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#480
by
jongoff
on 01 Mar, 2008 17:13
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Another interesting thought re: high-thrust sea-level expander cycle engines. They really seem to be some of the best fits with Aerojet's "Thrust Augmented Nozzle" concept that I've talked about occasionally. Basically, for liftoff you want a really high T/W (unless you're airlaunching, but even then a high T/W doesn't hurt), while once you're above the atmosphere you want a lot less thrust, but a lot more Isp. So you have an expander cycle (possibly with inducers and maybe even a split expander like you mentioned Gary), with say a 200-300% augmentation ratio. That means at takeoff, somewhere between 60-75% of your propellant is being injected at a much lower pressure (120 psi for TAN vs 600-1200psi for the main flow), which greatly reduces the required pump power per unit thrust (while actually giving a slight boost in sea level Isp compared to just trying to run a higher chamber pressure). For instance, if you've got 3 parts TAN for 1 part Core flow, and the pressures are 1200psi in the core and 120psi in the TAN, that engine only consumes 30% more pump power than the core alone, in spite of producing 4x the thrust.
At least theoretically I don't see why this couldn't allow expanders bigger than the F-1 running at reasonably low chamber pressures. Unless I'm missing something (which is very possible--all of my real-world experience is with deep-throttleable pressure-fed LOX/alcohol engines).
~Jon
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#481
by
William Barton
on 24 Mar, 2008 10:13
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There was a brief discussion in another thread about getting to the ISS inclination by launching southeastwards, with the general consenus that the problem is overflights of populated territory in the Caribbean and eastern South America. I wonder: Since Wallops Island is about 5 degrees east of Cape Canaveral, would a southeasterly azimuth work from there?
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#482
by
edkyle99
on 24 Mar, 2008 14:26
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William Barton - 24/3/2008 6:13 AM
There was a brief discussion in another thread about getting to the ISS inclination by launching southeastwards, with the general consenus that the problem is overflights of populated territory in the Caribbean and eastern South America. I wonder: Since Wallops Island is about 5 degrees east of Cape Canaveral, would a southeasterly azimuth work from there?
Yes, at least according to:
http://www.marsspaceport.com/space_access.htm - Ed Kyle
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#483
by
Chris Bergin
on 19 Oct, 2008 14:05
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Today is a Pegasus day, so bump
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#484
by
ikke666
on 23 Dec, 2008 11:13
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Why hasn't used orbital an derivative of the x-34 as a reusable first stage for their 3 stage pegasus?
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#485
by
Jim
on 23 Dec, 2008 11:55
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Why hasn't used orbital an derivative of the x-34 as a reusable first stage for their 3 stage pegasus?
Because it isn't needed, the aircraft (L-1011) is much cheaper. And the next cheaper option is the solid first stage, which combined with Pegasus is Taurus
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#486
by
ikke666
on 23 Dec, 2008 15:18
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I didn't mean the alternative stage would replace the aircraft.
I thought it was more cost effective to replace the first winged solid rocket stage with one who could be reused.
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#487
by
Jim
on 23 Dec, 2008 15:42
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I didn't mean the alternative stage would replace the aircraft.
I thought it was more cost effective to replace the first winged solid rocket stage with one who could be reused.
Pegasus doesn't fly enough to warrant a change in the first stage
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#488
by
tnphysics
on 04 Jan, 2009 22:14
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If it turns out that the F9 is profitably reusable, then would that be a reason to try to reuse the Taurus 2 Stage 1?
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#489
by
jcm
on 04 Mar, 2011 13:55
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Antonio - I am sure many of us have the Orbital team in our thoughts on this tough day. Best wishes to all and good luck on the investigation.
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#490
by
baldusi
on 24 Jun, 2011 02:39
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Dr Elias, in other thread there was some speculation regarding using the Taurus II as a booster. Was there some provision made in the design to be used as such?
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#491
by
Robotbeat
on 24 Jun, 2011 02:48
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Along those lines... Any thought going towards upgrading Taurus II with the proposed domesticized NK-33 (with reportedly significantly greater thrust) that Aerojet just announced?
