Design for waste water in space?

[Rjeffery]

How would the urine and feces of a long duration space voyage be treated. For example, to Mars and back. Would there be enough light and heat for biomass composting? How about for a 'generation ship' to, say Alpha Centari?

 

[rocketdoc]

I would think that because mass is such an issue still, in spacecraft design and mission planning, that I would think that the urine could and would be recoverable, but the feces would probably be discarded. Taking the "hit" on the mass of a feces reclaimation device would not be worth the effort.

Most of what constitutes feces is no longer of much value.

And before someone says that it's not environmentally friendly, just remember... space is a very big place.

PV

 

[Rjeffery]

I can understand discarding 'solid' waste when resupply is easy ie the shuttle and International Space Station, but when resupply is not possable...

Short term, dilution may be the solution by casting (pun intended) the feces into space, but for the longer duration flights a method of recovery and recycling needs to be found, I would say.

 

[morgothia]

on that long of a fligh5t the bio mass would be reused due to a few reasons one carbon is lost to us easting the plants and the feces would renew that 2 the nitrogen that is also found in feces would help the soil (since you will have to grow food for that long of a trip)



morgothia

 

[IRstuff]

Mars mission scenarios involve pre-positioning supplies on Mars for the ground mission and return. Therefore, the inefficiencies of the outbound trip are not a factor as far as recovering substances from solid waste, although the water would still be recovered.

TTFN TTFN

 

[rocketdoc]

On a trip of the duration to Mars, I would still say that the complexity and material components neccessary to reconstitute the carbon and nitrogen components of POO would not be worth it.

 

[jsalls]

I know this is a bit disgusting, but I remember hearing in the news several years ago that the japanese had developed a process for turning fecal matter into food material in order to reduce sewage waste. The report was that it was both nutricious and tasty although how they found a taste tester for the previous failed batches is beyond me.

I know that they have had filtration systems to recover urine as water for a long time.

I would think either process would have some unusable by products. At least I hope either process would have some unusable by products ;-).

 

[delta2112]

On trip to Mars, for sure is not worse to recover the solid part, and only the water would be OK. Moreover the plant to recover water is cheaper and smaller and lighter. But for an Alpha Centauri trip, for sure they will need to grow food on board of the ship (much, much larger space craft) and as such they would need to recycle everthing.

 

[Rjeffery]

these are all excellent thoughts, but...

How would you go about designing the system?

i.e. Would there be enough light and heat for biomass composting?

 

[delta2112]

As an engine for such large space craft designed for log trips aka Mars, Alpha Centaury, etc has to be electric (ionic, or plasma, etc.) the ship has a nuclear power generator. Guesing further that this will be designed a little bit further in future from today, it means we'll deal with a fusion power plant.

This means enough electrical energy, so enough heat, light and specific impulse to accelerate the ship.

There is one more thing regarding the power after leaving atmosphere, and friction or aerdynamics are not issues any more, very very large solar pannels can be used to harvest the Sun's energy even at large distances from it.

 

[samienela]

In the past decade NASA has had several composting projects but they are mostly geared toward processing of agricultural residues, for the scenario where the astronauts/colonists grow their own food. There is also some current work on freeze drying feces, but the goal is not so much resource recovery as stabilization so that the feces won't decompose and release toxic or offensive gases. The place to see reports on NASA research is the NASA task book site. From the

http://www.nasa.gov

site go to the "NASA research opportunities" site for the office of biological and physical research, and look for the taskbook database. It has yearly reports of nearly all NASA funded external research on life support and other biological topics, physics and materials science, going back to 1995.

By the way you don't need light and heat for composting. You need oxygen to support aerobic microbial growth, and and a reasonably well insulated enclosure so that the biochemical reactions will raise the temp high enough to kill off pathogens, and a dehumidifier downstream to condense out the water produced by metabolism and evaporated off of the compost pile.

Someone asked about power. Any long term mission where the astronauts grow their own food will have a huge power plant because the electrical-energy-to-food energy yield under artificial lighting is something like 1-2%.

Rjeffery asked about recycling nitrogen and carbon from feces. Most of the nitrogen we eat goes out in the urine and most of the carbon, in CO2. It would be nice to recover it, but not necessary except for really long term missions or very large crews.