Author Topic: The design of the Delta IV  (Read 15876 times)

Offline Lobo

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The design of the Delta IV
« on: 05/10/2013 09:55 pm »
Over in another thread this subject got hit on.  Why did Delta IV get designed like it did?  Why was it so different than Delta II and Delta III?  Both of those used a kerolox RS-27A sustainer engine with a cluster of GEM boosters.  However, with Delta IV they went with a brand new hydrolox engine, new larger GEM boosters as options (rather than required like Delta 2/3), a much wider core at 5m, etc.

Conversely, it looks like Atlas 2 to Atlas 3 to Atlas 5 was a much more synergetic progression.  Keeping kerolox, and just improving the engine and widening up the core some. (and Iím sure other improvements in avionics and such).

So what was McDonnel-Douglas/Boeing thinking on this upgrade?  Iím sure they have great engineers, and there was probably good reasons for it, Iím just not seeing them.  Plus, thereís a reason that hydrolox is normally only used for an upper stage, or systainer stage with some other higher thrust boosters.  Itís just not the greatest 1st stage booster propellant, and itís the most difficult propellant to handle.  So to make that issue larger by making the booster all hydrolox, as well as just the upper stage?  Iím guessing thereís a reason that hadnít been done before?
From my uneducated view I wonder about a few things.

a)   Why didnít they stick with RS-27A, and widen up the core and go with more of them.  2, 3 or four depending on how powerful they wanted to go?  RS-27A is based on the H-1, which was supposed to be a pretty cheap and simple engine.  Was cost an issue with RS-27A?  Itíd probably have to be a large issue, to warrent development of a new hydrolox engine, even one that had already had development done on it (as I understand the RS-68 had already had development on it).  Seems like a more incremental step would be increasing the Delta 2/3 2.4m diameter kerolox core with something like 3-3.5m  And then have the GEM-60ís developed and put a cluster of them on it as well?  Or just have like four RS-27Aís and go with something more F9 and Atlas V diameter.  3.6-3.8m?
b)   If they wanted to stick with just a single core engine, instead of multiple RS-27ís, why not have PWR update the F-1A, instead of the RS-68?  They are both kerolox gas generators.  With the 5m core that Delta IV got, they could mount a single F-1A on it, and probably just have a stretched DCSS to compensate for the lower ISP of the F-1A vs. RS-68.  Iíd assume that updating the F-1A would be roughly the same price, or cheaper, than finishing development on the RS-68?  Or is that incorrect?  Just that single F-1A could boost a 4.5-5m core a stretched DCSS and have performance probably in the D4H range, but with no more actual hardware and costs than a Delta IV-medium.

I mean, Iíd assume that most of the cost of an upper stage is in the systems, not the physical length of the cylindrical tanks.  The physical amount of alloy is a pretty small fraction of the cost I think.  If it needed two RL-10ís, thatíd be a little more.  But RL-60ís were like 90% developed anyway.  That might be a good engine for such an LV. 
A 5m kerolox core would look a lot like Atlas Phase 2 in size.  Just with a single F-1A engine.  It would have the same footprint, so the launch facilities at LC-37 wouldnít be any larger.  And the tri-core heavy version would probably not even be needed by USAF/DoD, given the capacity of it.  If a little more performance was needed, it could mount GEM-60ís just like the 5m Delta IV does anyway. 

Seems like youíd have an EELV-heavy launch vehicle, for the approximate costs of a single stick Delta IV-medium without SRBís.  Seems like a more obvious way to go.

Or just go with the scaled up Delta 2/3, a little wider diameter core with like two RS-27Aís and a cluster of 9 GEM-60ís instead of 9 GEM-46ís. 

Seems like either would have been a more incremental evolution of the Delta rocket.
Instead they take quite a turn to go from 2.4m core to 5m core, hydrolox instead of kerolox.  From about a 25m long core to a 40m long core.  Form integral SRBís to optional SRBís.  Just wondering why.

And sorta thinking that if Delta IV had been a 5m wide LV with a single F-1A engine, that that might have been a building block LV that NASA may have evaluated more closely during ESAS.  It should have gotten Orion to LEO by itself.  And stretching the core and putting two F-1ís on it would make something like the Dynetics booster, and a tri-core version of that would have made a pretty good 1.5 launch architecture, with a lot of synergy with EELVís. 
The tri-core would have just probably needed a new larger upper stage and/or EDS, which NASA could have made themselves.