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#492
by
Galactic Penguin SST
on 13 Dec, 2011 08:42
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I wonder if the new name for Taurus II came from this very thread....
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#493
by
Seer
on 17 Mar, 2012 20:11
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So, will we see any electric propulsion satellites from Orbital, Antonio?
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#494
by
kevin-rf
on 18 Mar, 2012 01:32
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So, will we see any electric propulsion satellites from Orbital, Antonio?
Since Orbital is a publicly traded company I doubt he would reveal anything so much as a millisecond before Orbital officially announced something. A millisecond later, well NSF would have more threads then you can shake a rocket at.
Though, when you look at the latest aviation week article on the subject, both Loral and Astrium have said they are working on something and will announce something in the near future. That does put pressure on Orbital to announce something. Otherwise it gives the competition something to one up Orbital with. The new 702SP does look to be aimed squarely at Orbital's niche.
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#495
by
Seer
on 18 Mar, 2012 06:06
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Electric satellites of the 702sp mass would also be able to be launched on Antares.
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#496
by
jcm
on 23 Jun, 2012 00:38
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If Antonio's still reading this thread: I realize I always misunderstood the nature of the APEX (Aug 1994) and SEASTAR (Aug 1997) Pegasus launches - the press at the time made it sound like the third stage was part of the Pegastar spacecraft, but now I realize it was just that (some of?) the third stage
avionics functions were moved to the spacecraft bus (or something?) but the third stage still separated as usual.
Can you comment on what was different about the third stage for these missions, and whether there was or was not an advantage to doing whatever was done?
- Jonathan
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#497
by
antonioe
on 25 Jun, 2012 16:22
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If Antonio's still reading this thread: I realize I always misunderstood the nature of the APEX (Aug 1994) and SEASTAR (Aug 1997) Pegasus launches - the press at the time made it sound like the third stage was part of the Pegastar spacecraft, but now I realize it was just that (some of?) the third stage
avionics functions were moved to the spacecraft bus (or something?) but the third stage still separated as usual.
Can you comment on what was different about the third stage for these missions, and whether there was or was not an advantage to doing whatever was done?
- Jonathan
APEX incorporated the Pegasus avionics as its own avionics, so the satellite steered the rocket intil it separated from the avionicsless third stage. That was not the case for SeaStar.
No, it was not a good idea. Trust me, it was MY idea!
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#498
by
jcm
on 29 Jun, 2012 22:14
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If Antonio's still reading this thread: I realize I always misunderstood the nature of the APEX (Aug 1994) and SEASTAR (Aug 1997) Pegasus launches - the press at the time made it sound like the third stage was part of the Pegastar spacecraft, but now I realize it was just that (some of?) the third stage
avionics functions were moved to the spacecraft bus (or something?) but the third stage still separated as usual.
Can you comment on what was different about the third stage for these missions, and whether there was or was not an advantage to doing whatever was done?
- Jonathan
APEX incorporated the Pegasus avionics as its own avionics, so the satellite steered the rocket intil it separated from the avionicsless third stage. That was not the case for SeaStar.
No, it was not a good idea. Trust me, it was MY idea!
Thanks for the insight!!
(As it happens, I spent much of today working around the results of an idea I had ten years ago that seemed like a really good one at the time :-))
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#499
by
gin455res
on 30 Jun, 2012 08:40
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Hi Antonio,
I read earlier in the thread that you inspected a B52 (one that carried the x15) before settling on the final launch aircraft.
This was hung off the wing and not underneath.
Do you know if the size of a rocket-plane suspended from a wing is limited by the asymmetry of this arrangement?
And if it is, do you know of any air launch concepts where the rocket plane is hung under one wing and a dead mass counter weight is slung under the opposite wing to balance this asymmetry?
(I'm assuming hanging two rocket-planes off the opposite wings of a carrier plane, and releasing them at the same time is madness?)
