Van Allen on Space Radiation.

[bknight]

I realize that Scott is long gone, but I's still like to respond to the James Collier article in the opening post.

And that is exactly what happened, they steered clear of the belts until adequate means of safeguarding the astronauts had been developed.  Furthermore, Dr. Van Allen's quote is taken out of context.  He was not referring to a rapid transit through the radiation belts.  Dr. Van Allen was specifically discussing two missions (Vanguard I and Sputnik III) that each spend two years orbiting through this region of space.  His warning was in reference to the integrated radiation exposure from these long duration missions.  Nothing in his statements preclude the possibility of an Apollo-style mission.

In addition there was a proposed space station that orbited at 1000 miles from Dr. Von Braun.

[ka9q]

Whenever anybody says you need lead to shield against radiation in space, they immediately reveal that they know very little about radiation in space.

[raven]

Whenever anybody says you need lead to shield against radiation in space, they immediately reveal that they know very little about radiation in space.

Yeah, one word: Bremsstrahlung. A very big word, but even I know lead is not the right stuff for the particle radiation Apollo would face going through the dose.

[Luke Pemberton]

Whenever anybody says you need lead to shield against radiation in space, they immediately reveal that they know very little about radiation in space.

One of the most exasperating aspects of the 'lead shielding' argument is how the CTs choose and pick their argument and demonstrate how little they know about radiation full stop. One issue that has arisen in the ISS is the trade off between using polymers and aluminium to offer structural integrity while ensuring astronauts are kept within their exposure limits.

Aluminium shielding makes the shielding of GCR more problematic than polymers as GCR interact with the aluminium nuclei of greater charge more easily than those in polymer based. This interaction causes GCR to fragment which leads to greater exposed dose (if I recall this is due to exotic matter being formed, which has a greater equivalent dose). The thicker the aluminium shileding, the more fragmentation of GCR. The CTs use this an argument against the use of aluminium in Apollo, citing that aluminium presents a greater problem. Lead, with a much greater atomic number, makes the fragmentation problem much greater so is an even poorer choice of material.

Of course, there is the small issue that GCR on a short mission to the moon are not as problematic as a shock driven CME event. The aluminium/lead argument in this case is moot as comparing the shielding regimes for Apollo and the ISS are apples and pears. Fragmentation of GCR, while I wouldoccur, is simply no an issue when one considers exposure over 14 days.

The other real issue for Apollo was X-ray bremsstrahlung in the van Allen belts, not fragmentation of high energy nuclei, so using a material with a low Z is the obvious option. But we know this.

[bknight]

I had to look up GCR, new one for me.  More of a problem for Orion, then?

[ka9q]

GCR is a potential problem for any long space trip. It could be ignored during Apollo because the missions were so short, but the accumulated dose over time could be a problem. It's continuous at a low level but cannot be practically shielded.

The bigger problem is probably still CMEs -- coronal mass ejections. These are rare and only somewhat predictable, but a severe one can give you acute radiation sickness if it hits you. Some sort of "storm cellar" seems appropriate here. On a surface, like Mars or the Moon, some sort of underground shelter seems like your best bet. In space, you have limited mass for shielding so you have to do the best with what you have, especially water, fuels and plastics, all of which have lots of hydrogen.

[bknight]

CME's occur approximately 6 times per year still?  Or has the Sun's activity increased the average rate?

[nomuse]

I realize that Scott is long gone, but I's still like to respond to the James Collier article in the opening post.

And that is exactly what happened, they steered clear of the belts until adequate means of safeguarding the astronauts had been developed.  Furthermore, Dr. Van Allen's quote is taken out of context.  He was not referring to a rapid transit through the radiation belts.  Dr. Van Allen was specifically discussing two missions (Vanguard I and Sputnik III) that each spend two years orbiting through this region of space.  His warning was in reference to the integrated radiation exposure from these long duration missions.  Nothing in his statements preclude the possibility of an Apollo-style mission.

In addition there was a proposed space station that orbited at 1000 miles from Dr. Von Braun.

I was unaware he had such gravity.

[Luke Pemberton]

The bigger problem is probably still CMEs -- coronal mass ejections. These are rare and only somewhat predictable, but a severe one can give you acute radiation sickness if it hits you.

Be a bit careful when talking about CMEs as being rare. CMEs are not rare and occur quite frequently. A large proportion of CMEs produce protons with speeds that are comparable to the solar wind, so from a radiation protection point of view, while huge quantities of matter are produced, the energies involved pose little problem from a shielding point of view.

Shock driven CMEs, the type that cause solar proton events are rarer events, many of these are known as partial-halo events, where Earth-CME alignment means we catch the edge of a shock driven event and an SPE is registered at Earth.

CMEs that cause the massive solar storms, such at the type observed in August 1972 or the Halloween storm, are caused by halo-CMEs, these are indeed rare.

To claim that CMEs are rare leaves a door open to the CTs, and the inevitable 'we can't get a story straight' accusations.

[Kiwi]

...GCR...

I, too, had to look up GCR.  Please, could we always give the definitions of the less-common abbreviations we use – at least for the first time in a thread or perhaps after a long gap? Not doing so has often been criticised by opponents of forums like ours as elitist, thoughtless and pompous.

