Radiation in Space

[Astronuc]

One of the major concerns is space is the radiation levels.  In addition to gamma-rays and X-rays, and electrons and other subatomic partices, ions present a problem.

Ions have two sources:

1) primary source - cosmic radiation, and

2) secondary source - ions formed from structural materials, either from atomic nuclei being knocked out of the material, or from spallation reactions.  In spallation, an atomic nucleus is blown apart much like fission.

Here are some diagrams which describe some of the issues.

1) The first show ionization tracks.  The heavier the ion and the greater the charge (Z) on the nucleus - the more ionization it does - and the more damage.

2) Galactic cosmic radation (GCR) spectrum data.

3) A comparsion of some shielding responses.

Prolonged exposure to such radiation will adversely impact the health of an astronaut.  Long term travel in space would require signifiant shielding to basically eliminate this radiation - but shielding adds mass that requires energy and propellant to move.  Besides radiation, the effect of zero gravity must be addressed.

[Mental Avenger]

In a recent discussion on the effects of radiation at Chernobyl, I came across some information that suggests that the tolerated levels of radiation may be a lot higher than currently widely published.  It seems that almost everyone just copied the results of one study and didn’t bother to find out how accurate they were.

There are places all over the Earth where the natural, local radiation is far higher than the average, perhaps 10 times higher than the “max whole body limit of 50mSv/yr” in some locations, even higher in others.  The people of those regions are generally healthy, sometimes relatively long-lived.  There is information that suggests that continuous moderate doses of radiation make actually promote good health and increase longevity.

The point is, perhaps we wont’ need nearly as much shielding as was previously thought.

[Astronuc]

The point is, perhaps we wont’ need nearly as much shielding as was previously thought.

The data I posted come from a NASA study.  A colleague at NASA provided these data, and made the comment that astronauts (ISS and Shuttle) were experiencing some harmful effects more than had been anticipated.

There are places all over the Earth where the natural, local radiation is far higher than the average, perhaps 10 times higher than the “max whole body limit of 50mSv/yr” in some locations, even higher in others.  The people of those regions are generally healthy, sometimes relatively long-lived.  There is information that suggests that continuous moderate doses of radiation make actually promote good health and increase longevity.

By all means, please provide the evidence or studies that support the idea of positive effects of radiation on health and longevity.

[Mental Avenger]

I’ll have to relocate the links.  A major computer crash several months ago wiped out a lot of the data I thought I had saved.

The short version, however, is that moderate doses of radiation may trigger the immune system very early in life to begin fighting diseases, long before the immune system is triggered into action by actual diseases. .  It sort of gives the immune system a running start at many diseases before they can attack.

[Astronuc]

I have seen articles on radiation and chemical hormesis ( http://en.wikipedia.org/wiki/Hormesis ), that is small doses of radiation or harmful chemicals may trigger a positive (immune) response in some organisms.  It been a while since I have read anything, so I'd have to go back and refresh my memory.

[yale]

Panel Affirms Radiation Link to Cancer
- June 29, 2005 (AP) --


Even very low doses of radiation pose a risk of cancer over a person's lifetime, a National Academy of Sciences panel concluded.  (Committee on Biological Effects of Ionizing Radiation or BEIR-VII) It rejected some scientists' arguments that tiny doses are harmless or may in fact be beneficial.


The findings, disclosed in a report Wednesday, could influence the maximum radiation levels that are allowed at abandoned reactors and other nuclear sites and raises warnings about excessive exposure to radiation for medical purposes such as repeated whole-body CT scans.


"It is unlikely that there is a threshold (of radiation exposure) below which cancers are not induced," the scientists said.


While at low doses "the number of radiation-induced cancers will be small ... as the overall lifetime exposure increases, so does the risk," the experts said.

Even common X-rays pose some risk of adverse health effects, the scientists found, although the panel said there was not enough information available to accurately estimate the cancer risk from X-rays. Nevertheless, the report said, there is evidence that per unit of absorbed radiation, X-rays may be more dangerous than other radiation.


The panel also said that approximately one person out of 1,000 would develop cancer from exposure to the amount of radiation from a single, average whole body CT-scan.


But the report should not scare people away from nuclear medicine, said Dr. Henry Royal, a professor of radiology at Washington University in St. Louis. He said most often the benefits of such tests and treatments outweigh the risks.


But Royal also said that procedures such as CT scans should be used to deal with a specific medical problems and not part of annual medical screenings. "You should not be exposed to radiation for superficial reasons," Royal said in a telephone interview.


Scientists for years have debated how extremely low doses of radiation affect human health.


Pro-nuclear advocates, as well as some independent scientists, have maintained that the current risk models for low-level radiation has produced more stringent requirements than is necessary to protect public health.


It is an issue in determining decontamination requirements at abandoned reactors and at federal weapons sites.


The academy's panel stood by the "linear, no threshold" model that generally is the acceptable approach to radiation risk assessment. This approach assumes that the health risks from radiation exposure decline as the dose levels drop, but that each unit of radiation — no matter how small — is assumed to cause cancer.

