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$64 Billion and seventeen years to land on the moon. What's wrong with this picture?



 
 
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  #291  
Old May 8th 04, 03:36 AM
Neil Gerace
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"Henry Spencer" wrote in message
...
(NB, there is disagreement about whether four chambers with one pump set
is considered one engine or four.)


My old car has four combustion chambers and one fuel pump. Definitely only
one engine


  #292  
Old May 8th 04, 05:27 AM
Henry Spencer
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In article ,
Derek Lyons wrote:
But the baffles are in a very harsh
environment, and they probably have to be cooled, e.g. by feeding a bit of
fuel (and only fuel) out through holes in them...


Why only fuel?


For effective cooling, you want to avoid combustion near the baffle
surfaces. (This is why it's better to feed the fuel out than to just
circulate it through them -- the fuel vapor fends the hot gas off from the
surface, greatly increasing the effective cooling value.) So you want
to use only one of the two propellants, at least in a given region.

As for why you might choose fuel rather than oxidizer... several reasons.
One obvious one is that the safe service temperature of typical baffle
materials is higher in a non-oxidizing environment.

More subtly, in traditional engine designs running at relatively low
pressures, LOX is not a good coolant, because it boils too quickly -- its
liquid range is fairly narrow, and gas is not *nearly* as good a coolant
as liquid. (Even if you are about to feed it out into the chamber, you
want it to cool the baffle material first.) This ceases to be important
when pressures go beyond the critical pressure of LOX -- 730 psi -- and
the liquid range effectively becomes unlimited.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |
  #293  
Old May 8th 04, 09:58 PM
Pat Flannery
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Neil Gerace wrote:

"Henry Spencer" wrote in message
...


(NB, there is disagreement about whether four chambers with one pump set
is considered one engine or four.)



My old car has four combustion chambers and one fuel pump. Definitely only
one engine


I tried the same argument with Henry years ago; it didn't work....
I look at it this way; if the company that makes the motor considers it
to be a single motor, then that's good enough for me.

Pat

  #294  
Old May 8th 04, 11:51 PM
Dan DeLong
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(Henry Spencer) wrote in message ...
In article ,
John Stoffel wrote:
Whereas XCOR has recently switched from isopropanol to kerosene...


How different is the burn characteristics between the two fuels? Will
this require a new injector design, or can they just fudge it all a
bit and treat the two fuels as mostly similiar in handling and burning
properties?


I don't know the details of what they're doing. My guess would be that
you could fudge it for igniters and small engines, especially without
regenerative cooling, but for main engines you'd want to pick the fuel
early in design. There *were* successful alcohol-to-kerosene conversions
of existing engines, without too much modification, in the 1950s, but it
strikes me as iffy. (In particular, those were quite low-pressure engines
by modern standards.)


What we're doing can't be called a "conversion", Henry. It's a new
design from clean paper. The XR-4K5 kerosene engine has 4 times the
thrust and over twice the chamber pressure of the XR-4A3 alcohol
engine. The concepts are the same but most of the dimensions are
different for both the injector and cooling. That is, the same
injector style, but adjusted flow areas and patterns for the different
O/F and density. There are as many changes to the cooling features as
in the injector. Kerosene has inferior cooling properties to
isopropanol. Can't go into further details for two reasons. One, it's
proprietary and two, this is an international forum and we have to be
sensitive to ITAR issues.

There are reasons other than cost and specific impulse that influenced
the propellant change decision. In-flight restartability was always a
requirement and that was easier to develop with alcohol. Now that we
figured out how to do it, we have more confidence about doing it with
kerosene. Another reason is that some of our potential applications
are for government customers and they prefer kerosene. And finally,
there is the intangible reason of not having to repeatedly answer the
questions "Why are you using alcohol? Isn't that 1950s technology?"
and "Where's the plume?"

Dan DeLong
  #295  
Old May 9th 04, 01:15 AM
Henry Spencer
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In article ,
Dan DeLong wrote:
...There *were* successful alcohol-to-kerosene conversions
of existing engines, without too much modification, in the 1950s, but it
strikes me as iffy...


What we're doing can't be called a "conversion", Henry. It's a new
design from clean paper.


Yeah, that's what I expected -- both because it's a bigger engine anyway,
and because too many of the details have to change.

(I'm amazed that some of those 1950s conversions actually worked. In
addition to the alcohol-to-kerosene conversions, there was at least one
experimental dense-fuels-to-hydrogen conversion!)

...this is an international forum and we have to be
sensitive to ITAR issues.


True, alas. The US has come a long way from "Congress shall make no
law... abridging the freedom of speech, or of the press...".

there is the intangible reason of not having to repeatedly answer the
questions "Why are you using alcohol? Isn't that 1950s technology?"
and "Where's the plume?"


Yes, I can imagine that it would get tedious answering those questions for
the hundredth time...
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |
  #296  
Old May 12th 04, 06:08 PM
Scott Hedrick
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"Herb Schaltegger" wrote in message
...
*I think Henry thinks too much for any one human. Either: a) he's
really 73 different people all posting using the same account; b) he's
one man who uses time-warp technology to learn as much as 73 people all
at the same time; c) he's another of Pat's atom-brained zombies, but
just a really, really smart one! ;-)


Multiple brains tied together- an organic multiple processor.


  #297  
Old May 12th 04, 07:33 PM
OM
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On Wed, 12 May 2004 13:08:00 -0400, "Scott Hedrick"
wrote:


"Herb Schaltegger" wrote in message
...
*I think Henry thinks too much for any one human. Either: a) he's
really 73 different people all posting using the same account; b) he's
one man who uses time-warp technology to learn as much as 73 people all
at the same time; c) he's another of Pat's atom-brained zombies, but
just a really, really smart one! ;-)


Multiple brains tied together- an organic multiple processor.


....I'm getting freudian dyslexic in my old age. The first time I read
that, i thought Scott said "multiple orgasmic processor".

OM

--

"No ******* ever won a war by dying for | http://www.io.com/~o_m
his country. He won it by making the other | Sergeant-At-Arms
poor dumb ******* die for his country." | Human O-Ring Society

- General George S. Patton, Jr
  #298  
Old May 12th 04, 10:03 PM
Scott Hedrick
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"OM" om@our_blessed_lady_mary_of_the_holy_NASA_researc h_facility.org wrote
in message ...
The first time I read
that, i thought Scott said "multiple orgasmic processor".


Mrs Henry- is that you?


  #299  
Old May 13th 04, 04:08 AM
Greg D. Moore \(Strider\)
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"OM" om@our_blessed_lady_mary_of_the_holy_NASA_researc h_facility.org wrote
in message ...

...I'm getting freudian dyslexic in my old age. The first time I read
that, i thought Scott said "multiple orgasmic processor".


Didn't Jane break the orgasmatron?


OM

--

"No ******* ever won a war by dying for | http://www.io.com/~o_m
his country. He won it by making the other | Sergeant-At-Arms
poor dumb ******* die for his country." | Human O-Ring Society

- General George S. Patton, Jr



 




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