Wow, @boneh3ad, quite a strong response. You certainly did turn my advice around in a way that was not intended, and re-interpreted my words in unflattering ways.
I see I did not complete my thought: MIT has 3 relevant departments to the OP- Aero/Astro, Ocean Engineering, and Mechanical Engineering. As the OP comes closer to figuring out what to do, he needs to narrow down his interest. As admissions is handled by the department, not MIT as a school (MIT for example, other schools will be similar- I said often, since there may be a school I don’t know of that handles graduate admissions a different way), he will need to decide on which department.
IF it is in Ocean Engineering, working for a spin-off company such as Bluefin (if I have the name right) will give industrial experience that is heavily collaborative with the MIT labs. This can be very helpful, if the OP decides he wants to work in this field, as the time approaches. So, if he decides he wants to work in ocean engineering developing new undersea vehicles, working for a company started by an MIT professor or student that acts as a de facto extension of an MIT lab is certainly a great option.
I assume the OP will first refine his interests, as he stated in his posting. If he is more interested in Aeronautical engineering or in other aspects of Mechanical engineering, and his interests align with the vast and broad scope of Lincoln Labs or inertial navigation interests at Draper, working at one of these places will give contact with MIT-affiliated researchers, (as would working at GTRI if he were targeting Georgia Tech). I detailed this example so as not to seem to be recommending interning at some random company just because they are affiliated (e.g. Northrop-Grumman), but to target academic positions as well as companies that have SPECIFIC spin-out close working ties with the target institution.
The OP stated he had an interest in doing PhD work at MIT, perhaps regardless of whether or not they are considered the best place to study his particular aspect of Mechanical, Ocean, or Aerospace engineering. I am assuming 1) it is difficult to gain admittance to MIT as a grad student (and recommendations from affiliated staff/faculty can speak to his fit and ability to do the work), and 2) he will refine his interests and is looking for what to do as he travels down this refined-interest road. I am taking him at his word that MIT is his preferred target school; and then simply using it as an EXAMPLE. That is why I said “e.g.”
I stand by my advice to refine the target, and then try to intern as close to your target as possible- both the purely academic options as well as looking at affiliated spin-out companies.
Do you REALLY disagree that he should focus down his interest, then focus on his primary target program? Would you rather that he randomly intern in some academic lab?
I would NEVER say to target a brand name institution for graduate school:
Also, working at a company that acts as an extension of an academic laboratory- with VERY close ties- often involves greatly shortened timelines, and increased scope of responsibility than interning in an academic lab; resulting in increased experience with the same “upsides” of working in R&D with a university professor. It is absolutely worth putting into the hat as an option to consider.