"The scientific research base shows that there is no threshold of exposure below which low levels of ionizing radiation can be demonstrated to be harmless or beneficial," said Richard R. Monson, the panel's chairman. He is a professor of epidemiology at Harvard's School of Public Health.

The panel said new and more extensive data developed over the past 15 years only strengthen the conclusions of the panel's last report, in 1990, on low-level radiation risks.


The scientists estimated that one out of 100 people exposed to 100 millisievert of radiation over a lifetime probably would develop solid cancer or leukemia, and that half of those cases would be fatal.


It also said that 42 additional cancers can be expected in the same group from other than low-level radiation sources.


A millisievert is a measurement of radiation energy deposited in a living tissue. People absorb about 3 millisievent of radiation annually from natural sources and 0.1 millisivert every time they get a chest X-ray.


The report noted that exposure from a whole body CT scan is about 10 millisievert, much higher than a normal X-ray.


Some anti-nuclear advocates said the study reaffirms that stringent regulations are needed when cleaning up abandoned nuclear sites or considering health risks near nuclear power plants.


"The NAS panel puts to rest once and for all claims that low doses of radiation aren't dangerous ... nuclear advocates have been making this claim for years" said Daniel Hirsch, president of Committee to Bridge the Gap, a Los Angeles-based nuclear watchdog group.


Mitchell Singer, a spokesman for the Nuclear Energy Institute, the industry's lobbying arm, said the report "is a positive finding. It shows there is very little risk of exposure from low levels of radiation."


The academy is a private organization chartered by Congress to advise the government of scientific matters.

www.nationalacademies.org

[Mental Avenger]

I understand that a study of one is not scientifically compelling, however……..

Back in the 60’s the Cold War produced a lot of paranoia and resulted in rather futile efforts by the US government to prepare us for the possibility of attack by nuclear weapons.  As part of the Civil Defense program, radiation monitoring stations were set up all over the US.  We were chosen to be one of those Civil Defense Monitoring Stations.

We were given a CD V777A kit that was part of our Civil Defense Monitoring Station equipment.  It contained a CD V-717, a CD V-700, and a CD V-715, along with dosimeters and a dosimeter charger.  We were encouraged to familiarize ourselves with the equipment, so we took them out into the hills across the creek to see what we could find.  Background radiation was minimal until we came to the half-underground “rock House” we had dug into the side of a hill. We had dug into the back, which was easy because it was filled with soft grey clay.   The meter on the CD V-700 pegged on the high scale (0-50 miliroentgens/hour) so we went back and got the CD V-715.  IIRC, the reading varied around the middle of the second scale, 0-50 roentgens/hour.  That is a respectable reading from what turned out to be uranium ore. 

We had played often in that hut, so we were all apparently exposed to some fairly high levels of radiation for many years. As a point of fact, I have been exposed to levels of radiation that the PTB claim would cause all sorts of severe problems.  Unless this is a dream, I am still alive and quite well.  Why is that?

Today, almost everyone takes me for someone at least 10 years younger than I am.  My doctor says the he thinks I will live to be 100.   Most tests show that my physiological levels are on the healthy end for someone at least 10 years younger.  My hearing sensitivity was literally off the charts, registering up in the heading area of the chart.  I have always healed from injuries extremely quickly, almost unnaturally so. 

A coincidence of some kind, I guess.

[Astronuc]

The figures in the first post can be found in:

NASA Conference Publication 3360
Shielding Strategies for Human Space Exploration
December 1997

Edited by
J. W. Wilson
Langley Research Center • Hampton, Virginia

J. Miller
Lawrence Berkeley National Laboratory • Berkeley, California

A. Konradi
Lyndon B. Johnson Space Center · Houston, Texas

F. A. Cucinotta
Langley Research Center • Hampton, Virginia

Proceedings of a workshop sponsored by the National Aeronautics and Space Administration and held at Lyndon B. Johnson Space Center, Houston, Texas
December 6–8, 1995
459 pages

[Charles A. Laster]

Very interesting thread. Mental Avenger, you seem to be an old fart like myself, I read nearly everything ever printed by the Civil Defence program, even built a fallout shelter. We also had a lot of soft grey clay, but I never checked its radiation levels. I look and act much younger than I am, heal very quickly, and my daughter wishes my hearing was not so good, but I always attributed it to lucky genes. Do other members of your family have the same traits as you. Looking back, mine do not share these qualities, but it could still be genitic.

As humans are long lived, and the studies done do not cover a large part of the population, I think the jury may still be out on this one. Some people may be able to handle radiation better than others, thanks to their genes. But I would still go with the idea that the less radiation exposed to in ones life the better. Better safe than sorry.

[Astronuc]

Sickening Solar Flares   (11.08.05)

When the biggest solar proton storm in 15 years erupted in January, many were left wondering: what would have happened if astronauts were on the moon?

