Author Topic: Delta IV Q&A  (Read 243294 times)

Offline Propforce

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Re: Delta IV Q&A
« Reply #240 on: 12/28/2007 09:04 pm »
OK... can someone tell me how to up load a 8 megabytes PDF document ?  This thing won't let me upload anything more than 100K  :frown:

Offline Antares

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Re: Delta IV Q&A
« Reply #241 on: 12/29/2007 06:09 am »
Hmmm.  I'm not sure which takes precedence, that the paper was produced by taxpayer dollars or AIAA (copy)rights.  I've had problems uploading too.  I can't remember what I did to fix it.  Maybe PM Chris.
If I like something on NSF, it's probably because I know it to be accurate.  Every once in a while, it's just something I agree with.  Facts generally receive the former.

Offline meiza

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Re: Delta IV Q&A
« Reply #242 on: 12/29/2007 11:23 am »
Interesting, how were these improvements discovered? Were they in the pipeline during the original RS-68 development but time ran out since EELV had a deadline?

Offline Damon Hill

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Re: Delta IV Q&A
« Reply #243 on: 12/29/2007 09:04 pm »
The RS-68 was biased towards cost rather than performance; the current round of enhancements mostly involve improving the existing design without major changes like a fully regenerative nozzle.  Others, like reduction of the hydrogen flare at ignition, are driven more by possible safety issues, or just reducing the appearance of problems.  I'd like to see a COBRA-style high-performance engine (sort of a simplified SSME with higher thrust), but the money isn't there for radical changes in design.

Offline kevin-rf

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Re: Delta IV Q&A
« Reply #244 on: 12/30/2007 12:13 am »
Interesting how much they are trying to reduce helium use ... Any chance that by the time they are done it will use less helium than LH ;)
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Offline Antares

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Re: Delta IV Q&A
« Reply #245 on: 12/30/2007 03:05 am »
Helium requirements are almost entirely driven by KSC infrastructure limits.  Future helium costs were secondary when the requirements were written, though the white papers have helped make the point.
If I like something on NSF, it's probably because I know it to be accurate.  Every once in a while, it's just something I agree with.  Facts generally receive the former.

Offline Nick L.

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Re: Delta IV Q&A
« Reply #246 on: 01/01/2008 02:35 am »
Wow, so much great info! This thread is this forum at its best. That's why I love this place. :)
"Now you may leave here for four days in space, but when you return it's the same old place..."

Offline sticksux

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Re: Delta IV Q&A
« Reply #247 on: 01/01/2008 11:02 pm »
Why it was decided to use LH+LOX first stage for Delta IV? It seems to be a step backwards from Delta II and III.

Offline Jim

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Re: Delta IV Q&A
« Reply #248 on: 01/01/2008 11:11 pm »
Clean burning.

Offline McDew

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Re: Delta IV Q&A
« Reply #249 on: 01/02/2008 01:42 am »
Actually the decision was driven by what was available in the US industry. Atlas wanted LOX/RP, but Rocketdyne could not develop a cost effective current technology high thrust/performance engine which led them to go the RD-180 route.  Boeing's strategy was to stay with a US built engine which drove them to a RS-68 shuttle derived engine with the hope of maintaining shuttle/NASA cost synergy which is paying off with planned upgrades.

Offline Jim

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Re: Delta IV Q&A
« Reply #250 on: 01/02/2008 01:47 am »
Quote
McDew - 1/1/2008  9:42 PM

Actually the decision was driven by what was available in the US industry. Atlas wanted LOX/RP, but Rocketdyne could not develop a cost effective current technology high thrust/performance engine which led them to go the RD-180 route.  Boeing's strategy was to stay with a US built engine which drove them to a RS-68 shuttle derived engine with the hope of maintaining shuttle/NASA cost synergy which is paying off with planned upgrades.

Not quite.  RS-68 was designed specifically for the Delta-IV.  Atlas went to the RD-180 when Rocketdyne couldn't handle two engine developments.

Offline Propforce

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Re: Delta IV Q&A
« Reply #251 on: 01/02/2008 01:54 am »
Quote
Jim - 1/1/2008  6:47 PM
  Atlas went to the RD-180 when Rocketdyne couldn't handle two engine developments.

 Rocketdyne could not compete with the price of RD-180 offerred by the Russians.  


Offline Propforce

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Re: Delta IV Q&A
« Reply #252 on: 01/02/2008 01:59 am »
Quote
sticksux - 1/1/2008  4:02 PM

Why it was decided to use LH+LOX first stage for Delta IV? It seems to be a step backwards from Delta II and III.

Why is it backward to have a H2 first stage?


