Author Topic: Why have Atlas 5 and Delta 4?  (Read 12390 times)

Offline Antares

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Re: Why have Atlas 5 and Delta 4?
« Reply #20 on: 03/29/2009 02:51 AM »
Plus the NASA flight rate is dropping due to the budget carved out for Constellation.  The effects of the coming changes to CxP on science missions are indeterminate, so even if money goes back into Science there will be a lull of at least 3 years.
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 Antares

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Re: Why have Atlas 5 and Delta 4?
« Reply #21 on: 03/29/2009 05:14 PM »
2010 = 2
2011 = 5
2012 = 3
2013 = 2
2014 = 5 at most

That's a lot less than the average of 5-6 per year that's been sustained for the last decade.  And basically none in the D-II class after 2011 (though a chicken and egg argument can be made).
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 edkyle99

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Re: Why have Atlas 5 and Delta 4?
« Reply #22 on: 03/29/2009 10:21 PM »
Quote
Another possibility would be to stack a Castor 30 (used on the Taurus II second stage) on a Delta IV CBC or Atlas V CCB, perhaps augmented by trim thrusters.  That would roughly replicate a Delta 7920H.  It suspect that would have a chance to cost less than a Delta II second stage.

While we're on the subject of Taurus II... would it possible/worth it to replace the Castor 30 on Taurus II with a Delta II upper stage? It would make the vehicle all liquid, but what would that do to the vehicle's performance?

It would suffer a substantial performance loss.  The Delta 2 second stage is only loaded with about 6 tonnes of propellant, compared with the 12.83 tonnes of propellant loaded onto the Castor 30 stage.  The AJ10-118K second stage engine has a 319.2 second specific impulse, but Castor 30 isn't terribly far behind at 294 seconds.  As an offset, Castor 30 produces nearly six times more thrust than AJ10-118K, reducing gravity losses.

My back of the envelope figuring, based on some of my own assumptions about the Taurus II first stage, says that replacing a Castor 30 with a Delta 2 second stage would cut Taurus II LEO performance from roughly 5 tonnes to something like 3.8 tonnes.

This example makes me wonder why ULA would consider using the Delta 2 second stage on an EELV when better performing non-liquid alternatives are available. 

 - Ed Kyle
« Last Edit: 03/29/2009 10:29 PM by edkyle99 »

Offline yinzer

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Re: Why have Atlas 5 and Delta 4?
« Reply #23 on: 03/29/2009 10:44 PM »
Quote
Another possibility would be to stack a Castor 30 (used on the Taurus II second stage) on a Delta IV CBC or Atlas V CCB, perhaps augmented by trim thrusters.  That would roughly replicate a Delta 7920H.  It suspect that would have a chance to cost less than a Delta II second stage.

While we're on the subject of Taurus II... would it possible/worth it to replace the Castor 30 on Taurus II with a Delta II upper stage? It would make the vehicle all liquid, but what would that do to the vehicle's performance?

It would suffer a substantial performance loss.  The Delta 2 second stage is only loaded with about 6 tonnes of propellant, compared with the 12.83 tonnes of propellant loaded onto the Castor 30 stage.  The AJ10-118K second stage engine has a 319.2 second specific impulse, but Castor 30 isn't terribly far behind at 294 seconds.  As an offset, Castor 30 produces nearly six times more thrust than AJ10-118K, reducing gravity losses.

My back of the envelope figuring, based on some of my own assumptions about the Taurus II first stage, says that replacing a Castor 30 with a Delta 2 second stage would cut Taurus II LEO performance from roughly 5 tonnes to something like 3.8 tonnes.

This example makes me wonder why ULA would consider using the Delta 2 second stage on an EELV when better performing non-liquid alternatives are available. 

The Castor 30 doesn't exist yet. When it does, it won't provide for multiple burns or precise orbital delivery.  Most payloads want one or both of those, so you might end up needing a third stage (like Orbital) and still suffering in terms of performance.

If a Delta II upper stage is available cheaper and sooner and gets the job done, why not use it?
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Offline edkyle99

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Re: Why have Atlas 5 and Delta 4?
« Reply #24 on: 03/30/2009 04:30 AM »
The Castor 30 doesn't exist yet. When it does, it won't provide for multiple burns or precise orbital delivery.  Most payloads want one or both of those, so you might end up needing a third stage (like Orbital) and still suffering in terms of performance.

If a Delta II upper stage is available cheaper and sooner and gets the job done, why not use it?

I don't think that a "Delta IV Small" as originally envisioned would replicate Delta 7900 series performance "as-is".  Boeing may have thought that the "Small" could make the mark during the mid 1990s when more optimistic performance was predicted for RS-68, etc, but it doesn't appear possible now.  The Delta II second stage would need to be stretched a bit, but that stretch would be limited by the second stage engine thrust.

