Well, my first question is - what does “not have the grads to be successful in an engineering program” mean? Is he in high school still? Obviously you don’t want to steer him into anything he’ll struggle in, but if he’s pretty good in math and science, really loves doing it, and just tends to get more Bs than As…that’s fine, too.
But actually I’d wager that many jobs supporting space exploration aren’t necessarily engineering. They’re probably mostly science, but as Twoin18 mentioned, a lot of those are non-engineering science positions like atmospheric science/meteorology, earth sciences/geosciences, physics and astrophysics, chemistry, etc. (A lot of those scientist positions are going to require at least a master’s, if not a PhD, though.)
But looking at the USAJOBS listings for NASA, I also see other areas there - attorney, public affairs specialist, several program specialists (they provide administrative support). I also checked out SpaceX and they hire people like environmental specialists/scientists, finance (somebody’s gotta do payroll!), information security, legal and government affairs, software development, and logistics and supply chain management.
Also, to Twoin18’s excellent point about the NewSpace bubble, I would highly encourage a career path/major that can be widely applicable to many fields. Space science and exploration is (as far as I know) heavily dependent on federal government funding, and that expands and contracts with different administrations. There are some private companies of course doing the work, too, but they make an excellent point about the lack of profitability and good business plans (one of the reasons space science was done almost exclusively by the government for so long is that it’s tremendously expensive for very little immediate financial benefit. It’s not like we’re pretty close to sending people to Mars for vacations or something).
Meteorology and atmospheric science can be used across SO many different businesses. I peeked into this major area before going in a completely different direction, but lots of people hire them - news and weather forecasting companies, of course, but also airlines, investment banks (for commodities trading!), food science/agriculture operations, environmental science/sustainability firms, etc.