Skylab Design Evolution

The modular building block approach to designing Skylab

Sep 16, 2023

Exploring the intersection of spaceflight history, pop culture, and art.

Creating Space continues the commemoration of the fiftieth anniversaries of the Skylab missions by looking at the design evolution of the workshop. The Skylab space station, as we know it, began as little more than an empty rocket stage, and grew to a purpose-built cluster of scientifically-focused modules.

Skylab Cluster Configuration

In earlier posts about Skylab’s beginnings, I described the initial configuration design that used an Apollo Saturn S-IVB stage that would be fully fueled at liftoff – the so-called ‘Wet Workshop’. Before Skylab would ultimately fly in 1973, the workshop’s design would evolve, adding specialized equipment modules intended to support specific scientific goals. In this post, I delve into the evolutionary path that began with the empty S-IVB stage (after its fuel was expended) and progressed to a full cluster of modules.

If you missed the first two Skylab posts, you can find them here:

Here Am I Sitting in a Tin Can

In its very early conceptual stage, the idea of a space station, or workshop, derived from an empty rocket stage, was hardly more than a tin can in which the astronauts would float around freely.

*Illustration from a report on an orbital S-IVB spent-stage experiment support module feasibility study, 1966 (Credit: Douglas Aircraft Company, Inc, NASA.)*

Dr. Gary Kitmacher, communications and education mission manager for the International Space Station program put it this way in a 2020 oral history interview:1

“A lot of the early ideas were not for a space station at all, they were simply going to open up a hatch and the astronauts would be able to go in and essentially be able to do an EVA inside of this upper stage.”

Jack Lousma, the Command Module Pilot on the second crewed mission to Skylab, described in an interview, in August 2023, how the astronauts would access the vented third stage workshop volume.2

“It was just going to be an empty hydrogen tank which would launch a Command Module into space and we were going to undock from it, turn around, and take about thirty-nine bolts off and go into this third stage of the Moon rocket that just launched us into space.”

Dr. Kitmacher, in the same 2020 oral history interview, elaborated on the difficulty the astronauts might have removing the hatch with the thirty-nine bolts:

“Von Braun and George Mueller, who was the Associate Administrator, dove into the water tank at the Marshall Space Center and actually tried to unbolt the hatch on one [of] these Saturn upper stages and they were unsuccessful. And they said there was no way you'd ever be able to get it open in orbit.”

Building on a Modular Approach

It was from this sparse, and somewhat impractical, starting point that the workshop configuration began to grow into something more useful. An underlying objective of NASA administration, primarily to keep costs down, was to use a modular, or building block, concept and to use existing hardware as much as possible.

This 1967 photo of a model shows that one of the first additions to the S-IVB stage would have been a docking module. Here we see an Apollo Command and Service Module (CSM) docked to a cylindrical module extending forward from the top of the S-IVB. This would have addressed the problems posed by the large bolted-on hatch on the hydrogen tank mentioned earlier.

*Model of Apollo Applications Spent Stage Workshop with docking module, 1967 (Credit: North American Rockwell Corporation)*

After the docking module, science would be a driving force in determining the form of the workshop. This 1967 press illustration from the Seattle Times3 indicates some scientific instruments or perhaps utility equipment placed adjacent to the docking module. There is also a rudimentary science workstation depicted within the empty hydrogen tank, albeit likely a product of the illustrator’s imagination.

*Illustration of a Saturn fuel tank-based space laboratory, 1967 (Credit: Seattle Times)*

One of the first large modular additions to the ‘tin can’ stage configuration studied was a spent-stage experiment support module (SSESM) which would sit atop the S-IVB hydrogen tank and inside the Lunar Module Adapter (SLA) petals. Its scientific equipment would surround the docking airlock module in a toroidal arrangement. This image also shows that designers were beginning to refine their ideas for what would be placed inside the empty fuel tank volume.

This arrangement would later be supplanted by a more modular building block approach that would require multiple launches of Saturn IB rockets.

*Inboard profile drawing of an early Skylab configuration (Credit: NASA)*

Science Rules

The major areas of scientific emphasis intended for the Skylab program were solar astronomy, Earth resources and materials processing (so-called “applications”), and long duration mission studies including habitability, medical experiments, and work effectiveness.

*Skylab Program Major Areas of Emphasis (Credit: NASA)*

Here is where the building block approach truly came into play. As originally planned, Skylab would be assembled in stages, launching specialized modules on a series of Saturn IB boosters. Initially, an uncrewed foundational assembly would be launched which consisted of the S-IVB stage, an airlock, and a docking adapter.4 Then, certain modules would be launched on additional Saturn IB rockets and attached to the workshop via one of the several docking ports. Some flights would bring equipment to be installed inside the main workshop volume.

