page_title: Space travel using constant acceleration
section_title: Ship reference frame
hierarchical_section_title: Space travel using constant acceleration / Interstellar travel / Interstellar traveling speeds / Ship reference frame
caption_attribution_description: English: Accelerated twin roundtrip with two sequential constant proper acceleration/deceleration pairs, over a travel distance of 10 c2/α, where c is lightspeed and α is the proper acceleration magnitude.
context_page_description: Constant acceleration is a proposed aspect of most future forms of space travel. It entails that the propulsion system of whatever kind operate continuously with a steady acceleration, rather than the brief impulsive thrusts used by chemical rockets—for the first half of the journey it constantly pushes the spacecraft towards its destination, and for the last half of the journey it constantly uses backthrust, so that the spaceship arrives at the destination at a standstill.
context_section_description: From the frame of reference of those on the ship the acceleration will not change as the journey goes on. Instead the planetary reference frame will look more and more relativistic. This means that for voyagers on the ship the journey will appear to be much shorter than what planetary observers see.
  At a constant acceleration of 1 g, a rocket could travel the diameter of our galaxy in about 12 years ship time, and about 113,000 years planetary time. If the last half of the trip involves deceleration at 1 g, the trip would take about 24 years. If the trip is merely to the nearest star, with deceleration the last half of the way, it would take 3.6 years.
caption: Plot of velocity parameters and times on the horizontal axis, versus position on the vertical axis, for an accelerated twin roundtrip to a destination with ΔxAB=10c2/α ~10 lightyears away if α~9.8 m/s2.
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