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#600
by
kevin-rf
on 25 May, 2015 13:01
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In reality, Vulcan is that evolution.
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#601
by
edkyle99
on 25 May, 2015 16:17
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Hi, i have some questions about the Delta 4:
Why is it being retired instead of being evolved into a less costly rocket? Basically ULA has this great vehicle and are going to just throw it away! F9 had to evolve to meat the commercial market, why not D4?
Gotta be cheaper than developing Vulcan from scratch^.^
The company that builds Delta 4 already has a lower-cost alternative for all but the Heavy missions (Atlas 5). Last year it considered increasing the Delta 4 production rate to offset the RD-180 issue, but soon switched to the plan to develop Vulcan instead. Presumably Vulcan will cost less than Delta 4 over its life, including development costs.
Atlas 5/Vulcan already has a better upper stage (Centaur). Delta 4 would need a vastly improved first stage (cost and performance) to survive. That means a new main engine, which means just as much development as Vulcan.
- Ed Kyle
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#602
by
baldusi
on 25 May, 2015 16:31
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Hi, i have some questions about the Delta 4:
Why is it being retired instead of being evolved into a less costly rocket? Basically ULA has this great vehicle and are going to just throw it away! F9 had to evolve to meat the commercial market, why not D4?
Gotta be cheaper than developing Vulcan from scratch^.^
Delta IV is not that great. You can't get Atlas V 431/531/541/551 performance with a single stick. The integration process is longer and more expensive. Also, it has less launch rate per pad. It needs two different upper stages and there's a reason that the Common Upper Stage is based on Centaur. Its avionics were replaced with Atlas'. It had a lot of different fairings. You need at least four different cores models to offer the full performance design. It's not human rated. And its engine is ablatively cooled and thus has no reuse potential. Also its manufacturer has a lot of overhead because it was designed to mount on the SSME infrastructure. And there are no equivalent engines in the world to replace it with like they are able to with the RD-180.
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#603
by
Patchouli
on 26 May, 2015 13:21
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Delta IV is not that great. You can't get Atlas V 431/531/541/551 performance with a single stick. The integration process is longer and more expensive. Also, it has less launch rate per pad. It needs two different upper stages and there's a reason that the Common Upper Stage is based on Centaur. Its avionics were replaced with Atlas'. It had a lot of different fairings. You need at least four different cores models to offer the full performance design. It's not human rated. And its engine is ablatively cooled and thus has no reuse potential. Also its manufacturer has a lot of overhead because it was designed to mount on the SSME infrastructure. And there are no equivalent engines in the world to replace it with like they are able to with the RD-180.
Keep in mind the Areojet SRBs on the Atlas have about seven and a half tons more propellant then the GEM 60s on the Delta IV M+ and may be responsible for a good deal of the performance difference.
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#604
by
pippin
on 19 Mar, 2017 14:14
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#605
by
DatUser14
on 19 Mar, 2017 14:16
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#606
by
pippin
on 19 Mar, 2017 14:17
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Ah, thanks!
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#607
by
Jim
on 19 Mar, 2017 22:27
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In this image of the WGS-9 launch you can see that the Delta IV boosters have different aft skirts.
Why is that?
https://twitter.com/johnkrausphotos/status/843299763747479553
One pair has a fixed nozzle, the other pair has a gimballed nozzle. I don't know which is which.
The one will the longer skirt has TVC
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#608
by
pippin
on 19 Mar, 2017 22:35
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Thanks again.
Once you know it it's quite obvious how different the exhaust directions are for the different boosters.
Do the ones with TVC usually fire at less of an angle at liftoff? To decrease cosine losses or to limit the effect on the pad?
Is the impact of plume impingement lower at liftoff than at altitude so that they can simply do it?
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#609
by
MATTBLAK
on 19 Mar, 2017 22:57
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Has anyone ever published good, worked-out performance figures for a version of the single-stick with 8x GEM-60 solids, aluminum-lithium structures and the 5-meter D-IVH upper stage? And with a regenerative RS-68 prospect and all the above gear?
I'm willing to bet performance closing in on the Delta IV-Heavy, even with the standard RS-68A engine, and cheaper than the Heavy to boot.
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#610
by
sdsds
on 20 Mar, 2017 03:02
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Has anyone ever published good, worked-out performance figures for a version of the single-stick with 8x GEM-60 solids, aluminum-lithium structures and the 5-meter D-IVH upper stage? And with a regenerative RS-68 prospect and all the above gear? I'm willing to bet performance closing in on the Delta IV-Heavy, even with the standard RS-68A engine, and cheaper than the Heavy to boot.
Sorry I don't know the answer to your question but am responding anyway!
I think maybe no serious consideration has been given to 8x solids on DIV because one or more of:
- mounting 8x solids would require somewhat major modifications to the pads;
- supporting the loads would require a redesign of the core, interstage, upper stage, etc.
- DIV-H exists;
- Atlas V exists;
- Vulcan is in development.
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#611
by
MATTBLAK
on 20 Mar, 2017 09:23
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Delta with 8x solids should outperform Atlas V-551. I was recently told by someone who knows these things that 8x GEM-60 solids would be the most that could be accommodated with Delta on the corestage without major redesign, and even then the corestage engine would likely have to run a different throttling profile. The 8x solid concept was looked at early in the Delta's career but was abandoned early on. Anyway, if they ever were to continue with Delta; 4x better solids such as the GEM-63XL would suffice over 8x GEM-60s. But with Vulcan on the horizon, the mighty RS-68 will be retired and the Delta IV tooling heritage will live on with Vulcan.
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#612
by
edkyle99
on 20 Mar, 2017 13:13
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But with Vulcan on the horizon .... Delta IV tooling heritage will live on with Vulcan.
Maybe. Maybe not. Some hints have suggested that Vulcan diameter could grow fatter than Delta 4, to as much as 5.4 meters, the same as the payload fairing. Meanwhile, a 2 x AR-1 version, if that should happen, would likely be 3.81 meters (150 inches) in diameter, the same as the Atlas 5 CCB.
- Ed Kyle
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#613
by
sevenperforce
on 02 Mar, 2018 13:54
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How many pyro bolts does the Delta IV Common Booster Core use for separation from the Delta CSS?
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#614
by
gtae07
on 21 Jan, 2019 21:54
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I noticed during the recent NROL launch that the Heavy seems to ascend with the boosters "top and bottom" (I assume to reduce aerodynamic forces) and then rolls "wings level" for booster jettison. But then it appears to roll 45 degrees after jettison and through second stage ignition. Why is that?
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#615
by
Jim
on 23 Jan, 2019 19:21
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How many pyro bolts does the Delta IV Common Booster Core use for separation from the Delta CSS?
none, they don't use pyro bolts there
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#616
by
darkenfast
on 24 Jan, 2019 05:49
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Well, then: what do they use?
I'm willing to bet performance closing in on the Delta IV-Heavy, even with the standard RS-68A engine, and cheaper than the Heavy to boot.
