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Nova was a series of proposed rocket designs, originally as NASA's first large launchers for missions similar to the production-level Saturn V. Nova studied designs that closely mirrored the Saturn V in basic concept, power, size and function. Differences were minor but practical, and the Saturn was selected for the Apollo Project largely because they would re-use existing facilities to a greater extent and could make it to the pad slightly earlier. During a series of post-Apollo studies in the 1960s, considerations for a manned mission to Mars revealed the need for boosters much larger than Apollo's, and a new series of designs with as many as eight Rocketdyne F-1 engines were developed under the Nova name (along with the Saturn MLV). The image of the Nova C8 is commonly used as a representative of the entire Nova series, and many references to Nova refer specifically to these post-Apollo versions. The two series of designs were essentially separate, but shared their name. Thus, "Nova" does not refer to a specific rocket design, just a rocket larger than the Saturn V in most cases. To add more confusion, the final Saturn V design was larger than some of the early Nova proposals. ==Lunar rockets== The first Nova series was designed in-house at NASA in 1959. This project examined several designs, the smallest having four F-1s in the lower stage and J-2s in the uppers. This design placed 24 tons in a lunar injection trajectory. These designs were presented to President Dwight D. Eisenhower on January 27, 1959. The Nova designs were not the only lunar rockets being considered at the time. The US Air Force was in the process of defining its Lunex Project, including a massive booster design using a cluster of solid fuel rockets in the lower stage with liquid hydrogen-powered uppers mounting the J-2 or M-1. Meanwhile, at the US Army's Redstone Arsenal, Wernher von Braun was developing his "Juno V" design, using a cluster of Jupiter and Redstone related engines and tanks for a lower stage, a Titan I missile as the second stage. In 1959 the Army decided it was no longer interested in developing large boosters, for which it had no immediate need, and passed von Braun's team over to NASA. This left NASA with two large booster designs, their own Nova, and von Braun's recently renamed Saturn ("the one after Jupiter"). Over the next two years the competing NASA and Air Force studies continued, but immediately following President John F. Kennedy's call to reach the moon before the end of the decade, NASA was given the mission and work on Lunex ended. Originally, NASA had designed Nova for the "direct ascent" mission profile, in which a single large spacecraft would be placed in earth orbit. Von Braun favoured a profile that built up the spaceship in Earth orbit, which reduced the launch mass needed for any one launch. However, as studies into the spacecraft needed for the mission started, it became clear that the systems would be much heavier than initially suspected; the existing Nova designs were too small, and the original Saturn design would need up to fifteen launches to put all the parts and fuel into orbit. A redesign of both plans followed. Nova was still targeting the direct ascent approach, which required the most lift capacity. The most powerful of the resulting "normal" designs, the 8L, included eight F-1's in the lower stage and placed 68 tons in a translunar trajectory. Other designs in the series replaced the F-1s with large solids, while others studied nuclear rocket engines for the upper stages. Lunar payload for the various models varied between 48 and 75 tons. A number of upgraded Saturns were also studied. Dr. von Braun's original Saturn design became the A-1 model, while the A-2 replaced the Titan missile with a Jupiter. The more powerful B-1 model used a cluster of Titans for its second stage, but was otherwise similar to the A-1. More "radical" proposals, those requiring new engines, were lumped together in the "C series". C-1 was similar to the A-1, but used new upper stages derived from Titan engines, while the similar C-2 used new J-2 powered upper stages. C-3 through C-5 used the same J-2 powered uppers, but added a new first stage powered by three, four, or five F-1 engines (hence the names). Dr. von Braun's favoured approach remained Earth Orbit Rendezvous (EOR), but this time based on two Saturn C-3's. The debate between the various approaches came to a head in 1961, and the outcome was unexpected by both teams. Instead of either the direct ascent or earth orbit rendezvous, the working group instead selected a third option, Lunar Orbit Rendezvous (LOR). LOR had a mass requirement about mid-way between the Saturn C-3 and Nova 8L. After studying what would be required to modify either booster to the new requirement of about 200,000 lb in low earth orbit (LEO), it seemed that the Saturn C-5 would be the best solution. The C-2 model would also be built as a testbed system, launching subassemblies into orbit for flight testing before the C-5 would be ready. The main determinant in selecting the Saturn over the Nova was that the Saturn C-5 could be built in an existing factory outside New Orleans, later known as the Michoud Assembly Facility, while the larger diameter Nova would need new factories to be built. Studies on the Nova series continued into 1962 as a backup for Saturn, but were eventually ended as the Saturn-based LOR profile became ingrained. 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「Nova (rocket)」の詳細全文を読む スポンサード リンク
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