Jugnix · free physics worksheets
Chandrayaan-3: Getting to the Moon Worksheet
By the end you will: explain how Chandrayaan-3 raised its orbit with engine burns, was captured by the Moon, and landed near the south pole.
A. Explore with the simulation
Look at the first orbit after launch. Record the farthest point and the time per orbit.
Fire burns at the closest point (perigee) each time round. What happens to the farthest point and the time per orbit?
At the Moon, what must the spacecraft do, and what happens if the brake is too small?
B. Calculate
The first orbit went from 200 km to 36,500 km above Earth (radius 6,371 km). Find its semi-major axis.
Find the speed of a circular orbit 100 km above the Moon (GM = 4,903 km³/s², radius 1,737 km), and its period.
A command takes how long to reach the Moon, 384,400 km away, at 3 lakh km/s?
C. Think it through
Why did ISRO take about 40 days instead of flying straight to the Moon in 3 days like Apollo?
Answer key (for teachers and parents)
- Farthest point about 36,500 km, about 10.7 hours per orbit.
- Each burn stretches the orbit: the farthest point gets higher and each orbit takes longer.
- It must fire its engine against its motion to slow down and be captured. With too small a brake it flies past and isn't captured.
- a = (6,571 + 42,871) ÷ 2 = 24,721 km.
- v = √(4,903 ÷ 1,837) ≈ 1.63 km/s. T = 2π × 1,837 ÷ 1.63 ≈ 7,080 s ≈ 2 hours.
- 384,400 ÷ 300,000 ≈ 1.3 s.
- A slower route of many small burns around Earth uses far less fuel, so a smaller, cheaper rocket (LVM3) could do the job.
Free to print and share for teaching. Made with the interactive simulation at jugnix.com/simulations/chandrayaan-3.