The first add-on module to be flown would be an Earth Mapping and Survey System (M&SS) for studies of our planet. This would actually be launched ahead of the main workshop, on a Saturn IB, together with a crewed Apollo CSM. The crew, with its CSM docked to the M&SS, and minus its expended S-IVB booster stage, would rendezvous with the separately launched orbital workshop and attach the M&SS to one of the docking ports.5

*Apollo CSM docks the Earth Mapping and Survey System (M&SS) to the orbital workshop’s docking module (Credit: NASA)*

After the M&SS was attached to one of the side-facing docking ports, the CSM would then dock to the top-most port and use its main propulsion engine to boost the entire assembly into a 200 mile high circular orbit.6 Though not explicitly stated in the reference material I have read, this seems to imply that the Saturn IB booster did not have adequate thrust to place the workshop stage into the desired orbit, even with the contribution of the “wet” fueled S-IVB stage.

*Apollo CSM docks to the end of the orbital workshop (Credit: NASA)*

One of the strangest applications of the building block philosophy, where existing Apollo hardware would be leveraged to maximum extent, was the free-flying Lunar Module-based solar telescope – the so-called Apollo Telescope Mount (ATM). The Apollo Lunar Module was, of course, designed for the very specialized purpose of landing astronauts and equipment on the lunar surface. It’s structure, life-support equipment, propulsion and control systems, and instrumentation were all optimized for operation in the one-sixth gravity environment of the Moon. In a very real sense, this made it overdesigned for use as a free-flying telescope. But, since the engineering and development had been previously worked out by NASA and Grumman engineers, it was apparently viewed as offering cost and schedule advantages over creating a brand new purpose-built orbital telescope.

As first envisioned, a Lunar Module ascent stage with some modifications to instrumentation and controls to support its new role, would be fitted with a legless shell of a descent stage. The interior of the descent stage would be outfitted with a telescope and sensors for solar observations. To provide power, four long rectangular arrays of solar panels would extend out from the base of the descent stage in a cruciform arrangement, resembling the blades of a windmill.

*Windmill-like free-flying Lunar Module-based solar telescope (Credit: NASA)*

*The Apollo Lunar Module derived telescope mount would look similar to this configuration diagram. (Credit: Perkin Elmer)*

Early plans were to fly and operate the LM-based telescope while docked to a Command and Service Module.

*The Apollo Lunar Module derived telescope mount docked with the Command and Service Module. (Credit: NASA)*

While not in operation, the LM telescope would be separated from the CSM, and both docked to the multi-port docking adapter.

*The Apollo Lunar Module derived telescope mount and the Command and Service Module prepare to dock with the orbital workshop. (Credit: NASA)*

Here is a very interesting photo of a full-size mock-up of the upper end of the Skylab workshop cluster showing a very out-of-place looking Lunar Module docked to the multi-port docking module.

*Engineering mock-up of the Apollo Lunar Module derived telescope mount docked to the orbital workshop. (Credit: NASA)*

When I see this photo, with the dark, empty, “eyes” of the Lunar Module windows and the kit-mod-looking descent stage, I can’t help but be reminded of Sid’s baby-headed, crab legged Frankenstein mash-up in Pixar’s ‘Toy Story’. Apologies for that indelible image now inserted into your head.

When completed, the final Skylab workshop assembly might have looked something like this illustration.

*Apollo Applications clustered Saturn orbital workshop configuration, 1967 (Credit: NASA)*

In upcoming posts, I will describe the final Skylab configuration as it flew in 1973, and share a large scale contractor model of the “Wet Workshop” Cluster configuration.

ACKNOWLEDGEMENT:

I want to extend a note of gratitude to the author of much of the source material I used for this post. David S. F. Portree writes an incredible blog called ‘No Shortage of Dreams’ that covers, in great detail, the early planning for Apollo and other U.S. space program proposals, many of which never left the drawing board.

There are a select few space history authors that can tap directly into my Space Geek veins. David’s well-researched writings are definitely in the upper echelon of those people. Thank-you, David, for many years of telling the stories of space that are often overlooked in space history books.

I highly recommend reading David’s blog, ‘No Shortage of Dreams’.

Art News

My space-inspired artwork, Moonlight Dreams, continues its run as part of the Art+Flight celebration at the Museum of Flight in Seattle, Washington. The celebration runs through January 7, 2024.

*Moonlight Dreams (right) on display at Art+Flight*

If you haven’t yet read about the exhibition and my artwork that is displayed, refer back to the following two posts to get filled in on the facts.

Art News from Moonlight Dreams post, June 4, 2023
Art News from The collectSPACE Insignia post, July 8, 2023

Stop by if you are in the Seattle area and check out the clear brilliant colors of my metal prints first hand. Prints are available for purchase in the museum store, and you can always find Moonlight Dreams and more of my artwork for sale at my online shop.

Art+Flight is free with Museum admission.

Open Daily, 10:00 AM to 5:00 PM

Admission FREE 5:00 PM to 9:00 PM the first Thursday of every month.

The Museum of Flight is located at 9404 East Marginal Way South, Seattle, WA 98108.

*Art+Flight logo (Credit: Museum of Flight)*

*Dave Ginsberg - Pixel Planet Pictures - Creating Space*

I’m Dave Ginsberg, the artist behind Pixel Planet Pictures and writer of Creating Space.

I am an artist and a creative engineer with a love for teaching and passions for spaceflight, astronomy, and science. My space-inspired art portfolio can be found at pixel-planet-pictures.com. You can also follow me on Instagram (pixelplanetpics).

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