Radiation

[mako88sb]

The thing that gets me about moon mission are the unknowns that have come to light over the years....

Well, microbursts were not identified as an aviation hazard until the mid 70's. All those decades before that with people flying about close to airports putting themselves at risk not knowing about the potential for disaster.

[bknight]

The thing that gets me about moon mission are the unknowns that have come to light over the years....

Well, microbursts were not identified as an aviation hazard until the mid 70's. All those decades before that with people flying about close to airports putting themselves at risk not knowing about the potential for disaster.

Ah yes I remember AA flight 181 2 Aug 85 near DFW.
https://en.wikipedia.org/wiki/Delta_Air_Lines_Flight_191

[raven]

The thing that gets me about moon mission are the unknowns that have come to light over the years....

Well, microbursts were not identified as an aviation hazard until the mid 70's. All those decades before that with people flying about close to airports putting themselves at risk not knowing about the potential for disaster.

Ah yes I remember AA flight 181 2 Aug 85 near DFW.
https://en.wikipedia.org/wiki/Delta_Air_Lines_Flight_191

It feels weird that we only knew about that after we finished* landing humans on the moon.
As for inconceivable's claims, don't really have anything to add that hasn't been said, except they show a typical lack of knowledge.
*As of 2018

[Luke Pemberton]

It wouldn't help.  You're thinking of laminated armor that uses alternate layers of dense and sparse material.  It's actually how the micrometeoroid shield on the Apollo LM was designed, and to a lesser extent the space suits.  It works for ballistic particles where "particle" here means dust, not some exotic thing ending in -on.  The theory behind laminated armor is that the collisions with the hard outer layers fragment (in a mechanical, not subatomic, way) both the injectile and the armor.  The soft inner layers (if they aren't just empty space) attenuate the velocity, but what they really do is provide distance for the collision products to fan out and vent their energy on the next hard layer across a broader surface area.

Pretty much how modern tank armour works, along with the angle of the armour. A trip to Bovington Tank Museum is well worth a trip to see the WW1 tanks if anyone is in the Dorset area of England. The first tanks were built with metal plate, the issue being that when a bullet hit the plate, it would blister the metal on the inside as there was no laminating. The little blister could produce a shard that would ping around the inside of the tank. The other issue being the crew were pretty much choked by the exhaust gases from the engine.

[Obviousman]

The thing that gets me about moon mission are the unknowns that have come to light over the years....

Well, microbursts were not identified as an aviation hazard until the mid 70's. All those decades before that with people flying about close to airports putting themselves at risk not knowing about the potential for disaster.

Oh yes. I remember the stuff we did flying in the 1980s. We were not trying to be unsafe but now when we look back, we are amazed that we actually lived through some stuff.

[timfinch]

FYI.

[Luke Pemberton]

FYI.

Good, so after a thread that has run over 1000 replies you finally calculated the median, which show the dose falls below your arbitrary threshold levels. I congratulate your honesty.

Now explain why the mean average and median are very different. The clue might be in the standard deviation and the SPEs. If I have a very large number that appears a few times, and lots of very little numbers, would you expect the mean to be skewed compared to the median?

Calculate the average of 1000    1      1      1      1      1      1     1      1

Now, calculate the median for the same data.

An 8th grader will do this and understand why the answers are very different.

Further, why not take the average and mean over part of the cycle that is nearer to solar maximum where Apollo missions too place.

This is rather academic anyway, as you need to look at the data for solar cycle 20.

[timfinch]

FYI

[timfinch]

KREEP
The lunar geochemical component KREEP contains trace amounts of the radioactive elements Thorium and Uranium. Regolith dust formed from this rock is a serious health hazard.

The radiation given off is Alpha particles (helium nuclei) and they do not penetrate very effectively. The direct radiation is stopped by any pressure vessel wall and even a well designed layer of spacesuit material. The problem is that if the dust is ingested into the human body, the particles will lay directly on lung or intestine tissue and are carcinogenic. Ingestion of the dust must therefore be rigorously limited.

