{"group":"make","pic":"living/pics/construction-city.webp","question":"How do you build a city without a single lorry of bricks?","answer":"From the ground under your feet. Robots dig the plain and bury homes under its soil, and printers lay new walls layer by layer from Mars itself.","play":{"label":"Watch a home being printed","href":"play/?at=62,-100,0,0.22,14&era=city&light=day"},"earth_mars":{"earth":{"head":"Builders bring it in"},"mars":{"head":"The plain is the quarry"},"pics":{"earth":"living/pics/em-construction-earth.webp","mars":"living/pics/em-construction-mars.webp"},"rows":[{"label":"Building stuff","icon":"layers","earth":"Cement, bricks, timber and steel, trucked in from all over.","mars":"Weathered volcanic rock, {cn_si}% silica and {cn_fe}% iron oxide. The city is made of it."},{"label":"Digging","icon":"gear","earth":"A digger leans its whole weight into the ground.","mars":"Everything weighs {g_pct}% of what it does on Earth, so diggers grip with drums that spin opposite ways."},{"label":"Under your boots","icon":"walk","earth":"Soft soil you can turn with a spade.","mars":"Ice-cemented ground from about {cn_ice} m down, hard as rock while it stays frozen."}]},"pin":[0.67,0.74],"soil":{"title":"What the plain is made of","line":"Every grain of the plain is something to build with. Tap a part to see what the city makes of it.","unit":"of the soil","parts":[{"id":"si","name":"Silica","use":"Melted into glass and spun into the stone wool the farms grow in."},{"id":"fe","name":"Iron oxides","use":"Rust: it makes Mars red, and pressed hard it binds into bricks with no oven at all."},{"id":"al","name":"Aluminium oxide","use":"Bakes hard when soil is heated into pads and paving."},{"id":"s","name":"Sulphur","use":"Melted with soil into sulphur concrete, which needs no water."},{"id":"rest","name":"Everything else","use":"Magnesium, calcium, chlorine and more, all baked in together."}]},"steps_title":"Four ways to build with soil","steps":[{"title":"Dig","text":"Light electric diggers with drums that turn opposite ways, so their pushes cancel. Each moves {cn_dig_lo} to {cn_dig_hi} m³ of soil a day."},{"title":"Set in","text":"Each steel home, {cn_vd} m across, is lowered level into a trench cut through the frozen ground, onto a bed of dry gravel."},{"title":"Cover","text":"{cn_cover} m of soil goes back over the top: {cn_cover_t} tonnes on every square metre of roof."},{"title":"Print","text":"Gantry printers lay walls in layers of baked soil: blast walls, berms and the homes under the domes."}],"cut":{"title":"Cut and cover","line":"How a home goes into the ground, drawn to scale.","marks":{"ice":"Frozen ground","soil":"Soil cover","vault":"Steel home","bed":"Gravel bed"},"text":"The trench is cut through ground that stays frozen and stands like a wall. The steel home goes in on its bed, the spoil goes back round it, and a low mound covers it all."},"grip":{"title":"Why the drums spin both ways","line":"A digger pushes by gripping the ground, and grip comes from weight.","earth":"On Earth","mars":"On Mars","weight":"Weight","push":"Push it can make","text":"On Mars a digger has only {g_pct}% of its Earth grip, so a hard push would just shove it backwards. Two drums turning opposite ways push against each other instead."},"scene":{"pic":"living/pics/scene-construction.webp","look":"03-11","shot":"site","focus":"50% 55%","zoom":1.6,"spots":[{"at":[0.09,0.5]},{"at":[0.33,0.61]},{"at":[0.59,0.56]},{"at":[0.82,0.32]}]},"proof":{"pic":"living/people/construction-proof.webp","place":"Johnson Space Center, Houston","when":"November 2022","head":"A home printed for Mars","credit":"Photo: NASA/Bill Stafford (public domain)"},"fact":"At NASA's Johnson Space Center in Houston stands Mars Dune Alpha, a home 3D printed by ICON. Crews of {cn_ch_crew} volunteers live inside it for {cn_ch_days} days at a time, as if they were on Mars.","quiz":[{"q":"What makes Mars red?","a":["Rust: iron oxide in the soil","Red sand blown from volcanoes","Copper in the rocks"],"why":"About {cn_fe}% of the soil is iron oxides, which is rust. Pressed hard, those grains even bind into bricks with no oven.","more":"In Coober Pedy, Australia, summer days pass {cn_cp_c}°C, so many people live in homes dug into the hillsides, cool all year round.","cite":"02-03 F-16, 03-11 F-19, F-25","from":"problem","fig":0,"icon":"layers"},{"q":"Why do the diggers have two drums turning opposite ways?","a":["So their pushes cancel out","To dig two trenches at once","To shake off the dust"],"why":"A digger has only {g_pct}% of its Earth weight to lean on. Two drums pushing against each other mean it never has to push against the ground.","more":"NASA's RASSOR 2.0 digging robot weighs just {cn_r2_kg} kg and is built to dig about {cn_r2_t} tonnes of Mars soil a day.","cite":"03-11 F-12, F-13","from":"why","fig":1,"icon":"gear"},{"q":"What does the soil on top of a buried home do?","a":["Keeps out radiation, cold and stones","Holds the air in","Weighs the home down in the wind"],"why":"{cn_cover} m of soil is the shield. The steel home inside it holds the air.","more":"In {cn_cc_built} the US Army dug Camp Century into the Greenland ice: {cn_cc_n} trenches, {cn_cc_km} km in all, roofed with steel arches and buried.","cite":"03-11 CM-03, F-11, 03-06 HA-02","from":"why","fig":0,"icon":"house"}],"notes":[{"beat":"fix","text":"A fresh trench shows a bright white rim of ice for a few days, until it fades away into the thin air.","cite":"03-11 CM-11"}],"everyday":{"title":"A city that grows","items":[{"time":"06:20","head":"Dug while you slept","text":"Overnight the robots cut a new trench and piled a small hill of soil beside it.","tag":"{cn_fleet_lo} to {cn_fleet_hi} m³ a day","pic":"living/pics/scene-construction.webp","pos":"20% 60%"},{"time":"12:30","head":"Layer by layer","text":"Under the new dome a printer lays another ribbed layer on a family's future home, and children press their noses to the glass to watch.","tag":"Printed from Mars","pic":"living/pics/construction-city.webp","pos":"50% 40%"},{"time":"18:45","head":"Moving day","text":"A new row is buried, lit and warm. The first family carries their boxes in to cheers from the neighbours.","tag":"{cn_cover} m of soil overhead","pic":"living/pics/homes-city.webp","pos":"50% 60%"}]},"living":"Every week the city grows a little. Robots dig through the night, printers hum under the new domes, and when a street is finished everyone turns out to watch the first family move in.","from":"From the building site","later":{"pics":{"city":"living/pics/construction-city.webp","far":"living/pics/construction-far.webp"},"city":{"tag":"Dug and printed","text":"Robots bury steel homes under the plain's own soil, and printers raise the first streets under glass."},"far":{"tag":"Made of Mars","text":"Domes of glass and steel made here, roads of cast basalt, and new neighbourhoods rising every year."}}}