Radiation

[timfinch]

https://www.lpi.usra.edu/meetings/leag2012/presentations/Stubbs.pdf

...and? What are you trying to show me, other then Cycle 20 was a more active time for the Sun than when the current CRaTER data was collected in cycle 24? So the three questions still remain:

• Have you interrogated the CRaTER data?
• How can you extrapolate between cycle 24 and 20?
• How does GCR flux vary with solar activity?

Nice graph.  Although the next few solar cycles WERE more active than 24, cycle 20 is also CLEARLY more active than cycle 20.  But trolls don't swallow facts, so I predict no admission of this simple truth from him.

cycle 20 is also CLEARLY more active than cycle 20"??

Yep.  I made a mistake.  I should have said "cycle 20 is also CLEARLY more active than cycle 24".

See how easy that is?

So the article stating that cycle 20 was not as active as later cycles is wrong also?

[Luke Pemberton]

As a non-physicist how am I doing? Anyone care to calculate probabilities?

The main mechanism at GCR energies spallation bye protons. The proton will interact with the nuclei of atoms and produce a shower of pions and a neutron. The pions will quickly decay in leptons and muons, with gamma being produced. There will also be bremstrahlung. It really is very complicated, but the main result is a a neutron, a lot neutrinos, some muons and then electrons/positrons are produced. The latter can are normally produced through pair production.

There's no NASA cabal as our friend suggests. In fact there are several NASA article that discuss the primary shower of proton fragmentation and the production of pions. There is also fragmentation of heavier nuclei in the GCR.

The whole idea of the GCR being captured by nuclei to synthesise radio isotopes is a little barking. Neutron capture is a possibility, but with light elements found in rocks, the cross sections are very low, and you have to get right down to thermal energies for it to occur. At the relativistic energies we are discussing the cross section for neutron capture fall by several orders of magnitude for light elements. For most elements it is practically zero.

[timfinch]

Secondary Flux on the Moon
Energetic particles and neutrons from cosmic rays induce nuclear reactions with target nuclei in the lunar regolith. Solar cosmic ray-produced secondaries are much less abundant than galactic cosmic ray-produced secondaries and occur primarily in the upper decimeter of the regolith. Since it is the energy of the incident particle that determines what reactions will occur, the GCR particles are of most concern. Typical particles with energies at MeV levels will induce reactions with an interaction mean free path of about 100 g cm-2. Thus, even GCR particles will interact with lunar surface materials at depths <5 m.

During the nuclear reactions (E >10 MeV) secondary particles are emitted; the original particle may emerge at a lower energy. Secondary neutrons and high energy particles can cause additional reactions. It is the secondary particles, especially the neutrons caused by GCR, that are relevant.

Solar wind particles are typically of such low energy that they penetrate no more than a micrometer. They can produce sputtered particles and can induce crystal damage. Most solar cosmic rays are stopped by ionization within the upper few cm of the regolith. The associated heavy nuclei are stopped in the outer millimeter. The main reactions produced by solar cosmic ray particles occur in the upper cm of the regolith, and few secondary particles are released.

Heavy nuclei in GCR radiation are usually stopped at depths <10 cm due to ionization energy loss, with most radiation damage occurring in the upper few cm. Shielding at a few g cm-2 is typically sufficient to remove most of the highly ionized heavy GCR nuclei. The lighter primary nuclei are more penetrating than heavier nuclei. Secondaries may be ionizing particles or uncharged, e.g. neutrons. The cascade that results from interaction depends on the energy of the incident particle and the nature (average atomic number) of the interacting material but can extend to depths of meters. Neutrons produced on the Moon typically have energies of a few MeV and travel until they interact or escape. Neutron interaction is most efficient with elements whose mass is lower than oxygen. Because such elements have relatively low concentrations (Table II), neutrons lose energy slowly and require many collisions to reach thermal energies (<0.1 eV).

https://www.lpi.usra.edu/wiki/lunaref/index.php/Lunar_Ionizing_Radiation_Environment


Moon dust is radioactive and this article is the definitive proof.  The  radiation reflected from the Moon raise the Background radiation in orbit around the Moon 30 to 40 percent.  Think about that for a minute.  The surface of the moon is so radioactive that it increases the radiation in the lunar orbit by 30 to 40 percent.  That is staggering.

