Cidersomerset
31st May 2013, 13:02
I wondered if the 'Secret Space programme' were ready for ordinary mars settlers..LOL..
http://static.bbci.co.uk/frameworks/barlesque/2.45.9/desktop/3.5/img/blq-blocks_grey_alpha.png
30 May 2013 Last updated at 20:26
Science correspondent Article written by Jonathan Amos
More from JonathanFollow Jonathan on TwitterRover radiation data poses manned Mars
mission dilemmaComments (325) Art work of humans on the surface of Mars
http://news.bbcimg.co.uk/media/images/67890000/jpg/_67890484_s6100151-astronauts_on_mars,_computer_artwork-spl.jpg
A single mission to Mars is going to take the astronauts close to or beyond their current
career limits for radiation exposure. Scientists say getting to Mars as quickly as possible
would lower the risks Nasa's Curiosity rover has confirmed what everyone has long
suspected - that astronauts on a Mars mission would get a big dose of damaging
radiation.The robot counted the number of high-energy space particles striking it on its
eight-month journey to the planet.Based on this data, scientists say a human travelling
to and from Mars could well be exposed to a radiation dose that breached current safety
limits.This calculation does not even include time spent on the planet's surface.
When the time devoted to exploring the world is taken into account, the dose rises
further still.This would increase the chances of developing a fatal cancer beyond what is
presently deemed acceptable for a career astronaut.
Cary Zeitlin from the Southwest Research Institute in Boulder, Colorado, and colleagues
report the Curiosity findings in the latest edition of Science magazine.They say
engineers will have to give careful consideration to the type of shielding that is built into
a Mars-bound crew ship. However, they concede that for some of the most damaging
radiation particles, there may be little that can be done to shelter the crew other than to
get them to Mars and the partial protection of its thin atmosphere and rocky mass as
quickly as possible.At the moment, given existing chemical propulsion technology, Mars
transits take months.
"The situation would be greatly improved if we could only get there quite a bit faster,"
Dr Zeitlin told BBC News.
"It is not just the dose rate that is the problem; it is the number of days that one
accumulates that dose that drives the total towards or beyond the career limits.
Improved propulsion would really be the ticket if someone could make that work."
New types of propulsion, such as plasma and nuclear thermal rockets, are in
development. These could bring the journey time down to a number of weeks.
Curiosity travelled to Mars inside a capsule similar in size to the one now being
developed to take astronauts beyond the space station to destinations such as asteroids
and even Mars.
http://news.bbcimg.co.uk/media/images/67890000/gif/_67890485_mars_1_nasa.gif
Aeroshell separates from cruise stage The rover travelled to Mars tucked inside a
protective capsule. Its RAD instrument was turned on for most of the journey
For most of its 253-day, 560-million-km journey in 2011/2012, the robot had its
Radiation Assessment Detector (RAD) instrument switched on inside the cruise vessel,
which gave a degree of protection. RAD counts the numbers of energetic particles -
mostly protons - hitting its sensors. The particles of concern fall into two categories -
those that are accelerated away from our dynamic Sun; and those that arrive at high
velocity from outside of the Solar System. This latter category originates from exploded
stars and the environs of black holes.
These galactic cosmic rays (GCRs) impart a lot of energy when they strike the human
body and will damage DNA in cells. They are also the most difficult to shield against.
Earth's thick atmosphere, its magnetic field and its huge rock bulk provide protection to
people living on its surface, but for astronauts in deep space even an aluminium hull 30
cm thick is not going to change their exposure to GCRs very much.The RAD data
revealed an average GCR dose equivalent rate of 1.84 milliSieverts (mSv) per day
during the rover's cruise to Mars. (The Sievert is a standard measure of the biological
impacts of radiation.) This dose rate is about the same as having a full-body CT scan in
a hospital every five days or so.
Number reassessment
Dr Zeitlin and his team used this measurement as a guide to work out what an
astronaut could expect on a Mars mission, assuming he or she had a similarly shielded
spacecraft, travelled at a time when the Sun's activity was broadly the same and
completed the journey in just 180 days - Nasa's "design reference" transit time for a
manned mission to Mars. They calculated the total dose just for the cruise phases to
and from Mars to be 660mSv. The team promises to come back with the additional
number from surface exposure once Curiosity has taken more measurements at its
landing location on the planet's equator.
But even this 660mSv figure represents a large proportion of the 1,000mSv for career
exposure that several space agencies work to keep their astronauts from approaching.
