By Rachel Gould - Engineering Student @ Jesus College, Cambridge
Starship is a fully reusable rocket under development by SpaceX. The project aims to create the most powerful rocket ever developed, capable of launching satellites into low Earth orbit, and eventually take cargo and humans to Mars. The vehicle is a huge 120m tall (nine meters taller than Saturn V) and could be around 5000t by mass when stacked and fueled.
The rocket has made headlines in the last 18 months through its high-altitude flight tests. The 50m tall top stage launches to around 10km altitude and performs a “belly flop” at apogee (the point at which it is furthest from the earth), rotating itself horizontally. 500m from the ground, two to three engines reignite and the rear flaps fold in, flipping it upright again, and the vehicle performs a controlled landing.
This maneuver has never been tried before by the space industry and is extremely difficult to execute, but the belly flop maneuver is surprisingly a safe and effective way to return the vehicle to earth to be used again.
The logic behind the action is relatively simple. An object falling from space will accelerate due to the Earth’s gravity until it reaches its terminal velocity – where the downwards force from gravity balances the force upwards from air resistance. The larger the air resistance, the lower the terminal velocity, as the object will accelerate less before the forces balance.
By “belly flopping” Starship increases its bottom surface area from 70m² to 545m²,