Will it be safe for humans to fly to Mars?
Sending human travelers to Mars would require scientists and engineers to overcome a range of technological and safety obstacles. One of them is the grave risk posed by particle radiation from the sun, distant stars and galaxies.
Answering two key questions would go a long way toward overcoming that hurdle: Would particle radiation pose too grave a threat to human life throughout a round trip to the red planet? And, could the very timing of a mission to Mars help shield astronauts and the spacecraft from the radiation?
In a new article published in the peer-reviewed journal Space Weather, an international team of space scientists, including researchers from UCLA, answers those two questions with a "no" and a "yes."
That is, humans should be able to safely travel to and from Mars, provided that the spacecraft has sufficient shielding and the round trip is shorter than approximately four years. And the timing of a human mission to Mars would indeed make a difference: The scientists determined that the best time for a flight to leave Earth would be when solar activity is at its peak, known as the solar maximum.
The scientists' calculations demonstrate that it would be possible to shield a Mars-bound spacecraft from energetic particles from the sun because, during solar maximum, the most dangerous and energetic particles from distant galaxies are deflected by the enhanced solar activity.
Journal Reference:
M. I. Dobynde, Y. Y. Shprits, A. Y. Drozdov, et al. Beating 1 Sievert: Optimal Radiation Shielding of Astronauts on a Mission to Mars [open], Space Weather (DOI: 10.1029/2021SW002749)
(Score: 5, Funny) by Anonymous Coward on Wednesday September 15 2021, @01:00PM (2 children)
see to it that Soylent News is keeping their certificate current, lest you arrive on Mars only to be greeted with an error about an expired certificate and forced to turn back.
(Score: 0, Insightful) by Anonymous Coward on Wednesday September 15 2021, @01:30PM (1 child)
Or just go back to proper HTTP, which does not require this kind of nazi-ific bullshit.
(Score: 2) by DannyB on Wednesday September 15 2021, @04:54PM
The NSA approved this message.
The lower I set my standards the more accomplishments I have.
(Score: 3, Informative) by c0lo on Wednesday September 15 2021, @02:16PM (7 children)
Just put the water tanks between the Sun and the travelers to Mars. 10cm of water will halve the γ ray intensity [eu.com] α and β aren't of any concern.
https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
(Score: 1, Interesting) by Anonymous Coward on Wednesday September 15 2021, @03:01PM (2 children)
It's neither the gammas or the betas that are the problem, it is the high energy cosmic rays (mostly protons). Shielding is complicated in that as you add more shielding, you decrease the flux of cosmic rays, but you increase the flux of secondary particles generated in the shielding, so it is an optimization problem. I will have to look at the paper in detail later to see what they say about solar flares (CMEs), which would be more prevalent during solar max.
(Score: 0) by Anonymous Coward on Thursday September 16 2021, @12:19PM (1 child)
As I understand it you need low atomic number or Low-z materials to do the mopping up of any spallation neutrons generated. Hence the water / boronated ethylene.
The radiation shield needs to be basically a long cylinder they can all fit inside of.
(Score: 0) by Anonymous Coward on Thursday September 16 2021, @12:23PM
I think Low Z materials make poor spallation targets, its like pool or billiards basically? Something about elastic collisions. I'm not a particle physicist obviously.
(Score: 5, Interesting) by Immerman on Wednesday September 15 2021, @03:21PM (3 children)
They were specifically looking at *particle* radiation, so gamma rays weren't considered. Meanwhile alpha and beta should be mostly blocked by the ship's skin, but the resulting ionization could still present shocking (heh) difficulties.
Heck, I imagine just the pointing the engines and fuel tanks at the sun would do an excellent job of shielding from solar radiation. I'm not sure how the shielding properties of liquid methane and oxygen compare to water, though with all those hydrogen bonds methane at least should compare pretty well, but having many meters of the stuff (on average, it'll be floating around) should do the job nicely.
But that's less than half the radiation - at Earth's orbit only about half the radiation comes from the sun while the other half, including most of the extreme high energy radiation, comes from distant astronomical sources. And as you move further from the sun on your way to Mars the solar portion decreases.
Since effectively shielding against cosmic rays is currently pretty much impossible given the mass constraints, traveling at solar maximum to minimize the interstellar radiation by taking advantage of the shielding effects of the denser solar wind seems to make sense.
However, I can't help wondering just how dramatic the difference really is.
(Score: 1, Informative) by Anonymous Coward on Wednesday September 15 2021, @05:23PM
Skimming the article suggests a nearly 3:1 reduction in cosmic rays. As cosmic rays are more dangerous than solar radiation that seems significant.
