Two to three feet of water is a very good insulator for radiation. Water could be placed in tanks above greenhouses that open to the outside with side windows. Sunlight would be indirect, but grow lights could be placed above the plants.
Quote from: high road on 09/24/2017 05:13 pmQuote from: Robotbeat on 09/23/2017 03:35 amGreenhouses don't need to be underground. That's sort of a misconception. It's okay to be above-ground for a few hours per day (up to ~30-35 hours per week if the rest of the time is well-shielded) without exceeding annual dose limits for Earthbound radiation workers (which most people on Mars basically will be), just like it's okay from a skin cancer perspective to be outside like 15-30 minutes per day without protection on a sunny day on Earth.How long can the plants stay in those greenhouses without suffering adverse effects from the radiation? Or how much protection is required to lower Martian radiation levels to the point they are no longer harmful to plant or animal life?At Mars levels, the radiation has basically no effects on plants and almost none on animals. It matters a little for humans because we have long lifespans. But as long we limit the length of time to about 30-35 hours a week, it's no worse than radiation worker limits on Earth.The Chernobyl exclusion zone is incredibly lush because the humans are gone. The radiation has essentially zero effect on the wildlife.
Quote from: Robotbeat on 09/23/2017 03:35 amGreenhouses don't need to be underground. That's sort of a misconception. It's okay to be above-ground for a few hours per day (up to ~30-35 hours per week if the rest of the time is well-shielded) without exceeding annual dose limits for Earthbound radiation workers (which most people on Mars basically will be), just like it's okay from a skin cancer perspective to be outside like 15-30 minutes per day without protection on a sunny day on Earth.How long can the plants stay in those greenhouses without suffering adverse effects from the radiation? Or how much protection is required to lower Martian radiation levels to the point they are no longer harmful to plant or animal life?
Greenhouses don't need to be underground. That's sort of a misconception. It's okay to be above-ground for a few hours per day (up to ~30-35 hours per week if the rest of the time is well-shielded) without exceeding annual dose limits for Earthbound radiation workers (which most people on Mars basically will be), just like it's okay from a skin cancer perspective to be outside like 15-30 minutes per day without protection on a sunny day on Earth.
All of the information on greenhouses is no the "Scaling Agriculture on Mars" thread. Two to three feet of water is a very good insulator for radiation. Water could be placed in tanks above greenhouses that open to the outside with side windows. Sunlight would be indirect, but grow lights could be placed above the plants. Believe me, I have used grow lights, it is amazing how fast plants can grow with these things. Anyway, read the thread. Agriculture will start small, and grow from there as greenhouses, above or below ground, are built to provide food and green ambiance for the closed in colonists. A lot of water will be needed for human and plant consumption, as well as fish and small animals. Most will be recycled, but much will still need to be added to a growing colony, and to provide fuel for spacecraft returning to earth.
Quote from: spacenut on 09/24/2017 06:15 pmAll of the information on greenhouses is no the "Scaling Agriculture on Mars" thread. Two to three feet of water is a very good insulator for radiation. Water could be placed in tanks above greenhouses that open to the outside with side windows. Sunlight would be indirect, but grow lights could be placed above the plants. Believe me, I have used grow lights, it is amazing how fast plants can grow with these things. Anyway, read the thread. Agriculture will start small, and grow from there as greenhouses, above or below ground, are built to provide food and green ambiance for the closed in colonists. A lot of water will be needed for human and plant consumption, as well as fish and small animals. Most will be recycled, but much will still need to be added to a growing colony, and to provide fuel for spacecraft returning to earth. either you use several feet of water for radiation protection and it dwarfs all other hydrogen needs other than fuel, or hydrogen is used to grow the colony and radiation protection is done by going underground. One or the other.
oh, humans are far worse for habitability than radiation, no doubt. But genetic damage in seeds might build up quickly for plants with short generaions. I wouldn't want my sole food source to depend on steadily mutating crops. Their nutrient production might change unexpectedly.
Quote from: high road on 09/24/2017 09:09 pmoh, humans are far worse for habitability than radiation, no doubt. But genetic damage in seeds might build up quickly for plants with short generaions. I wouldn't want my sole food source to depend on steadily mutating crops. Their nutrient production might change unexpectedly.I think the occasional good mutation would be deliberately propagated while cuttings and seeds from far deeper nurseries used to plant most gardens
I've read that only one foot of water screens out most radiation, on this forum somewhere. I didn't realize how little it took. Not several feet.
The halving thickness of water is about 7.2 inches. One foot of water will absorb 70% of the radiation. Two feet will absorb 90%.
Quote from: spacenut on 09/24/2017 09:24 pmI've read that only one foot of water screens out most radiation, on this forum somewhere. I didn't realize how little it took. Not several feet. The halving thickness of water is about 7.2 inches. One foot of water will absorb 70% of the radiation. Two feet will absorb 90%.NASA estimates a deep space cruise of 253 days would deliver a dose of .66 sieverts based on the data from Curiosity's trip to Mars. That comes out to ~2.608 millisieverts daily. For comparison exposure at Earth's surface is 10 microsieverts daily. Now if you are on the surface of Mars than Mars will block out half of the sky, thus half of the radiation so that leaves you with ~1.304 millisieverts daily. NASA says that a dose of 1 sievert is associated with a 5.5% increase in fatal cancer. Assuming you want to stay under 1 sievert than you could not stay on Mars unprotected for more than 476 days. Sounds ok for an exploration mission. Now when it comes to a settlement a foot of water is not nearly good enough. A 70% decrease will increases the time it takes to reach the 1 sievert dose from 476 days to 1586 days, which is only a little over 4 years. Two feet of water will increase the time to about 13 years. You really need about 40 inches before the time to reach 1 sievert comes out to 100 years.