ThrustWeightRatio

ThrustWeightRatio (TWR) is designed for use by model rocketeers and Range Safety Officers (RSOs). TWR is intended to both assist rocketeers in proper motor selection and provide RSOs a mechanism to determine at check-in if a rocket has enough thrust to ensure stability once it has left the launch guide (rod/rail) given current wind conditions. If the length of the launch guide is also entered (optional), TWR will also calculate the estimated rocket speed at launch guide exit.

Inputs:
1. Average Motor Thrust in Newtons (N) or Pounds Force (lbf)
2. Rocket mass at launch in grams, kilograms, ounces or pounds.
3. Launch Guide (Rail/Rod) Length in meters or feet.

Outputs:

1. Thrust-Weight Ratio, with “traffic light” stability indicator: Less than 3 Red; 3-5 Yellow; 5-7 Green; >7 Blue.
2. Velocity at Launch Guide Exit in meters per second and feet per second.

3. Computation:
Thrust-Weight Ratio:
Average Motor Thrust in Newtons / Rocket Weight in Newtons =
(Total Impulse in Newton-Seconds / Motor Burn Time) / (Mass in Kilograms * Gravity)
Velocity at Launch Guide Exit, where:
velocity = √ [ 2 * gravity * (Thrust/Weight - 1) * (Launch Guide Length(meters))
(Source: velocity (m/s) = Rocket Acceleration * Time to End of Launch Guide:
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