Launch it, fly it, land it on the Moon

How to fly Rocket

Rocket is a free space flight simulator you can play in your browser — no download and no account. You fly real-sized rockets with real stage masses, thrust and fuel, in real gravity: the Earth, the Moon and Mars at their true sizes and distances, the Earth's spin, its atmosphere thinning with height. Four missions, each harder than the last: orbit the Earth and splash down, dock with a space station, land on the Moon, and fly to Mars.

Getting to orbit

1. Throttle up (Z) and press Space: the engines light and the clamps let go.
2. Climb straight up for a few seconds, then tip the nose a few degrees east (→) and let it follow the prograde marker — the gravity turn. Or press 6 for SAS GUIDANCE, which flies the ascent programme for you.
3. Through max Q — the most aerodynamic stress, about 35 kPa — keep the nose on the airflow: turned more than 20° across it, the rocket breaks up.
4. When a stage burns out, press Space to drop it and light the next.
5. Orbit is a matter of speed sideways, not height: about 7.8 km/s at 200 km. Cut the engine (X) once periapsis is above 140 km — or coast to apoapsis and burn prograde there to round the orbit off.

The displays and widgets

• The view follows the rocket with the planet below; it zooms out as you climb, and the wheel or [ ] zoom it further. Markers on the edge point to your target and the planets.
• Flight data: altitude, vertical, surface and orbital speed, apoapsis and periapsis and the time to each.
• Attitude indicator: the yellow line is your nose; green circles are prograde and retrograde, the magenta diamond is guidance, a pink square the station.
• Engine and systems: thrust, thrust-to-weight, Isp (which rises as the air thins), mass, Δv in the stage and in all, dynamic pressure, g-load, heat-shield temperature, SAS and the parachutes, with warning lamps.
• The orbit display shows your path from above, predicted ahead — across into the Moon's or Mars's sphere of influence — with apoapsis, periapsis, the burn marker and the closest pass. System shows the whole inner solar system.
• The rocket display draws your stack with each tank emptying as it burns, the Δv each stage has left, and a chart of height and speed over the flight.
• Mission Control calls out each milestone and warns you of trouble. Ask it for your status, the next step, or a burn plan: it works out transfer windows, burn times and course corrections from your real orbit.

Time warp

Speed time up 10, 100 or 1000 times at any moment, and 10 000 or 100 000 times while you coast above the air with the engines off — a three-day trip to the Moon takes a couple of minutes, the eight-month cruise to Mars about four. Warp drops back by itself at burnouts, at the edge of the atmosphere, entering another world's sphere of influence and before a planned burn.

The missions

• Orbit and home: reach orbit, then drop the second stage, burn retrograde to bring periapsis below 40 km, and hold the capsule's heat shield into the airflow (SAS RETRO) through re-entry. Arm the parachutes (G): drogues open at 9 km, the mains at 2.5 km. Splash down under 12 m/s.
• Station rendezvous: the station orbits 420 km up. Make your orbit round, then ask for a burn plan — Mission Control times the transfer so you arrive together. Kill the relative speed (ANTI-TGT), point at the station (TARGET) and close with the RCS thrusters, under 0.5 m/s at contact.
• To the Moon: from a parking orbit, burn prograde at the TLI marker — about 3.1 km/s — and coast to the Moon. Brake retrograde at periapsis into lunar orbit, lower it, then land the lander upright, under 3 m/s.
• To Mars: the transfer window is open. Burn at the marker — about 3.6 km/s — and cruise for eight and a half months, asking for course corrections on the way. At Mars, brake at periapsis into an orbit above its atmosphere.

Frequently asked questions

Is Rocket free?

Yes. It is free to play with no sign-up, no download and no in-game purchases.

How realistic is it?

The rockets are modelled on real launchers' stages, the planets on the real ones, and the physics is real: gravity, the rocket equation, thrust and Isp that change with air pressure, drag, re-entry heating, and orbits that follow Kepler's laws, handed from one world to the next as patched conics. It is flat — every orbit lies in one plane — and it is a game, not a mission planner.

Is my progress saved?

Your best score on each mission is kept in this browser on this device; nothing is sent anywhere.