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A Japanese H-2A launcher blasted off from an idyllic island spaceport Tuesday, dispatching a daring six-year expedition to bring a piece of an asteroid back to Earth.

The Hayabusa 2 mission’s roundtrip voyage began at 0422 GMT Wednesday (11:22 p.m. EST Tuesday) with a thunderous ascent from Tanegashima Space Center in southern Japan.

The 1,300-pound spacecraft rode a hydrogen-fueled H-2A rocket through clouds hanging over the seaside spaceport, leaving a twisting column of exhaust in its wake before disappearing hundreds of miles over the Pacific Ocean.

The rocket’s upper stage engine fired two times to accelerate Hayabusa 2 on a speedy departure fast enough to break free of the pull of Earth’s gravity.

The robotic explorer, packed with four stowaway landers to be deployed to the asteroid’s surface, separated from the H-2A rocket at 0609 GMT (1:09 a.m. EST). Applause could be heard in a live webcast of the launch provided by the Japan Aerospace Exploration Agency, which manages the Hayabusa 2 mission.

The launch marked the opening chapter in the most ambitious mission to an asteroid ever attempted. The roundtrip journey will take six years to complete, and Hayabusa 2 promises to expand scientists’ understanding of how asteroids may have seeded Earth with water and organic molecules, the building blocks of life.

Hayabusa 2 is heading for asteroid 1999 JU3, a carbon-rich world just 900 meters — about 3,000 feet — across with a tenuous gravity field 60,000 times weaker than Earth’s.

The mission follows up on the achievements of Japan’s Hayabusa 1 probe, which made the first roundtrip flight to an asteroid from 2003 to 2010. The first Hayabusa mission encountered several crippling problems, including a fuel leak, failures in its pointing system, and a glitch with the craft’s sample collection system.

Despite the challenges, the spacecraft returned to Earth in 2010 — a few years late and carrying a fraction of the asteroid specimens intended. But Japanese scientists found microscopic samples from asteroid Itokawa — Hayabusa 1’s research subject — inside the probe’s landing vehicle.

The success vaulted Japan into the big leagues of solar system exploration.

“Many scientific milestones have been achieved from asteroid observations and samples from the asteroid Itokawa,” said Tetsuo Tanaka, associate director general of JAXA’s Lunar and Planetary Exploration Program Group. “Going to a far-off asteroid and returning with samples from it for the first time, these are tremendous technological challenges and our success in meeting them has brought worldwide admiration.”

“For the Hayabusa 2 project, Japan’s development of its own deep space exploration technology aims to lead the world in that technical field,” Tanaka said. “The Hayabusa 2 project sets new challenges for Japan’s unique technologies. How we face those challenges and how we use (the) project results will surely bring new impacts to the world.”

But Hayabusa’s troubles meant it was prudent for engineers to make changes on Hayabusa 2.

“We changed a lot of parts on Hayabusa 2,” said Hitoshi Kuninaka, JAXA’s Hayabusa 2 program manager. “We installed four reaction wheels, and Hayabusa 1 had only three. The sampling system also has some improvements. Our operations software was upgraded for better proximity operations around the asteroid.”

Hayabusa 2’s electrically-powered ion engines were upgraded to produce more thrust, and engineers installed a Ka-band antenna to beam data back to Earth at four times the rate possible on the first Hayabusa mission.

The spacecraft will arrive at the asteroid in June 2018 after swinging by Earth late next year to get a boost to the mission’s destination, which circles the sun between the orbits of Earth and Mars.

The probe will initially park itself 20 kilometers, or about 12 miles, from the asteroid for a comprehensive survey with a set of spectrometers, cameras, and other sensors to map the tiny world.

Then scientists will start to look for suitable sites on the asteroid to put down four diminutive landing drones and scoop up samples for return to Earth.

Hayabusa 2 will spend a year-and-a-half at asteroid 1999 JU3, enough time for the probe to pick up rock specimens from three different locations on the unexplored asteroid.

One of the samples is supposed to come from material excavated from beneath the asteroid’s surface. Hayabusa 2 will use explosives to fire a copper impactor into the asteroid to carve an artificial crater, exposing underground pristine rocks for the probe to pick up during a touch-and-go maneuver.

“The most difficult operations are, I think, the impactor operations,” Kuninaka said. “Scientists want to get materials from inside of the asteroid, so we developed the impactor … That is a very difficult operation. Once we release the impactor from the asteroid, it will be ignited about 40 minutes later. We cannot stop that ignition, so before the ignition the spacecraft will do an escape maneuver to the other side of the asteroid, and the time is very limited. We have to do the escape maneuver so the spacecraft will avoid serious damage from the impactor. I think that is one of the most difficult operations we have ever done.”

The spacecraft’s sampling mechanism works by shooting a small bullet into the asteroid after it dips down to the surface. When the bullet fires while Hayabusa 2’s sampling funnel is in contact with the asteroid, engineers believe bits of gravelly rock will be blasted through a tube into a collection chamber for storage inside the mission’s return capsule.

Hayabusa 2 carries four landers, including a 22-pound robot named MASCOT built by the same team that managed the Philae comet lander that touched down on comet 67P/Churyumov-Gerasimenko on Nov. 12.

Three other landing craft built in Japan will also descend to the asteroid during Hayabusa 2’s mission.

The landers are mobile and will use mechanisms to hop across the asteroid to study its environment from several locations.

“We are going to operate simultaneously a large group of robotics on the surface of the asteroid,” Kuninaka said. “That will be an immense engineering challenge to operate many robots at the same time on the asteroid.”

Once the mission’s work at the asteroid is complete, Hayabusa 2 will leave and head for Earth in December 2019.

Hayabusa 2 will release a container with the asteroid samples for a blazing re-entry through Earth’s atmosphere for a parachute-assisted landing in the Australian outback in December 2020.

In an interview with Spaceflight Now before the launch, Kuninaka said Hayabusa 2 has a dual purpose as a machine for scientific discovery and a testbed for new technologies that could advance space exploration.

“Learning about asteroids is important for the future of space exploration,” Kuninaka said. “This is a difficult mission, but in order for humans to expand from Earth into space, it will be necessary to meet challenges. We need a lot of technology and information about the solar system, and Hayabusa 2 will make a big step in these areas to help us be ready to plan and collaborate in the next step of space exploration.”

Follow Stephen Clark on Twitter: @StephenClark1.