Calculator inputs
Large screens use three columns, medium screens use two, and mobile uses one.
Example data table
Sample scenario: nose radius 0.75 m, emissivity 0.85, radiative add-on 12%, and safety margin 10%.
| Altitude (km) | Velocity (km/s) | Density (kg/m³) | Total Heat Flux (W/cm²) | Total Heat Flux (MW/m²) | Wall Temp (K) | Dynamic Pressure (kPa) |
|---|---|---|---|---|---|---|
| 80.00 | 7.90 | 0.00001570 | 483,996.26209 | 4,839.96262 | 17,801.35 | 0.48994 |
| 65.00 | 7.30 | 0.00014934 | 1,177,775.63301 | 11,777.75633 | 22,233.51 | 3.97921 |
| 50.00 | 5.70 | 0.00097752 | 1,434,471.81492 | 14,344.71815 | 23,356.91 | 15.87989 |
| 35.00 | 3.60 | 0.00821392 | 1,047,577.75147 | 10,475.77751 | 21,591.80 | 53.22620 |
Formula used
This calculator is intended for fast engineering screening. It does not replace full trajectory analysis, chemistry-coupled CFD, or detailed TPS material response simulation.
1) Convective stagnation-point heating
q_conv = k × √(ρ / Rn) × V³
- q_conv = convective heat flux.
- k = Sutton–Graves engineering coefficient.
- ρ = atmospheric density at the selected altitude.
- Rn = nose radius.
- V = flight velocity.
2) Total engineering heat flux
q_total = (q_conv + q_conv × radiative_add_on) × (1 + safety_margin)
The radiative percentage here is a configurable allowance. It is useful for early trade studies when you want a more conservative screening estimate.
3) Equilibrium wall temperature
T_wall = [ q_total / (ε × σ) ]^(1/4)
- ε = surface emissivity.
- σ = Stefan–Boltzmann constant.
4) Dynamic pressure
q_dynamic = 0.5 × ρ × V²
5) Approximate integrated heat load
Heat load ≈ Σ(average heat flux × time step)
The profile assumes a simple descent sweep between the selected start and end states. It is a practical planning estimate rather than a full six-degree-of-freedom trajectory solution.
How to use this calculator
- Enter the current altitude where you want the heating estimate.
- Enter reentry velocity in km/s and the effective nose radius in meters.
- Set surface emissivity for the wall-temperature estimate.
- Add a radiative percentage if you want a conservative allowance.
- Apply a safety margin that matches your design practice.
- Choose the lower altitude and lower velocity for the plotted descent profile.
- Press Calculate reentry heating.
- Review the summary metrics, graph, and exported CSV or PDF if needed.
Frequently asked questions
1) What does this calculator estimate?
It estimates stagnation-point convective heating, total engineering heat flux, equilibrium wall temperature, atmospheric density, dynamic pressure, and an approximate integrated heat load along a simplified descent profile.
2) Is this suitable for final TPS sizing?
No. It is best for preliminary trade studies and quick comparisons. Final sizing should use validated trajectory analysis, material response modeling, uncertainty treatment, and higher-fidelity aerothermodynamic methods.
3) Why does nose radius matter so much?
A larger effective nose radius reduces the square-root density-to-radius term in the heating relation, which usually lowers stagnation-point heat flux for the same atmosphere and velocity.
4) Why is velocity so influential?
The screening correlation uses velocity cubed. That means small velocity increases can produce very large heating changes, especially in the higher-speed part of the entry corridor.
5) What is the radiative add-on percentage?
It is a user-controlled engineering allowance added on top of the convective estimate. It helps early studies include a conservative thermal margin without performing detailed radiative-heating analysis.
6) Does the wall-temperature result include conduction into the structure?
No. The wall temperature is a radiative equilibrium estimate. Real hardware can differ because of conduction, catalytic effects, ablation, pyrolysis, material response, and non-equilibrium chemistry.
7) How is the heat load calculated?
The tool builds a simple altitude-velocity sweep, estimates heat flux at each step, derives an approximate descent time from flight-path angle, and integrates heat flux over that path.
8) Why can peak heating occur below the starting altitude?
Heating depends on both density and velocity. During descent, density rises while velocity falls. Their combined effect can create a heating maximum at an intermediate altitude.