Random Propulsion idea

[bellino]

Now now, before you say it wont work, i know it wont. But its cool

Now, we know humans produce Co2 right? Manned spacecraft just dump it. But, what if, it could be used as propulsion?

According to a study by the United States Department of Agriculture, an average person's respiration generates approximately 450 liters (roughly 900 grams) of carbon dioxide per day.. Then times three or four people. This is 1800 liters of CO2 every day. What if it could be used for the Reaction Control System on a spacecraft?

This has advantages and dis-advantages:

1. Cheaper RCS and lighter tanks

2. refuel naturally, while in flight!

HOWEVER:

1. Since CO2 is not as dense as the regular fuel, it will be slower to turn.

But the spacecraft would still have a backup tank and re-entry tank full of the usual fuel.

DISCUSS!

[Tommygun]

I'm not sure what the current methods for removing CO2 are. They used to use absorbers to remove it and if they still do, I would imagine the weight of the equipment to separate the CO2 from the absorbers may well be much higher than the weight of the fuel you're trying to save.

It's just easier to launch more fuel and have less equipment to maintain.

[bellino]

lol, sorry

I was thinking of the dumps on the Mercury capsule... and it didnt even dump co2

[Kerbin Dallas Multipass]

Wouldnt it be more practical to just remove the C from the CO2 and just breathe the O2?

[OtherDalfite]

Wouldnt it be more practical to just remove the C from the CO2 and just breathe the O2?

That's a bit tough to do without plants .

To quote the OP, rocket fuels are used because of their ability to expand rapidly when heated and to be very reactive. CO2 is a very stable gas and trying to use it as propulsion would probably net you as much dV as blowing the hatch in a pod. Very very small amounts. In KSP, that amount might seem enough to bring you home or some other thing, but in real life you need far more thrust to do anything big, like changing your orbit.

[bellino]

Replying to this-

I guess i worded the title wrong, as this isnt an engine, but an RCS fuel.

Also now i want to find out how much dV blowing a mercury hatch would make

[DaveofDefeat]

I feel like exhaling out into space has the major side effect known as dead.

[OtherDalfite]

I feel like exhaling out into space has the major side effect known as dead.

Well, holding your breath will also lead to a side effect known as ruptured lungs and still dead!

[bellino]

Your not exhaling into space... lol

Your taking the CO2 into a tank, storing it, and then shooting it out for dV

[Temstar]

The problem is to actually extract the CO2 out of the spacecraft's atmosphere is no easy job. For short term use like Apollo spacecraft lithium hydroxide is used. Lithium hydroxide absorbs CO2, turns into lithium carbonate and releases water so the process is non-regenerative, but the system itself is pretty simple and compact. For long term solution on board space stations a more elaborate system using molecular sieves is used where dried air is forced through the sieves and the sieves stop the bigger CO2 molecules from getting through while the smaller O2 and N2 are able to fit pass the gaps. When the sieves become saturated with CO2 it's moved to the outside of the spacecraft and into the sun where CO2 is then allowed to leak away.

The regenerative system is complex enough that the two systems on ISS called Vozdukh and CDRA that use this method often break down, sometimes even together! When that happens the crew switch to back up lithium hydroxide system and go about fixing them. Considering that this system is responsible for keeping the crew alive I think it would be a bad idea to make it even more complex just to get a tiny bit of delta-V out of it.

Edited September 14, 2013 by Temstar

[dharak1]

If there was a way to extract CO2 then this may be viable for long term spacecraft like space stations.