Reaching 1,000mSv is associated with a 5% increase in the risk of developing a fatal
cancer. There would likely be neurological impairment and eyesight damage as well.
Nasa actually works to keep its astronauts below a 3% excess risk.
"If you extrapolate the daily measurements that were made by RAD to a 500-day
mission you would incur exposures that would cause most individuals to exceed that 3%
limit," explained Dr Eddie Semones, the spaceflight radiation health officer at Nasa's
Johnson Space Center, who added that experts were reviewing the restriction.
"Currently, we're looking at that 3% standard and its applicability for exploration-type
missions, and those discussions are going forward on how to handle that and what steps
need to be taken to protect the crew."
All this should be set against the dangers associated with space travel in general, such
as launching on a rocket or trying to land on another planet. It is a dangerous business.
It also needs to be considered in the context of the risks of contracting cancer during
a "normal" lifetime on Earth, which is 26% (for a UK citizen).
Complex calculation
The space agencies have quite deliberately set conservative limits for their astronauts
but it seems clear they would have to relax their rules somewhat or mitigate the risks in
some other way to authorise a Mars mission.However, the scenario for commercial
ventures could be very different. Two initiatives - Inspiration Mars and Mars One - have
been announced recently that propose getting people to Mars in the next 10 years using
existing technologies. Privateer astronauts that participate in these projects may regard
the extra risks associated with radiation to be an acceptable gamble given the
extraordinary prize of walking on the Red Planet.
Dr Kevin Fong is director of the Centre for Space Medicine at University College London,
UK, and has written about the dangers associated with space exploration. He said that
what Dr Zeitlin and colleagues had done was help remove some of the uncertainty in
the risk assessment.
"Radiobiology is actually really tricky because how the body will respond to exposure
will depend on many factors, such as whether you're old or young, male or female," he
told BBC News.
"What's important about this study is that it characterises the deep space radiation
environment for the first time in a vehicle whose shielding is not orders of magnitude
different from that which you would expect to put a human crew inside."
http://news.bbcimg.co.uk/media/images/67890000/jpg/_67890489_rad.jpg
Position of RAD instrument on Mars The RAD instrument continues to gather data on the
surface of Mars
http://www.bbc.co.uk/news/science-environment-22718672
http://static.bbci.co.uk/frameworks/barlesque/2.45.9/desktop/3.5/img/blq-blocks_grey_alpha.png
30 May 2013 Last updated at 20:26
Science correspondent Article written by Jonathan Amos
More from JonathanFollow Jonathan on TwitterRover radiation data poses manned Mars
mission dilemmaComments (325) Art work of humans on the surface of Mars
http://news.bbcimg.co.uk/media/images/67890000/jpg/_67890484_s6100151-astronauts_on_mars,_computer_artwork-spl.jpg
A single mission to Mars is going to take the astronauts close to or beyond their current
career limits for radiation exposure. Scientists say getting to Mars as quickly as possible
would lower the risks Nasa's Curiosity rover has confirmed what everyone has long
suspected - that astronauts on a Mars mission would get a big dose of damaging
radiation.The robot counted the number of high-energy space particles striking it on its
eight-month journey to the planet.Based on this data, scientists say a human travelling
to and from Mars could well be exposed to a radiation dose that breached current safety
limits.This calculation does not even include time spent on the planet's surface.
When the time devoted to exploring the world is taken into account, the dose rises
further still.This would increase the chances of developing a fatal cancer beyond what is
presently deemed acceptable for a career astronaut.
Cary Zeitlin from the Southwest Research Institute in Boulder, Colorado, and colleagues
report the Curiosity findings in the latest edition of Science magazine.They say
engineers will have to give careful consideration to the type of shielding that is built into
a Mars-bound crew ship. However, they concede that for some of the most damaging
radiation particles, there may be little that can be done to shelter the crew other than to
get them to Mars and the partial protection of its thin atmosphere and rocky mass as
quickly as possible.At the moment, given existing chemical propulsion technology, Mars
transits take months.
"The situation would be greatly improved if we could only get there quite a bit faster,"
Dr Zeitlin told BBC News.
"It is not just the dose rate that is the problem; it is the number of days that one
accumulates that dose that drives the total towards or beyond the career limits.
Improved propulsion would really be the ticket if someone could make that work."
New types of propulsion, such as plasma and nuclear thermal rockets, are in
development. These could bring the journey time down to a number of weeks.
