"Pat Flannery" wrote in message
dakotatelephone...


Jeff Findley wrote:

So what? A pound of water is a hell of a lot cheaper than a pound of
extruded aluminum, a pound of machined titanium, or a pound of TPS
material. You're falling into the aerospace engineering trap that lighter
is always cheaper.

Why don't you check up on the total amount of water used by weight per
crew member per day on the ISS?
For a crew of four it's 40,000 pounds per year:
http://library.thinkquest.org/J01121...ce_station.htm
starting with that, extrapolating it to a full six-person crew, and it's
60,000 pounds of water per year.
Divide that by four for the intended three month lifespan of your
lifeboat, and you have to drag along 15,000 pounds of water alone to give
the crew something to drink, cook, and wash with while they are orbiting
up there awaiting rescue.

It's time for a reality check. That would be about 28 pound of water per
day! That's absolutely absurd! Take a look at Skylab's actual water
consumption:

http://www-pao.ksc.nasa.gov/history/...ylab-stats.htm

The *three* skylab crews used 4,290 lbs of water and that *included*
showers! The total duration of the three missions was about 170 days times
three crew is about 500 man-days. So, they were using about 8.6 lbs of
water per day, which included an occasional shower! You're not going to be
showering in a safe haven or lifeboat, so that number is obviously HIGH.

Actually, if you doubled the crew size of Skylab to six, that would have
been about 85 days of consumables, which is right in the ballpark for what
I'm proposing for an ISS safe haven.

Water 4,290 lbs
Oxygen 3,336 lbs
Nitrogen 933 lbs
Total 8,559 lbs

This included consumables for all the EVA's as well (there were quite a few
to repair Skylab and to service the Apollo Telescope Mount, which used film
canisters which had to be replaced via EVA). You'd have to add food and
LiOH canisters to that.

Then stick all the food aboard, the oxygen supplies, the CO2 scrubbers,
and the solar arrays, and your lifeboat is around the weight of two or
three Salyut space stations.

This is another silly argument. You don't need all the Salyut systems for a
lifeboat/safe haven. Consumables aren't as big a deal as you're making them
out to be. Again, consumables are cheap since there is zero development to
be done on them. A free flying safe haven which would last for three months
is more like the size of an ATV or two.

This "lifeboat" is medium-sized space station unto itself as far as mass
goes.

So what? You're still confusing mass with cost. Consumables are dirt
cheap. Additional copies of life support equipment already in use on ISS is
also relatively cheap compared to developing Orion.

It's like your plan for the orbiting refueling stations; you get so
enraptured by a concept that the actual costs of doing it are ignored, and
what you end up with is doing something fairly simple in a much more
complex and expensive way...due to some sort of preconceived philosophical
conceit in regards to how it _should_ be done in your own mind, rather
than the cheapest way of doing it in reality.

Every system we need for a safe haven was around since Gemini, Apollo,
Salyut, Skylab, Mir, shuttle, and ISS. No one knows exactly how much
orbital refueling stations will cost because they have not been developed
yet.

Jeff
--
A clever person solves a problem.
A wise person avoids it. -- Einstein