Ariane Economies of Scale

Rand Simberg wrote:
On Thu, 03 Jul 2003 08:55:46 -0700, in a place far, far away, Hop
David made the phosphor on my monitor
glow in such a way as to indicate that:


I was surprised to see a figure as low as 30% quoted.


For only a doubling?


Besides gain in experience aren't costs of tools, dies etc.
amortized in quantities?

Please forgive some of my naive questions, I haven't been reading this
newsgroup long.

What kind of production runs are being hoped for? 100 units? 1000?


Not for Arianes

For what kind of craft?



It's hoped that the satellite market plus space tourism would make this
sort of investment attractive?


No, those are separate markets, and they'll be served by different
vehicles. The satellite market will never be large enough to drive
the development of low-cost launchers, though it will take advantage
of them when they appear.

The economies of scale that we (or at least I) refer to are in
operations of a reusable space transport, not manufacturing quantities
of expendables.


I seem to recall a discussion that reusable space craft require huge,
massive fuel tanks. Is this a physics mandated expense that couldn't be
overcome by better business practices?


No, but large "massive" (not sure what that word means in this
context, other than that it isn't massless) fuel tanks aren't a
significant cost driver.

Multi-stage rockets discard stages to decrease the mass that has to be
accelerated. If you don't discard the stages aren't the rocket engines
pushing a lot more dead mass in the form of empty tanks? Perhaps I'm in
error equating reusable vehicles to single stage to orbit vehicles.

Hop
http://clowder.net/hop/index.html

On Thu, 03 Jul 2003 17:41:45 -0700, in a place far, far away, Hop
David made the phosphor on my monitor
glow in such a way as to indicate that:

What kind of production runs are being hoped for? 100 units? 1000?


Not for Arianes

For what kind of craft?

Not for any expendable, as far as I know.

I seem to recall a discussion that reusable space craft require huge,
massive fuel tanks. Is this a physics mandated expense that couldn't be
overcome by better business practices?


No, but large "massive" (not sure what that word means in this
context, other than that it isn't massless) fuel tanks aren't a
significant cost driver.

Multi-stage rockets discard stages to decrease the mass that has to be
accelerated. If you don't discard the stages aren't the rocket engines
pushing a lot more dead mass in the form of empty tanks?

Yes, but that's not a cost driver, as long as there's adequate level
of operations. It's like saying, "we can't afford to carry these
wings and fuel tanks along on these airplanes--it just costs too much
in fuel to carry them...

Perhaps I'm in
error equating reusable vehicles to single stage to orbit vehicles.

That is an error, but it's not your primary error.

--
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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Rand Simberg wrote:
On Thu, 03 Jul 2003 17:41:45 -0700, in a place far, far away, Hop
David made the phosphor on my monitor
glow in such a way as to indicate that:


What kind of production runs are being hoped for? 100 units? 1000?


Not for Arianes

For what kind of craft?


Not for any expendable, as far as I know.


I seem to recall a discussion that reusable space craft require huge,
massive fuel tanks. Is this a physics mandated expense that couldn't be
overcome by better business practices?


No, but large "massive" (not sure what that word means in this
context, other than that it isn't massless) fuel tanks aren't a
significant cost driver.

Multi-stage rockets discard stages to decrease the mass that has to be
accelerated. If you don't discard the stages aren't the rocket engines
pushing a lot more dead mass in the form of empty tanks?


Yes, but that's not a cost driver, as long as there's adequate level
of operations. It's like saying, "we can't afford to carry these
wings and fuel tanks along on these airplanes--it just costs too much
in fuel to carry them...

Are airplanes a good comparison?

4.5 km/second is near the top exhaust velocity for chemical rockets, no?
So if I wanted to achieve 11.2 km/sec the ratio of
(Mpayload+Mfuel)/Mpayload would = e^(11.2/4.5) which is about 12.

Is it typical for a plane mass at take off to be 11/12 fuel?

And say in addition to 11.2 you wanted to do Hohmann insertion and exit
to elsewhere in the solar system you could easily total 17 km/sec. I
think fuel would be about 43/44 of take off mass. In this scenario I'd
want to have expendable tanks so as to reduce payload mass.

But I'd venture a guess that the reusable craft you hope to see mass
produced wouldn't be doing that sort of delta V.

Hop
http://clowder.net/hop/index.html

On Fri, 04 Jul 2003 12:16:27 -0700, in a place far, far away, Hop
David made the phosphor on my monitor
glow in such a way as to indicate that:


Yes, but that's not a cost driver, as long as there's adequate level
of operations. It's like saying, "we can't afford to carry these
wings and fuel tanks along on these airplanes--it just costs too much
in fuel to carry them...

