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#100
by
Jim
on 23 Sep, 2007 11:25
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tnphysics - 22/9/2007 10:38 PM
What about scrapping the tankage and focusing on reusing the engines?
Or making a flyback CBC?
Not worth the effort
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#101
by
tnphysics
on 24 Sep, 2007 22:34
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Would using RS-800 engines require pad mods?
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#102
by
Firehawk153
on 25 Sep, 2007 20:38
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If the need or financial justification arose, could the RS-68 be modified for use as an upperstage engine? Stock RS-68 ISP in a vacum (410) can't compete w/ RL-10 (as high as 462?) but I wonder if perhaps the Ares upgrades to the RS-68 would open up this possibility. Or would it be better to complete the AUS?
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#103
by
Jim
on 25 Sep, 2007 22:07
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Firehawk153 - 25/9/2007 4:38 PM
If the need or financial justification arose, could the RS-68 be modified for use as an upperstage engine? Stock RS-68 ISP in a vacum (410) can't compete w/ RL-10 (as high as 462?) but I wonder if perhaps the Ares upgrades to the RS-68 would open up this possibility. Or would it be better to complete the AUS?
RS-68 as an upperstage engine is a nogo. See other posts
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#104
by
MKremer
on 25 Sep, 2007 22:20
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Firehawk153 - 25/9/2007 3:38 PM
If the need or financial justification arose, could the RS-68 be modified for use as an upperstage engine? Stock RS-68 ISP in a vacum (410) can't compete w/ RL-10 (as high as 462?) but I wonder if perhaps the Ares upgrades to the RS-68 would open up this possibility. Or would it be better to complete the AUS?
As mentioned by others here in different threads, the RS-68 design just takes too much ground support equipment to prep for ignition and through the ignition cycle. To try to add all it needs into an upper stage would add so much mass it would overwhelm any advantages the engine could offer.
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#105
by
tnphysics
on 25 Sep, 2007 22:48
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Jetteson the excess startup hardware after RS-68 ignition.
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#106
by
Firehawk153
on 25 Sep, 2007 23:05
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Ahhhh, okay, it makes sense then why it wouldn't work. I forget that these vehicles require extensive ground support.
tnphysics - 25/9/2007 5:48 PM
Jetteson the excess startup hardware after RS-68 ignition.
Wouldn't this incur a mass penalty to the overall payload capacity to haul the excess equipment thru 1st stage and 2nd stage ignition?
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#107
by
MKremer
on 25 Sep, 2007 23:11
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You're kidding, right?
I'm not sure it couldn't be done, but do you realize the amount of extra engineering, testing, and costs involved to try to accomplish that?
Just some advice, but you really need to keep in mind that everything requires money - $$$$$. Designs cost $$$$$. Engineering costs $$$$$. Development and testing costs $$$$$. Construction costs $$$$$. Money ($$$$$) rules over everything, *everything* regardless of how neat, nifty, cool, or even practical a new idea for a booster, propulsion system, mission vehicle, or mission plan design might be.
The primary emphasis is to design and build the hardware needed to accomplish the ordered mission for as little $$$$$ as possible. The $$$$$$ is the main priority for the designs and hardware, not the hardware or mission itself.
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#108
by
Nick L.
on 25 Sep, 2007 23:32
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tnphysics - 25/9/2007 6:48 PM
Jetteson the excess startup hardware after RS-68 ignition.
The LV might not even be able to get off the ground! The hardware is MUCH bigger than you think. I would bet that carrying all of the starting equipment would reduce payload to nil, if you could even get it to fit into the LV interstage. From an old post of Jim's, I believe the helium tank for starting the engine is the size of a tractor-trailer. Engineering the ability to carry all of this equipment into the rocket, and then jettisoning all of it, would cost very much - almost certainly too much to be worth it.
The RS-68 is also not capable of air-starting, due to the differences in air pressure and density, and re-engineering it to be able to do that basically kills the cost benefits of the cheaper RS-68 design.
All in all, too much money for too little reward.
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#109
by
tnphysics
on 26 Sep, 2007 01:40
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What about using Atlas V CCBs as LRBs on a Heavy?
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#110
by
MKremer
on 26 Sep, 2007 01:43
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First fund the heavy testing and development.