NASA's new plans include returning to the moon -- not just with robots, but with people too. In the decades ahead we can expect to see habitats, greenhouses and power stations up there. Astronauts will be out among the moondust and craters, exploring, prospecting and building.

On Jan. 20, 2005, though, there were no humans walking around on the moon. And it's a good thing.

On that day, a giant sunspot named "NOAA 720" exploded. The blast sparked an X-class solar flare, the most powerful kind, and hurled a billion-ton cloud of electrified gas (a coronal mass ejection, or CME) into space. Solar protons accelerated to nearly light speed by the explosion reached the Earth-moon system minutes after the flare; it was the beginning of a days-long "proton storm."

Proton storms cause all kinds of problems. They interfere with ham radio communications. They zap satellites, causing short circuits and computer reboots. Worst of all, they can penetrate the skin of space suits and make astronauts feel sick.

January 2005 was a stormy month in space. With little warning, a giant spot materialized on the sun and started exploding. From Jan. 15 through Jan. 19, sunspot 720 produced four powerful solar flares. When it exploded a fifth time on Jan. 20, onlookers were not surprised.

The sun-lit side of the moon is totally exposed to solar flares. It has no atmosphere or magnetic field to deflect radiation. Protons rushing at the moon simply hit the ground or whoever might be walking around outside. An astronaut on the moon, caught outdoors on Jan. 20, would have had almost no time to dash for shelter, and would have become sick. At first, he'd feel fine, but a few days later, symptoms of radiation sickness would appear: vomiting, fatigue, low blood counts. These symptoms might persist for days.

http://www.nasa.gov/mission_pages/stereo/news/stereo_astronauts.html

[Astronuc]

Modelling codes for Solar Protons and Cosmic Radiation

Solar Flare Protons
  SOLPRO Model
  JPL Proton Model

Cosmic Rays and Related Software
  CREME Programs
  Spacecraft Anomaly Data Base

http://modelweb.gsfc.nasa.gov/sun/sun_index.html

[Astronuc]

Solar proton models

http://www.spenvis.oma.be/spenvis/help/background/flare/flare.html

Table of contents

Introduction
Solar proton effects on space systems
Predicting solar proton events
Solar proton models
  The King model
  The JPL model
  The ESP models
Using the solar proton models
  The King model
  The JPL model
Comparison of the King and JPL models
  The ESP models
Geomagnetic attenuation and Earth shadowing
References

Introduction

Together with geomagnetically trapped particles and galactic cosmic rays, solar protons (and other ions) contribute to the terrestrial radiation environment and can present a hazard to both manned spaceflight and to the sensitive components used in satellite subsystems and instrumentation. Depending on the mission requirements of an Earth orbiting spacecraft, it may be possible to use the Earth's magnetic field to shield partially, or even completely, against solar particles. However, on interplanetary trajectories or on high altitude or high latitude Earth orbits, this is clearly not an option.

A number of significant events associated with past solar cycles may have been responsible for several spacecraft operational anomalies. Furthermore, radiation protection is a prime issue for space station operatons, for extended missions to the planet Mars, or for a return visit to the Moon. For these reasons and others, considerable interest has been shown in recent years concerning the prediction of solar proton fluences from data collected during past solar cycles.

[Astronuc]

New techniques for predicting solar proton fluences for radiationeffects applications

Xapsos, M.A.   Summers, G.P.   Shapiro, P.   Burke, E.A.   
Naval Res. Lab., Washington, DC;

This paper appears in: Nuclear Science, IEEE Transactions on
Publication Date: Dec 1996
Volume: 43,  Issue: 6, Part 1
On page(s): 2772-2777
Meeting Date: 07/15/1996 - 07/19/1996
Location: Indian Wells, CA, USA
ISSN: 0018-9499
References Cited: 24
CODEN: IETNAE
INSPEC Accession Number: 5498436
Digital Object Identifier: 10.1109/23.556865
Posted online: 2002-08-06 20:42:59.0
 
Abstract
At geosynchronous altitudes, solar proton events can be a significant source of radiation exposure for devices such as optical imagers, memories and solar cells. These events appear to occur randomly with respect to time and magnitude during the active period of each solar cycle. New probabilistic descriptions, including extreme value theory, are given in forms applicable to assessing mission risks for both single events and the cumulative fluence of multiple events. The analyses yield simpler forms than previous models, include more recent data, and can easily be incorporated into existing computer programs 

[Astronuc]

Engineering Models for Galactic Cosmic Rays and Solar Protons

http://space-env.esa.int/EMA_Events/SPENVIS_WS2002/Proceedings/gabriel.pdf


from

ESA Space Environments & Effects - http://space-env.esa.int/

Space Environment Information System - http://www.spenvis.oma.be/spenvis/

[Astronuc]

Solar Wind (May 8, 2006) - Spaceweather.com - SOHO
speed: 494.4 km/s
density: 0.9 protons/cm³