GCR =
Galactic Cosmic Ray/Radiation
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[ka9q]

The bigger problem is probably still CMEs -- coronal mass ejections. These are rare and only somewhat predictable, but a severe one can give you acute radiation sickness if it hits you.

Be a bit careful when talking about CMEs as being rare.

Point taken. I meant the really powerful, shock-driven ones that actually hit you and cause problems. The earth-moon system is pretty big, but it occupies a tiny fraction of the sphere surrounding the sun. Most will miss.

It's hard to fathom the energies involved here, especially when you consider that the "surface" gravity on the sun is 28 g!

[bknight]

I realize that Scott is long gone, but I's still like to respond to the James Collier article in the opening post.

And that is exactly what happened, they steered clear of the belts until adequate means of safeguarding the astronauts had been developed.  Furthermore, Dr. Van Allen's quote is taken out of context.  He was not referring to a rapid transit through the radiation belts.  Dr. Van Allen was specifically discussing two missions (Vanguard I and Sputnik III) that each spend two years orbiting through this region of space.  His warning was in reference to the integrated radiation exposure from these long duration missions.  Nothing in his statements preclude the possibility of an Apollo-style mission.

In addition there was a proposed space station that orbited at 1000 miles from Dr. Von Braun.

I was unaware he had such gravity.

Tongue in cheek, LOL as he proposed a space station at 1000 miles.   IIRC it was on a Disney program, concerning space exploration.

[JayUtah]

Point taken. I meant the really powerful, shock-driven ones that actually hit you and cause problems.

That's what I usually mean too, without forgetting that lesser-magnitude events occur.  The engineering mentality, I guess, are that those are the ones that you worry about; the rest is just weather.

[bknight]

This discussion reminds me of the question which Luke answered

 720802 72075 0316-0451 13 -35 1B 11976 32322 12
 720802 72075 0505-0800 14 -34 SN 11976 32322 12
 720802 72076 1838-1859 14 -26 1B 11976 21200 5?
 720802 72077 1958-2355 13 -27 2B 11976 22333 13

The flares occurred during the 1972 solar storm, but these data describe the duration of H-alpha prominences, areas of the sun where filament heating occurs. The coding 1B, SN, and 2B describe the 'magnitude' of the prominence. I'd have to go digging in the loft for a text, but if I recall the number pertains to the brightness of the prominence and the letter pertains to the area of the prominence. It is quite a subjective classification. SN, I'm fairly sure, means it is too minor to classify. The number goes up as far as 4, which is the brightest prominence. The third set of numbers describe the duration of the prominence. This time does not represent the time of a solar flare, it represents the duration of the flare developing from initial heating to the final connection of the magnetic field. The final connection period is where the flare produces soft x-rays over a duration, typically measured in seconds.

The solar storm that occurred at the same time was created by a shock driven CME, and such events are accompanied by active regions of the sun showing H-alpha prominences. However, an H-alpha prominence does not always correlate with a shock driven CME. In other words, shock driven CMEs are usually a result of rearrangement of the solar magnetic field and ejection of plasma, where regions of the sun become H-alpha active. Regions of the sun can also become H-alpha active, but there is no large scale rearrangement of the magnetic field.

Ok if this is the H-alpha data, where in the data would I find the shock driven CM's?

Here is the link to the data I initially queried.  I assume that shock driven CME's would be in a relative similar location.

[bknight]

This discussion reminds me of the question which Luke answered

 720802 72075 0316-0451 13 -35 1B 11976 32322 12
 720802 72075 0505-0800 14 -34 SN 11976 32322 12
 720802 72076 1838-1859 14 -26 1B 11976 21200 5?
 720802 72077 1958-2355 13 -27 2B 11976 22333 13

The flares occurred during the 1972 solar storm, but these data describe the duration of H-alpha prominences, areas of the sun where filament heating occurs. The coding 1B, SN, and 2B describe the 'magnitude' of the prominence. I'd have to go digging in the loft for a text, but if I recall the number pertains to the brightness of the prominence and the letter pertains to the area of the prominence. It is quite a subjective classification. SN, I'm fairly sure, means it is too minor to classify. The number goes up as far as 4, which is the brightest prominence. The third set of numbers describe the duration of the prominence. This time does not represent the time of a solar flare, it represents the duration of the flare developing from initial heating to the final connection of the magnetic field. The final connection period is where the flare produces soft x-rays over a duration, typically measured in seconds.

The solar storm that occurred at the same time was created by a shock driven CME, and such events are accompanied by active regions of the sun showing H-alpha prominences. However, an H-alpha prominence does not always correlate with a shock driven CME. In other words, shock driven CMEs are usually a result of rearrangement of the solar magnetic field and ejection of plasma, where regions of the sun become H-alpha active. Regions of the sun can also become H-alpha active, but there is no large scale rearrangement of the magnetic field.

Ok if this is the H-alpha data, where in the data would I find the shock driven CME's?

Here is the link to the data I initially queried.  I assume that shock driven CME's would be in a relative similar location.  ftp://ftp.ngdc.noaa.gov/STP/SOLAR_DATA/SOLAR_FLARES/FLARES_IN?DEX/McMath/CFI55_80.TXT