OrÖfor more synergy, a 2-launch architecture with two tri-core heavies of the single engine cores.  That should have gotten something like 120-140mt to LEO Iíd think.  It would have basically been Atlas Phase 2, but already developed an flying.  And with a storied US built engine.
 
« Last Edit: 05/11/2013 04:24 pm by Chris Bergin »

Offline simonbp

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Re: Why did was Delta IV designed like it was?
« Reply #1 on: 05/10/2013 11:23 pm »
Delta IV is a direct descendant of NLS III.

The NLS program was built around the STME, which was a cost-reduced expendable version of SSME. The NLS I used an ET core with STMEs and two shuttle SRBs. NLS II was smaller version with ET tank and no SRBs and old Atlas-style stage and-a-half. NLS III was an even smaller version with one STME and 5.5 m tanks.

Boeing continued to develop the concept after NLS was canned and proposed it for the competition that became EELV, with a an ablative nozzle version of the STME called RS-68. When Boeing and McDonnell Douglas merged, the rocket became known as Delta IV.

EDIT: This explains the logic a bit:

http://books.google.com/books?id=eWbO9JJoAogC&lpg=PA258&ots=9_LV1L0-ID&dq=%22NLS%20III%22%20stme&pg=PA259#v=onepage&q=%22NLS%20III%22%20stme&f=false
« Last Edit: 05/10/2013 11:30 pm by simonbp »

Offline Jim

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Re: Why did was Delta IV designed like it was?
« Reply #2 on: 05/11/2013 01:52 am »
Delta IV is a direct descendant of NLS III.

The NLS program was built around the STME, which was a cost-reduced expendable version of SSME. The NLS I used an ET core with STMEs and two shuttle SRBs. NLS II was smaller version with ET tank and no SRBs and old Atlas-style stage and-a-half. NLS III was an even smaller version with one STME and 5.5 m tanks.

Boeing continued to develop the concept after NLS was canned and proposed it for the competition that became EELV, with a an ablative nozzle version of the STME called RS-68. When Boeing and McDonnell Douglas merged, the rocket became known as Delta IV.


Correction, it was all McDonnell Douglas.  Heritage Boeing was never involved in Delta IV, it only became Boeing through the merger.  Boeing lost out of the EELV competition when it went from 4 to 2 contractors.  Boeing then developed Sealaunch to get in the launcher business.

There are photos of Boeing's EELV proposal on L2.
http://forum.nasaspaceflight.com/index.php?topic=29906.0
« Last Edit: 05/11/2013 01:56 am by Jim »

Offline Lobo

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Re: Why did was Delta IV designed like it was?
« Reply #3 on: 05/11/2013 02:34 am »
Delta IV is a direct descendant of NLS III.

The NLS program was built around the STME, which was a cost-reduced expendable version of SSME. The NLS I used an ET core with STMEs and two shuttle SRBs. NLS II was smaller version with ET tank and no SRBs and old Atlas-style stage and-a-half. NLS III was an even smaller version with one STME and 5.5 m tanks.

Boeing continued to develop the concept after NLS was canned and proposed it for the competition that became EELV, with a an ablative nozzle version of the STME called RS-68. When Boeing and McDonnell Douglas merged, the rocket became known as Delta IV.


Correction, it was all McDonnell Douglas.  Heritage Boeing was never involved in Delta IV, it only became Boeing through the merger.  Boeing lost out of the EELV competition when it went from 4 to 2 contractors.  Boeing then developed Sealaunch to get in the launcher business.

There are photos of Boeing's EELV proposal on L2.
http://forum.nasaspaceflight.com/index.php?topic=29906.0

Very interesting Jim.  Thank you.

So Delta 4 was the result do MD work on NLS or something?

I'm still a little confused.  delta 2 was Boeing's design right?

So was Delta 4 completely a MD design with no relationship to Delta 2/3, but they just called it a Delta anyway?
« Last Edit: 05/11/2013 02:36 am by Lobo »

Offline Galactic Penguin SST

Re: Why did was Delta IV designed like it was?
« Reply #4 on: 05/11/2013 02:41 am »
Delta IV is a direct descendant of NLS III.

