I have to admit that I was stumped.
Many years ago, I became disillusioned with mainstream space activist groups whose primary strategy to achieve their goal (space settlement) seemed to be blinkered and unwavering support of almost anything that NASA said it wanted to do. This was because, when I looked at NASA's stated plans, I couldn't see any clear path from them to one that would achieve that goal. The activists' philosophy seemed to be that it was better to have any manned space program, no matter how orthogonal -- even counterproductive -- to their objectives, than none at all.
There are many reasons that the road to a spacefaring civilization doesn't go through the International Space Station, and I don't have column space to recount them in their entirety here. But briefly, the station was designed primarily for microgravity research (search) (a use for which the hype has far exceeded the actual results to date). For technical reasons, this makes it unsuitable for other uses, such as a transportation depot, or a hotel. In the '80s, when we looked at all of the conflicting requirements inflicted on our unitary (of necessity, because no one ever conceived of multiple platforms) space station concept, we said that it was like designing a hospital and clean room in the middle of Grand Central Station (search).
But even if its design were flexible enough to accommodate new future uses, the fact remains that it's in an orbit almost useless for most needs, for purely political reasons, in a decision made a decade ago.
In 1993, in the face of continual schedule delays and budget overruns caused by program mismanagement and multiple redesigns (partly a result of the requirements schizophrenia described above), it was on the verge of being cancelled. The Clinton administration, like most administrations, never had much interest in the space program, but it latched onto the idea of using it as a means of cooperation with the newly-democratizing Russia. It didn't matter that it was space, except that once again, as in the space race of the '60s, that was the only area in which the Russians had technical expertise to (this time) cooperate (as opposed, then, to compete).
Of course, what was important to the administration was not building a space station, but finding a convenient pot of money with which to provide foreign aid that wouldn't come out of the State Department's budget. So the program was restructured to include them, and with the support of the administration to rein in wavering Democrats, it survived a congressional decision by a single vote.
That was the point at which it became clear to many that the program had very little to do with actually building a useful space station, but for those desperate to preserve "the manned space program," the Faustian bargain was acceptable. They were willing to kill the program (in terms of ultimate utility) in order to save it.
The problem is that, because Russia cannot launch into low-inclination orbits (those nearer the equator) from their high-latitude launch sites, we had to put the station in a high-inclination orbit. It's now in a poor (essentially useless) location to serve as transportation node for more ambitious manned flights to the moon or beyond.
Some have suggested that it could be the initial hotel for space tourists. There are a couple of problems with this.
First, because of its high inclination, it is much more costly for us to get to (payload is greatly reduced for high-inclination orbits). But the real problem with that idea is that it wasn't designed for that, and with the noise, and cramped quarters, and paucity of windows, it's far from an ideal space resort. That might be all right, if it has no competition, but almost as soon as launch costs get low enough to allow this to be a viable use for it, they'd also become low enough to allow the construction of a dedicated tourist hotel, made affordable by affordable launch, and custom designed to the market.
If we solve the launch cost problem, building useful space stations in useful locations will become a trivial task, relative to attempting to jury-rig the existing one. If we can't solve the launch cost problem, then the program is probably not worth continuing.
No, the ISS is probably a technological dead end, even if its construction is eventually (even in the face of the travails of the Shuttle program) completed. Like the Shuttle, what lessons we will learn from it will be mostly negative -- how not to do things, and that applies not just technically, but programmatically. It will not be our springboard to the stars, or even back to the Moon. Sometimes in this life, there are lemons from which one cannot even make lemonade.
Sadly, in retrospect, my host's question reminds me of the Simpsons episode in which (in a satire of the beloved musical The Music Man), the town of Springfield builds a monorail, and the project, using substandard parts and training, goes Terribly And Hilariously Wrong.
At the end of the episode, we hear Marge's voice intoning: "And that was the only folly the people of Springfield ever embarked upon. Except for the Popsicle stick skyscraper. And the 50-foot magnifying glass. And that escalator to nowhere.''
As the script description says, "The magnifying glass focuses the sun's rays on the skyscraper, igniting a fire. Meanwhile, people rise to the top of a huge escalator, only to fall off when it reaches the top."
Substitute American people for Springfield citizens, Congress for Mayor Quimby, and a succession of NASA officials for slick, fast-talking monorail salesman Lyle Lanley. The result is a frustrating, and all-too-valid metaphor for our nation's manned space program over the past three decades. In a sense, we've built our own escalator to nowhere.
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.