SpaceX's Starship 40 rocket has begun the long journey home after being retrieved from waters off Christmas Island.
Carrying the precious cargo, heavy duty transport vessel Forte departed the island on Friday afternoon, headed for the United States.
The rocket splashed down in the Indian Ocean on July 24, and spent just over three weeks at sea before being towed to Christmas Island, about 1,500 kilometres off Western Australia's northern coast.
The Forte arrived in Flying Fish Cove last Sunday night, with the delicate operation to retrieve the rocket getting underway on Tuesday.
The vessel's ballast tank was filled with water to change the buoyancy of the ship, lowering its deck below the surface.
Local stevedores assisted in the operation to position the rocket over the Forte before the vessel refloated, lifting the SpaceX cargo out of the water for the first time in more than a month.
Locals farewell SpaceX rocket
The Christmas Island community has been captivated by the rocket, which sheltered just off the coast.
Local school students followed the Starship's movements, and social media feeds were flooded with images of the rocket, with a local dive company offering 'rocket trips'.
A local bar even named a cocktail Rocket Fuel in honour of the unexpected arrival, with crew members involved in the retrieval leaving a message on its wall.
Local tourism operator Lisa Preston has been hosting 30 birdwatchers for the island's annual Bird Week, who have been excited to witness the retrieval operation.
Ms Preston said it had been an amazing journey, and the Christmas Island community enjoyed being in the global spotlight.
"The decision being made to tow the rocket here when there's thousands of kilometres of coastline south of us, to be able to fulfil that role, to protect it whilst they did what they needed to do … it shows we've got alternate uses for positive things."
Expensive exercise
The journey of about 20,000 kilometres back to the Starbase rocket development facility in Texas is expected to take several weeks.
University of Sydney Professor of Marine Robotics Stefan Williams said the cost of the retrieval operation would add up quickly.
"We operate pretty regularly on research vessels which can cost $50,000 to $100,000 a day to operate, these are even bigger vessels," he said.
"There's a significant cost involved, both in rescue operations and also in the transport of the equipment from where it's been retrieved, in this case back to the home base in the US."
Professor Williams said semi-submersible vessels like the Forte were quite common, but using such a large ship was a heavy-duty operation.
"They're used extensively in the offshore industry in oil and gas and increasingly in offshore wind, anywhere you need large bits of equipment to be moved around," he said.
Starship 40's legacy
The 52-metre-long rocket is the first SpaceX upper stage spacecraft to survive a space flight intact and could provide a wealth of information for engineers.
One of the goals for the space company is developing a rocket that can return safely to its launch site and be used again.
Astronomer Matt Woods says SpaceX's program is helping to make space exploration more affordable.
"Just off the back of the first stage of Falcon 9 and Falcon Heavy [rockets], it's dropped the price down on rockets dramatically," he said.
"It's amazing what you can do and how cheap it is for companies and universities to put the satellites up there and continue doing their study of the universe."