Offline McDew

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Re: Delta IV Q&A
« Reply #253 on: 01/02/2008 02:01 am »
Boeing did not go the Rocketdyne LOX/RP route for the same reasons as Atlas.  The US was 20 years behind in the LOX/RP engine technology and the cost to catch up would kill any proposal.

Offline tnphysics

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Re: Delta IV Q&A
« Reply #254 on: 01/02/2008 04:19 am »
Couldn't you just restart RS-84 development?

Offline sticksux

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Re: Delta IV Q&A
« Reply #255 on: 01/02/2008 09:54 am »
Quote
Propforce - 2/1/2008  2:59 AM
Quote
sticksux - 1/1/2008  4:02 PM
Why it was decided to use LH+LOX first stage for Delta IV? It seems to be a step backwards from Delta II and III.
Why is it backward to have a H2 first stage?

Because LH stage costs more than equivalent (in lifting capability) kerolox one. Ask yourself - why SpaceX didn't go LH route?

Offline meiza

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Re: Delta IV Q&A
« Reply #256 on: 01/02/2008 11:45 am »
Quote
sticksux - 2/1/2008  10:54 AM

Quote
Propforce - 2/1/2008  2:59 AM
Quote
sticksux - 1/1/2008  4:02 PM
Why it was decided to use LH+LOX first stage for Delta IV? It seems to be a step backwards from Delta II and III.
Why is it backward to have a H2 first stage?

Because LH stage costs more than equivalent (in lifting capability) kerolox one. Ask yourself - why SpaceX didn't go LH route?

An LH2 gas-generator engine (with an ablative nozzle!) is much much simpler and cheaper than an oxygen rich kerolox staged combustion one, if produced in the US. And still has better ISP. I bet that was one of the reasons... There was LH2 experience from the SSME and STME that were clearly assets and competetive advantages.

Offline TrueGrit

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Re: Delta IV Q&A
« Reply #257 on: 01/02/2008 04:22 pm »
The Delta IV decision on LH2/LOx first stage is an example of a decision based on all four aspects of real-world engineering performance-cost-schedule-manufacturing (both recurring and nonrecurring).  Anyone who considers it a "step-backward" isn't taking into account all considerations...  Delta (under MacDac) traded LH2 and RP1 during the proposal phase and found significant benefits to go with LH2, a big one being the high maturity of the Rocketdyne engine proposal.  While I don't want to go into details the Delta and Atlas trades are good examples for those of you guys in school planning on joining us in the real-world...  Real trade studies often involve all the aspects of the business.

Offline meiza

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Re: Delta IV Q&A
« Reply #258 on: 01/02/2008 05:09 pm »
Quote
TrueGrit - 2/1/2008  5:22 PM

The Delta IV decision on LH2/LOx first stage is an example of a decision based on all four aspects of real-world engineering performance-cost-schedule-manufacturing (both recurring and nonrecurring).  Anyone who considers it a "step-backward" isn't taking into account all considerations...  Delta (under MacDac) traded LH2 and RP1 during the proposal phase and found significant benefits to go with LH2, a big one being the high maturity of the Rocketdyne engine proposal.  While I don't want to go into details the Delta and Atlas trades are good examples for those of you guys in school planning on joining us in the real-world...  Real trade studies often involve all the aspects of the business.

Well, LH2 seems to lose on all the other sectors than ISP (which is an important thing ofc).
Ground equipment: pumps, vacuum jacketed piping, hydrogen leaks easily, issue of fuel cost and storability, density, temperature...
Rocket (other than the engine): Low density makes a bulky stage which is expensive to make and transport and is draggy in flight, low temp means you need more insulation, purges, bellows in the lines etc...
But there was experience in all of this.

Offline edkyle99

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Re: Delta IV Q&A
« Reply #259 on: 01/02/2008 05:34 pm »
Quote
TrueGrit - 2/1/2008  11:22 AM

The Delta IV decision on LH2/LOx first stage is an example of a decision based on all four aspects of real-world engineering performance-cost-schedule-manufacturing (both recurring and nonrecurring).  Anyone who considers it a "step-backward" isn't taking into account all considerations...  Delta (under MacDac) traded LH2 and RP1 during the proposal phase and found significant benefits to go with LH2, a big one being the high maturity of the Rocketdyne engine proposal.  While I don't want to go into details the Delta and Atlas trades are good examples for those of you guys in school planning on joining us in the real-world...  Real trade studies often involve all the aspects of the business.

The results of this very interesting "trade study" are still pending, but seem, based on recent and projected EELV flight rates, to be leaning right now toward the Atlas staged combustion RP/LOX choice.  The results are not final.  One monster Atlas pad explosion, Sea Launch style for example, could change everything.  

 - Ed Kyle

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