Safety Concerns
Safety becomes a major issue in regards to the advantages and disadvantages of manned and remote space missions. Both the government agencies and the public regard the deaths or injuries of astronauts or cosmonauts a major failure. Conversely, robotic spaceflights have virtually no risk to humans outside of ground accidents. In total, five percent of all people who have attempted to fly into space have died. As of 2010, the total was 22, including three aboard Apollo 1, one aboard Soyuz 1, one on the X-15-3 experimental craft, three aboard Soyuz 11 and seven on the Challenger and Columbia space shuttles respectively. In all, NASA has lost the most astronauts. This number does not include those in the midst of training or ground crew killed during preparation.
In response, both NASA and the Russian Space Agency have constructed memorials for those who have died while attempting spaceflight. In the John F. Kennedy Space Center, the Space Mirror Memorial holds the names of those killed in spacecraft. Russia has its fatal cosmonaut mission participants buried at the Kremlin Wall Necropolis in Moscow.
Health Risks
Manned spaceflight opens up major risks to humans in regards to basic health risks as well. When astronauts or cosmonauts fly into space, they can experience a number of illnesses including immune deficiency, collapse of bone and muscle tissue, decompression sickness and radiation poisoning. In order to combat these problems, the National Space and Biomedical Research Institute conducts experiments on a regular basis with spaceflights to combat this. Robotic spaceflights have no issues in regards to health. Since there are no humans present, very little affects the spacecraft. Robots are able to achieve their missions with almost no threat to human life.
Time Frame
The time frame of space missions drastically impacts the advantages and disadvantages of manned and remote space missions. Human crews are required to train for months to years in order to pilot spacecraft. Robotic spacecraft, on the other hand, are built to conduct their mission immediately. However, there is a disadvantage to construction because of the fact that it takes years to build an unmanned craft.
In addition, there are limitations to what manned space flight can accomplish in regards to the time it takes to get to destinations. Humans are limited on lifespan, which causes the timespan of a flight to become an important factor. Meanwhile, robotic spacecraft have no such factors impacting their lifespan. This becomes highly important since no medical emergencies can be handled from the ground crew short of advice to the astronauts.
Costs
The overall cost of human spaceflight versus robotic missions is a significant factor in the decision to continue missions. According to NASA, each space shuttle mission costs $420 million on average, but increased drastically after the Columbia disaster. These missions generally only last one to two weeks. This is much higher than robotic missions, which can be conducted for much less considering the tasks can take place over the course of years. For example, the Cassini-Huygens and Voyager missions have lasted years.
References
"Manned vs. Unmanned Space Exploration" Physorg: http://www.physorg.com/news8442.html
"20 Years Later: Hubble, Humans and the Future of Space Flight" The Atlantic: http://www.theatlantic.com/science/archive/2010/04/20-years-later-hubble-humans-and-the-future-of-space-flight/39212/
Image Source
Skylab. (Supplied by NASA; Public Domain; http://upload.wikimedia.org/wikipedia/en/0/07/Skylab_%28SL-4%29.jpg)
Manned Missions: Advantages and Disadvantages
