This really depends on what you mean by space. If you just want to get into orbit around the Earth, you should reach speeds of at least 4.9 miles per second or around 17,600 miles per hour. The closest star to Earth is Proxima Centauri. It's about 4.25 light-years away, or about 25 trillion miles (40 trillion km).
The fastest spacecraft in history, the Parker solar probe, now in space, will reach a maximum speed of 450,000 miles per hour. It would take just 20 seconds to get from Los Angeles to New York City at that speed, but it would take about 6,633 years for the solar probe to reach the nearest neighboring solar system to Earth. The speeds required for interstellar travel in human life far exceed those that can be provided by current space travel methods. Even with a hypothetically perfectly efficient drive system, the kinetic energy corresponding to those speeds is enormous by current energy development standards.
In addition, collisions of spaceships with cosmic dust and gas at such speeds would be very dangerous both for passengers and for the spacecraft itself. In essence, the ship resides within a piece of space-time, a “warp bubble” that moves faster than the speed of light. For example, a spacecraft could travel to a star 32 light-years away, initially accelerating at a constant speed of 1.03 g (i). In theory, this approach does not contradict the laws of relativity, since you don't move faster than light in the space around you.
Regardless of how this is achieved, a propulsion system that could produce continuous acceleration from departure to arrival would be the fastest method of travel. However, let's suppose that you could somehow compress the space between you and point B so that the interval is now just one meter. Interstellar travel is expected to be much more difficult than interplanetary space flights due to the large difference in the scale of the distances involved. The possibility of making that trip, only to spend the rest of the colony's life inside a sealed habitat and venture out in a space suit, can eliminate many potential targets from the list.
Scientists are investigating many other ways to go fast, including distortion travel, the faster-thread-thread-light trip popularized by Star Trek. The crew of an interstellar ship would face several major dangers, including the psychological effects of prolonged isolation, the physiological effects of extreme acceleration (if it exceeded the acceleration of 1 g), the effects of exposure to ionizing radiation from space and possibly from the ship's engines, and the physiological effects of weightlessness on muscles, joints, bones, the immune system and eyes. In this scheme, a 30-kilometer secondary sail is deployed at the rear of the spacecraft, while the large main sail is separated from the ship to continue moving forward on its own. The spacecraft itself, as proposed, used a 12,000,000 ton ball of frozen deuterium to power between 12 and 24 thermonuclear impulse propulsion units.
At several hundred million kilometers per hour, every speck in space, from lost hydrogen gas atoms to micrometeoroids, in effect becomes a high-powered bullet that hits the hull of a ship. Undoubtedly, micrometeoroids are not the only obstacle to future space missions, in which higher human travel speeds would probably come into play. Speculative dangers could also arise if humans manage to travel faster than light, either by taking advantage of gaps in known physics or through paradigm-breaking discoveries. However, shortening travel times would mitigate these problems, making a faster approach highly desirable.
All rockets, even the sleek new rockets used by SpaceX and Blue Origins, burn rocket fuel that's not much different from car gasoline. .