On the other hand, a small trim stage ("post-boost" stage) would seem to be necessary for the higher-performance Castor 30.  Money would decide between the three available choices (the third being to use EELV Medium with unused payload capability.)

 - Ed Kyle     
« Last Edit: 03/30/2009 04:31 AM by edkyle99 »

Offline TrueGrit

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Re: Why have Atlas 5 and Delta 4?
« Reply #25 on: 03/30/2009 05:45 AM »
Yes the Delta IV has had some performance loss since the original Delta IV Small was dropped.  But there has also been a significant efort to claw back that performance.  And with the RS-68A soon to come on line I have little doubt a Delta IV Small would have equivelent performance as the 7920 Delta II.  A simple scaling of a 7920-H and Delta III seems to indicate this as well (yes I know this is not a very accurate method of comparing performance).

Delta II -> 1869kg to GTO and 4120kg to LEO (ref 1999)
Delta II-H -> 2030kg to GTO and 4475kg to LEO (ref 1999)
Delta III -> 3810kg to GTO and 8400kg to LEO (ref 1999)
Delta IV Small -> 2290kg to GTO and 4870 to LEO (DII/DIII 1999 scaling applied to DIV Med)
  - Compared to 2008 DII -> 1750kg to GTO and 4490kg to LEO
  - Compared to 2008 DII-H data -> 2120kg to GTO and 5340kg to LEO
Delta IV S+3,2 -> 3210kg to GTO and 6520kg to LEO (DIV Med/M+ scaling)
  - Notional intermediate to exceed DII-H LEO performance
Delta IV Medium -> 4300kg to GTO and 9150kg to LEO (ref 2008)
Delta IV M+4,2 -> 6030kg to GTO and 12240kg to LEO (ref 2008)

Secondly there is huge amount of knowledge on how the Delta II upper stage.  This welth of knowledge, simulation models, and procedural expereience is a huge advantage.  And so is the fact that the Avionics system is all ready to go with little to no modifications (replace Delta II boxes with nearly identical Delta IV boxes).  The Delta Avionics would for certain need to be requalified for use on a solid stage, with doubts it could last without a major redesign.

You do bring up the real question...  Is the better cost angle the existing Atlas and Delta Mediums (flying unused capability)?  Or can the Delta IV Small upper stage's signifcantly lower cost overcome it's developement costs (An RL-10 cost is more than the entire Delta II upper stage)?
« Last Edit: 03/30/2009 05:53 AM by TrueGrit »

Offline libs0n

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Re: Why have Atlas 5 and Delta 4?
« Reply #26 on: 03/30/2009 08:00 AM »
How does an Atlas 5 first stage compare with the Delta 4 first stage in this role?  It, barring other considerations that are beyond my grasp, would seem to be the favoured first stage option for the small given its reputed competitiveness, especially given the stiff competition it will face in the category.

I'd like to suggest a third second stage option to consider for the small: the Russian Block-D.  Feasibility of import and acceptance of a foreign stage would be matters to determine.  Who will buy these "Delta 2 class" launches in a post-Delta 2/Air Force supported Delta 2 world?  Just NASA?  Other government agencies like NOAA?  A few commercial launches maybe?  Maybe these customers wouldn't care about such a second stage.  They'll always have the option to buy the Centaur/the others if they do.

Offline Jim

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Re: Why have Atlas 5 and Delta 4?
« Reply #27 on: 03/30/2009 01:08 PM »
You do bring up the real question...  Is the better cost angle the existing Atlas and Delta Mediums (flying unused capability)?  Or can the Delta IV Small upper stage's signifcantly lower cost overcome it's developement costs (An RL-10 cost is more than the entire Delta II upper stage)?

There is also the DII second stage on the Atlas V CCB

Offline Jim

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Re: Why have Atlas 5 and Delta 4?
« Reply #28 on: 03/30/2009 01:10 PM »
Other government agencies like NOAA?

There are only 4 gov't agencies that buy launch services.  USAF, NRO, DARPA and NASA.   NOAA contracts NASA for spacecraft procurement and launch services

Offline Jim

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Re: Why have Atlas 5 and Delta 4?
« Reply #29 on: 03/30/2009 01:12 PM »

I'd like to suggest a third second stage option to consider for the small: the Russian Block-D. 

Not even an option.  Delta and Atlas guidance systems are in the upperstages

Offline libs0n

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Re: Why have Atlas 5 and Delta 4?
« Reply #30 on: 03/30/2009 09:41 PM »

I'd like to suggest a third second stage option to consider for the small: the Russian Block-D. 

