By Roland Piquepaille
Last year, the United States decided to send humans on Mars within thirty years. This sounds possible to me, but in this article, The Scientist warns that besides technical barriers, NASA will need to work to avoid biomedical risks to the human crews. First, crew members will have to live together for almost three years in a small spacecraft, and this promiscuity can lead to possible conflicts or depressions. Bone and muscle losses are another serious issue for such a long mission. Finally, the crew will be exposed to cosmic radiation and will need to be protected from such damages as the destruction of their brain cells. Fortunately, the author thinks that there are solutions to these three problems and offers us his vision. Read more...Let's briefly look at the psychological factors. Jay Buckey Jr., the author, who flew aboard the Space Shuttle Columbia in 1998, thinks that conflicts between crew members can be avoided either by sending large crews or big spacecrafts. But he also notes that human are pretty adaptable, especially when faced with tough conditions. He gives a couple of examples.
Fridtjof Nansen spent nine months above the Arctic Circle in a two-person hut with colleague Hjalmar Johansen. Nansen returned and later received the Nobel Prize for other work. He not only survived, he flourished. The crew on Sir Ernest Shackleton's unsuccessful trip across Antarctica survived two years lost in the Antarctic ice.
So even if a three-year mission could be difficult, it's still possible to be a successful one with proper training and crew selection.
NASA will have to face the even more serious issue of bone loss.
Crew members in space can lose approximately 1.5% of bone mass per month in certain load-bearing areas such as the hip. This loss occurs despite an aggressive, exercise-based countermeasure program.
According to Buckey, this problem can be solved by using two approaches. The first one implies more effective exercise and use of drugs. The second one would be to build a spaceship with an artificial gravity. Of course, NASA would have to test a series of inhabited rotating spacecrafts before.
The biggest health problem for a human crew going to Mars is the exposure to cosmic radiation, and mainly because it's invisible and almost impossible to quantify. Here is a description of the problem.
Galactic cosmic radiation consists of atomic nuclei traveling at high speed with high energy. Earth's magnetic field and atmosphere deflect or block most of it terrestrially, but a spacecraft in interplanetary space would not have this protection. Modeling studies have shown that with typical shielding, ions with an atomic number (z) ¡Ý 15 would hit approximately 6%-12% of the entire population of neuronal nuclei (depending on size and location) in the brain. Hits would occur outside of the nucleus as well. Many of these strikes are likely to be lethal to the cells.
So what's the solution to this problem? The answer is to build a shield around the spaceship.
Again, there are two solutions. A passive shield, made of lead for instance, would have to be very thick to successfully protect the crew, and the weight of such a protected spacecraft would probably be too high to send it in space anyway.
But there is another solution: active shielding.
Just as a magnetic field protects Earth, it might be possible to put a magnetic field around a spacecraft. A coil of a superconducting material could produce a substantial magnetic field, which could, in turn, deflect the energetic galactic cosmic radiation. For a small-coil radius, the magnetic field would have to be quite strong (several Tesla) to be effective. A field of this size presents major structural and safety issues.
The larger the coil, however, the weaker the magnetic field needs to be. A wire wrapped on a spool could be unwound in space into a large coil. As the radius of the coil approaches a kilometer or so, the field strength and current that is needed will drop to reasonable levels. This approach to shielding, called active shielding, potentially could keep radiation levels within the spacecraft at any desired level.
In his conclusion, Buckey says that Mars is an achievable goal, and delivers his vision.
We solve most of the physiologic problems such as bone loss through biomedical research; address the psychological stresses with proper training and selection; and devote our engineering efforts to making an active radiation shield.
Even if technical or medical hurdles remain, wouldn't you be happy to go to Mars?
Source: Jay C. Buckey, for The Scientist, Volume 19, Issue 6, 20, March 28, 2005
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