The NLS program was built around the STME, which was a cost-reduced expendable version of SSME. The NLS I used an ET core with STMEs and two shuttle SRBs. NLS II was smaller version with ET tank and no SRBs and old Atlas-style stage and-a-half. NLS III was an even smaller version with one STME and 5.5 m tanks.

Boeing continued to develop the concept after NLS was canned and proposed it for the competition that became EELV, with a an ablative nozzle version of the STME called RS-68. When Boeing and McDonnell Douglas merged, the rocket became known as Delta IV.


Correction, it was all McDonnell Douglas.  Heritage Boeing was never involved in Delta IV, it only became Boeing through the merger.  Boeing lost out of the EELV competition when it went from 4 to 2 contractors.  Boeing then developed Sealaunch to get in the launcher business.

There are photos of Boeing's EELV proposal on L2.
http://forum.nasaspaceflight.com/index.php?topic=29906.0

Very interesting Jim.  Thank you.

So Delta 4 was the result do MD work on NLS or something?

I'm still a little confused.  delta 2 was Boeing's design right?

So was Delta 4 completely a MD design with no relationship to Delta 2/3, but they just called it a Delta anyway?

The whole Thor-Delta series from 1960 was done by Douglas, which became McD, then merged into Boeing in 1997. So your 2nd question is wrong, while the other two are correct.  ;)
Astronomy & spaceflight geek penguin. In a relationship w/ Space Shuttle Discovery. Current Priority: Chasing the Chinese Spaceflight Wonder Egg & A Certain Chinese Mars Rover

Offline Jim

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Re: Why did was Delta IV designed like it was?
« Reply #5 on: 05/11/2013 02:45 am »
Delta IV is a direct descendant of NLS III.

The NLS program was built around the STME, which was a cost-reduced expendable version of SSME. The NLS I used an ET core with STMEs and two shuttle SRBs. NLS II was smaller version with ET tank and no SRBs and old Atlas-style stage and-a-half. NLS III was an even smaller version with one STME and 5.5 m tanks.

Boeing continued to develop the concept after NLS was canned and proposed it for the competition that became EELV, with a an ablative nozzle version of the STME called RS-68. When Boeing and McDonnell Douglas merged, the rocket became known as Delta IV.


Correction, it was all McDonnell Douglas.  Heritage Boeing was never involved in Delta IV, it only became Boeing through the merger.  Boeing lost out of the EELV competition when it went from 4 to 2 contractors.  Boeing then developed Sealaunch to get in the launcher business.

There are photos of Boeing's EELV proposal on L2.
http://forum.nasaspaceflight.com/index.php?topic=29906.0

Very interesting Jim.  Thank you.

So Delta 4 was the result do MD work on NLS or something?

I'm still a little confused.  delta 2 was Boeing's design right?

So was Delta 4 completely a MD design with no relationship to Delta 2/3, but they just called it a Delta anyway?

Boeing had nothing to do with Delta.  Delta was Thor heritage which was produce by Douglas pre 1968 and MD there after.  The 4m upperstage on Delta 3 became the 4m upperstage on Delta IV.  MD wanted to leverage the LH2 experience in the industry and the large diameter from its Titan IV fairing work and have common propellants for all stages for Delta IV
« Last Edit: 05/11/2013 02:45 am by Jim »

Online catdlr

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Re: Why did was Delta IV designed like it was?
« Reply #6 on: 05/11/2013 03:07 am »
This may help some: Rocket Genealogy

Tony De La Rosa

Offline Lobo

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Re: Why did was Delta IV designed like it was?
« Reply #7 on: 05/11/2013 03:44 am »
Quote from: Jim link=topic=31873.msg1050160#msg1050160 date


Boeing had nothing to do with Delta.  Delta was Thor heritage which was produce by Douglas pre 1968 and MD there after.  The 4m upperstage on Delta 3 became the 4m upperstage on Delta IV.  MD wanted to leverage the LH2 experience in the industry and the large diameter from its Titan IV fairing work and have common propellants for all stages for Delta IV

Ok...so Douglas created Delta, the MD after that. 
So that still leaves my original question, why wasn't Delta 4 an evolved Delta 2/3 instead of such a different animal altogether?

MD wanted to leverage LH2 experience in the industry?  Weren't The complex reusable RS-25 and the upper stage only RL-10 the only LH2 engines in the US then?
Why wouldn't they want to leverage existing gas generator kerolox experience they already had with RS-27?   Or larger with the F-1A?
Or the RS-84 in development that was based on the new ORSC tech from the Russians?

