Rocket to the Moon, Part II

If we are going to attempt to establish a base on the moon, we are going to need a reliable transportation system. One rocket now and again is not going to cut it. We need a regularly scheduled transportation workhorse. Our current space shuttle is very nice. It has a large carrying capacity. But this is also its' weakness. It is so big and so complex it takes an army of people of month of Sunday's to prepare for a single launch. We need something simpler that a small contingent of people can prepare and launch on a weekly, or perhaps even daily, basis.

Space elevators have been getting some attention for a while now, but I do not think anyone is going to build one anytime soon, perhaps not even in this century. The difficulties are enormous. We need:

• a material that would be strong enough,
• to put this material into geosynchronous orbit,
• extrude a 23,000 long mile cable of this material,
• build an elevator car that can climb this cable.

And then there is another difficulty that does not get mentioned much. Just how fast can this elevator car go? At 200 MPH (the current practical limit for wheeled vehicles), it will take 115 hours, or nearly five days to get to orbit. We could go faster using magnets (ala the Japanese Magetic Levitating Bullet Trains) but this technology has a way to go on the ground before we can even start thinking about using it in space. Perhaps by the time we have the means to build the cable for a space elevator, we will have the technology to climb it.

Meanwhile, back at the ranch, it would nice to have regularly scheduled rocket service to the moon. I have been thinking that what we need are nice simple solid fuel boosters that lift a couple of tons into orbit. Small rockets are simpler, and if there is a disaster, you do not lose as much. If we have learned nothing else in our 50 years of fooling around with space, rockets are dangerous. Right now the space shuttle uses two solid fuel boosters that are made in Utah, in sections, and then shipped via rail and barge all the way to Florida for assembly and launch. They are made in sections because the rail line goes through a curved tunnel which limits the length of the booster sections. (I did not find any reference to the curved tunnel, but I distinctly remember reading about it a few years ago, probably when we had the first shuttle disaster.)

This business of building the rockets in West and then shipping them half way across the country strikes me as nuts. I am sure there are very good reasons for it, even if they are just political, but I still think it is nuts. I think a better way would be to make the rockets at or near the launch site. I have a vision of having a series of missile silos in the ground, and having a couple of guys in a tanker truck, or maybe something like a cement mixer, driving from one silo to the next, dispensing the liquid version of the solid propellant into rocket booster shells installed in the silos. Leave the liquid version to harden into solid propellant for however long it takes, and then repeat until you have a complete solid booster. Cap on the payload and press the go button. What could be simpler?

Well, actually, almost anything. Putting missile silos in Florida is going to be to like trying to bury bodies in New Orleans. The water table is so high the silos will likely float right out of the ground. Launching a rocket out of a silo is going to create a very hostile environment around the outside of the booster. On the other hand, the defense department managed that for nuclear missiles, but then they have different budget constraints and different requirements. (So what if one out of ten nuclear missiles does not make it off the ground, this nuclear war, d**n it, full speed ahead!) And then there is the problem of making a core burning solid fuel rocket.

There are basically two kinds of solid fuel rockets:
1) end burning
2) core burning
End burning rockets have a solid block of fuel. The end of the block nearest the nozzle is ignited and the block burns steadily towards the front of the rocket. Core burning rockets have a hole through the central axis of the fuel block and the rocket. Ignition is done simultaneously all along this central hole. The fuel burns outward towards the outer shell of the rocket. Core burning rockets burn out much faster and generate much more force than end burning rockets. Shuttle boosters are core burning.

So we are pouring solid fuel slurry into an empty rocket shell casing, but we want to leave a hole in the center. Well, we could put a pole in the center and then pull it out when we are done filling the rocket, but how are you going to do that? The rocket is already in the silo. You would need a large hole under the rocket to pull the pole into when you pulled it out of the rocket.

So there are some problems with the idea, but I really like the idea of two guys in a truck dispensing rocket fuel slurry into a series of rocket silos. 3, 2, 1, blastoff!