SLS, SSMEs, reinventing the wheel, etc.
"Using shuttle main engines isn't exactly a bold leap forward - weren't they they ones that got cracked turbine blades that could easily have caused a Challenger type disaster if the SRBs hadn't got there first?"
I don't know about the cracked turbine blade issue, but iirc, the SSMEs have been far more reliable and less accident-prone (shall we say) than the SRBs. USAF experience with strap-on SRBs on the Titan III long before the Shuttle flew showed lots of problems with seals similar to the Shuttle SRB O-ring issue.
It makes perfect sense to me that on the new SLS heavy-lift vehicle, NASA is going with technology that's already proven and has a long filght history instead of trying to invent something new from zero... although I still wonder about how the new version of the Apollo-era J2 design will work for them; with all the advancements in engineering and materials science since the '60s, you can be pretty sure they aren't just going to pull the old J2 plans and build the engines as-is from the old '60s designs.
You also have to remember that a lot of what they're proposing for this new vehicle probably has its origins in the old "Shuttle-C" unmanned heavy-lift cargo launch system proposed in the late '80s:
"American orbital launch vehicle. NASA Marshall design for a cargo version of the shuttle system. The shuttle orbiter would be replaced by an unmanned recoverable main engine pod. The same concept was studied earlier as the Interim Heavy Lift Launch Vehicle (IHLLV) and as the Class I Shuttle Derived Vehicle (SDV). The Phase I two-SSME configuration would have a payload of 45,000 kg to low earth orbit. Design carried to an advanced phase in 1987-1990, but then abandoned when it was found the concept had no cost advantage over existing expenable launch vehicles..."
Granted, the new SLS heavy-lift vehicle doesn't exactly resemble the proposed Shuttle-C --
-- but there are many similarities, such as the first-stage core based on the Shuttle main tankage powered by SSMEs with solid strap-ons.
It's also interesting that along with reviving some elements of the old Shuttle-C proposal, the SLS vehicle also bears a striking resemblance to the old Saturn MLV-V proposed in the '60s, an uprated Saturn V with strap-on SRBs on the first stage.
As far as private industry being able to do space better... well, it's not like privately-run aerospace corporations are loaded with risk-averse leadership, or bean-counter types cutting corners and jeapordizing missions in order to save a couple of bucks... are they? Let's not forget North American's issues with workmanship, etc. on the Block I Apollo; when Gus Grissom hung a lemon from the hatch of an under-construction Block I CM after a visit to the NA plant, he wasn't just joking around.
What also worries me is that with all these different companies all going ahead with their own programs -- instead of proposing their systems to NASA under an RFP for a contract award to build a single design -- we're going to end up in a situation much like the xUSSR during the '50s and '60s: two or three companies -- or, in the xUSSR's case, design bureaus -- going ahead and building full-up launch systems and flight hardware, and suffering all the duplication of effort and duplication of cost overruns that went with it.
Still, I've got to admit I'm totally rooting for SpaceX, as it looks as if they've really got it going on with the Falcon launcher, and if they can get their manned version of Dragon together and get it certified, well, I sure as hell won't be complaining. Being an old '60s kid, I'm a die-hard NASA fan, but, still... what the hell, the more the merrier.