Today President Nixon announced that Project Neptune the reusable Space Shuttle had been selected as the next NASA program with the goal of making travel to space less expensive than it had been during the 1960's. In light of this plan to reduce costs and risks the Shuttle Orbiter would be launched by a modified Saturn V rocket. The first stage would separate at high altitude and once the second stage was clear it would preform a braking maneuver to bring its relative velocity to zero. Then it would free fall for miles in a computer controlled attitude, then right before impact with the ocean solid rocket braking thrusters would ignite for 5 seconds to allow a gentle computer guided splash down into the Atlantic ocean. After that an ocean going tug boat would lash on to the S-V-C-2 and tow it back to Cape Canaveral where it would be reconditioned and used again for a later flight.
Project NeptuneThe second stage was the same S-V-II in external dimensions but internally the new S-V-II-B was completely rearranged to form an external tank for the orbiter rather than a 'live stage'. To fit the same energy density of fuel in the same volume the new ET was designed to carry the same Liquid Oxygen, albeit in a larger tank, but the fuel component was Liquid Methane aka Liquefied Natural Gas. This had two significant benefits, Liquid Methane and Liquid Oxygen are stored at nearly the same temperature and pressure which would greatly simplify the internal plumbing and allow the two components to share an uninsulated inner tank wall, which would save a great deal of weight on a second tank wall. It also eliminated the insulation that had to go between the Liquid Hydrogen and Liquid Oxygen tanks because the Hydrogen was so cold it would turn the Oxygen slushy and potentially damage the engines or even clog the oxidizer lines. Secondly because Methane generates many more calories of heat on a volume basis than Hydrogen a smaller volume of fuel was needed allowing the existing S-V-II shell with the manufacturing facilities already in place to hold all the fuel needed. Another advantage was the relative expense of the fuel, converting simple natural gas into liquid rocket fuel was far less expensive than first generating Hydrogen gas, then cooling it to extremely low temperatures and holding it at those temperatures until launch commenced. Hydrogen was very hard to store as a gas because the molecule was so small it would slowly escape through the surface of almost any container it was stored in by working its way between the molecules of the tank structure. Even worse this process would turn all known materials brittle so that they had a tendency to shatter at the least convenient times. On the other hand Methane was so incredibly easy to store nature had been accumulating it in reservoir formations in the ground for millions of centuries. In addition to the internal changes to the tanks the five engines would be removed from the S-V-II design and those engines would be shifted to the orbiter vehicle, which would be attached to the side of the stage instead of riding on top. This required structural weight be dedicated to securing the orbiter during the burn much as had been proposed for the external tank with solid rocket booster option. The redesigned S-V-II-B structure would use the weight saved by the changes to put in place solid rocket braking units like those in the first stage in hopes of eventually being able to recover these stages from soft splash down in the Indian Ocean, but for the early test flights at least they would be used to ensure the stage burned up in a high speed shallow angle reentry by accelerating the stage into a maximum velocity entry rather than braking it to fall vertically with minimum reentry heating.
In a political move that was designed to turn one of the biggest opponents of NASA into an ally President Nixon ordered the design to make maximum use of milk products, specifically Casein plastic. This would shift Senator Walter Mondale from his axiomatic hatred of all things space to a proponent because he was in favor of any federal program that used Milk and thus supported the dairy industry of his state. As a result of this requirement the concept of a durable reusable heat shield made of complicated, delicate silica wafer tiles was set aside for future development in favor of Casein plastic tiles for single use only. The new tile 'scheme' consisted of hundreds of identical hexagonal plastic tiles that individually bolted to the frame of the shuttle. Though they were substantially heavier, over twice the weight of the silicon wafer system they were a great deal cheaper to produce and replacing them was simplified by the fact that the vast bulk of them were a single interchangeable design. The fact that the NASA contractor factory in Minnesota produced tons of Butter and Ethanol from the milk in addition to the plastic was just a bonus for the state of Minnesota.
The first step in making the plastic was to centrifuge the milk at extreme high speed to separate out the milk fat, which was sent to the butter and cream process. The second step was to add a precisely calculated amount of industrial white vinegar to cause the Casein to form small clumps which were then filtered out and sent to the plastics portion of the plant. In the last step Lactase enzymes were added breaking the Lactose milk sugar into Glucose and Galactose and the treated liquid was fed to ethanol producing wine yeast. NASA also purchased the Ethanol at a set price for use as a solvent and fuel additive for their vehicle fleet.
Using a disposable heat shield system did save the design and testing team a huge sum of money and time, though in the initial proposal the Apollo phenol resin made from crude oil had been the proposed plastic. Securing Senate support and silencing the long time critical Senator Mondale was worth the extra expense incurred. The time saved in research and development to perfect the silicon tiles and the bonding system that would both hold them to the frame and allow them to expand and contract as they heated and cooled was worth several years in the development process. Each of the prior programs, Mercury, Gemini and Apollo had taken from five to seven years. By using already wind tunnel tested shapes and modified existing hardware it was expected that the partially reusable Space Shuttle would be able to meet the same time table. As it turned out a modest budget boost actually lead to drop tests of the Enterprise orbiter in 1976 and the first 'flight test' used the Trans Atlantic Abort Mode flew in June 1977. Fred Haise and Alan Bean lifted off from Kennedy Space Center and the orbiter Columbia landed in Casablanca, Morocco 29 minutes later proving the shuttle could survive an abort with just one engine in the second stage working. The Columbia had ejector seats for both crew members just in case, but fortunately they were unnecessary and the flight was deemed a complete success.
In December 1978 the Enterprise makes its first orbital flight, the first manned orbital mission since the Apollo Soyuz Test Project in 1975 and successfully docks with the Skylab space station. During a space walk the astronauts attach a new orbital maneuvering unit to the forward docking port and restock the station with enough supplies to support a crew for a year in space. After they detach from the station ground control uses the new thruster unit to boost the station to a higher stable orbit so that a later Shuttle mission can ferry a crew up for a long duration expedition in orbit.