Saturday, May 14, 2011

What Might Have Been, Part I

We are currently counting down to the last flight of the Space Shuttle program. Just over thirty years ago, Columbia roared into the Florida sky for the first time; late this year or early next year, Atlantis will be the last to touch down on Runway 33.

Others will write about what the end of this program means. I may be one of them. But not today. Instead, I want to spend some time imagining what else might have been. Today, we're setting the Way-Back Machine to 1968, and take a quick peek at NASA's post-Apollo plans.

By 1968, it was fairly clear that they would probably take a swing at the first Moon landing sometime in 1969. Having hit the mark that President Kennedy set for them in 1961, they needed another goal to keep as many of their staff gainfully employed as possible. They had already been working on a set of post-Apollo options under the label Apollo Applications Program, but were also working on much more ambitious plans. What they presented to the Nixon Administration in 1969 was an ambitious, integrated program that included a reusable space shuttle, nuclear space tugs, a space station, and a manned mission to Mars by 1986.

That's not the might-have-been I want to look at. Going down that road requires you to imagine that Congress would be willing to fund NASA at its peak levels for another ten or fifteen years. That was never going to happen. But what might have happened is that a more modest program could have been proposed: one that built on technology that the American taxpayer had already bought and paid for. The question before us is, what could be done with a second production run of Saturn boosters and Apollo spacecraft? Further, what can be done with a fairly modest investment in additional spacecraft research and development?

Some of this ground had already been covered by the Apollo Applications Program design studies. For our purposes, though, only two pieces of AAP will be of interest to us: the Wet Workshop space station, and the Dry Workshop space station. While a lot of AAP's focus was on extending Apollo lunar technology towards building a semi-permanent or permanent base, the additional R&D funding to make that happen probably wouldn't be forthcoming. But there are practical considerations to contend with as well. As it turns out, three days is about as long as the A7L space suit could last in the lunar environment. By the end of the Apollo 17 moonwalks, the joints in Cernan's and Schmitt's suits were beginning to seize up from the moon dust. It just wasn't realistic to expect this suit to stand up to a full week of daily use, much less a month or more. This is a problem that could be cracked, given enough research focus; but the funding required to solve that problem just isn't forthcoming in the time frame we're talking about. So, as a practical consideration, we're going to restrict our consideration to things we can do without having to contend with dust.

This is the problem that AAP was faced with. With landings taken off the table, what's left? The only thing left is long-duration space flight. Which is why this alternative program centers on two different space station platforms: the Wet Workshop, and the Dry Workshop. Each one has its own strong points, and its own drawbacks.

The key advantage of the Dry Workshop is the reason why it's the one we actually built and flew in the Skylab program: it's a far better, and far more well-equipped research platform. More than one crew can use it. And you don't have to worry about packaging anything to withstand exposure to cryogenic propellants during launch. But the drawback to a Dry Workshop is that you can only put it in one place: in low orbit around Earth.

When you're talking about a Wet Workshop, the term "space station" may be a bit of a misnomer. You're using the liquid hydrogen tank of the spent S-IVB stage as living space for your crew, but the spent S-IVB stage isn't necessarily in low Earth orbit. There are any number of mission profiles. It's possible to put an empty S-IVB stage in orbit around the Moon, for example, giving the crew a place to stay while they spend a month or two doing detailed observations from lunar orbit. Or, it's possible to put an empty S-IVB stage in an inclined 24-hour period orbit, where it will trace out a figure-8 on a globe, giving you the opportunity to make observations of the same region of Earth over an extended period of time. The most ambitious mission profiles involve interplanetary fly-by trajectories to Mars or Venus. You can't carry as much equipment as you could with a Dry Workshop. But, the equipment can be more closely tailored to the specific mission at hand. It's a marvelously flexible concept.

We know that such a thing would have been possible. But would it have been affordable? Probably so: between 1968 and 1981, about $30 billion was spent on STS research and development. The marginal costs for a Saturn V launch were $185 million in 1969, and $55 million for a Saturn IB in 1972. A second production run of Saturn V boosters, 15 units, would run $2.775 billion; and a second production run of 30 Saturn IB boosters would run $1.650 billion. Skylab cost $2.2 billion, so we can guess that the wet workshop would cost at least as much. Call it $5 billion, for R&D for the first unit of each, and $500 million per unit thereafter. Fiscally, it looks doable.

Next time, we'll attempt to unpack the schedule, to see how much might have been done in the 1970s. And we'll also take a look at the downside: what we'd have given up on by going down this road.

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