orbit determination of IKAROS by range-and-range-rate (RARR) that is newly calculated in addition to the data of the relativization accelerating speed of IKAROS between IKAROS and the Earth that has been taken since before the Doppler effect was utilized.<ref name="http://www.jaxa.jp/press/2010/07/20100709_ikaros_j.html"></ref> The data showed that IKAROS appears to have been solar-sailing since 3 June when it deployed the sail.


title: Solar sail

text: IKAROS has a diagonal spinning square sail 14×14 m (196 m) made of a thick sheet of polyimide. The polyimide sheet had a mass of about 10 grams per square metre. A thin-film solar array is embedded in the sail. Eight LCD panels are embedded in the sail, whose reflectance can be adjusted for attitude control. IKAROS spent six months traveling to Venus, and then began a three-year journey to the far side of the Sun.


title: Solar sail

text: A team from the NASA Marshall Space Flight Center (Marshall), along with a team from the NASA Ames Research Center, developed a solar sail mission called NanoSail-D, which was lost in a launch failure aboard a Falcon 1 rocket on 3 August 2008. The second backup version, NanoSail-D2, also sometimes called simply NanoSail-D, was launched with FASTSAT on a Minotaur IV on November 19, 2010, becoming NASA's first solar sail deployed in low earth orbit. The objectives of the mission were to test sail deployment technologies, and to gather data about the use of solar sails as a simple, "passive" means of de-orbiting dead satellites and space debris. The NanoSail-D structure was made of aluminium and plastic, with the spacecraft massing less than . The sail has about of light-catching surface. After some initial problems with deployment, the solar sail was deployed and over the course of its 240-day mission reportedly produced a "wealth of data" concerning the use of solar sails as passive deorbit devices.


title: Solar sail

text: NASA launched the second NanoSail-D unit stowed inside the FASTSAT satellite on the Minotaur IV on November 19, 2010. The ejection date from the FASTSAT microsatellite was planned for December 6, 2010, but deployment only occurred on January 20, 2011.


title: Solar sail

text: On June 21, 2005, a joint private project between Planetary Society, Cosmos Studios and Russian Academy of Science launched a prototype sail "Cosmos 1" from a submarine in the Barents Sea, but the Volna rocket failed, and the spacecraft failed to reach orbit. They intended to use the sail to gradually raise the spacecraft to a higher Earth orbit over a mission duration of one month. The launch attempt sparked public interest according to Louis Friedman. Despite the failed launch attempt of Cosmos 1, The Planetary Society received applause for their efforts from the space community and sparked a rekindled interest in solar sail technology.


title: Solar sail

text: On Carl Sagan's 75th birthday (November 9, 2009) the Planetary Society announced plans to make three further attempts, dubbed LightSail-1, -2, and -3. The new design will use a 32 m Mylar sail, deployed in four triangular segments like NanoSail-D. The launch configuration is a 3U CubeSat format, and as of 2015, it was scheduled as a secondary payload for a 2016 launch on the first SpaceX Falcon Heavy launch.


title: Solar sail

text: "LightSail-1" was launched on 20 May 2015. The purpose of the test was to allow a full checkout of the satellite's systems in advance of LightSail-2. Its deployment orbit was not high enough to escape Earth's atmospheric drag and demonstrate true solar sailing.


title: Solar sail

text: "LightSail-2" was launched on 25 June 2019, and deployed into a much higher low Earth orbit. Its solar sails were deployed on 23 July 2019.


title: Solar sail

text: Despite the losses of "Cosmos 1" and NanoSail-D (which were due to failure of their launchers), scientists and engineers around the world remain encouraged and continue to work on solar sails. While most direct applications created so far intend to use the sails as inexpensive modes of cargo transport, some scientists are investigating the possibility of using solar sails as a means of transporting humans. This goal is strongly related to the management of very large (i.e. well above 1 km) surfaces in space and the sail making advancements. Development of solar sails for crewed space flight is still in its infancy.


