Escape Velocity Calculator Downloads & RevenueEscape Velocity Calculator · App Store

Escape Velocity is Newton's cannon for any world you like. Fire a cannonball, a bullet or a moon rocket from a mountain top and watch it fall back, circle the world, or leave it for good. Everything is computed on your iPhone or iPad. No account. No subscription. No internet connection of any kind.

In the Principia, Isaac Newton imagined a cannon on a mountain so high it stood above the air. Fire it gently and the ball falls back. Fire it harder and it lands further away. Fire it hard enough and the ground curves away beneath it as fast as it falls, and it never comes down. Escape Velocity draws that thought experiment live, for real worlds and real projectiles, with the true orbit worked out from the physics.

THE CANNON
Choose a world, a charge and a launch height, then fire sideways or straight up. The view follows the shot, close in for a ball that barely leaves the barrel and drawing back to the whole world for an orbit or an escape. Every shot is paced by the physics, quick near the ground and slow at the top. It tells you whether the shot falls back, orbits or escapes, with the height reached, the distance to landing, the flight time or the time for one orbit. A shot too small to see is put into words: a rifle round fired up on a neutron star rises about the width of a virus.

Famous shots load at a tap: the Paris Gun from Pluto, a rifle on a neutron star, a jump off Deimos, the HARP gun from the Moon, Newton's own cannon from Earth, a cricket ball off the asteroid Bennu, Jules Verne's Columbiad, and a cannon hovering beside a black hole.

THE BODIES
Thirty-six worlds to fire from, most with a painted portrait: the Sun, every planet, the great moons, Pluto and Ceres, asteroids and a comet, a white dwarf, neutron stars and black holes, and three things people built: the International Space Station, the Great Pyramid and a Saturn V. Each page gives escape speed, gravity, mass and density, what you would weigh there, which projectiles get away, and for the compact objects how slowly a clock runs. Figures come from NASA's Jet Propulsion Laboratory and are sourced on the page. Anything still an estimate is marked as one.

THE LADDER
Every world on one scale of escape speed, from a pyramid you could leave by blowing on it to a black hole even light cannot leave, with every projectile drawn across it as a line. Anything below the line, that shot escapes.

THE ROCKET
How much fuel it takes to leave. Choose a world, an engine from kerosene to a photon rocket, and a payload. The rocket equation answers in both its Newtonian and its relativistic forms, and puts numbers too large to picture into Saturn Vs, Earths, Suns and observable universes of fuel.

THE FORGE
Build your own world. Give it a name, a colour, a mass and a size, then squeeze it until it becomes a black hole. The Earth does at 8.87 millimetres. Fire from it, edit it, keep it. Enter your own mass and find out how slowly something would have to move to escape from you.

Save any setup a