Well, folks, it's Wednesday, and you know what that means: New Eyes Turned Skyward! When we last left off, the new NASA Administrator George Low was facing a future of shrinking budgets, and having to make hard choices on what to cut and what to save.
Eyes Turned Skyward, Post #3:
The plans Low was considering envisioned a space-station centered strategy for NASA, where logistics and crew would be dealt with not by an advanced (and expensive) shuttle craft but rather modified variants of existing spacecraft, particularly the Apollo CSM and Saturn IB (though the Gemini and Titan III were advanced as options by their respective manufacturers). As NASA thought prior to Kennedy's famous speech generally held that the main goal of the space agency should be to construct a permanent space station, vaguely followed by a flight or two around the Moon (but no landings, at least until later), this was in many ways a return to form. As eventually adopted in the FY 1971 budget, the Skylab program would consist of two main parts. After the launch of Apollo 18, a "dry workshop"--essentially the wet workshop constructed on the ground and therefore much more capable--named "Skylab" would be launched into LEO. This would carry as its main piece of scientific equipment a solar telescope, the Apollo Telescope Mount, originally intended for AAP projects. In addition, it would carry a wide variety of remote sensing equipment, intended for tests of both the equipment for future remote sensing missions and of the ability of astronauts to contribute to or detract from Earth observation, a number of biological experiments probing the effects of space on living organisms for the benefit of future astronauts, and a number of materials experiments investigating whether the unique environments of space could be used in manufacturing processes impossible on Earth. In all this it was quite similar to the contemporaneous Soviet Salyut program, right down to the provision of several non-Skylab "free-flyer" missions to test experiments and capabilities before using them on the station itself. Once this preliminary program was wrapped up, the second part would begin. A heavily modified variant of the backup built for the first Skylab--Skylab B--would be launched by the last Saturn V into a similar orbit. This advanced Skylab would delete the solar telescope, but otherwise be far more capable, designed for continuous resupply, on-orbit repair, and even perhaps a degree of expandability. This would be occupied by a series of crews operating many different experiments, including (perhaps) some Japanese or European ones, for 5-6 years after launch. After Nixon and Brezhnev agreed to start the Apollo-Soyuz Test Project, that too was included in the plan. After the initial test flight, Skylab B would play host to several Soyuz and Apollo crews at the same time, for stays of up to as much as 90 days together, becoming the "International Skylab". Afterwards, additional modules (suitably equipped for automatic or semi-automatic rendezvous and dock operations) might be launched, further extending the station's capabilities, or a whole new station, designed from the ground up using "lessons learned" by the Skylab missions, might be developed. While this promised a new era of international cooperation, at NASA the technical challenges of the plan were wearing, for NASA's equipment (designed to achieve the Moon landing ASAP) was ill-suited for the missions at hand, in particular the Block II CSM and the Saturn IB rocket.
The Block II was, especially after the modifications following the Apollo 13 accident, a reliable and capable spacecraft. Still, it had its shortcomings for the new type of space station missions planned for the 1970s and beyond. In particular, at its full wet mass--the mass of the entire spacecraft while fully fueled and carrying its maximum payload--it weighed over 65,000 lbs (30,000 kg), far more than the comparable Soviet spacecraft, the Soyuz, which had a mass of just 14,500 lbs (6,500 kg) while providing only 50% more habitable volume for the crew. While it was far more capable than its Soviet equivalent--the Soyuz itself was not capable of being used on circumlunar flights, and the two variants that were were far less commodious than either Soyuz or Apollo--those capabilities were entirely superfluous, and prevented it from being launched by either the Saturn IB or the planned Saturn IC without carrying a smaller-than-capacity fuel load. As such, it was of no surprise to anyone that in FY 71 NASA requested funding for the development of the "Block III" variant, which was immediately contracted out to North American Rockwell. It would feature enhanced on-orbit life while in 'sleep' mode, reduced fuel space, a combination of parachutes and airbags that would allow NASA to dispense with the expensive naval recovery fleet, and many other improvements that would make it lighter but more capable of achieving the missions placed upon it.
Due to the need for continuous resupply and crew cycling, low cost reliable launch vehicles were a must for NASA's forthcoming projects. However, though the Saturn IB was reliable, it was certainly not low cost in comparison to the other launchers available at the time. While it cost five times more to launch than the Titan IIIC, it was only capable of lofting two-fifths again as much payload, a poor bargain in anyone's book. Various proposals to replace or improve it had been floated for some time, ranging from simply upgrading its engines and decreasing its structural mass to outright disposing of it for a new rocket, perhaps one based on a huge solid first stage or the S-II stage from the Saturn V. Under the circumstances the agency found itself in in 1970, though, merely recapitulating the basic design would get them nowhere--it was clearly far too expensive for sustained use--but an all-new design would require much of the NASA budget and might not be ready by the time the existing stocks of Saturn IBs were depleted. The concept of the Saturn IC, a significant modification which yet used mostly existing Saturn hardware, broke into this logjam in late 1970. It had been noted that the F-1A, a relatively modest upgrade of the existing and highly successful F-1, had a greater thrust than the cluster of 8 H-1s used on the first stage of the Saturn IB, and a considerably larger specific impulse. Combined with a modest upgrade to the S-IVB second stage, this would allow a rocket using a single F-1A as the first-stage engine to lift a greater payload than the Saturn IB, especially if the cluster design of the first stage was replaced with a lighter monolithic design, while being considerably simpler in design and cheaper to fly. The idea of the Saturn IC quickly gained acceptance by the agency, and by 1971 development on the new first stage was beginning at Michoud, with first flight expected by the middle of the decade.
Finally, there was the issue of logistics and station resupply. It was quickly realized that, while Skylab A itself would probably not need much resupply, Skylab B and any future stations would. The sheer mass and volume of supplies needed--everything from film for cameras and telescopes to mail for the astronauts--made Apollo flights a poor way to provide this service. They were burdened by having to carry a crew, the limited available volume within the CSM itself, and the unwillingness of the still mostly-pilot astronauts to "deliver milk". Thus, thought turned towards developing some type of autonomous vehicle that could be launched by the Saturn IC carrying a substantial amount of cargo and supplies to orbit, then rendezvous and dock with Skylab without needing a crew on board. As analysis slowly proceeded, it gained the name "AARDV," for Autonomous Automated Rendezvous and Docking Vehicle, but was quickly paraphrased to "Aardvark," and began to take shape. A suitably modified Block III SM would be used as the "brains and brawn" of the vessel, responsible for on-orbit maneuvering, while a large pressurized container would replace the CM to store cargo. While this pressurized container would not be able to reenter, it was soon recognized that this would allow the easy disposal of trash, allowing the use of the oxygen tank of the S-IVB as additional pressurized volume on Skylab B.
