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#20
by
simonbp
on 14 Apr, 2014 23:02
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#21
by
edkyle99
on 15 Apr, 2014 01:56
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Larger upperstage
Interesting. That was my guess, but only a guess.
So what sort of new upper stage would it likely be? I'm assuming they can't or won't just adapt a 5m DCSS to fit on Atlas? Would it be something like ACES? Or more like a scaled up Centaur with larger balloon tanks? Would it use RL-10's or switch to like an RL-60 or something?
The ACES plan, or something like it, seems most likely to me. That is essentially a "Fat Centaur" powered by multiple RL10C engines (or equivalent) that starts with 40-ish tonnes of propellant and can grow to 70 tonnes or more. The stage would be designed to serve on Delta 4 as well, creating a true common stage in a move to cut costs.
Looking back at the growth of Atlas Centaur and Thor-Delta over the years shows incremental improvements in lower and upper stages, usually in differential steps. Thus, the next step after "Fat Centaur" is likely improved solid boosters. Eventually a "Fatter Atlas 5" might occur, but not for many years.
- Ed Kyle
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#22
by
kevin-rf
on 15 Apr, 2014 12:21
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Looking back at the growth of Atlas Centaur and Thor-Delta over the years shows incremental improvements in lower and upper stages, usually in differential steps. Thus, the next step after "Fat Centaur" is likely improved solid boosters. Eventually a "Fatter Atlas 5" might occur, but not for many years.
- Ed Kyle
Not to argue, but:
1. The solid's on Atlas are already quite large. Much larger than the ones on Delta IV. They spent quite a bit of money developing and tailoring them to Atlas.
3. I assume a Fat Atlas requires two RD-180's. Meaning pad changes?
Like you and Jim said, the low hanging fruit is Centaur. There have been several proposals in the past for a Wide Body Centaur / ACES. A larger Centaur will hold more LH/LOX and be able to push more mass to high energy orbits, while a multi RL-10 Centaur would improve the TWR and be able to push more to LEO.
If I remember correctly, the original ACES proposal not only had room for between 1 and 6 RL-10's but variable length LH/LOX tanks. It could be optimized for HEO (1 RL-10, long tank), LEO (Multiple RL-10 reducing gravity losses) and large Heavy Boosters (Long Tank, multiple RL-10's).
I think the next low hanging fruit after a larger tank is an RL-10 replacement. The ACES proposal highlights the need for higher thrust in some applications. ULA has also been making noise about the RL-10 costs. I think if they can get a lower cost RL-10 replacement that has higher thrust. I can not see why they will not move to it before moving to improved solids or Fat Atlas.
The other low hanging fruit is a common Atlas/Delta IV upper stage.
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#23
by
Lobo
on 16 Apr, 2014 00:27
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Larger upperstage
Interesting. That was my guess, but only a guess.
So what sort of new upper stage would it likely be? I'm assuming they can't or won't just adapt a 5m DCSS to fit on Atlas? Would it be something like ACES? Or more like a scaled up Centaur with larger balloon tanks? Would it use RL-10's or switch to like an RL-60 or something?
The ACES plan, or something like it, seems most likely to me. That is essentially a "Fat Centaur" powered by multiple RL10C engines (or equivalent) that starts with 40-ish tonnes of propellant and can grow to 70 tonnes or more. The stage would be designed to serve on Delta 4 as well, creating a true common stage in a move to cut costs.
Looking back at the growth of Atlas Centaur and Thor-Delta over the years shows incremental improvements in lower and upper stages, usually in differential steps. Thus, the next step after "Fat Centaur" is likely improved solid boosters. Eventually a "Fatter Atlas 5" might occur, but not for many years.
- Ed Kyle
Assuming a "Fatter Atlas 5" would be a 5m core with two engines, wouldn't that be more likely to be the next upgrade after Fat Centaur? Given that ULA has the 5m core tooling necessary already? (be different if they didn't). That would do away with the SRB's altogether for most/all launches, seemingly simplifying things.
Or would upgraded SRB's be a cheaper upgrade than a wider core with extra engine?
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#24
by
kevin-rf
on 16 Apr, 2014 01:43
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Two engines, and you double the cost of the first stage engines. That is not a small chunk of change.
Considering 26 of 46 Atlas launches to date are v401/v501 configurations without solids. Do you need the large boost in performance a fatter Atlas with two RD-280's would provide? Is an extra RD-180 cheaper than a the solids it replaces?