title: Solar sail

text: A technology demonstration sail craft, dubbed "Sunjammer", was in development with the intent to prove the viability and value of sailing technology. "Sunjammer" had a square sail, 124 feet (38 meters) wide on each side (total area 13,000 sq ft or 1,208 sq m). It would have traveled from the Sun-Earth Lagrangian point 900,000 miles from Earth (1.5 million km) to a distance of 1,864,114 miles (3 million kilometers). The demonstration was expected to launch on a Falcon 9 in January 2015. It would have been a secondary payload, released after the placement of the DSCOVR climate satellite at the L1 point. Citing a lack of confidence in the ability of its contractor L'Garde to deliver, the mission was cancelled in October 2014.


title: Solar sail

text: , the European Space Agency (ESA) has a proposed deorbit sail, named ""Gossamer"", that would be intended to be used to accelerate the deorbiting of small (less than ) artificial satellites from low Earth orbits. The launch mass is with a launch volume of only . Once deployed, the sail would expand to and would use a combination of solar pressure on the sail and increased atmospheric drag to accelerate satellite reentry.


title: Solar sail

text: The Near-Earth Asteroid Scout (NEA Scout) was a mission jointly developed by NASA's Marshall Space Flight Center (MSFC) and the Jet Propulsion Laboratory (JPL), consisting of a controllable low-cost CubeSat solar sail spacecraft capable of encountering near-Earth asteroids (NEA). Four booms would deploy, unfurling the aluminized polyimide solar sail. In 2015, NASA announced it had selected NEA Scout to launch as one of several secondary payloads aboard Artemis 1, the first flight of the agency's heavy-lift SLS launch vehicle.


title: Solar sail

text: OKEANOS (Outsized Kite-craft for Exploration and Astronautics in the Outer Solar System) was a proposed mission concept by Japan's JAXA to Jupiter's Trojan asteroids using a hybrid solar sail for propulsion; the sail would have been covered with thin solar panels to power an ion engine. "In-situ" analysis of the collected samples would have been performed by either direct contact or using a lander carrying a high-resolution mass spectrometer. A lander and a sample-return to Earth were options under study. The OKEANOS Jupiter Trojan Asteroid Explorer was a finalist for Japan's ISAS 2nd Large-class mission to be launched in the late 2020s. However, it was not selected.


title: Solar sail

text: The well-funded Breakthrough Starshot project announced on April 12, 2016, aims to develop a fleet of 1000 light sail nanocraft carrying miniature cameras, propelled by ground-based lasers and send them to Alpha Centauri at 20% the speed of light. The trip would take 20 years.


title: Solar sail

text: In August 2019, NASA awarded the "Solar Cruiser" team $400,000 for nine-month mission concept studies. The spacecraft would have a solar sail and would orbit the Sun in a polar orbit, while the coronagraph instrument would enable simultaneous measurements of the Sun's magnetic field structure and velocity of coronal mass ejections. If selected for development, it would launch in 2024.


title: Solar sail

text: Cordwainer Smith gives a description of solar-sail-powered spaceships in "The Lady Who Sailed The Soul", published first in April 1960.


title: Solar sail

text: Jack Vance wrote a short story about a training mission on a solar-sail-powered spaceship in "Sail 25", published in 1961.


title: Solar sail

text: Arthur C. Clarke and Poul Anderson (writing as Winston P. Sanders) independently published stories featuring solar sails, both stories titled "Sunjammer," in 1964. Clarke retitled his story "The Wind from the Sun" when it was reprinted, in order to avoid confusion.


title: Solar sail

text: In Larry Niven and Jerry Pournelle's 1974 novel "The Mote in God's Eye", aliens are discovered when their laser-sail propelled probe enters human space.


title: Solar sail

text: A similar technology was the theme in the "" episode "". In the episode, Lightships are described as an ancient technology used by Bajorans to travel beyond their solar system by using light from the Bajoran sun and specially constructed sails to propel them through space ().


