Recent comments in /f/askscience

speederaser t1_j1bd4w4 wrote

Reply to Why do we use phase change refrigerants? by samskiter

My company makes the world's smallest "practical" refrigerator. I say practical because you can indeed make smaller refrigerators that use thermoelectrics or other methods, but they are not useful because they are too slow to cool or don't work if the room gets slightly warm or slightly humid. For those reasons we use a phase change refrigerant like just about every other refrigerator on the planet, but the smallest one in the world.

This is the application of all the other comments in the thread. For practical reasons, like size, energy density... us engineers usually end up choosing phase change refrigerants.

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QtPlatypus t1_j1bb7my wrote

Reply to comment by BigWiggly1 in Why do we use phase change refrigerants? by samskiter

>Water vapor is useless for space cooling, because it condenses at 100C. We'd have to use liquid water for cooling instead, which wouldnt be able to use the carnot cycle.

Though cooling is just the other side of warming. Steam is a great way to heat a room.

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Interesting-Month-56 t1_j1baq0t wrote

Reply to Is accidental transportation of microbes to Mars bad? by Responsible-Maybe912

For the purposes of studying extraterrestrial environments and clean experiments about the origins of life, not having terrestrial life on board is important.

For the purposes of studying how well terrestrial life can adapt and thrive in nonterrestrial environments, having them provides a natural experiment.

The hard fact is that it’s almost impossible to exclude terrestrial bacteria from any space craft. So for now, scientists try their best, and eventually it won’t matter.

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zekromNLR t1_j1ba8rm wrote

Reply to comment by Danne660 in How do fusion scientists expect to produce enough Tritium to sustain D-T fusion (see text)? by DanTheTerrible

Well, you would need a quite large inventory of lithium in the reactor to capture a large fraction of the neutrons, but it would only be consumed at a slow rate. Even assuming only 20% of the fusion power comes out as net electricity output (the rest being either lost as waste heat or needed to keep the fusion going), a 1 GW D-T fusion power plant would consume only about 275 kg of tritium per year, which would correspond to a lithium consumption of about 600 kg per year, depending on the specific mix of lithium isotopes.

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zekromNLR t1_j1b9g5z wrote

Reply to comment by Splatterman27 in How do fusion scientists expect to produce enough Tritium to sustain D-T fusion (see text)? by DanTheTerrible

Those processes are how a D-T fusion plant would capture energy. About 80% of the energy output of D-T fusion is in the neutron, and the other 20% are probably required to keep the plasma hot anyways. As the neutrons slow down and go through nuclear reactions in the breeding blanket, they will give up their kinetic energy as heat, which can then be used to boil water and drive a steam turbine.

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