Except for your ‘rocket’ function, most of that looks as though it should work.
Leave out the subscript reference when you are declaring your function, and within your function, since ‘k’ is not defined within your function, and is not necessary anyway.
Try this instead:
function h = rocket(t)
h = (60+(2.13*(t^2))-(0.0013*(t^4))+(0.000034*(t^4.751)));