A Space & astronomy forum. SpaceBanter.com

Go Back   Home » SpaceBanter.com forum » Space Science » Space Science Misc
Site Map Home Authors List Search Today's Posts Mark Forums Read Web Partners

Moral Equivalent Of A Space Program



 
 
Thread Tools Display Modes
  #41  
Old February 15th 06, 10:25 AM posted to sci.space.moderated,sci.space.policy
external usenet poster
 
Posts: n/a
Default Moral Equivalent Of A Space Program

In article ,
Fred J. McCall wrote:
Seems to me that it's expensive enough to get mass up there that we
ought to plan on not bringing it back.


And a space station, in particular, *wants* to be as heavy as possible --
that reduces the effect of air drag and hence the frequency of reboosts.

(The average annual reboost fuel consumption is, to a good first
approximation, unaffected. The reboosts take more fuel each, but they're
less frequent.)
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |

  #42  
Old February 15th 06, 01:33 PM posted to sci.space.moderated,sci.space.policy
external usenet poster
 
Posts: n/a
Default Moral Equivalent Of A Space Program

On Wed, 15 Feb 2006 04:15:41 -0500, in a place far, far away, "Fred J.
McCall" made the phosphor on my monitor glow
in such a way as to indicate that:

::No, I told you. Add up the development costs, and the ongoing
:perational costs (including the costs of launching the cargo that is
::no longer launched by the manned vehicle, but can be by the Shuttle),
::divide by the flight rates, and you get an infrastructure that costs
::as much, or more than, the Shuttle. Even ignoring the amortization of
::the development costs, the marginal costs of the Shaft + CEV launch
::will be at least a couple hundred million, to deliver four crew
::instead of seven. Shuttle's marginal cost are about the same, to
::deliver a crew of seven, plus fifty thousand pounds of payload.
:
:Except you cheat the numbers because you don't include the development
:and infrastructure development costs of the Shuttle in *that* number.
:
:That is not *cheating*. I told you, they're sunk. We have no choice
ver whether or not to spend them, because that expenditure has
:already taken place, and we don't have a time machine. When you're
:making a decision to make a future investment in something that's
stensibly to save you money, you *have to* include the investment as
art of the total costs.

Note that this is *NOT* the same question as whether it would be
cheaper to get a pound to orbit than Shuttle. You're now asking if it
makes free-market economic sense - and you haven't answered that
question adequately, either.


Either in the free market, or in a government expenditure, an economic
decision has to be based on future costs, not sunk ones. There's an
expression for your kind of thinking--"throwing good money after bad."

  #43  
Old February 15th 06, 03:23 PM posted to sci.space.moderated,sci.space.policy
external usenet poster
 
Posts: n/a
Default Why The SM? (was Moral Equivalent Of A Space Program)

Rand Simberg wrote:

And the CaLV is already maxed out carrying the LSAM and EDS.


It would be easier (and make more sense) to make that bigger, than the
Satay.



You would prefer NASA to make an even larger CaLV than it plans to?

Who are you and what have you done with Rand Simberg?

Will McLean

  #44  
Old February 15th 06, 03:28 PM posted to sci.space.moderated,sci.space.policy
external usenet poster
 
Posts: n/a
Default Why The SM? (was Moral Equivalent Of A Space Program)

On Wed, 15 Feb 2006 09:23:49 -0500, in a place far, far away, "Will
McLean" made the phosphor on my monitor glow in
such a way as to indicate that:

Rand Simberg wrote:

And the CaLV is already maxed out carrying the LSAM and EDS.


It would be easier (and make more sense) to make that bigger, than the
Satay.



You would prefer NASA to make an even larger CaLV than it plans to?


No, I'd prefer that they dump ESAS entirely. But if you're going to
build a heavy lifter, you might as well make it heavy (they're talking
about a mondo grosso one for the Mars missions anyway). If the
philosophy is to have a launcher dedicated to crew launches, and put
everything else up on the heavy, then truly dedicate it to crew, and
make the job easier on it.

  #46  
Old February 16th 06, 10:50 AM posted to sci.space.moderated,sci.space.policy
external usenet poster
 
Posts: n/a
Default Moral Equivalent Of A Space Program

h (Rand Simberg) wrote:

:On Wed, 15 Feb 2006 04:15:41 -0500, in a place far, far away, "Fred J.
:McCall" made the phosphor on my monitor glow
:in such a way as to indicate that:
:
:::No, I told you. Add up the development costs, and the ongoing
::perational costs (including the costs of launching the cargo that is
:::no longer launched by the manned vehicle, but can be by the Shuttle),
:::divide by the flight rates, and you get an infrastructure that costs
:::as much, or more than, the Shuttle. Even ignoring the amortization of
:::the development costs, the marginal costs of the Shaft + CEV launch
:::will be at least a couple hundred million, to deliver four crew
:::instead of seven. Shuttle's marginal cost are about the same, to
:::deliver a crew of seven, plus fifty thousand pounds of payload.
::
::Except you cheat the numbers because you don't include the development
::and infrastructure development costs of the Shuttle in *that* number.
::
::That is not *cheating*. I told you, they're sunk. We have no choice
:ver whether or not to spend them, because that expenditure has
::already taken place, and we don't have a time machine. When you're
::making a decision to make a future investment in something that's
:stensibly to save you money, you *have to* include the investment as
:art of the total costs.
:
:Note that this is *NOT* the same question as whether it would be
:cheaper to get a pound to orbit than Shuttle. You're now asking if it
:makes free-market economic sense - and you haven't answered that
:question adequately, either.
:
:Either in the free market, or in a government expenditure, an economic
:decision has to be based on future costs, not sunk ones. There's an
:expression for your kind of thinking--"throwing good money after bad."

