Re: SPACE: ISS (and Other) Thoughts

Date: Sat Oct 21 2000 - 06:25:08 MDT

In a message dated 10/21/00 12:30:17 AM Central Daylight Time, writes:

> Using OV-103, basic cargo lift for due east from KSC (which is located
> at 28.5 deg N) to 110
> nm orbit was said to be 55,000 lbs (pre-Challenger figures). Subtract
> about a ton from that for the post-Challenger firepole, etc.; this
> brings us to a nominal 53,000 lbs to 110 nm.
> For the same altitude, subtract 500 pounds per degree of plane change,
> according to an old page I found via Google:
> html
> ISS is as you know at 51.6 degrees, so based on that rule of thumb, we
> are talking about a roughly -11,500 lb penalty just to get to a minimal
> orbit at that inclination.

Aha - I should have thought of that. I knew about the "fact sheets" on each
of the orbiters". Looking these over and the payload weights recorded for
ISS flights, it looks like your SWAG of 5-6 tons is about right for the "Cold
War Orbit Penalty". Well, that's one way to quantify the "weight of history"
I'm always blathering on about.

In a message dated 10/21/00 6:20:17 AM Central Daylight Time, writes:

> > <> Would it be possible to actually use the ISS as a "construction
> for
> > projects such as assembling translunar or interplanetary vehicles?
> The trend goes to smaller system size. It is not obvious why even a
> deep space mission would profit from more bulk, unless we're talking
> manned missions. But manned missions are an obvious mistake at this
> point, anyway.

Gene, gene, I KNOW that, I just don't FEEL that :-) And politics and
historical inertia being what they are, a good deal of homo sapiens'
investment in extraterrestrial infrastructure over the next 10-15 years is
going to be in NASA/ /Energia/ESA/NASDA's manned programs, like it or not.
Furthermore, as Spike has pointed out here recently, a significant portion of
humanity's collective knowledge of space science and technology is
concentrated in the institutions that run these programs. One of the primary
values of the ISS program I see for the intermediate term is that it provides
a place for this group of people to continue to practice and perfect their
craft for the next decade or so.

Beyond that, I'll reply to your specific point above: One reason for bulk is
REDUNDANCY, a very high value in space tech. This IS a relative value,
however: The smaller the components in a spacecraft, the lower the gross
penalty one pays for redundancy.

> > <> 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?
> Excuse me, I don't see any logics behind this. All the mass must come
> from the bottom of some nearby gravitational well. There is nothing
> else there nearby which doesn't have a prohibitive delta vee.

There is one value in marshalling resources in one place: Logistics
efficiency, which is why I don't like the high inclination orbit ISS is in.
Matching a fuel packet to a user on a case-by case basis requires optimizing
lift investment to each specific mission. In any given case, a specific
booster may have more delta-v capacity than a specific refueling or other
supply task requires. Averaging over a large number of refuelings, it may be
more efficient to optimize fuel lift out of Earth's gravity well and pay a
smaller total penalty on each rendezvous in Earth orbit. Remember, LEO is
half-way to anywhere.

> If one
> thinks about braking down some near earth asteroids with a barrage of
> nukes sufficient for Earth orbit capture, lowering down asteroid belt
> material with solar sails or braking a comet fragment using newly
> proposed plasma magnetic solar wind sail these are obviously highly
> complex, very expensive missions. Being realistic, we cannot think of
> those yet.

That's right, which is where my questions come from. You may recall I asked
the questions some many months ago "(1) given Drextech, how fast could a
committed group of space enthusiasts develop a basic space infrastructure and
(2) how small a group of technologists would be required to cover all the
bases to create a basic extraterrestrial infrastructure?" Bearing in mind
Robin's observations about "dreams of autarchy", the reality of nano-enabled
space efforts will almost surely not be that of a small group starting ab
initio, but rather will consist of incremental work building on whatever
exists at the time and, at first at least, in a fashion that is embedded in
the existing institutional and programmatic dynamics of the time. This is
one of the primary reasons I continue to be keenly interested in the most
likely state of space infrastructure development over the next 10-40 years.
> If you want to refuel using Earth resources, you need to haul up fuel
> using some cheap transportation, hypersonic reusable vehicle (to be
> developed, a risky investment) or old-fashioned rockets (proven,
> scalable technology, would be much cheaper if built in numbers). It
> would be much better to use lunar linear mass drivers for launching
> processed materials and probes, so constructing these should be on top
> of our priorities.

I'm with you 100% on this, gene, which is why I have to grit my teeth at the
activities of the Mars crowd. Luna is FAR more important for the near-term
development of space.
> We can get to the Moon in one piece from Earth surface. Why using
> several missions to bring up fuel and system modules before going to
> the Moon? It would rather make more sense to build a bigger rocket,
> something which can carry twice Proton's payload.

Yes, true . . . but how likely are we to get a good Saturn-class booster in
the near future? The near-to-intermediate-term economics of space development
support continued refinement of small and intermediate sized boosters. This
factor alone is one reason that an on-orbit construction facility may be
important. And the process of building ISS shows that - again in the
near-to-intermediate term - having a monkey on site to hook things up IS
still a good value. Until we have highly reliable, lightweight robots with
equal dexterity and flexibility, folks who live in my town are going to be
needed to build things in space. (Did I just show a bias???)

       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

This archive was generated by hypermail 2b30 : Mon May 28 2001 - 09:50:18 MDT