"There’s a one-ton, automobile-sized piece of American ingenuity…sitting on the surface of Mars right now.” –John P. Holden, President Obama’s science adviser responding to doubts about America’s leadership in space exploration
On August 6th, the NASA rover Curiosity touched down on the surface of Mars. It aims to investigate Martian climate, geology, and ability to support life. NASA released the animation below to show how Curiosity landed on the surface.
It might surprise you, but the forces acting on the rover in its landing can be easily explained using what we’ve learned in the first two weeks of Physics 111. Here’s a free-body diagram of the rover’s descent into the Martian atmosphere.
The rover reaches terminal velocity (like the penny example we did in class) quickly after it enters the atmosphere of Mars. Terminal velocity is achieved when the force due to air resistance equals the force of Martian gravity, as shown in the diagram. When the rover reaches a certain altitude, the parachute is deployed, which acts to further increase the effective force of air resistance by increasing the area term. This decreases the terminal velocity more and allows the rover to approach the surface at a less disastrous velocity.
When the it reaches a lower altitude, the rover is ejected and thrust boosters are activated in the direction opposite to the force of gravity to stabilize the rover and to allow it to be safely landed on the surface of Mars. The rover is then lowered using a pulley system. Here’s a free-body diagram of the rover being lowered onto Mars.
Landing on Mars is pretty complicated. A few years ago when the rovers Spirit and Opportunity landed, the landings were a little less sophisticated.