The trip from Earth to Mars will take at least 6 months. However we have to wait 19 months before we can launch off the surface of Mars back to Earth. You see planning a trip to Mars is not that easy. Once every 19 months Mars comes close enough to Earth to enable humans to reach it.The 2.5 year round trip to Mars posses many challenges.

The Orbiter will take astronauts to the Martian vehicle which is orbiting around Earth. It is likely that the Martian vehicle that will take humans to Mars will be built in stages outside of the Earth's atmosphere. There the relatively large structure, when compared to the Orbiter, will be launched towards Mars without having to fight against Earth's gravity.

The electrical system of the Martian space vehicle may be the same as the one currently operating on the Orbiter. A fuel cell, which is really a giant battery, reacts hydrogen and oxygen to form water and electricity. The Orbiter fuel cells produce water at the rate of 3.2 litres per hour. This amount of water is used for hygiene, rehydration of food and for drinking. Excess water is dumped overboard. However, on our long voyage to Mars it may be necessary to store this precious commodity.

The typical daily mass of food per astronaut is limited to just over 1 Kg. Water is not carried onboard as it is made during the mission by the fuel cells. Weight minimisation at lift-off from the Martian surface is important as it relates to less fuel and larger payloads.

During a 2.5 year trip to Mars, what mass of food should be taken onboard to feed 8 astronauts?

The mass of food needed to sustain the astronauts may seem very high. Can you think of ways that astronauts can become self reliant when it comes to food?