Rocket Inputs
The page remains a single-column experience, while the form uses 3 columns on large screens, 2 on medium screens, and 1 on mobile.
Example Data Table
This example uses realistic hobby-scale values and shows what the calculator can produce with a moderate-thrust flight profile.
| Dry Mass | Propellant | Avg Thrust | Burn Time | Cd | Diameter | Launch Altitude | Apogee | Burnout Velocity |
|---|---|---|---|---|---|---|---|---|
| 1.80 kg | 0.70 kg | 140 N | 2.30 s | 0.55 | 0.10 m | 250 m | 749.53 m | 114.54 m/s |
Formula Used
A = π × (d / 2)2
D = 0.5 × ρ × Cd × A × v2
The code applies drag opposite to velocity using v × |v|.
a = (T × cosθ − m × g − D) / m
a = (−m × g − D) / m
vnew = v + a × Δt
hnew = h + vnew × Δt
β = m / (Cd × A)
This calculator uses a time-step simulation. It assumes constant average thrust during burn, linearly decreasing mass while propellant is consumed, constant air density, and a fixed launch angle from vertical.
How to Use This Calculator
- Enter the rocket dry mass without propellant.
- Add the propellant mass that will be burned during powered ascent.
- Supply average thrust and burn time from your motor data.
- Enter the drag coefficient and body diameter to estimate aerodynamic drag.
- Use local air density and gravity if your launch site differs from standard conditions.
- Set the launch angle from vertical and the site altitude above sea level.
- Choose a small time step such as 0.02 seconds for smoother results.
- Press the calculate button to view apogee, burnout values, derived engineering outputs, and the Plotly graph.
Frequently Asked Questions
1) What does apogee mean in a rocket flight?
Apogee is the highest altitude reached during flight. This calculator reports total apogee altitude and the altitude gain above the launch point.
2) Why is drag important in apogee estimation?
Drag removes energy throughout powered ascent and coast. Higher drag lowers burnout velocity and reduces peak altitude, especially for wide rockets or flights at high speed.
3) Does this model use changing rocket mass?
Yes. During burn, mass decreases linearly from initial mass to dry mass. That improves realism compared with a constant-mass estimate.
4) Is launch angle included in the calculation?
Yes. The calculator uses the thrust component aligned with vertical ascent. A larger angle from vertical reduces upward acceleration and usually lowers apogee.
5) Why can a rocket show poor altitude gain?
Low thrust, high mass, large drag, or a steep off-vertical angle can limit acceleration. A thrust-to-weight ratio near or below one is a common problem.
6) What time step should I use?
A smaller time step gives smoother and more stable results. Values around 0.01 to 0.05 seconds usually work well for small and medium rockets.
7) Does the calculator model wind or changing air density?
No. This version assumes constant air density and no wind. It is useful for fast engineering estimates, but not a full trajectory certification model.
8) Can I export the results for reports?
Yes. Use the CSV button for spreadsheet analysis and the PDF button for a compact report with inputs, outputs, and the plotted flight graph.