title: Solar sail

text: In the 2002 "Star Wars" film "Attack of the Clones", the main villain Count Dooku was seen using a spacecraft with solar sails.


title: Solar sail

text: In the third season of Apple TV+'s alternate history TV show "For All Mankind", the fictional NASA spaceship Sojourner 1 utilises solar sails for additional propulsion on its way to Mars.


title: 1999 Bridge Creek–Moore tornado

text: On the evening of Monday, May 3, 1999, a large and extremely powerful F5 tornado registered the highest wind speeds ever measured globally; winds were recorded at by a Doppler on Wheels (DOW) radar. Considered the strongest tornado ever recorded to have affected the metropolitan area, the tornado devastated southern portions of Oklahoma City, Oklahoma, along with surrounding suburbs and towns to the south and southwest. The tornado covered during its 85-minute existence, destroying thousands of homes, killing 36 people (plus an additional five indirectly), and leaving US$1 billion (1999 USD) in damage, ranking it as the fifth-costliest on record not accounting for inflation. It was the first use of the tornado emergency statement by the National Weather Service.


title: 1999 Bridge Creek–Moore tornado

text: The tornado first touched down at 6:23 p.m. Central Daylight Time (CDT) in Grady County, roughly south-southwest of the town of Amber. It quickly intensified into a violent F4, and gradually reached F5 status after traveling , at which time it struck the town of Bridge Creek. It fluctuated in strength, ranging from F2 to F5 status before it crossed into Cleveland County where it reached F5 intensity for a third time shortly before entering the city of Moore. By 7:30 pm, the tornado crossed into Oklahoma County and battered southeastern Oklahoma City, Del City, and Midwest City before dissipating around 7:48 p.m. just outside Midwest City. A total of 8,132 homes, 1,041 apartments, 260 businesses, eleven public buildings, and seven churches were damaged or destroyed.


title: 1999 Bridge Creek–Moore tornado

text: Large-scale search and rescue operations immediately took place in the affected areas. A major disaster declaration was signed by President Bill Clinton the following day (May 4) allowing the state to receive federal aid. In the following months, disaster aid amounted to $67.8 million. Reconstruction projects in subsequent years led to a safer, tornado-ready community. However, on May 20, 2013, nearby areas adjacent to the 1999 storm's track along with some of the same areas in the path of the tornado were again devastated by another large and violent EF5 tornado, resulting in 24 fatalities and extreme damage in the South Oklahoma City/Moore area.


title: 1999 Bridge Creek–Moore tornado

text: The Bridge Creek–Moore tornado was part of a much larger outbreak which produced 71 tornadoes across five states throughout the Central Plains on May 3 alone, along with an additional 25 that touched down a day later in some of the areas affected by the previous day's activity (some of which were spawned by supercells that developed on the evening of May 3), stretching eastward to the Mississippi River Valley. The most prolific tornadic activity associated with the May 3 outbreak – and the multi-day outbreak as a whole – occurred in Oklahoma; 14 of the 66 tornadoes that occurred within the state that afternoon and evening produced damage consistent with the Fujita scale's "strong" (F2–F3) and "violent" (F4–F5) categories, which, in addition to the areas struck by the Bridge Creek–Moore tornado family, affected towns such as Mulhall, Cimarron City, Dover, Choctaw and Stroud.


title: 1999 Bridge Creek–Moore tornado

text: On the morning of May 3, in its Day 1 Convective Outlook for the United States, the Storm Prediction Center (SPC) – based in Norman, approximately south of the tornado's eventual damage path – issued a slight risk of severe thunderstorms from southern Nebraska to central Texas. SPC analysis had detected the presence of a dry line that stretched from western Kansas into western Texas that was approaching a warm, humid air-mass over the Central Plains; the condition ahead of the dry line and a connecting trough positioned over northeastern Colorado appeared to favor the development of thunderstorms later that day that would contain large hail, damaging straight-line winds, and isolated tornadoes.


