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Grasshopper and the Falcon 9 Reusable Development Vehicles (F9R Dev) are experimental technology-demonstrator, suborbital reusable rockets that make vertical takeoffs and vertical landings.〔 〕 Two prototypes have been built to date, and both are ground-launched test vehicles for the broader SpaceX reusable launch system development program.〔 A third prototype test vehicle was being built as of April 2014.〔 Grasshopper was announced in 2011〔 and began low-altitude, low-velocity hover/landing testing in 2012. The initial Grasshopper test vehicle was tall and made eight successful test flights in 2012 and 2013 before being retired. A second Grasshopper-class prototype test vehicle design—the larger and more capable Falcon 9 Reusable Development Vehicle (F9R Dev) based on the larger Falcon 9 v1.1 launch vehicle form factor—will result in two additional VTVL test vehicles which will be used for testing at higher altitudes and supersonic speeds as well as additional low-altitude testing with the larger vehicle. The F9R Dev1 vehicle was built in 2013–2014 and made its first low-altitude flight test on 17 April 2014; it was lost during a three-engine test at the McGregor test site. A second F9R Development Vehicle—F9R Dev2—is currently being built. The Grasshopper and F9R Dev vehicles are being developed and tested by Space Exploration Technologies (SpaceX) in order to assist development of the reusable Falcon 9 and reusable Falcon Heavy rockets, which will require vertical landings of the near-empty Falcon 9 and Falcon Heavy first-stage booster tanks and engine assemblies. The project is privately funded by SpaceX, with no funds provided by the government. Grasshopper and F9R Dev are only two elements of the multi-element, incremental ''SpaceX reusable launch system development program'' test program, a program that includes Grasshopper and F9R Dev1 testing in low-altitude, low-velocity environments at the SpaceX Texas test site; high-altitude, mid-velocity testing of the F9R Dev2 test vehicle at Spaceport America in New Mexico; and high-altitude, high-speed controlled-descent tests of post-mission (spent) Falcon 9 booster stages on Falcon 9 missions that began in September 2013 and have continued into 2014. ==History== The Grasshopper technology demonstrator first became known publicly in the third quarter of 2011, when space journalists first wrote about it after analyzing US government space launch regulatory documents.〔 Shortly thereafter, SpaceX confirmed the existence of the test vehicle development program, and projected it would begin the Grasshopper flight test program in 2012. Grasshopper began flight testing in September 2012 with a brief, three-second hop at the company's Texas test site, followed by a second hop in November 2012 with an 8-second flight that took the testbed approximately off the ground, and a third flight in December 2012 of 29 seconds duration, with extended hover under rocket engine power, in which it ascended to an altitude of before descending under rocket power to come to a successful vertical landing. From the announcement in 2011, SpaceX has achieved each of the schedule milestones that they publicly announced. SpaceX said in February 2012 that they were planning several vertical-takeoff, vertical-landing (VTVL) test flights during 2012, and confirmed in June 2012 that they continued to plan to make the first test flight within the next couple of months.〔 Updated photos of the rocket on the test pad appeared in a news article on 11 Sep 2012, They achieved first flight on September 21, 2012.〔 Beginning in October 2012, SpaceX discussed development of a second generation Grasshopper test VTVL vehicle, one that would have lighter-weight landing legs that fold up on the side of the rocket, would have a different engine bay and would be nearly 50% longer than the first Grasshopper vehicle. In May 2013, they announced that the higher-altitude, higher-velocity part of the Grasshopper flight test program would be done at Spaceport America—and not at the Federal Government's adjacent White Sands Missile Range facility as previously planned —near Las Cruces, New Mexico, and signed a three-year lease for land and facilities at the recently operational spaceport. SpaceX indicated in May 2013 that they do not yet know how many jobs will move from McGregor, Texas to New Mexico. SpaceX retired the Grasshopper test vehicle after making a total of eight successful test flights between September 2012 and October 2013.〔 〕 SpaceX began flight tests of the F9R Dev vehicle—F9R Dev1—in April 2014.〔 〕 , the FAA permit to fly the Falcon 9 Reusable Development Vehicle in Texas is open until February 2015. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Grasshopper (rocket)」の詳細全文を読む スポンサード リンク
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