As Jim argued above there will be plenty of time until MCT will transport 100 people. That is because the station/colony cannot accept that many. So there will be plenty of time to optimize the system and make it reliable. Maybe 4 systems are needed but there will be 5 providing failsafe. Closed loop may well be worth it even if it only recovers all the oxygen and discards the methane like in the ISS.
So not in the hypothetical, but in reality - what technology do you propose for a closed loop ECLSS for MCT? Even for a crew of 10-20.
Closed space composting, which gives you good fertilizer for crops at the settlement. In one test using stored solid human waste it took about a year to get nice, fluffy and pathogen free uber-fertilizer. Food waste is faster. Urine is relatively pathogen free, and after 30 days of 'ripening' pathogen free. Careful design, of course.
The talk of this for 100 person MCT is needless. Any life support systems will have been proven out on early vehicles before they get to colonization. There will be smaller 4-8 person vehicles for the initial explorations. Then there will be larger vehicles for the initial settlements that will handle 2 digits worth of passengers. It will be years before infrastructure on Mars can handle an increment of 100 people. Until then, there will be smaller vehicles with less passengers making the rounds
While you're recovering metabolic products, you also need to figure out a way of dealing with the accumulating sodium, calcium, magnesium, chlorine, potassium, phosphorus, and nitrogen that you need to separate out from the waste stream.
Agree completely - which makes that 100 comment pretty pointless.
Metabolic processes produce CO2 but also a lot of H2O. The necessary hydrogen to process CO2 would be produced by electrolysis of H2O. The endresult of the reaction food +O2 will be methane CH4 plus O2. This process would not be closed though because the ratio of C and H would be closer to CH2 than CH4 because of longer chaín carbohydrates. To close that gap you would need more H2O to electrolyze. With enough energy from the solar panels the system could produce not only CH4 methane but also O2 that could be added to the LOX in the tanks. That way most of the food and water consumed during the flight would end up in the propellant tanks.I am not sure though if that would be the optimum solution overall. It really depends on availabel energy from the solar panels.
Metabolic processes produce CO2 but also a lot of H2O. The necessary hydrogen to process CO2 would be produced by electrolysis of H2O. The endresult of the reaction food +O2 will be methane CH4 plus O2. This process would not be closed though because the ratio of C and H would be closer to CH2 than CH4 because of longer chaín carbohydrates. To close that gap you would need more H2O to electrolyze. With enough energy from the solar panels the system could produce not only CH4 methane but also O2 that could be added to the LOX in the tanks. That way most of the food and water consumed during the flight would end up in the propellant tanks.
Solar panels have a low efficiency of conversion of sunlight to electricity, and electrolysis also has a low efficiency of use of electrical energy. Consider a solar concentrator to make direct use of heat energy, which can also take advantage of the UV component of light:-https://en.m.wikipedia.org/wiki/Water_splitting#High-temperature_electrolysis
Quote from: MP99 on 10/04/2015 10:42 amSolar panels have a low efficiency of conversion of sunlight to electricity, and electrolysis also has a low efficiency of use of electrical energy. Consider a solar concentrator to make direct use of heat energy, which can also take advantage of the UV component of light:-https://en.m.wikipedia.org/wiki/Water_splitting#High-temperature_electrolysisSounds like a very complex machinery to have on a spaceship.
I am not sure though if that would be the optimum solution overall. It really depends on availabel energy from the solar panels.
The ECLSS on MCT should be as simple as possible. The flight time is short, the crew will be small until much later, and there will be plenty of mass available for supplies.
It sounds like this is a version of the standard electrolysis that you'd use anyway, but just at the focus of a fairly simple reflector.On the basis that electrolysis is part of the sizing of the solar panels, this reduces their size by more than the surface area of the reflector. (Assumes that electrolysis runs close to 24x7.)As an external system, I think this also reduces the radiator / heat rejection required from inside the hab.Cheers, Martin
Quote from: meekGee on 10/03/2015 10:27 pmSo not in the hypothetical, but in reality - what technology do you propose for a closed loop ECLSS for MCT? Even for a crew of 10-20. First, water recycling. There is a lot of water in human waste that needs to be recovered plus water from controlling humidity of the air. That includes water metabolized from hydrogen in the food but also the water already in the food. Second, a mix of oxygen production from electrolyzing water plus at least the hydrogen produced in the process can be used to process CO2 to methane and oxygen. If it is worth liquefying the methane and add it to the fuel or just dump it over board like on the ISS is an engineering exercise I don't want to do.Early flights could have experimental setups that don't endanger the mission if they fail somewhere on the way, only maybe cause some inconvenience. Evolve them until they are reliable enough to use on a 100 person MCT.