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Fly to Tokyo, Get Two Chest X-rays:
The Effects of Space Weather on Aviation
presented by science@nasa
The next time you step onto an airplane,
consider the following:
In any given year,
the pilot of your aircraft probably absorbs
as much radiation as a worker in a nuclear power plant.
And you are about to follow him wherever he goes.
The FAA classifies pilots as 'occupational radiation workers.'
Flying high above Earth with little atmosphere to protect them,
they can absorb significant doses of cosmic rays
and solar radiation.
During a typical polar flight from Chicago to Beijing, for instance,
a pilot is exposed to the equivalent of two chest x-rays.
Multiplied over the course of a career,
this can cause problems such as increased risk of cancer
and possibly cataracts.
Passengers have reason to be concerned, too.
'A 100,000 mile frequent flyer gets about 20 chest x-rays,'
points out Chris Mertens,
a senior research scientist at NASA Langley Research Center.
'This is true regardless of the latitude of the flights.'
It's worth noting that even people on the ground absorb some radiation.
Cosmic rays and their by-products are so powerful,
they can reach all the way down to Earth's surface,
giving a person at sea level the equivalent of one chest x-ray
every 10 days or so.
On a plane, however,
dose rates increase 10-fold or more.
The exposure depends on factors
ranging from the altitude and latitude of the flight path
(polar routes are irradiated most)
to sunspot counts and solar activity
(a powerful solar storm can boost radiation levels a hundredfold).
To help airline companies safeguard passengers and personnel,
NASA is developing an experimental tool
to predict exposures in real time.
Mertens is the PI of the system,
called NAIRAS--
short for 'Nowcast of Atmosphere Ionizing Radiation for Aviation Safety.'
Mertens notes that the number of flights over the poles
has skyrocketed in recent years.
Airlines prefer polar routes for international travel
because they are shorter and have reduced head winds,
creating fuel savings of tens of thousands of dollars per flight.
However, Earth's poles
are where the radiation problem can be most severe.
Our planet's magnetic field funnels cosmic rays
and solar energetic particles
over the very same latitudes where airlines want to fly.
On a typical day when the sun is quiet,
dose rates for international flights over the poles
are 3 to 5 times higher than domestic flights
closer to the equator.
If a flight controller wants to know the situation around the poles right now,
NAIRAS can help.
It is, essentially,
an online global map of radiation dose rates
for different flight paths and altitudes.
Maps are produced in near real-time by a computer at Langley,
which combines cutting-edge physics codes
with realtime measurements of solar activity
and cosmic rays.
'We are still in an experimental phase,' he says.
'The ultimate goal of the NAIRAS effort
is to adopt a paradigm similar to terrestrial weather forecasting.'
The value to the airlines is clear.
The ability to fly over the poles can save $35,000 to $40,000
per flight in fuel costs alone.
On the other hand,
altering course to avoid a polar radiation storm
can cost as much as $100,000.
A forecasting tool like NAIRAS
can help the airlines make the right decision.
Of even greater importance to Mertens
is the human factor.
Martens says,
'Back in 2004, I went to a workshop on space weather and aviation.
A pilot stood up to address the audience:
'Look,' he said,
'we are classified as radiation workers,
we are more exposed than any other group,
yet we know the least of all the groups.'
That was a turning point for me.
I wanted to do something
to help pilots better understand what they are flying into.'
And so NAIRAS was born.
Mertens and colleagues are about to publish a paper
in the journal Space Weather
comparing NAIRAS predictions
to actual radiation measurements onboard airplanes.
'The results are encouraging,' he says,
'but we still have work to do.'
For updates from the skies above-
and beyond-
stay tuned to science.nasa.gov