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posted by takyon on Sunday October 01 2017, @02:45AM   Printer-friendly
from the funding-needed dept.

This week at the International Astronautical Congress (IAC) in Adelaide, Australia, SpaceX CEO and Lead Designer Elon Musk will provide an update to his 2016 presentation regarding the long-term technical challenges that need to be solved to support the creation of a permanent, self-sustaining human presence on Mars.

Making Life Multiplanetary


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  • (Score: 0) by Anonymous Coward on Monday October 02 2017, @05:18AM (5 children)

    by Anonymous Coward on Monday October 02 2017, @05:18AM (#575774)

    I'm not sure why you think there would be no variety. That may or may not be the initial case but it would rapidly change. And in any case by the time it's possible for more 'regular' individuals to buy their way there, there'd certainly be a great variety. As an example, even BudWeiser is currently pursuing [space.com] efforts to be the first beer on Mars. That guarantees more will follow it as Martians become starved for a drinkable beer.

    Another issue here is that the ships themselves will also provide resources. The average American eats about a ton of food per year. So the average human probably eats about half a ton per year. Now factor in the issue that Mars has 1/3rd Earth's gravity and so there will be vastly less energy consumption, meaning you need consume even less. So let's be modest and put it at 1/3rd a ton. The BFR can pack 150 tons of cargo and they plan to launch 4 rockets to Mars on the first mission. 1 manned, and presumably 3 with supplies. Even if just one of the rockets is filled with food that's potentially 450 man years of food. Assuming an initial landing crew of 10 that'd be space for 45 years of food per person. They'll have plenty of time to setup a sustaining and diverse array of foodstuffs while you're stuffing yourself with nonpersishable/MREs.

  • (Score: 2) by takyon on Monday October 02 2017, @07:51AM (3 children)

    by takyon (881) <reversethis-{gro ... s} {ta} {noykat}> on Monday October 02 2017, @07:51AM (#575802) Journal

    Now factor in the issue that Mars has 1/3rd Earth's gravity and so there will be vastly less energy consumption, meaning you need consume even less.

    Whooaaa there! So in microgravity, astronauts would eat even less food, right? No! [nasa.gov] (oooo [quora.com])

    They need to work out vigorously to counteract the health effects of microgravity. So they end up requiring more food than Earthlings.

    Here's one estimate [mit.edu] of the daily calorie requirement on Mars: 3040.

    People burn calories even when doing nothing (aka laying on the bed with the normal force counteracting gravity) - you can burn through 1,500 calories during a 24 hour nap. They will need to exercise while on Mars to prevent negative health effects. The lessened gravity does not mean significantly lessened energy consumption, and definitely not 37.6% as much (752 calories instead of 2,000). Although if I go by your modest 0.5 to 0.33 ton thing, I guess you are proposing about 75% of Earth calories consumption. I think 125-150% is more likely, especially if it is a Mars mission and not Mars bedrest.

    Assuming an initial landing crew of 10 that'd be space for 45 years of food per person.

    How Will We Eat On Mars? [archive.fo]

    For the initial trip to Mars, the food will almost all be pre-positioned, so that it's waiting for them when they arrive. If you consider it's a 6-month trip to Mars, that food is going to be 5 to 7 years old when they get there.

    The challenge is having enough variety of foods that will last for that length of time, and will be high enough quality that the astronauts won't quit eating. There is a very real phenomenon called menu fatigue, where if people don't have enough variety or they get really bored with the food system, then they tend to eat enough to survive and not enough to thrive. We want the crew to be at top performance.

    The other challenge that we have is that the nutritional content of this food will decay over time. Even though our food packages are considered sterile, there are chemical reactions that take pace. The color is going to change, the texture is going to change, and the nutrition degrades over time. We need to know, after 5 to 7 years, how much nutrition is it really going to have left in it, and will there be certain nutrients that will be too scarce?

    [...] The military has some of the same concerns that we do--they'd love to make food that lasts a really long time for the troops, so we've actually partnered with them on some research that's being done. They're looking into two emerging technologies: high pressure processing and microwave sterilization2. The advantages to these two technologies is that theoretically they don't do as much heat damage to the food that you're processing. If you're applying less heat or for a shorter period of time, you degrade fewer nutrients. And if you're starting at a higher level of nutrients, you can end with a higher level.