A more capable Centaur (Wide Body/ACES) would reduce the number of solids needed, reducing costs and pushing more missions to the v401/v501 platform. A cheaper better higher thrust RL-10 replacement would have a similar effect.
This is especially true if you can move the v411/v421/v511/v521 missions, 8 to date, to the v401/v501. That would account for 34 of the 46 flown missions.
Again, I will state Lockheed spent a good chunk of change sizing and developing solids so they would have dial a rocket. What would a more powerful solid buy you? Other than a small handful of payloads that fly on the Delta IV heavy, Atlas can currently launch everything. Do you really need bigger solids. ACES only makes sense if it costs less than the Centaur and incremental solids it replaces. Bigger solids will reduce ULA's dial a rocket's flexibility.
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#25
by
baldusi
on 16 Apr, 2014 01:56
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ACES would be a Common Stage. Not only increases base performance, but significantly lowers cost overall. Plus Common Avionics and a lot of work can be done to unify Mission Control, for example.
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#26
by
Jim
on 16 Apr, 2014 02:24
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ACES would be a Common Stage. Not only increases base performance, but significantly lowers cost overall. Plus Common Avionics and a lot of work can be done to unify Mission Control, for example.
Launch control, there is no mission control ;-)
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#27
by
edkyle99
on 16 Apr, 2014 03:36
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Not to argue, but:
1. The solid's on Atlas are already quite large. Much larger than the ones on Delta IV. They spent quite a bit of money developing and tailoring them to Atlas.
True, and I'm sure that ULA wants to fly the existing motors for years. But that doesn't mean that they can't eventually be upgraded - just like Thor-Delta's boosters were incrementally upgraded over four decades. When the Atlas 5 boosters were developed, they were among the world's largest monolithic solid rocket motors (second to Castor 120, I think). They have since been surpassed, by both JAXA's SRB-A and by Vega's P80FW - and even bigger monolithic motors are on the drawing board.
3. I assume a Fat Atlas requires two RD-180's. Meaning pad changes?
I think that the basic platform could still be used, but some mods might be needed. But, again, this particular change wouldn't be needed for many years, or even decades.
- Ed Kyle
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#28
by
Lobo
on 16 Apr, 2014 16:49
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Agreed.
I was mainly wondering if Atlas V could be made to cover D4H's capability if there were reason at some point in the future to for ULA to want to down select to just one LV, without too much change to Atlas. It actually does sound like Atlas 55x with fat Centaur would be pretty close to covering it.
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#29
by
Lobo
on 16 Apr, 2014 16:49
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Out of curiosity, why does the current Centaur on Atlas not use the better performing RL-10B-2? Is it just that the Atlas interstage is too narrow for the RL-10B-2's nozzle extension? I'd always assumed that but, I'm wondering if that's correct, or if there's another reason, like the RL-10B-2 has a different design for the DCSS vs. RL-10A-4-2 for Centaur?
Seems like going to the RL-10B-2 would not only have given more synergy between the two LV's, but give Atlas a bump in performance.
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#30
by
kevin-rf
on 16 Apr, 2014 17:23
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Maybe because the RL-10B-2 was designed for the Boeing Delta III/IV programs, and Centaur already existed?
What ever happened to ULA modifying some of the excess RL-10B-2 inventory to work on Centaur? At one point ULA had a plan.
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#31
by
Jim
on 16 Apr, 2014 19:08
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Out of curiosity, why does the current Centaur on Atlas not use the better performing RL-10B-2? Is it just that the Atlas interstage is too narrow for the RL-10B-2's nozzle extension? I'd always assumed that but, I'm wondering if that's correct, or if there's another reason, like the RL-10B-2 has a different design for the DCSS vs. RL-10A-4-2 for Centaur?
Seems like going to the RL-10B-2 would not only have given more synergy between the two LV's, but give Atlas a bump in performance.
Doesn't fit in the Atlas interstage
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#32
by
Jim
on 16 Apr, 2014 19:09
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Maybe because the RL-10B-2 was designed for the Boeing Delta III/IV programs, and Centaur already existed?
What ever happened to ULA modifying some of the excess RL-10B-2 inventory to work on Centaur? At one point ULA had a plan.
