Author Topic: Atlas V and Centaur Q&A  (Read 217746 times)

Offline Antares

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Re: Atlas V and Centaur Q&A
« Reply #20 on: 02/05/2007 12:15 AM »
2 things that haven't been mentioned:

1) widening the body at a constant mass shortens the vehicle and gives a shorter engine moment arm for control.

2) I think a structurally stable second stage is less likely since second stage mass has such a high exchange rate with payload mass.
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Offline Kayla

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Re: Atlas V and Centaur Q&A
« Reply #21 on: 02/05/2007 12:32 AM »
Atlas V's 12.5' diameter was driven by the need to air lift the long booster tank.

From its inception WBC was freed of this limitation.  Originally the assumption was that the tank would be built at Michoud where three 5.4m demonstration hoops were assembled and lap welded together to demonstrate the planned construction using thin (0.080") al-li sheet stock.  With the formation of ULA, ULA now has the option of using either Michoud or Decatur for construction.  Either location has the ability to friction stir weld large diameter tanks and then ship the final structures to the Cape or Vandenberg.

WBC is designed to merge the extremely efficient monocoque, common bulkhead tank from the historic Centaur with modern materials and friction stir welding spear headed for space application by the external tank and Delta programs.  This combination, along with increased propellant load allows the WBC to increase the mass fraction from the current Centaur's 0.91 to 0.94!  The following paper provides additional information.
http://www.lockheedmartin.com/data/assets/12382.pdf

Offline bombay

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Re: Atlas V and Centaur Q&A
« Reply #22 on: 02/05/2007 04:02 AM »
Quote
Kayla - 4/2/2007  7:32 PM

Atlas V's 12.5' diameter was driven by the need to air lift the long booster tank.

Titan Centaur was 14' dia. and air lifted, though obviously not as long as the booster.

Offline bombay

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Re: Atlas V and Centaur Q&A
« Reply #23 on: 02/05/2007 04:24 AM »
On another thread, we briefly discussed what upperstage would be used in 2008 (maybe) for the GPSIIF satellites that are slated to fly on Atlas V or Delta IV as the transition from Delta II begins to occur (maybe).

Centaur was mentioned as the upperstage candidate for Atlas V for obvious reasons though it seems to me that it would be a very costly option.  What of the possibility of using the current Delta II 2nd and 3rd stages on Atlas V with a modified interstage adapter?  Is that being considered?  What am I missing in my thought process?    

Offline Jim

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Re: Atlas V and Centaur Q&A
« Reply #24 on: 02/05/2007 10:51 AM »
Quote
bombay - 5/2/2007  12:24 AM

On another thread, we briefly discussed what upperstage would be used in 2008 (maybe) for the GPSIIF satellites that are slated to fly on Atlas V or Delta IV as the transition from Delta II begins to occur (maybe).

Centaur was mentioned as the upperstage candidate for Atlas V for obvious reasons though it seems to me that it would be a very costly option.  What of the possibility of using the current Delta II 2nd and 3rd stages on Atlas V with a modified interstage adapter?  Is that being considered?  What am I missing in my thought process?    


The Delta-IV Small was to use a Delta II 2nd and 3rd stages.  The Atlas V Small was to use a updated version of the Agena upperstage.  
The EELV small versions were cancelled since they were only for GPS launches and the additional expense of having another version wasn't worth the extra cost.  So the GPS spacecraft were redesigned and had their AKM's "removed"  Now the EELV's put the GPS spacecraft directly into their operational orbits using the standard EELV upperstages (Centaur and D-IV 4m)  

A Delta II can not be used for a GPSIIF since there is no AKM.

Offline Launch Fan

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Re: Atlas V and Centaur Q&A
« Reply #25 on: 02/05/2007 04:47 PM »
Did a search on the net, but got a load of convolted stuff, so maybe a clear round up would be good.

When did Lockheed Martin start launches on the Atlas? It's history started when? What was it initial purpose?

Offline edkyle99

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Re: Atlas V and Centaur Q&A
« Reply #26 on: 02/05/2007 04:57 PM »
Quote
Launch Fan - 5/2/2007  11:47 AM

Did a search on the net, but got a load of convolted stuff, so maybe a clear round up would be good.

