and the higher the odds of a catastrophic collision with a meteoroid This is silly. The dangers to a mission from a meteroid are essentially the same for a six

and the higher the odds of a catastrophic collision with a meteoroid This is silly. The dangers to a mission from a meteroid are essentially the same for a six-month mission as a six-day mission: nil when compared the to the risk of blowing up on the launchpad. Chang-Diaz is developing an advanced plasma propulsion system that would cut the round-trip time on Mars missions to five months Ugh. We can already get to Mars in six months using chemical rocket engines right off the shelf. If Chang-Diaz thinks people can accept nuclear reactors in space, then we should just pull out the Nuclear Thermal Rockets we've already built and use them instead. EDIT: I now see he is saying roundtrip being 5 months. This doesn't violate the laws of physics, but it does require nuclear reactors in space with massive energy-to-mass ratios, well beyond anything we've built for anything on the ground or in space before. Spacecraft propelling astronauts to Mars — and habitats on its surface — must be equipped with shielding sufficient to block space radiation. Or you can just take your dose. The cosmic ray dose from a round-trip Mars mission would increase your chance of cancer over your lifetime from about 20% to about 21%. This isn't something you would want to expose the general public (or even the janitor in a nuclear power plant) to, but it's petty when talking about the risks to crew safety from the Mars mission. Launching a extra spare habitat or earth-return-vehicle to Mars will be a better bang-for-the-buck in terms of decreasing mission risk, with the bonus that we need to do it anyway. (This is different from blocking solar flares. Those can and probably will kill the crew dead if they aren't shielded from those. But that shielding is more straightforward as the article says.)