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The 100/10/1 Rule.



 
 
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  #71  
Old March 10th 07, 03:16 PM posted to sci.space.history,sci.space.policy,sci.space.station,sci.space.shuttle
Pat Flannery
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Default The 100/10/1 Rule.



Henry Spencer wrote:


You might like it there, but other considerations can intervene, like the
extra structural weight incurred by putting most of the propellant mass up
high. The LOX was on the bottom in the S-II, the S-IV/S-IVB, and the
Ariane 1/2/3/4 third stage, and still is in the Centaur, the Delta IV
upper stage, and the GSLV third stage. It might have ended up on the
bottom in the ET, too, had it not been for the asymmetric vehicle
configuration -- keeping the ET's changing center of mass within the
limited gimbal range of the SSMEs absolutely dictated putting the LOX tank
as far away from the SSMEs as humanly possible.


I thought the gimbaling would probably be the main problem... the thing
is already fairly unstable without getting it completely unstable by
sticking the LH2 on top and having it constantly trying to go out of
control.
Was there any particular reason the LOX ended up on top in the Atlas?
Gimbaling limits again?
I note that both Jupiter and Thor had it on the bottom.

Pat
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  #72  
Old March 10th 07, 03:46 PM posted to sci.space.history,sci.space.policy,sci.space.station,sci.space.shuttle
Pat Flannery
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Posts: 18,466
Default The 100/10/1 Rule.



Mr Jim wrote:
Does Project Score count? That was a specially-prepared Atlas B launched in
December of 1958 which put the booster (less the so-called stage zero
booster engines, of course) in orbit, with a radio transmitter/tape player
package that broadcast a recorded "message of peace" from President
Eisenhower. "Atlas - the ultimate weapon" has a chapter on it, with excerpts
from a BIPS article ("the talking satellite") about the mission.

The fact that it dropped the two outer engines probably disqualifies it
from the SSTO category.
With the later Atlas versions it might have been possible to get the
whole works in orbit, but with no real payload, so there was no reason
to do it.
I still remember Eisenhower's stirring Christmas message from orbit:
"This is the President of the United States speaking. Through the
marvels of scientific advance, my voice is coming to you from a
satellite traveling in outer space.
My message is a simple one: Through this unique means I convey to you
and all mankind, America's wish for peace on Earth and goodwill toward
men everywhere."
Only recently has the alternative version of the message come to light
in the voluminous archives of the Eisenhower presidential library:
"This is the Vice President of the United States speaking. Through the
marvels of scientific advance, my voice is coming to you from a
satellite traveling in outer space, launched by a rocket that could put
a hydrogen bomb in Red Square inside of one hour from the word "go".
My message is a simple one: Through this unique means I convey to you
and all mankind, America's wish for peace on Earth and goodwill toward
men everywhere.
Or else.
And that goes for you big eastern college-boy beatnik liberals also. No
good will for you, you pinkos.
The only peace you deserve is eternal peace. If Checkers ever laid eyes
on you, he'd bite you right on your big red ass." ;-)

Pat
  #73  
Old March 10th 07, 03:52 PM posted to sci.space.history,sci.space.policy,sci.space.station,sci.space.shuttle
Pat Flannery
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Default The 100/10/1 Rule.



Henry Spencer wrote:
Not necessarily. The lower Isp is more than made up for by the higher
propellant density and the better engine T/W ratio. Sure, you need a
higher mass ratio, but it's actually easier to do. Dense-propellant
stages with SSTO-class performance were built years before LOX/LH2 ones
started to show up, and with considerably less difficulty.

Also note that the mass-ratio disparity is not as large as you'd think,
because a dense-propellant SSTO needs less delta-V to reach orbit. Lower
Isp, and thus higher propellant mass-flow rate, means it loses mass
faster, thus reaches higher accelerations sooner, thus suffers smaller
gravity losses. It's not a big advantage -- circa 300m/s -- but it's on
the steep part of the curve, so it drops the required mass ratio quite
substantially. (This effect was known in the early 60s, but got forgotten
in the rush of enthusiasm for hydrogen the wonder fuel.)


Okay.
(crawls back under rock)
We've read up on your "Brown Bess" booster concept; if you were going to
make an unmanned expendable SSTO, how would you go about it, and what
propellant combo would you use?

Pat
  #74  
Old March 10th 07, 03:55 PM posted to sci.space.history,sci.space.policy,sci.space.station,sci.space.shuttle
Herb Schaltegger
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Default The 100/10/1 Rule.

On Sat, 10 Mar 2007 00:54:39 -0600, Henry Spencer wrote
(in article ):

Also note that the mass-ratio disparity is not as large as you'd think,
because a dense-propellant SSTO needs less delta-V to reach orbit.


Um, what?

--
You can run on for a long time,
Sooner or later, God'll cut you down.
~Johnny Cash

  #75  
Old March 10th 07, 04:01 PM posted to sci.space.history,sci.space.policy,sci.space.station,sci.space.shuttle
Paul F. Dietz
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Posts: 599
Default The 100/10/1 Rule.

