About the same. New Horizons was faster at launch, but the real boosts come from gravitational assists. Clever choices of orbits buy you speed - stealing an in

About the same. New Horizons was faster at launch, but the real boosts come from gravitational assists. Clever choices of orbits buy you speed - stealing an infinitesimal fraction of Jupiter's momentum is much more efficient than any propulsion technology in use. If that ever changes, then "too soon" will have become reality. From http://en.wikipedia.org/wiki/New_Horizons http://en.wikipedia.org/wiki/New_Horizons "New Horizons is often given the title of Fastest Spacecraft Ever Launched, although the Helios probes are arguably the holders of that title as a result of speed gained while falling toward the Sun. New Horizons, however, achieved the highest launch velocity and thus left Earth faster than any other spacecraft to date. It is also the first spacecraft launched directly into a solar escape trajectory, which requires an approximate velocity of 16.5 km/s (36,900 mph), plus losses, all to be provided by the launcher. However, it will not be the fastest spacecraft to leave the Solar System. This record is held by Voyager 1, currently travelling at 17.145 km/s (38,400 mph) relative to the Sun. Voyager 1 attained greater hyperbolic excess velocity from Jupiter and Saturn gravitational slingshots than New Horizons. Other spacecraft, such as Helios 1 & 2, can also be measured as the fastest objects, due to their orbital velocity relative to the Sun at perihelion. However, because they remain in solar orbit, their orbital energy relative to the Sun is lower than the five probes, and three other third stages on hyperbolic trajectories, including New Horizons, that achieved solar escape velocity, as the Sun has a much deeper gravitational well than Earth."