so this article is about temperature regulation for a spacesuit on mars. we assume you want to walk around on the outside, doing light work like checking the terrain and maybe also heavy work like constructing houses and such.

there's 4 major ways to lose heat:

• radiation
• convection (through the wind)
• evaporation (water loss)
• conduction (through the ground)

the share of each way to heat loss on mars is as follows: assuming -60°C external temperature, almost all of the heat loss is through radiation; there's a very thin atmosphere (therefore almost no convection losses), we assume no evaporation losses (the suit is airtight), very small conduction losses (small feet area).

so sorry for posting chatgpt output here, i checked the text however and it's true, but it's neatly summed up and i'm too lazy to rephrase.

sources for the details:

• Stefan-Boltzmann-law
• Emissivity

emissivity of materials can vary from 0.03 to 0.99 so you can basically choose your emissivity. depending on the emissivity, the heat losses will be different. there's an almost linear connection there.

so for a typical white spacesuit, the losses will be around 600 W of heat on average; which can be reduced by an order of magnitude if you use tin foil as the surface material instead.

meanwhile the average human metabolic output is around 250 W throughout the day (assuming light activity like walking around), and it can peak at around 500 W during heavy work activity.

so you could choose a proper material to have around 400 W of heat loss on average, so you wouldn't overheat if you work hard but also not lose too much heat if you just walk around; in the latter case, you'd have to supplement the heat with a technical heat source, such as resistive heating. so the spacesuit would also have a battery attached to it as the power source; if you want the battery to last an hour before you have to change it for a new battery, it would have to have a capacity of around 100 Wh. if it's a Li-ion battery, it would have to weight around 400 g to provide that energy.

a person requires approximately 1 kg of oxygen a day.

how to calculate this: a person requires roughly 8 MJ of chemical energy a day, which is about 0.5 kg of bread. to oxidize this in a 2:1 ratio of oxygen:carbon (CO2), you need 1 kg of oxygen.

so if you use some kind of face mask to supply you oxygen, you might inhale 200 mbar of pure oxygen. however, the body cannot take that all in all at once, so the air you exhale has like 160 mbar of oxygen still (that the body could not absorb) and 40 mbar of exhaled CO2. at least that's how it works on Earth. (i should link a source here, but i'm too lazy to look one up, i write this down from memory)

so inhalation absorbs about 20% of the available oxygen. so if you require to take in 1 kg of oxygen in a day, that means that 5 kg have to be provided in total. so how big would the flasks have to be?

if a flask is 1 liter in size, it would contain 1 g of oxygen at 1 bar, but if we increase the pressure, it can hold more. obviously, we can't increase the pressure to 5000 bar to make it hold 5 kg of oxygen at once, because the highest pressures that can be safely used in industrial settings are 200 bar, and that's already incredibly high. so if we only put 50 bar of pressure into the flasks, one flask would hold 50 g of oxygen, which is about enough for 15 minutes, before you have to change it again. (we need 5000 g of oxygen supply in a day of 86400 seconds, so roughly 50 g supply oxygen for 864 seconds which is almost 15 minutes).

source

the worst insult you can throw at somebody today is "you're a child". because in the minds of the US citizen, the child is the worst things in existence. schools exist to quarantine them, to remove them from society, to make them "proper" humans, adults, in other words.

the reason why the child is considered the most despicable object in US mainstream culture is because the child represents nature, the thing that is a direct offspring of biology, instinct, and whatever we consider "uncultured uncivilized being". in the US, the child is like a piece of dirt, or clay maybe, that has to be sculpted and burned into porcellaine before it's considered worth anything. even more, the child - through its playful instinct and lust for life - might even represent the animal instinct that has been so successfully repressed in every Grown-up human. and we cannot accept what was never accepted about ourselves.

unfortunately i lost the source on these ones.

CivitAI

SpaceX conducted another successful Starship launch test yesterday evening.

You can watch the full, 1:40:00 footage here:

Invidious YouTube

I'd recommend watching it, it's a well-done video documentary, not too long, with good views.

how should the world's economy develop? what companies should be developed? how should the profit be distributed? should it be illegal for companies to make a profit at all?

