At 12:29 PM 2/18/2003 -0500, Andrew Case wrote:
On Tuesday, February 18, 2003, at 12:05 PM, [EMAIL PROTECTED] wrote:There's no reason you can't build a huge transporter that can gently pick up the ship and trundle it up to a mile or so over well prepared surfaces to a dedicated launch stand. Obviously you're better off landing closer to the stand than you are landing far away, since the transporter is unlikely to move faster than walking speed. You're going to need such a vehicle anyway, for those occasions when you need to get the ship into a hangar for things like swapping out engines or periodic maintenance.Since by definition, the engine thrust support structure (TSS) must take something like 1.5 times the load of the fully fueled vehicle, the ground support structure could be something as simple as a robust single leg (or jack) that fits into a socket at the center of the TSS. The outboard gear would provide stability, while the central leg bears the weight until liftoff.
I agree on the need, but I don't see why it has to be slow and ponderous. Personally, I think the ideal vehicle would be a specially adapted travel lift, like they use to transport and launch boats from large dinghies up to 100'+ megayachts. Travel lifts tend to have fairly large tires and good suspension -- I don't see why they couldn't keep up the equivalent of a running pace or better (10-15 mph) over the equivalent of an airport tarmac.
There's an argument to be made against moving it based on the fact that that's slack time for all of the ground crew except the guy driving the transporter, but it's not clear that you can't make that time up by improved efficiency once you get to the launch stand (since now everything is in a known and well defined position relative to everything else).
The problem with this is that the driver is eating up man-hours picking up the vehicle, driving it around, and place it. I can see a crew easily eating up Michael's four man-hours just on these operations. I agree with Gerald on the desirability of a mobile launch stand and mobile service vehicle. The placement and operations of both of these vehicles can be heavily mechanized and automated. Even garbage trucks are automated these days :). The service vehicle can connect to in-pad plumbing for propellant and other fluids.
However, I also agree with Randall on the economic desirability of extremely fast turnaround. I don't think it's really that much of an economic issue until your flight rate reaches multiple flights per vehicle per day, with production runs of tens of vehicles per model. At that kind of production and flight rate, even very large development budgets can be readily amortized. I think a first generation cheap reusable should shoot for a much more modest turnaround goal -- a few hundred man-hours per flight, including routine maintenance and inspection, but not major maintenance. Allowing for a longer turnaround will reduce the vehicle's overall complexity and reduce the number of tradeoffs that must be made.
-p
Mars or Bust!
www.marssociety.com
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