Question: how close would you be to the sun, in order to get visibly burnt/injured in a rocket?

Kirsty Ross answered on 21 Jun 2012:

If you were travelling towards the sun, you would have to be in a spaceship to be protected from the vacuum and cold of space. Breathing and keeping warm would be an issue otherwise! I wouldn’t necessarily be worried about the UVA/UVB radiation coming from the sun that causes your skin to burn. More than enough would be blocked by the windows and walls of the spaceship.

Once you get away from the earth’s protective magnetic field, you are exposed directly to the solar wind. This wind consists of high energy particles from the sun. We see them on earth as they are directly down through the atmosphere by the earth’s magnetic field. They are the northern and southern lights. There isn’t really a safe distance from the sun to avoid the solar wind. The closer you get the stronger it would be. Solar flares can sometimes send enough energy towards the earth to knock out satellites in orbit. If you were travelling towards the sun, you’d have to take shelter in a well shielded area for a few days, as they can make you very sick. Fortunately they move slower than light, so you’d have a day or two’s notice if you were near earth. Closer to the sun would give you less warning time and they would be a lot stronger.

When the Sun flares, it produces x-rays, gamma-rays, and energetic particles. The energetic particles are the worst, but they are delayed compared to the X-rays and gamma-rays, so you have some warning that they are coming. If you were travelling towards the sun, you would have time to hide in a ‘storm shelter’, a well-shielded area that you can live in for a few days until the particles die down. A good place for a storm shelter would be in the center of the ship, surrounded by the water tanks. If you don’t have a storm shelter (e.g. if you are out moonwalking in just your suit) a bad solar flare can kill you by radiation sickness.

The hard radiation (particles and x/gamma rays) from the non-flaring Sun is small compared to the galactic cosmic ray exposure. These particles come from deep space more or less continuously. Small amounts of shielding can cut out the majority of this, but the remainder will give you a somewhat increased risk of cancer. Using very conservative rules of thumb, a week in space’s cosmic ray environment will shorten your life expectancy by about a day (statistically–it is very unlikely to give you cancer, but if it does, it will shorten your life by more than a day). Since space is inherently dangerous at the present state of the art, cancer due to cosmic rays is relatively small additional risk.