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------------------------------
Date: 29 Jul 93 02:32:47 GMT
From: Henry A Worth <haw30@ras.amdahl.com>
Subject: In article 876@access.digex.net, prb@access.digex.net (Pat) writes:
Newsgroups: sci.space
>
> Michael Jensen again shows his lack of Knowledge....
>
>
> For what it's worth, The DC-3 was very high Risk for it's
> time and considered very experimental..
>
> a 2 Engine Plane for Oceanic Flight??????
>
The single-engine performance issue for the DC-3 and its predecessors was not trans-Oceanic, it was trans-Rockies. Demonstrating a crossing with a single-engine shut-down was an important milestone in getting CAA certification for mountain operations and the Airlines were reluctant to order until it had that certification
(if memory serves, the demo was Phoenix to Denver in a DC-2, and required a portion
of the climb to be made single-engine). Prior to the DC-2/3, trans-Rockies scheduled
passenger flights required tri-motors and were often substituted for by rail links.
The DC-3 did not have the range for trans-Oceanic operations (island hopping doesn't count), that had to wait for the DC-6 (I think even the DC-4 required favorable
winds and payload for even the shortest non-stop trans-Alantic routes, and was used
on such routes primarily as a VIP and critical-freight hauler during WWII, and even
then diversions to Greenland or Iceland were common, if not the norm).
The DC-2 and DC-3 differ primarily in a larger cabin cross-section for the DC-3.
They were similar enough that during WWII, DC-2's were often canabalized to repair DC-3's, and on at least one occasion a DC-2 wing was mated to a DC-3 resulting in
the rather well known DC-2 1/2 (there were slight differences in the wing).
---
Henry Worth
No, I don't speak for Amdahl... I'm not even sure I speak for myself.
------------------------------
Date: Wed, 28 Jul 1993 23:12:13 GMT
From: Gary Coffman <ke4zv!gary>
Subject: Low Tech Alternatives, Info Post it here!
Newsgroups: sci.space
In article <1993Jul28.175458.9978@cs.rochester.edu> dietz@cs.rochester.edu (Paul Dietz) writes:
>
>It should be clear that some optimum cost vs. performance point must
>exist for launch vehicle hardware. What evidence is there that we are
>on the low-performance side of that point? Analysts in the 60s
>concluded that, in fact, we were on the high side, and should make
>less sophisticated, less complex vehicles, whose poorer mass ratio was
>more than offset by much lower per pound construction cost. We make
>cars out < $1/lb sheet steel, not $1,000/lb exotic composites. It is
>not clear why rockets should be any different.
Autos are produced by the millions, rockets by the tens. Hand built
Ferraris use $1,000/lb exotic composites too. Even Peterbilt is going
to carbon fiber, fiberglass, and aluminum for over the road trucks. If
GM can save $.01 a car, they make $5,000,000 additional profit per year.
But that doesn't apply in small production runs. There, a few dollars
one way or the other doesn't make much difference. Most of the cost of
building a rocket is in the hand labor, and launch preparation, and
launch operations, not the materials.
For a really big rocket, Sea Dragon comes to mind, shipyard materials
and shipyard techniques make sense. But for the run of the mill small
rockets we use, and the small numbers we launch, we can use the best
materials so we can get the most from each launch. The cost of launcher
materials is one of the smaller costs in the total picture of getting
a payload into orbit and operating it there.
Gary
--
Gary Coffman KE4ZV | You make it, | gatech!wa4mei!ke4zv!gary
Destructive Testing Systems | we break it. | uunet!rsiatl!ke4zv!gary
534 Shannon Way | Guaranteed! | emory!kd4nc!ke4zv!gary
Lawrenceville, GA 30244 | |
------------------------------
Date: Thu, 29 Jul 1993 03:25:59 GMT
From: Paul Dietz <dietz@cs.rochester.edu>
Subject: Low Tech Alternatives, Info Post it here!
Newsgroups: sci.space
In article <1993Jul28.231213.9082@ke4zv.uucp> gary@ke4zv.UUCP (Gary Coffman) writes:
> Autos are produced by the millions, rockets by the tens. Hand built
> Ferraris use $1,000/lb exotic composites too.
Hardly that expensive! The composites used in low volume auto
manufacturing are mostly fiberglass, which is more expensive than
steel, but not enormously more expensive. Commercial E-glass costs
only a few dollars per pound. Note, however, that the fiberglass is
used in places where very high strength is not important.
> Even Peterbilt is going
> to carbon fiber, fiberglass, and aluminum for over the road trucks. If
> GM can save $.01 a car, they make $5,000,000 additional profit per year.
> But that doesn't apply in small production runs. There, a few dollars
> one way or the other doesn't make much difference. Most of the cost of
> building a rocket is in the hand labor, and launch preparation, and
> launch operations, not the materials.
The materials you list for Peterbilt are still nowhere near the
expense of aerospace composites. Moreover, I would be surprised if
Peterbilt is putting them into places where strength is crucial,
like the major loadbearing members.
The fact that things are built by hand does not necessarily make
expensive materials better. Consider the experience with the
prototype steel tanks manufactured (by hand) by Boeing for the cost
optimized booster project in the late 60s. They found reduction in
the per-pound cost of fabricated, tested steel tanks of an order of
magnitude over then-standard aluminum alloy tanks. The reduction in
cost was due to a more forgiving, if lower performance, material, and
wider margins. I shudder to think what those tanks would have cost if
made of aerospace grade graphite-epoxy.
Paul F. Dietz
dietz@cs.rochester.edu
------------------------------
Date: Thu, 29 Jul 1993 03:01:40 GMT
From: "Alex C. Anderson" <andersan@apollo14.ecn.purdue.edu>
Subject: Low Tech Alternatives, Info Post it here!
Newsgroups: sci.space
The thread on low-cost spaceflight touches on one subject that doesn't
seem to be covered very well when people discuss spaceflight, and that is
the actual cost for really putting something into say LEO, or even just
a spounding rocket flight. I'm not talking about the "cost" we are given
for a shuttle launch; that can be argued back and forth for all eternity
with people wantiong to include this or that cost. I heard from someone at
Wallops that when they helped with a small commercial launch a few years ago
(I think it was a Conestoga?) that the rocket cost was allegedly a few
hundred thousand, but with the attendant launch ops the real figure was
over a million.
If anyone out there has actual exp[erience or good information about costing
for these things, I would be interested in hearing about it in detail - with
an idea of where the numbers come from, too. I've seen so many figur
them is, I find it hard to believe anyone's cost estimate for a hammer, let
