3-part interview with a phone screen, on-site panel interview, and then HR call. Generally they were all conversational; mostly consisted of reading through resume/CV and asking questions about it. Fairly straightforward interview process.

I applied for a junior level signal processing position around summer of 2017. I had a phone interview shortly after applying that went well enough to garner an in person interview ~2 weeks later. Onsite I met with 5 or 6 engineers of varied experience levels, everyone was friendly enough. The company vibe is definitely "Small New England Defense Contractor", it seems to have the kind of work atmosphere you'd get at MIT LL/MITRE/"golden days" BBN, and it seems a lot of the senior employees and management used to work at those places. I had traveled from out of state to interview and they didn't offer travel/lodging accommodations so I drove and stayed with a friend. After interviewing, I emailed HR and the manager I met with thanking them for bringing me in. I reached out a little over 2 weeks later since I hadn't heard anything back at that point. A month later, still having heard nothing, I reached out again and was finally met with a short email from HR that I was not a good match at that time. All good, looking back I think I wasn't a great fit for that specific role. However, the total lack of communication until I had reached out several times left a bad taste in my mouth. At a company this small, not contacting candidates you bring onsite (esp. without offering travel reimbursements) in ANY way within ~2-3 weeks gives off an appearance that you don't really respect the candidate's time. I don't think it's unreasonable to expect that kind of turnaround, regardless of whether or not they're sending an offer - I work at a similar company now and we have no problem getting back to candidates within a week or two. Hopefully that doesn't happen often!