Spaceships travelling through space and debris How can a spaceship travel through space if there is space debris flying around at very high speeds?
Wouldn't even a small rock crack through the spaceship?
 A: Yes, that is entirely true. All this "junk" is usually separated in two categories: space debris (man-made), and micro-meteoroids (natural origins). 
Micro-meteoroids
Micro-meteoroids are not as common as you might think. Even when you fly straight through the asteroid belt, micrometeorite impacts will be extremely unlikely. This is because small objects (dust, comet debris, ...) get pushed out of the Solar system by solar radiation pressure, are very likely to fall on a nearby asteroid, be caught in some planet's gravity field (Jupiter, mostly), etc. In short, small celestial bodies (in the order of cm or less) generally have a very short life span on astronomical time scales. 
They can however be a problem near Jupiter for instance, which, because of its large mass, is a gravitational sink for these small objects. Even though they won't live there for very long, there are just so many of them flowing into Jupiter's gravity well all the time that they might just pose a problem. They haven't caused any major problems in exploration missions yet, but nevertheless, the Galileo spacecraft and most others flying to or past Jupiter were equipped with micro-meteoroid impact protection systems around the most critical components.  
Space debris
Space debris is a very active field of study. As it is man-made, it is only a problem of any size for spacecraft near the Earth. The importance of most near-Earth satellites and the threat space debris poses to them is why NORAD keeps track of most space debris in the vicinity of Earth. Information gathered by NORAD is used by space mission designers, so that they can design a spacecraft's trajectory such that it avoids collisions with larger (>~10cm) chunks of space debris. 
Although this prevents most catastrophic collisions, it is very difficult if not impossible to track all the smaller objects (<~10cm). There are unfortunately many millions of such things close to the Eartch, which sometimes indeed leads to impact. Solar panels from the ISS returned to Earth are riddled with holes, dents, scratches, etc., all resulting from impacts with space debris. The ISS has a lot of shields all over able to withstand impact with objects smaller than a few mm. For instance, the windows of the ISS are not simply a few layers of glass; there's pressure panes, primary shield, secondary shield, scratch panes, etc. Teh overall thickness of a window can exceed 40cm. The shield in front of a window is designed to be strong enough to break any impacting particle up into lower-mass dust, which then sprays out over the deliberate spacing between the primary shield and auxiliary pressure pane, the latter of which is then able to withstand the lower energy impact of the dust. It's kind of like bullet-proof glass, but then for bullets travelling several km/s :) 
Space debris is not really a problem yet, because even though there is a large number of objects orbiting the Earth, the volume they fly through is so vast that the average density is still very low. But, when things like this happen, there is a major impact on many space missions, existing and future ones. When not taken seriously between now and ~15 years, space debris might indeed become a real threat, possibly even leading to the Kessler syndrome.
A: That's right. Any significant space debris hit can do heavy damage to spaceship because we don't have shield technology like sci-fi world.
Well, we set spaceship trajectories so that we never encounter space debris in the way (unless intended like once NASA hit a probe to asteroid to study it).
A: Considering that hitting a 1mg grain of dust at 0.1c speed would release the energy equivalent to an explosion of a 200 kg bomb, I really would not hold my breath. The only way I can imagine interstellar travel is as a swarm of nanobots. They would be sent on their way, and would have to be somehow decelerated at the destination. They would not carry fuel, so they would travel "light".
A: Striking a 1 gm meteoroid at 10 % c with a structure like ISS, would not even slow the 1 gm meteoroid down much.  It would make a small hole in, go through and a small hole out. The affected areas would vent atmopshere and need to be sealed, but the structure would survive. Going from 10 % to 9.98 % of light speed.  IF the craft was heavily armored with 4 meter thick shielding, then yes, the result would be more catastrophic with much more energy released.  
Another analogy, is it would be much more likely to survive being shot be like size armor piercing round at 4,000 ft per second than the same size round in hollow point configuration at 1,200 ft per second. 4000 ft per second armor piercing = small hole in, small hole out, not much energy dissipation, (bullet keeps on going with 90+ % of its original velocity). The hollow point would = small hole in, expansion, great energy dissipation and large tissue/bone destruction, perhaps no exit wound or a huge exit.
A: i just think there is a way to do this without sustaining maximum impact damage
redirection is always a good route to take for diversion of weighted impacts
and there are more than several different ways to redirect and some may even be combined together to increase the success odds
but if the ship were to have an outer reflective layer or divertive layer with a reinforced hull underneath itd be just fine with a pointy tipped nose for deflection thru aeronautics and speed acceleration as well but diverting it along the side of the ship is always going to be way less of a weighted impact than the direct collision impact weight
maybe even have a false diversion up ahead of the ship to divert ahead of time that way the direct impact would be either inflicted to the false application and also possibly divert its path from the main ship altogether.
Having a projectile defense system would be greater for the obvious size problems but the mini ones that are too fluent and aggressive are best left to diversion tactics and would be more than minimized with such diversions
not to mention as stated up above how using a planet or other objects orbital pull to deflect paths of smaller objects or alter the trajectory altogether.
sorry i just didnt have time to get all nerdy with the reference tools and i did also mention another answer lol and i know my answer is not how its supposed to be and for that i apologize and hope you have a great day anyways!!! big squeezies fellow earthlings!!! <3
