Spaceship One stepping-stone or dead-end?

In article ,
jacob navia wrote:
Earth orbit however needs substantially (a factor of 9) more speed
and this means at least a factor of 9 of costs to get it.

Except that twice as fast isn't twice as expensive. In practice twice as
fast is usually between 4 and 8 times as expensive (*). If you multiply
Rutan's $20+ million by 9^2, you get more than $1.6 billion.

(*) This assumes a fair comparison rather than a silly one like a used
Corvette vs. a new Winnebago.

--
/\ Greg Kuperberg (UC Davis)
/ \ Home page: http://www.math.ucdavis.edu/~greg/
\ / Visit the Math ArXiv Front at http://front.math.ucdavis.edu/
\/ * All the math that's fit to e-print *

On Thu, 30 Sep 2004 19:09:58 +0000 (UTC), in a place far, far away,
(Greg Kuperberg) made the phosphor on my monitor
glow in such a way as to indicate that:

In article ,
jacob navia wrote:
Earth orbit however needs substantially (a factor of 9) more speed
and this means at least a factor of 9 of costs to get it.

Except that twice as fast isn't twice as expensive. In practice twice as
fast is usually between 4 and 8 times as expensive (*).

There is no such simple relationship between speed and development
cost. Your calculation is pointless.

"Greg Kuperberg" wrote in message
...
In article ,
jacob navia wrote:
Earth orbit however needs substantially (a factor of 9) more speed
and this means at least a factor of 9 of costs to get it.

Except that twice as fast isn't twice as expensive. In practice twice as
fast is usually between 4 and 8 times as expensive (*). If you multiply
Rutan's $20+ million by 9^2, you get more than $1.6 billion.

I'm not sure if this metric is true, but even if it is, this would still be
far less than NASA spent to develop the shuttle.

Jeff
--
Remove icky phrase from email address to get a valid address.

On Thu, 30 Sep 2004 15:43:43 -0400, in a place far, far away, "Jeff
Findley" made the phosphor on my monitor
glow in such a way as to indicate that:

Earth orbit however needs substantially (a factor of 9) more speed
and this means at least a factor of 9 of costs to get it.

Except that twice as fast isn't twice as expensive. In practice twice as
fast is usually between 4 and 8 times as expensive (*). If you multiply
Rutan's $20+ million by 9^2, you get more than $1.6 billion.

I'm not sure if this metric is true, but even if it is, this would still be
far less than NASA spent to develop the shuttle.

It also completely ignores vehicle size. It's a completely
meaningless number, but then, Greg, being a mathematician and all, is
probably quite comfortable with meaningless numbers.

In article ,
Jeff Findley wrote:
"Greg Kuperberg" wrote in message
...
Except that twice as fast isn't twice as expensive. In practice twice as
fast is usually between 4 and 8 times as expensive (*). If you multiply
Rutan's $20+ million by 9^2, you get more than $1.6 billion.
I'm not sure if this metric is true, but even if it is, this would still be
far less than NASA spent to develop the shuttle.

That's true, but in one respect it's not a fair comparison. In the
part of my post that you deleted, I asked for a fair comparison, not
a silly one like a Corvette vs. a Winnebago. The shuttle really is the
Winnebago of spacecraft. If you extended this analogy to "SpaceShip One",
it would be akin to a go-cart.

In another respect, it is fair enough, in that the whole problem with
many government projects is that they are bloated, like Winnebagos.
But then, that could be an indictment of manned spaceflight in general,
not just the shuttle.

Besides, a factor of n^2 in cost for a factor of n in speed is, if
anything, low-balling it.
--
/\ Greg Kuperberg (UC Davis)
/ \ Home page: http://www.math.ucdavis.edu/~greg/
\ / Visit the Math ArXiv Front at http://front.math.ucdavis.edu/
\/ * All the math that's fit to e-print *

In article ,
Rand Simberg wrote:
On Thu, 30 Sep 2004 19:09:58 +0000 (UTC), in a place far, far away,
(Greg Kuperberg) made the phosphor on my monitor
glow in such a way as to indicate that:
Except that twice as fast isn't twice as expensive. In practice twice as
fast is usually between 4 and 8 times as expensive (*).
There is no such simple relationship between speed and development
cost. Your calculation is pointless.

Of course it's not a law of physics or anything like that. But has been
true in practice for comparable vehicles, i.e., comparable capacity,
luxury level, and engineers.
--
/\ Greg Kuperberg (UC Davis)
/ \ Home page: http://www.math.ucdavis.edu/~greg/
\ / Visit the Math ArXiv Front at http://front.math.ucdavis.edu/
\/ * All the math that's fit to e-print *

On Thu, 30 Sep 2004 20:00:42 +0000 (UTC), in a place far, far away,
(Greg Kuperberg) made the phosphor on my monitor
glow in such a way as to indicate that:

Besides, a factor of n^2 in cost for a factor of n in speed is, if
anything, low-balling it.

No. As I said, there is no such simple relationship, except for
simple minds.

"MichaelJP" writes:

Would appreciate any links, references?

Thanks,
- MP

For starters, look at XCOR's proposed Xerus.

(Greg Kuperberg) wrote in message ...

Except that twice as fast isn't twice as expensive. In practice twice as
fast is usually between 4 and 8 times as expensive (*). If you multiply
Rutan's $20+ million by 9^2, you get more than $1.6 billion.

Thanks for playing "guess this parameter," but your guess is not even
close.

According to the DAPCA IV model, engineering costs scale with V^0.9,
tooling costs scale with V^0.7, and manufacturing costs scale with
V^0.5.

(*) This assumes a fair comparison rather than a silly one like a used
Corvette vs. a new Winnebago.

That's what happens when you assume.

(Greg Kuperberg) wrote in message ...

Of course it's not a law of physics or anything like that. But has been
true in practice for comparable vehicles, i.e., comparable capacity,
luxury level, and engineers.

No, it hasn't. You're assuming cost squares with the square or cube of
velocity. In reality, it's closer to the square *root* of velocity.

There are other variables, which you're ignoring, but even if we
control for all those variables, you aren't close to being correct.