Discover magazine jumps on the Galactic Cosmic Ray Chicken Little Bandwagon: Are We Trapped On Earth?. This follows the recent Scientific American article, which had a similar attitude: Shielding Space Travelers: The perils of cosmic rays pose severe, perhaps insurmountable, hurdles to human spaceflight to Mars and beyond .

Poppycock!

Radiation, neither galactic cosmic rays (GCR) nor solar flares, comes even remotely close to being a show-stopper for human exploration and settlement. Practical shielding solutions are abundant with just a modicum of vehicle and habitat design imagination.

Unless I see someone else do a good job at it, I will eventually write a longer article on this subject. For now I'll just make a few points that I think are important:

* Spaceship Earth is NOT A METAPHOR! We are proof that you can travel in space and survive. There is absolutely nothing magical about the earth's atmosphere or its magnetic field (which has little effect on GCR anyway). If you reproduce the mass per area above you with water, metals, lunar dirt, etc, then you will be just as protected elsewhere in space as you are here.

* If you hear or read someone spouting off about the dosages that space travelers will receive and they don't specify under what level of shielding they are assuming for those travelers, then everything they say is completely and utterly worthless. When describing the dangers to someone crossing the Atlantic, it is important to say whether the person is riding in a cruise ship, a rowboat or is swimming. Similarly, dosages during space travel depend on what is surrounding them. During a space trip it is crucial to know whether the the occupants are in, for example, a plain ol ' Apollo type capsule or are riding in an advanced designed vehicle with, for example, water and fuel tanks surrounding some or all of their living quarters.

* The SciAm article does give some useful tidbits such as the rule of thumb that 5 meters of water will protect you from GCR to the same degree as living at an altitude of 5500 meters. (BTW: If you are protected from the very high energy GCR, then you will be automatically protected from the lower energy but far more intense solar flare radiation.) Solid materials will allow for considerably thinner shields but since water is needed anyway, it is a good material to use for conceptual designs.

* There are options in between the extremes. The SciAm article first calculates a large cumulative dosage that a traveler on a mission to Mars will receive with limited shielding. Then it examines each of three extreme shielding options: 5 meters of water surrounding the entire spacecraft, only magnetic shielding protecting the whole spacecraft, only electrostatic shielding the whole spacecraft. It finds failings in each these. But, of course, there are a range of practical options in between. For example, shielding just the sleeping quarters with the water tanks would cut the cumulative dosages by at least a third. Improved shielding elsewhere in the living quarters sections of the craft could get the dosage down to half of the extreme case. With these simple assumptions one gets a system that provides a level of radiation risk that the first wave of pioneers to Mars would no doubt gladly take.

* As Mike Griffin has advocated, orbiting depots with fuel, water, and other cargo will be essential for space development. Bulk cargo delivery via systems such as Loral's proposed Aquarius launchers can supply such an orbiting facility at relatively low cost. Don't assume as the SciAm article does that a spacecraft must be lifted to orbit all at once with all of its shielding by a single launcher. Water and other shielding materials can be added to a habitat or spacecraft after it has reached orbit.

* Five meters is a lot but it is not out of the question to surround a habitat and at least part of a spacecraft with that amount of water. For example, there have been many designs of space stations using the Shuttle External Tanks. The ET's oxygen and hydrogen tanks are over 8 meters in diameter and 15 and 29 meters long, resp.. Putting tanks that size filled with water around, say, a Bigelow habitat would lower its radiation background to below that on the surface of the earth. People might go to space hotels to enjoy an environment with LESS radiation than they endure from all those nasty natural background sources down here! ;-)

* The cycler type of vehicle that Buzz Aldrin has advocated for Mars travel goes continuously in a solar orbit that is synchronized in such a way that it passes regularly by Earth and Mars. Taxi vehicles would bring people and cargo up and down from the cycler when it neared each planet. Some station keeping fuel would be needed to maintain its orbit but once there it would not need further large scale boosting. So as I've mentioned before, the cycler has the nice feature that its shielding could be built up to high levels, i.e. each taxi could bring additional material that is left with the cycler. (Andrew Turner of Loral has suggested that the Aquarius could provide an excellent low cost way to build up a cycler's mass.) A "cruise spaceship" operation for Mars travelers could eventually be offered by such a cycler with the shielding set to earth levels of radiation exposure.
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Dealing with space radiation is a serious but solvable problem for which we have a number of options. Optimizing shielding designs is clearly something NASA should dedicate substantial resources. However, the ridiculous scare tactics in these pop articles are grossly misleading and over the top. Radiation will not keep humans from going to space.