The case for smaller launch vehicles in human space exploration (part 2)<< page 1: getting back to the bottom line More launchers, more possibilities…By the year 2018—the year NASA has chosen for its first lunar return mission—it will have been almost 50 years since mankind first set foot on the Moon, and the world will, at best, have only one heavy-lift launch vehicle. Conversely, as of this writing there already exist five medium-lift boosters that can deliver 20 tonnes or better to low-Earth orbit, and with more on the way. Why are we so reluctant to utilize what we already have? Smaller launch systems exist in greater quantity because of greater demand. Whether or not humankind begins in earnest a program of exploration beyond LEO, a large market will still exist for smaller boosters, but the same can’t be said for HLLVs. To be sure, most heavy-lift advocates acknowledge this fact: Robert Zubrin of Mars Direct fame recognized this past summer that a heavy-lift booster’s only real purpose can be human spaceflight beyond low orbit.
There is another important issue that needs to be addressed. If the current NASA administration has its way, a program of manned lunar expeditions will evolve in the next few decades that only NASA itself will be capable of undertaking. Since NASA’s hardware will be optimized for launch on heavy-lift vehicles (along with their characteristic low launch rate, high operations costs, and veritable standing army of ground staff), there will be limited potential at best for either the private sector or other countries to get involved in a meaningful way. No nation in the world is capable of delivering 100 tonnes to Earth orbit in a single shot, and no private effort will be capable of developing heavy-lift launch technology anytime in the foreseeable future, so with a program of lunar exploration designed for HLLVs, there won’t be anyone involved in launch anywhere but on the Cape. The civilian launch industry won’t grow, and NASA will be shouldering all of the launch costs instead of divvying them up between different companies or countries. It makes one wonder just what kind of a space age the 21st century will become. Smaller launch vehicles are cheaper to build, cheaper to fly, and cheaper to maintain, and for a given amount of payload that must be launched into orbit, smaller launchers are more economical by virtue of their higher required flight rate. If an exclusively US-based effort is what the American government wants for lunar or Mars exploration, then specifying medium-lift boosters and doing any of:
would all represent much more cost-effective ways of flying than spending upwards of $10 billion on a single HLLV and edging everyone else out of the game.
NASA Administrator Mike Griffin has acknowledged these criticisms, but has maintained that, “…it is not acceptable for a publicly funded program not to have a way of meeting its mission requirements in the event that commercial operators do or don’t materialize”. Certainly this is a valid point, but ensuring NASA can still get the job done without help from industry does not necessarily mean developing a heavy-lift booster. NASA’s proposed Crew Launch Vehicle—if designed with the reliability its supporters claim can be achieved—will represent the ideal launch system for undertaking missions to both the Moon and Mars using orbital assembly, should privately developed boosters not come to fruition. And small-launch, orbital assembly-based missions would allow the agency to save a great deal of money by circumventing the $10-billion investment required for a shuttle-derived HLLV, which would do nothing less than make private launchers useless for public-sponsored space exploration. And what about the possibility of international cooperation? If a multinational mission architecture was desired, then both Russia and Europe (really France, but be careful to whom you say that) already have launch vehicles capable of delivering 20–25 tonnes to low-Earth orbit, in addition to America’s existing two (soon to be three). Because a mission design using medium-lift boosters requires far less capital investment that can be far better amortized over the course of the mission, an international cooperative may even encourage nations without significant launch industries to create their own systems that can do the job, or at least to fund individual component launches. (The Canadian Space Agency’s budget is only about $300 million Canadian per year, but the promise of a maple leaf emblazoned on a propulsion stage could go a long way towards encouraging a contribution.) Involving other countries would keep the competitive elements in space exploration constructively economic, rather than detrimentally political. Having different companies or countries bid for launch contracts would certainly be preferable to edging both out completely and leaving NASA to shoulder the entire launch burden with an expensive vehicle that no one else can match. It’s like giving NASA the only keys to the car, and then letting them drive off without insurance. ConclusionsIf the reader of this article looks into the technical paper from which its mission design was derived, they will find a much more modest argument, which was strongly tempered by criticisms from several notable people of high standing in both industry and academia. The times currently favor heavy-lift launch technology, and the engines of popular opinion are powerful ones with which to contend. However, advocates of smaller launch systems persist, and the issue is by no means decided. Heavy-lift launch vehicles will be highly effective in future space exploration, but until humanity truly begins to venture beyond low Earth orbit in a significant way, bigger boosters will struggle to find a cost-effective place. The private sector can’t build them, nor is there presently a launch market big enough to justify them. For a healthy, cost-sustainable space program to develop, the private sector must play a significant role, and the launch industry must be encouraged to grow. Mike Griffin has, in spite of supporting the agency’s present course, nevertheless acknowledged that the task of human space exploration is too daunting for NASA to undertake alone, and that if reliable commercial launch providers can emerge in the next five to seven years, they would allow NASA to concentrate its resources on more advanced activities. Those providers are already here: all that’s required now is a change in design philosophy away from the Apollo-style “big booster”, a delay or failure of which may deny humans the dream of meaningful space exploration. If the true purpose of President Bush’s Vision for Space Exploration is to open the inner solar system to mankind, then undertaking actual missions beyond Earth orbit should be the highest priority. Heavy-lift launch technology doesn’t currently exist, and its re-development will require several years—years in which no space exploration will occur at all. With our future in space hinging on the reliability of a single vehicle, the ability of NASA to persevere through setback or tragedy is also called into question. Launch system redundancy, flexibility, and cost-effectiveness are the real keys to space exploration, especially if we want the exploration to last. For this reason, the use of a larger number of more modest, more attainable launch vehicles should be re-examined in earnest by policymakers and engineers alike. Humans have a promising future in space, but what’s the best way to get there? AcknowledgementsMany thanks to Edward Wright, president of X-Rocket LLC (whom I have never met) for developing in previous work several of the economic arguments which I have employed. I also wish to thank several HLLV advocates, in particular Dr. Robert Zubrin, whose well thought-out (and often strong) criticisms of medium-lift launchers in human spaceflight have frequently caused me to re-evaluate my beliefs on this issue. The future of human spaceflight is only helped by awareness and debate—and fortunately, it seems that both are currently growing. References
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