In article , "Paul Austin"
wrote:

"Harry Andreas" wrote in message
...
In article , "Paul Austin"
wrote:

There will be a B3 manned heavy bomber.
There's this problem. Nanotube-stiffened composites have
a_long_way to
go before anyone would use them for primary structure. The
nanotubes
themselves are gleams in folks eyes and based on carbon fiber
composite experience, there will be a fairly long learning
experience
before they are ready for prime time.

last time I heard just plain (not even woven) nanotube was
$2300/gram.

choke and I thought space-grade stuff was expensive. The price
will
come down as we learn to make them in industrial quantities but I
still don't see a pressing need to substantially lighter primary
structure in a bomb-truck.

It's only money for fuel and range limitations.

The lighter you can make the primary structure, the less power
it takes to fly your weapons. Better fuel fraction, less fuel used,
less $$, better range.

That's true but... Tell me again how a lighter weight airframe is
going to deliver more_military utility_than you can currently buy with
a B-2. Spirits are already miracles of load-carrying effciency and
with the advent of the Small Diameter Bomb, it's difficult to see how
a larger payload will be much more useful.

That's true, however, if you postulate the need for a new airframe
(mythical B-3) then there's no reason to stick with outdated
construction materials/techniques. The B-2 works well for 70/80's
technology.


As far as "less fuel used, less $$, better range" is concerned, fuel
cost is a tiny fraction of the life cycle cost of a heavy and as for
range, B-2s are already flying missions that strain crew endurance.

I would dispute this, although I have few figures to back it up.
Fuel costs are high on all military aircraft, and are getting higher.
Fuel costs vs LCC for heavies is misleading because the heavies sit
a lot more than tacair assets. In addition, all the assets
for air refueling that support the heavies are lumped in a different
bucket and not considered part of their LCC.


Substantially lighter airframes are going to be_very_expensive to
develop. You have to balance those costs against marginal improvements
in fuel consumption (since you aren't going to build a single-engined
heavy bomber).

It's never too early to plan, and it's never too early to conserve resources.

--
Harry Andreas
Engineering raconteur