Engineers developing rockets must control variables and consider failure points when improving rocket designs to increase the amount of mass they can lift into space. “There are a lot of different pieces that you can change when you’re designing an engine or a rocket,” says Dr. Kristina Kipp, an engineer working on the Mars 2020 rover mission. “We can change the fuel type and that can change how the propulsion system works. We can change the number of engines and the size of the engines. We could even change the shape to make the rockets more aerodynamic.”