(note that i think that it is generally unavoidable that some companies make some profit, the grey area on the image of the supply-demand diagram (or rather quantity-price diagram) is the profit, and that would only be zero if all companies have exactly the same production costs per unit.)

source

what do you think of it? how accurate is it?

ok so because there was a post on this comm 10 minutes ago about somebody wishing that more happens here, here's my take

what's the probability of aliens happening to be physically close to Earth? rather low, i guess. here's why

https://en.wikipedia.org/wiki/Great_Oxidation_Event

if you would please consult the diagram

it says that live has taken about 4 billion years to develop. meanwhile most of human culture and arts and science has developed within the last 10k years which is roughly one millionth of the entire time. i think that humanity will spread to other planets in a high velocity in the near future so if we encounter another planet, what are the chances of them being pre-singularity (the time that we learn to settle other planets)? idk

but the chances of meeting them while they are developing science is rather low, we'd have to meet them in a rather narrow maybe 10k years slice of time. rather unlikely. if we meet aliens, they're either really dumb or very technologically advanced.

the same the other way around: they either met us in the very distant future and are therefore a normal part of today's life, or they're not likely to come here anytime soon.

The report examined so-called “firm” renewable systems – combinations of solar panels, wind farms and battery storage capable of providing round-the-clock electricity.

In regions with strong sunlight and wind resources, solar power paired with batteries now costs between about €50 and €75 per megawatt-hour, the report found.

That compares with about €60 to €75 per megawatt-hour for new coal plants in China and more than €88 globally for new gas power.

A steep drop in battery prices has helped drive the change. Since 2010, the cost of battery storage has fallen by 93 per cent, according to IRENA, while solar panel costs dropped by 87 per cent and onshore wind costs by 55 per cent.

currently enjoying some time in a nature camp with some friends :) u should do the same

Most countrysides look somewhat like that. At least the one i was forced to grow up in. Sure, there are lots of plants but nevertheless the land is ecologically dead because there's only a few species (mostly 3 different subspecies of corn). Sure there are some trees but i think the trees feel as lonely as i did when i lived there.

If you want to live in nature, go to the mountains or some place that has large bodies of water nearby (lakes, rivers, ocean). That's where the actual life is.

It's because of a mixture of landscape reasons. Large flat areas are attractive to farming, so that's what's being done. On the other side, mountains are unattractive for that because the big machines can't drive over uneven soil. Similarly, large waters host a ton of biodiversity because water is the origin of all life, and you can really feel that. Just give it a try.

This is huge!

Spirulina, a type of algae, is considered one of the best sources of food on Mars, because it can grow in small containers and doesn't need big greenhouses. It is also very nutrient-rich, containing both lots of energy and protein.

However, vitamin B12 so far has been assumed to only exist in animal food products, such as beef and dairies.

This research project investigates genetically modified spirulina algae that contain levels of B12 comparable to beef!

This is not only a big breakthrough for food security on Mars but it also opens up the door another step to the broader approach of genetically engineering food sources on Mars. What might be next?

Brandolini's law (or the bullshit asymmetry principle) is an Internet adage coined in 2013 by Italian programmer Alberto Brandolini. It compares the considerable effort of debunking misinformation to the relative ease of creating it in the first place. The adage states:

The amount of energy needed to refute bullshit is an order of magnitude bigger than that needed to produce it.

The challenge of refuting bullshit does not come just from its time-consuming nature, but also from the challenge of defying and confronting one's community.

cross-posted from: https://lemmy.zip/post/63552288

Highly recommend any art/sculpture fans go to the Hakone Open Air Museum.

if you think about it, boats can't go above a certain speed (hull speed) and airplanes can't go below a certain speed (or they would stall). Really makes you think

::: spoiler I'm talking about this person btw.

:::

And i would kindly ask to request whether we could maybe remove them? It's a bit visually distracting while scrolling through the community feed as it's a bit visually catchy. (Or at least put the image behind a spoiler.

(The sidebar is always visible on the default Lemmy browser UI.)