Once again, his own source refutes him.  From the above reference:
"The ionizing radiation environment at the Moon, both in orbit and on the surface, consists of the solar wind, solar particle events (SPE, also referred to as solar cosmic rays) and galactic cosmic radiation."

Please note the absence of "radioactive Moon dust" as being included as part of the Moon's radiation environment.  This is because that dust's temporary radioactivity is caused by the GCR's secondary events - NOT neutron capture that makes the elements unstable, and thus causes them to be considered radioactive.  This has been previously explained, but like any good troll, he ignores that fact.

Am I to believe that you think only neutron capture is responsible for nuclear instability?  So you don't believe High energy particles and rays can cause fission?

[MBDK]

https://www.lpi.usra.edu/meetings/leag2012/presentations/Stubbs.pdf

...and? What are you trying to show me, other then Cycle 20 was a more active time for the Sun than when the current CRaTER data was collected in cycle 24? So the three questions still remain:

• Have you interrogated the CRaTER data?
• How can you extrapolate between cycle 24 and 20?
• How does GCR flux vary with solar activity?

Nice graph.  Although the next few solar cycles WERE more active than 24, cycle 20 is also CLEARLY more active than cycle 20.  But trolls don't swallow facts, so I predict no admission of this simple truth from him.

cycle 20 is also CLEARLY more active than cycle 20"??

Yep.  I made a mistake.  I should have said "cycle 20 is also CLEARLY more active than cycle 24".

See how easy that is?

So the article stating that cycle 20 was not as active as later cycles is wrong also?

Of course not, as I NOWHERE made any inference to such a thing.  And regardless, due to the fact that cycle 20 WAS more active than cycle 24, the cycles in-between were irrelevant.  It seems you are now trying to fork along the troll path to argue semantics rather than logic.  Soon you are going to demand a toll.

[timfinch]

As a non-physicist how am I doing? Anyone care to calculate probabilities?

The main mechanism at GCR energies is fragmentation of the proton. The proton will interact with the nuclei of atoms and produce a shower of pions and a neutron. The pions will quickly decay in leptons and muons, with gamma being produced. There will also be bremstrahlung. It really is very complicated, but the main result is a a neutron, a lot neutrinos, some muons and then electrons/positrons are produced. The latter can are normally produced through pair production.

There's no NASA cabal as our friend suggests. In fact there are several NASA article that discuss the primary shower of proton fragmentation and the production of pions. There is also fragmentation of heavier nuclei in the GCR.

The whole idea of the GCR being captured by nuclei to synthesise radio isotopes is a little barking. neutron capture is a possibility, but with light elements found in rocks, the cross sections are very low, and you have to get right down to thermal energies for it to occur. A the relativistic energies we are discussing the cross sections fall by several orders of magnitude for light elements. For most elements it is zero.

That is some mighty fine horse defecation you spouted there, sir.  If I had no interest in the subject matter I might have been impressed.  I am impressed with the size of your pile.  It is impressive.

[timfinch]

https://www.lpi.usra.edu/meetings/leag2012/presentations/Stubbs.pdf

...and? What are you trying to show me, other then Cycle 20 was a more active time for the Sun than when the current CRaTER data was collected in cycle 24? So the three questions still remain:

• Have you interrogated the CRaTER data?
• How can you extrapolate between cycle 24 and 20?
• How does GCR flux vary with solar activity?

Nice graph.  Although the next few solar cycles WERE more active than 24, cycle 20 is also CLEARLY more active than cycle 20.  But trolls don't swallow facts, so I predict no admission of this simple truth from him.

cycle 20 is also CLEARLY more active than cycle 20"??