title: 1999 Bridge Creek–Moore tornado

text: SPC forecasters initially underestimated the atmospheric conditions that would support tornadic development that afternoon and evening. Around 4:00 a.m. CDT that morning, Doppler radar and wind profile data indicated a streak of elevated jet stream winds along the California−Nevada border, though weather balloon soundings sent up the previous evening by National Weather Service (NWS) offices in the western U.S. and numerical computer model data failed to detect the fast-moving air current as it moved ashore from the Pacific Ocean. In addition, the dry line was diffused, with surface winds behind and ahead of the boundary moving into the region from a southerly direction. SPC meteorologists began to recalculate model data during the morning to account for the stronger wind profiles caused by the jet streak; the data acknowledged that thunderstorms would occur within the Central Plains, but disagreed on the exact area of greatest severe weather risk.


title: 1999 Bridge Creek–Moore tornado

text: By 7:00 a.m. CDT, CAPE (convective available potential energy) values began exceeding 4,000 J/kg, an extreme value well above the climatological threshold favoring the development of severe thunderstorms. Despite conflicting model data on the specified area where thunderstorms would develop, the newly available information that denoted a more favorable severe thunderstorm setup in that part of the state prompted the SPC to upgrade the forecasted threat of severe weather to a moderate risk for south-central Kansas, much of the western two-thirds of Oklahoma, and the northwestern and north-central portions of Texas at 11:15 a.m. CDT that morning, which now indicated that the atmospheric conditions present would "provide sufficient shear for a few strong or violent tornadic supercells given the abundant low level moisture and the high instability." The increasing threat of a severe weather/tornado outbreak for late that afternoon into the evening was reemphasized by NWS Norman forecasters in a Thunderstorm Outlook issued by the office at 12:30 p.m. CDT.


title: 1999 Bridge Creek–Moore tornado

text: By the early afternoon hours, forecasters at both the SPC and NWS Norman (both of which shared an office complex near Max Westheimer Airport at the time), realized that a major event was likely to take place based solely on observational data from radar and weather satellite imagery and balloon soundings, as the computer models remained uncooperative in helping meteorologists determine where the greatest threat of severe storms would occur.


title: 1999 Bridge Creek–Moore tornado

text: Conditions became highly conducive for tornadic development by 1:00 p.m. CDT as wind shear intensified over the region (as confirmed by an unscheduled balloon sounding flight conducted by the NWS Norman office), creating a highly unstable atmosphere. The sounding balloon recorded winds blowing southwesterly at and respectively at the surface and at the level, southerly winds of and westerly winds of at ; it also indicated that a capping inversion over the region was weakening in southwestern Oklahoma and north Texas. With the warm air above the surface cooling down, this allowed warm air at the surface the chance to rise and potentially create thunderstorms. Although cirrus clouds − a bank of which had developed in west Texas and overspread portions of Oklahoma later in the morning − were present through much of the day, an area of clearing skies over western north Texas and southwestern Oklahoma early that afternoon allowed for the sun to heat up the moisture-laden region, creating significant atmospheric instability.


title: 1999 Bridge Creek–Moore tornado

text: At 3:49 p.m. CDT, the SPC − having gathered enough data to surmise that there was a credible threat of a significant severe weather outbreak occurring within the next few hours − amended its Day 1 Convective Outlook to place the western nine-tenths of the main body of Oklahoma, central and south-central Kansas and the northern two-thirds of Texas under a high severe weather risk, denoting a higher than normal probability of strong (F2+) tornadoes within the risk area. About 40 minutes after the revised outlook's issuance, at 4:30 p.m. CDT, the SPC issued a tornado watch for western and central Oklahoma, effective from 4:45 p.m. until 10:00 p.m. CDT that evening, for the threat of tornadoes, hail up to in diameter, wind gusts to and intense lightning. As that happened, the first thunderstorm cell of the unfolding event had already formed over southwestern Oklahoma.


