Apollo Moon Missions and Solar CMEs

RJ Emery · #1 (**permalink**) 28-May-2008, 07:21 AM

How protected were the Apollo astronauts against solar flares and CMEs? Would the CM and LM afforded sufficient shielding? I think not.

01101001 · #2 (**permalink**) 28-May-2008, 07:33 AM

Science@NASA: Sickening Solar Flares

Quote:

To die, you'd need to absorb, suddenly, 300 rem or more.
[...]
Such doses from a solar flare are possible. To wit: the legendary solar storm of August 1972.

It's legendary (at NASA) because it happened during the Apollo program when astronauts were going back and forth to the Moon regularly. At the time, the crew of Apollo 16 had just returned to Earth in April while the crew of Apollo 17 was preparing for a moon-landing in December. Luckily, everyone was safely on Earth when the sun went haywire.

"A large sunspot appeared on August 2, 1972, and for the next 10 days it erupted again and again," recalls Hathaway. The spate of explosions caused, "a proton storm much worse than the one we've just experienced," adds Cucinotta. Researchers have been studying it ever since.

Cucinotta estimates that a moonwalker caught in the August 1972 storm might have absorbed 400 rem. Deadly? "Not necessarily," he says. A quick trip back to Earth for medical care could have saved the hypothetical astronaut's life. [...]

An Apollo command module with its aluminum hull would have attenuated the 1972 storm from 400 rem to less than 35 rem at the astronaut's blood-forming organs. That's the difference between needing a bone marrow transplant … or just a headache pill. [...]

JonClarke · #3 (**permalink**) 28-May-2008, 08:29 AM

The Apollo CM offered significant shielding, ~ 8g/cm2.

Have have often wondered how directional the radiation is. For example, would putting the SM between you and the sun create a radiation shadow?

Jon

Swift · #4 (**permalink**) 28-May-2008, 01:23 PM

Quote:

Originally Posted by JonClarke

The Apollo CM offered significant shielding, ~ 8g/cm2.

Have have often wondered how directional the radiation is. For example, would putting the SM between you and the sun create a radiation shadow?

Jon

I believe much of the radiation is from charged particles, so I would guess that it is very directional and that such a move would help a lot.

ravens_cry · #5 (**permalink**) 28-May-2008, 02:22 PM

Considering that the article states that the main brunt comes at 1/3 light speed, if true, then it has to be particles. Unless something is really, really whacked.

RJ Emery · #6 (**permalink**) 28-May-2008, 02:58 PM

The article does not state about exposure when passing through any of the Van Allen Radiation Belts during a CME event. In the Belts, charged particles are concentrated and would deliver a concentrated jolt to anyone passing through them, regardless of how brief. It may just exceed the limit.

JonClarke · #7 (**permalink**) 28-May-2008, 11:05 PM

Quote:

Originally Posted by Swift

I believe much of the radiation is from charged particles, so I would guess that it is very directional and that such a move would help a lot.

That is what I would have thought. In which case an appropriately designed spacecaft could put not g/cm2 but kg/cm2 between the sun and the crew. In which case it would be a case of "CME? What CME?"

But I have never seen this confirmed.

Jon

JonClarke · #8 (**permalink**) 28-May-2008, 11:10 PM

Quote:

Originally Posted by RJ Emery

The article does not state about exposure when passing through any of the Van Allen Radiation Belts during a CME event. In the Belts, charged particles are concentrated and would deliver a concentrated jolt to anyone passing through them, regardless of how brief. It may just exceed the limit.

It goes not matter how much more radiation there is, so long as it is not more energetic. If 8 g/cm2 was adequate against CMEs for Apollo mission durations, it would be fine against the low energy radiation in the VAB. The Earth's magnetic field channels and slows particles very well. Only a couple of g/cm2 is enough to provide protection in the VAB - less than the walls of the CSM.

One caveat is that radiation comes from several directions in the VAB so a shadow shield definitely would not work.

Jon

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