Yep.  I made a mistake.  I should have said "cycle 20 is also CLEARLY more active than cycle 24".

See how easy that is?

So the article stating that cycle 20 was not as active as later cycles is wrong also?

Of course not, as I NOWHERE made any inference to such a thing.  And regardless, due to the fact that cycle 20 WAS more active than cycle 24, the cycles in-between were irrelevant.  It seems you are now trying to fork along the troll path to argue semantics rather than logic.  Soon you are going to demand a toll.

Cycle 24 is after cycle 20.  If it is less active than cycle 20 then the statement cannot be correct.  So what is it?

[MBDK]

Secondary Flux on the Moon
Energetic particles and neutrons from cosmic rays induce nuclear reactions with target nuclei in the lunar regolith. Solar cosmic ray-produced secondaries are much less abundant than galactic cosmic ray-produced secondaries and occur primarily in the upper decimeter of the regolith. Since it is the energy of the incident particle that determines what reactions will occur, the GCR particles are of most concern. Typical particles with energies at MeV levels will induce reactions with an interaction mean free path of about 100 g cm-2. Thus, even GCR particles will interact with lunar surface materials at depths <5 m.

During the nuclear reactions (E >10 MeV) secondary particles are emitted; the original particle may emerge at a lower energy. Secondary neutrons and high energy particles can cause additional reactions. It is the secondary particles, especially the neutrons caused by GCR, that are relevant.

Solar wind particles are typically of such low energy that they penetrate no more than a micrometer. They can produce sputtered particles and can induce crystal damage. Most solar cosmic rays are stopped by ionization within the upper few cm of the regolith. The associated heavy nuclei are stopped in the outer millimeter. The main reactions produced by solar cosmic ray particles occur in the upper cm of the regolith, and few secondary particles are released.

Heavy nuclei in GCR radiation are usually stopped at depths <10 cm due to ionization energy loss, with most radiation damage occurring in the upper few cm. Shielding at a few g cm-2 is typically sufficient to remove most of the highly ionized heavy GCR nuclei. The lighter primary nuclei are more penetrating than heavier nuclei. Secondaries may be ionizing particles or uncharged, e.g. neutrons. The cascade that results from interaction depends on the energy of the incident particle and the nature (average atomic number) of the interacting material but can extend to depths of meters. Neutrons produced on the Moon typically have energies of a few MeV and travel until they interact or escape. Neutron interaction is most efficient with elements whose mass is lower than oxygen. Because such elements have relatively low concentrations (Table II), neutrons lose energy slowly and require many collisions to reach thermal energies (<0.1 eV).

https://www.lpi.usra.edu/wiki/lunaref/index.php/Lunar_Ionizing_Radiation_Environment


Moon dust is radioactive and this article is the definitive proof.  The  radiation reflected from the Moon raise the Background radiation in orbit around the Moon 30 to 40 percent.  Think about that for a minute.  The surface of the moon is so radioactive that it increases the radiation in the lunar orbit by 30 to 40 percent.  That is staggering.

Once again, his own source refutes him.  From the above reference:
"The ionizing radiation environment at the Moon, both in orbit and on the surface, consists of the solar wind, solar particle events (SPE, also referred to as solar cosmic rays) and galactic cosmic radiation."

Please note the absence of "radioactive Moon dust" as being included as part of the Moon's radiation environment.  This is because that dust's temporary radioactivity is caused by the GCR's secondary events - NOT neutron capture that makes the elements unstable, and thus causes them to be considered radioactive.  This has been previously explained, but like any good troll, he ignores that fact.

Am I to believe that you think only neutron capture is responsible for nuclear instability?  So you don't believe High energy particles and rays can cause fission?

As per my statement that you just quoted - not in any significant number so as to be considered a significant source.  Now quit trying to obfuscate the subject and explain what part of the CRaTER data I highlighted is above .2mGy/day.