title: 1999 Bridge Creek–Moore tornado

text: The thunderstorm that eventually produced the F5 tornado began developing around 3:20 p.m. CDT that afternoon over northeastern Tillman County (southwest of Faxon). Despite the lack of overall lift prevalent in the region, the storm formed out of a contrail-like horizontal area of convective clouds that developed during peak surface heating over southwestern Oklahoma, located well ahead of the dry line that was still positioned farther to the west, which provided enhanced lift and speed shear necessary to develop the supercell. Tracking northeast, the storm strengthened and entered Comanche County shortly after 4:00 p.m. CDT. By 4:15 p.m. CDT, the NWS Norman office issued a severe thunderstorm warning for Comanche County, as the initial storm continued to rapidly intensify over the southern half of the county; there, hail up to in diameter fell.


title: 1999 Bridge Creek–Moore tornado

text: As the supercell's mesocyclonic rotation began to rapidly strengthen at the cloud base, a tornado warning was issued for the counties of Comanche, Caddo, and Grady at 4:50 p.m. CDT; one minute later, a small tornado roughly in diameter − the first of fourteen associated with supercell "A" (NWS Norman designated lettered names for the three tornado-producing supercells in the outbreak in storm surveys) − touched down east-northeast of Medicine Park along U.S. Route 62. Five more tornadoes developed as the storm continued northeast; a sixth one, which would be given an F3 rating, touched down a short time later and caused substantial damage in central Grady County, including some to the Chickasha Municipal Airport, where roofs were torn off of two hangars.


title: 1999 Bridge Creek–Moore tornado

text: At 6:23 p.m. CDT, a ninth tornado associated with supercell "A" touched down about south-southwest of Amber. The tornado quickly intensified in both strength and size as it crossed Oklahoma State Highway 92, attaining F4 strength about east-northeast of Amber. It quickly became a wedge tornado, varying between in width at various points throughout the track. Damage consistent with this rating was sustained over the following of the path before striking Bridge Creek. There, it attained the highest-possible rating on the Fujita Scale, F5. A mobile Doppler weather radar recorded winds of within the tornado at Bridge Creek, the highest wind speed ever recorded on Earth. Since the record for maximum winds are reported from only non-tornadic events, however, the wind gust from Cyclone Olivia in 1996 retained the title.


title: 1999 Bridge Creek–Moore tornado

text: Damage in Bridge Creek was extreme, as many homes were swept away completely, leaving only concrete slabs where the structures once stood. Damage surveyors noted that the remaining structural debris from some of the homes in this area was finely granulated into small fragments, and that trees and shrubs were completely debarked. A few of these homes were bolted to their foundations. Approximately 200 houses and mobile homes were destroyed, and hundreds of other structures were damaged. The Ridgecrest Baptist Church in Bridge Creek was also destroyed in the process. Extensive ground scouring occurred, and vehicles were thrown hundreds of yards from where they originated, including a mangled pickup truck that was found wrapped around a telephone pole. About of asphalt was scoured off one road.


title: 1999 Bridge Creek–Moore tornado

text: About twelve people died in Bridge Creek, nine of whom were in mobile homes; all fatalities and the majority of injuries were concentrated in the Willow Lake and Southern Hills Additions and Bridge Creek Estates, consisting mostly of mobile homes. Over 39 people were injured in the area as well. Continuing northeastward, the tornado briefly weakened to F4 status before re-strengthening to F5 intensity as it neared the Grady-McClain County line, where a car was thrown roughly in the air, and a well-built home with anchor bolts was reduced to a bare slab. At this time, it had attained a width of , having grown to its largest width after crossing the South Canadian River into the southern Oklahoma City limits. The tornado then became quickly rain-wrapped; Jim Gardner, then-helicopter pilot for KFOR-TV, reported during the station's live coverage of the storm that the tornado was at least one mile wide, and was embedded (or "rain-wrapped") in the precipitation core associated with the main circulation, making it difficult to see.


