[ExI] Risks on large scale and long term projects/was Re: Power satellites
dan_ust at yahoo.com
dan_ust at yahoo.com
Thu Apr 23 20:38:00 UTC 2009
--- On Thu, 4/23/09, Keith Henson <hkeithhenson at gmail.com> wrote:
> On Thu, Apr 23, 2009 at 6:18 AM, Dan
> <dan_ust at yahoo.com>
> > --- On Wed, 4/22/09, Keith Henson <hkeithhenson at gmail.com>
> >> On Wed, Apr 22, 2009 at 6:20 AM, Dan
> >> <dan_ust at yahoo.com>
> >> wrote:
> >>> I would not use a hypothetical, untested
> technology as
> >> my "gold standard for space transport."
> >> "Gold standard" in this context means, "Yah can't
> >> betta:" I.e., it
> >> is as the limit.
> > I think you could: nuclear pulse propulsion from the
> surface. I haven't run the numbers, but there'd be no need
> for the huge capital investment of a space elevator AND most
> of the technology for it'd be off-the-shelf. No need to
> develop nanotech further. In fact, my guess is one could
> do nuclear pulse propulsion with decades old tech. (Of
> course, there's the problem of pollution.)
> Nuclear pulse is a reaction technique. All reaction
> engines are
> rotten at energy efficiency--which hardly matters with
> nuclear energy.
I was thinking -- as I stated -- in terms of costs: lower capital investment, shorter development time, and lower overall risk. Plus, think of the final product: you'd probably have several nuclear pulse rockets for the price of one space elevator. If one of those rockets fails, you still have the others. If the single space elevator fails, you have to build another one and fall back on non-space elevator means to get to orbit. (Of course, if space elevators do happen, there'd likely be more than one.)
> > Until you've built and tested one, you can't know the
> costs -- which are economic -- or the physical efficiencies
> of an actual space elevator. Were this not the case, there
> would never be any need for quality assurance and quality
> control; everything would simply worked as conceived. You
> can, of course, make guesses, but, looking at past large
> scale engineering projects -- especially, ones for space
> travel -- it seems to me these guesses are often way off the
> mark. (One can make similar claims about nuclear pulse
> propulsion, though it has a longer history and actual tests
> were done years ago with much of the underlying technology.
> Certainly, nuclear weapons have been extensively
> My claim, space elevators, like common building elevators,
> would be
> upwards of 90 % efficient in converting electrical energy
> potential energy. If your claim is that you don't
> have any confidence
> in this figure, why? I.e., energy is conserved, where
> is going to go?
Simple: you have to build one to see what the actual efficiencies are. This has yet to be done. Until then, these are hypothetical efficiencies. They might be a good ballpark, but it seems more like what's being assumed is the best case scenario with little attention paid to things not going right.
> To be sure, when working on ambitious projects with a lot
> of R&D there
> is uncertainty in the cost. But that's not the reason
> for quality
> control. You need quality control on railroad
> axles. For the most
> part stuff does work as conceived. But "as conceived"
> may include
> proper heat treatment. I remember a case of a carrier
> aircraft with
> fold up wings where the hinge pins were not properly heat
> The wings fell off, fortunately not in the air.
> The space shuttle/space station went way over budget, but
> that can
> mostly be traced to political decisions that forced
> underestimate of
> the cost.
Do you believe a space elevator will avoid the averse effects of "political decisions"? Is anyone seriously planning to build it completely without any political input?
Also, there are still many unknowns with a space elevator. One has yet to be built and the closest thing to it, space tethers, are not a proven technology either. It'd be a lot different if you lived in a world where space tethers were commonplace -- a mature and proven technology -- and large-scale nanoenegineering. These may yet come to pass, but, until they do, there are still huge financial and engineering risks with this kind of large scale project.
> There is a lot of commonality with aircraft
> design and
> that's fairly well understood.
> You might note that the Three Gorges dam came in under
Government project in a nation that doesn't have independent auditing techniques. I'd hardly rely on that one example to bolster my case -- and it's funny that that's one of the rare cases where a large engineering project came in under budget. You might want to look at a larger data sample, especially including most other large scale engineering projects and especially space projects -- both sets of which tend to have large political components.
Also, aside from political components, any project that takes a long time to complete -- all else being equal -- is going to have more risk. The longer it takes, the more things there are that can go wrong, all else remaining the same.
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