New Horizons - Launch

Launch

The launch of New Horizons was originally scheduled for January 11, 2006, but was initially delayed until January 17 to allow for borescope inspections of the Atlas rocket's kerosene tank. Further delays related to low cloud ceiling conditions downrange, and high winds and technical difficulties — unrelated to the rocket itself — prevented launch for a further two days. The probe finally lifted off from Pad 41 at Cape Canaveral Air Force Station, Florida, directly south of Space Shuttle Launch Complex 39, at 14:00 EST on January 19, 2006.

The Centaur second stage reignited at 14:30 EST (19:30 UTC), successfully sending the probe on a solar-escape trajectory. New Horizons took only nine hours to reach the Moon's orbit, passing lunar orbit before midnight EST that day.

Although there were backup launch opportunities in February 2006 and February 2007, only the first 23 days of the 2006 window permitted the Jupiter fly-by. Any launch outside that period would have forced the spacecraft to fly a slower trajectory directly to Pluto, delaying its encounter by 2–4 years.

The craft was launched by a Lockheed Martin Atlas V 551 rocket, with an ATK Star 48B third stage added to increase the heliocentric (escape) speed. This was the first launch of the 551 configuration of the Atlas V, as well as the first Atlas V launch with an additional third stage (Atlas V rockets usually do not have a third stage). Previous flights had used none, two, or three solid boosters, but never five. This puts the Atlas V 551 take-off thrust, at well over 2,000,000 lbf (9 MN), past the Delta IV-Heavy. The major part of this thrust is supplied by the Russian RD-180 engine, providing 4.152 MN (933,000 lbf). The Delta IV-H remains the larger vehicle, at over 1,600,000 lb (726,000 kg) compared to 1,260,000 lb (572,000 kg) of the AV-010. The Atlas V rocket had earlier been slightly damaged when Hurricane Wilma swept across Florida on October 24, 2005. One of the solid rocket boosters was hit by a door. The booster was replaced with an identical unit, rather than inspecting and requalifying the original.

The Star 48B third stage is also on a hyperbolic Solar System escape trajectory, and reached Jupiter before the New Horizons spacecraft. However, since it is not in controlled flight, it did not receive the correct gravity assist, and will only pass within 200,000,000 km (120,000,000 mi) of Pluto.

New Horizons is often erroneously given the title of Fastest Spacecraft Ever Launched, when in fact the Helios probes are the holders of that title. New Horizons 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.