The lack of resiliency of NASA’s transportation plans is a point that I’ve made often. For instance, in The Path Not Taken, five years ago, I wrote:

The chief problem with the Bush vision for NASA is not its technical approach, but its programmatic approach—or, at an even deeper level, its fundamental philosophy. This is not simply a Bush problem, but a NASA problem: When government takes an approach, it is an approach, not a variety of approaches. Proposals are invited, the potential contractors study and compete, the government evaluates, but ultimately, a single solution is chosen with a contractor to build it. There has been some talk of a “fly-off” for the Crew Exploration Vehicle, in which two competing designs will actually fly to determine which is the best. But in the end, there will still be only one. Likewise, if we decide to build a powerful new rocket, there will almost certainly be only one, since it will be enough of a challenge to get the funds for that one, let alone two.

Biologists teach us that monocultures are fragile. They are subject to catastrophic failure (think of the Irish potato famine). This is just as true with technological monocultures, and we’ve seen it twice now in the last two decades: after each shuttle accident, the U.S. manned spaceflight program was stalled for years. Without Russian assistance, we cannot presently reach our (one and only) space station, because our (one and only) way of getting to it has been shut down since the Columbia accident.

The lesson—not to put your eggs in one basket—hasn’t been learned. The Air Force is now talking about eliminating one of the two major rocket systems (either Boeing’s Delta or Lockheed Martin’s Atlas), because there’s not enough business to maintain both. The president’s new vision for space proposes a “Crew Exploration Vehicle” and a new heavy-lift vehicle. The same flawed thinking went into many discussions in the last decade about what the “shuttle replacement” should be.

And it’s not a new idea. As Ron Menich points out in today’s issue of The Space Review:

…the following wording appears as Groundrule A-1 in the Space Transportation Architecture Study (STAS) from the late 1980s:

“Viable architecture will be based on a mixed fleet concept for operational flexibility. As a minimum, two independent (different major subsystems) launch, upperstage and return to Earth (especially for manned missions) systems must be employed to provide assured access for the specific, high priority payloads designated in the mission model.”

The words “independent (different major subsystems)” can help us to see a value that international partners can provide in large space architectures. Soyuz was not grounded at the same time that the Shuttle fleet was after the Challenger and Columbia disasters, and a future failure of, say, a Progress resupply vehicle would likely have no effect on the HTV’s ability to supply the stations. The fact that different nations developed their own independent launch capabilities has had the happy side effect of increasing redundancy, even though the original motivations (such as political or national pride goals) for developing those separate systems were far removed from reliability considerations.

I worked on (and later managed) that study for Rockwell, which was kicked off (at least for Rockwell) on the day that Challenger was lost.

And about three months after the Challenger loss, there was a Titan-34D accident at Vandenberg (the second consecutive failure for that vehicle), which shut that program down as well, leaving the US with no heavy-lift capability for a period of time. So even dual redundancy isn’t always enough. So all through the eighties, on STAS, on Advanced Launch System, and other architecture studies, it was a groundrule that we have a mixed-fleet capability in any future plans.

But even though Ron’s article says nothing new, apparently the lesson remains unobvious and unknown to the people who planned Constellation. As they did with the requirements to be affordable and sustainable (and in fact having redundancy is one of the ways of making it sustainable), they completely ignored the need for redundancy in the design of the architecture, to the point that they didn’t even attempt to explain why their architecture didn’t have it. It’s in fact frustrating that this wasn’t an issue that even came up in Augustine deliberations. No one wants to talk about it, even though it’s the biggest Achilles Heel in space transportation, as evidence by the fact that once we shut down Shuttle, we’ll have no means of getting to ISS independent of the Russians (at least NASA won’t — SpaceX and ULA may be another matter). And the reason, I suspect, that no one wants to talk about it is that it is a fatal flaw in their plans, and one to which they have no sensible response. If people admitted that this is a requirement, it drives a stake through the heart of heavy lift, once and for all. At least, that is, until there is enough traffic to justify the cost of developing and operating not just one such vehicle, but two.

And of course, every day that they delay doing the sensible thing, and figuring out how to carry out their plans with the vehicles they have, is another day of delay in reaching that far-more-distant goal.