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  #42  
Old December 31st 04, 01:29 AM
Mary Pegg
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Pat Flannery wrote:

Back in the early days of jet engines, thought was given to simply
clustering large numbers of small jet engines to power aircraft; but
after the eight-engined B-52, the trend in both military and civilian
aircraft has been to _minamize_ the number of motors needed for
propulsion. Two is about the maximum you are going to see in future
fighters and small and medium airliners, four in bombers and large
airliners. I think there is a lesson there in regards to numbers vs.
reliability.


There's a lesson, but it's a lesson in economics. It's cheaper to
have two than four. On the other hand, a 747 with two engines out
will get there, a 777 with two engines out is a glider. Hence the
ETOPS (Extended Twin OPerationS) regulations which apply to both
the aircraft type *and* the operator.

--
Nothing to be done.

  #43  
Old January 1st 05, 01:26 PM
Rodney Kelp
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A 777 with two engines out is more like a rock than a glider.

"Mary Pegg" wrote in message
news
Pat Flannery wrote:

Back in the early days of jet engines, thought was given to simply
clustering large numbers of small jet engines to power aircraft; but
after the eight-engined B-52, the trend in both military and civilian
aircraft has been to _minamize_ the number of motors needed for
propulsion. Two is about the maximum you are going to see in future
fighters and small and medium airliners, four in bombers and large
airliners. I think there is a lesson there in regards to numbers vs.
reliability.


There's a lesson, but it's a lesson in economics. It's cheaper to
have two than four. On the other hand, a 747 with two engines out
will get there, a 777 with two engines out is a glider. Hence the
ETOPS (Extended Twin OPerationS) regulations which apply to both
the aircraft type *and* the operator.

--
Nothing to be done.


  #44  
Old January 2nd 05, 04:47 PM
T
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Pat Flannery wrote:
Henry Spencer wrote:


snip


(Well, and there would have been the small matter of his favored assembly
orbit -- the "two-hour orbit" -- being right in the middle of the inner
Van Allen belt...)


You mean the _von Braun_ belts in this scenario; the lack of experience
with solar storms would also be a problem.

Pat


Has the experience of the Fantastic Four taught us NOTHING?


TBerk

  #45  
Old January 2nd 05, 05:02 PM
Paul F. Dietz
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T wrote:

Has the experience of the Fantastic Four taught us NOTHING?


Marvel has reimagined them (and their other characters) in several
parallel lines of comics these days (they even have an Indian version
of Spiderman). Not all versions of the F4 were due to radiation.

Rather clever of Marvel, if you ask me, but then the comic
book business *is* a business.

Paul

  #46  
Old January 3rd 05, 02:52 AM
Henry Spencer
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In article ,
Keith F. Lynch wrote:
Mind you, the crash-program timing I noted above is unfortunate, in
that it may put your first lunar expeditions during the nasty solar
maximum of the late 50s.


Wasn't the 1972 maximum, which was in the middle of the Apollo
program, even larger? I remember marveling at the August 1972
auroras.


The 4 August 1972 giant flare was a bad one, but there were several
late-50s flares that were probably worse -- there is some uncertainty
because our knowledge of them is mostly indirect inferences from ground
measurements. (And there were some giant flares in the 1940s which may
have been worse still, but the data is very sketchy.)

The Sun was generally very active in August 1972, but only that one flare
really pegged the meters.

Fortunately there didn't happen to be an Apollo aloft that
day. If there had been, how much radiation would they have gotten?


Depends somewhat on what they were doing at the time. The onset of a
giant flare fortunately typically lasts several hours, giving time for
emergency procedures (if outside, get back inside fast; if on the lunar
surface, get back to the better-shielded CSM fast; point the CSM generally
nose-down but tipped some toward the hatch side, to get the greatest
combined shielding from the Moon and the CSM's own mass).

If memory serves, the tentative evaluation was that the 4 Aug 1972 flare
would probably have made an Apollo crew sick but they'd have survived...
but the 23 Feb 1956 flare might have been another story.
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |

  #47  
Old January 3rd 05, 04:43 AM
Peter Stickney
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In article ,
"Rodney Kelp" writes:
A 777 with two engines out is more like a rock than a glider.


Actually, the no-power Lift/Drag ratio for a 777 is around 23-25:1.
About that of a medium performance sailplane. Sink rates and best
glide speeds tend to be a bit higher, but airliners are quite
respectable gliders.

"Mary Pegg" wrote in message
news
Pat Flannery wrote:

Back in the early days of jet engines, thought was given to simply
clustering large numbers of small jet engines to power aircraft; but
after the eight-engined B-52, the trend in both military and civilian
aircraft has been to _minamize_ the number of motors needed for
propulsion. Two is about the maximum you are going to see in future
fighters and small and medium airliners, four in bombers and large
airliners. I think there is a lesson there in regards to numbers vs.
reliability.


There's a lesson, but it's a lesson in economics. It's cheaper to
have two than four. On the other hand, a 747 with two engines out
will get there, a 777 with two engines out is a glider. Hence the
ETOPS (Extended Twin OPerationS) regulations which apply to both
the aircraft type *and* the operator.


Uhm, Mary, that's ETOPS (Engines Turn Or Pilots Swim)

--
Pete Stickney

Without data, all you have are opinions

  #48  
Old January 3rd 05, 08:03 AM
Pat Flannery
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T wrote:


Has the experience of the Fantastic Four taught us NOTHING?



Al Shepard: "Lets light this candle..."
Von Braun: "Feure on!" :-)

Pat

  #49  
Old January 3rd 05, 02:38 PM
Jeff Findley
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"Mary Pegg" wrote in message
news
There's a lesson, but it's a lesson in economics. It's cheaper to
have two than four. On the other hand, a 747 with two engines out
will get there, a 777 with two engines out is a glider. Hence the
ETOPS (Extended Twin OPerationS) regulations which apply to both
the aircraft type *and* the operator.


Compare a 747 with 1/2 its engines out to a 777 with 1/2 of its engines out.
For lots of fun, try a 747 with both of the left engines out and see how it
flies and lands.

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

  #50  
Old January 3rd 05, 05:03 PM
Neil Gerace
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"Pat Flannery" wrote in message
...
Back in the early days of jet engines, thought was given to simply
clustering large numbers of small jet engines to power aircraft


I think that's because not much thought was given to building large engines;
the small ones being built were quite unreliable enough.

 




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