Space Travel Calculator

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Both systems use light-years for distance and g for acceleration; this switch changes supplemental outputs.
Distance in light-years. Proxima Centauri is 4.24 ly, Andromeda is about 2.5 million ly.
light-years
1 g (9.81 m/s^2) is comfortable for humans and coincidentally produces fast interstellar travel.
g
Arrive-and-stop flips thrust at the midpoint to brake; flyby keeps accelerating the whole way but arrives at maximum speed.
Dry mass of the spacecraft excluding fuel, used to estimate fuel requirements. 25,000 kg is roughly ISS module scale.
kg
Ship time (crew experience)Ultra-relativistic
3.54

Proper time elapsed on the spacecraft, experienced by the crew

Earth time elapsed5.866
Ship time (formatted)3.54 years
Earth time (formatted)5.87 years
Maximum velocity (fraction of c)0.949547
Maximum velocity94.9547 % of c
Lorentz factor (gamma)3.189
Time dilation ratio1.657
Fuel-to-payload mass ratio37.64
Fuel mass required941024 kg
Distance in km40.11 trillion km
Ship time (years)3.54
Earth time (years)5.866

Journey to 4.24 light-years: crew time 3.54 years, Earth time 5.87 years.

  • For every year the crew experiences, approximately 1.66 years pass on Earth. The crew ages 3.54 years while Earth ages 5.87 years.
  • The spacecraft peaks at 94.955 % of light speed, giving a Lorentz factor of 3.189. At this speed, lengths appear contracted by the same factor from Earth's frame.
  • The arrive-and-stop journey reverses thrust at the midpoint (2.12 ly) to decelerate. This requires significantly more fuel than a flyby.
  • A fuel-to-payload ratio of 38 is extraordinarily demanding. No current or near-future technology can achieve this.

Next stepTry 1 g acceleration to Andromeda (2.537 million ly) to see how 28 years of ship time map to 2.5 million years of Earth time, and why fuel requirements make it currently science fiction.

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