Humanity is doomed. Even at a mere 1500 km/sec (0.5 percent lightspeed), or less than 3-times the escape velocity of the sun, the impact of a micrometeorite would destroy any spacecraft. A typical 10 gram micrometeorite would impact with the energy of 2.7 tons of TNT. The Oklahoma City bombing was less powerful between 1-2 tons of TNT. The explosion that destroyed the Russian submarine Kursk was also less powerful at about 2 tons of TNT, but it was registered by seismic stations in several countries. Even a tapered titanium-constructed spacecraft (10 meters wide, 51000 meters long) that "brushes off" to the side any meteorite impact would still accumulate enough damage to render it garbage in far less than the 860 years needed to make it to the nearest star system Alpha Centauri. It would be too massive to get up to speed, requiring at least 3 million pounds thrust for nearly a year to reach cruise speed of 1500 km/sec. Look at the world we live in. We have not yet come up with a way to survive that does not require a cities and urban congestion and depletion of resources. Crime is rampant. People are vicious to one another. What a 5hithole we live in. Humanity is doomed.