Re: Why superships cost more per mass

The question isn't is a Battleship more complex
and harder to build than a Destroyer. The question
is is a 200 mass battleship more trouble/complex/
expensive to build than 4 50 mass destroyers all
put together. Are there really more points of
failure between say 1 big engine and 4 smaller
engines? Is it easier to maintain 2 small honda
motorcycle engines than 1 larger honda car engine?

Ok, so I'm not a naval architect or a construction
engineer on ships. Is there anyone on the list who
DOES have actual direct experience -- i.e. who is
a real expert? If not, all we have is speculation.

Remember I've already conceded that if you're trying
to build a 250 mass ship and you've only ever built
150 mass ships, you'll definitely have more than a
linear collection of problems. But if you're say the
US and you decide you need another Aircraft Carrier,
that at least is something you've done before. You
may add some improvements, and some of those could
have their difficulties, but the basic job has already
been done many times over. Our shipbuilders already
know how to build our nuclear aircraft carriers.

Likewise if you're building your first aircraft
carrier and you've never done carrier air operations
before and you've never built a catapult before and
you've never had ships with that many crew before
etc etc etc. THEN you better stand by for many times
your weight in wildcats (or Kzinti).

--- agoodall@canada.com wrote:
> On Fri, 29 June 2001, David Griffin wrote:
> 
> > I don't know much about the Canadian navy, but if
> > they were working on a class of ship they're used
> > to working on, and they weren't trying to do
> anything
> > they hadn't done before, then I don't think size
> > would have that much to do with their overruns.
> 
> Even if you have a robotic ship building facility,
> complexity still increases with size, and as Tom
> pointed out it isn't linear.
> 
> As the ship gets bigger, you have more "connectors"
> (whether it be points where load bearing members
> connect and have to be welded, or points where
> wires/fibres connect, or weapon mounts, what have
> you). You have more of them, because your ship is
> bigger. Each one of these is a potential point of
> failure. If you have 10 connectors in a destroyer
> and 100 connectors, you have 10 times the number of
> failure points in the larger ship. The larger ship
> will likely have 10 times the failures of these
> parts.
> 
> However, there is a cascade relationship happening.
> One part breaks down, resulting in stresses on other
> parts. This cascading effect is worse in the big
> ship, and is the reason the complexity isn't linear.
> 
> Anyone in engineering, or in programming, knows
> this. A 500,000 line program is more than 10 times
> more prone to failure than a 50,000 line program.
> 
> Now, throw into the mix the fact that other people
> are TRYING to make these things break. They are
> warships, after all.
> 
> Even if building them is automated, a bigger ship
> will be more complex than a smaller ship, and more
> than just in proportion to the size difference.
> 
> Allan Goodall - agoodall@canada.com
>
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