Free Form Post 2: The Dangers of Space Radiation

Science fiction authors have long dreamed of sending humans into the far reaches of the galaxy to explore alien planets and establish interstellar empires. While this dream might seem unattainable and foolish,  renowned physicist Stephen Hawking, and many like him, believe that "Space could prevent the disappearance of humanity by the colonization of other planets". By living exclusively on Earth, humans have put all their eggs in one basket. With so many threats to human existence, from rogue asteroids, climate change, nuclear war, and the unknown (alien invasion?), colonizing other planets would diversify humanity's settlements and increase its chance of survival. 

However, colonizing other planets is an immense challenge that will require coordination, resources, and new technology to overcome the various logistical challenges involved in moving humans and machines over vast distances through space. Among problems such as reducing the massive cost and inefficiency, producing food supplies, and establishing a suitable habitat at the destination, is the challenge of surviving the dangerous journey without a significantly increased risk for cancer caused by the massive amounts of radiation present in Space.

Radiation is moving energy in the form of high-speed particles and electromagnetic waves. We are subjected to this radiation daily just by living on Earth in the form of visible light, radio waves, microwaves, and UV light from the Sun. Radiation is divided into two categories with different levels of harmfulness - ionizing radiation and non-ionizing radiation.

• Ionizing radiation is powerful enough to remove electrons from the orbits of atoms, producing highly unstable ions. This radiation is harmful to humans because it affects our DNA and is the type of radiation that scientists are worried about protecting us from. Examples of ionizing radiation include gamma rays, x-rays, and cosmic rays.

• Non-Ionizing radiation does not have enough energy to remove electrons from the orbits of atoms. This is because longer wavelength, shorter frequency waves have less energy than high frequency, short wavelength waves. It is not harmful to humans like ionizing radiation is. Examples include: visible light and radio waves.

Though we are constantly exposed to "dangerous" radiation on Earth, this exposure is in such small quantities that isn't immediately lethal to humans and allows us to comfortably survive. The reason why this exposure is so negligible is that the Earth itself shields us from this radiation with its magnetic field and atmosphere. As the Earth, with its molten iron core, rotates, it creates a magnetic field around the Earth. This magnetic field deflects harmful radiation particles away from the Earth, blocking around 99% of harmful radiation. The atmosphere acts as an additional barrier and stops some of the remaining radiation.


However, astronauts and potential space colonists will have to venture out of the protective radiation shelter that is the Earth and face the dangerously high levels of radiation that exist in Space. Each day we each receive about 10 microsieverts of radiation on Earth. A round-trip to just Mars would expose an astronaut to 0.66 sieverts of radiation, not to mention the radiation that would be absorbed by staying on Mars for a sustained period of time. Exposure to 1 sievert of radiation increases the risk of cancer by 5.5 percent. Clearly, any sustained manned mission, especially one intended to colonize,  would, at least at current speeds and protection levels, doom its crew to an early demise.

There are two ways to solve this problem. The first is to increase the speed of the voyage. By increasing the speed of the voyage, astronauts would be exposed to less radiation. Unless of course I'm completely wrong and they would actually be exposed to the same amount of radiation but just in a shorter period of time (like running the gauntlet faster). The problem with this method is that scientists and engineers haven't feasibly developed the technology to travel at faster speeds than those feasible with rockets. They have proposed alternative propulsion systems such as solar sails but these have not been tested. The second method to decrease exposure to radiation is to increase shielding on board the ship. Of course, the problem with this is that shielding needs to be incredibly dense and therefore heavy. A properly shielded interstellar spaceship would probably not be able to take off from the Earth. Perhaps if it were assembled in high Earth orbit, this problem could be avoided.

Until scientists can figure out a way to overcome the dangers posed by radiation in space, human space colonization may remain simply a dream.