Author Topic: Delta IV Q&A  (Read 243288 times)

Offline Propforce

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Re: Delta IV Q&A
« Reply #260 on: 01/02/2008 07:15 pm »
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sticksux - 2/1/2008  2:54 AM

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Propforce - 2/1/2008  2:59 AM
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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?

... and you think SpaceX is more successful than Delta IV?  :laugh:


Offline Propforce

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Re: Delta IV Q&A
« Reply #261 on: 01/02/2008 07:17 pm »
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TrueGrit - 2/1/2008  9:22 AM
  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.

Very good points, both you and Meiza made.  


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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... easy there now.  Remember those young kids are the FUTURE of this country !!!

... God help us !!!  :laugh:


Offline Propforce

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Re: Delta IV Q&A
« Reply #262 on: 01/02/2008 07:43 pm »
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meiza - 2/1/2008  10:09 AM

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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.


Not necessary.  LH2 first stage also has additional benefits.  First despite a "bulkier" first stage, the GTOW of vehicle is actually less than a RP first stage, so the booster engine require less thrust than a comparable RP engine.  You can even afford to loss LH2 propellant with less insulations and still outperform a RP first stage.  Common ground propellant equipment.  This is a BIG deal and costly.

For those of you comparing Delta IV with Atlas V as a "definitive study" on LH2 vs RP first stage really doesn't give enough credits to a LH2 first stage.  Delta IV made a few "mistakes" during its development while Atlas has the advantage of buying an essentially "off-the-shelf" cheap import with plenty of power to spare.

D-IV mistakes include 1) weight growth on the first stage design, and 2) a weak RL10B-2 as 2nd stage engine.  The 1st stage weigth growth greatly reduced the take-off thrust-weight of the vehicle.  Unfortunately; the thrust requirements of RS-68 was already negotiated with Rocketdyne at the time.  It would take an act-of-God, and all his money, to re-negotiate this requirement.  As result, the "common" booster core (CBC) were forced to be re-designed to become "individual" booster core in order to take weights out.

D-IV was designed for payloads to go to geosynchronous orbit (GSO), rather than at GTO and wave goodbye to payloads.  In fact, it's probably the only vehicle that can take payload to GEO than separate.  This way, payloads do not need to impart its propellant energy to circularize orbit, thus prolong payload life in GEO.  As result, the RL10B-2 was selected for its high Isp.  Unfortunately; its relative low thrust means a poor performance for LEO payloads.  Notice Atlas V has the same problem, but they use two RL10A-4 engines (dual engine centaur, DEC) to compensate for this shortfall.  So Atlas V has a higher LEO payload capability than D-IV.  D-IV attempted to solve this with its advanced upper stage (AUS) upgrade, with a 60K lbf upper stage engine.  This would greatly enable D-IV to compete with Atlas and the Arianne in the commercial payload sector.  But that funding got squashed along with the dot.com constellation business plan.


Offline sticksux

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Re: Delta IV Q&A
« Reply #263 on: 01/02/2008 09:52 pm »
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Propforce - 2/1/2008  8:15 PM
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sticksux - 2/1/2008  2:54 AM
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Propforce - 2/1/2008  2:59 AM
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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?
... and you think SpaceX is more successful than Delta IV?  :laugh:

No, I think SpaceX is much more cost-averse than Boeing -> it is more likely to pick more economical solution, by necessity.

If you want to compare apples to apples, compare Atlas V to Delta IV. Atlas is almost twice as cheap (!).

Offline Propforce

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Re: Delta IV Q&A
« Reply #264 on: 01/02/2008 10:57 pm »
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sticksux - 2/1/2008  2:52 PM

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Propforce - 2/1/2008  8:15 PM
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sticksux - 2/1/2008  2:54 AM
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Propforce - 2/1/2008  2:59 AM
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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?
... and you think SpaceX is more successful than Delta IV?  :laugh:

No, I think SpaceX is much more cost-averse than Boeing -> it is more likely to pick more economical solution, by necessity.


SpaceX launch failure rate is 100%, success rate is 0%.  


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If you want to compare apples to apples, compare Atlas V to Delta IV. Atlas is almost twice as cheap (!).

How did you arrive at that number?  Cost per lbm of payload?

Offline KSC Engineer

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Re: Delta IV Q&A
« Reply #265 on: 01/03/2008 12:26 am »
I hear you Propforce but I do hope Space X is successful long term as we can always use another launch option especially one that is funded by the private sector.   What I worry about with Space X  is if they don't get real lucky they will end up spending a lot more time and money than they plan to and being a private venture the money could dry up very quickly.  I hope Mr. Musk hangs in there because even though launching rockets looks easy the reality is our rocket technology today is layered with a lot of unknowns and probabilities.   But I understand what he is trying to do....better to be early to the party than late.