It still really seems like an unusual left turn suddenly.  Especially since LH2 isn't a particularly great booster propellant compared to Kerolox...(or even solids)
I mean there was a reason that the S-1C was kerolox, instead of he Saturn V being all hydrolox and the shuttle had solid boosters rather than being all hydrolox. 
Ditto for Araine 5 and other rockets around when Delta 4 was designed.


Online edkyle99

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Re: Why did was Delta IV designed like it was?
« Reply #8 on: 05/11/2013 03:57 am »
a)Why didnít they stick with RS-27A, and widen up the core and go with more of them.  2, 3 or four depending on how powerful they wanted to go? 
Given the limitations imposed by the original EELV requirements, McDonnell Douglas would have needed 6 to 8 of those H-1 type engines on each core and a bigger upper stage powered by more than one RL-10 engine.  A Heavy then would have ended up with 18 to 24 booster engines.  Those things weren't cheap.  Delta would have flat out lost the proposal to a staged combustion Atlas.

Strap-on solids would have made the task far easier, but weren't allowed.  General Dynamics showed how during the 1980s with its original "Atlas II/Centaur G-PRIME" proposal for CELV (won by Titan IV).  That proposal used five H-1D engines on a 200 inch core augmented by four 67 inch diameter solids motors (SRB-A class). 

McDonnell Douglas did contemplate a fatter Delta.  During the late 1980s or early 1990s it studied a 2xRS-27A core with 12 strap-on solid motors, topped by a bigger upper stage.  That led to Delta III, with more powerful solid motors taking the place of the dual core engine approach.

 - Ed Kyle

Offline simonbp

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Re: Why did was Delta IV designed like it was?
« Reply #9 on: 05/11/2013 05:25 am »
Given the limitations imposed by the original EELV requirements, McDonnell Douglas would have needed 6 to 8 of those H-1 type engines on each core and a bigger upper stage powered by more than one RL-10 engine. 

Well that sounds familiar. ;)

Offline Lobo

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Re: Why did was Delta IV designed like it was?
« Reply #10 on: 05/11/2013 06:19 am »
Given the limitations imposed by the original EELV requirements, McDonnell Douglas would have needed 6 to 8 of those H-1 type engines on each core and a bigger upper stage powered by more than one RL-10 engine. 

Well that sounds familiar. ;)

Heheheheh....nice point!

But I thought that H-1's were supposed to be relatively cheap?
Or could they have been more streamlined and automated if there'd been a relatively large production run of them?
I mean, aren't they sort of a larger Merlin 1?  The economics of needing nine of those on an EELV-class launcher seem to be working out so far for SpaceX.  ;-)

But, Merlin 1's were designed some 50 years after the H-1 and a modern production facility was put together for them, so perhaps the H-1's couldn't be made in a mass produced, cost effective way by PWR for McDonnell-Douglas?
I don't know, but I'd think they could, maybe?

Offline Lobo

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Re: Why did was Delta IV designed like it was?
« Reply #11 on: 05/11/2013 06:42 am »
a)Why didnít they stick with RS-27A, and widen up the core and go with more of them.  2, 3 or four depending on how powerful they wanted to go? 
Given the limitations imposed by the original EELV requirements, McDonnell Douglas would have needed 6 to 8 of those H-1 type engines on each core and a bigger upper stage powered by more than one RL-10 engine.  A Heavy then would have ended up with 18 to 24 booster engines.  Those things weren't cheap.  Delta would have flat out lost the proposal to a staged combustion Atlas.

Strap-on solids would have made the task far easier, but weren't allowed.  General Dynamics showed how during the 1980s with its original "Atlas II/Centaur G-PRIME" proposal for CELV (won by Titan IV).  That proposal used five H-1D engines on a 200 inch core augmented by four 67 inch diameter solids motors (SRB-A class). 

McDonnell Douglas did contemplate a fatter Delta.  During the late 1980s or early 1990s it studied a 2xRS-27A core with 12 strap-on solid motors, topped by a bigger upper stage.  That led to Delta III, with more powerful solid motors taking the place of the dual core engine approach.

