Sunday, September 14, 2008

Next Step Foreward

At least for the next couple of decades, the number of people in space at any given time is likely to remain a handful. In the next decade the number of 'Murricans up there at any given time may be in doubt, sad to say. I will bend my rule of avoiding politics here enough to say that it should be no surprise that an administration and party that have screwed up everything they touch on Earth should screw up outer space as well.

Past midcentury we can hope and expect something better than that, but the number of people in space may grow quite gradually through this century. Practical spacelift is likely to remain expensive because it remains near the limit of the practical: We can just do it. Nor is there a practical role - yet - for very many people up there. The ones who do go up there will be much more productive than imagined in the rocketpunk era, a space station crew of ten doing the work that a crew of 100 would have been needed for in rocketpunk.

No tech revolution is needed for substantially cheaper orbit lift. What is needed is traffic demand sufficient to keep a dozen or so fully or mostly reuseable spacecraft, probably two stages to orbit (TSTO), flying on a weekly or at least monthly schedule. That is about the minimim needed for production and operating efficiencies - say, 100-500 launches each year, each one carrying perhaps 5 tons of equipment or 5 passengers to low Earth orbit (LEO). Supposing that 80 percent of launches are freight payloads, total annual traffic to LEO each year is thus in the range of 400-2000 tons and 100-500 people.

This is a lot! Current world demand for orbit lift is less than 100 tons to LEO each year (equivalent to about 20 tons to geosynch orbit), which is why we don't already have a space transportation system like this. No one buys trucks and buses that will run mostly empty. That is why space growth is likely to be gradual - taking off at the critical point at which launch demand justifies economies of scale. At a guess, the transport system outlined above might cost $25 billion per year to operate, corresponding to a lift cost of $5 million per ton or passenger in the early years - compared to some $20 million now - and falling to $1 million per ton/passenger as the transport system matures.

For comparison, the current NASA budget is $17 billion. Supposing that a third to a half of total space spending is on the orbital transport system, about three or four times the NASA budget, from all sources, is needed for a space effort large enough for efficient transportation.

Note that nationalistic competition in space may help in the short run but probably hurt in the long run. On the one hand, nationalist hype fuels budgets, at least for a while. On the other hand, if everyone wants their own orbital transport system, the efficiencies of scale needed for an efficient one get strangled in the crib. This is more or less what happened in the first Space Age, resulting in a burst of progress followed by relative stagnation. A plausible outcome might be two or three launch services worldwide, each run by some bloc or consortium.

Militarization of space, all too plausible a prospect, is a fast trajectory to stagnation. One thing they had most wrong in the rocketpunk era was the presumed high-ground advantage of spaceships against forces on a planetary surface. Spacecraft in low orbit are exceedingly vulnerable to 'ambush' by surface-launched antisatellite missiles (ASATs). These do not need to reach anything like orbital velocity. All they need to do is loft a kinetic target seeker on a suburbital trajectory, so that the spacecraft slams into it. The target's own orbital velocity does the rest. There are countermeasures, but they are expensive and complicated, whereas ASATs are, by space standards, simple and cheap.

War in space, at least between Earth powers, won't be rival interplanetary armadas, it will be waves of ASATS shredding everything in near-Earth space ... and conceivably giving Earth a permanent ring of shrapnel that makes space travel impossible. Orbital shrapnel never fully disperses, or only on a time scale of centuries or longer.

But let us suppose that by c. 2050 an efficient transport system is in place, and perhaps 200 people each year are going into space. We can guesstimate the average number up there at any given time. Half the travellers, say, go up for short stays of about a week - in effect as tourists, even if officially they are 'inspecting.' That means on average just a pair of quasi-tourists in space on a given day. The other half of travellers, however, are going up on longer rotations averaging perhaps six months, so typically there are 50 long-term workers in space at a given time. Perhaps half of them, a couple of dozen, are assigned to a space station; another dozen are on the Moon, the final dozen are aboard one or two interplanetary missions.

By rocketpunk standards this presence is decidedly modest, but it means sending out human interplanetary missions at about the same pace we now send out robotic ones - more or less a mission or two every optimum transfer window. Each will be a comprehensive expedition: That is why you're sending people. Robotic exploration won't cease! In fact the human missions will surely each carry a load of robotic probes as well.

The exploration of Mars will not go the way we imagined it in the rocketpunk era. The crew of the first Mars landing won't be looking down from their orbiting ship, scouting out possible landing points for the first time. They'll be making the final judgment call after decades of robotic exploration that has already begun. Likewise we won't send human missions off at random into the asteroid belt; we will send them to explore bodies already identified as of particular interest.

I've said nothing of deep space industry, because it belongs almost by definition to the next period, when exploration gives way to development. We don't know what those industries might be yet, because we've scarcely begun to explore. But the first such industry is likely to be propellant, by far the largest consumable of space travel. When it is cheaper - including development cost - to crack and tanker oxygen from the Moon to LEO rather than ship it up from the surface at $1 million/ton, we will do so. (Why oxygen? It can be cracked from lunar rocks, and accounts for most of the mass of hydrogen-oxygen rocket fuel.)

Who will pay for all this, and why? I'll talk about that next post.

Sunday, September 7, 2008

A Farewell to Rocketpunk?

