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LGarde, also L'Garde or L·Garde, is an American
aerospace Aerospace is a term used to collectively refer to the atmosphere and outer space. Aerospace activity is very diverse, with a multitude of commercial, industrial and military applications. Aerospace engineering consists of aeronautics and astr ...
and defense technology company founded in 1971 in Orange County, CA and is the primary contractor for the Sunjammer spacecraft, the world largest
solar sail 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 p ...
. The company was an early pioneer of thin-skinned, multi-task inflatable structures used in various military and space applications. At the height of the Cold War, L·Garde developed and manufactured inflatable targets and decoy systems for U.S. military defense, and countermeasure systems for the
Strategic Defense Initiative The Strategic Defense Initiative (SDI), derisively nicknamed the "''Star Wars'' program", was a proposed missile defense system intended to protect the United States from attack by ballistic strategic nuclear weapons (intercontinental ballistic ...
(Star Wars). After the Cold-War, the company used the technologies and manufacturing techniques it had developed to land a contract to design and build the
inflatable antenna experiment The Inflatable Antenna Experiment (IAE) was a NASA experiment that began on May 19, 1996, consisting of an inflatable antenna made of mylar which was launched from the Space Shuttle '' Endeavour'' during the 1996 STS-77 mission, in cooperation w ...
and other thin-film inflatable space structures using its unique application of rigidizable tube technology. The company's unusual name is an acronym formed by the initials of the founding partners: Bill Larkin, Gayle Bilyeu, Alan Hirasuna, Rich Walstrom, Don Davis. The "E" comes from the Latin term " et al" (and others) as a tip to other partners and original employees of the company.


