martes, 16 de junio de 2009
Are We Ready to Live on Other Planets?
The International Space Station has a beefed up crew that has gone from three to six astronauts, now that the construction of the $100 billion space laboratory is nearly complete. We are told that the station crew will be able to spend more time doing medical and biological experiments in the station's microgravity environment to prepare humans for journeys to the moon and Mars.
We are “learning to live in space” is the shorthand justification for why we have a space station. But are the right questions behind the ISS experiments being asked? Exactly how salient is the research on the ISS when applied to human interplanetary travel?
Let me draw a parallel to something that’s not too far from where I live in Maryland; the Chesapeake and Ohio Canal that follows the Potomac River. Construction of the canal started in the early 1800s as part of a post Revolutionary War vision by Thomas Jefferson to connect the eastern seaboard to the Great Lakes and Ohio River. Passengers rode on mule drawn barges for several days to go from Washington D.C. northwest to Cumberland, Maryland, 185 miles away. It was not long before the much speedier steam locomotive antiquated this form of human transportation. The canal was abandoned before it ever reached the Ohio River.
When we look at the long term future of manned interplanetary travel, astronauts will not live in weightlessness for extended periods, any more that travelers today expect to spend several days on a mule draw barge to go the distance a jetliner covers is less than 30 minutes.
Let’s face it, interplanetary travel is deadly. Crews will be in mortal danger from radiation blasted into space by solar flares and coronal mass ejections. Any sort of mechanical breakdown of life support systems en route to Mars could quickly become disastrous. There are also practical matters about the amount of payload mass that needs to be devoted to food and water, and the psychological well-being of a crew cooped up in a rancher house-volume habitat module for many months. So the less time spent in transit, the better, and the more likely the success of the mission.
This is simple rocket science. The propulsion systems for going to Mars will need to be much more mature than they are today. With today’s chemical rockets transit time are six to nine months. But with adequately funded research and development you could have advanced propulsion that cuts travel time down to a matter of weeks.
Among the more visionary ideas: magnetized-beam plasma propulsion where a vehicle is pushed along by a directed energy beam from Earth; a gas core fission reactor ejecting hot hydrogen fuel at a powerful rate; a fusion-reactor rocket that expels a super-heated plasma at high velocities.
My favorite farout propulsion idea comes from the imagination of Arthur C. Clarke who, in his 1975 novel Imperial Earth, described a black hole drive. This is an artificially made black hole which has the mass of a mountain embedded inside an event horizon the size of the head of a pin. Soda straw diameter tubes feed fuel into it. The story’s interplanetary cruise liner can travel from Earth to Saturn in 20 days!
We simply will not make the treacherous journey to Mars until there is alternative rocket propulsion to today’s wimpy “mule-barge” chemical rockets.
What's more, It's not clear what further space station research in "living in weightlessness" will yield. After four decades of American and Russian space travel, we know by now that long-term exposure to weightlessness is not good for the body. It deteriorates the heart, bone density, muscle mass, and the immune system, among many other complications. Minor effects include puffiness in the face, flatulence, weight loss, nasal congestion and sleep disturbance. This is a “ perfect storm” of trouble for people cooped up in a space capsule for months.
What we don’t know at all is what the effects of long term living in the gravitational field of the moon and Mars will do to the body. And, future explorers will spend much more time living in 1/6th (moon) or 1/3rd (Mars) gravity, than in weightless space.
The ISS was supposed to have a centrifuge for replicating the gravitational pull of other worlds and trying it out on animal specimens. The module was built by the Japanese government and named the Centrifuge Accommodation Module. But the lab was never launched because of ISS cost overruns and ISS assemble schedule problems. The $700 million lab is now the world’s most expensive museum piece, put on display in an outdoor exhibit at the Tsukuba Space Center in Japan. (The only saving thought is that we don’t have to go through the charade of watching NASA name the module in a contest. How would Whirlpool have worked? Both for the natural phenomenon and the manufacturer of spinning washing machines and clothes dryers.)
In hindsight, the way for NASA to do this kind of critical research would have been to build the complete space station as a spinning wheel that would create artificial gravity through centrifugal force. The idea is over 100 years old, as first described by the great Russian theoretician Konstantin Tsiolkovsky. It was epitomized in the landmark science fiction film 2001 A Space Odyssey, were a majestic space station cartwheels along to the tune of Johann Strauss’ Blue Danube waltz
Such a station could be rotated at a rate to create a 1/6 pull of gravity on one of those ISS “expedition” missions to replicate the lunar environment. Then the crews could swap out and the space wheel spun up to recreate Mars’ 1/3rd gravity for another expedition team. For expeditions doing non-biological experiments, the space wheel could have been spun up further to create Earth’s pull, and the crew could live and work normally. No need for one of those suction potty chairs.
Such an elaborate facility might not have necessarily been beyond the NASA budget, especially if it were fabricated out of inflatable structures (as envisioned by rocket pioneer Werner Von Braun half a century ago). But the space base we've paid for doesn’t tell us the consequences of living on the moon or Mars for any length of time. Does body degradation decrease proportionally with increasing gravity, or is it more complicated that that?
It’s always possible that I’m being premature until we see what science papers are published in research journals from the ISS experiments. But the bottom line it that humans were not made to live in zero-g any more that we’d expect them to grow gills by living in underwater habitats.
What's more, there's no hurry to get to Mars. It's not like the 1848 California Gold Rush (which, by the way, pushed transportation infrastructure). So, let's not do it until it can be done robustly.
image credit: MGM