Ariane Economies of Scale

"Paul F. Dietz" wrote in message ...
Ian Woollard wrote:

Not quite. By definition, SSTO has the same margin as a
technologically equivalent two-stager.

Not at all. For a given level of technology, the TSTO will
have more generous margins.

But increasing the margins is just using a lower level of technology.
I mean, the payload goes down. He said technologically equivalent.

Paul

On 15 Jul 2003 09:17:08 -0700, in a place far, far away,
(Ian Woollard) made the phosphor on my monitor
glow in such a way as to indicate that:

The payoff of the SSTO would be from expected lower operational
costs.

Yes, but because SSTO would have much less margin than a
(technology-equivalent) two-stage, lower operational costs may end up
being an illusion at current technology levels.

Not quite. By definition, SSTO has the same margin as a
technologically equivalent two-stager.

??

Not at all, if you really mean "technologically-equivalent."

Yes I do mean. It depends a little on what you mean by "technological
equivalent".

I mean similar materials and fabrication techniques, among other
things.

I took it to mean pretty much the same construction
techniques- same tankage weight, similar engine margins, similar fuels
etc. etc.

I don't really understand what you're saying here. The problem is,
that at a given technology level, you *can't* have the same margins in
a single-stage that you do in a multiple stage.

I mean, the whole point of TSTO is that it allows you to get away with
using a lower technology level doesn't it?

That's one way of looking at it, but it seems to go against what you
say above.

--
simberg.interglobal.org * 310 372-7963 (CA) 307 739-1296 (Jackson Hole)
interglobal space lines * 307 733-1715 (Fax) http://www.interglobal.org

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h (Rand Simberg) wrote in message ...
The problem is, that at a given technology level, you *can't*
have the same margins in a single-stage that you do in a multiple
stage.

Look, if you've got a SSTO, turning it into a TSTO is normally going
to be pretty easy and you certainly don't have to add margin and you
usually gain payload (for the same GLOW).

It may or may not be worth doing. But you can certainly do it.

I mean, the whole point of TSTO is that it allows you to get away with
using a lower technology level doesn't it?

That's one way of looking at it, but it seems to go against what you
say above.

No, all I'm saying is you can add margin if you want to. You're saying
it's impossible, that you HAVE to add margin. Uh, why? No.

On 15 Jul 2003 16:05:57 -0700, in a place far, far away,
(Ian Woollard) made the phosphor on my monitor
glow in such a way as to indicate that:

(Rand Simberg) wrote in message ...
The problem is, that at a given technology level, you *can't*
have the same margins in a single-stage that you do in a multiple
stage.

Look, if you've got a SSTO, turning it into a TSTO is normally going
to be pretty easy and you certainly don't have to add margin and you
usually gain payload (for the same GLOW).

If it's an SSTO that doesn't have sufficient margin to be operable,
then you have to add margin, if your purpose in making it a two stage
was to improve operability.

I mean, the whole point of TSTO is that it allows you to get away with
using a lower technology level doesn't it?

That's one way of looking at it, but it seems to go against what you
say above.

No, all I'm saying is you can add margin if you want to.

And you're mistaken.

At certain technology levels, you can't. With SSTO, at some point,
when you try to add margin, you start chasing your tail, and can't get
the design to close.

--
simberg.interglobal.org * 310 372-7963 (CA) 307 739-1296 (Jackson Hole)
interglobal space lines * 307 733-1715 (Fax) http://www.interglobal.org

"Extraordinary launch vehicles require extraordinary markets..."
Swap the first . and @ and throw out the ".trash" to email me.
Here's my email address for autospammers:

"Ian Woollard" wrote:
h (Rand Simberg) wrote in message
...
On 14 Jul 2003 20:48:55 -0700, in a place far, far away,
(Ian Woollard) made the phosphor on my monitor
glow in such a way as to indicate that:
Not quite. By definition, SSTO has the same margin as a
technologically equivalent two-stager.

??

Not at all, if you really mean "technologically-equivalent."

Yes I do mean. It depends a little on what you mean by "technological
equivalent". I took it to mean pretty much the same construction
techniques- same tankage weight, similar engine margins, similar fuels
etc. etc.

I mean, the whole point of TSTO is that it allows you to get away with
using a lower technology level doesn't it?

Not at all. I think you're looking at it in the wrong way.
If you have a maxed out SSTO I think you're imagining that
if you put another stage on top of it it'll just bite into
the payload. But, obviously, that's not how you'd do it.
Rather, you'd design a smaller version of the SSTO stage,
place it on top of (or wherever it'll fit) the original
stage, deduct the mass of the new stage from the propellant
mass of the first stage nee SSTO and now you have a two
stage vehicle with the same GLOW but with greater payload
(because the second stage doesn't have to accelerate the
entire dead weight of the first stage).

