Modern Sci-Fi - the enslavement of scientific reality to religious delusion

"Gene Ward Smith" wrote in
oups.com:


Terry Austin wrote:

Typical believer mark. Can't refute what he has said, so you call names.

Yes, that's what Randi did--call names. That you are a true believer
has also become clear.

And yet, you're the one afraid to quote your own words in your replies.

Why is that, coward?

--
Terry Austin

Terry Austin wrote:
"Gene Ward Smith" wrote in
oups.com:

Yes, that's what Randi did--call names. That you are a true believer
has also become clear.

And yet, you're the one afraid to quote your own words in your replies.

Why is that, coward?

Because I trim, Stupid. It's recommended Usenet practice.

Why do you fly into a spittle-spewing rage because someone says they
are not impressed by Randi? That makes about as much sense as
firebombing a church to prove Moslems are nonviolent.

"Gene Ward Smith" wrote in
oups.com:


Terry Austin wrote:
"Gene Ward Smith" wrote in
oups.com:

Yes, that's what Randi did--call names. That you are a true believer
has also become clear.

And yet, you're the one afraid to quote your own words in your replies.

Why is that, coward?

Because I trim, Stupid. It's recommended Usenet practice.

Especially when the quote proves you a liar.

But thanks for admitting I'm right.

--
Terry Austin

Wayne Throop wrote:

The alternatives are "have lots of energy, use a small
fraction", and "have very little energy, use a large fraction".
Why is it important to avoid the former and do the latter?

Firstly, those aren't the all the alternatives. There is the "have
lots of energy, use a large fraction" option (gaseous fission for
example).

Secondly, the ones that have "lots of energy" are extremely
expensive compared to the ones that "have very little energy".

For example, with current technology, a stirling engine can be
made much more efficient than an internal combustion engine, in
terms of fuel converted to useful work. And run quieter, and
last longer, too. But if the task you require of it is to run a
helicopter, it is traditional to use the less efficient, but
higher power-per-mass method. I approve of this tradition.
Especially if I were contemplating a trip by helicopter.

Not a good analogy. Internal combustion engines and Stirling
engines are relative close in efficiency (well within a factor of
2). Therefore the choice between them can be dominated by other
considerations (such as power to weight ratio).

Orions have thermal efficiencies about 3 or 4 *orders of magnitude*
less than chemical rockets.

Do you imagine IC engines would be used for any application if its
efficiency was 3 or 4 orders of magnitude less than that of
Stirling engines?

: For nuclear rockets of whatever description (including Orion)
: where reaction mass and energy source are *not* the same the
: importance of delta-v-per- reaction-mass is much diminished.

Why? You still haven't explained the "why".

Yes I did. I'll repeat it since you didn't grasp it:

The ratio of useful work done to available energy expended (the
usual measure of efficiency) is very low for Orion and this is
unfortunately coupled with the fact that the energy source for
Orion (fissile material) is very expensive. Even the smallest
practical Orion consumed enormous quantities of fissile material.

Jim Davis

: Jim Davis
: Firstly, those aren't the all the alternatives. There is the "have
: lots of energy, use a large fraction" option (gaseous fission for
: example).

They are, however, the alternatives that were under discussion.
Your claim was that it is, for some reason you haven't shared,
more impotant to be in the one category than the other. If that
wasn't your claim, what high-thrust, near-future technologies
do you have in mind, exactly?

: Secondly, the ones that have "lots of energy" are extremely expensive
: compared to the ones that "have very little energy".

Near as I can tell, that turns out not to be the case.
Why would nuclear pulse propulsion be more expensive in terms of delta-v
per given mass? Indeed the reverse seems to be the case; chemical
rockets and their infrastructure would be many times as expensive, to
deliver a given payload to, say mars. Such as an exploratory
expedition. Do you have references to the costs you are concerned with?
How many dollars per ton are we talking, exactly?

: Not a good analogy.

Shrug. It illustrates the folly of an inappropriate definition
of "efficiency". And you still haven't explained why delta-v per
reacion mass is the wrong one (though see below).

: Do you imagine IC engines would be used for any application if its
: efficiency was 3 or 4 orders of magnitude less than that of Stirling
: engines?

If you really really wanted to fly a helecopter, yes.
But more to the point, recall that the comparison is to chemical fuels,
which are six orders of magnitude less energy per fuel mass. So, four
orders of magnitude less energy-efficient, times six orders of magnitude
more energy, still yields a hundred times more efective.

