I was reading an article about the 2 of the 3 cores arriving by barge from Decatur at CCAFS and it noted that the two would be the Starboard and center cores.

This made me wonder what differences in the core stages might exist. That is, do they build the three cores differently for a Delta 4 Heavy launch?

I know one of the critiques for the Delta 4 performance wise is that the mount points for the solid rocket boosters apparently are heavy, and are there on every launch, even those not using it. Somehow Atlas V differs in its mounting of solid boosters that does not carry a similar penalty.

So does the center core require additional structure to attach a core to either side, or is it already built into all the common core boosters?

My ultimate question that I am looking to get answered is: Are the CBC modules in a three core Delta 4 Heavy interchangeable?

  • $\begingroup$ Simple answer: the starboard/port cores (let alone center core) can't be identical because the fueling umbilical attaches to the same side when they're mated together and the core-core attachments must be on the opposite side. $\endgroup$
    – Nick T
    Commented Feb 12, 2016 at 22:44

1 Answer 1


No, it does not seem that the 3 different CBC's are interchangeable. The Common Booster Core employs separate spherical bulkheads on the LH2 and LOX tanks. The tanks employ internal stringers for additional stability and the LOX tanks use anti-slosh baffles. An external wiring tunnel runs down the length of the entire booster whereas some of these components of the stap on common booster cores.

These are subtle differences that could more than likely easily be altered to make them interchangeable although some components would have to be added (such as the external wiring, etc).

Here is some more info:


Of course some of these components they all share in common but the wiring I think is the big thing. And the need for booster separation.

  • $\begingroup$ That is interesting details, but in now way addresses the question. The question is, are the CBC modules in a three core Delta 4 Heavy interchangeable? $\endgroup$
    – geoffc
    Commented Mar 26, 2015 at 16:25
  • $\begingroup$ Well, as I was reading your question it said "That is, do they build the three cores differently for a Delta 4 Heavy launch?" -I addressed that question. My links explained what differences in the core stages exist. As well as some of the other things in the rest of the question. Never in the question did it directly say "Are the CBC modules in a three core Delta 4 Heavy interchangeable?. $\endgroup$
    – Kleigh
    Commented Mar 26, 2015 at 17:00
  • $\begingroup$ Hehe. Look at the actual title of the question. So are the two side CBC's identical? Or is the core different from the two side boosters? $\endgroup$
    – geoffc
    Commented Mar 26, 2015 at 17:06
  • $\begingroup$ Sorry, Missed the title there. I do believe that there are subtle differences that keep them from being interchangable although I think if they wanted to they could very easily interchange them with a few small alterations. Would you allow me to post my corrected answer? I believe I can answer that question for you. $\endgroup$
    – Kleigh
    Commented Mar 26, 2015 at 18:17
  • 1
    $\begingroup$ Go for it! :) That is the point. Fix your answer, delete and do a new one,. Whatever. Get the best answer out there. $\endgroup$
    – geoffc
    Commented Mar 26, 2015 at 18:24

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