Yes, staging lets you get away with using "lower
technology", but it also substantially increases payload for
any given GLOW, regardless of the "technology level" used.

Not that that is necessarily a desirable goal, but it is
nevertheless true.

"Paul F. Dietz" wrote in message ...
Ian Woollard wrote:

Not at all. For a given level of technology, the TSTO will
have more generous margins.

But increasing the margins is just using a lower level of technology.

Wrong.

Proof by assertion? No. Try again.

Paul

h (Rand Simberg) wrote in message ...
On 15 Jul 2003 16:05:57 -0700, in a place far, far away,
(Ian Woollard) made the phosphor on my monitor
glow in such a way as to indicate that:

(Rand Simberg) wrote in message ...
The problem is, that at a given technology level, you *can't*
have the same margins in a single-stage that you do in a multiple
stage.

Look, if you've got a SSTO, turning it into a TSTO is normally going
to be pretty easy and you certainly don't have to add margin and you
usually gain payload (for the same GLOW).

If it's an SSTO that doesn't have sufficient margin to be operable,
then you have to add margin, if your purpose in making it a two stage
was to improve operability.

Yes, if and if.

I mean, the whole point of TSTO is that it allows you to get away with
using a lower technology level doesn't it?

That's one way of looking at it, but it seems to go against what you
say above.

No, all I'm saying is you can add margin if you want to.

With SSTO, at some point,
when you try to add margin, you start chasing your tail, and can't get
the design to close.

Obviously. But I was clearly talking about adding margin to the
'technologically equivalent' TSTO, not the SSTO. Everything else being
equal, you can always add some margin relative to the SSTO.

On 15 Jul 2003 23:37:02 -0700, in a place far, far away,
(Ian Woollard) made the phosphor on my monitor
glow in such a way as to indicate that:

If it's an SSTO that doesn't have sufficient margin to be operable,
then you have to add margin, if your purpose in making it a two stage
was to improve operability.

Yes, if and if.

Are we talking about some other circumstance?

I mean, the whole point of TSTO is that it allows you to get away with
using a lower technology level doesn't it?

That's one way of looking at it, but it seems to go against what you
say above.

No, all I'm saying is you can add margin if you want to.

With SSTO, at some point,
when you try to add margin, you start chasing your tail, and can't get
the design to close.

Obviously. But I was clearly talking about adding margin to the
'technologically equivalent' TSTO, not the SSTO. Everything else being
equal, you can always add some margin relative to the SSTO.

I'm sorry, but this is gibberish. I've no idea what idea you're
trying to convey here.

--
simberg.interglobal.org * 310 372-7963 (CA) 307 739-1296 (Jackson Hole)
interglobal space lines * 307 733-1715 (Fax) http://www.interglobal.org

"Extraordinary launch vehicles require extraordinary markets..."
Swap the first . and @ and throw out the ".trash" to email me.
Here's my email address for autospammers:

Ian Woollard wrote:

Proof by assertion? No. Try again.

For a given level of technology (materials strength, engine
thrust/weight, etc.) a TSTO can be designed with larger margins
on the structure/etc. than a SSTO. You end up with more wiggle
room to add (for example) thicker TPS.

This is so obvious that it's not clear why anything more
than a simple assertion is needed. Do you want me to use
words with fewer syllables?

Paul

h (Rand Simberg) wrote in message ...
On 15 Jul 2003 16:05:57 -0700, in a place far, far away,
(Ian Woollard) made the phosphor on my monitor
glow in such a way as to indicate that:

....snip...

No, all I'm saying is you can add margin if you want to.

And you're mistaken.

At certain technology levels, you can't. With SSTO, at some point,
when you try to add margin, you start chasing your tail, and can't get
the design to close.

Yes. About the only way that I have found to add
margin to an SSTO is to make it bigger. And at the
point that this starts to happen--at a gross mass
of perhaps 750 to 1000 tonnes--the investment is a
killer for a first-generation commercial project.

Moreover, a space transport needs a high traffic
level measured primarily by the number of flights
--not by the total payload tonnage. Ergo: TSTO
seems to be the only viable route for a
first-generation, commercial space transport.

Best regards,
Len (Cormier)
PanAero, Inc. and Third Millennium Aerospace, Inc.
( http://www.tour2space.com )