I am a first-year graduate student in mechanical engineering. For most of the fellowships I want to apply, such as the NSF fellowship for graduate students, they all require 3 letters of recommendation.
My problem is I only have one research advisor who knows me very well but even with this advisor we haven't produced any meaningful work yet. Also, during my undergrad, I've only done one summer research a long time ago at a very large lab and I never got to meet the PI while in the lab. I don't think he even remembers me now.
To sum, I don't really know where I should get my other two letters of recommendation. In my case, should I ask my graduate school instructors for the letters? is this a good idea?