Re: DIY space transport

"Derek Lyons" <fairwater@xxxxxxxxx> wrote in message
news:42d7ead5.15620636@xxxxxxxxxxxxxxxxxxxxxxx
> "Len" <len@xxxxxxxxxxxxxx> wrote:
> >I know that some think that I am rather fickle with respect to the
> >variety of launch vehicle concepts that I have proposed. However,
> >with our very limited resources, I have found that this is, by far,
> >the best way to make the most progress for the fewest bucks.
>
> Proposals don't make progress - bending and flying metal does.

It is rare that I can comprehensively disagree with something you say -
this is one of those rare occasions.

There is yet to be general conceptual vehicle design convergence, until
this happens bending metal beyond the component level will not be
justified. We are not yet ready to bend metal and doing so prematurely
is a very big waste of money, as has been elaborately demonstrated.

There is not even a general consensus on things like optimal flight
rate, vehicle size, orbital assembly, propellant choice, etcetera. We
do not yet even have well developed cheap OTS componentry like plug and
play rocket engines and guidance systems. Hell, many people think heavy
lift, space elevators, SDVs, etcetera, are a good idea. We are just not
yet ready to bend metal let alone fly it, except with regard to
fundamental research and development.

Currently we are following what I refer to as the astrologer's model of
development. We use the stars to randomly select a vehicle design that
has no conceptual basis in cost, development, practicality, etcetera.
By literally trying hundreds of designs survival of the fittest will
eventually select for design superstitions that inadvertently work
finally resulting in a viable design. This is a pure numbers game.
Because the government is involved everything has to be done at great
scale, and because of the nature of such institutional knowledge these
designs invariably continually repeat themselves. This is why astrology
must be used, to randomise the process and avoid old patterns.

Say we try one new white elephant every thirty years, and say we have to
try one hundred new vehicle designs before we hit on one that works,
then we should have a viable design in say another 3000 years.
Obviously this assumes the NASA budget can be sustained and publicly
justified for that length of time.

Most of the economic design optimisation can still be done at the
conceptual level without going through the expensive process of bending
metal. When the conceptual designs have been sufficiently developed the
timing will become apparent as to when to start bending metal.
Basically the rate of conceptual design improvement will decrease to the
point where the cost benefit analysis of conceptual design is less than
that of bending metal. Arguments about the excessive costs of some
conceptual designers compared to the costs of other metal benders aside,
we are not yet at that point. A $1000 worth of thinking can still
refine a general design far more than a $1000 worth of bending metal.

In development there must always be the test of reality, even with the
most sensible conceptual design analysis this will still be in part a
numbers game. As such initial designs should be biased towards even
lower development cost than would otherwise seem optimal - vehicles
should be smaller than the economic and practical considerations
suggest. This is because many will fail and in the numbers game
increasing the number of vehicles tried will pay greater dividends than
optimising individual designs for direct economic return. If the base
design works, it can be grown and economically optimised later. The
development methodology needs to move towards more, smaller, cheaper
vehicle prototypes. While individual likelihood of success will
decrease, total likelihood of success will increase. Making vehicles
bigger is not cheaper, people forget the cost savings associated with
the mass producing of smaller prototypes. This is a flight rate type
argument with regard to the design, build and testing of prototypes.
Build small and often.

Something which is critical in circumstances like this, but which gets
very little consideration, is that one would normally actively design
the development process. Right from the beginning one considers how one
can best minimise the cost of bending metal, how one can minimise the
cost of testing, how one can minimise individual prototype cost, how one
can minimise the time of the prototype cycle, (from conceptual design
through to testing), this is in part a numbers game and one needs to
stack the deck. If one can not prototype quickly, cheaply and
effectively, learning everything one can from each prototype and pouring
it into the next one, then one is not ready to start.

At this stage, vehicle design should be selecting primarily on the basis
of being fast, cheap and easy to continually prototype. This is not
something that most tend to consider. Designs just do not leap fully
developed off the drawing board. We are just not yet ready to start
bending metal, though some individuals are close.

Pete.







.

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