ULA is going to the RL-10C-1 for Atlas and RL-10C-2 for Delta
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#33
by
Lobo
on 17 Apr, 2014 15:57
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Maybe because the RL-10B-2 was designed for the Boeing Delta III/IV programs, and Centaur already existed?
I think the RL-10B-2 flew in 1998 on Delta III, before the RL-10A-4-1 in 2000 and RL-10A-4-2 in 2002. Centaur was flying RL-10A-4 at that time in the "Centaur-T" configuration on Titan IV, and another dual engine version on Atlas II, If I understand the timeline correctly. After that was the current Centaur (Called "Centaur 3" I think?) flying on Atlas III and Atlas V, which changed from the RL-10A-4 to the 4-1 and 4-2.
So time wise, I think it was available to be used on the current Atlas V Centaur, and had more thrust and more ISP. But didn't know if it was a matter if it having different interfaces for the DCSS and couldn't be adapted for Centaur? Or just a matter of lack of width in the Atlas V interstage for that big nozzle extension.
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#34
by
Lobo
on 17 Apr, 2014 16:00
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Out of curiosity, why does the current Centaur on Atlas not use the better performing RL-10B-2? Is it just that the Atlas interstage is too narrow for the RL-10B-2's nozzle extension? I'd always assumed that but, I'm wondering if that's correct, or if there's another reason, like the RL-10B-2 has a different design for the DCSS vs. RL-10A-4-2 for Centaur?
Seems like going to the RL-10B-2 would not only have given more synergy between the two LV's, but give Atlas a bump in performance.
Doesn't fit in the Atlas interstage
Ahhh, ok, thanks for the clarification.
I'm assuming it would have been more costly to have modified the Atlas V interstage area to fit the RL-10B-2, than the performance increase it would have given? So not worth the investment of doing that, so they keep flying the A's?
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#35
by
Jim
on 17 Apr, 2014 16:25
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I'm assuming it would have been more costly to have modified the Atlas V interstage area to fit the RL-10B-2, than the performance increase it would have given? So not worth the investment of doing that, so they keep flying the A's?
Also different mixture ratio.
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#36
by
vapour_nudge
on 26 Apr, 2014 06:07
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Hi, I've been following the US space industry sine Atlas E days (doesn't mean I know anything) and I seem to recall in the early to mid 2000s that it was stated the Atlas V 551 could actually launch more payload to orbit with the current engine/booster combination but there is a limitation imposed by the vehicle's structure where it just can't handle anything heavier.
Can someone confirm or discount this?
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#37
by
Jim
on 26 Apr, 2014 12:45
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Hi, I've been following the US space industry sine Atlas E days (doesn't mean I know anything) and I seem to recall in the early to mid 2000s that it was stated the Atlas V 551 could actually launch more payload to orbit with the current engine/booster combination but there is a limitation imposed by the vehicle's structure where it just can't handle anything heavier.
Can someone confirm or discount this?
There is a structural limit for stock Centaurs and it only applies to LEO missions where the capability is high. If Atlas were to do such a mission, different tank skin would be needed and I think the forward adapter would have to be beefedup.
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#38
by
Lobo
on 05 May, 2014 23:59
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Hi, I've been following the US space industry sine Atlas E days (doesn't mean I know anything) and I seem to recall in the early to mid 2000s that it was stated the Atlas V 551 could actually launch more payload to orbit with the current engine/booster combination but there is a limitation imposed by the vehicle's structure where it just can't handle anything heavier.
Can someone confirm or discount this?
There is a structural limit for stock Centaurs and it only applies to LEO missions where the capability is high. If Atlas were to do such a mission, different tank skin would be needed and I think the forward adapter would have to be beefedup.
Would a new 5m upper stage be designed from the start for maximum (Atlas-55x) LEO payload mass, just in case it's ever used for that purpose? Or woudl it be made lighter in anticipation it's typical BLEO payloads?
Also, would an Atlas with a 5m upper stage use the Delta IV 5m PLF, and just have it sit on top as it does on Delta? Or would it use a new Atlas 5.1m PLF and encapsulate the upper stage as it does now for teh 5xx variants?
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#39
by
Lobo
on 06 May, 2014 00:13
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Jim,
Based on some of the posts on this thread, if one were to approximate the Likely Atlas Phase 1 performance at rougly 25-26mt to LEO, and 12-13mt to GTO, would one be in the ballpark?