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#111
by
TrueGrit
on 26 Sep, 2007 16:06
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"What about using Atlas V CCBs as LRBs on a Heavy?"
Delta Heavy with the RS-68A exceeds Atlas Heavy capability... Atlas and Delta attachment points points don't match up... Altas and Delta avionics systems are not compatible... LC37/SLC6 don't have the proper GSE (umbicals to electrical) to support Atlas... LC37/SLC6 don't have any RP1 loading capability... LC37/SLC6 LOx storage capability sized to Delta and Atlas requires more... And the problems go on and on
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#112
by
TrueGrit
on 26 Sep, 2007 16:14
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RS-68 as an upperstage engine? First question is what upper-stage would require ~800klb of thrust? Second what upperstage would want the huge mass penalty (RS-68 is quite heavy)? RS-68 would drain the huge Ares upperstage dry in less than 3 minutes... And pull almost 2 g's at the time.
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#113
by
Propforce
on 26 Sep, 2007 17:58
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I am amused with all these seemly naive questions. But I think the problem is that the folks who are not in this industry doesn't know how a launch vehicle and engine is designed. As such, in their minds, they're trying to fit an existing engine into a "new" vehicle for whatever application they have in mind.
In reality, those of us who are in this business will design or modify an existing engine/ vehicle to meet whatever the new mission(s) calls for, assuming there's a "need" for this new mission and whoever the customer is will pay for it. Sometime we change the design so much just about the only "heritage" part is the nameplate and everything else is different. We, D-IV, do it. The Atlas folks do it. The SpaceX folks do it. Everyone who's in the LV business does it.
We will start with these "new" missions, develop representative flight profiles, call them "design reference missioins" (DRM) and start to evaluate existing vehicle/ engine to see if we can modify or need to build new ones, and how long and how much they will cost. All these study results are fed back to management/ customers in order to evaluate if the mission is worth the money that will be required.
Like Dr. Antonio Elias of OSC said, any fools can design an expensive new launch vehicle, but it takes experiences and brains to design a "cost effective" vehicle. The ingenius part is to design a vehicle that is inexpensive while meeting launch accuracy and relaibility. In the case of "mature" infrastructure such as the Atlas and the Delta, any decision on design changes on the vehicle must take into account its impact on existing launch pad, ground system, factory, suppy chain, and logistic. Sometime it's harder to make changes to these infrastructure and it's easier if one is starting from scratch such as the SpaceX and OSC.
In the case of Delta IV upgrades, yes we have studied putting a brand new engine (MB-60) on a new "stretch" versioin of upper stage (AUS), or putting 2~3 smaller new engines (MB-35), or existing engines (RL10B-2), more solids on the CBC, more liquid strap-on (upto 6) around the core CBC, build a larger diameter of CBC (over 8 meters) and put multiple RS-68s on each CBC, up-rating RS-68 to a much higher thrust than the existing upgrade, etc. All these were done for various *missions* with various customers, each comes with impact on cost, schedule and varying degree of risks. But don't ask me about these results, they are proprietary first of all, then the issue of ITAR, FOUO, etc... yikes!
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#114
by
tnphysics
on 26 Sep, 2007 23:54
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Where can I find information about the Delta IV Heavy upgrades beyond what is on astonautix.com etc.?
I didn't know about the widend CBC.
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#115
by
Propforce
on 27 Sep, 2007 00:11
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tnphysics - 26/9/2007 4:54 PM
Where can I find information about the Delta IV Heavy upgrades beyond what is on astonautix.com etc.?
I didn't know about the widend CBC.
Why do you need to know?
:cool:
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#116
by
tnphysics
on 27 Sep, 2007 00:13
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Just curious.
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#117
by
kevin-rf
on 27 Sep, 2007 03:35
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tnphysics - 26/9/2007 8:13 PM
Just curious.
pre ULA they where clearly posted on the boeing site. I am sure one of the forums digital pack rats has a copy somewhere. If not google is your friend... I am sure they are findable... I know the graphic has been posted several times on this forum.
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#118
by
meiza
on 27 Sep, 2007 11:10
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Yeah, it was named "delta evolution chart" or something like that.
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#119
by
tnphysics
on 27 Sep, 2007 22:30
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Okay. Why didn't the Delta IV developers go with a wider twin engine upper stage?