History

LGarde engineers took their experience with inflatable structures for military use to space applications around 1992 as a means of controlling the cost of deploying instrumentation into Earth orbit and beyond. They studied development work and lessons learned from projects for the
United States Department of Defense The United States Department of Defense (DoD, USDOD or DOD) is an executive branch department of the federal government charged with coordinating and supervising all agencies and functions of the government directly related to national secur ...
and the NASA going back to the 1960s. Observing the advantages and challenges of deploying a very large inflatable antenna and other structures in Earth orbit using this technology, LGarde engineers also observed changes in structural principles when such structures are used in a zero-gravity environment, and other technical issues arising for large precision structures including surface accuracy, analysis and electrical properties. LGarde's first inflatable space structure project was the Spartan 207 Project, also known as the
Inflatable Antenna Experiment The Inflatable Antenna Experiment (IAE) was a NASA experiment that began on May 19, 1996, consisting of an inflatable antenna made of mylar which was launched from the Space Shuttle '' Endeavour'' during the 1996 STS-77 mission, in cooperation w ...
, which was launched with
Space Shuttle Endeavour Space Shuttle ''Endeavour'' ( Orbiter Vehicle Designation: OV-105) is a retired orbiter from NASA's Space Shuttle program and the fifth and final operational Shuttle built. It embarked on its first mission, STS-49, in May 1992 and its 25th an ...
on mission STS-77, May 19. 1996. The goal of this mission was to inflate a 14-meter antenna on three 28-meter struts built by LGarde under contract with
JPL The Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center in the City of La Cañada Flintridge, California, United States. Founded in the 1930s by Caltech researchers, JPL is owned by NASA ...
. The project was developed under NASA's In-STEP technology development program. Deployed using the shuttle's
Remote Manipulator System Canadarm or Canadarm1 (officially Shuttle Remote Manipulator System or SRMS, also SSRMS) is a series of robotic arms that were used on the Space Shuttle orbiters to deploy, manoeuvre, and capture payloads. After the Space Shuttle ''Columbia'' ...
, the antenna was successfully inflated and the correct final shape was attained. According to the final mission report, the mission was successful and gained a great deal of information about inflating large structures in space. Among the points that the Spartan 207 project proved was the viability of inflatable space structures as a cost-saving concept. The inflatable antenna weighed only about 132 pounds (60 kilograms) and an operational version of the antenna may be developed for less than $10 million - a substantial savings over current mechanically deployable hard structures that may cost as much as $200 million to develop and deliver to space. LGarde engineers expanded their development of inflatable rigidizable structures with low mass structures strong enough to support orbital large solar arrays as well as much smaller
nanosat A small satellite, miniaturized satellite, or smallsat is a satellite of low mass and size, usually under . While all such satellites can be referred to as "small", different classifications are used to categorize them based on mass. Satellites ca ...
s. Among the many detail design parameters they considered were tube design (for rigidizable material), alternative beam types and designs (e.g., trusses), material thickness, laminates, and the best way to resolve Euler
buckling In structural engineering, buckling is the sudden change in shape (deformation) of a structural component under load, such as the bowing of a column under compression or the wrinkling of a plate under shear. If a structure is subjected to a ...
. A project, conducted with JPL under NASA's Gossamer Spacecraft program in 1999, sought to build an inflatable reflector to concentrate solar energy for space electrical power generation, while acting as a large aperture high gain antenna. Among the goals of the Gossamer Spacecraft program was to reduce the mass and stowage volumes of a power antenna while maintaining comparable yield from electrical power generation. Additional development came in 2005, when LGarde began utilizing material rigidization methods that provide a long lasting reflector shape without requiring continuous inflation. Engineers settled on an aluminum/plastic laminate as the rigidization method of choice over cold rigidization of a
Kevlar Kevlar (para-aramid) is a strong, heat-resistant synthetic fiber, related to other aramids such as Nomex and Technora. Developed by Stephanie Kwolek at DuPont in 1965, the high-strength material was first used commercially in the early 1970s ...
thermoplasticelastomer composite as a means of accomplishing two goals: 1) diminish stowage space and thereby expanding the potential aperture size of the mirror reflectors and 2) eliminate the need for “make-up” gas needed for purely inflatable reflectors to remain inflated in space. LGarde engineers later advanced the readiness level of the inflatable planar support structure for the gossamer antenna system with additional design, analysis, testing, and fabrication of an inflation-deployed rigidized support structure for the waveguide array. Going into 2002, LGarde was developing polyurethane resins for a 3-ply composite laminate that could be used in the fabrication of rigidizable structures suitable for use in space. In a paper submitted to the American Institute of Aeronautics and Astronautics (
AIAA The American Institute of Aeronautics and Astronautics (AIAA) is a professional society for the field of aerospace engineering. The AIAA is the U.S. representative on the International Astronautical Federation and the International Council of t ...
), engineers found that such composites can be used to fabricate ultra-lightweight deployable rigidizable structures for space applications and that polyurethane was chosen because it could become rigid when exposed to the low temperatures of space. The paper goes on to observe that under NASA's SSP program ( Space Solar Power Truss), a 24-foot long inflatable-rigidizable truss using polyurethane composites withstood a compression load of 556 pounds, 10% above its designed compression strength while reducing mass of comparable mechanical structures by a factor of 4. It had been long theorized that
solar sails 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 p ...
could reflect photons streaming from the sun and convert some of the energy into thrust. The resulting thrust, though small, is continuous and acts for the life of the mission without the need for propellant. In 2003, LGarde, together with partners JPL,
Ball Aerospace Ball Aerospace & Technologies Corp. is an American manufacturer of spacecraft, components and instruments for national defense, civil space and commercial space applications. The company is a wholly owned subsidiary of Ball Corporation (NYSE: BAL ...
, and
Langley Research Center The Langley Research Center (LaRC or NASA Langley), located in Hampton, Virginia, United States of America, is the oldest of NASA's field centers. It directly borders Langley Air Force Base and the Back River on the Chesapeake Bay. LaRC has fo ...
, under the direction of NASA, developed a solar sail configuration that utilized inflatable rigidized boom components to achieve 10,000 m2 sailcraft with a real density of 14.1 g/m2 and potential acceleration of 0.58 mm/s2. The entire configuration released by the upper stage has a mass of 232.9 kg and required just 1.7 m3 of volume in the booster. Additional advancement of the solar sail project came as LGarde engineers improved “sailcraft” coordinate systems and proposed a standard to report propulsion performance. LGarde was selected by NASA to build construct the Sunjammer spacecraft, which would have been the world's largest solar sail. Slated for launch in January 2015, Sunjammer was constructed of Kapton and was square with a total surface area of over , providing a thrust of about 0.01  N. The ultrathin 'sail' material was only 5
μm The micrometre ( international spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer ( American spelling), also commonly known as a micron, is a unit of length in the International System of Uni ...
thick with a low weight of about 32 kilograms (70 lb). To control its orientation, Sunjammer would have used gimballed vanes (each of which is itself a small solar sail) located at the tips of each of its 4 booms completely eliminating the need for standard propellant. On October 17, 2014, NASA cancelled the Sunjammer project after investing four years and more than $21 million on the project.


References

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