 - Ed Kyle

I'm not at all familiar with the EELV requirements, but the basic Atlas V only has 860klbs thrust.  Four H-1B's wou'd have 820klbs, and five would have 1025klbs.  Why would MD need 6-8 H-1's?
That's be Saturn 1 class rather than Atlas V-401 or Delta IV-Medium class, which are the basic versions of those EELV's.

And the initial RS-68 only put out 668klbs of thrust.  Three H-1B would get you close to that.

And that's assuming the H-1 couldn't be tweaked to put out a little more thrust.

And it could have used SRB augmentation for more performance, because Atlas V and Delta IV both do.  So I'm assuming that was ok.

Now, the H-1's aren't as efficient as either the RD-180 or RS-68, but the Merlin 1's are GG kerolox as well, and they seem to work pretty good.  Falcon doesn't have great BLEO performance, but I sort of assumed that had more to do with the kerolox upper stage than the kerolox GG booster?
So why couldn't Delta IV have basically been a Falcon 9, but with five H-1 engines and a stretched Delta III upper stage?  And if an RL-10 wouldn't be enough, what about an RL-60?
Again, as I understand, the RL-60 was 90% developed anyway.
Was RL-10 a common engine prior to the EELV's, in that in was desirable to keep using it? 
I think it was only used on Centaur on certain Titan IV launches...right?
It wasn't quite the mainstay upper stage engine it's been since the EELV's started flying back then, was it?

So, I'm wondering why not a modernized H-1 engine, maybe boosting it's thrust to around 225klbs and put four of them on a 3.6m core (1Mlbs total) with a stretched Delta III upper stage with an RL-60 engine?
Wouldn't that have been as competative of a proposal as developing the RS-68, and more synergetic with the Delta family?
And have various optional GEM-60 SRB augmentation options as well?
Or a tri-core heavy?
« Last Edit: 05/11/2013 06:45 am by Lobo »

Offline Jim

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Re: Why did was Delta IV designed like it was?
« Reply #12 on: 05/11/2013 12:08 pm »

MD wanted to leverage LH2 experience in the industry?  Weren't The complex reusable RS-25 and the upper stage only RL-10 the only LH2 engines in the US then?
Why wouldn't they want to leverage existing gas generator kerolox experience they already had with RS-27?   Or larger with the F-1A?
Or the RS-84 in development that was based on the new ORSC tech from the Russians?

It still really seems like an unusual left turn suddenly.  Especially since LH2 isn't a particularly great booster propellant compared to Kerolox...(or even solids

And most of the people in the engine industry had LH2 experience.  SSME and RL-10 had/were going through various upgrades.  There was only  sustaining engineering of the RS-27.

MD wanted a common propellant also
« Last Edit: 05/11/2013 12:14 pm by Jim »

Offline Jim

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Re: Why did was Delta IV designed like it was?
« Reply #13 on: 05/11/2013 12:12 pm »

And it could have used SRB augmentation for more performance, because Atlas V and Delta IV both do.  So I'm assuming that was ok.


Not for the original USAF requirements.  Commercial requires drove the addition of solids.  Reliability and cost drove the single engine design.

Online edkyle99

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Re: Why did was Delta IV designed like it was?
« Reply #14 on: 05/11/2013 03:30 pm »
I'm not at all familiar with the EELV requirements, but the basic Atlas V only has 860klbs thrust.  Four H-1B's wou'd have 820klbs, and five would have 1025klbs.  Why would MD need 6-8 H-1's?
Specific impulse differences.  The H-1 gas generator cycle was less efficient than the RD-180 staged combustion cycle.  Less efficient meant more propellant which meant more thrust.  The effect cascades.  The engines were 15% less efficient, but the rocket would have to weigh 35-40% more.

A bigger upper stage would allow for a smaller first stage and use of only six H-1 engines, but that bigger upper stage, which would have to carry twice as much propellant as Centaur, would need more RL10s (probably two for GTO and four for LEO missions).  Five H-1 engines simply can't lift enough to meet the EELV Medium GTO requirement, no matter how big the upper stage.  Unless, of course, McDonnell Douglas had added a third stage - a move adding more costs.

 - Ed Kyle
« Last Edit: 05/11/2013 03:52 pm by edkyle99 »

Online Chris Bergin

Re: The design of the Delta IV
« Reply #15 on: 05/11/2013 04:25 pm »
Terrible thread title resolved! ;)
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Offline Lobo

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Re: The design of the Delta IV
« Reply #16 on: 05/11/2013 09:44 pm »
Terrible thread title resolved! ;)

Thanks Chris!

