As of 2023, the fastest spacecraft capable of interplanetary travel is the Solar Probe Plus (also known as Parker Solar Probe). It is a robotic spacecraft that was launched in 2018 and is designed to make multiple close encounters with the Sun to study its atmosphere and magnetic field.

The spacecraft is powered by a Delta IV Heavy rocket launched from Cape Canaveral, Florida, on August 12, 2018. It achieved its first close encounter with the Sun on November 5, 2018, traveling at a speed of about 430,000 mph (about 690,000 km/h) relative to the Sun, and has made multiple close encounters since then, achieving an overall top speed of about 324,000 mph (about 519,000 km/h) relative to the Sun.

While Solar Probe Plus is the fastest spacecraft capable of interplanetary travel, it was designed to study the Sun and is not aimed at traveling to other planets. The journey to Neptune would likely take several decades using current technology. Additionally, the spacecraft is not designed to carry human passengers, so any journey to Neptune would have to be fully autonomous, which is currently not possible with existent technology.

It is worth noting that there are several ongoing missions that are exploring the outer Solar System, such as NASA's New Horizons mission to Pluto and the Kuiper Belt, and the ESA's Rosetta mission to comet 67P/Churyumov-Gerasimenko. While these missions involve advanced spacecraft that utilize a combination of propulsion systems and gravitational assists to achieve high velocities, they still require many years to reach their destinations, often requiring multiple flybys of other planets to gain the necessary speed and trajectory to reach their targets.

So, in summary, while it is possible to launch a spacecraft that can travel to Neptune using current capabilities and technology, the journey would likely take several decades and require a combination of advanced propulsion systems, gravitational assists, and sophisticated autonomous navigation systems that are currently being developed and tested by various space agencies.
spam fails_task lang_mismatch pii not_appropriate hate_speech sexual_content quality toxicity humor helpfulness creativity violence