[MBDK]

https://www.lpi.usra.edu/meetings/leag2012/presentations/Stubbs.pdf

...and? What are you trying to show me, other then Cycle 20 was a more active time for the Sun than when the current CRaTER data was collected in cycle 24? So the three questions still remain:

• Have you interrogated the CRaTER data?
• How can you extrapolate between cycle 24 and 20?
• How does GCR flux vary with solar activity?

Nice graph.  Although the next few solar cycles WERE more active than 24, cycle 20 is also CLEARLY more active than cycle 20.  But trolls don't swallow facts, so I predict no admission of this simple truth from him.

cycle 20 is also CLEARLY more active than cycle 20"??

Yep.  I made a mistake.  I should have said "cycle 20 is also CLEARLY more active than cycle 24".

See how easy that is?

So the article stating that cycle 20 was not as active as later cycles is wrong also?

Of course not, as I NOWHERE made any inference to such a thing.  And regardless, due to the fact that cycle 20 WAS more active than cycle 24, the cycles in-between were irrelevant.  It seems you are now trying to fork along the troll path to argue semantics rather than logic.  Soon you are going to demand a toll.

Cycle 24 is after cycle 20.  If it is less active than cycle 20 then the statement cannot be correct.  So what is it?

Yep, the monster's on to semantics now.  Gives a reference written prior to cycle 24 and expects it to remain true unto eternity. 

Time to do something productive again.  Tim is just having a laugh in his own warped mind.  Cheers.

[Luke Pemberton]

Am I to believe that you think only neutron capture is responsible for nuclear instability?

From high energy GCR, no. The primary mechanism is nuclear spallation, not fission. Fission has a very specific mechanism in physics, and pertains to capture of a slow neutron in certain heavy elements.

As your article informs you, secondary neutrons are the most relevant secondary radiation. If you research the literature further, you'll find pions and nuclear fragments are produced, but the relevant secondary radiation to this discussion is spallalted neutrons.

Why do you think that pre-space age we measured solar storm activity using ground based neutron monitors? What causes an influx of neutrons in abundance to measure solar storm activity.

So you don't believe High energy particles and rays can cause fission?

Less likely owning to the cross section decreasing considerably at relativistic energies associated with GCR. There's a small issue of quantum mechanics to consider to being with, as the interactions are taking place at the nuclear level, so via the strong force. Your idea that these interactions/processes occur equally at all energies across all isotopes is very wrong.

[molesworth]

Ah, I wasn't expecting a return to the debate!!

I do have a question for Mr Finch, as regards the measured, or generally accepted figures for radiation levels in space beyond the VAB.  (I originally brought it up in post #550, but I'll summarise here as well.)

I work for a company which develops data handling technologies* for spacecraft.  I'm on the software side of things, but I know our chip design folks have to consider a lot of factors about the environment their designs will be used in.  Since the data they're using is based on the generally accepted measurements and models, why aren't there a lot more failures of missions operating in these regions?

As I also noted in my previous post, it's not just NASA that's involved in determining radiation risks, but private companies and other organisations in the US, and around the world, and even small independent groups like the Lunar X-Prize teams.

Either :
a) the failure rates are being covered up, or
b) all the engineers, all over the world, are in some great conspiracy to lie about the figures, or
c) all missions outside of LEO are fakes, or
d) the space radiation environment has been correctly measured and modelled, and allows for safe design of both manned and unmanned missions

Which, in your opinion, is the explanation?


[ * The same technology has been used on well over 100 missions, including LRO, MRO and Mars Express, and will launch on BepiColombo, JWST and several other upcoming spacecraft.]

The technology obviously exist to operate electronic equipment in the SAA and passing through the VAB.  Missions in this high radiation background have shorter life expectancies than missions that remain in LEO.  I can't begin to answer your question without comparative data.  I am sure redundancy and hardened equipment was used in designing electronic equipment for the hazards of space.  What has any of this to do with my claim that Apollo 11's mission dose is unrealistic in light of recent empirical data?

Ah, the joys of being in a different time zone... 