Offline Lobo

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Re: Why did was Delta IV designed like it was?
« Reply #17 on: 05/11/2013 10:05 pm »

MD wanted to leverage LH2 experience in the industry?  Weren't The complex reusable RS-25 and the upper stage only RL-10 the only LH2 engines in the US then?
Why wouldn't they want to leverage existing gas generator kerolox experience they already had with RS-27?   Or larger with the F-1A?
Or the RS-84 in development that was based on the new ORSC tech from the Russians?

It still really seems like an unusual left turn suddenly.  Especially since LH2 isn't a particularly great booster propellant compared to Kerolox...(or even solids

And most of the people in the engine industry had LH2 experience.  SSME and RL-10 had/were going through various upgrades.  There was only  sustaining engineering of the RS-27.

MD wanted a common propellant also

Hmmm...

Didn't most people in the industry also have RP-1 experience?

And I can understand a common propellant.  The Russians and SpaceX went that route too. 
But...take Atlas V.  You have three liquids.  LH2, LOX, and RP-1.

If you want to remove one to make things more simple and streamlined, it doesn't seem like removing the most simple and easy to pump, transport, and store really helps things much.  You'd think they'd remove the most difficult by far to work with...LH2.

I mean, I understand the higher performing LH2...but if you are going for simplicity, it seems a little counter intuitive to cut out the most easy liquid to work with and make it so you need even more of the most difficult liquid to work with.
Especially since a lot of the advantages of the ISP of LH2 isn't really realized until after the "booster" phase of ascent. 
Using LH2 to get off the pad is a little like trying to start a car on an uphill incline in 5th gear...is it not?

Better to start in a high torque low speed gear, no?

Offline Thorny

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Re: The design of the Delta IV
« Reply #18 on: 05/11/2013 10:24 pm »
It was a progression toward a simpler vehicle in theory. If you stick to Delta, you have...

Delta II... RP-1, LOX, Aerozine 50 and N204 (four liquids)
Delta III... RP-1, LOX, LH2 (three liquids)
Delta IV... LH2, LOX (two liquids)

Offline Hyperion5

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Re: Why did was Delta IV designed like it was?
« Reply #19 on: 05/12/2013 03:53 am »
I'm not at all familiar with the EELV requirements, but the basic Atlas V only has 860klbs thrust.  Four H-1B's wou'd have 820klbs, and five would have 1025klbs.  Why would MD need 6-8 H-1's?
Specific impulse differences.  The H-1 gas generator cycle was less efficient than the RD-180 staged combustion cycle.  Less efficient meant more propellant which meant more thrust.  The effect cascades.  The engines were 15% less efficient, but the rocket would have to weigh 35-40% more.

A bigger upper stage would allow for a smaller first stage and use of only six H-1 engines, but that bigger upper stage, which would have to carry twice as much propellant as Centaur, would need more RL10s (probably two for GTO and four for LEO missions).  Five H-1 engines simply can't lift enough to meet the EELV Medium GTO requirement, no matter how big the upper stage.  Unless, of course, McDonnell Douglas had added a third stage - a move adding more costs.

 - Ed Kyle

So the ratio you're saying that if we want to launch the same amount of payload to orbit, the rough rule of thumb is that a 1% increase in booster engine Isp results in a 2.33-2.66% lighter rocket?  With regards to the Delta IV though, wouldn't the superior impulse density of the RD-180 make the Atlas V the more optimized LV? 

There's one other thing about the Delta IV that bothers me besides an all-hydrolox design.  It's the complete and utter lack of common bulkheads anywhere in the design.  I'm looking at the design overview diagram of the Ariane 5 ECA (http://en.wikipedia.org/wiki/File:Cut_drawing_of_an_Ariane_5_ECA_EN.svg), and it's clear that LV was mass-optimized.  That in turn allows Ariane to use less expensive engines for the same level of performance.  Why, if the Delta IV has to overcome the drawbacks of an all-hydrolox design, did they not follow Ariane's lead?  I've heard explanations that it was considered a 'bridge too far' and so on, but it seems like a wasted opportunity.  I'm curious, if the Delta IV did feature Ariane 5-style common bulkheads, just how much would that affect its performance and dry mass? 

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