title: 1999 Bridge Creek–Moore tornado

text: As it was becoming clear that a particularly violent tornado was moving into some of the most densely populated areas of central Oklahoma, around 6:57 p.m. CDT, NWS Norman issued the first-ever tornado emergency for southern portions of the Oklahoma City metropolitan area. David Andra, a meteorologist at the NWS Norman office, said that, in drafting the enhanced warning, he wanted to "paint the picture [to residents in the areas that were to be affected by the storm] that a rare and deadly tornado was imminent in the metro area." For its initial usage, the enhanced wording was released as part of a standalone Severe Weather Statement (NWS code: SVS), which were (and still are) normally meant to update the public on an existing tornado warning or severe thunderstorm warning. For tornado warnings, the SVS provides updated information on the approximate location of the storm's base-level rotation or, if it occurred after the initial warning was issued, a tornado reported by the public, civil defense personnel or storm spotters, or with the later advent of dual-polarization radar in the early 2010s, verified by radar-detected debris signatures. (In future issuances, tornado emergencies were issued within either the initial tornado warning issuance or an SVS providing updated information on a tornado warning already in effect.) Two minutes later, at 6:59 p.m. CDT, the SPC issued a Particularly Dangerous Situation tornado watch for much of the central third of Oklahoma, effective from 7:15 p.m. until midnight CDT on the early morning of May 4; the SPC watch product discussion noted that the extreme instability compensated for "somewhat marginal" wind shear to enhance the threat of strong to violent tornadoes.


title: 1999 Bridge Creek–Moore tornado

text: Paralleling Interstate 44, the tornado moved into McClain County, where it crossed the highway twice at F4 intensity, killing a woman who was blown out from an underpass where she was attempting to seek shelter after being dragged down the embankment by the intense channeling winds; her 11-year-old son − with whom the woman vacated their stalled car nearby − survived, staying held tight onto the steel girders of the overpass. A man who helped the mother and son up the overpass suffered severe injuries to his leg, which was partially sliced by a highway sign thrown by the winds. At 7:10 p.m. CDT, a satellite tornado touched down over an open field north of Newcastle; it was rated as an F0 due to lack of damage. In McClain County, 38 homes and two businesses were destroyed and 40 homes, some of which were leveled at F4 intensity, were flattened; seventeen people were injured.


title: 1999 Bridge Creek–Moore tornado

text: After crossing the Canadian River, the tornado entered Cleveland County and weakened to F2 intensity. By this time, it had entered the south side of Oklahoma City. Several minutes after entering the county, it re-attained F4 status, and then moved directly into the city of Moore, reaching F5 intensity for a third time. Some of the most severe damage took place in Cleveland County, mainly in Moore, where eleven people were killed and 293 others were injured. The tornado caused an estimated $450 million in damage across the county. The first area impacted in Moore was the Country Place Estates subdivision, where 50 homes were destroyed and one was swept cleanly from its foundation at F5 intensity. Several vehicles were picked up and tossed nearly away from their previous location. According to local police, an airplane wing, believed to have been from an airport in Grady County (possibly lofted into the storm's updraft when the supercell's sixth tornado hit Chickasha Municipal Airport), was found near Country Place Estates. Then, the powerful tornado struck the densely populated Greenbriar Eastlake Estates at F5 intensity, killing three people and reducing entire rows of homes to rubble. In one instance, four adjacent homes were completely destroyed, with only concrete slabs remaining, warranting an F5 rating at that location. Three other homes in this housing division also received F5 damage, with the remaining destruction rated high-end F4. Severe debarking of trees was noted in this area. At the Emerald Springs Apartments, three more people were killed and a two-story apartment building was mostly flattened.


