On Sunday, February 16, 2003, at 10:57 PM, Henry Spencer wrote:
I think there is a good case for having the ground crew actually go up to the vehicle and service it. The more eyeballs looking over things the better the chances of catching anomalies before they get out of hand. There's a cost, of course, but at least in the case of propellant transfer, I would like human eyeballs looking at the connection as it is made and broken. These are the times when spills are likely. Also the propellant transfer connections on the ship are likely to be stress risers in the skin, and to be exposed to somewhat harsh conditions on reentry. You could have the eyeballs in question be in a remote location watching a screen, but absent a reason to keep the humans away from the ship, I'd rather have them right up near it.On Sun, 16 Feb 2003, Andrew Case wrote:Water cooling seems to me the way to go. You'll be fueling anyway, soAs I think I noted before, at that kind of operations pace, *nobody* hooks
the same guy who hooks up the Fuel and Ox lines can do the TPS water...
up fuel and oxidizer lines -- they are part of the launch stand, like all
the other umbilicals, and are hooked up (and leak-tested) automatically
when the vehicle is positioned on the stand. The Russians have been doing
this for thirty years; surely us backward Westerners :-) can learn to do
it before too much longer.
My thinking has changed a bit regarding the launch stand - I'm now thinking of a pad with service vehicles, and access to fuel/ox/water through hatches in the pad, much like an airport apron. No big service tower, certainly no movement of the ship between landing and relaunch. If the landing gear can't take liftoff weight (which it probably can't), then the first thing that happens after the landing engines are turned off is a service vehicle moving a support pedestal into position to take the ship's weight before it is fueled. I assume that the prop transfer vehicle, the launch pedestal vehicle and the pallet swap vehicle(s) all have automated systems to ensure accurate location and to test fits and seals, but also that they are under the control of a person who does the rough positioning and who can override the automated systems at any time. The driver/controller should be on the service vehicle, and should have a clear view of the actuators/connectors/whatever.
That said, there's no reason the propellant transfer and TPS water can't all go through the same umbilical plate, hooked up by the same person.
You are right - a guy plugging hoses in one at a time doesn't make sense. OTOH, I don't think it's a good idea to trust a machine to do it completely unsupervised. A small error could turn into a very large accident (loss of vehicle, possibly loss of pad, possibly loss of personnel). The cost of those eyeballs seems to me well worth it. It might make sense to have a fully automated set of pad services, with just a couple of guys who do nothing but walk around from one spot to another at the appropriate time and watch as critical automated functions are performed. These crew members could stop everything while they took a closer look if something seemed fishy. You'd also want somebody who could take a big picture view of things happening on the pad. That's three people to turn the ship around. Of course that comes at an increased cost in infrastructure, but it might be worth it.The "handler" will be a computer, or at least an automatic sequencer --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.
like the one that tanked operational V-2s -- and it will have no problem
doing multiple fills simultaneously. Everything that can possibly be
done via the umbilical plate and automatically-controlled valves will be.
Those are the customer's man-hours, not yours. You accept only palletized...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...
payloads. There is none of this business of custom treatment for each
payload, or at least it's an extra-cost option rather than normal practice.
Good point. UPS doesn't package my mail.
Up to a point. Total cost per flight has to take absolutely *all* costs into account. My sense of the problem is that beyond a certain point man-hours on the pad can only be shaved further at the expense of substantial increases in man-hours elsewhere in the system, all of which have to be paid for....and time in the hanger for periodic maintenance...I think it's reasonable to count that under a different heading.
......Andrew
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