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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.
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SpaceX: Making Human Life Multiplanetary
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The last time I saw him he was walking down Lover's Lane holding his own hand.
-- Fred Allen
(Score: 0) by Anonymous Coward on Monday October 02 2017, @09:41AM (2 children)
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.
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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)
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:
2.5 kg from 3 meals per astronaut. Bump water consumption to 4 L per day and everything is accounted for!
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 0) by Anonymous Coward on Monday October 02 2017, @10:42AM
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!