Very much ado has been made of Newt Gingrich's recent assertion that we should reinvigorate our space program to the extent of establishing a moon base and perhaps mount expeditions to Mars. Discounting the snark of both liberal and conservative planetary isolationists more sober precincts are exploring the merits of such a proposal.
The most obvious ointment bound fly is the cost. Establishing a viable moon base would more than likely involve monies the equivalent of, or probably even greater than, the 175 billion bucks (inflation adjusted) of the Apollo program. In an age of truly insane budget deficits such a program really does appear to be, well, insane. The numbers have been run a thousand times and with anything remotely resembling current technology the costs of such an effort are wildly beyond anything any forseeable congress will ever tolerate. It all comes down to dollars per pound to orbit. Using the most sophisticated heavy lifter technology available the numbers just don't add up, to put it as mildly as possible.
Even the sundry nascent private space exploration efforts, amounting to really only stunts at present, have little chance of driving down costs to levels that will ever make any remote economic sense. We appear to be stuck. Stuck on Earth's surface that is. My personal feeling is that we will remain stuck for probably at least a century. This of course is in the category of a wild-ass guess, could take somewhat less time, and could well take two or three times as long as a century.
Two central conundra confront us. The first is getting bulk materials to orbit at a cost that is a least three orders of magnitude less than that is possible or foreseen in the next several decades. Lifting the many thousands of tons to orbit required by moon base building or a Mars expedition by means of chemical reaction rockets is simply out of the question as a long term solution. To be sure there are current private efforts to greatly increase the efficiency of conventional rockets and these should bear real fruit in the fullness of time. What they will not do is cut payload to orbit costs by the several orders of magnitude that is actually required for true commercial exploitation.
This leaves what? Well it leaves exactly one thing and that is the much vaunted space elevator that will mechanically transfer material to orbit for, supposedly, a very tiny fraction of the costs that conventional rocketry can manage. The slang term for such a structure is the Beanstalk. The primary stumbling block for such a structure is usually taken to be the strength of the fibers used to build it which will need to be far greater than anything we have now or promise to have this century barring some truly monumental discovery--so monumental that its discovery will amount to a real life deus-ex-machina. In other words it will take a miracle.
For the purposes of discussion let us postulate that such hyper-strength materials can be fabricated, and somehow made affordable. This is merely the beginning. The engineering challenges will be stupefying difficult and fabulously expensive. The costs of building such a structure could easily exceed a trillion dollars. We are talking about deploying millions of tons of ultra high-tech materials and hardware on an unprecedented scale with unprecedented problems guaranteed to rear their heads before the project is finished. With such vast quantities of complex materials and huge heavy devices economies of scale will only take us so far.
Vast amounts of electrical energy will be required to power the vehicles which would ply this mega-tower, some of which can be recovered to be sure, but nevertheless the equivalent of several large nuclear powerplant's worth of generating capacity would be required at the base of the stalk. Unknown dynamic resonance effects will crop up as the immense stucture ascends (and descends at the same time) and will continue to crop up after the structure is finished. Problems of NIMBYism, terrorism, and equatorical political factors will plague the builders. Monies will aways be in short supply with the required coalitions of national finances subject as they always are to interruptions, turf wars and political battles. As in the case of advanced fighter aircraft the project's gestation will be long enough for technological obsolescence to be a major thorn in the side of project management.
Before the project is finished hundreds of billions of dollars worth of conventional heavy lift capability will be needed to facilitate construction on the orbital terminus of the stalk. After what is likely to be a quarter century of construction the amount of energy to deliver a pound to orbit will indeed be a small fraction of what it is now but the gigantic build costs will have to be amortized over each and every pound delivered to orbit for decades afterward. Further consideration must be given to the fact that during the lifetime of the structure there will many billions of dollars of cost per decade required to maintain and upgrade the structure. Consequently the fully amortized cost to orbit will be thousands of dollars per pound which although cheaper than now is still a stiff tab to pay. The beanstalk concept, although promising, is far from a financial panacea.
This brings us to conundrum two. Once we get that material to orbit then what? There we'll be all dressed up with nowhere to go because we will still be dependent on conventional rocketry to get where we want to go in the solar system. We will not, repeat not
be able to cost effectively explore the solar system with conventional rockets. The costs and time frames are simply far too prohibitive. With conventional rockets we would still need months to get to Mars and years to get to Jupiter and Saturn with severe contraints in terms of the supplies needed for such long journeys and the sundry human factors that will remain as intractable as they do now.
Nuclear powered rockets are touted as the best hope for cutting this knot. A vehicle under one continuous gee of thrust would only need a few weeks to get to Jupiter, including turnaround and deceleration into Jovian orbit. Trouble is we do not yet have a clue, despite much research, on how we will ever build such devices. All the projects to date envision devices that, although operating continuously, provide very small amounts of thrust. This would be an improvement over the massive fuel consuming burns of conventional rockets but the transit times will still be in the area of many months, at a minimum. Such low thrust scenarios could make a Mars expedition more viable than at present, somewhat, but transits to the outer planets are entirely another matter. The low continuous thrust scenario could well be a cheaper route but it will not be a particularly speedier one.
To properly address these stony problems will require truly stupendous leaps in the materials and power handling sciences--leaps that will dwarf what we have already achieved--and we have achieved a very great deal. To build a space elevator we will need materials that make the very strongest carbon nanotube based fibers we can manage currently seem like overdone spaghetti. To build nuclear powered rockets that will continuously develop tons of thrust over long periods will require both materials performance and power densities that make the most efficient rocket engines yet devised look like a child's holiday sparkler. It is going to be really really frakin' HARD
to achieve all this. It is very possible that we could be in Star Trek territory, beyond the 24th century, before we get a real handle on these bizarrely difficult challenges. It is in fact possible that we might develop a true FTL spacecraft drive before we ever figure out how to get a pound of stuff to Earth orbit at a reasonable cost.
The big problem is that mere incrementalism is not likely to bear the fruit we want. Slightly ever greater efficiencies in heavy lift capability and marginally ever more powerful and compact drive technologies are not going to get us there because costs are bound to remain a severely hobbling factor. We are beyond baby steps. What we need are true technological seven-league boots. At this point we have not the faintest idea what such boots will look like.
This is a hard pill to swallow for enthusiasts of space exploration, as I am, but there simply will not be any cheap easy road to the planets let alone the stars. And since our publicly funded space programs are essentially jobs programs that will at best tolerate a timid incremental approach we will be making little progress in the decades to come. I fear that Newt-like boosterism, even if it inexplicably infects the general public, will make little difference in the long run.
The Manhattan Project and the Apollo program required a reordering of industrial focus and the injection of vast amounts of cash to achieve what they did but both achieved their objectives with essentially what technology was available, or envisionable, at the time. All it took was will and money, a lot of each to be sure. It's naturally going to take vast heaps of both of those to achieve a true interplanetary spaceflight capability but it is also going to require technological leaps the likes of which we can simply can not imagine at this time. The state motto of Kansas is instructive--Ad Astra Per Aspera--to the stars with difficulty. Brother they ain't kiddin'.