Why can't astronauts just bring plants into space with them so they can breathe off that?

Question

Why can't they just bring up some cactus (i think cactus are plants that give off a lot of oxygen) and leave them there so that when some astronauts switch shifts on the space station they can take up more space with other stuff instead of those oxygen tanks? (obviously you'd need them as back up, but in theory how come... How many plants would you need i guess is moreso the question. I'm asking b/c if hypothetically Deep Impact or something happens and i gotta be in a bunker i wanna know how many plants i need to be able to keep breathing fine.

Answer 1

Because it takes a lot of leaf surface and cactus are not a good source of leaf surface.   Under no gravity, growing plants, keeping water in place, circulating the water oxygenating it, etc. requires a lot of hardware and weight.  Much more than cramming oxygen in a tank and treating the air for CO2 and moisture.   If plants were taken along, the shuttle would have to be constantly aimed at the sun and the plants protected from freezing when in the dark (more hardware).    The ideal plants would be leafy vegetables that could be eaten, like spinach, that don't have large stems and grow their leafy area neatly.

  Because of the need to control the water, most plans for plant supported oxygenation call for algae in closed glass piping from which the algae is filtered and processed for food.

Answer 2

major major problems with that. first of all, plants need Co2, water, and sunlight. water is VERY heavy to carry on a rocket. heavier than oxygen. add the plants on top of that, and you are just weighing down your space craft more. second, there is no air in space. there is no Co2. and cacti, or any other plants for that matter, don't create enough oxygen to fufill the needs of the astronautes on the ISS. if i brought 50 cacti with me, tons of Co2 and the right amount of sunlight, and also plenty of water... more water than astronautes already take with them, i would have to wait more than a 10 years for the entire spaceship to have enough oxygen for a 2 week mission.

if you want to plant plants on the moon, there is no way. again, no Co2. we can't even add Co2 because it doesn't have an atmosphere to contain these gasses. and they need liquid water, and the moon doesn't have that. as for mars, again, no way. its way too cold and has no running water. does it have Co2? yes it does. it has plenty of Co2, but no liquid water, and its too cold. and if we were to load over 90% of the planet with plants, gave them water and everything, it would take thousands of years for the planet to be rich in oxygen.

its cheaper, easier, and a lot simpler to carry O2 tanks.

Answer 3

Plants don't live in space so taking them in space is of no use.

Answer 4

My guess is that it has to do with the cost of bringing plants on board, along with water to keep them alive.

As my high school physics teacher put it, to figure out how much it costs to send something on a space shuttle, place the item on one side of the balance. Load up the other side with twenty dollar bills. Add a $100 bill every now and then for good measure.

It's much more cost effective to bring compressed oxygen gas than to bring enough plants to live off of. Plants might be better for deep space travel, where you won't be able to get regular shipments of oxygen.

Answer 5

im no biologist, but i think the oxygen that plants breathe out are the same oxygen atoms that came from the water in the soil. therefore, since you have to bring water for the plants, you could just take the water to space, and perform electrolisys on it (which means to separate the hydrogen and oxygen in water molecules by using an electrical current) therefore avoiding the hassle of keeping plants in the space station.

Answer 6

an intriguing question, but perhaps you are putting it wrong.

the ISS isnt a cottage with windows that face the sunrise...  you can't just bring plants, you need everything a plant needs.  BUT, what you COULD do is have one ISS module set up as a greenhouse; it can have its own solar panels and be connected to the rest of the ISS by only an air conduit.

now, why didn't anyone try that?

my guess is... each module is restricted to Shuttle launches and the NASA bigwigs thought we had plenty of shuttles... showing you CAN be a moron and be in charge of a gov't space agency.

Answer 7

At night (or in the dark), plants would produce a lot of CO2 and that would be dangerous