{"group":"port","pic":"living/pics/fuel-city.webp","question":"Where does a ship's fuel for home come from?","answer":"From Mars itself. The plant turns ice from under the plain and carbon dioxide from the air into methane and oxygen, then keeps it ice-cold in big white tanks until a ship needs it.","play":{"label":"Visit the tank farm","href":"play/?at=505,500,-1.83,0.22,26&era=city&light=day"},"recipe":{"title":"The recipe","sub":"Fuel from water and air.","line":"One carbon dioxide and two waters become one methane and two oxygens.","from":"Air and ice","to":"Rocket fuel","carbon":"Carbon","oxygen":"Oxygen","hydrogen":"Hydrogen","mix":"Mix","again":"Back to the start","before":"One carbon dioxide from the air and two waters from the ice.","after":"The atoms swap partners: one methane to burn and two oxygens to burn it with.","per":"Every tonne of fuel takes about {fu_water} t of water and {fu_co2} t of carbon dioxide."},"steps_title":"How the plant does it","steps":[{"icon":"intake","title":"Air catchers","text":"Filters strip out the dust, then cold plates freeze carbon dioxide out of the air as white frost."},{"icon":"plant","title":"The plant","text":"Electricity splits water into hydrogen and oxygen, and a hot reactor turns the hydrogen and carbon dioxide into methane."},{"icon":"tanks","title":"Cold tanks","text":"A pair of big insulated spheres for every ship going home: {fu_lox_t} t of oxygen and {fu_ch4_t} t of methane."},{"icon":"pipe","title":"Pipeline to the pads","text":"A buried, insulated line runs {fu_pipe_lo} to {fu_pipe_hi} km out to each pad's fuelling point."}],"loop":{"title":"The loop","line":"Water is split, carbon dioxide is caught, the reactor makes methane, and its water goes round again.","ice":"Ice water","air":"Mars air","split":"Splitter","freeze":"Frost catcher","reactor":"Methane reactor","oxygen":"Oxygen","methane":"Methane","hot":"{fu_sab_lo} to {fu_sab_hi}°C","round":"Water goes round again"},"cold":{"title":"Cold enough to pour","line":"Oxygen turns liquid at {fu_lox}°C and methane at {fu_ch4}°C, so the tanks are wrapped and kept cold by machines.","water":"Water freezes","day":"Summer afternoon","frost":"Air freezes to frost","methane":"Methane liquid","oxygen":"Oxygen liquid"},"earth_mars":{"earth":{"head":"Fuel is pumped from the ground"},"mars":{"head":"Fuel is made from ice and air"},"pics":{"earth":"living/pics/em-fuel-earth.webp","mars":"living/pics/em-fuel-mars.webp"},"rows":[{"label":"The ingredients","icon":"drop","earth":"Natural gas is drilled from deep underground.","mars":"Air that is {fu_co2_air}% carbon dioxide, and water from the ice under the plain."},{"label":"Fire","icon":"flame","earth":"Air rich in oxygen, so a gas leak can catch fire.","mars":"Methane cannot burn with less than {fu_loc}% oxygen around it. Mars air has {fu_o2}%."}]},"living":"Nobody waits for fuel here. The plant hums quietly all year, the tanks stand frosted and ready, and when a ship is due to fly home it fills up through a pipe under the plain: Mars air and ancient ice, bottled at {fu_lox}°C.","fact":"The space station has run this plant's chemistry before. From {fu_iss_lo} to {fu_iss_hi}, a Sabatier unit aboard turned the crew's breathed-out carbon dioxide into fresh water and sent the methane overboard as waste. Here, that methane is the fuel home.","later":{"pics":{"city":"living/pics/fuel-city.webp","far":"living/pics/fuel-far.webp"},"city":{"tag":"Fuel for every window","text":"The plant hums day and night, filling a pair of tanks for every ship that flies home in the next window."},"far":{"tag":"The city's filling station","text":"A long double row of tanks fuels ships every window, and the long-range rovers on the roads between cities."}},"pin":[0.68,0.32],"scene":{"pic":"living/pics/scene-fuel.webp","look":"03-04","shot":"yard","focus":"45% 55%","spots":[{"at":[0.12,0.6],"side":"left"},{"at":[0.45,0.62]},{"at":[0.32,0.26]},{"at":[0.8,0.55]}]},"proof":{"pic":"living/people/fuel-proof.webp","place":"In orbit around Earth","when":"{fu_iss_lo} to {fu_iss_hi}","head":"The same reaction, in orbit","credit":"Photo: NASA (public domain)"},"quiz":[{"q":"What is Arcadia's rocket fuel made from?","a":["Ice water and carbon dioxide from the air","Oil found under the plain","Fuel shipped from Earth"],"why":"Every tonne of fuel takes about {fu_water} t of water and {fu_co2} t of carbon dioxide from the air.","more":"Paul Sabatier, the chemist whose reaction makes the methane, shared the {fu_nobel} Nobel Prize in Chemistry.","cite":"03-04 F-01, F-05, F-06","from":"problem","fig":0,"icon":"flame"},{"q":"Why can't spilled methane catch fire outside?","a":["Mars air holds almost no oxygen","It is too cold to burn","The dust smothers it"],"why":"Methane needs at least {fu_loc}% oxygen around it to burn. Mars air has just {fu_o2}%.","more":"Liquid oxygen is pale blue, and one litre of it boils into {fu_expand} litres of gas.","cite":"03-04 F-22, F-29","from":"problem","fig":0,"icon":"air"},{"q":"How cold is liquid oxygen?","a":["{fu_lox}°C","About as cold as a freezer","Just below freezing"],"why":"Oxygen turns liquid at {fu_lox}°C and methane at {fu_ch4}°C, so the tanks are wrapped and kept cold by machines.","more":"In 2015 NASA piped a cooler into a fuel tank through a web of tubes, and it stopped the fuel boiling away altogether.","cite":"03-04 F-22, F-24","from":"why","fig":1,"icon":"thermo"}],"notes":[{"beat":"fix","text":"Making fuel makes spare oxygen too. It is kept as liquid in the tank farm and piped to the homes: the city's reserve of breathing air.","cite":"03-04 C-05"}],"from":"From the fuel plant","everyday":{"title":"A day at the plant","items":[{"time":"09:20","head":"Filter day","text":"Two technicians drive out to swap the dust filters on the air catchers, and the plant hums on without a pause.","tag":"{fu_co2} t of air a tonne","pic":"living/pics/scene-fuel.webp","pos":"15% 60%"},{"time":"14:00","head":"Frost on the valves","text":"Every cold pipe grows white frost from the air itself, so everything cold wears a thick wrap.","tag":"{fu_ch4}°C","pic":"living/pics/em-fuel-mars.webp","pos":"60% 50%"},{"time":"19:30","head":"A ship fills up","text":"Fuel flows through the buried pipe to the pad, and a ship stands ready for the trip home.","tag":"{fu_pipe_lo} to {fu_pipe_hi} km of pipe","pic":"living/pics/fuel-city.webp","pos":"80% 50%"}]}}