Calculate model rocket velocity, burnout speed, and delta-v. Include drag, gravity, thrust, and mass effects. Compare designs using practical launch data and cleaner assumptions.
1. Exhaust velocity: Ve = Isp × g₀
2. Mass flow rate: ṁ = Thrust ÷ Ve
3. Burn time: tb = Propellant mass ÷ ṁ
4. Ideal rocket equation: Δv = Ve × ln(m₀ ÷ mf)
5. Gravity loss: g₀ × tb × cos(angle from vertical)
6. Drag force: 0.5 × ρ × Cd × A × v²
7. Corrected burnout velocity: (Ideal delta-v − gravity loss − drag loss) × efficiency factor
This calculator uses a practical drag iteration. It gives a more realistic burnout estimate.
| Dry Mass (g) | Propellant (g) | Payload (g) | Thrust (N) | Isp (s) | Cd | Diameter (mm) | Air Density | Angle (deg) | Efficiency (%) | Burnout Velocity (m/s) |
|---|---|---|---|---|---|---|---|---|---|---|
| 180 | 55 | 20 | 18 | 80 | 0.55 | 41 | 1.225 | 5 | 95 | 136.08 |
A model rocket velocity calculator helps estimate powered flight performance. It combines thrust, mass, drag, and specific impulse. These values shape burnout speed. They also affect launch stability. Good estimates reduce guesswork. They improve design decisions before field testing.
Rocket motion depends heavily on changing mass. Propellant leaves the motor during burn. That raises acceleration over time. The classic rocket equation captures this effect. A higher mass ratio usually increases ideal delta-v. Lighter dry structures also help. Excess payload lowers predicted velocity quickly.
Average thrust gives the main pushing force. Specific impulse converts motor efficiency into exhaust velocity. Together they produce mass flow rate. That sets burn time. Short burns often create sharper acceleration. Longer burns may reduce peak loading. Both cases can reach different burnout speeds.
Real rockets never fly in a vacuum. Air density and drag coefficient matter. Body diameter affects frontal area. Larger frontal area increases aerodynamic drag. Drag grows with velocity squared. That means fast rockets lose speed rapidly. Even strong motors can underperform when drag rises.
During powered ascent, gravity pulls against motion. A near vertical launch sees stronger gravity loss along the path. The calculator subtracts that loss. It then applies a practical efficiency factor. This can represent rail friction, misalignment, or other real penalties.
The displayed burnout velocity is a design estimate. It is useful for comparison. It helps screen body sizes, motor choices, and mass targets. It also highlights thrust to weight ratio and acceleration limits. Use the output with test data. That gives better calibration for future launches.
It estimates corrected burnout velocity. That is the rocket speed at motor burnout after ideal delta-v is reduced by gravity loss, drag loss, and efficiency adjustment.
Specific impulse links propellant performance to exhaust velocity. Higher specific impulse usually improves ideal delta-v when rocket mass and thrust remain reasonable.
Drag coefficient represents aerodynamic resistance. A sleek rocket usually has a lower value. Lower drag helps preserve more of the ideal velocity during powered flight.
No. It is an engineering estimate. Real flights also depend on wind, fin alignment, motor curves, rail friction, weather, and construction quality.
Many hobby builds target at least 5:1 at liftoff. Higher ratios often improve off-rail speed, but structure and safety limits still matter.
Measuring from vertical makes gravity loss handling simpler for an ascent model. A small tilt may help weathercocking control, but it changes the effective gravity component.
It reduces the theoretical burnout velocity by a chosen percentage. This helps model practical losses that simple equations may not fully capture.
You can use it for early comparisons, but advanced projects need more detailed simulations, real thrust curves, stability analysis, and verified structural margins.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.