Sidebar: The Mercury Space Station

mercury-space-station

One of two configurations of a proposed Mercury-based space station. The other had the capsule stay in place with an inflatable tunnel running between the two hatches. Click for a larger view.

(Another little experiment along the lines of the Chief Designer posts. I’m finding a few space projects here and there that couldn’t support an entire discussion in False Steps’ usual format, but that still are worth examining. I’m thinking that perhaps they can be used as short sidebars here and there in the final product. I’ve tried two of them out on Reddit so far and they seem popular enough, so here they are for you too.)

In August 1960 McDonnell Aircraft suggested to NASA that a Mercury capsule should be extended into a small space station. This was despite the fact that a human being could just barely fit into a Mercury capsule, and couldn’t live in one for long—the final Mercury, Mercury-Atlas 9, could only last a full day because it was stripped down to hold more consumables, and even at that Gordon Cooper was only able to get it back to Earth through heroic efforts on his part.

That didn’t deter McDonnell. They suggested building a secondary, cylindrical capsule with the main Mercury capsule mounted to one end, and then sticking the whole thing on top of an Atlas LV-3B to fire it into space. Since it would be too heavy for that rocket to lift, the new capsule would have an Agena motor attached to its other end, which would finish pushing the spaceship into orbit.

They stated that the one man aboard the capsule could, with the aid of the extra living and storage space, live on board for an entire two weeks, performing experiments and whatnot until it was time to return home. As a result, they pitched it as a “space station”, but it really was no such thing. Altogether the whole thing only massed a few hundred kilograms more than the Vostok capsule that carried Yuri Gagarin into space; its internal living space was actually smaller than a modern-day Soyuz capsule. Nobody calls either of those craft space stations.

The Mercury Station never got built and likely the kicker was that the Mercury was pretty much an experimental craft. It was never intended to be upgraded and so McDonnell had to resort to a remarkable kludge just to let the astronaut onboard climb between the two pressurized volumes. Ideally there would have been a tunnel directly between the two when they were docked normally, but the Mercury’s retrorockets were in the way. So as designed, this craft would have had to take one of two approaches. Either the Mercury would stay in place and an inflatable half-toroid would join the hatch on the side of the capsule with the hatch on the secondary module, or else the Mercury would bend backwards on a hinge until its side hatch actually touched the side of the new capsule. Only then would the astronaut be able to clamber from one to the other.

NASA said no thanks and nothing ever came of it, but the basic idea seems to have evolved into the Manned Orbiting Laboratory for the US Air Force. Gemini was called “Mercury Mark II” after all, and was configured so that a tunnel could run between its base and any add-on modules behind it. It was quite natural, then to take the concept and adapt it to the newer, more capable spacecraft.

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4 thoughts on “Sidebar: The Mercury Space Station

  1. Great post, especially the volume threshold for space station-hood. Ever notice how there were so many more concepts for “space stations” than for other piloted mission types, like lunar landings? Or is that just my own bias showing?

    • I think you’re right, and if I had to guess it’s the confluence of several things:

      – The US didn’t have a long-term space station until the dawn of the 21st century, pace Skylab, so there was room for the US’ space contractors to propose station after station in the hopes of getting one to stick.

      – For a long time it was assumed that you would build a station before you would go to the Moon, so there’s a raft of Stations without Bases but relatively fewer Bases without Stations.

      – The US settled on Apollo and the Space Shuttle to such an extent that there’s been comparatively little room for other spacecraft and comparatively little money for Moon bases and Mars missions. But stations hit the sweet spot of being relatively cheap while also not stepping on the Apollo and STS programs.

  2. Does anyone have the complete McDonnell proposal in PDF format? We keep reading about it, but no one has anything more than about four pages of the two drawings and the weight and size numbers.

    • I don’t think so, no. I combed the NTRS for them (back when it was up) and didn’t even come up with the abstracts. Either they’re a long way back in the NASA scanning queue, they’re in the possession of Boeing after McDonnell’s successive mergers with Douglas and them, or they’ve been lost.

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