Minimum consumables requirements are something like:–Water: 2 kg/person/day drinking + 0.2 kg/person/day for minimal washing. Probably more on long trips for better hygiene–Oxygen: 0.8 kg/person/day for metabolic consumption (assumes exercise) + leaks + repressurization–Nitrogen: mostly driven by leak rates, repressurization (e.g. for airlocks)–Food: 1.8 kg/person/day (includes meal-level packaging) at ~380 kg/m3 density–Be sure to account for both mass and volume
Quote from: Oli on 08/17/2015 05:13 pmMinimum consumables requirements are something like:–Water: 2 kg/person/day drinking + 0.2 kg/person/day for minimal washing. Probably more on long trips for better hygiene–Oxygen: 0.8 kg/person/day for metabolic consumption (assumes exercise) + leaks + repressurization–Nitrogen: mostly driven by leak rates, repressurization (e.g. for airlocks)–Food: 1.8 kg/person/day (includes meal-level packaging) at ~380 kg/m3 density–Be sure to account for both mass and volumeThat's great. Sounds like my estimate of 2kg/person/day was very generous. Getting water and nitrogen from ISRU on Mars is a safe assumption. Also meal-level packaging would add a lot of unnecessary weight. For a long stay under gravity food can be stored in bulk. Maybe I should adjust my estimate from 2 kg to 1 kg for the duration of the surface stay.
If you have ever had a LRP or freeze-dried meals for hiking, you know they make an MRE look like a gourmet meal. However, it beats starving. But you have to a reliable water supply or it's like eating salty sand and gravel.Hopefully, the crew wouldn't have to resort to the emergency rations.
Why do you dismiss 3D printing as a primary source of spare parts?
Quote from: nadreck on 08/17/2015 09:02 pmWhy do you dismiss 3D printing as a primary source of spare parts?To be honest I would dismiss it for the moment too. However the food assumed by Impaler does not take into account bulk packing as we did. Also I don't see it as a valid assumption that an ECLSS completely new designed for MCT with all knowledge and experience available will need the same amount of spare parts as the present ISS systems do. It will be designed to be more robust and needing less spares. ECLSS on Mars is another item again. It is not part of what we discuss as consumables. It will be designed for Mars with completely different methods, mostly biological. More volume, more initial weight but more efficient to run for a long time.
Quote from: nadreck on 08/17/2015 09:02 pmWhy do you dismiss 3D printing as a primary source of spare parts?Because I come from a family that has been in the tool-and-die, plastic injection molding and quality control industries for 3 generations, we know that these additive processes complement but do not replace traditional manufacturing processes.Furthermore the reactions happening in most ECLSS equipment are high temperature and energy chemistry, that means metal and ceramic vessels, valves and catalysts, they can not be replaced with plastic widgets.While their is some limited potential for packaging materials to be a source of plastic feed-stocks as soon as you start talking about metallic part printing your looking at bring large amounts of metallic feed-stock, and large amounts of secondary equipment for finishing, measuring and testing the parts created.In summary 3D printing is not a Star Trek Replicator.
Agricultural systems will need to be redundant and as they are power intense there is the most potential for downtime from a disaster, needing reboot after a plant disease related flushing
MCT is not part of some MarsOne no-return suicide pact,
Even once a base is established people will rotate in and out for a long time before anyone even thinks about settling permanently. A return option MUST exist at the time the first person sets foot on Mars.
You have no idea what your talking about. If you have some notion of canned or frozen food then you've completely blown the mass budget on the food alone as that would be ~75% water, the only practical way to send food is dry and that reduces it's self-life,
You know nothing about ECLSS is you think 5 kg a day is zero recycling,
The MarsOne nonsense got shot down by MIT for exactly the same failure to consider spares.
I don't think food production via agriculture need be either complex/difficult or especially fragile.Quote from: nadreck on 08/17/2015 06:16 pmAgricultural systems will need to be redundant and as they are power intense there is the most potential for downtime from a disaster, needing reboot after a plant disease related flushingWhy power intense? Mars gets sufficient sunlight for plant growth -- probably more than, say, the Pacific Northwest temperate rainforests or England (due to clouds) which are both rather lush.It should be rather simple to eliminate all plant diseases by not bringing them from Earth. Even if this fails, plant disease doesn't usually mean complete collapse of the system, as you'd have multiple species.
Your saying an entire mining industry needs to be established to support manufacturing of spare parts, to keep the ECLSS running to keep the FIRST LANDING of 4-6 astronauts alive for multiple synods so we can postpone having to figure out how to do a return trip???
Did you not pay attention to the original premise of this tangent? I have been talking this ENTIRE time about initial landings of small numbers for exploratory purposes, you seem to be talking about Blue Mars level end-state total self sufficiency a century from now. Your scale and time range are so out of step with what I'm talking about it's like talking about how the James town settlers will will generate electricity.
Any logical sequence would consist of first exploratory scouting missions, followed by outposts with personnel cycling in and out and then finally a permanent settlement once lots of infrastructure is built up and optimum sites are found.
You seem to be throwing your lot in with Vultur and the MarsOne nonsense of immediate colonization from the first footprint. This is not going to happen, it's like saying that Neil Armstrong should have colonized the moon rather then coming back.
The one alternative I can see is if we do ISRU on Phobos or Deimos and supply many manned sorties to the surface of Mars before building the first settlements. This would still involve a permanent presence and the one reason I don't really elaborate on it here is the idea that it doesn't work all that well with the MCT model driving Mars settlement.
Yeah, these are seemingly absurd percentage improvements, however not impossible. The critical elements of the solution are rocket reusability and low cost propellant (CH4 and O2 at an O/F ratio of ~3.8 ). And, of course, making the return propellant on Mars, which has a handy CO2 atmosphere and lots of H2O frozen in the soil.The design goal is technically 100+ metric tons of useful cargo per flight, so maybe more than 100 people can be taken. Depends on how much support mass is needed per person and the luggage allowable.Avionics, sensors, communications, aspects of vehicle structure, landing pads and a few other things get better with scale, plus it is more fun to be on a cruise ship than a bus, so I suspect that the 100 people per flight number grows a lot over time, maybe to several hundred. Also, we could subsidize the equivalent of economy by charging a lot more for first class.Factor in all of the above and getting below $100k/ton or person eventually is conceivable, as the trip cost is then dominated by propellant, which is mostly liquid oxygen at a mere $40/ton (although a lot of it is needed per useful ton of cargo). That would be really awesome!