The Dangers of Traveling near the Speed of Light
Image for a moment that you are in a spaceship traveling at 10% of the speed of light. All of a sudden your spaceship hits a single molecule of floating hydrogen gas (only two atoms of hydrogen). Traveling at those speeds, these two lonely hydrogen atoms essentially become high intensity radiation that will penetrate through your spaceship, destroy all electronic equipment that they touch, and kill any living thing that is unfortunately in their way.
Space is not completely void of all matter. There are plenty of atom gases (mostly hydrogen gas) and micro-meteorites that are not detectable or avoidable in space travel; and when traveling at super high speeds approaching the speed of light, impact with these floating atoms will be common... perhaps every few seconds of space travel depending on your location in space.
The only way to protect a spaceship and crew from this deadly radiation is through shields.. a heck of a lot of shielding. In my opinion, spaceships would need to have massive hulls that must absorb 100% percent of all radiation and still not significantly break down over time, since space travel can take hundreds and maybe thousands of years even when traveling near the speed of light.
So, my solution is to use entire asteroids as shields, preferably using heavy, mostly rocky, or metal-based asteroids. Maybe these spaceships would be inside or are the asteroids themselves. Therefore, the surface of these asteroids could literally heat up to molten rock while the occupants in the spaceship are safe behind several thousand tons of heavy rocks and metal.
Of course for a spaceship to be able to continuously move an asteroid along with itself at speeds near the speed of light would require an enormous amount of energy; but I assume that if mankind has enough energy to move a spaceship at those speeds, then they can also move an asteroid too.
by Phil for Humanity