KREEP is concentrated in the Oceanus Procellarum (Ocean of Storms) and Mare Imbrium (Sea of Rains) with a major concentration south of Crater Copernicus. This region covers about 40% of the Earth-facing side of the Moon. Based on the small number of lunar samples returned, low KREEP regions measure 8% or less of the radioactive elements in their dust compared to the high KREEP regions. With current technology, the entire high KREEP region is not acceptable for any long-term human settlement or manned mining operation.

The high KREEP region contains many sites of interest to science, particularly those of volcanic origin. Even short scientific expeditions there will require special procedures to prevent ingestion of dust and the removal of dust from all returning equipment.

Radon Gas
Another source of dangerous radiation is the radon gas that is created in the decay of trace amounts of uranium found naturally in lunar rocks. This gas is very heavy and concentrates in low areas. This type of radiation is easily stopped by even a thin layer of material, but radon is carcinogenic if ingested directly into the body.

Even though sensitive scientific equipment has been able to detect radon on Luna, the quantity of radon gas is such that it can be ignored. The lunar atmosphere is so thin that the most massive component, Argon, is present in only 30,000 particles per cubic centimeter, that is 2 trillionths of a gram per cubic meter. Radon is so scarce that it is not even mentioned in the list of components in the lunar atmosphere article. See the Moon Fact Sheet from NASA.

Radon has also been detected from lunar outgassing events.

http://lunarpedia.org/index.php?title=Radiation_Problem

[timfinch]

Abstract
During a stay on the moon humans are exposed to elevated radiation levels due to the lack of substantial atmospheric and magnetic shielding compared to the Earth's surface. The absence of magnetic and atmospheric shielding allows cosmic rays of all energies to impinge on the lunar surface. Beside the continuous exposure to galactic cosmic rays (GCR), which increases the risk of cancer mortality, exposure through particles emitted in sudden nonpredictable solar particle events (SPE) may occur. SPEs show an enormous variability in particle flux and energy spectra and have the potential to expose space crew to life threatening doses. On Earth, the contribution to the annual terrestrial dose of natural ionizing radiation of 2.4 mSv by cosmic radiation is about 1/6, whereas the annual exposure caused by GCR on the lunar surface is roughly 380 mSv (solar minimum) and 110 mSv (solar maximum). The analysis of worst case scenarios has indicated that SPE may lead to an exposure of about 1 Sv. The only efficient measure to reduce radiation exposure is the provision of radiation shelters. Measurements on the lunar surface performed during the Apollo missions cover only a small energy band for thermal neutrons and are not sufficient to estimate the exposure. Very recently some data were added by the Radiation Dose Monitoring (RADOM) instrument operated during the Indian Chandrayaan Mission and the Cosmic Ray Telescope (CRaTER) instrument of the NASA LRO (Lunar Reconnaisance Orbiter) mission. These measurements need to be complemented by surface measurements. Models and simulations that exist describe the approximate radiation exposure in space and on the lunar surface. The knowledge on the radiation exposure at the lunar surface is exclusively based on calculations applying radiation transport codes in combination with environmental models. Own calculations are presented using Monte-Carlo simulations to calculate the radiation environment on the moon and organ doses on the surface of the moon for an astronaut in an EVA suit and are compared with measurements. Since it is necessary to verify/validate such calculations with measurement on the lunar surface, a description is given of a radiation detector for future detailed surface measurements. This device is proposed for the ESA Lunar Lander Mission and is capable to characterize the radiation field concerning particle fluencies, dose rates and energy transfer spectra for ionizing particles and to measure the dose contribution of secondary neutrons.

http://adsabs.harvard.edu/abs/2012P%26SS...74...78R

[Luke Pemberton]

KREEP
The lunar geochemical component KREEP contains trace amounts of the radioactive elements Thorium and Uranium. Regolith dust formed from this rock is a serious health hazard.

The radiation given off is Alpha particles (helium nuclei) and they do not penetrate very effectively. The direct radiation is stopped by any pressure vessel wall and even a well designed layer of spacesuit material. The problem is that if the dust is ingested into the human body, the particles will lay directly on lung or intestine tissue and are carcinogenic. Ingestion of the dust must therefore be rigorously limited.

