Educational articles and essays on the basics of rocketry and orbital mechanics.
An in-depth analysis on rocket physics Full document with all topics in one place (opens in Google Docs)An interactive 2D physics simulation of orbital mechanics and rocket launches from Earth. Realistic atmosphere, variable thrust, drag, and a closed-loop guidance system.
Choose a mode from MENU before launching.
| Action | Control |
|---|---|
| Open menu | MENU |
| Launch | LAUNCH |
| Pause / Resume | PAUSE |
| Reset mission | RESET |
| Time warp | SPEED (1x → 1000x) |
| Zoom | ZOOM IN / ZOOM OUT / AUTO ZOOM |
| Camera | FOLLOW ROCKET / CENTER EARTH |
| Pitch (manual) | W / S or ↑ PITCH UP / ↓ PITCH DOWN |
| Orbital burns | Hold PROGRADE, RETROGRADE, NORMAL, etc. |
Real-time data: T+, stage, altitude, downrange, velocity (vertical/horizontal), acceleration, Max Q, dynamic pressure, drag coefficient, Mach, mass, propellant, thrust, pitch, gimbal, turn rate, apoapsis, periapsis.
Closed-loop, priority-based. In atmosphere: vertical ascent → gravity turn, Max-Q protection, turn-rate limits. In vacuum: raise apoapsis, keep periapsis safe, circularize at target altitude.
For more detail, see the project README on (a star would be appreciated if you like it!) GitHub.
What is this rocket launch simulator and how realistic is it?
This is a 2D physics-based rocket launch simulation featuring realistic orbital mechanics, atmospheric modeling (US Standard Atmosphere 1976), Mach-dependent drag coefficients, variable thrust and specific impulse, gimbal dynamics, and a closed-loop guidance system. The physics accurately models gravity, atmospheric drag, thrust vectoring, and orbital mechanics using real equations like the vis-viva equation and Kepler's laws.
What game modes are available in the rocket simulator?
Three modes are available: Manual Control (you pilot the rocket with W/S keys while guidance shows recommendations), Guided Launch (set a target altitude from 150-2000 km and the guidance system handles everything automatically), and Orbital Mode (spawn directly in orbit at 200-800 km to practice orbital maneuvers like prograde, retrograde, normal, and radial burns).
How does the closed-loop guidance system work?
The guidance system uses a priority-based approach. In atmosphere: it performs vertical ascent, initiates gravity turn, protects against Max-Q structural limits, and manages turn rates. In vacuum: it raises apoapsis to target altitude, maintains safe periapsis above 100 km, and performs circularization burns at apoapsis. It continuously adjusts based on current orbital parameters.
What physics concepts can I learn from this rocket simulator?
You can learn orbital mechanics (apoapsis, periapsis, orbital velocity), atmospheric physics (drag, dynamic pressure, Mach number), rocket propulsion (thrust, specific impulse, mass flow rate), gravity turns, the Karman line, circularization burns, and how real rockets reach orbit through gravity-assisted trajectory shaping.
What are the key features of the rocket configuration?
The default rocket is Falcon 9-like with two stages. Stage 1: 22,200 kg dry mass, 395,700 kg propellant, 7,607 kN sea-level thrust, 282s Isp. Stage 2: 4,000 kg dry mass, 92,670 kg propellant, 981 kN vacuum thrust, 348s Isp. Payload: 15,000 kg. You can also build custom rockets with the Rocket Builder feature.
How do I control the rocket in manual mode?
Use W/S keys or the on-screen PITCH UP/PITCH DOWN buttons to control pitch angle. The guidance system shows recommended pitch in cyan for reference. You can choose between Turn Rate mode (control target pitch, gimbal adjusts automatically) or Gimbal mode (direct gimbal control) in Settings. The pitch rate is limited to 2 degrees per second for realism.
What is Max Q and why does it matter?
Max Q (maximum dynamic pressure) is the point during ascent where aerodynamic stress on the rocket is highest, typically around 35 kPa for Falcon 9. It occurs when the combination of increasing velocity and decreasing air density creates peak pressure. The guidance system automatically protects against exceeding structural limits by following prograde during this phase.
Can I customize the rocket parameters?
Yes! The Rocket Builder feature lets you customize stage dry mass, propellant mass, thrust levels, specific impulse, payload mass, and more. Changes are shown in a live diagram with calculated center of gravity, center of pressure, and starting acceleration. Your custom rocket applies to the next mission start.
How accurate is the atmospheric model?
The simulation uses the US Standard Atmosphere 1976 model with 7 atmospheric layers from sea level to space. It includes geopotential altitude corrections, temperature-dependent calculations, and realistic density profiles. Drag coefficients vary with Mach number: subsonic (~0.25), transonic peak (~0.45), supersonic (~0.35), and hypersonic (~0.20).
What is a gravity turn and when should I perform it?
A gravity turn is a trajectory optimization where the rocket gradually pitches over while following its velocity vector (prograde). It starts around T+10 seconds with a small pitch kick, then the rocket naturally follows prograde through the atmosphere. This is more fuel-efficient than pitching over abruptly because it minimizes gravity losses and aerodynamic stress.