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Space-X Falcon Heavy Launch
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BarkellWH
Posts: 3458
Joined: Jul. 12 2009
From: Washington, DC
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 RE: Space-X Falcon Heavy Launch (in reply to Ricardo)
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quote:
Exposure to radiation will be minimal time wise, and once on mars, the crew can generate some sort of artificial magnetic field similar to what Earth has.
Earth's magnetic field (which protects us from radiation) surrounds circulating electic currents in the Earth's molten, metalic core that are the field's source. It is the Earth acting like a dynamo, and the field extends far out into space. I have not seen anything to indicate how explorers/scientists on Mars could possibly generate an "artificial magnetic field similar to what Earth has."
I would be interested if you could cite a source for this observation. To create a magnetic field on Mars similar to that found on Earth would require Mars to act as a dynamo, with internal electric currents generated by a molten, metalic core like that found on Earth. If Mars lacks this attribute, how would it be artificially accomplished by visitors to Mars? Even if we are talking about a magnetic field restricted to the area surrounding the crew's quarters, it would have to extend far into space to achieve the same protective effect as Earth's magnetic field.
Bill
_____________________________
And the end of the fight is a tombstone white,
With the name of the late deceased,
And the epitaph drear, "A fool lies here,
Who tried to hustle the East."
--Rudyard Kipling
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Date Feb. 9 2018 16:43:22
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Piwin
Posts: 3559
Joined: Feb. 9 2016
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RE: Space-X Falcon Heavy Launch (in reply to jalalkun)
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There's some interesting work on small localised shields. I think it's already been successfully tested.
http://iopscience.iop.org/article/10.1088/0741-3335/50/12/124025/meta
NASA is even more ambitious and has floated the idea of creating a magnetosphere for the entire planet of Mars.
https://phys.org/news/2017-03-nasa-magnetic-shield-mars-atmosphere.html
But there are significant logistical problems (significant amount of infrastructure required, so too much mass to carry that infrastructure in one single launch, energy requirements, etc.). It doesn't sound like a solution for the first guys out there, but maybe for the longer term. The other options (physical shields or medical advancements) might protect astronauts out there, but a magnetic shield does much more than that, possibly (if NASA's ambitions come to fruition) recreating a viable atmosphere on Mars. It's theoretically possible, but we may have to wait a bit longer than 2024 
I do agree with Ricardo's friend that Elon Musk has been rather cavalier about it. At least in his public speeches. Perhaps behind the scenes he's hard at work to find a solution but publicly he's just been saying that it's "no big deal", whereas researchers in the field say otherwise. I'll bet money the first launch isn't in 2024. It's not being pessimistic, I'm really excited at the prospect and really think they'll get there. But it's like large construction projects. There's always something that comes up and adds delays. Hell, even this falcon heavy launch was supposed to happen 5 or 6 years ago so I figure it's safe to assume there will also be delays for the first Mars mission. Unless China announces it's sending people up there, then you know everything will speed up!
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Date Feb. 11 2018 9:17:04
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Richard Jernigan
Posts: 3430
Joined: Jan. 20 2004
From: Austin, Texas USA
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RE: Space-X Falcon Heavy Launch (in reply to jalalkun)
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Shielding the Mars pioneers from ionizing radiation is necessary because it disrupts synapses, and indeed entire cells in the brain. Large enough doses lead to cognitive decline. The effects are noticeable in some people who receive radiation treatments for brain cancer. Animal experiments indicate that high enough levels of damage can be long lasting, if not permanent.
Our magnetosphere shelters us from the full force of the solar wind, but a few particles leak through. We have evolved to survive the lifetime dose, pretty well. Shielding alternatives that I know of cost weight, the main nemesis of the rocket designer. Each ounce of payload weight is multiplied by the weight of the required additional structure, and a very heavy penalty in required fuel, fuel tankage, etc.
The Apollo astronauts survived the Van Allen belt and translunar space without visible long term effects. I recollect reports of occasional visual light flashes, tentatively attributed to ionizing radiation. However, the possibility of a large solar flare was a worrying prospect. Radiation exposure was monitored by instrumentation on the spacecraft, but above a certain threshold the medical officer (often my brother) was to be notified. I never asked him what, if anything, they might have done.
I seriously doubt that a practical threshold of safe radiation exposure is known. There are legal guidelines in the USA, generally considered to be very conservative. For example, people who work near high power radar transmitters are required to wear X-ray badges. If their exposure exceeds a certain threshold, they are removed from the environment for a period of time, and management are required to make engineering changes to lower the radiation level.
Space travel introduces two more variables: how much risk are you willing to take to save weight? and how do you quantify the risk relative to the level of exposure to high energy particles? The first question is an ethical one, the second scientific.
I am reminded of a conversation I had with my brother. While we were visiting them he came home one day saying he had been battling with the engineers. They were specifying the backup life support system for the Apollo spacecraft. The engineers were badgering him with the question, "What is the minimum amount of oxygen required to sustain human life?"
My brother responded that the answer was unknown to medical science.
"Well, can't medical science find out?"
"No," he replied.
"Why not?"
"We take an oath not to intentionally kill anybody."
Of course the oath reads, "First, do no harm." How you quantify the risk of radiation damage without doing harm to anybody is a vexed question. Animal studies are a fairly blunt instrument if you're trying to quantify the effects on human cognition.
RNJ
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Date Feb. 19 2018 0:36:45
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