Tow2a 20s (some manuals say approx 21s), Tow2b 21s to 3750m
Missiles have a short burn, some exhaust their motor in the launch tube and coast the whole way. Others are ejected, then boost and coast. TOW is ejected, motor ignites at 7-8m, burns only for 1.5 s, peak ~320-330m/s, coasts to max range over the next 19.5s
Very few are still accelerating at their maximum range, and then only if their range is limited by factors other than kinematics. Those which may still have an active motor, are almost always only using a low thrust arrangement as a sustainer/gas generator, to limit decay of energy, and the bulk of their acceleration still comes from the high thrust boost motor or boost phase of a multi-phase motor.
The velocity/range profile for most SAM/ATGM is broadly similar to a (draggy) shell, but with longer times of flight and an acceleration from a launch speed to peak over the first second(s).
e.g 9M119M launch ~200m/s, boost 800m/s within a very brief burn, then a long coast to their max range of 5000m at an "average" velocity (not actually flown for any duration) of ~350m/s
< Message edited by Lieste -- 11/30/2018 4:56:04 PM >