Why dosnt NASA put plants on spaceships?

Question

do they already or why dont they? It would provide oxegon and breath in carbon dioxide.

Answer 1

Volume problems and they weigh too much.
But water is the key to the problem and its solution.

It is very expensive to get anything into space and plants require water. That water is dense and hugely expensive. It is cheaper to pay to ship the oxygen up then to pay to ship up the required water to feed plants that could make a decent contribution to the oxygen supply on the Space Station.

Now if you increase the scale and make a farm then it becomes more practical. For example algae isn't all that good to taste, but you can live off of it. If astronauts grew algae on a long space voyage then they would get the CO2 conversion to oxygen effect and the food benefit.

A long term space colony would use plants to recycle the oxygen because if a little gear breaks an entire eco system won’t break down. If you have a minor error in your CO2 scrubbers then you can have some severe problems.

The International Space Station is a foothold in space, more of a toehold. Its scale is too small for anything except research to be economical. There are manufacturing techniques and drugs that can be made in space that can’t be duplicated on the Earth, but we aren’t doing it yet because we don’t have the capability to sustain a space industry.

A true space colony would have an ecology which means plants and animals (maybe only humans, but still animals). Then we can imitate the cycle of ecology that keeps live on earth running. Crops could be grown to harvest for food while the plants would convert CO2 to breathable oxygen. They would also naturally recycle used water, purifying it. The problem with this equation is water. You still need to put water into the cycle and currently we don’t have any source of water except on earth. Water is dense and heavy, unlike gases it can’t be pressurized to fit in a smaller container; it is incompressible. So shipping it into space is hugely expensive. Humans need it and we currently can’t afford to have plants competing with us for it. The efficiency and savings from using the plants won’t make up for the lack of water, because without water both of us will die.

NASA is looking for water in space. If they find it on Mars then life could exist. If they find water on the Moon then a stable lunar colony could be built. The only other place we know where water can be found is in comets and the ice rings around Saturn. Saturn is too far away to go to for water, but comets have a habit of coming pretty close to the earth. If astronauts could catch a comet and harvest the water from it that would be a tremendous benefit; all that ice in space could be used to drink, to flush, to wash, and then broken down into hydrogen fuel and breathable oxygen. A source of water in space would be worth 10 times its weight in gold, if we could get to it. It would be worth so much because it is so hard to get the water up into space to begin with. Currently that is the biggest limit on space exploration. Not the oxygen, but the water. It is cheaper to bring oxygen up into space than water.

It might even be more effective to break water down into pure hydrogen and pure oxygen and then pressurize that and carry the lighter components into space. Except the process of breaking down water is very energy intensive and handling pure oxygen and pure hydrogen is deadly. As a gas one can explode the other is the key ingredient for a fire. As a liquid they both can kill if touched, they can destroy normal materials and are still dangerous.

The holy grail of space travel is to get the price down to $50/lb. Once we have it that low we can economically live in space. Until then we can only visit for a short time. Even a moon or Mars base is going to require a lot of water and the expense of getting it there is a major factor that is holding us back.

NASA invented the science of hydroponics so they could grow plants in space, even in a zero-g environment. They found that they can grow plants in water with no soil, just add the proper nutrients and they will do fine. The experiments have been done on earth and in space. The concept is proven and workable, IF we could get enough water to support it. When a plant or a human takes in water they use it to operate, move things around, to form structure, and to create part of them. Both sweat, but both consume more water than they ever give out. Water is vital for life, next to oxygen it is the most required component of life. Next to carbon dioxide water is the most vital ingredient for plants. We need the water and currently it is too heavy to lift enough water to make it worth working with plants.

Answer 2

To date, the only plants that have been carried to space are for experiments (much like what they've done with small animals), due to the weight and complexity of using plants for a spacecraft's life support system. Right now, it costs, on average, about $7500 to put a pound of weight into orbit. Closed-loop life support systems like you see in sci fi movies have not been perfected yet, which is why the preference is to test them on the ground, before launching something so massive and complex into orbit.

Answer 3

Plants need a lot of water, which is expensive and difficult to transport on space craft (at this time).
Even hydroponics (which don't require soil, which is very heavy to launch) still requires a lot of water, nutrients, and equipment.
Plans for long-term manned missions to Mars and the outer plants have included plants for oxygen production, CO2 absorption, etc. But nothing has been built yet, since we don't have manned missions scheduled and in progress yet.

Answer 4

They do.
Plants are not a perfect solution to the problems you mention. The problem is providing the proper light for the plants. Either clear walls need to be provided which are heavy compared to walls made from other other materials or power consuming lamps.

Answer 5

Plants also use oxygen, require water and add weight. To get a meaningful yield of oxygen from plants on the spacecraft would require too much plant matter. It's easier to add a little more oxygen to the tanks.

Answer 6

I guess because they don't want to waste the weight limit on plants. They would also have to bring more water, which would also add to the weight.