The relevance to the Apollo missions is that the data used for shielding, design of rad-hard electronics etc. is based on the measurements over many years, starting pre-Apollo.  The published, currently available data, which has been used for many, many missions, shows that the environment outside LEO and the VAB is not as hostile as you claim, and certainly not enough to prevent manned lunar missions.

You're claiming that this data, used by engineers in many countries, is incorrect, and misrepresents the actual environment, but the success and reliability of missions to the Moon, Mars and beyond, to Lagrange points etc. says otherwise.

Perhaps you ought to familiarise yourself with spacecraft reliability and failure data, because radiation damage is not the primary cause of mission failures (even ignoring launch failure and human errors).

[timfinch]

MBDK,  You have what we used to call in the Nuclear Navy, "A gross conceptual error" or "GCE".  98% of GCR is comprised of heavy ions and 85% which are protons.  If protons are not capable of causing fission then where are all the neutrons coming from?

[Luke Pemberton]

If protons are not capable of causing fission then where are all the neutrons coming from?

Nuclear spallation. Fission is something entirely different.

[timfinch]

Ah, I wasn't expecting a return to the debate!!

I do have a question for Mr Finch, as regards the measured, or generally accepted figures for radiation levels in space beyond the VAB.  (I originally brought it up in post #550, but I'll summarise here as well.)

I work for a company which develops data handling technologies* for spacecraft.  I'm on the software side of things, but I know our chip design folks have to consider a lot of factors about the environment their designs will be used in.  Since the data they're using is based on the generally accepted measurements and models, why aren't there a lot more failures of missions operating in these regions?

As I also noted in my previous post, it's not just NASA that's involved in determining radiation risks, but private companies and other organisations in the US, and around the world, and even small independent groups like the Lunar X-Prize teams.

Either :
a) the failure rates are being covered up, or
b) all the engineers, all over the world, are in some great conspiracy to lie about the figures, or
c) all missions outside of LEO are fakes, or
d) the space radiation environment has been correctly measured and modelled, and allows for safe design of both manned and unmanned missions

Which, in your opinion, is the explanation?


[ * The same technology has been used on well over 100 missions, including LRO, MRO and Mars Express, and will launch on BepiColombo, JWST and several other upcoming spacecraft.]

The technology obviously exist to operate electronic equipment in the SAA and passing through the VAB.  Missions in this high radiation background have shorter life expectancies than missions that remain in LEO.  I can't begin to answer your question without comparative data.  I am sure redundancy and hardened equipment was used in designing electronic equipment for the hazards of space.  What has any of this to do with my claim that Apollo 11's mission dose is unrealistic in light of recent empirical data?

Ah, the joys of being in a different time zone... 

The relevance to the Apollo missions is that the data used for shielding, design of rad-hard electronics etc. is based on the measurements over many years, starting pre-Apollo.  The published, currently available data, which has been used for many, many missions, shows that the environment outside LEO and the VAB is not as hostile as you claim, and certainly not enough to prevent manned lunar missions.

You're claiming that this data, used by engineers in many countries, is incorrect, and misrepresents the actual environment, but the success and reliability of missions to the Moon, Mars and beyond, to Lagrange points etc. says otherwise.

Perhaps you ought to familiarise yourself with spacecraft reliability and failure data, because radiation damage is not the primary cause of missions failures (even ignoring launch failure and human errors).

Why would I.  I have made no claims about mission survivability.  I don't even claim that the radiation hazards are insurmountable.  The only claim I make and am willing to defend is the mission doses of Apollo 11 do not represent realistic values in light of current data.  Anything else is yours.

[Luke Pemberton]

98% of GCR is comprised of heavy ions and 85% which are protons.

What is the other -83% made from?

[timfinch]

If protons are not capable of causing fission then where are all the neutrons coming from?

Nuclear spallation. Fission is something entirely different.

Technically you would be correct.  Different bullet same gun, same result.  How does Spallation reduce the neutron radiation on the surface of the moon?  GCR's are the source of the neutrons and the radioactivity of the moon's surface.