Re: Space Access Update #112 9/19/05

"Fred J. McCall" <fmccall@xxxxxxxxxxxxx> wrote in message
news:a0knl1tjgpk7600jbutgj85kum5u7pet84@xxxxxxxxxx
> "Pete Lynn" <pete@xxxxxxxxxxxxxxxxxx> wrote:
>
> :"Fred J. McCall" <fmccall@xxxxxxxxxxxxx> wrote in message
> :news:a5vil1p203v26arp7v4e1ncvu62232k5c3@xxxxxxxxxx
> :> "Pete Lynn" <pete@xxxxxxxxxxxxxxxxxx> wrote:
> :> >
> :> > I would add to this that the design should be
> :> > capable of fast prototyping and incremental
> :> > development. Ideally this should be how one
> :> > accommodates vehicle loss or damage, not by
> :> > building three identical prototypes.
> :>
> :> That's not how we do aircraft.
> :
> :It is how we *did* aircraft.
>
> It WAS how we did RESEARCH platforms that
> were never intended to lead to anything directly, but
> that's what you want to get away from, isn't it?

No, not until the development is ready for the commercial step. The
research does have to be commercially focussed, as opposed to whatever
the focus has been to date.

> No, that's not a better question, at least insofar as the
> suggested paradigm of development goes. You're no
> longer talking about 'prototypes'. You're talking
> about producing ONE vehicle and then trying to
> make money with a single copy of it.

Operational prototyping is a great aid in introducing a commercial focus
into the development process. This is critical. I doubt the first five
prototypes will pay for themselves, however they will hopefully
incrementally make less of a loss.

> Operational vehicles do not lend themselves well to a
> test program. You sort of have to choose either 'test'
> or 'operate'. Describe your vehicle as a 'test
> prototype' and see how many people rush to put
> their expensive payloads on it.

The current market leads to current launchers, for CATS one has to
ignore that market. Inexpensive and far more numerous payloads will need
to be developed concurrently.

After initial testing, operational testing will I expect mostly focus on
longevity and operational issues. There is a great need to build up
flight hours for vehicles and people a like.

> :At $50/kg to LEO, $500,000 puts ten ton in LEO.
> :At this, a million dollar house in LEO seem feasible.
> :The up keep might be a bit more expensive, but then
> :so is the access. This still seems within the price
> :range of a very large number of people.
>
> Ten tons isn't a 'house'. Ten tons is a not very big
> trailer. A not very big trailer in LEO that only cost
> $500,000 to put together is a very unsafe not very big
> trailer. Go look up the weight of ANYTHING that
> humans can live in in space for any length of time.
> Hell, go look up the weight of your car and
> extrapolate.

I suggest you look at this from a design perspective and do some
numbers.

> Now, just how big do you think the market is for
> million dollar deathtraps in LEO?

Considering how many million dollar houses there are on Earth in various
resort locations, I would expect in the millions.

> :As per cruise ships...
>
> If you think there's a similarity, you're VASTLY
> mistaken. You might want to look up just what
> percentage of people get 'space sick' in the short
> term.

And you presume these problems are insurmountable.

By the time we have million dollar LEO homes for the masses, I would
expect something more along the lines of five kilometre diameter
spinning spoked housing estates with collective areas and functions.
This should be sufficient to prevent such sickness, until then, people
will have to cope.

> :Because the passenger would be a pilot.
>
> Then give the passenger real controls. If 'a pilot' can
> fly it via laptop locally, then the same pilot can fly it
> via laptop remotely.

They would be full controls, I just doubt they would have the added mass
of full mechanical back ups.

> :It is quite sufficient. The Wright flier and those which
> :followed were not four person aircraft.
>
> None of those planes were 'transports'. If you want
> Mercury capsules, you know where to find them.

Mercury capsules have almost no relationship to CATS.

> :There will be a lot of developmental water under the
> :bridge before kids are on the cargo manifesto. Kid
> :proofing a space station is non trivial and will come
> :much later. Initial passengers will be competent and
> :trained individuals.
>
> In other words, we're out of the 'tourist' venue again
> and back to a government program.

I would still consider the large numbers of adults who pay to go to
Everest or Antarctica to be tourists. This is how I would expect CATS to
start out.

> :This can more sensibly go up on separate unmanned
> : flights.
>
> So what's the point of your 'single man in a can'
> design again?

Because it can accomplish most everything a larger design can at lower
development cost and higher flight rates.

> :> What's the leak rate of Vectran with atmospheric
> :> pressure gas on one side and vacuum on the other?
> :
> :Fairly good I think,
>
> 'Fairly good' isn't exactly a quantitative measurement.
> 'I think' doesn't inspire much confidence that even a
> non-quantitative measurement is very trustworthy.

Obviously you are unfamiliar with such design, the Vectran coatings are
as impermeable as one makes them. As I mentioned bladders are also
generally used, I suspect this is more for redundancy.

Bigelow thinks Vectran is workable, if you want a place to start
learning about such things, google transhab.

> I also note that you're talking about bringing up your
> inflatable in one load and all the fittings in other loads.
> That means you're trying (for example) to plug a
> door-sized hole in your inflatable with an airlock and
> get something approximating an airtight seal at the join
> while working in vacuum in a pretty clumsy suit. Now
> add the windows.

Obviously you have not thought about this in depth, this has been
discussed previously on this group in some detail.

Such habitats would be constructed from many shells. Something like an
interior protective wall, bladder, two to three redundant Vectran
shells, many well spaced impact resistant 'tent fly' layers, various
insulation layers, etcetera. The size of each shell being limited by the
payload mass, which as previously stated is not an immediate limitation,
(internal equipment may or may not be more limited by payload size).

It is relatively easy to add circular windows and airlocks to the
Vectran shells, and to do so in LEO - inserted as plugs. Windows are
heavy and pose an impact risk, to be avoided where possible. They would
normally be located on the Earth side where they would be more
protected. Separate heavy purpose built viewing habitats are perhaps
more likely. Perhaps heavy wall protruding port holes.

EVAs will probably not be required for habitat erection. Personally I
see little need for space suits for general construction work. One of
the first CATS station requirements will be a large hanger where large
objects can be assembled and checked over directly. Large robotic arms
holding manned capsules with smaller robotic arms should also arrise
early on in the development process, and many other possible
construction systems.

> Good luck with THAT.
>
> :but most inflatable designs use a separate bladder.
>
> You've still got vacuum on one side and pressure on
> the other. What's your loss rate? How much of your
> cargo capacity is taken up to replace gas that leaks
> through the walls?

What is your loss rate for any pressure vessel? This is getting
tiresome, do a little research.

> You're also going to need a separate cover, by the
> way. Vectran breaks down rapidly when exposed to
> UV. So we have the mass of the Vectran (how thick
> are you assuming that is?) plus the mass of an interior
> bladder of some sort to try to retain pressure for the
> occupants plus the mass of a UV-resistant external
> cover for the Vectran plus the mass of "airlocks,
> windows, extra shells, furnishings, etcetera".

Yes and?

> Oh, have you worked out just how big 500 cubic
> meters is? I make it a sphere of slightly less than 5
> meters radius. Now stick in 'furnishings, etcetera' and
> you've got how much living space, again?

About as much as a typical house.

> Your surface area is a bit over 300 square meters.
> That gives you about .33 kg of Vectran to cover a
> meter of surface. Giving Vectran a density of 1
> g/cc^3 (not far wrong), that gives you (assuming I'm
> not messing up the math working it in my head) about
> 30mm thickness of Vectran.
>
> I think you need to rethink some numbers.

For your example, try 0.33mm instead of 30mm of Vectran.

Pete.


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