Any fun website about rocketry has to have one of these sections as honestly these questions fly around every circle of rocket enthusiasts I’ve ever been around.

The science behind the forces of physics at different stages of flight are easily explained in the formula below.

Rocket Equations Quick Reference

The content below is originally found at the following link:

html version as below: http://www.rocketmime.com/rockets/qref.html

Non html version: http://www.rocketmime.com/rockets/rckt_eqn.html

Equations for finding your rocket’s peak altitude and motor delay.

Definition of Terms

• m = rocket mass in kg (see below)
• g = acceleration of gravity = 9.81 m/s²
• A = rocket cross-sectional area in m²
• C_d = drag coefficient = 0.75 for average rocket
• r (rho) = air density = 1.22 kg/m³
• t = motor burn time in seconds (NOTE: little t)
• T = motor thrust in Newtons (NOTE: big T)
• I = motor impulse in Newton-seconds
• v = burnout velocity in m/s
• y₁ = altitude at burnout
• y_c = coasting distance
• Note that the peak altitude is y₁ + y_c
• t_a = coasting time => delay time for motor

Note on the rocket mass: you usually know the empty (no motor) mass of your rocket m_r. You can usually find the loaded mass of your motor, m_e, and the mass of the propellant, m_p. Both Estes and Aerotech provide these numbers in their spec sheets and with the motors. Then

• average mass during boost is m_r + m_e – m_p/2
  use this value for all but the y_c, q_a, and q_b calculations.
  
  
• mass during coast is m_r + m_e – m_p
  use this value for the y_c, q_a, and q_b calculations.