If Watney turns off all the heating, he can use all of the rover’s 18000 watt hours of power to drive. Now part of the power usage of the rover is based on heating. To make the journey faster, he cannibalizes the second rover and doubles the daily travel distance to 70 km. The basic rover is equipped to go 35 km on a full charge: Watney works out a way to carry enough solar panels with him to recharge the rover on a daily basis. Mark has to take the rover and make a 3200 km journey to Schiaparelli Crater to blast off and hopefully intercept the rescue mission as it passes overhead. Oxygen required = 40.9 kg Survival Problem 5: Rover Journey to Schiaparelli Crater Hydrogen required = water required × water to hydrogen ratio Oxygen required = water required × water to oxygen ratio If we assume that 1 litre of water is the same as 1 kilogram of water, then we can calculate how much oxygen and hydrogen Watney will need to source to generate the required 368 litres of water: Using the above figure and some information about the molecular weights of the various molecules involved, we can calculate that 1 kilogram of oxygen combines with 0.125 kilograms of hydrogen to form 1.125 kilograms of water. The figure above shows how two hydrogen molecules combine with one oxygen molecule to create two water (H 20) molecules. Watney needs water to drink, but also to grow his crops (before the explosion squashes that plan).įrom the various equipment and supplies on the base, he can get his hands on both oxygen and hydrogen. Total farming water required = 368 litres Survival Problem 4: Water Creation Total farming water required = number cubic metres soil × water required per cubic metre He calculates that he needs about 40 litres of water per cubic metre of soil. Planting the potatoes won’t be enough – Mark will need to water them as well. Total soil required = farming area × soil depth
To successfully grow potatoes, Mark has to cover the floor to a depth of 10 centimetres: If the circular farm area has a radius of 5.41 metres, we can calculate the total farming area: Watney set up the roughly circular habitat to become a farm. Mark now has a major problem, because the emergency resupply probe isn’t expected to reach him until Sol 856 – which is more than 250 days after his food is expected to run out. The crops will last him:Ĭrop time = number of plants saved × number of potatoes per plant × calories per potato / calories required per day The rations we already know will last him about 400 sols. Revised survival estimate = ration time + crop time We can calculate how long he can survive with just this limited crop and his rations: All he has are the rations, and the crops he’s already grown, which he estimates to be about 400 plants, with an average of 5 potatoes per plant. Survival Problem 2: Disaster StrikesĪt one point, a catastrophic explosion exposes Mark’s entire potato farm to the Martian atmosphere and kills his remaining crop. For example, “that burger has 250 calories” actually means that burger has 250 kilocalories, or 250,000 calories.ġ kilocalorie is equivalent to 4.184 kJ, which is another unit of energy in food that is used in many places around the world. Number of grown potatoes required = 10000Ī note about calories: when people talk about calories in food, they’re actually talking about “kilocalories” (1 thousand calories).
Number of grown potatoes required = 1500000 / 150 Number of grown potatoes required = total calories required / calories per potato Mark estimates a single potato has about 150 calories. He needs to grow a whopping 1.5 million calories of potatoes! Total extra calories required = 1000 × 1500 Total extra calories required = sols left × calories required per day Mark calculates he needs a minimum of 1500 calories per sol. His only solution – to grow potatoes on Mars using his own faeces (poo) as fertilizer! Yuck! That leaves Watney with another 1000 sols without food. Rationed supply time = ration factor × normal supply duration Now since times are desperate, Watney can also ration out the food to last a bit longer – about 1.33 times longer. Since there’s only one person left, that can be multiplied by 6: NASA provided the original team of 6 crew with enough food for about 50 sols. How long? Well, he estimates it’s 1400 sols (Martian days which are 24.5 earth hours long) until he will be rescued. He has to use a lot of science and maths to make it through a range of hairy survival situations.Īstronaut Mark Watney is marooned and it looks like he’s going to be stuck on the planet for a long time. Matt Damon plays an astronaut who is presumed dead in an accident and left behind on Mars. The fantastic “ The Martian” film came out in 2015 and itself was based on the equally good book by Andy Weir published in 2011.
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