And there's an expression for yours, as well - "comparing marginal
costs to fully burdened development costs".

In other words, you compare apples to aardvarks. In even simpler
terms, you cheat the numbers.

To answer the original question, you have to compare marginal costs to
marginal costs.

To answer the issue you now bring up above, you have to compare fully
burdened costs to fully burdened costs OVER THE EXPECTED LIFESPAN OF
THE SYSTEM.

You do neither.

--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn

  #48  
Old February 18th 06, 12:25 PM posted to sci.space.moderated,sci.space.policy
external usenet poster
 
Posts: n/a
Default Moral Equivalent Of A Space Program

In article , Gene Cash wrote:
And a space station, in particular, *wants* to be as heavy as possible...
(The average annual reboost fuel consumption is, to a good first
approximation, unaffected. The reboosts take more fuel each, but
they're less frequent.)


Hm. I think I'd consider fuel budget more important than frequency of
reboosts.


Note what I said: the fuel budget is *unaffected*. Loosely speaking, the
requirement for reboost is that reboost thrust, averaged over the period
between reboosts, equal the air-drag force averaged over the same period.
Station frontal area affects fuel budget, but station mass does not.

The one place where mass makes a difference to reboosts is that it slows
down the effects of air drag. So if you reboost at the same frequency,
your altitude varies over a narrower range, while if you let the altitude
vary over the same range, reboosts are less frequent.

I didn't think a reboost was that inconvenient, if you have to
haul up the extra station mass *and* more fuel to keep it in orbit.


Please read what I wrote: you *don't* need more fuel. And the mass in
question is stuff that is already being hauled up there; the question is
whether to go to added inconvenience to get rid of it.

Reboosts actually are inconvenient, not least because they disrupt the
microgravity environment that is one major reason to have a station.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |

  #49  
Old February 18th 06, 04:32 PM posted to sci.space.moderated,sci.space.policy
external usenet poster
 
Posts: n/a
Default Why The SM? (was Moral Equivalent Of A Space Program)

Ed Kyle wrote:

The choice of an Apollo-like ablative heat shield means that
trying to protect propulsion module equipment, especially
an engine bell, would add a lot of mass to the reentry
module, and probably drive up overall spacecraft mass.
When the reentry module gets heavier, parachute (and
terminal retro) recovery systems get more complicated in
a hurry too. If they used a lighter heat shield system
(shuttle tiles?), it might be an easier problem to tackle.



Of course you could go the Russian VA capsule route and put the retro
system on the top of the capsule rather than on its base, and turn it
into a jettisonable unit to decrease landing weight.
You really want to save landing weight, jettison the whole heatshield
after reentry like Soyuz does.
Another problem with putting the retro/manuvering engines in the CEV CM
itself would be noise when they are fired.

Pat

  #50  
Old February 19th 06, 01:01 AM posted to sci.space.moderated,sci.space.policy
external usenet poster
 
Posts: n/a
Default Moral Equivalent Of A Space Program

"Will McLean" wrote in
ups.com:

The CEV/CLV *could* do assembly, delivering modules instead of the
unpressurized cargo module. They've chosen not to do that, choosing
not to modify modules designed to launch on the shuttle. But there's
nothing impossible about it.


They'd have to modify the CLV as well; some of the modules will be beyond
its lift capacity once the propulsion, guidance, and ISS docking/berthing
systems are added in.

Like you said, not fundamentally impossible, but costly in terms of both
money and time.


--
JRF

Reply-to address spam-proofed - to reply by E-mail,
check "Organization" (I am not assimilated) and
think one step ahead of IBM.

 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Congressional Resolutions on Hubble Space Telescope EFLASPO Amateur Astronomy 0 April 1st 04 03:26 PM
Unofficial Space Shuttle Launch Guide Steven S. Pietrobon Space Shuttle 0 February 2nd 04 04:33 AM
First Moonwalk? A Russian Perspective Jason Donahue Amateur Astronomy 3 February 1st 04 04:33 AM
First Moonwalk? A Russian Perspective Astronaut Misc 0 January 31st 04 04:11 AM
NASA Selects International Space Station Program Scientis Ron Baalke Science 0 August 20th 03 06:38 AM


All times are GMT +1. The time now is 02:09 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 SpaceBanter.com.
The comments are property of their posters.