Fly the mission · Learn the physics · Unlock each phase
The rocket goes UP because fire shoots DOWN! 🔥
Isaac Newton discovered: every push has an equal push back the other way! When the rocket pushes gas DOWN really hard, the gas pushes the rocket UP just as hard. That's called thrust!
But gravity is always pulling down. The rocket has to push harder than gravity to leave the ground!
The SLS rocket works because of Newton's 3rd Law: for every action, there is an equal and opposite reaction.
The engines burn fuel and blast hot gas downward at enormous speed. The reaction force pushes the rocket upward — that's thrust.
Try the sliders: increase thrust and watch what happens. Reduce fuel and see how it affects performance!
The SLS Block 1 generates 8.8 million pounds of thrust (39.1 MN) — about 1.5× the weight of a fully loaded aircraft carrier. Newton's 3rd Law: F⃗ reaction = −F⃗ action.
Net upward acceleration: a = (F_thrust − F_gravity − F_drag) / m. As fuel burns, mass decreases, so acceleration increases even at constant thrust — this is the Tsiolkovsky rocket equation.
Drag peaks at "Max Q" — maximum dynamic pressure — where atmospheric density × velocity² is greatest, around 40 seconds after launch. The engines briefly throttle down at Max Q to protect the vehicle structure.
Answer correctly to unlock Phase 2!
Why doesn't the spaceship fall down when it's going around Earth? 🌍
It IS falling — but it's also moving sideways SO fast that Earth keeps curving away underneath it! The spaceship falls and falls but never hits the ground!
To escape to the Moon, the engines fire again — a big kick called TLI — and now it goes fast enough to escape Earth and travel to the Moon! 🌕
In orbit, gravity is still pulling the spacecraft down — but the spacecraft moves sideways so fast that it keeps "missing" Earth as it falls. That balance between falling and moving forward creates an orbit!
To go to the Moon, Orion fires its engine one more time — the Trans-Lunar Injection (TLI) burn. This speeds up Orion enough to escape Earth's orbit and coast to the Moon!
Orbital mechanics follow Newton's Law of Universal Gravitation: F = Gm₁m₂/r². At any altitude, there's one exact speed where centripetal acceleration equals gravitational acceleration — that's orbital velocity.
The TLI burn raises Orion's velocity above Earth escape velocity (~11.2 km/s). The Hohmann-like transfer arc then coasts to the Moon with no additional burns — gravity alone shapes the trajectory. The free-return geometry means if TLI is correct, Orion returns to Earth even if all engines fail.
Answer correctly to unlock Phase 3!
The Moon is like a giant invisible magnet! 🌕
As Orion flies near the Moon, the Moon's gravity grabs it and swings it around — like swinging a ball on a string and letting go! The Moon pulls Orion around its far side and then flings it back toward Earth!
No engine needed for the return trip — the Moon's gravity does all the work! 🪃
This is the free-return trajectory — one of the most elegant tricks in spaceflight! Orion doesn't orbit the Moon. Instead, it approaches, gets bent by the Moon's gravity like a ball curving around a corner, and naturally arcs back to Earth.
Try changing the flyby distance slider. Too close and the curve is too tight. Too far and the Moon's gravity barely affects the path. The sweet spot sends Orion exactly home!
The free-return trajectory is a figure-8 shaped path (technically a translunar orbit) that satisfies the restricted three-body problem for the Earth-Moon system. At exactly the right energy and angle, gravitational forces from both bodies create a closed path returning to Earth's atmosphere.
The beauty: this trajectory has zero fuel cost for return. If all propulsion fails beyond TLI, the crew still returns to Earth — a critical safety design feature first validated by Apollo 8 and later relied upon during Apollo 13's oxygen tank failure.
Answer correctly to unlock Phase 4!
Coming home is the most dangerous part! 🔥
The spaceship falls toward Earth SUPER fast — 25,000 miles an hour! That's like 33 times faster than a bullet! When it hits the air, the air pushes back SO hard that it makes the spaceship glow white hot!
Then big parachutes open and slow Orion way down — SPLASH into the ocean! 🌊 The astronauts are safe!
When Orion hits Earth's atmosphere at 25,000 mph, air molecules can't get out of the way fast enough. They pile up and get compressed — and compressed air gets extremely hot, reaching over 5,000°F!
The heat shield absorbs this energy and slowly burns away (ablates), carrying the heat with it — like a protective ice cube melting to keep your drink cold.
The entry angle matters hugely: too steep = burn up. Too shallow = skip off the atmosphere back into space!
Reentry physics are governed by the hypersonic aerodynamics of a blunt-body capsule. The bow shock wave converts kinetic energy into thermal energy. At Mach 32 (~10.7 km/s), peak stagnation temperatures exceed 2,800°C — hot enough to ionize atmospheric nitrogen, creating a plasma sheath that blocks radio communications (the "blackout" phase).
Orion uses a skip reentry — deliberately bouncing off the upper atmosphere once before final reentry. This reduces peak g-forces and allows more precise landing zone targeting. The corridor is only ~2° wide: steeper → overshoot g-limit (9G). Shallower → skip to orbital insertion, no return possible.
Complete the mission — answer to finish!
The mission has completed! You've piloted the spacecraft through all four phases and mastered the physics of deep-space human exploration!
Track the real mission live at nasa.gov/trackartemis