: The ratio of useful work done to available energy expended (the usual
: measure of efficiency) is very low for Orion and this is unfortunately
: coupled with the fact that the energy source for Orion (fissile
: material) is very expensive.

Which still doesn't explain it, since you've pretty much merely
substituted dollars for reaction mass, but haven't said why the million
times more mass per unit energy is cheaper. Again, how many dollars
per ton of payload are we talking, exactly? Or even approximately.


Wayne Throop http://sheol.org/throopw

On Sun, 17 Sep 2006 20:45:58 GMT, in a place far, far away,
(Wayne Throop) made the phosphor on my monitor glow
in such a way as to indicate that:

Near as I can tell, that turns out not to be the case.
Why would nuclear pulse propulsion be more expensive in terms of delta-v
per given mass? Indeed the reverse seems to be the case; chemical
rockets and their infrastructure would be many times as expensive, to
deliver a given payload to, say mars. Such as an exploratory
expedition. Do you have references to the costs you are concerned with?
How many dollars per ton are we talking, exactly?

: Not a good analogy.

Shrug. It illustrates the folly of an inappropriate definition
of "efficiency". And you still haven't explained why delta-v per
reacion mass is the wrong one (though see below).

Which one is the "right" one depends on what one is trying to
optimize. There is no obvious correct answer. Unfortunately, one of
the reasons that launch is so expensive is that engineers focus on
technical measures of efficiency (e.g., the Isp of the SSME) instead
of on cost efficiency.

:: It illustrates the folly of an inappropriate definition of "efficiency".

: h (Rand Simberg)
: Which one is the "right" one depends on what one is trying to
: optimize. There is no obvious correct answer. Unfortunately, one of
: the reasons that launch is so expensive is that engineers focus on
: technical measures of efficiency (e.g., the Isp of the SSME) instead
: of on cost efficiency.

Yes, dollars in per similar goal out is almost always the right one.
I don't see that nuclear pulse propulsion is markedly worse than
alternatives. It is politicaly unacceptable, and a PR nightmare
in the current social climate, and arguably has unacceptable
environmental impact in some uses, and that's part of the "almost always".
But I don't see those as "efficiency" issues in this case.


Wayne Throop http://sheol.org/throopw

On Sun, 17 Sep 2006 21:17:08 GMT, in a place far, far away,
(Wayne Throop) made the phosphor on my monitor glow
in such a way as to indicate that:

:: It illustrates the folly of an inappropriate definition of "efficiency".

: h (Rand Simberg)
: Which one is the "right" one depends on what one is trying to
: optimize. There is no obvious correct answer. Unfortunately, one of
: the reasons that launch is so expensive is that engineers focus on
: technical measures of efficiency (e.g., the Isp of the SSME) instead
: of on cost efficiency.

Yes, dollars in per similar goal out is almost always the right one.
I don't see that nuclear pulse propulsion is markedly worse than
alternatives. It is politicaly unacceptable, and a PR nightmare
in the current social climate, and arguably has unacceptable
environmental impact in some uses, and that's part of the "almost always".
But I don't see those as "efficiency" issues in this case.

And it's not at all obvious that Orion would have been low cost to
anywhere.

: h (Rand Simberg)
: And it's not at all obvious that Orion
: [.. the nuclear pulse propulsion one ..]
: would have been low cost to anywhere.

What do you see as the major expenses of, say, the proposed mars
expedition? Or of nuclear pulse propulsion systems in operation in general?

My guess would be, most of it would be largely reusable, and the major
expense of such a system in operation would be the pulse units. Though
mainenance cycle costs are unclear.

In any event, while I agree it's not obvious, it seems to me that
the upthread characterization of "not a serious proposal" is unjustified.
At least, I haven't seen anybody make a substantial case justifying it.


Wayne Throop http://sheol.org/throopw

Wayne Throop wrote:

In any event, while I agree it's not obvious, it seems to me that
the upthread characterization of "not a serious proposal" is unjustified.
At least, I haven't seen anybody make a substantial case justifying it.

And besides, the objections that had been raised so far in defense of
that claim weren't about cost effectiveness, they were about energy
efficiency.

--
Erik Max Francis && && http://www.alcyone.com/max/
San Jose, CA, USA && 37 20 N 121 53 W && AIM, Y!M erikmaxfrancis
You are in the music / In the man's car next to me
-- Sade