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Europe in space (7)
In the case Big Gemini was to be launched by a Titan III, the pressurized cargo section would end strikingly similar to a Soviet Salyut space station in length, diameter and mass.

One thing is sure, there is no lack of bold concepts involving space stations, most of them derived from Skylab - one way or another. Saturn upper stages - the S-II and S-IVB - are quite voluminous thanks to hydrogen very low density. It is that immense volume space station designers intend to use.

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Skylab option C is a single-launch space station. This configuration features a 92-foot-long, 23-foot-diameter core module launched as part of a Saturn V vehicle. The module would provide 26,000 cubic feet of pressurized volume, separated into 7 "decks" connected by a centralized passageway. Seven berthing ports would be located on the circumference of the module to place possible international modules and other elements.

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Skylab is first and foremost a S-IVB stage turned into a space station; which mean the J-2 engine has been removed and the fuel tanks filled with an astronaut habitat. As such Skylab no longer can propel itself into orbit. There's no reason Skylab recipe couldn't apply to the even larger S-II. In both case the station ends so heavy and voluminous only a Saturn V can orbit it.
An alternate approach is the so-called wet workshop, where the rocket stage keep its engines and tanks hence the capacity to orbit itself. The obvious issue is that, since the tanks are full of propellants they can't be outfitted as a space station on the ground. It fell to astronauts doing that job once in orbit - and it is a totally different matter which led to the abandonment of the concept.

In the early days of Apollo however legendary Wernher von Braun proposed an intermediate solution - half Skylab, half wet-workshop.

The S-II and S-IVB are essentially similar - they feature a hydrogen tank on top and an oxygen tank below. A little know fact is that the hydrogen tank domes or bulkheads feature a 40 inch (1 meter) diameter manhole.

It is only used by Douglas and North American employees on the ground for quality control of the rocket stages. What von Braun suggested was to literally slide a Skylab or Salyut space station through that opening (the opening would have previously been enlarged, of course !)

One has to figure a 4.5 m diameter Salyut (or Big Gemini cargo section) encased into a 10 m S-II - resulting in an interval of 6.5 m between the two hulls.

Once the space station "slidded" into the rocket stage tank the aforementioned "interval" would be pressurised providing the astronaut with a truly immense volume to live in.

The combination of all the above results in a host of space station designs. The Douglas company noted the trick would also work with their 6.6 m S-IVB - in some way a Salyut could be slidded into a Skylab via the S-IVB opening !

The extreme logical end of this would have Skylab itself slidded into a S-II (provided the opening could be enlarged to 6.6 m, which is probably a bridge too far.)

So rigid modules could be slided through an S-IVB or S-II manhole. An interesting alternative might be the so called inflatable. The habitat would be folded, deflated, inside the hydrogen tank; then, once the stage in orbit with the propellants depleted, the module would be inflated, filling the tank better than any rigid module. NASA gave a limited contract study to ILC Dover, the company that currently manufacture the astronaut space suits.



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"A meeting between American and European representatives took place in Washington from 14 to 16 June 1972. Behind the rhetorical requirements of diplomacy, both the opening and the concluding remarks by Herman Pollack (Director, Bureau of International Scientific and Technological Affairs of the Department of State) revealed the tense atmosphere of the gathering.

Cooperation on the tug was formally agreed on but at the same time ELDO involvement in space station modules was prohibited. While the final go-ahead on participation in the development of the tug had been expected, the veto on the modules came as a sudden surprise. The reason officially given were mainly technical. The station modules, it was said, were a moving target; it was not clear how, when and what would be built. The secondary literature gives additional reasons including:

1. American skepticism, widely shared in Europe, over Europe's technical ability to develop a full, large space station module on its own

2. Rejection of Big Gemini -based pressurised shell in favor of larger, Skylab-like modules

3. Johnson Space Center willingness to take complete control over the space station over Marshall and ELDO.

The European delegates were rightly worried, since NASA administrator James Beggs added that the tug now amounted to a modified Lockheed Agena. The only technological transfer would be the automated approach and docking system. Italy and Germany would build Agenas under licence - much like they had build F-104G Starfighters a decade earlier.

The Europeans were clearly dissatisfied, and sought a larger commitment. That's the moment when the sortie lab made a spectacular come-back. A pressurised module signified European willingness to enter the field of manned space activities and to pay its entrance fee.

After insertion into orbit by a classic rocket, the Agena would ferry and dock the module to the American space station. Called the Agena Transfer Vehicle – ATV - the unmanned European spacecraft would add its volume and cargo to the American orbital facility.

Both Agena and pressurised module were essentially off-the-shelf components, the later nothing more than a Big Gemini cargo section. This meant development belonged to American contractors; Europe work would amount to a build things under licence. As a compensation, NASA allowed the Europeans to eventually turn some Agena cargoes into little science laboratories that could be added to the American future space station.

Excerpt from: A history of the European Space Agency, 1958 - 1987
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