(Score: 0) by Anonymous Coward on Wednesday September 15 2021, @07:30PM (1 child)
Not quite that simple. During solar minimum, when the solar magnetic fields (close to the ecliptic plane) are generally described as Archimedean spirals, higher energy charged particles from flares and other disturbances predominantly travel along those spirals, which at around 1 AU are at angles around 45 degrees, so you'd want to point your engines about 45 degrees towards the western limb. However, at solar maximum, it is all a mess. The spirals are disturbed by all sorts of stuff and your solar magnetic field angle at your spacecraft can be all over the place, meaning that your particles will be all over the place. Plus you add in the spiral trajectories of charged particles due to Coulomb forces, it gets even messier. That's why galactic cosmic rays are largely isotropic in their arrival directions all the time. Solar less so, but much more jumbled up during solar max.
(Score: 2) by Immerman on Thursday September 16 2021, @01:38PM
Hmm, I hadn't thought of that. So I suppose you would want shielding adequate for solar particle radiation in pretty much every direction. You'd have to decide whether it makes more sense to point the engines at the densest (highest energy?) incoming particle concentration, or directly at the sun to block the neutral and EM stuff. My guess would be the latter, unless they were hit by a tide of something really serious.
Of course, I think the article was actually discussing cosmic ray exposure inside a radiation shield (10-30g/cm^2?) anyway, so that's probably exactly what they were visualizing.
(Score: 0) by Anonymous Coward on Wednesday September 15 2021, @02:42PM (8 children)
Starship is made of steel, so pretty easy to magnetize.
(Score: 4, Interesting) by Runaway1956 on Wednesday September 15 2021, @03:03PM (5 children)
What kind of steel, specifically, is Starship made of?
https://www.rocheindustry.com/is-stainless-steel-magnetic/ [rocheindustry.com]
Next question would be, Do you really want a magnetized hull for space travel? You point out an obvious benefit, but what about all the instruments in and on the hull? Which will be affected, and how? If you can make all the instrumentation happy with magnetic surroundings, then what about the equipment? Imagine a valve picking up it's own magnetic charge from the hull, and refusing to turn, or drifting back to it's preferred orientation during a rocket engine burn.
I suspect that magnetizing the hull would introduce a lot of complications, that may or may not be solved.
(Score: 0) by Anonymous Coward on Wednesday September 15 2021, @03:09PM (1 child)
Well, the biggest one I can think of is it will really mess up their credit cards and hotel room keys.
(Score: 2) by Runaway1956 on Wednesday September 15 2021, @03:23PM
Well if I can't stay at Olympus Mons Hilton, I'm not going!
(Score: 2) by DannyB on Wednesday September 15 2021, @05:03PM (1 child)
Will instruments located in or on the hull go out of tune due to a magnetic field?
A Pitot tube [wikipedia.org] for example, used to measure air speed during the voyage to Mars, would seem to be unaffected by magnetism.
The lower I set my standards the more accomplishments I have.
(Score: 1, Interesting) by Anonymous Coward on Wednesday September 15 2021, @07:37PM
The momenta of all of these particles under consideration are much too high for you to generate your own local magnetic field to shield them. Every now and then someone will win one of those NASA advanced concepts awards (those "pie-in-the-sky" ideas where they give you enough money to do a nice little study and write a paper) that have ideas along these lines of magnetic shielding, such as instead of generating a really strong local dipole field, you have a formation of unmanned spacecraft that can generate reasonable strength magnetic fields, but you fly them at a distance from the astronaut spacecraft to create a large effective field at a distance, etc., etc.).
(Score: 0) by Anonymous Coward on Wednesday September 15 2021, @07:52PM
I know right? I mean, how do they expect the compass to work? What if they end up going in circles???
(Score: 1, Funny) by Anonymous Coward on Wednesday September 15 2021, @03:05PM (1 child)
If the astronauts are vaccinated, won't that take care of the magnetization problem?
(Score: 3, Touché) by DannyB on Wednesday September 15 2021, @05:04PM
If astronauts are vaccinated then they haven't been listening to the anti-vax conservative talk show hosts who are dropping like flies from covid.
The lower I set my standards the more accomplishments I have.
(Score: 0) by Anonymous Coward on Wednesday September 15 2021, @05:32PM
problem solved!
(Score: 2) by Beryllium Sphere (r) on Wednesday September 15 2021, @08:18PM (1 child)
I haven't checked good sources but had been under the impression that occasional solar events could be seriously dangerous.
(Score: 0) by Anonymous Coward on Wednesday September 15 2021, @09:58PM
CMEs are short term events and can be readily tracked, so having a small, well shielded CME shelter is much lighter than trying to shield the entire ship to that standard. The bigger problem is continuous radiation exposure, and cosmic rays are more dangerous and harder to block than solar radiation, especially as you get farther from the sun.
(Score: -1, Troll) by Anonymous Coward on Wednesday September 15 2021, @09:05PM (1 child)
Stop wasting money on spaceships and use it to educate inner city children. #BLM
(Score: 1, Insightful) by Anonymous Coward on Wednesday September 15 2021, @10:15PM
In 2017 the US spent $762 billion on education. NASA's budget for that year was $19.7 billion, or 2.6% of the education budget. Space ships aren't the problem.