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Commercial Single Stage to Orbit Launchers

SSTO to the Moon

Commercial SSTO Rockets in Orbit A single-stage-to-orbit rocket, refueled with terrestrial hydrogen and lunar oxygen, could be flown from low Earth orbit all the way to the moon's surface and back again for an aerodynamic entry and landing on Earth. The effect of this on both our overall program costs and the appeal of the system for commercial space travel is tremendous.

Back to the real world of 1996 for a moment: Let me emphasize again that the reference mission is only one way of doing things. Given that there's one way of doing it that will work, regardless of how inefficient that way may be, then we know we have a program. So if the Space Shuttle or Titan IV works, a lower-cost launcher will make it work all the better.

There Ain't No Such Thing as a Cheap Launch

There are problems, though, even with an SSTO. Some aerospace executives are fond of pointing out, "There's no such thing as a cheap launch." Their thesis is that no matter how efficient the technology, the cost of servicing and integrating a payload into a manned rocket will still be extremely high. To some extent, that's right. There will always be the need to make sure the materials are selected meticulously, that maintenance records are kept in excruciating detail, that no material in the pressurized volume outgasses something inimical to the human crew. Those things take time, and time equals cost. When you add it all up, 100% of the cost of everything is human effort.

Any launcher program conducted by the federal government will be accompanied by almost boundless costs. It's the nature of government programs, and after 25 years of tilting with that windmill, I'm convinced there's just no way to avoid it. To get a government program to be cost-effective, we're bucking a grand tradition which dates back 5000 years, to the days Hammurabi and the city of Ur.

If we want low-cost access to orbit, we're going to have to see that it's done by private enterprise in a competitive environment. And if we want a rocket that we can refuel in LEO and fly all the way to the moon, we may have to do it ourselves.

Watch Out for G Loads

Incidentally, there's a key technical point hidden in the scenario outlined above. If wee fly an entry trajectory all the way from the moon, with aerobraking to Earth's surface at the end of the mission, the spacecraft will be going 36,000 feet per second when it hits the atmosphere. It will take at least 9 g's of acceleration to brake the rocket's velocity to a safe landing on Earth. Our first crews might be willing to take that kind of acceleration (the Apollo astronauts did, after all), but for the long-haul that's unacceptable. Our goal is to open space to everybody, not just to young men in perfect physical condition who are experienced in handling high g loads.

We can solve the acceleration problem by refueling the rocket on the moon so it has sufficient fuel to brake to less than Earth orbital velocity when it gets home. Again, the key is lunar oxygen. Oxygen is such a huge portion of the weight of the rocket when it lifts off the moon's surface, lunar refueling is the only thing that makes sense for chemical propulsion between the moon and Earth.

The weight of the hydrogen fuel is almost trivial by comparison, although tanks for liquid hydrogen can start to add up. In the early stages, we should plan to carry the hydrogen all the way from Earth. In the long term, we can get ahead by mining water-ice asteroids for hydrogen (oxygen, too), but first we have to get our lunar base going.

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