title: 1999 Bridge Creek–Moore tornado

text: As the tornado entered Cleveland County, NWS Norman activated emergency procedures, preparing to evacuate staff and others present at the facility in the event that the supercell should turn right, placing areas surrounding the Norman campus in the tornado's path (under NOAA protocol in situations posing a danger to personnel at local Weather Forecast Offices and related guidance centers, responsibility over the issuance of warnings and statements on the unfolding outbreak would have been transferred to the nearest NWS Forecast Office, based in Tulsa, while the SPC's forecasting responsibilities would be turned over to the 557th Weather Wing at Offutt Air Force Base). The supercell, however, continued on a northeastward track, sparing the Norman area.


title: 1999 Bridge Creek–Moore tornado

text: Safety precautions were also enacted elsewhere in and near the storm's path; council members and citizens at Moore City Hall − where a council meeting was scheduled to be held that evening − sheltered in place in the building's first-floor restrooms, away from the multiple large-pane windows at its facade. In downtown Oklahoma City, spectators attending sporting events held that evening involving two of the city's minor league teams – a regular season Pacific Coast League baseball game between the Oklahoma RedHawks and the Memphis Redbirds (which was suspended during the second inning) and Game 2 of the Ray Miron President's Cup series between the Central Hockey League's Oklahoma City Blazers and Huntsville Channel Cats – were also evacuated to shelter in an underground storage area connected to the Southwestern Bell Bricktown Ballpark and Myriad Convention Center amid concerns that the storm would jog northward and place Oklahoma City itself in the tornado's path. Flights were grounded at Will Rogers World Airport as the northern edge of the supercell (containing hail up to , straight-line wind gusts up to , and moderate to heavy rain) approached the area; the tornado turned right, away from southwestern parts of the city proper located within Oklahoma County, shortly before airport officials began evacuating employees and visitors at the terminals. Traffic on Interstate 35 in south Oklahoma City and north Moore became backed up for several miles, as drivers evacuated from their vehicles to seek shelter under an overpass overlooking South Shields Boulevard.


title: 1999 Bridge Creek–Moore tornado

text: Just outside the Eastlake Estates, an honors ceremony was being held at Westmoore High School at the time of the tornado. Adequate warning time allowed those at the school to seek shelter, however, and more than 400 adults and students attending the awards ceremony at the school's auditorium were moved to the main building, sheltering in reinforced hallways and bathrooms. Ultimately, Westmoore High sustained heavy damage and dozens of cars that were in the school's parking lot were tossed around, some of which were completely destroyed or thrown into nearby homes. No injuries took place at the school, though a horse was found dead between a couple of destroyed cars in this area. The tornado proceeded through additional densely populated areas of Moore shortly thereafter, where several large groups of homes were flattened in residential areas, with a mixture of high-end F4 and low-end F5 damage noted in the survey. Near Janeway Avenue, four people were killed in an area where multiple homes were completely destroyed. A woman, who took shelter with her husband and two children, was also killed when she was blown out from under the Shields overpass on Interstate 35. The tornado weakened somewhat as it moved through the Highland Park neighborhood of Moore, but still caused widespread F3 and F4 damage.


title: 1999 Bridge Creek–Moore tornado

text: The tornado entered Oklahoma County and struck the southeast fringes of Oklahoma City, where it re-intensified to high-end F4 strength; two people were killed in this area as a building housing a trucking company was completely destroyed. Shortly before it tracked into the county, patrons and employees at Crossroads Mall were evacuated to storage areas in the basement of the building. Numerous industrial buildings were leveled in this area of the city. A freight railroad car, weighing was thrown . The car bounced as it traveled, remaining airborne for at a time. Multiple homes were also completely destroyed in southeast Oklahoma City, and one woman was killed in that area. Crossing Southeast 44th Street into Del City, the tornado moved through the highly populated Del Aire housing addition, killing six people and damaging or destroying hundreds of homes, with many sustaining F3 to F4 damage. Seven people were killed as a direct result of the tornado in Del City, and hundreds of homes were damaged or destroyed.