J-2

That immediately morphed into a 5 segment SRM and upgraded J-2 with the associated Billions of dollars in development costs.

Augustine Committee Meets at MSFC Today - NASA Watch 2009

ESAS said off-the-shelf 4 segment SRM and J-2 would meet requirements.

Augustine Committee Meets at MSFC Today - NASA Watch 2009

At least with this Constellation business we might get to see the J-2 revived.

NASA Leadership Vacuum - NASA Watch 2009

I believe this is backwards -- it has always been my understanding that Ares requires far more upfront money and development time, compared with Direct since (in part) Direct uses the existing 4 segment SRB and the J-120/J-130 will not need to wait for (or pay for) the J-2 upper stage engine.

Proponents of DIRECT Offer Rebuttal to NASA's Analysis - NASA Watch 2009

Ditto with the 2nd stage, where a single J-2 would be a better engine choice than two or more RL-10s.

Delta IV Heavy is Cheaper Than Ares 1. Wow. Who Knew. - NASA Watch 2009

I can go either way on Ares 1, but as for Ares 5 it's the only real project we have and it already uses well proven technology ... similar SRBs to the Shuttle, same 1st stage engines as Delta IV, a very realiable and tested J-2 engine for the upper stage, and a standard two stage + solid boosters configuration without the Ares 1 complexities or asymmetric concepts like Shuttle-C.

Reader's Consensus: Develop a new launch vehicle - NASA Watch 2009

In any case EELV is an excellent launcher for the DoD and certain government missions, I think Falcon 9 will be a great commercial success, and strongly believe we need to see Ares-1 as a step towards developing the technologies for Ares-5 (solid rocket boosters, improved J-2 engine, Ares 5 upper stage, etc.).

Gration's Chances Fade Away - NASA Watch 2009

Note that this design "upgrade" (the 2nd stage got a fifth J-2 as well) was executed in late 1961/early 1962, before the Apollo LOR mode decision was final.

First Briefing on Human Space Flight Review - NASA Watch 2009

Much of the Ares-1 technology (J-2 engine, SRM, etc.) was being developed with the Ares-5 in mind, so with that gone so will the supplier chain just barely being established.

Major General Jonathan Scott Gration Emerges as Possible Obama Choice for NASA Administrator - NASA Watch 2009

For the latest information on the security situation in Iraq, contact DIA J-2.

David Isenberg: The GAO Transcripts, Part 15: Coordination is Easier Said Than Done 2010