http://institute.nsta.org/web_seminars.asp

NASA/NSTA Web Seminar:

Radiation – Can’t Live With It, Can’t Live Without It

LIVE INTERACTIVE LEARNING @ YOUR DESKTOP

Radiation – Can’t live with it, can’t live without it

Anuradha Koratkar,

Susan Hoban,

Albert Hill, and

Brendan Shaughnessy

Electromagnetic (EM) radiation

• EM radiation is produced by the motion of electrically charged particles.

• EM waves travel through empty space as well as through air and other substances.

Gas in space emits radio waves.

True False We don’t know

Our eyes cover less than one octave of the more than 65 octaves of the electromagnetic spectrum.

This type of emission can come from radioactive materials:

Radio X-rays Gamma-rays

• Electromagnetic radiation travels at the speed of light.

• Electromagnetic radiation acts both as waves or a stream of particles (photons). Low energy photons (such as radio) behave more like waves, while higher energy photons (such as X-rays) behave more like particles.

• The photons with the highest energy correspond to the shortest wavelengths.

The Sun’s Atmosphere

Solar atmosphere consists of:

– The photosphere (5,800K)

– The chromosphere

– The corona (1,000,000K)

We live in the Sun’s Atmosphere

The outer solar atmosphere is a plasma– Gas made of

charged particles – Affected by

magnetic fields– Extends out into

interplanetary space as part of the solar wind.

Solar Max & Solar Min

What is the radiation environment in space?

• Solar electromagnetic radiation • High energy charged particles:

Solar wind and Cosmic rays

What is the Solar Wind?

• Plasma so hot that the Sun's gravity cannot hold it down

• Flows away from the Sun in all directions

• Moves at about 400 km/sec (about 250 miles/sec) and reaches Earth in 4-5 days and in 4 to 5 months reaches Pluto

• Solar proton events have protons with energies exceeding 10 MeV!

Commonplace in the universe.

What are Cosmic rays?

• High energy particles: protons, anti-protons, electrons, positrons and positively charged atomic nuclei.

• Ions of a familiar elements--mostly hydrogen. Ordinary matter, which had undergone some extraordinary process to gain huge energies.

• Low energy cosmic rays are particles accelerated in the shocks of supernova remnants. Ultimate origin of high energy cosmic rays is unknown.

Incoming rate of nearly 1 particle per square meter per second.

Cosmic-ray energy spectrum

Are there more high energy cosmic rays or low energy cosmic rays?

Which of these is affected by radiation?

Equipment Humans

No matter where you live, you receive up

to 360 millirems (4- 5 chest X-rays) per

year, and you have no control over this.

Poll question

The effect of low radiation dosage on humans is:

No negative consequences

Cell damage Radiation induced cancer

What is the effect of radiation on Humans?

• Low radiation dosage – No negative consequences because changes

and repairs in cells, including chromosomes, occur constantly in our bodies.

• Chronic exposure or high radiation dosage– Ionization of atoms, could lead to cell damage,

impact higher-level biological functions – cells operate abnormally or die.

• Critically damage the DNA of cells.

• Radiation-induced cancer is one of the main health risks for manned exploration of the Solar system.

What is the effect of radiation on space equipment?

• Highly energetic particles penetrate electronic components– erroneous commands within the spacecraft – erroneous data from an instrument. – degrade the useful lifetime of internal

components.

• Less energetic particles contribute to a variety of spacecraft surface charging problems.

Radiation protection

Radiation protection

• The energy spectrum of cosmic rays peaks near 1000 MeV per nucleon, and these particles can only be partially blocked by shielding.

• Present shielding approaches are effective only for solar proton events (~10MeV).

• Water is extremely good at shielding.

The CRaTER telescope

Silicon detectors

Tissue equivalent plastic

Window to the deep space

Lunar window

Radiation – Can’t live without it

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If you have any questions let us discuss them on the discussion listserv. Flavio will send everyone a link in case you are not

subscribed to it.

See you at the next session which will be

“Energy and Sustainable Habitat”