No, not to this blog; in spite of my failure to update it for though all of August, it is staying right here. Nevertheless time, which keeps everything from happening all at once, does march on, and in the fifteen months or so since I launched it, Rocketpunk Manifesto has evolved along with my thinking about space, into something rather different from what I originally conceived. The term 'rocketpunk' was coined, by analogy to steampunk, to denote a style of retro-SF that evokes science fiction of the mid-20th century, especially the first hard SF, a la Clarke and Heinlein, the Willy Ley / Chesley Bonestall illustrations, and so forth.

I am not aware that any such rocketpunk has actually been written, beyond a pair of very short snippets here. It is a bit problematic to write, because the 1950 era is not yet quite remote enough to be quaint the way the turn of the last century is. There are no aether ships in rocketpunk - instead it has shuttles and space stations resembling more-developed versions of the real thing. (Until you find out that the ship's computer takes up a whole compartment, requires binary input/output, and has rather less power than my trusty old HP-10C calculator.)

Since I started this blog, I have found myself more often than not using 'rocketpunk' to denote the original item, or the whole period in SF just prior to the space age, the 'rocketpunk era.' More to the point, however, I have started to rethink our actual future in space. Over the years I had become something of a space pessimist, at least as regards human spaceflight. It is expensive and likely to remain so for a considerable time to come. People involved in the very successful program of robotic interplanetary exploration have a legitimate complaint that human spaceflight is a budget eater, and in recent decades its tragedies have been more spectacular than its triumphs.

Underlying this skepticism, however, was a vague sense that if we couldn't have all the Cool Stuff we expected in the rocketpunk era and the first decade of the space age, then the whole thing was an anticlimax and scarcely worth doing at all. This, on belated second thought, is a somewhat blinkered perspective. The value and potential of human space exploration does not and certainly should not hinge on whether it leads to a future that resembles stories that Heinlein wrote fifty or sixty years ago. That would be roughly comparable to saying that archeology is a wasted effort because it does not resemble Indiana Jones movies.

So what might we expect from and in space in the midfuture? This is the period extending roughly from 2050 to 2200 - starting, that is, a technological and policy generation or two beyond the present, and extending about as far as we can extrapolate without getting lost in a speculative haze. Not by coincidence it is roughly the period in which much of the original rocketpunk was set.

To start with, however - and continuing the theme of the last post - one thing that will probably not happen is space colonization, at least in anything like the classical form we're all familiar with from rocketpunk-era science fiction. Space colonization, at least in American SF, was the ultimate Bat Durston: a recapitulation of the American frontier experience, often culminating in a repeat of the American Revolution in space. The appeal of this is obvious. (At least to those of us in the US; elsewhere in the Anglosphere, including the Great North and especially the Scepter'd Isle, you might understandably have another perspective.)

Heinlein was the great offender here, and perhaps no surprise, since he was only about a generation removed from the 'closing of the frontier' in the United States. Heinlein's Solar System was retro even for the 1950s era, with its habitable Venus and semi-habitable Mars - though in Farmer in the Sky he had Ganymede* being terraformed and settled by, well, farmers. But in the course of the 20th century the impulse toward homesteading has pretty much disappeared. Although immigration to the US is at a historic high, the immigrants no longer come to claim forty acres and a mule. They come to find work in an existing complex economy. Farming is just about the last reason for going into space.

People will go into space to work; in time, if going there becomes cheap enough, they will go there on vacation. Neither calls for colonies as such. If a research station on or orbiting Mars (or wherever) grows large enough, a sort of college town might take form around it. (Though this has not happened yet in Antarctica.) Any such development is likely to be gradual and ambiguous. Some people might retire there, if they can clear the economic and administrative hurtles.

Having and raising children off Earth is much more problematic. A space station or base is not a particularly good place to have kids running around - as Ken Burnside puts it, children are highly efficient entropy generators. Even more serious is the question of whether children raised off-Earth could later adapt to Earth gravity. (Any space structure intended for really long-term habitation will need to be spun, but probably at a good deal less than 1 g.) It is fine to say that the children of thriving space communities might not even wish to visit Earth, but there's a bootstrapping problem, because the first space communities will be more nearly outposts. So, for a good long time to come, pregnant women will probably be bundled back to Earth. The time constraints of interplanetary travel mean that some children in the midfuture will likely be born in space, but the sooner they adapt to Earth gravity the better.

Through the midfuture, then, there is likely to be nothing much resembling colonization, or any true permanent space population, any more than there is in Antarctica. If you were raised on rocketpunk-era SF, as I was, this thought is probably vaguely depressing, but there is no reason it should be. We have traveled the seas for thousands of years; the sea has played a central role in many cultures, and it has been a setting for adventure since before the Argo - all without permanent sea-living populations growing up, all without more than a relative handful of people being born at sea, and with no sea-living population ever developing. There is no essential reason why space should be any different, just because no habitable islands are in reach of foreseeable technology.

* Ganymede lies within the intense Jovian radiation belts, making it difficult even to visit, and it also seems to be the least interesting of Jupiter's larger moons. The outer big moons, Callisto and especially Europa, now seem to have more of a future. One more way that the real Solar System differs from the old rocketpunk version.