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}} The ''Vulcan'' rocket is an American heavy-payload launch vehicle currently under privately-financed development by United Launch Alliance. To date, the ULA board of directors have made only short-term funding commitments to the rocket development project, and it is unclear whether long-term funding will be available to complete the project. == History == ULA had considered a number of launch vehicle concepts in the decade since the company was formed in 2006. Various concepts for derivative vehicles based on the Atlas and Delta lines of launch vehicles they inherited from their predecessor companies were presented to the US government for funding. None were funded beyond concept stage. In early 2014, geopolitical and US political considerations led to an effort by ULA to consider the possible replacement of the Russian-supplied RD-180 engine used on the first stage booster of the Atlas V. Formal study contracts were issued by ULA in June 2014 to a number of US rocket engine suppliers.〔 ULA was also facing competition from SpaceX — then seen to affect its core national security market of US military launches — and by July 2014, the US Congress was debating whether to legislatively ban future use of the RD-180.〔 〕 In September 2014, ULA announced that it had entered into a partnership with Blue Origin to develop the BE-4 LOX/methane engine to replace the RD-180 on a new first stage booster. The engine was already in its third year of development by Blue Origin, and ULA said it expected the new stage and engine to start flying no earlier than 2019.〔 Two of the -thrust BE-4 engines were to be used on a new launch vehicle booster. In October 2014, ULA announced a major restructuring of company processes and workforce in order to reduce launch costs by half. One of the reasons given for the restructuring and new cost reduction goals was new competition in the launch market from SpaceX.〔〔 ULA stated it planned to have preliminary design ideas in place for a blending of its existing Atlas V and Delta IV technologies by the end of 2014, in order to build a successor to the Atlas V that would allow them to cut Atlas V launch costs in half.〔 〕 A part of the restructuring effort was described as the effort to co-develop the alternative BE-4 engine with Blue Origin for the new launch vehicle.〔 〕 ULA first referred to the successor concept vehicle as a "next generation launch system" in October 2014〔 and used that descriptor for the rocket through the end of 2014 and into early 2015.〔 〕 ULA did not release details by the end of 2014, but unveiled the new vehicle April 2015. On 13 April 2015, CEO Tory Bruno unveiled the new ULA launch vehicle as the ''Vulcan'' at the 31st Space Symposium, a new TSTO rocket that would be rolled out incrementally. The ''Vulcan'' name was chosen after an online poll to select the name. Vulcan Inc. has stated that it holds the trademark on the name and has contacted ULA.〔 〕 , the ULA board had not yet approved the new launch vehicle, with first launch planned in 2019.〔 ULA plans an "incremental approach" to rolling out the vehicle and its technologies.〔 〕 Deployment will begin with the first stage, based on the Delta IV's fuselage diameter and manufacturing process and is expected to use two BE-4 engines. Aerojet Rocketdyne's AR-1 engine is being retained by ULA as a contingency option, with a final decision to be made in 2016. The first stage can have from one to six solid rocket boosters (SRBs), and in the maximal configuration could launch a heavier payload than the highest-rated Atlas V, though still less than the Delta IV Heavy. A later feature is planned to make the first stage partly reusable. ULA plans to develop the technology to allow the engines to detach from the vehicle after cutoff, descend through the atmosphere with a heat shield and parachute, and finally be captured by a helicopter in mid-air.〔 In April 2015, ULA estimated that reusing the engines would reduce the cost of the first stage propulsion by 90%, with propulsion being 65% of the total first stage build cost. Initial configurations of Vulcan will use the same Centaur upper stage as the Atlas V, with its existing RL-10 engines. A later advanced cryogenic upper stage — called the ''"Advanced Cryogenic Evolved Stage"'' (ACES) — is conceptually planned for full development by ULA in the late 2010s. ACES would be LOX/LH2-powered by one to four rocket engines yet to be selected. This upper stage will include the Integrated Vehicle Fluids technology that could allow long on-orbit life of the upper stage, measured in weeks rather than hours.〔 In 2015, ULA stated its goal was to sell a "barebones Vulcan" for half the price of a basic Atlas V rocket, which , sells for about $164 million. Addition of strap-on boosters for heavier satellites would increase the price.〔 〕 In May 2015, the ULA CEO released a chart showing a potential future Vulcan Heavy three-core launch vehicle with -payload capacity to Geosynchronous Transfer Orbit, while a single-core Vulcan 561 with the ACES upper stage would have capacity to the same orbit.〔 〕 In September 2015, ULA and Blue Origin announced an agreement to expand production capabilities in order to manufacture the BE-4 rocket engine currently in development and test. However, ULA also reconfirmed that the decision on the BE-4 vs. the AJR AR-1 would not be made until late 2016, with maiden flight of Vulcan no earlier than 2019.〔 〕 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「Vulcan (rocket)」の詳細全文を読む スポンサード リンク
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