On Sunday, February 16, 2003, at 08:15 PM, John Carmack wrote:
The assumption is that it isn't the man-hours themselves that are important, it is the time that the vehicle isn't flying. Sure, not needing labor at all is best, but being able to get the vehicle back in the air rapidly, even if it means larger labor in parallel with the flight, would be a significant improvement. Especially for something like a suborbital point-to-point service, where the total flight time is very short, moving what labor is necessary out of the critical path is good practice.It seems to me that the figure of merit is total man-hours per launch, regardless of where in the processing flow they appear. This is what scales the cost per launch (neglecting materials costs). Cutting labor for fixed flight rate or increasing flight rate for fixed amount of labor both improve man hours/flight. Obviously this neglects a bunch of important issues, but as a BOTE analysis principle it seems to me that it's the right approach.
I'm just laying this out on principle -- For a vehicle that is going to operate that rapidly, I would almost certainly opt for some kind of active cooling.Water cooling seems to me the way to go. You'll be fueling anyway, so the same guy who hooks up the Fuel and Ox lines can do the TPS water. The water will take a lot less time, it can be completed in the slack time while the fuel/Ox handler is waiting for the tanks to fill. You'd also want containerized payload so the payload swap would be a simple matter of pulling the old pallet and installing the new one. It seems to me the four man hours of on-pad effort is possible, but once you take into account the time to install the payload on the pallet and time in the hanger for periodic maintenance, a total of four man hours per flight seems out of reach, especially if you have a pilot (which I think is a good idea for various reasons).
......Andrew
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