KREEP is concentrated in the Oceanus Procellarum (Ocean of Storms) and Mare Imbrium (Sea of Rains) with a major concentration south of Crater Copernicus. This region covers about 40% of the Earth-facing side of the Moon. Based on the small number of lunar samples returned, low KREEP regions measure 8% or less of the radioactive elements in their dust compared to the high KREEP regions. With current technology, the entire high KREEP region is not acceptable for any long-term human settlement or manned mining operation.

The high KREEP region contains many sites of interest to science, particularly those of volcanic origin. Even short scientific expeditions there will require special procedures to prevent ingestion of dust and the removal of dust from all returning equipment.

Radon Gas
Another source of dangerous radiation is the radon gas that is created in the decay of trace amounts of uranium found naturally in lunar rocks. This gas is very heavy and concentrates in low areas. This type of radiation is easily stopped by even a thin layer of material, but radon is carcinogenic if ingested directly into the body.

Even though sensitive scientific equipment has been able to detect radon on Luna, the quantity of radon gas is such that it can be ignored. The lunar atmosphere is so thin that the most massive component, Argon, is present in only 30,000 particles per cubic centimeter, that is 2 trillionths of a gram per cubic meter. Radon is so scarce that it is not even mentioned in the list of components in the lunar atmosphere article. See the Moon Fact Sheet from NASA.

Radon has also been detected from lunar outgassing events.

http://lunarpedia.org/index.php?title=Radiation_Problem

All taken from an article that discusses using the rocks and regolith as a shelter for prolonged missions, so naturally the hazard will be discussed for a very important reason:

You do know that approx 50% of natural background radiation on Earth is attributed to rocks. In some areas of the UK, where the bedrock is mainly granite, radioactive radon is produced when radioisotopes in the atoms of rocks decay. There is a small increases in the lung cancer incidence on those areas. It is believed it may be due to the radon emitting alpha particle in the lungs during inhalation and exhalation. So if you are going to build a shelter from the moon's regolith, you are naturally going to want to understand the risks.

No one said that the moon was not radioactive, we were explaining to you that the influx of GCR does not turn the moon into a radioactive wasteland. The activity, duration of the missions and accumulated dose all play a part in total dose.

Interesting you article discusses alpha particles. How well do you think an astronaut in a suit will be protected from alpha exposure?

[Luke Pemberton]

FYI

You've hung yourself by your own petard here haven't you? The doses are measured using the data from a neutron ground based monitor. By inspection, I make the ground dose around 0.35 - 0.50 mGr/day. Again, this is taken in solar cycle 24, which is less active than 20.

Further, can you directly compare the detectors between this these ground based monitors and monitors and CRaTER? They use different materials.

I'm going to throw this out for others on the forum, but is it possible for the dose on the Earth's surface to be greater than the moon's surface. The GCR has a thick layer of atmosphere to traverse, increasing the number of secondary neutrons and mesons produced? Just a thought.

[timfinch]

In 1972, Apollo astronaut Harrison Schmitt sniffed the air in his Lunar Module, the Challenger. "[It] smells like gunpowder in here," he said. His commander Gene Cernan agreed. "Oh, it does, doesn't it?"

The two astronauts had just returned from a long moonwalk around the Taurus-Littrow valley, near the Sea of Serenity. Dusty footprints marked their entry into the spaceship. That dust became airborne--and smelly.


see caption

Right: Moonwalking astronaut Harrison Schmitt. [More]
Later, Schmitt felt congested and complained of "lunar dust hay fever." His symptoms went away the next day; no harm done. He soon returned to Earth and the anecdote faded into history.

https://science.nasa.gov/science-news/science-at-nasa/2005/22apr_dontinhale

[Luke Pemberton]

In 1972, Apollo astronaut Harrison Schmitt sniffed the air in his Lunar Module, the Challenger. "[It] smells like gunpowder in here," he said. His commander Gene Cernan agreed. "Oh, it does, doesn't it?

Are you suggesting that radioactive dust smells more than a non-radioactive counterpart, or that they were simply exposed to dust?

Again, provide a figure for the activity of the dust. being exposed to GCR does not make the dust radioactive to the point that it affords a hazard.

[Luke Pemberton]

Copying and pasting swathes of text that you do not understand does not support an argument. You need to begin to answer questions that are posed and address your understanding of the text you are cutting and pasting. I'm very patient. There are others here who frown on this intellectual cowardice.