Chair Force Engineer

Saturday, August 18, 2007

From Expendables to Spaceships

Sometimes I wonder if I will ever see mankind build a true, reusable spaceship that replaces at least some of the expendable rockets that we rely so heavily upon. The problem is that there just aren't enough satellites in need of launch to justify the high development costs of a Reusable Launch Vehicle.

Therein lies the chicken-and-egg dilemma of RLV's. Nobody will commit the money to developing one, because the number of payloads means you'll never recoup your original investment. But if an RLV already existed, the number of payloads would possibly (but not certainly) increase as a result of having cheap space access.

Some RLV proponents might argue that the government should subsidize RLV development, or perhaps launch a satellite program that would require an RLV to complete it. I've often joked that NASA should build a gigantic orbiting sign that reads "No Fat Chicks." Such a sign would be miles across and could be read from earth. It would go into sun-sync orbit, so all the world's people could enjoy it at a predictable time of day.

Space tourism does give us hope that the aforementioned "egg" will be cracked. By opening the space frontier to thrill-seekers, you can dramatically increase the number of "payloads" that can be flown. The question is whether this potential market is big enough to justify further RLV development. Many people are risking their fortunes on the belief that it is. I suspect that suborbital tourism will be a thriving market within the next decade, but I also see orbital tourism being constrained by excessive launch costs. The path to the stars will probably begin with a sizable number of people paying a reasonable amount of money to take suborbital spaceflights. Using the profits from suborbital tourism, the suborbital vehicles can be further developed into orbital spacecraft. Once we have moved away from the "capsule on an expendable" paradigm, the orbital tourism market will open up.

Thanks to the space shuttle program, we have learned quite a bit about what will be required for a successful RLV. The shuttle was designed on the idea that it would have to replace virtually every US launch vehicle. It was designed as a large RLV with a large payload bay in order to accommodate a wide variety of payloads. Unfortunately, shuttle would never meet the high launch rates that were required to replace the other US launch vehicles. Designed for approximately 26 missions a year (it will fly every two weeks, or so we were told,) we learned that nine flights per year was pushing things to the point where operations became dangerous.

I have often thought about how big an RLV should be in order to be commercially viable. Should it be sized to compete with Soyuz, or maybe Proton? I suspect that even if the RLV replaced the world's most popular launch vehicles, it would still be a losing proposition at today's flight rates.

One idea I've been kicking around has been a single-stage, orbital RLV for launching nanosats. While single-stage rockets are horribly inefficient, they are much simpler from an operational point of view. Because this hypothetical RLV would only be carrying nanosats, it would be well within the range of what's technically possible. Because there are so many engineering schools in the world, the potential customers for this single-stage nanosat launcher would be numerous. This RLV would definitely open up the space frontier to universities who previously had no ability to afford space launch services.