The Radiation environment and its effect on human spaceflight: A Lunar Mission

Relative monthly infall of galactic cosmic rays from 1958 through December 2012 shows the inverse relationship with solar activity. The highest GCR infall rate (since the beginning of the Space Age) was recorded in late 2009 (arrow), occurring at the same time was the latest and unusually lengthy solar minimum [Moscow Neutron Monitor].

João Sabino
Instituto Superior Técnico
Lisboa, Portugal

This work is an overview of the quantities and concepts common in radiation physics and describes the types of radiation important to planning crewed missions to the Moon. Radiation effects on biological tissue and the consequences to astronaut health are addressed.

The environment of a mission to the Moon was simulated based on data obtained with the CREME program along with data from Lunar Prospector neutron measurements. The virtual mission was divided into stages of a trajectory: Low Earth Orbit, traversing the Van Allen Radiation Belts (VARB), the geostationary orbit radiation environment (GEO), lunar orbit and surface radiation environments. 

Major details in the development of a software application in Geant4 (CERN) are presented. The application was used to reproduce the transport of radiation particles through matter, to simulate the physics involved and to obtain the resulting absorbed dose, equivalent dose and the spectre of secondary radiation. The quantities were evaluated for solar minimum, solar maximum, and solar conditions wre evaluated for each mission phase.

The radiation environment in the solar system presents the main constraint to human spaceflight outside Earth's protecting radiation belts.

As the human presence in space tends to increase, or the will to reach other planets grows, radiation in space becomes a more compelling obstacle that needs to be dealt with. The risks that radiation exposure presents to space missions directly effects mission planing. For this reason a good knowledge of the radiation environment in all mission phases is essential. Development of reliable prediction tools is of major importance to assist mission planing and assure minimum safety for the crew.

This work pretends to explain subjects that need to be taken into account to understand problems space radiation pose to human spaceflight, taking as an example the case of a real lunar mission scenario and also documenting the development of software simulating the radiation environment and analyzing the effects of exposure.

Robotic space exploration looks promising in the immediate future, but despite huge advantages many scientists acknowledge it is not sufficient alone, that humans are needed in space to perform more complex research tasks such as field geology and the acquisition and analysis of samples.

This is a strong incentive towards human spaceflight and also a natural drive based on curiosity and adventure the human being has shown in this kind of challenge that lead us to go farther and farther; not to mention technological and industrial advancements always associated with meeting such challenges. Nowdays, even the tourism industry has begun to recognize space as an interesting destination for the wealthy, and some companies have already flown tourists to the International Space Station.

Human space exploration beyond LEO is presumably going to reemerge very soon, especially if some of the present risk it poses are minimized.

Download or read the study (pdf), HERE.

Cosmic ray flux effects lunar ice (March 19, 2012)
“a perfect storm of cosmic rays” (September 29, 2009)
Cosmic rays and manned space travel (September 16, 2009)
Cosmic ray flux highest ever recorded (September 3, 2009)
LUNAR-TEX radiation blanket: Skeptical (May 11, 2009)

Managing Space Radiation Risk in the New Era of Space Exploration (2008)
Committee on the Evaluation of Radiation Shielding for Space Exploration
National Research Council

PETA protests target radiation testing

Dave Wedge
Boston Herald

While about two dozen animal rights supporters gathered outside McLean Hospital in Belmont this morning to protest controversial radiation tests on monkeys, researchers defended the testing as adhering to government guidelines.

Wearing T-shirts and holding signs, People for the Ethical Treatment of Animals members voiced their opposition to a NASA project that will zap about 20 squirrel monkeys with radiation. The primates will be hit with radiation doses equivalent to three years of space travel at a New York facility and then will be shipped to McLean to live under the watch of Harvard Medical School researchers.

PETA officials say the testing is cruel because it could lead to cancer, premature aging and cognitive damage in the monkeys. Six PETA protesters donned monkey masks and sat in cages during the peaceful protest.

Follow this story HERE.

Yet another prediction for Solar Cycle 24

An international panel of experts led by NOAA and sponsored by NASA has released a new prediction for the next solar cycle. Solar Cycle 24 will peak, they say, in May 2013 with a below-average number of sunspots.

"If our prediction is correct, Solar Cycle 24 will have a peak sunspot number of 90, the lowest of any cycle since 1928 when Solar Cycle 16 peaked at 78," says panel chairman Doug Biesecker of the NOAA Space Weather Prediction Center.

It is tempting to describe such a cycle as "weak" or "mild," but that could give the wrong impression.

"Even a below-average cycle is capable of producing severe space weather," points out Biesecker. "The great geomagnetic storm of 1859, for instance, occurred during a solar cycle of about the same size we’re predicting for 2013."

The 1859 storm--known as the "Carrington Event" after astronomer Richard Carrington who witnessed the instigating solar flare--electrified transmission cables, set fires in telegraph offices, and produced Northern Lights so bright that people could read newspapers by their red and green glow. A recent report by the National Academy of Sciences found that if a similar storm occurred today, it could cause $1 to 2 trillion in damages to society's high-tech infrastructure and require four to ten years for complete recovery. For comparison, Hurricane Katrina caused "only" $80 to 125 billion in damage.

"Right now, the solar cycle is in a valley--the deepest of the past century. In 2008 and 2009, the sun set Space Age records for low sunspot counts, weak solar wind, and low solar irradiance. The sun has gone more than two years without a significant solar flare. In our professional careers, we've never seen anything quite like it," says Dean Pesnell of the Goddard Space Flight Center, NASA's lead representative on the panel. "Solar minimum has lasted far beyond the date we predicted in 2007."

"Meanwhile, the sun pays little heed to human committees. There could be more surprises, panelists acknowledge, and more revisions to the forecast."

"Go ahead and mark your calendar for May 2013," says Pesnell. "But use a pencil."

via NASA Science News
The full Article can be read or heard HERE.

More on a Flare of a Spotless Sun

Solar Flare, CME and Tsunami Generated by a “Blank Sun”

Posted: 27 Apr 2008 10:20 PM CDT

Even during solar minimum, the Sun can be surprisingly dynamic. We are currently observing a sunspot-less solar disk, but on Saturday the Solar and Heliospheric Observatory (SOHO) observed a noteworthy X-ray flare. It was a B3.8 flare, producing a coronal mass ejection (CME), sending vast quantities of hot plasma into interplanetary space. Admittedly, it is [...] Astroengine

http://www.astroengine.net/?p=207

Quiet Sun, Flares

With the Sun continuing a its unusually prolonged Minimum, solar physicists continue to await the advent of Solar Cycle 24, which seemed to sputter briefly with the properly polarized sun spots in February, then quieted down again, only to see a small parade of Cycle 23 spots traverse the Sun's disk in recent weeks.

A "small" solar flare was reported by SpaceWeather.com today, with an attendant Coronal Mass Ejection, qualifying for a genuine SPE, or Solar Partical Event that may effect the geomagnetic field and offer a display of aurora phenomena over the next 24 to 72 hours.

STRANGE SOLAR FLARE: No sunspots? No problem. Yesterday the blank sun unleashed a solar flare without the usual aid of a sunspot. At 1408 UT on April 26th, Earth-orbiting satellites detected a surge of X-rays registering B3.8 on the "Richter scale" of solar flares. That's a relatively minor flare; nevertheless, the blast sent a "solar tsunami" shock wave rippling through the sun's atmosphere and also launched a coronal mass ejection. The CME is expected to reach Earth late on April 28th or April 29th, possibly sparking high latitude auroras when it arrives. Visit http://spaceweather.com to view images, movies and updates.