A Soyuz-2.1a rocket lifts off on April 19, 2013, with Bion-M №1. Rockets don’t accelerate much faster than cars or objects in free-fall on Earth, but the key limitation is that they cannot maintain that acceleration indefinitely. If they could, here’s what would suddenly be within reach. (ROSKOSMOS)

How Far Could A Human Travel In A Constantly-Accelerating Rocket Ship?

Imagine you had perfect technology and unlimited fuel. How far could you go?

Human spaceflight has brought us beyond Earth, but we could potentially venture even farther.

The very first launch from NASA’s Cape Kennedy space center was of the Apollo 4 rocket. Although it accelerated no faster than a sportscar, the key to its success was that the acceleration was sustained for so long. The Saturn V rockets would later take humanity to the Moon. Although we’ve never ventured farther than Apollo took us all those decades ago, our potential to explore the Universe goes far beyond what we’ve already accomplished. (NASA)

Imagine that we could constantly accelerate at the same rate as Earth’s gravitational pull, 9.8 m/s², indefinitely.

A multistage rocket that lost and jettisoned mass as it moved faster and faster would be required to reach speeds approaching the speed of light, like the Super Haas rocket shown here. You must either posses a super-efficient type of fuel or gather more fuel along your journey to achieve relativistic speeds. In theory, a ship with constant acceleration could take us farther into the Universe than anything else we’ve hitherto envisioned. (DRAGOS MURESAN, UNDER C.C.A.-S.A.-3.0)

While you’d initially speed up, you’ll rapidly approach the speed of light.

A “light clock” will appear to run different for observers moving at different relative speeds, but this is due to the constancy of the speed of light. Einstein’s law of special relativity governs how these time and distance transformations take place between different observers.(JOHN D. NORTON, VIA PITT.EDU/~JDNORTON/TEACHING/HPS_0410/CHAPTERS/SPECIAL_RELATIVITY_CLOCKS_RODS)

Owing to Einstein’s Special Relativity, time will dilate and lengths will contract.

One revolutionary aspect of relativistic motion, put forth by Einstein but previously built up by Lorentz, Fitzgerald, and others, is that rapidly moving objects appear to contract in space and dilate in time. The faster you move relative to someone at rest, the greater your lengths appear to be contracted, while the more time appears to dilate for the outside world. (CURT RENSHAW)