A study on the technical feasibility of the Mars One mission plan was published by MIT in September 2014. A copy of the report can be found here .
The study was widely reported in the press as demonstrating the infeasibility of the Mars One plan, that the first astronauts would ‘suffocate, starve, and be incinerated’, the crew would die within 68 days from excess oxygen. In simple terms the study looks at the logistical requirements of the project and the material balances in the habitat, in particular the oxygen balance, under two scenarios, one where all the food is brought from Earth, and the second where food is grown within the habitat.
It is true that the study does predict death within 68 days for one scenario, but this is not a balanced reflection of the report, nor are the results from the study necessarily a fair reflection of the Mars One proposal for the life support scheme. What the study does demonstrate is just how little definition and thinking the Mars One project have put into their proposal.
The MIT study is a thorough and well written piece of work, and stands head and shoulders above anything published by Mars One, but it is not beyond criticism. The study takes the relatively sketchy definition that Mars One provides and applies it without reservation; it also fails to drive home a basic limit to growth of the colony.
One finding of the report is in truth a trivial one, but is nonetheless a comment on the Mars One project that they continue to gloss over. Mars One proposes to build up numbers on Mars by sending crews of 4 people at two year intervals. In the absence of food production on Mars and the absence of any manufacturing capacity, then all equipment, materials, spares, and food has to come from Earth. With each successive crew arrival, the amount of material that has to be transported to support the colonists simply increases in a linear fashion.
At some point the ability to provide will reach a limit beyond which the colony cannot grow, due to the sheer mass and cost of transport. To progress beyond this limit, the colony has to grow its own food, but far more importantly, manufacture its own equipment and spares. What the MIT study does do is to put some numbers to this, based necessarily on a lot of assumptions. The MIT figures show that even if growing food in the colony, it is the ever increasing need for manufactured goods that is the problem. MIT estimate that the total weight of material required to be sent with the fifth crew is some 85 to 95 Te, around twice the mass required for the first crew.
An interesting and possibly counter-intuitive result from the MIT study is that growing food within the colony requires more mass to be transported than relying on food shipped from Earth. As the report states, producing food does not have a payoff for at least two decades. This is even assuming that effective food production can be established from the first crew arrival, which may well not be achievable.
The problem of manufacturing on Mars is waved away by Mars One by invoking the magic wand of ‘3-D printing’. It is surely more than a little fanciful to plan that in the near future a mechanical device (or even group of devices) can be used, on Mars, to replicate the full range of manufacturing required, even if some limited manufacture was possible (perhaps the odd plastic gasket, or metal widget) . Most of the systems in the life support system will be highly specialized, using sophisticated technologies. It will not be bolts and nuts that are required but replacement valves, actuators, rotating machine parts, electronics, catalysts, absorbents, pump parts, springs, motors, instruments, etc..
The second finding in the report concerns the habitat oxygen balance in the scenario where plants are grown to provide food. The study found that the crew would die after 68 days due to low oxygen partial pressures, which (paradoxically) would arise from to the need to vent gas from the habitat because of the production of oxygen from the growing plants. The driver behind this is straightforward. With the amount of plant growth assumed by the MIT team, the rate of oxygen generation within the habitat would exceed the rate of usage, requiring that gas be vented to the external environmental to prevent the habitat oxygen concentration from rising too high.
This uses up diluent nitrogen faster than it can be supplied, and after some 60 odd days the nitrogen supply runs out. The habitat pressure then gradually drops due to leakage losses, while the molar fraction of oxygen in the air rises. The crew die from low oxygen partial pressure; hence the media headlines.
Does this study therefore show that the crew are ‘doomed to die on Mars’? They may well be, but not from this. The principle of the Mars One life support system is perfectly reasonable, and in the absence of plant growth, and assuming that the units actually work reliably, then the system could be expected to keep the crew alive.
The underlying issue is that this study shows just how little thought Mars One had put into their proposal. They continue to make great play of the concept of growing plants to provide food, and at least up to the issuing of this study insisted that growing plants would start with the first crew. In the Paragon report (issued after the MIT study) this is played down; the Paragon study assumes that initially plant growth will have ‘minimal impact’ on the life support system operation. The report actually says ‘minimal impact to the design and operation’. This may have been added as an afterthought, since clearly the design of the life support system has to take account of the impact of growing plants at some clearly defined level, otherwise limitations in the system could preclude growing plants at all. As indeed is the finding from the MIT study.
So one underlying problem with the proposed Mars One / Paragon life support system is that it is predicated on the assumption that there is no oxygen generation within the habitat. A means to remove oxygen is required. A simple question is this: why did the Paragon report fail to address the issue of oxygen generation within the habitat?
Cygnus Resupply Ship to ISS - 2017 [Credit : NASA]
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