Week 13: Coast Phase

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After burnout, a rocket doesn't stop moving upward — it coasts, slowing under gravity alone until it reaches its highest point. This coast phase is where a lot of the interesting physics happens, and it's where some of our own club mentors' real research lives too.

Forces

Once the motor stops burning, drag becomes small enough at typical model rocket speeds that we can approximate the coast phase using gravity alone: pure kinematics, no thrust term needed.

Math

v² = v0² − 2·g·h

Worked example (metric): with a burnout velocity of 60 m/s, find the height at apogee (where v = 0): 0 = 60² − 2 × 9.81 × h → h = 3600 / 19.62 ≈ 183 m.