Offline TrueGrit

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Re: Delta IV Q&A
« Reply #266 on: 01/03/2008 04:14 am »
Just to correct something...  The complexity of LH2 systems, particularly on the ground, is overrated.  Yes you need vacuum jacketing, but vacuum jacketing is recommended for LOx systems in order to eliminate heat leak.  And in return for vacuum jacketing you eliminate the transfer pumps.  That's because unlike heavy LOx or RP lighter LH2 can be transfer via pressure alone...  Vaporizor, storage tank, lines, and flow control valve that's all.  And yes you need higher spec valves, but most LOx designs work fine at LH2 temps with little modification.  And in return there is no need to be concerned with storage vessel heaters in order assure your propellant doesn't get too cold during a freeze before a launch.  In all there's a favorable trade by eliminating the RP storage system completely, and increasing the size of the upperstage system.

Offline sticksux

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Re: Delta IV Q&A
« Reply #267 on: 01/03/2008 08:39 am »
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Propforce - 2/1/2008  11:57 PM
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sticksux - 2/1/2008  2:52 PM
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Propforce - 2/1/2008  8:15 PM
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sticksux - 2/1/2008  2:54 AM
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Propforce - 2/1/2008  2:59 AM
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?
... and you think SpaceX is more successful than Delta IV?  :laugh:
No, I think SpaceX is much more cost-averse than Boeing -> it is more likely to pick more economical solution, by necessity.
SpaceX launch failure rate is 100%, success rate is 0%.
You miss the point. I am saying than when company has no monetary backing from DOD, it *has to* pick the most economical solutions, not the high-tech fancy ones.

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If you want to compare apples to apples, compare Atlas V to Delta IV. Atlas is almost twice as cheap (!).
How did you arrive at that number?  Cost per lbm of payload?
Yes. It was mentioned on this forum. LV and Services Cost ($FY06M):
A 551 $180 - ~21 ton to LEO, 8.2 ton to GTO
D IVH $475 - ~25 ton to LEO, 10.8 ton to GTO

Offline sticksux

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Re: Delta IV Q&A
« Reply #268 on: 01/03/2008 08:43 am »
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TrueGrit - 3/1/2008  5:14 AM
Just to correct something...  The complexity of LH2 systems, particularly on the ground, is overrated.  Yes you need vacuum jacketing, but vacuum jacketing is recommended for LOx systems in order to eliminate heat leak.  And in return for vacuum jacketing you eliminate the transfer pumps.  That's because unlike heavy LOx or RP lighter LH2 can be transfer via pressure alone...

Why are you comparing LOX with LH? You should compare _kerosene_ with LH, since LOX is used in both cases anyway. No difference in LOX piping. The difference is in fuel piping.

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...is no need to be concerned with storage vessel heaters in order assure your propellant doesn't get too cold during a freeze before a launch.

Sure, you don't need heaters for LH. You need BIG FRIDGE instead, though, and need to run it all the time (say, even during launch delay), which has to be much more expensive. And what is done during month-long launch delay (like current Shuttle one)? I suppose they run cryo cooler all this time?

Offline sticksux

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Re: Delta IV Q&A
« Reply #269 on: 01/03/2008 10:11 am »
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Propforce - 2/1/2008  8:43 PM
LH2 first stage also has additional benefits.  First despite a "bulkier" first stage, the GTOW of vehicle is actually less than a RP first stage, so the booster engine require less thrust than a comparable RP engine.

This is true. You need bigger kerolox engine for the same LEO capability. For example, RD-180 has approx. ~1.25 higher thrust than RS-68, and therefore can be considered "equivalent".

We should always think in terms of $$$, not newtons, if we want to have affordable access to space. I am trying to estimate cost of US kerolox engine. Russians build and sell RD-170 for $7.5 million apiece to Ukrainians. They also build "half of RD-170" engine - RD-180 - for $10 million and sell it to ULA. So, it is already sold at approx x3 profit! RS-68 costs $14 million. I'd hazard to guess than American engine in RD-180 ballpark should cost no more than $25 million apiece.

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You can even afford to loss LH2 propellant with less insulations and still outperform a RP first stage.

I very much doubt you can have less insulation on your LH tank that on kerosene tank, as kerosene tank does not need any insulation!

Offline Jim

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Re: Delta IV Q&A
« Reply #270 on: 01/03/2008 10:41 am »
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sticksux - 3/1/2008  4:43 AM

Sure, you don't need heaters for LH. You need BIG FRIDGE instead, though, and need to run it all the time (say, even during launch delay), which has to be much more expensive. And what is done during month-long launch delay (like current Shuttle one)? I suppose they run cryo cooler all this time?

LH2 ground systems do not have refrigerant systems.  The insulation on the tanks keep the LH2 cold.  Only a little venting is required.

Cryotanks at the launch sites are not allowed to go dry.  They are replenished even during long stand downs (years)

Offline Jim

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Re: Delta IV Q&A
« Reply #271 on: 01/03/2008 10:43 am »
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sticksux - 3/1/2008  6:11 AM

I very much doubt you can have less insulation on your LH tank that on kerosene tank, as kerosene tank does not need any insulation!

