T T-0Alt 0 kmSpeed 0 m/sMach 0q 0 kPaAcc 0 gStage 1on the padFPS 0

Drag to orbit, wheel or pinch to zoom. Design the rocket on the right, check the go / no-go table, then press Launch. The blue line is the flight path; circles on the right mark the atmosphere layer you are in.

Spaceport to Orbit: Rocket Mission Designer

Design a fictional two-stage rocket, pass the pre-launch go / no-go check, fly it through the atmosphere layers and put a small science satellite on a circular orbit.

Pre-launch verdict (model run of the current design)

Vehicle design

Flight programme

Mission and weather

Time scale

Live readouts

Altitude and speed during the flight

Dynamic pressure (aerodynamic load)

Delta-v budget of this design

Uncertainty (Monte-Carlo, 60 seeded flights)

Specific impulse +-1.5 % (1 sigma), drag coefficient +-10 %, upper wind +-4 m/s around the slider value.

Independent numerical checks

Controls and mission steps

Drag / one finger: orbit the camera; wheel / pinch: zoom. "Camera" cycles follow, pad (fixed), wide.
Presets load a complete design. Each slider change re-runs the whole flight in the background and updates the go / no-go table.
Auto-tune searches the kick angle and pitch rate (25 trial flights) for the current design and target.
Phases: lift-off, max-Q (peak dynamic pressure), main-engine cut-off (MECO), stage separation, stage-2 ignition, fairing jettison above 110 km, second-engine cut-off (SECO) and satellite deployment.
Success: perigee at least 180 km and eccentricity at most 0.02. After SECO use the time scale to watch the orbit.

The science

Rocket equation. Δv = I_sp g₀ ln(m₀/m_f) for each stage; the stage Δv add. Staging pays because the empty tank mass of stage 1 is thrown away before stage 2 has to accelerate it. This design carries about 10.2 km/s of ideal Δv.

Why 10 km/s when orbit needs 7.7 km/s? Circular speed at radius r is v_c = √(μ/r), 7.73 km/s at 300 km. Gravity loss ∫ g sinγ dt (about 1.7 km/s here), drag loss and steering loss make up the difference; they are counted in the budget panel.

Thrust depends on altitude. F = ṁ I_sp,vac g₀ − p_a(h) A_e; the sea-level I_sp (285 s) is lower than the vacuum value (315 s) because ambient pressure acts on the nozzle exit area.

Atmosphere and loads. ISA 0 to 86 km (piecewise-linear temperature, barometric formula), exponential with a 5.9 km scale height above. Drag D = ½ ρ v² C_D(M) A with a transonic drag rise; dynamic pressure q = ½ ρ v² peaks at max-Q near 64 s. The engine is throttled back when q approaches its limit.

Equations of motion. Planar, spherical non-rotating Earth: r̈ = −μ r̂/r² + (T − D)/m, RK4 with dt = 0.05 s while the engines burn and velocity Verlet (leapfrog, symplectic) in the vacuum coast. Mass flows at ṁ = F/(I_sp g₀).

Guidance. Stage 1: vertical rise, a kick, then thrust along the velocity (a gravity turn) but never steeper than a linear pitch programme. Stage 2: closed-loop terminal guidance that commands the vertical acceleration a = 6Δh/t² − 4v_r/t (double integrator) so the stage arrives at the target height with zero vertical speed; cut-off when the specific orbital energy reaches that of the target circle. The orbit is then a = −μ/(2ε), e = √(1 + 2εh²/μ²).

Simplifications. Fictional vehicle, not a copy of any real rocket; 2-D flight plane, no Earth rotation or J2, no structural or aero-stability model, no stage-1 recovery, wind modelled only as drag on the relative airspeed, round-number drag, mass fractions and thrust values. Not a design tool. Peaceful science mission only. Models built with Blender, scene by Three.js.