Lift-off is usually the most environmentally harmful stage of any space mission, with vast quantities of fuel burnt up in a matter of minutes. For instance, SpaceX’s Falcon 9 gets through 112 tonnes of refined fuel, emitting about 336 tonnes of CO₂. This is the equivalent produced by your average car driving almost 70 times around the world. As well as greenhouse gases, rocket engines emit particles that destroy ozone. These issues are growing more pressing with the emergence of commercial spaceflight. There were 114 space launches in 2020, but there may be up to 1,000 per year in future.

Sustainable fuels are the top priority to enable greener space travel. Current spacecraft use a variety of fuels, but most are based on fossil fuels. One potentially greener option is liquid hydrogen and oxygen. Hydrogen can be obtained sustainably by using solar power to break water down into oxygen and hydrogen.

Reusable rockets can cut down on some of the waste associated with spaceflight. Traditionally, boosters, fuel tanks and other components are treated as expendable. But guiding them back to Earth in a controlled manner opens new possibilities—most components from the Falcon 9 can be reused up to 100 times.

Truly environmentally friendly space travel is still some way off. But we already have many of the technologies needed to start limiting its impact on our planet.

Q16: What do we learn from the passage about the lift-off of spacecraft?
Q17: What happens traditionally to boosters, fuel tanks and other components in spaceflight?
Q18: What does the passage say we already have regarding spaceflight?