Not even an option.  Delta and Atlas guidance systems are in the upperstages

This would also seem to apply to Mr. Kyle's nomination of the Castor 30 for this role.  In another related thread, he proposed an "avionics shelf" to be added to the stage for that function, which I presume to mean a guidance system.  Presumably, a Block DM could be similarly modified by ULA to include such a guidance system.  I also take it that the Delta 2 second stage would also need to undergo modification to include an appropriate guidance system if it is to use the Atlas V CCB.

Offline HIPAR

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Re: Why have Atlas 5 and Delta 4?
« Reply #31 on: 03/30/2009 09:56 PM »
Don't forget the Atlas relies on a Russian engine.  If you follow the news, there are many stories about events that are slowly increasing tensions between the US and Russia.

Some time ago, there was a discussion here about Pratt and Whitney concluding it's manufacturing analysis for the engine.  There was never a consensus that they actually manufactured one and test fired it.

---  CHAS

Offline bobthemonkey

Re: Why have Atlas 5 and Delta 4?
« Reply #32 on: 03/30/2009 10:26 PM »
There was never a complete engine produced from all US made parts, but the most complicated part (The name of which escapes me at this time), was made in the US, along with other critical parts.

Part 1 & 2 of the domestic co-production programme was completed. Stage 3 was the establishment of a factory and test stand. At the end of phase 2 there was the intellectual capacity to produce RD-180's in the US; it was the production capacity that was lacking. This can be competed without any additional input from Russia.
« Last Edit: 03/30/2009 10:55 PM by bobthemonkey »

Offline madscientist197

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Re: Why have Atlas 5 and Delta 4?
« Reply #33 on: 03/30/2009 11:05 PM »
Depends, of course, on how long it is until relations break down (not that I actually believe all the scaremongering). If it is in seven years time, then it might not be as easy as it is now.
John

Offline Capt. Nemo

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Re: Why have Atlas 5 and Delta 4?
« Reply #34 on: 04/12/2009 05:41 AM »
Would it be at all feasible to replace the RD-180 with an American engine like the RS-84? (I know it's never really been built and it would require a development program.) How hard would it be to integrate a new/different engine on a pre-existing rocket system like Atlas? Would it take more than simply 'lots and lots of money'? Would it be technically extremely difficult to pull of? Or is it just an idiotic idea?  :D
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Offline kevin-rf

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Re: Why have Atlas 5 and Delta 4?
« Reply #35 on: 04/12/2009 04:40 PM »
Would it be at all feasible to replace the RD-180 with an American engine like the RS-84? (I know it's never really been built and it would require a development program.) How hard would it be to integrate a new/different engine on a pre-existing rocket system like Atlas? Would it take more than simply 'lots and lots of money'? Would it be technically extremely difficult to pull of? Or is it just an incorrect idea?  :D

... cough ... Atlas III ... cough ...
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Offline edkyle99

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Re: Why have Atlas 5 and Delta 4?
« Reply #36 on: 04/13/2009 12:12 AM »
Would it be at all feasible to replace the RD-180 with an American engine like the RS-84? (I know it's never really been built and it would require a development program.) How hard would it be to integrate a new/different engine on a pre-existing rocket system like Atlas? Would it take more than simply 'lots and lots of money'? Would it be technically extremely difficult to pull of? Or is it just an incorrect idea?  :D

... cough ... Atlas III ... cough ...

Yes, it could be done, IF the money were released (and a lot of it), but the question is who would build it? 

Surely not Rocketdyne, the company that bowed out of the Altas III (then Atlas IIAR) competition rather than compete against RD-180 - a company that hasn't developed a kerosene rocket engine in decades - and hasn't even built one in several years. 

SpaceX?  Perhaps, but that would be a gamble given that the company has barely broken the 100Klb thrust barrier, only 1/9th what Atlas V would need.

Aerojet?  Only if another Russian engine is allowed.

 - Ed Kyle
« Last Edit: 04/13/2009 12:12 AM by edkyle99 »

Offline Antares

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Re: Why have Atlas 5 and Delta 4?
« Reply #37 on: 04/13/2009 03:55 AM »
This question has been asked and answered several times on here.  Seek and ye shall find.
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 Capt. Nemo

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Re: Why have Atlas 5 and Delta 4?
« Reply #38 on: 04/14/2009 04:46 AM »

Yes, it could be done, IF the money were released (and a lot of it), but the question is who would build it? 

Surely not Rocketdyne, the company that bowed out of the Altas III (then Atlas IIAR) competition rather than compete against RD-180 - a company that hasn't developed a kerosene rocket engine in decades - and hasn't even built one in several years. 

 - Ed Kyle

Ah, I see. Well thanks for the answer Ed. (So many bits of information I don't know. I'm learning though.)  ;D   
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