SPACE: ISS (and Other) Thoughts

Date: Fri Oct 20 2000 - 17:11:11 MDT

With the successful completion of STS-92's on-orbit work at the International
Space Station, I'm prompted to some musings on that growing stack of
hardware. As long-time list denizens know, I'm an Apollo-era space-junkie,
and can't help but be both happy and a little bemused at the landmark of the
shuttle's 100th flight and ISS's being very near "Phase I" completion.

The Original Plan (i.e the von Braun-Ley vision that was hard-coded into my
psyche as a preschooler looking at LIFE magazine) called for step-by-step
development of space: First a winged, reusable orbiter, then a LEO station,
then the Moon, then Mars; all of which would be done by "about now", i.e. the
turn of the century. Well, the Cold War saw to the fact that things got
taken out of order, and the funding slump following Vietnam saw to it that it
took 20 years to get from the reusable winged orbiter to the first station,
in the US program, at least.

So what do we have with the ISS? Cold War aftermath dictated building the ISS
in a very high inclination orbit. This has lead me to wonder about a number
of questions:

<> How much of a delta-v penalty does the STS pay in reaching that high

<> How much of a delta-v penalty will a launcher starting from a more
sensible equatorial base have to pay to reach the current ISS orbit?

<> Suppose someone actually uses the ISS for one of the primary original
purposes envisioned in the Original Plan, i.e. as a construction and
maintenance base for further space infrastructure, such as a reusable
translunar vehicle, planetary transit vehicles and the like. How much
penalty is imposed by its current orbit?

<> Suppose things change in the future and it makes sense to move the ISS to
a more equatorial orbit. Will the propulsion system the final version will
have be able to make that move?

Beyond these questions of "location, location, location", I also wonder what
the more professional space cadets here think of the ISS's prospects for
serving as a useful platform for expanding space infrastructure might be.
For instance:

<> Would it be possible to actually use the ISS as a "construction base" for
projects such as assembling translunar or interplanetary vehicles? This
question is prompted by the extreme caution I know is used when the shuttle
gets close to the ISS even in its current configuration, in terms of not
pulsing the ACS jets toward the solar panels. I gather that once the Big Rig
of solar panels is in place that final docking will be accomplished by
capture with the station's big arm, to cut down on final correction firing of
the shuttle's ACS. With that delicacy in mind, is it practical to think
about having a lot of hardware being moved around anywhere near the
"completed" ISS? If not, would there still be savings in doing work based
from the ISS, but "commuting" a short distance to a work site in some kind of
small "taxi" vehicle?

<> Do back-of-the-envelope calculations support the idea of using ISS as a
base for building other space hardware? By this, I mean are the savings in
having a "construction shack" in place sufficient to justify using it for
this purpose?

<> What are the cost/benefit factors effecting creation of a fuel depot near
the station for use by other vehicles. This always seemed to be an inherent
element of the Original Plan (c. 1955 - i.e. the one I was weaned on). I can
envision low-cost, specialty tankers, perhaps Big Dumb Boosters, for the
purpose of ferrying fuel into LEO. I realize that using lunar resources at
the Moon makes the most sense for getting energy there, but does a fuel depot
in LEO at or near ISS or something like it make sense?

<> What about using ISS as a base for an on-orbit satellite retrieval and
repair service? I've envisioned an unmanned "tug" vehicle, based at the ISS,
able to make the transit from LEO to GEO, for the purpose of placing
satellites into GEO, or of retrieving hardware from anywhere within that
regime. Targets could be brought back to ISS for servicing there, or for
packing into relatively "dumb" reentry shells to be shipped groundside for
servicing. Are there decent economics in this?

Ultimately, I wonder how expandable the ISS architecture is. Clearly, the
PMA "node" design allows for a modular extension in a lot of directions. I
know Spacehab has a couple of designs they're pushing for some nice
accommodation modules, including the truly cool inflatable hab module.
Obviously, crewing is limited to the lifeboat capacity, which is 3 until
Rutan's bird flies, when it will be 7 per ACRV. Docking two ACRVs could
bring the crew up to 14. Could the current ISS platform be grown that much?

CAVEAT: All of this is near term stuff and I know that flinging monkeys into
space doesn't make a lot of sense in the long run.

       Greg Burch <>----<>
      Attorney ::: Vice President, Extropy Institute ::: Wilderness Guide -or-
                                           ICQ # 61112550
        "We never stop investigating. We are never satisfied that we know
        enough to get by. Every question we answer leads on to another
       question. This has become the greatest survival trick of our species."
                                          -- Desmond Morris

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