Are airplanes a good comparison?

They're not a bad one. The biggest difference between space
transports and air transports (right now) is market size.

4.5 km/second is near the top exhaust velocity for chemical rockets, no?
So if I wanted to achieve 11.2 km/sec the ratio of
(Mpayload+Mfuel)/Mpayload would = e^(11.2/4.5) which is about 12.

Is it typical for a plane mass at take off to be 11/12 fuel?

No, but it's not unheard of.

And say in addition to 11.2 you wanted to do Hohmann insertion and exit
to elsewhere in the solar system you could easily total 17 km/sec.

That would be silly. There's a good reason we stage rockets.

But I'd venture a guess that the reusable craft you hope to see mass
produced wouldn't be doing that sort of delta V.

No, LEO is plenty, and there's no need to do it in a single stage.

--
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..."
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On 4 Jul 2003 22:43:54 GMT, in a place far, far away, Jim Davis
made the phosphor on my monitor glow in such
a way as to indicate that:

Is it typical for a plane mass at take off to be 11/12 fuel?

No, but it's not unheard of.

???

Care to give an example?

The record for fuel fraction on take off as far as I know is Rutan's
Voyager at about 75%.

That was the example I had in mind. I thought it was a much higher
fraction than that.

Of course, those numbers are irrelevant as long as you're not a true
believe (as I'm not) in SSTO.

--
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..."
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On Sat, 05 Jul 2003 15:20:50 -0700, in a place far, far away, Hop
David made the phosphor on my monitor
glow in such a way as to indicate that:

In a multistage, the discarded stages are expendable, no?

By definition, yes, but there's no need for "discarded stages." First
stages can fly back.

--
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..."
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On Sat, 05 Jul 2003 23:02:49 GMT, in a place far, far away, Michael
Walsh made the phosphor on my monitor glow in
such a way as to indicate that:


The only virtue that a SSTO has over a TSTO (two stage to orbit) reusable
vehicle is the reduction in cost by developing and using only one vehicle
instead of two.

There are also theoretical operational cost reductions by not having
to mate the vehicles in turnaround, but at the current state of
technology it's not clear that the loss of performance margin of a
single stage doesn't wipe out this advantage.

--
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..."
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Rand Simberg wrote:

On Sat, 05 Jul 2003 23:02:49 GMT, in a place far, far away, Michael
Walsh made the phosphor on my monitor glow in
such a way as to indicate that:

The only virtue that a SSTO has over a TSTO (two stage to orbit) reusable
vehicle is the reduction in cost by developing and using only one vehicle
instead of two.

There are also theoretical operational cost reductions by not having
to mate the vehicles in turnaround, but at the current state of
technology it's not clear that the loss of performance margin of a
single stage doesn't wipe out this advantage.

OK, but that is just a clarification of what I posted.

Not having to mate vehicles in turnaround is certainly part of a reduction
in cost by using only one vehicle instead of two.


Mike Walsh

"Hop David" wrote in message
...
Not having to mate vehicles in turnaround is certainly part of a
reduction
in cost by using only one vehicle instead of two.

Is mating vehicles difficult?

In the case of the shuttle, it is. Simply lifting the orbiter into position
for mating takes around 8 hours. Hard-mate generally takes around 18-24
hours, if all goes well. The entire process of completing mechanical and
electrical connections, plus checkout of the integrated stack takes about
five days of round-the-clock effort (been there, done that).

In the case of a two-stage RLV, where there is no need for propellant
transfer, the connection process would be greatly simplified, with the bulk
of time and effort most likely being consumed by the tedious positioning
process, where the second stage is placed in position for soft, then hard,
mating. Electrical connection and checkout would likely be greatly reduced.

-Kim-

On Mon, 07 Jul 2003 00:32:06 GMT, in a place far, far away, Michael
Walsh made the phosphor on my monitor glow in
such a way as to indicate that:

The only virtue that a SSTO has over a TSTO (two stage to orbit) reusable
vehicle is the reduction in cost by developing and using only one vehicle
instead of two.

There are also theoretical operational cost reductions by not having
to mate the vehicles in turnaround, but at the current state of
technology it's not clear that the loss of performance margin of a
single stage doesn't wipe out this advantage.

OK, but that is just a clarification of what I posted.

Yes, because I (perhaps mistakenly) inferred that you were saying that
the main problem was development.

--
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..."
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