When did Lockheed Martin start launches on the Atlas? It's history started when? What was it initial purpose?

From:
http://www.lockheedmartin.com/wms/findPage.do?dsp=fec&ci=12912&rsbci=4&fti=0&ti=0&sc=400

"Lockheed Martin Corporation was formed in March 1995 with the merger of two of the world's premier technology companies, Lockheed Corporation and Martin Marietta Corporation."

Lockheed Martin developed Atlas V to be an orbital space launcher from its outset, in response to the U.S. Pentagon EELV program requirements.  The first Atlas V launch was in 2002.

Lockheed Martin assumed control of the legacy Atlas program in 1995, from Martin Marietta.  Martin Marietta had run the Atlas program only since 1993, when it acquired General Dynamics Space Systems.  General Dynamics had been the Atlas prime since its inception as an ICBM during the 1950s.

 - Ed Kyle




Offline yinzer

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Re: Atlas V and Centaur Q&A
« Reply #27 on: 02/05/2007 06:12 PM »
Quote
bombay - 4/2/2007  9:24 PM

On another thread, we briefly discussed what upperstage would be used in 2008 (maybe) for the GPSIIF satellites that are slated to fly on Atlas V or Delta IV as the transition from Delta II begins to occur (maybe).

Centaur was mentioned as the upperstage candidate for Atlas V for obvious reasons though it seems to me that it would be a very costly option.  What of the possibility of using the current Delta II 2nd and 3rd stages on Atlas V with a modified interstage adapter?  Is that being considered?  What am I missing in my thought process?    

You would have to compare the cost savings of producing one less Centaur (which will probably be much less than the average cost of a Centaur) to the additional cost of producing one more Delta II upper stage set (which will probably be fairly high since the Delta II will probably have been retired by then so you'd be paying for the whole production line).

Then you'd also have to pay for all of the development work to integrate the upper stage onto the launch vehicle - designing the interstages, making sure the upper stage could handle the loads, creating new control laws, integrating the Centaur avionics (which can control the Atlas) onto the Delta II upper stage, modifying the pad to allow fueling of the upper stage.  Over the five or ten Atlas GPS flights, this could wipe out most of the savings.

Which shouldn't come as a surprise, because the initial EELV plans included "Small" launchers, and someone went through exactly the same logic and figured out that it would be cheaper to just use the Mediums.

I am surprised that there hasn't been talk of dual-manifesting the GPS birds.
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Offline Jim

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Re: Atlas V and Centaur Q&A
« Reply #28 on: 02/05/2007 06:29 PM »

Offline yinzer

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Re: Atlas V and Centaur Q&A
« Reply #29 on: 02/05/2007 06:53 PM »
Sorry, I meant talk of flying two GPS birds on one rocket.
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Offline Jim

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Re: Atlas V and Centaur Q&A
« Reply #30 on: 02/05/2007 07:00 PM »
Quote
yinzer - 5/2/2007  2:53 PM

Sorry, I meant talk of flying two GPS birds on one rocket.

The constellation is already filled out.  Only replenishment spacecraft are now flying.  There are 6 different planes and seldom do 2 spacecraft die on a single plane at the same time.  There is no need for 2 spacecraft on one launch.  Would be "wasting" one spacecraft

Offline kevin-rf

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Re: Atlas V and Centaur Q&A
« Reply #31 on: 02/05/2007 07:20 PM »
So an Atlas 552 with Wide Body Centuar would deliver how much to GTO? GEO? Would it outperform the Delta IV heavy to GTO? (Not to start a Delta vs. Atlas fight or anything?)

I really wish they would publish those figures without muddying them with the Atlas V Heavy numbers.
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Offline Jim

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Re: Atlas V and Centaur Q&A
« Reply #32 on: 02/05/2007 07:44 PM »
Quote
kevin-rf - 5/2/2007  3:20 PM

So an Atlas 552 with Wide Body Centuar would deliver how much to GTO? GEO? Would it outperform the Delta IV heavy to GTO? (Not to start a Delta vs. Atlas fight or anything?)

