For obvious reasons spaceflight has been reserved for governments and the very wealthy. And when it comes to governments, the criteria are stringent. They will get thousands of applications per year and quickly weed out most of them. Predominantly you have to already be a government employee to have any chance of being an astronaut so that is a big disqualification for much of the best and brightest in America.

Today, you don't have to be an astronaut to go into space. Now that it is no longer controlled by the government, technologically has become advanced enough for companies and people making their own star trek to feel comfortable - and that means the cost is dropping as well. You can experience weightlessness for $5,000 and people have visited the Soyuz Space Station for $30 million. Two companies expect they will be able to duplicate the Apollo 8 mission and take civilians around the Moon and back for $100 million - less than 25% of what US Space Shuttle missions cost just to go into orbit.

But because space flight has been primarily government employees and competition has been fierce, the medical community has very little data on what diseases or medical conditions might be risky. To help provide some answers, the aerospace medicine group at the University of Texas Medical Branch at Galveston recently studied how average people with common medical problems — high blood pressure, heart disease, diabetes, lung diseases like asthma or emphysema and back and neck injuries, surgeries or disorders — would be able to tolerate the stresses of commercial spaceflight.

Overall, they found that nearly everyone with well-controlled medical conditions who participated in this project tolerated simulated flight without problems. 

"Physiological stresses of flight include increased acceleration forces, or 'G-forces,' during launch and re-entry, as well as the microgravity period," said lead author Dr. Rebecca Blue. "Our goal was to see how average people with common medical problems, who aren't necessarily as fit as a career astronaut, would be able to tolerate these stresses of an anticipated commercial spaceflight."

Some medical conditions are of particular interest within the commercial spaceflight industry, either because of the high rate of occurrence or because of the potential to cause sudden, serious medical events. The researchers studied how people with these common conditions performed when put through centrifuge simulations of spaceflight launch and re-entry.

The centrifuge allows researchers to mimic the acceleration of a rocket launch or of a spacecraft re-entering through the atmosphere. Astronauts regularly use centrifuges to train for their own spaceflights. The acceleration forces expected in a commercial spaceflight profile are tolerable, but can be uncomfortable, for healthy individuals. The researchers wanted to see if they were equally tolerable for individuals with complex medical histories or whether there were certain conditions that would make it more difficult for them to handle the flight.

"This study further supports the belief that, despite significant chronic medical conditions, the dream of spaceflight is one that most people can achieve," said Blue.