Food and its mass

[Kimberly]

I'm designing a Mun base and I'm curious about something: how many times per year will my Kerbals need to be resupplied with food and water? It's not a topic I know very much about.

2500-3000 calories per day is fairly normal for physically active human adults, but I wouldn't know what the typical consumption for an astronaut is--they're not expending as much energy in the low gravity on the Mun. We can probably apply the normal 64% scale to whatever the right figure is to adjust it for Kerbals. A full complement for the base is 18 kerbals, two of whom are expected to regularly conduct EVAs on foot and with rovers; the rest have jobs managing the station, coordinating Mun operations and doing research but may expect to do EVAs from time to time. There is sufficient equipment available to recycle all of the crew's waste, and let's say it is 80% efficient (is that a reasonable figure?).

For transportation, my Mun base will use Cal'Mihe's awesome Starspeeder, safely rated for about 5 tons of payload. (But it's a fully reusable SSTO that can get to the Mun, which I imagine makes it cheaper to do multiple trips than to use a heavier/wasteful transport for fewer trips.) And any reasonably practicable method for reducing the mass of the food during transport is acceptable.

[Themohawkninja]

Well, smaller creatures tend to burn calories faster, and Kerbals are about half the size of a normal human adult, so that could be an issue.

[dharak1]

As the above post says, small animals burn calories faster. Spacesuits are also VERY motion restricting if you watch videos of astronauts on the moon when they fall over they can barely move and pretty much bounce around motionless. I would imagine that being very taxing so I would say that's easily another 750 calories.

[stupid_chris]

The easy solution would to get the Kerbal to be able to grow it's own food.

[magnemoe]

Should be possible to look up how much is supplied to IIS. To save weight you would want to send a lot of dried or dehydrated food as you can reuse water.

Growing food would mostly be for getting fresh vegetables.

[stupid_chris]

Should be possible to look up how much is supplied to IIS. To save weight you would want to send a lot of dried or dehydrated food as you can reuse water.

Growing food would mostly be for getting fresh vegetables.

Indeed, it's hard to grow meat. But since the diet of the Kerbals is unknown and we know Kerbin has plenty of plants and apparently no animals, I'd suggest they are probably vegetarian. Could also explain their colour, after all, flamingos are pink because of the amount of shrimp they eat.

[Kerbface]

Indeed, it's hard to grow meat. But since the diet of the Kerbals is unknown and we know Kerbin has plenty of plants and apparently no animals, I'd suggest they are probably vegetarian. Could also explain their colour, after all, flamingos are pink because of the amount of shrimp they eat.

Regardless of whether the average Kerbal is vegetarian or not, it's perfectly possible for both humans and presumably Kerbals to live without animal products, and on a self-sustaining mission, this would probably be the case, as growing animals for consumption is just a waste and in that sort of situation, one you can't afford.

[Brotoro]

Indeed, it's hard to grow meat. But since the diet of the Kerbals is unknown and we know Kerbin has plenty of plants and apparently no animals, I'd suggest they are probably vegetarian. Could also explain their colour, after all, flamingos are pink because of the amount of shrimp they eat.

I don't understand why people keep saying Kerbin has no animals when they can hear that wonderful cacophony of birdsong in the view of the space center at the start of the game.

[stupid_chris]

I don't understand why people keep saying Kerbin has no animals when they can hear that wonderful cacophony of birdsong in the view of the space center at the start of the game.

SHHHHHHHHHHHh

[Flixxbeatz]

The easy solution would to get the Kerbal to be able to grow it's own food.

The kerbals already make their own food. Using the sunlight

[Kimberly]

I don't understand why people keep saying Kerbin has no animals when they can hear that wonderful cacophony of birdsong in the view of the space center at the start of the game.

That's just the wind rustling through the trees.

Anyway, my moon base design does include hydroponics, from udk_lethal_d0se's pack. But I imagine it's not 100% efficient at recycling the crew's waste, so that some resupply will be necessary. Is the 80% I mentioned a realistic figure for efficiency?

Edit: This article says that ordinary consumption for ISS inhabitants is 3000 calories (or it was in 2004, anyway). And this article says that 3630 kg of food supports a crew of 3 for six months, meaning a crew of 18 would consume 43560 kg per year. If we assume an 80% efficient recycling system, 20% of that needs to be resupplied each year, i.e. 8.7 tons worth of transport. It may be less for a Kerbal crew. That's only two resupply missions, or perhaps one resupply mission if you really stretch the Starspeeder to its limits... That seems awfully little, really.