I really wish they would publish those figures without muddying them with the Atlas V Heavy numbers.

http://www.lockheedmartin.com/data/assets/12461.pdf

Offline kevin-rf

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Re: Atlas V and Centaur Q&A
« Reply #33 on: 02/05/2007 08:28 PM »
Okay to GTO, Atlas 552 with WBC is 12.9 mT. Delta Heavy is 13.1 mT. Close but Delta Heavy still has a slight 200 kg edge.

So for GTO missions developing Atlas 552 WBC would make more sense than developing Atlas V Heavy which gunther lists as 12.6 mT to GTO.
(That is assuming five solids, a single common core, and a WBC costs less than three common core Atlas booster and a standard Centuar).

Thanks
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Offline edkyle99

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Re: Atlas V and Centaur Q&A
« Reply #34 on: 02/05/2007 08:52 PM »
Quote
kevin-rf - 5/2/2007  3:28 PM

Okay to GTO, Atlas 552 with WBC is 12.9 mT. Delta Heavy is 13.1 mT. Close but Delta Heavy still has a slight 200 kg edge.

According to the November 2002 User's Guide, Delta IV Heavy can only put 12.5 tonnes into GTO, and this to a GTO that is 1,800 meters per second from GEO (typical Cape Canaveral insertion).  It can only put 10.75 tonnes to a GTO that is 1,500 meters per second from GEO (the "industry standard" insertion orbit by Ariane from Kourou and Zenit 3SL from the equator).  

This Atlas brochure doesn't specify the GTO orbit inclination.  As a result, it isn't possible to compare it with the Delta IV Heavy numbers that I listed in the previous paragraph.

 - Ed Kyle

Offline meiza

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Re: Atlas V and Centaur Q&A
« Reply #35 on: 02/05/2007 08:58 PM »
Back to Q&A.
What is the Centaur like during transport and at integration and at the pad? Does the balloon tank design give headaches? Is it manpower intensive?

Offline Jim

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Re: Atlas V and Centaur Q&A
« Reply #36 on: 02/05/2007 09:09 PM »
Quote
meiza - 5/2/2007  4:58 PM

Back to Q&A.
What is the Centaur like during transport and at integration and at the pad? Does the balloon tank design give headaches? Is it manpower intensive?

The Centaur has to be kept "in stretch" or under pressure at all times.  It just means it has to be monitored.  Most of the pressure monitoring is automated (use to require a tech onsite at all times).  They have the procedures down and it is second nature to keep it from collapsing

Offline simonbp

Re: Atlas V and Centaur Q&A
« Reply #37 on: 02/05/2007 09:34 PM »
With ULA and the move to Decatur, will new tooling be built or the existing moved? Wouldn't this move be the best opportunity to build new tooling that could support a wider body Atlas V?

Simon ;)

Offline Kayla

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Re: Atlas V and Centaur Q&A
« Reply #38 on: 02/06/2007 12:39 AM »
Quote
simonbp - 5/2/2007  4:34 PM

With ULA and the move to Decatur, will new tooling be built or the existing moved? Wouldn't this move be the best opportunity to build new tooling that could support a wider body Atlas V?

Simon ;)

ULA is still working all of the consolidation trades.  It is likely however that Decatur's friction stir weld process will be used for the booster tanks, gaining significant weld strength.

Offline Kayla

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Re: Atlas V and Centaur Q&A
« Reply #39 on: 02/06/2007 12:48 AM »
Quote
Antares - 4/2/2007  7:15 PM

2 things that haven't been mentioned:

1) widening the body at a constant mass shortens the vehicle and gives a shorter engine moment arm for control.

2) I think a structurally stable second stage is less likely since second stage mass has such a high exchange rate with payload mass.

The 1.5X WBC (150% of current Centaur's propellant mass, or ~70 klb) is substantially shorter than the existing Centaur.  Vehicle control, even with engine out on the multi-engine variants, has been studied in detail and can be satisfied with the existing EMA thrust vector control system.  The 3.5X (~160 klb propellant mass) version is slightly longer than the current Centaur.

The WBC is designed to be structurally stable during manufacture.  To maintain, actually improve, the mass fraction the stage will rely on pressure during flight (even the ET requires pressure during flight).

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