Who's Afraid of a Solar Flare?

10kBq Jaro · Senior Member

Who's Afraid of a Solar Flare?

stungun · Veteran Member

Hi Jaro,

Interesting article. I have my doubts about the priority of a man on mars, but the magnet field phemomena that lowers radiation exposure is very interesting. The article wonders if timed correctly, if it might provide safe (safe enough) escort for humans to mars. I wonder if the magnetic field shield can be artificially imitated.

Here are a few quotes I enjoyed...

"No one knows all the things cosmic rays might do to humans. "We haven't been in space long enough," says Cucinotta.

<SNIP>

One thing is clear. "Reducing exposure is a good thing," he says."

In context...

"No astronaut wants to encounter a swarm of high-energy solar protons. Severe storms are literally sickening; exposure causes vomiting, fatigue and low blood counts. Without medical attention, an astronaut suffering from radiation sickness could die. Now for the good news: few solar protons are able to penetrate the hulls of NASA spaceships. As long as astronauts stay inside, they're safe.

Cosmic rays are different—and worse. Cosmic rays are super-charged subatomic particles coming mainly from outside our solar system. Sources include exploding stars, black holes and other characters that dwarf the sun in violence. Unlike solar protons, which are relatively easy to stop with materials such as aluminum or plastic, cosmic rays cannot be completely stopped by any known shielding technology.

Even inside their ships, astronauts are exposed to a slow drizzle of cosmic rays coming right through the hull. The particles penetrate flesh, damaging tissue at the microscopic level. One possible side-effect is broken DNA, which can, over the course of time, cause cancer, cataracts and other maladies.

Above: Neutron counts from a cosmic ray monitoring station in Moscow. Radiation levels dropped in early Sept. during a period of intense solar activity. [More]

No one knows all the things cosmic rays might do to humans. "We haven't been in space long enough," says Cucinotta.

Except during brief trips to the Moon forty years ago, he explains, astronauts have never been fully exposed to galactic cosmic rays. Close to Earth where the ISS orbits, crews are protected not only by their ship's hull, but also by Earth's magnetic field and the gigantic solid body of Earth itself. A 6-month trip to Mars, far from these natural shields, is something new. What are the long-term risks? How much shielding is needed to keep astronauts safe? NASA researchers are grappling with these questions.

One thing is clear. "Reducing exposure is a good thing," he says

GoogleNaut · Guru

One of the components of cosimic rays are completely ionized Fe ions. These bare iron nuclei slam into the hulls of spacecraft, and are capable of creating pretty significant secondary showers of aluminum, nickel, silicon ions (in varying degrees of ionization.) The bare heavy nuclei--although fairly rare in cosmic rays--represent a significant threat. Ironically almost no threat occurs from the ultra-energetic cosmic rays (protons with kinetic energies of order 10^20 eV) which are amongst the rarest particles in the universe. And it is not well understood what generates them. Most cosmic rays are thought to be the emissions from extragalactic supernova--which is the origin of the iron nucleii and other energetic particles.

I'd have to agree that better shielding is, well, better.

I am an advocate of using a relatively thick layer of something like water for primary shielding--say 10 cm thick. This would add a lot of mass to a mars bound ship. In addition, a centrally located radiation storm cellar with additional water shielding makes sense to protect crews from the worst of a solar-flare. Also, with the use of a nuclear thermal rocketry, a fast transit vehicle carrying the exploration crew would significantly cut a crews total exposure to cosmic and solar radiation. Besides it just makes sense to send supplies, landing vehicles, and other stuff on a dedicated logistics vehicle. Most of the Mars base could be landed and set up before the crew even departed for Mars. Then a fast transit vehicle with a high delta-v burn from a nuclear Triton stage could 'zip' the crew to the destination in fairly short order. A high delta-v fast return trajectory can be made to return the crew back to Earth. Otherwise, a longer manned voyage will require a much larger vehicle, capable of much better shielding to reduce the total radiation dose recieved by each crewman.

The other thing with cosmic and solar radiation--exposure tends to be full body exposure. I'm not enough of an expert to predict what effects this can have on a human body, but I do know that intuitively speaking, it makes sense to limit full body exposure to penetrating radiation. A full body dose to a lower intensity of radiation might have more of a biological effect than a higher flux, but very locallized dose. I percieve this as a sort of 'calculus of exposure'--one must integrate the total radiation flux over the entire volume in order to determine the total recieved dose. This makes the problem complex and difficult to answer, especially where attenuation of various tissues are concerned. I know that extensive research has been done on the topic, but I'm not sure to what degree it has been 'put together' so that a fairly consistent picture can be obtained given various radiation parameters (flux intensity, energy spectrum, and duration of exposure.)

Dusty · Veteran Member

Whenever this sort of discussion takes place I find myself in awe of the energies that cosmic rays can attain.

>10^20eV!

Thats not far off a rifle bullet!

Dusty