Of course the Executive and Legislative branches set the national vision and objectives, along with providing funding -- that makes sense to me. But what exactly is the rationale behind mandating that things be done a particular way, rather than trusting the engineers to achieve the task as safely, quickly, and inexpensively as possible?
Is it simply a matter of protecting the interests of the Congressional districts (job sureity), or is there another reasoning behind it? Have things always been this way? Do they mandate more than just things like SLS or is that a special situation, with NASA generally having authority over how things are done? What would the landscape look like if NASA had the freedom and flexibility to operate in a mission (and results) oriented fashion rather than constrained to policies set by non-engineers? To be agile enough to indifferently cut things that simply aren't working and pursue promising avenues to accomplish the task to the best of their abilities?
Consider Apollo. The politicians clearly defined the objective -- landing a man on the moon and returning him safely to the earth by the end of the decade -- and then left the engineers to choose the best technical means of achieving it. They argued extensively, and you can read all about Apollo's famous "mode debate." The engineers selected lunar-orbit rendezvous (LOR) in July of 1962. That decision was reviewed by the White House later in the year, and could conceivably have been overturned. In particular, presidential science advisor Jerome Wiesner and one of his staffers, Nick Golovin, were skeptical of LOR. In then end, though, NASA's decision held.
The Constellation program halfway followed the Apollo template, in that the Exploration Systems Architecture Study (ESAS) was an engineering justification for the 1.5-launch architecture that was to have been employed. I say "halfway," because the Study was widely criticized for its assumptions (e.g., a high failure rate for automated rendezvous and docking, and the convoluted assertion that large solid boosters are safe for crew launch but small ones are not). But at least there was an attempt to let engineers define the technical solution to a problem set by politicians. A key difference between Apollo's mode debate and ESAS is that the former really was a debate, with analyses performed by many different parties, whereas ESAS was a single report, making it much easier to manipulate.
With Orion/SLS, it's all gone completely bass ackward, with the politicians specifying the hardware but only vaguely defining the goal. It's not completely illegitimate that the politicians would have a say in the hardware solution, because there could be national concerns beyond the engineers' purview. In the case of SLS, for example, circa 2010 or 2011 we briefly heard about the Global Precision Strike System, which was to be an ICBM armed with a penetrating non-nuclear warhead (though I suspected at the time that the whole point of this proposal was to justify a need for keeping large solid rocket motors in production).
Does the head of NASA have the kind of authority to executive decisions on the direction projects are going in, or does he or she simply serve as a liaison between NASA and Congress, having responsibility with no real authority?
The head of NASA works for the president, who is supposed to follow the law laid down by Congress. There's not a lot of wiggle room there. Except when Congress feels like granting it, which it sometimes does. SLS as now conceived actually violates the law (there's no 70-tonne LEO version; the target 2016 date for initial operational capability [which would have required flights in 2015 or earlier] has been completely thrown out the window; even with EUS, the current SLS won't be able to orbit 130 tonnes).
I've heard people say NASA shouldn't be in the rocket making business, but what exactly do they mean by that? SLS is being made by ULA which is a private company I thought, not an internal NASA project, and even if Congress didn't mandate SLS development it seems entirely reasonable for NASA to set specifications based on their needs and contract out to private companies that can compete for the project.
The key distinction here is whether NASA should buy launch
vehicles, which it then operates itself, or buy launch
services. NASA's human-spaceflight program excepted, for decades now the US government has been buying launch services rather than launch vehicles.
Why does ULA seem to be struggling when companies like SpaceX appear to be making revolutionary leaps at a fraction of the time and cost?
Though ULA is a relatively new company, its owners, Boeing and Lockheed Martin, are old-time cost-plus contractors. They have many decades' experience making money by selling to a very wealthy and very risk-averse customer, namely the US military. ULA's product line is therefore high-cost and low-risk. There are certainly people at ULA who would like to move in a different direction, but ULA's owners aren't likely to allow much of that. That's a perfectly reasonable corporate strategy. They exist, after all, principally to make money for their shareholders. That it may not be the best thing for space or for the USA as a whole is not their concern.
Anyway these are just things that nobody seems to be talking about and I honestly don't think the majority of people even know. So frustrations and lashing out at NASA over cost overruns and delays when Congress is forcing them to do it and ULA is the one struggling while NASA has it's arms tied and doesn't seem to have any say over it's own direction, it seems to me the criticism towards them isn't fair. I feel like people may be a little more forgiving to Bridenstine if he was more vocal that he doesn't have a choice in a lot of this...
I agree that NASA's hands are often tied, but NASA also can be part of the problem. It seems to me that human institutions are a form of life, in that they inevitably adopt their own survival as a primary goal. There are parts of NASA that want to get the organization out of the rocket business and other parts, specifically the rocket parts, that very much want to stay in that business. The senators who wrote SLS's specs into law got those specs from somewhere.
I sympathize with Bridenstine. I'm sure he's smart enough not to believe everything he has to say. But I don't think it's viable for him to go around emphasizing that he doesn't have much of a choice in what he does. His job is largely to implement a plan chosen by others. Among other things, that means being the cheerleader-in-chief for the The Official Program.