Incorrect. Some vehicles require the RP-1 to be at certain temps

Offline sticksux

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Re: Delta IV Q&A
« Reply #272 on: 01/03/2008 11:35 am »
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Jim - 3/1/2008  11:41 AM
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sticksux - 3/1/2008  4:43 AM
Sure, you don't need heaters for LH. You need BIG FRIDGE instead, though, and need to run it all the time (say, even during launch delay), which has to be much more expensive. And what is done during month-long launch delay (like current Shuttle one)? I suppose they run cryo cooler all this time?
LH2 ground systems do not have refrigerant systems.  The insulation on the tanks keep the LH2 cold.  Only a little venting is required.
Cryotanks at the launch sites are not allowed to go dry.  They are replenished even during long stand downs (years)

Didn't know that. So, when/where LH is actually produced (where it becomes L - liquid?).

How much LH boils off in a month?

Offline sticksux

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Re: Delta IV Q&A
« Reply #273 on: 01/03/2008 11:40 am »
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Jim - 3/1/2008  11:43 AM
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sticksux - 3/1/2008  6:11 AM
I very much doubt you can have less insulation on your LH tank that on kerosene tank, as kerosene tank does not need any insulation!
Incorrect. Some vehicles require the RP-1 to be at certain temps

My main point still stands - LH tank needs more insulation, not less.

Heating/cooling kerosene is for squeezing last 0.3% of engine performance, right? Is it really worth the trouble - I mean - does it make $/kg to orbit lower?

Offline Jim

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Re: Delta IV Q&A
« Reply #274 on: 01/03/2008 11:45 am »
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sticksux - 3/1/2008  7:35 AM

Didn't know that. So, when/where LH is actually produced (where it becomes L - liquid?).

How much LH boils off in a month?

Louisana

Offline TrueGrit

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Re: Delta IV Q&A
« Reply #275 on: 01/03/2008 03:24 pm »
What I'm saying is that the cost for ground system cryo lines and valves is minor...  And technically LH2 is not that different than LOx.  The trade is in eliminating the RP system completely vs. enlarging the upperstage LH2 system that was already going to be there.  Buying and maintaining large, simple, common LH2 storage/transfer system vs. buying and maintaining a smaller LH2 storage/transfer system aswell as a more complex large RP system.

The trade isn't a clear cut as some of you like to make it out...  It's is actually a very close trade.  And that's why you don't see a clear cut winner...  Shuttle and Delta IV are LH2, while Atlas V and Russian systems are RP.  That big differnce maker for Delta IV was the high maturity of the Rocketdyne engine, which lowered development costs tremendously compared with starting with something fairly imature.

Anyone that's been around large scale LOx or LN2 stoarge will be familar with the liquid gas trucks that come and go during all times of the night and day...  Those same trucks also carry LH2 and LHe.  LH2 and LHe, just like LOx and LN2, are produced in a large plant that takes in gas, seperates it into it's respective components, and sells off the result in either gas or liquid form.  Look up Praxair and Air Liquide for more information...


Offline sticksux

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Re: Delta IV Q&A
« Reply #276 on: 01/03/2008 04:05 pm »
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TrueGrit - 3/1/2008  4:24 PM
maintaining large, simple, common LH2 storage/transfer system vs. buying and maintaining a smaller LH2 storage/transfer system aswell as a more complex large RP system.

I don't understand. RP system will be more complex than similarly-sized LH system? Why?

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And that's why you don't see a clear cut winner...  Shuttle and Delta IV are LH2, while Atlas V and Russian systems are RP.

I do see clear cut winners here, as soon as I recall $/kg for these vehicles.

Offline edkyle99

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Re: Delta IV Q&A
« Reply #277 on: 01/03/2008 08:05 pm »
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sticksux - 3/1/2008  3:39 AM

A 551 $180 - ~21 ton to LEO, 8.2 ton to GTO
D IVH $475 - ~25 ton to LEO, 10.8 ton to GTO

I'm not sure I believe that Atlas price/cost.  In fact, I'm almost certain that I don't believe it.  It probably costs almost that much per launch just for the facility maintenance contract.  Then again, I don't know if I believe the Delta number either.  

 - Ed Kyle

Offline WHAP

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Re: Delta IV Q&A
« Reply #278 on: 01/03/2008 08:23 pm »
$190M (not $180M) was the advertised (by NASA) value of the Juno contract.

http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=10071&posts=15&start=1

Believe but you will, but if you think ULA would sell a vehicle at a loss, you're mistaken.
ULA employee.  My opinions do not necessarily reflect those of my employer.

Offline Propforce

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Re: Delta IV Q&A
« Reply #279 on: 01/03/2008 08:54 pm »
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sticksux - 3/1/2008  1:39 AM

You miss the point. I am saying than when company has no monetary backing from DOD, it *has to* pick the most economical solutions, not the high-tech fancy ones.

Delta IV was built with 80% internally funded money.  

Cost is not a clear driver to discriminate between LH2 and RP first stage.


ps- you don't think SpaceX is building Falcon 9 with government funded money?



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