To be fair, it's pretty common for "mature" organizations to reach orbit on the first try. SpaceX had three Falcon 1 failures before their first success, and a few other startups have shown similar numbers. On the other hand, the first Falcon 9 reached orbit. More directly relevant, Shuttle was a success on its first launch (good thing, too, with a pair of astronauts flying!). On the third hand, the first Ariane 5 failed 37 seconds into flight, for reasons discussed on HN every so often.
I'd give SLS an 85% chance of reaching roughly the correct initial orbit, and only a small chance of leaving a smoking crater.
> Do they really expect this launch to go right the first time?
Yes, they really do. They want the second flight of this rocket ever to be crewed. That's obviously not going to happen if the first launch goes wrong.
I fully expect this launch to be flawless other than having, shall we say, a less than elegant design.
The companies who have put this together are very experienced at making launches successful.
The self congratulations do seem premature, but they are very good at blowing time and money budgets on disposable solutions that optimize for the maximum payroll per flight… absolute world class experts at what they do.
How many times did SpaceX blow up before getting a rocket into orbit?