Herb Schaltegger wrote:
On Sat, 10 Mar 2007 00:54:39 -0600, Henry Spencer wrote
(in article ):


Also note that the mass-ratio disparity is not as large as you'd think,
because a dense-propellant SSTO needs less delta-V to reach orbit.



Um, what?


He explained that. What part of the explanation didn't you understand?

Paul
  #76  
Old March 10th 07, 05:16 PM posted to sci.space.history,sci.space.policy,sci.space.station,sci.space.shuttle
kT
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Posts: 5,032
Default The 100/10/1 Rule.

Henry Spencer wrote:

In article ,
Pat Flannery wrote:
LOX is on top on the ET also.
Due to it's higher mass than LH2 per volume, the LOX will end up on top
in pretty much any design you use, for balance purposes during ascent.
You want the CG as far forward as possible.


You might like it there, but other considerations can intervene, like the
extra structural weight incurred by putting most of the propellant mass up
high. The LOX was on the bottom in the S-II, the S-IV/S-IVB, and the
Ariane 1/2/3/4 third stage, and still is in the Centaur, the Delta IV
upper stage, and the GSLV third stage. It might have ended up on the
bottom in the ET, too, had it not been for the asymmetric vehicle
configuration -- keeping the ET's changing center of mass within the
limited gimbal range of the SSMEs absolutely dictated putting the LOX tank
as far away from the SSMEs as humanly possible.


That brings up another little paper napkin design that has been floating
around : two four segment SRBs on a Delta IV Medium CBC, attached from
the thrust structure to the intertank segment, with an SSME for primary
propulsion. This would be the 'little Ariane V' design. Any comments?

At least the oxygen is still on the top. I can see I'm going to have to
write some extra simulation code. Thanks guys, the discussions here
lately have been improving, across the board. I just haven't been
following up on many of these frankensteins, as I am focused on SSTO.

--
Get A Free Orbiter Space Flight Simulator :
http://orbit.medphys.ucl.ac.uk/orbit.html
  #77  
Old March 10th 07, 05:51 PM posted to sci.space.history,sci.space.policy,sci.space.station,sci.space.shuttle
Pat Flannery
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Posts: 18,466
Default The 100/10/1 Rule.



kT wrote:

That brings up another little paper napkin design that has been
floating around : two four segment SRBs on a Delta IV Medium CBC,
attached from the thrust structure to the intertank segment, with an
SSME for primary propulsion. This would be the 'little Ariane V'
design. Any comments?


Yeah, us a RS-68 as its cheaper than a SSME.

Pat
  #78  
Old March 10th 07, 06:01 PM posted to sci.space.history,sci.space.policy,sci.space.station,sci.space.shuttle
kT
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Posts: 5,032
Default The 100/10/1 Rule.

Pat Flannery wrote:

kT wrote:

That brings up another little paper napkin design that has been
floating around : two four segment SRBs on a Delta IV Medium CBC,
attached from the thrust structure to the intertank segment, with an
SSME for primary propulsion. This would be the 'little Ariane V'
design. Any comments?


Yeah, us a RS-68 as its cheaper than a SSME.


Except for the fact that it can't make orbit on its own.

If you want to fly the RS-68, may I suggest the Delta IV?

--
Get A Free Orbiter Space Flight Simulator :
http://orbit.medphys.ucl.ac.uk/orbit.html
  #79  
Old March 10th 07, 06:14 PM posted to sci.space.history,sci.space.policy,sci.space.station,sci.space.shuttle
richard schumacher
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Posts: 191
Default The 100/10/1 Rule.

In article ,
Pat Flannery wrote:

We've read up on your "Brown Bess" booster concept; if you were going to
make an unmanned expendable SSTO, how would you go about it, and what
propellant combo would you use?


He will start by dropping the pointless qualifier "unmanned".
  #80  
Old March 10th 07, 09:47 PM posted to sci.space.history,sci.space.policy,sci.space.station,sci.space.shuttle
Jorge R. Frank
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Posts: 2,089
Default The 100/10/1 Rule.

"Paul F. Dietz" wrote in
:

Herb Schaltegger wrote:
On Sat, 10 Mar 2007 00:54:39 -0600, Henry Spencer wrote
(in article ):

Also note that the mass-ratio disparity is not as large as you'd think,
because a dense-propellant SSTO needs less delta-V to reach orbit.


Um, what?


He explained that. What part of the explanation didn't you understand?


He kinda sorta explained that. The actual delta-V required to reach orbit
is purely a function of orbital mechanics and is independent of propellant
density. But the rocket equation does not account for things like gravity
and drag losses, and those things do depend on propellant density. Rather
than expand the rocket equation to explicitly include those terms, the
convention is to apply a fudge factor to the delta-V term. Dense-propellant
SSTOs have lower gravity losses so they need a smaller fudge factor. (They
also typically have lower drag losses since the dense propellants allow
smaller tanks, but that's not as significant as the lower gravity losses.)

So a dense-propellant SSTO doesn't really need less delta-V to reach orbit,
but you use a smaller delta-V term when modelling one using the rocket
equation.

--
JRF

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