Free One False Step by Richard Tongue

moon, but for Mars ; it's objective was the assembly in orbit of a spaceship capable of setting a man on Mars. The concept of the rocket dated back to before the launch of the first Sputnik, and undertook a wide variety of redesigns in order to increase the payload. Still, despite its size, it would have had considerably poorer performance than the comparable Saturn V rocket – only able to put 75 tons into orbit.
     The first alternative was the R-56, developed by Mikhail Yangel, who had formerly worked for Korolev before receiving his own bureau. This would be a minimal lunar mission, only able to place 30 tons into a lunar trajectory, and would use a new high-performance engine design, the RD-270. This rocket was never seriously considered; it is thought that Yangel did not wish to split the scarce space resources three ways, fearful of the damage this might do to Soviet aspirations in space.
     By far the more serious rival was the UR series. These were developed by Vladimir Chelomei, a long-standing rival of Korolev. The UR-500 rocket would be used to place a cosmonaut in orbit around the moon, and a larger derivative, the UR-700, could be used for a lunar landing. This design returned to the 'direct-ascent' method of landing on the moon, where the whole spacecraft was launched from Earth to land on the moon, though only the top stage would leave the moon to return to Earth.
     By August 1964, the N-1 had been approved as the booster that would be used for the lunar landing program, but crucially, the UR-500 would also be developed for the circumlunar missions. At this point, the Soviet Union essentially had two lunar programs that would be continually competing for resources and attention, each hoping to squeeze the other out. At best, the Soviet Union had far fewer resources to devote to the Moon program than the United States, this was a recipe for disaster.
     The controversy would continue for another two years. Despite the approval of the plan, Chelomei and his bureau (which included Khrushchev's son) attempted to have the UR-700 reinstituted for the lunar landing. Finally, in September 1966, a commission was formed with the goal of reviewing the whole lunar program, and the original plan won the day – and strengthened the importance of the moon program, allowing it greater access to resources and funding. But this was five years after the United States had defined its lunar program.
     Of the two boosters that were selected, the N-1 and the UR-500, only one was destined to ever reach space; and that one would remain a mainstay of first the Soviet and later the Russian space programs for many years, though not in its intended role.
     The UR-500 originated as the carrier for a huge Soviet nuclear bomb, a superbomb designed to carry a payload capable of a 58- megaton yield. The only way the bomb could be delivered to targets in the United States would be through the use of a new missile, and design work quickly began. However, the weapon would fail to find a place in the Soviet nuclear arsenal, which left the missile short of a mission; it was at this stage that its designer, Chelomei, began to suggest that it could be valuable to the moon project.
     The rocket, which would become more famously known as the Proton, consists of three stages, using nitrogen tetroxide and unsymmetrical dimethyl-hydrazine. It would use what for the next twenty years would be the most advanced rocket engines in the world, far ahead of their time. A top stage, known as Block D, would use more traditional liquid oxygen and kerosene.
     Given a combination of the initial military nature of the rocket, and the general Soviet secrecy of the era, little is known today about the design history of the Proton. We do know that its early launches demonstrated poor reliability; fourteen of the first twenty-nine launches were failures, destroying a series of planetary and lunar probes. Though it would become one of the most reliable