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.
Quote from: simonbp on 05/10/2013 11:23 pmDelta 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
Quote from: Jim on 05/11/2013 01:52 amQuote from: simonbp on 05/10/2013 11:23 pmDelta 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=29906.0Very 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
a)Why didn’t 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.
Quote from: edkyle99 on 05/11/2013 03:57 amGiven 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.
Quote from: Lobo on 05/10/2013 09:55 pma)Why didn’t 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
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 it could have used SRB augmentation for more performance, because Atlas V and Delta IV both do. So I'm assuming that was ok.
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?
Terrible thread title resolved!
Quote from: Lobo on 05/11/2013 03:44 amMD 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 solidsAnd 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
Quote from: Lobo on 05/11/2013 06:42 amI'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