Science & Technology
The title of the article, penned by Nathan Schwadron of the University of New Hampshire and colleagues from seven other institutions, asks the provocative question, "Does the worsening galactic cosmic ray environment preclude manned deep space exploration?" Using data from a cosmic ray telescope on board NASA's Lunar Reconnaissance Orbiter, they conclude that while increasing fluxes of cosmic rays "are not a show stopper for long duration missions (e.g., to the Moon, an asteroid, or Mars), galactic cosmic radiation remains a significant and worsening factor that limits mission durations." This figure from their paper shows the number of days a 30 year old astronaut can spend in interplanetary space before they reach their career limit in radiation exposure:
According to the plot, in the year 2014, a 30 year old male flying in a spaceship with 10 g/cm2 of aluminum shielding could spend approximately 700 days in deep space before they reach their radiation dose limit. The same astronaut in the early 1990s could have spent 1000 days in space.
What's going on? Cosmic rays are intensifying. Galactic cosmic rays are a mixture of high-energy photons and subatomic particles accelerated to near-light speed by violent events such as supernova explosions. Astronauts are protected from cosmic rays in part by the sun: solar magnetic fields and the solar wind combine to create a porous 'shield' that fends off energetic particles from outside the solar system. The problem is, as the authors note, "The sun and its solar wind are currently exhibiting extremely low densities and magnetic field strengths, representing states that have never been observed during the Space Age. As a result of the remarkably weak solar activity, we have also observed the highest fluxes of cosmic rays in the Space Age."
The shielding action of the sun is strongest during solar maximum and weakest during solar minimum--hence the 11-year rhythm of the mission duration plot. At the moment we are experiencing Solar Max, which should be a good time for astronauts to fly--but it's not a good time. The solar maximum of 2011-2014 is the weakest in a century, allowing unusual numbers of cosmic rays to penetrate the solar system.
This situation could become even worse if, as some researchers suspect, the sun is entering a long-term phase of the solar cycle characterized by relatively weak maxima and deep, extended minima. In such a future, feeble solar magnetic fields would do an extra-poor job keeping cosmic rays at bay, further reducing the number of days astronauts can travel far from Earth.
To learn more about this interesting research, read the complete article in the online edition of Space Weather.
Comment: There are many things we don't know about our universe. Unprecedented changes in our own solar system is something we really need to pay attention to and try to understand.
A fascinating book called Earth Changes and the Human-Cosmic Connection is a good way to become familiar with some of these topics.
Reader Comments
That is because of thier nature. They can penetrate miles of rock with the greatest of ease.
What you need is a magnetic shield to deflect the cosmic rays.
Star Trek stuff.
That Van Allen Belt shield belongs to the Earth and it's magnetic field.
You can't take that with you to Mars, Moon or wherever else you might be going.
The sheer mass of the Earth's inner and outer cores of Iron-Nickel compostion do the generation.
So, what you really need to do is to generate artificial mass aboard a spacecraft.
Then you have to power it. The best we can do now is a mini-reactor.
Then you have to get it up there. And house it in a large spacecraft. Add a bio-unit for life support while you're at it.
Face it, were stuck on this big blue rock.
Robot explorers and probes are our present capabilities limit.
So a area the approx. size of a sheet of A4 paper would be about 5Kg ... how would that take off?
I doubt if the problem has changed but now is a convenient time for NASA et al to suddenly declare that manned space missions are no longer possible
Any trip to Mars or beyond will require shielding. Plain and simple. Any colony on Mars MUST have shielding or it will be a single generation colony.