Curiosity travelled to Mars inside a capsule similar in size to the one now being
developed to take astronauts beyond the space station to destinations such as asteroids
and even Mars.
http://news.bbcimg.co.uk/media/images/67890000/gif/_67890485_mars_1_nasa.gif
Aeroshell separates from cruise stage The rover travelled to Mars tucked inside a
protective capsule. Its RAD instrument was turned on for most of the journey
For most of its 253-day, 560-million-km journey in 2011/2012, the robot had its
Radiation Assessment Detector (RAD) instrument switched on inside the cruise vessel,
which gave a degree of protection. RAD counts the numbers of energetic particles -
mostly protons - hitting its sensors. The particles of concern fall into two categories -
those that are accelerated away from our dynamic Sun; and those that arrive at high
velocity from outside of the Solar System. This latter category originates from exploded
stars and the environs of black holes.
These galactic cosmic rays (GCRs) impart a lot of energy when they strike the human
body and will damage DNA in cells. They are also the most difficult to shield against.
Earth's thick atmosphere, its magnetic field and its huge rock bulk provide protection to
people living on its surface, but for astronauts in deep space even an aluminium hull 30
cm thick is not going to change their exposure to GCRs very much.The RAD data
revealed an average GCR dose equivalent rate of 1.84 milliSieverts (mSv) per day
during the rover's cruise to Mars. (The Sievert is a standard measure of the biological
impacts of radiation.) This dose rate is about the same as having a full-body CT scan in
a hospital every five days or so.
Number reassessment
Dr Zeitlin and his team used this measurement as a guide to work out what an
astronaut could expect on a Mars mission, assuming he or she had a similarly shielded
spacecraft, travelled at a time when the Sun's activity was broadly the same and
completed the journey in just 180 days - Nasa's "design reference" transit time for a
manned mission to Mars. They calculated the total dose just for the cruise phases to
and from Mars to be 660mSv. The team promises to come back with the additional
number from surface exposure once Curiosity has taken more measurements at its
landing location on the planet's equator.
But even this 660mSv figure represents a large proportion of the 1,000mSv for career
exposure that several space agencies work to keep their astronauts from approaching.
Reaching 1,000mSv is associated with a 5% increase in the risk of developing a fatal
cancer. There would likely be neurological impairment and eyesight damage as well.
Nasa actually works to keep its astronauts below a 3% excess risk.
"If you extrapolate the daily measurements that were made by RAD to a 500-day
mission you would incur exposures that would cause most individuals to exceed that 3%
limit," explained Dr Eddie Semones, the spaceflight radiation health officer at Nasa's
Johnson Space Center, who added that experts were reviewing the restriction.
"Currently, we're looking at that 3% standard and its applicability for exploration-type
missions, and those discussions are going forward on how to handle that and what steps
need to be taken to protect the crew."
All this should be set against the dangers associated with space travel in general, such
as launching on a rocket or trying to land on another planet. It is a dangerous business.
It also needs to be considered in the context of the risks of contracting cancer during
a "normal" lifetime on Earth, which is 26% (for a UK citizen).
Complex calculation
The space agencies have quite deliberately set conservative limits for their astronauts
but it seems clear they would have to relax their rules somewhat or mitigate the risks in
some other way to authorise a Mars mission.However, the scenario for commercial
ventures could be very different. Two initiatives - Inspiration Mars and Mars One - have
been announced recently that propose getting people to Mars in the next 10 years using
existing technologies. Privateer astronauts that participate in these projects may regard
the extra risks associated with radiation to be an acceptable gamble given the
extraordinary prize of walking on the Red Planet.
Dr Kevin Fong is director of the Centre for Space Medicine at University College London,
UK, and has written about the dangers associated with space exploration. He said that
what Dr Zeitlin and colleagues had done was help remove some of the uncertainty in
the risk assessment.
"Radiobiology is actually really tricky because how the body will respond to exposure
will depend on many factors, such as whether you're old or young, male or female," he
told BBC News.
"What's important about this study is that it characterises the deep space radiation
environment for the first time in a vehicle whose shielding is not orders of magnitude
different from that which you would expect to put a human crew inside."
http://news.bbcimg.co.uk/media/images/67890000/jpg/_67890489_rad.jpg
Position of RAD instrument on Mars The RAD instrument continues to gather data on the
surface of Mars
http://www.bbc.co.uk/news/science-environment-22718672