What must happen before manned trips to other planets are possible?
Can we visit another planet? Yes. But Mars is our best option, and we need at least another couple decades to prepare.
Photo Credit: Brandon Alms
The last time anyone from Earth stepped foot on another natural astronomical body was the last manned moon mission in the early 1970s. That's a long time ago. In the interim, we've built a succession of space stations, from the Russian Mir to the U.S. Spacelab to the current International Space Station, from which astronauts regularly embark and disembark. Innumerable satellites have been launched, and shuttle missions became so common that they weren't even newsworthy (at least until Columbia broke up over Texas on Feb. 1, 2003, and the shuttle fleet was grounded for more than two years thereafter). We've launched probes that have reached the edges of our solar system and will go far, far deeper into space.
So the question that space-minded members of the public often ponder is, "Why haven't humans gone further than the moon, and why haven't they done so by now?"
One answer is, plain and simple: Cost.
Launching any space mission is expensive, but launching a mission to a planet even as relatively close as Mars is a huge undertaking. Even in times of plenty, the thought of putting so much money into something with no immediate tangible benefits (such as a profit or the promise of new breakthroughs on Earth) is a tough sell. In 1991, a report was commissioned to look at President George H. W. Bush's 1989 plan to establish a permanent moon base and launch a human mission to Mars, and the response of some to that report was that the effort could cost as much as $500 billion even back then.
So, part of the challenge is getting buy-in from the public, and perhaps brokering financial and technical partnerships among many nations to work together on manned missions to other planets. Numerous corporate-government alliances may also need to occur for sufficient monetary backing to come about.
There are also any number of technical and safety considerations. The United States managed to launch two robotic vehicles to explore the surface of Mars recently, but one of those vehicles experienced a number of problems. A similar European mission ended with a complete loss of contact with their vehicle, the Beagle-2, presumably because of a crash landing. Sending people is a much more delicate affair, since there would be actual lives at stake.
Some have argued that people could be on Mars by 2010, give or take, if we simply had the will to commit our time and money. But most experts don't feel comfortable with another manned lunar mission before 2015 (more likely 2020), and the assumption is that a manned Mars mission would take place in 2030 at the earliest. It will be 2014 or so, most likely, before even an unmanned craft visits Mars to bring Martian material back to Earth.
It's a long trip, too, and that brings a number of concerns. With currently known technology, a trip to Mars (283 million miles away), would take 18 to 24 months. And that's the closest planet that we have any hope of stepping onto without immediate death. Venus has a corrosive atmosphere that would do in any spacesuit, and Mercury is way too close to the Sun. Beyond Mars, many of the planets are not only unbelievably distant in terms of miles and travel time for humans, but they are also not likely to be sites we can land on, since many of those planets are mostly gaseous and might not even have a solid surface to land on (or, if there is, it is so far down that atmospheric pressure would crack a human like an egg).
A manned vessel to Mars or any other celestial body farther out than the Moon needs to be sturdy enough to survive the trip and well-stocked enough to keep a crew alive for several years worth of travel. Also, no one really knows what the stress of such a journey will mean for travelers, which is why Russian researchers and others wish to simulate the long journey with people on Earth who would volunteer to enter into a simulated vessel on this planet and remain there for the equivalent duration of a Mars flight. This still won't be perfect, as zero gravity conditions in space will have their own effects, many of them negative, on human anatomy over a prolonged period. As yet, there is no practical way to create a vessel that would simulate normal-gravity conditions, though there might be by the time 2020 or 2030 rolls around.
So, a trip to Mars is still some time off. And a human-crewed trip to any other planet is virtually unthinkable for any time in the foreseeable future. The possibilities are tantalizing, but the fact is that much remains to be done before out feet disturb any ground other than our lunar neighbor's.