    Now we can ignore menu fatigue (drink Tang or die, asstronauts!) and play around with the numbers a bit, but it seems clear that not all of the food sent will be as usable or nutritious after 20+ years. Sending 45 years worth would just be a waste of mass. It could be better to use some of the available mass to send robots to build a working greenhouse, as big as possible, to produce fresh food before astronauts ever set foot on the colony.

    If your colony can't get a single measly resupply from Earth within 45 years, given that under current plans [recode.net] the cost of getting mass to Mars is expected to fall over that time period due to heavy reusability and economy of scale, then Earth is probably dead and you'll have really wanted to build that greenhouse and become self-sufficient ASAP.

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    • (Score: 0) by Anonymous Coward on Monday October 02 2017, @09:41AM (2 children)

      by Anonymous Coward on Monday October 02 2017, @09:41AM (#575829)

      Lots of great information and sources. Thanks! A couple of things immediately stood out to me. In the first PDF from NASA, they state astronauts use an average of 3,500 calories a day. Then the response on quora (an apparent employee of NASA) suddenly changes that to 2600 (+/- 600) calories. That is quite perplexing. He also states that their "appetites" do decrease after a couple of months with no elaboration. Is that appetite or caloric intake? To what degree? Is the change is linear, a plateau, or what. Such a tease. The paper that 3040 calorie MIT article is based upon is here. [sciencedirect.com] The source for their estimation lays out a day as:

        - 8 hours sleep

        - 2 hours intensive exercise

        - 8 hours nonstop outside work on EVA days

        - All remaining time (6-14 hours) is spent on nonstop inside work that uses an unstated aggregate caloric consumption rate over the tasks such as "performing science experiments, preparing meals, or harvesting and replanting crops."

      In other words you engage in physical work or exercise during every single waking hour. I certainly agree with you that it won't be a "Mars bedrest", but I also think it's possible to have figures pointing somewhat unrealistically in the other direction.

      ---

      In any case, I'd completely agree with you that having 45 years of food would be quite pointless. That was the implicit point. The BFR's storage capacity to Mars is unprecedented and so even just taking everything you could ever possibly want to consume before you're able to setup self sufficient local food resources is completely trivial. So it's not like you have enough to last you through the first harvest or two and after that it's your choice of grilled potatoes, mashed potatoes, boiled potatoes, or potato soup.

      I found a source citing the exact mass of food for astronauts on the ISS. This [space.com] sources cites 3,630 kg as being the mass of food to support a crew of three for 6 months. That's 3630 * 2 / 3 = 2.42 metric tons per astronaut per year. That would be 6.6 kilograms of food per astronaut per day. No idea where they're getting those numbers from, but I'm going to have to suggest there is an error or misrepresentation in the data they're sourcing.

      • (Score: 2) by takyon on Monday October 02 2017, @10:08AM (1 child)

        by takyon (881) <reversethis-{gro ... s} {ta} {noykat}> on Monday October 02 2017, @10:08AM (#575833) Journal

        My only thought is that they counted a shipment of water in there. 1 L = 1 kg. 2-3 liters per day consumption seems to be typical. So now you are down to 3.6 kg of food per day.

        This page [nasa.gov] says:

        When astronauts travel into space, NASA scientists determine how much food will be needed for each mission. For example, an astronaut on the ISS uses about 1.83 pounds (0.83 kilograms) of food per meal each day. About 0.27 pounds (0.12 kilograms) of this weight is packaging material. Longer-duration missions will require much more food.

        2.5 kg from 3 meals per astronaut. Bump water consumption to 4 L per day and everything is accounted for!

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        • (Score: 0) by Anonymous Coward on Monday October 02 2017, @10:42AM

          by Anonymous Coward on Monday October 02 2017, @10:42AM (#575844)

          Yeah that could be the difference, but it would be be rather misleading. Water is heavily recycled precisely for that reason. Even urine is reprocessed into drinking water!

  • (Score: 2) by GreatAuntAnesthesia on Monday October 02 2017, @09:39AM

    by GreatAuntAnesthesia (3275) on Monday October 02 2017, @09:39AM (#575828) Journal

    And that 150 tons of food would eventually become 150 tons of sewage & C02, which could theoreticlaly be converted into 150 tons of plant food, which can become 150 tons of crops. It could be worth a hell of a lot more than 45 man-years of food.