{"group":"survive","pic":"living/pics/power-city.webp","question":"How do you keep the lights on when a dust storm can hide the Sun for months?","answer":"With small reactors buried out on the plain. They hum away day and night, in every season, and a storm never touches them.","play":{"label":"Walk out to the reactor field","href":"play/?at=-40,-362,0,0.16,16&era=city&light=day"},"storm":{"title":"When dust hides the Sun","line":"Pick a day and watch what reaches the ground.","days":[{"id":"clear","name":"A clear summer day","big":"100","unit":"% of the sunlight","text":"{vl_clear} Wh of sunlight lands on every square metre, measured by Viking 1 on a clear northern summer day."},{"id":"dusty","name":"A dusty winter day","big":"{vl_dusty_pct}","unit":"% of a clear day","text":"Dust in the air soaks up the beam. Viking 1 measured {vl_dusty} Wh on a dusty winter day, most of it scattered glow."},{"id":"storm","name":"A global dust storm","big":"{opp_pct}","unit":"% of a normal day","text":"In 2018 a storm wrapped the whole planet. Opportunity's solar panels fell from {opp_hi} to {opp_lo} Wh a day."}],"safe":"Arcadia's reactors give exactly the same power on all three.","sun_label":"Sunlight on the panels","reactor_label":"Power from the reactors"},"steps_title":"A reactor on the plain","steps":[{"icon":"unit","title":"The buried reactor","text":"Each unit sits in a pit under a mound of soil, with its white cap on top. The soil keeps its radiation in."},{"icon":"fins","title":"The radiator","text":"Heat leaves by glowing away into space, so tall white fins shed it from both faces, bright as mirrors in the low Sun."},{"icon":"ring","title":"The keep-out ring","text":"Red lamps mark a ring {buried_m} m out. At its edge the reactor adds less than a quarter of what the Martian sky already gives."},{"icon":"cable","title":"Cables to town","text":"Every home is fed by two buried cable routes from a field {rf_lo} to {rf_hi} km away, so one cut cable never puts the lights out."}],"heat":{"title":"Where a reactor's heat goes","sub":"NASA's {o22_kwe} kW design, with every line drawn to the same scale.","heat":"{o22_kwt} kW of heat","power":"{o22_kwe} kW of electricity","spare":"{p_waste} kW of spare heat","warm":"Warms the wells and homes","glow":"Glows away from the radiator","line":"Only {p_eff} of every 100 units of heat become electricity. The rest is never wasted if the city can use it: a warm loop carries it to the ice wells and the homes.","court":"A doubles tennis court","rad":"The radiator, {o22_rad} m²","rad_line":"Its radiator covers {o22_rad} m², about {p_rad_court_pct}% of a doubles tennis court."},"field":{"title":"Why the field stands out on the plain","sub":"Distances drawn to scale.","unit":"Reactor","ring":"Keep-out ring, {buried_m} m","town":"Town, {rf_lo} to {rf_hi} km","sky":"Mars's own sky, every year","edge":"Reactor, at the ring's edge","line":"Stand at the ring's edge all year and the reactor adds at most {p_fence_msv} mSv, against the {h_plain_y} mSv the open plain already gives. In town, a kilometre and more away, it is nothing you could measure."},"earth_mars":{"earth":{"head":"Sunshine you can count on"},"mars":{"head":"Dust can hide the Sun for months"},"pics":{"earth":"living/pics/em-power-earth.webp","mars":"living/pics/em-power-mars.webp"},"rows":[{"label":"Sunlight","icon":"sun","earth":"{earth_sun} watts on every square metre above the air.","mars":"{mars_sun} watts: {f_sun_pct}% of Earth's."},{"label":"Dust storms","icon":"wave","earth":"Clouds come and go, and the Sun is back within days.","mars":"A global dust storm can dim the Sun for {s01_sols} days."}]},"living":"The power here never blinks. Out on the plain the reactors hum under their mounds day and night, so the rooms are warm, the lights are bright and the farms glow, even while a dust storm turns noon to dusk. Each of us has the power of {p_homes} British homes.","fact":"In {krusty_year}, NASA ran a small reactor built for the Moon and Mars at full power for {kp_hours} hours. The team made engines and heat pipes fail on purpose, and it kept on running.","card":"power","pin":[0.855,0.17],"scene":{"pic":"living/pics/scene-power.webp","look":"03-03","shot":"fins","focus":"45% 50%","lap":120,"spots":[{"at":[0.49,0.4]},{"at":[0.13,0.36],"side":"left"},{"at":[0.64,0.46]},{"at":[0.83,0.58],"side":"left"}]},"proof":{"pic":"living/people/power-proof.webp","place":"NASA's Kilopower reactor","when":"Tested in {krusty_year}","head":"A reactor built for Mars","credit":"Photo: NASA Glenn Research Center (public domain)"},"quiz":[{"q":"In 2018's global dust storm, how much of a normal day's energy reached Opportunity's solar panels?","a":["About {opp_pct}%","About half","About 90%"],"why":"Its panels fell from {opp_hi} to {opp_lo} Wh a day. Arcadia's reactors never notice a storm.","more":"In {trick_date}, InSight's team trickled sand beside a dusty panel so the wind would carry the dust away with it, winning back {trick_wh} Wh a day.","cite":"03-03 F-02, F-16","from":"problem","fig":0,"icon":"sun"},{"q":"Why does each reactor sit in a pit under a mound of soil?","a":["The soil keeps its radiation in","To keep it warm at night","To hide it from the wind"],"why":"Buried, a unit needs a keep-out ring only {buried_m} m out, instead of {fsp_dose_km} km on open ground.","more":"Nuclear power in space is not new: the first reactor in space, SNAP-10A, flew in {snap_year}, made over {snap_w} W for {snap_days} days, and is still in orbit.","cite":"03-03 F-07, F-10, F-12","from":"fix","fig":0,"icon":"shield"},{"q":"Of every 100 units of heat a reactor makes, about how many become electricity?","a":["{p_eff}","90","50"],"why":"NASA's {o22_kwe} kW design makes {o22_kwt} kW of heat for {o22_kwe} kW of electricity. Arcadia sends spare heat to its wells and homes.","more":"The South Pole station runs on {sp_gens} generators of {sp_kw} kW: one runs, one waits ready to take over, and the waste heat warms the station.","cite":"03-03 F-09, F-20, G-11","from":"why","fig":0,"icon":"bolt"}],"notes":[{"beat":"fix","text":"The city always keeps about {spare}% more reactor power than it needs, and never fewer than two spare units, so any unit can rest for repairs.","cite":"03-03 G-05"}],"from":"From the reactor field","everyday":{"title":"A day with power","items":[{"time":"06:40","head":"Warm before sunrise","text":"The reactors never sleep, so the house is warm and bright long before the Sun is up.","tag":"{kpp} kW each, day and night","pic":"living/pics/power-city.webp","pos":"50% 45%"},{"time":"13:10","head":"The panels drink the noon light","text":"Out past the fuel plant, fields of solar panels soak up the midday Sun and turn it into fuel for the ships home.","tag":"{f_sun_pct}% of Earth's sunlight","pic":"living/pics/power-far.webp","pos":"50% 50%"},{"time":"20:30","head":"A storm outside, a film inside","text":"Dust is turning the sky brown out on the plain. Indoors nobody notices: the reactors run exactly the same.","tag":"Same power every day","pic":"living/pics/em-power-mars.webp","pos":"30% 50%"}]}}