Our manned space infrastructure is extremely fragile — even brittle.

NASA just found a problem with the Space Shuttle Orbiters Atlantis and Discovery. They have hairline cracks in some jackets in the main propellant lines.

These aren't cracks in the lines themselves, so there's no danger of a leak of oxygen or hydrogen, but they could result in a small piece of metal getting ingested into the engines, which could potentially cause anything from a premature engine shutdown to a turbopump explosion.

That could be a pretty spectacular show, considering that for the few brief minutes it operates during each flight, each of the three fuel turbopumps generates about 70,000 horsepower (or about fifty megawatts — equivalent to a small power plant or dam).

If it happened during flight it would be comparable to the Challenger disaster. If it happened on liftoff, it could take out the whole pad, along with the Shuttle and crew. Even in the event of a simple engine shutdown early in the flight, a Return To Launch Site (RTLS) abort would be exciting, and dangerous, and it's never been attempted. No matter what, it would make for a very bad day for all aboard.

NASA doesn't yet understand how the cracks got there (my own "recovering engineer" guess is fatigue from thermal cycling, as they're repeatedly soaked in very-cold liquified gases over several years); how long they've been there; and whether or not the other two vehicles have them. As a result, they have prudently grounded the entire Shuttle fleet indefinitely.

Indefinitely, in this case, does not mean that it will necessarily be a long time, but that they can't say how long it will be. This means that Columbia's mission to the space station next month will almost certainly be delayed until they do have some answers.

I've written before about the high costs of space due to lack of economies of scale, but our minimal activity level causes other problems as well. It makes it difficult to afford a robust and resilient space transportation infrastructure.

In 1979, when a DC-10 literally lost an engine and crashed in Chicago, the whole McDonnell-Douglas DC-10 fleet was grounded. But this didn't shut down the airline industry because there were hundreds of aircraft of many other makes and models which weren't affected.

In contrast, we learned with the Challenger breakup the danger of relying on a single launch system. With a small number of vehicles, grounding means putting all activity on hiatus. A loss of an Orbiter would constitute the loss of a quarter of our fleet. The loss of another one after that would be another third of the remainder. And grounding the fleet to avoid this may result in more delays to the beleaguered space station program.

NASA has studies underway to look at solutions to this problem, such as the Space Launch Initiative, or the Alternate Access to Space program. But these programs seem to be stuck in the same mode of thinking that gave us Shuttle. People talk about "the" Shuttle replacement, or "the" next-generation launch system, as though there will be only one, because no one can imagine a market or funding for more. And all the focus remains on technology and vehicle concepts, which are beside the point.

No one in the government seems to recognize our real problem, which is the currently infinitesimal market size for space transportation. NASA continues to pay the traditional aerospace contractors for traditional solutions, and ignores the fact that we need a diversity of approaches and providers. Such a diversity can only be supported by a large, vibrant and growing commercial demand for space transportation services.

There is an old tale, about "for lack of a nail...a kingdom was lost."

As long as we, as a nation, refuse to acknowledge the problem with our space markets and approaches, we will remain in our current state of fragility, in which the fate of a multi-billion-dollar space station — which, for all of its cost, can only support three people — is held hostage to the whims of microscopic slivers of metal in frigid propellant ducts.

Milestone In Low-Cost Launch

Another milestone in rocketry was achieved Monday. For the first time in history, a pure rocket-powered aircraft performed a touch-and-go landing. This maneuver, which involves landing on a runway and then taking off again before speed is slowed too much, is one that every student pilot practices, multiple times, because it builds skill in both takeoff and landing. But until this week, it had always been performed with an airbreathing engine.

XCOR Aerospace has now demonstrated that it's possible to do it with rocket power, which required the ability to routinely and reliably cut power for the landing, and then restart the engines for the takeoff.

This implies that if they are not available now, engines will be available very soon that will allow affordable rocket races, trips to suborbit and (eventually) rides into orbit itself on a routine basis. This could provide the foundation for a whole new transportation industry.

Another Close Call

An asteroid came within 70,000 miles of earth last week--the closest known approach in several years. That's just a few earth radii away.

It was big enough to destroy a major city. As Jay Manifold has pointed out, if it hit a major city on the Indian subcontinent (or anywhere in the region), it might have touched off a nuclear war, given the hair-trigger situation over there.

We really do need to get more serious about these things.

Letters

I got a number of emails on last week's column on international cooperation in space. I've responded to them at my weblog.

But, as usual, I need to clarify. I don't believe that we should never have international collaborations for space activities — there are many examples in which this resulted in cost-effective success.

My point was that when we do so, we should do it because it's the best way to achieve the space goal, rather than simply using some space goal as an excuse to cooperate with other countries. And in general, when we use space to serve other agendas, we end up with, well...space stations that cost tens of billions of dollarsc but can support only three people and are years behind schedule.

Rand Simberg is a recovering aerospace engineer and a consultant in space commercialization, space tourism and Internet security. He offers occasionally biting commentary about infinity and beyond at his Web log, Transterrestrial Musings.

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