Lunar Landing Challenge: Touch Down Softly
Understand that a landing is a balance between engine thrust and the Moon’s gravity: more thrust than weight slows you, less speeds you up, and every second of thrust burns fuel.
Before you try
What if you fired the engine at full power the whole way down? Would you land, or fly back up?
Try it out
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What happened?
Move a control to see what changes and why.
The lander only moves up and down in constant lunar gravity; real landers also steer sideways and pick a safe spot.
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Try these ideas
- Leave the throttle at 50% and watch what happens. Then find the throttle that makes the lander hover.
- Try a late, hard brake: low throttle most of the way, then full power near the ground.
- Start from 500 m with only 150 kg of fuel. Can you still land safely?
Why it works
On the Moon there is no air, so no parachute can slow a spacecraft. The only brake is the rocket engine. The Moon pulls the lander down at 1.62 m/s², about one sixth of Earth’s gravity. When the engine pushes up harder than the lander’s weight, the lander slows down; when it pushes less, the lander speeds up toward the ground.
You set the throttle while the lander falls. The simulator uses Newton’s second law each moment: acceleration equals thrust divided by mass, minus gravity. Fuel burns in proportion to thrust and the lander gets lighter as it goes, so the hover throttle keeps dropping. Chandrayaan-3 made this kind of powered descent near the Moon’s south pole in 2023.
Check your understanding
Question 1 of 4
The lander weighs 2,000 kg and the engine gives 3,240 N of thrust. What happens?
Why does the hover throttle keep dropping during the descent?
Why can’t a parachute be used to land on the Moon?
Which plan usually uses the least fuel?
Explain it in your own words
What changed? Why did it happen? Where might you notice this in everyday life?
What will you discover next?
Try Rocket Launch Lab: Why Rockets Are Mostly Fuel next.
For parents & teachers
- Ask: why do astronauts on the Moon still fall, just more slowly?
- Work out the weight of a 1,000 kg lander on Earth and on the Moon.
- Look up how Chandrayaan-3 slowed from 6,000 km/h to a soft landing.