The average speed of a generation ship can vary depending on various factors such as propulsion technology, distance to be covered, and mission objectives. A generation ship is a hypothetical concept designed for long-duration space travel, often spanning multiple generations of inhabitants.
Since generation ships are envisioned for interstellar travel, the speeds involved would typically be a significant fraction of the speed of light (c), which is approximately 299,792 kilometers per second (186,282 miles per second). However, achieving such high speeds is extremely challenging due to the limitations of current propulsion systems and the energy requirements involved.
Realistically, generation ships would likely travel at a fraction of the speed of light, taking into account the physical constraints and technological capabilities of the time. Proposed methods for interstellar travel, such as using nuclear propulsion, ion propulsion, or even concepts like antimatter propulsion, could potentially achieve speeds of around 10-30% of the speed of light.
It's important to note that even at these speeds, interstellar distances would take a significant amount of time to traverse. Journey times of several decades or even centuries would be expected, which is why generation ships are designed to sustain multiple generations of crew members who are born, live, and die during the journey.
Keep in mind that the concept of generation ships is largely theoretical at this point, and no operational generation ship has been built or deployed. Research and advancements in propulsion technology are ongoing, and future developments may alter our understanding of achievable speeds for such interstellar journeys.