It would take roughly about 12 years to travel to Neptune using current spacecraft technology, as demonstrated by the Voyager 2 mission. Voyager 2 launched in 1977 and reached Neptune in 1989, marking around 12 years of travel time. The time depends on the trajectory, gravity assists, and relative positions of Earth and Neptune in their orbits. Using faster future technology might decrease this time, but significant challenges remain, especially if a spacecraft needs to slow down to enter Neptune's orbit. For a human crewed mission, considering the braking and safety requirements, the total journey could take between 24 to 28 years. In summary:
- Voyager 2 took about 12 years for a flyby mission.
- Orbital insertion or crewed missions might take much longer (potentially 24–28 years).
- Neptune's average distance from Earth is about 4.3 to 4.7 billion kilometers, with light travel time around 4 hours.
This long travel time is due to the vast distance and current propulsion limitations.