Edited July 14, 2013 by Kimberly

[Themohawkninja]

The kerbals already make their own food. Using the sunlight

Considering their star is modeled after our star, and our star emits primarily in the green light (which is why plants are green), and Kerbals are green, that actually makes a lot of sense.

Before anybody asks, the sun appears yellow due to some phenomena with light that is beyond me that causes the yellow light to visually overpower the green.

[Kerbface]

Considering their star is modeled after our star, and our star emits primarily in the green light (which is why plants are green), and Kerbals are green, that actually makes a lot of sense.

Before anybody asks, the sun appears yellow due to some phenomena with light that is beyond me that causes the yellow light to visually overpower the green.

Green things reflect green light and absorb light that is not green. Just saying.

[Themohawkninja]

Green things reflect green light and absorb light that is not green. Just saying.

I just woke up... although now that you pointed that out, that makes absolutely no sense, because doesn't that mean\ that plants are very inefficient?

[Person012345]

Indeed, it's hard to grow meat.

Space cows my good man.

[Kerbface]

I just woke up... although now that you pointed that out, that makes absolutely no sense, because doesn't that mean\ that plants are very inefficient?

I read some stuff about it in the comments of a Scott Manley video... seems it's a little unclear exactly why plants are green.

http://gizmodo.com/5990764/we-dont-actually-know-why-plants-are-green

Here's a little discussion of it...

Edited July 14, 2013 by Kerbface

[Person012345]

I just woke up... although now that you pointed that out, that makes absolutely no sense, because doesn't that mean\ that plants are very inefficient?

If evolution were perfect they would most likely be black. afaik we don't really know why they aren't, but it might just be the fact that achieving chlorophyll and things better than chlorophyll is evolutionarily difficult. Or it might have come from outer space and plants evolved utilizing it. But we don't really know.

[Kimberly]

Considering their star is modeled after our star, and our star emits primarily in the green light (which is why plants are green), and Kerbals are green, that actually makes a lot of sense.

What if it's a camouflage color? Kerbin is a bland shade of green almost all over, after all.

[Fuzzy Dunlop]

The first things to evolve photosynthesis were bacteria, some of these are still alive today and are purple - because they absorb green light. It's possible that these bacteria were once so dominant that most of the water only let through purple light. Then green bacteria evolved to make use of the spare purple light. Later the green bacteria became the chloroplasts in plants and at some point the plants began to dominate.

[stupid_chris]

I just woke up... although now that you pointed that out, that makes absolutely no sense, because doesn't that mean\ that plants are very inefficient?

More like the opposite, the plants's photosynthesis is the most efficient system we know. They convert literally 100% of the light they receive into energy, while our best solar panels have trouble going past 10%... And suprisingly, just to mess things up nicely, the answer to their efficiency would lie in quantum physics ._. They'd use the quantum tunnel effect to transform photons into energy and yeah, complicated stuff is involved. Viva la biology.

Although I'd like to see where you got that the Sun emits mostly in the green wave length, last I heard it emits the whole spectrum equally.

[Person012345]

More like the opposite, the plants's photosynthesis is the most efficient system we know. They convert literally 100% of the light they receive into energy, while our best solar panels have trouble going past 10%...

Where did you get these figures? a quick wiki tells me that:

Plants usually convert light into chemical energy with a photosynthetic efficiency of 3–6%.[29] Actual plants' photosynthetic efficiency varies with the frequency of the light being converted, light intensity, temperature and proportion of carbon dioxide in the atmosphere, and can vary from 0.1% to 8%.[30] By comparison, solar panels convert light into electric energy at an efficiency of approximately 6–20% for mass-produced panels, and above 40% in laboratory devices.

Photosynthesis measurement systems are not designed to directly measure the amount of light absorbed by the leaf. Nevertheless, the light response curves that systems like the LCpro-SD produce, do allow comparisons in photosynthetic efficiency between plants.

[Kimberly]

If plants converted literally 100% of the light they received, they would all be a dark, soul-chilling black.

[stupid_chris]

Where did you get these figures? a quick wiki tells me that:

IIRC, the amount of solar energy they can absorb is near 100% , but then the amount of that captured solar energy the can convert into chemical energy is far less, usually around 10%. But yeah, the whole thing about quantum tunneling is still being discussed, it's fairly new. But I remember seeing an article on it in a French scientific magazine called Science & Vie back in ~2011-2012 I found an article on it here, although those numbers aren't discussed exactly in it.

[Fuzzy Dunlop]

Photosynthesis really isn't that efficient

[stupid_chris]

Photosynthesis really isn't that efficient

The overall process, no, but the amount of light actually captured by plants is surprisingly high.