- By Jonathan Amos
- BBC Science Correspondent
The most powerful rocket ever built is about to attempt a maiden launch.
The vehicle, known as Starship, was built by American entrepreneur Elon Musk’s SpaceX company.
It stands almost 120m (400ft) tall and is designed to have almost twice the thrust of any rocket in history.
Monday’s uncrewed demonstration will depart from Boca Chica in Texas. The goal is to send the long stage vehicle eastward, to complete almost a circuit of the world.
Mr Musk appealed to everyone to temper their expectations. It is common for a rocket to experience some sort of failure on its first launch.
“This is the first launch of a very complex, giant rocket, so it will not launch. We will be very careful, and if we see anything that gives us concern, we will postpone the launch,” he said at a Twitter Spaces event.
“When we launch, I’ll consider anything that doesn’t result in the destruction of the launch pad itself a victory.”
Thousands of spectators are expected to try to reach locations along the Gulf of Mexico coast to witness the event.
Elon Musk hopes to completely scale up the rocket business with Starship.
It is designed to be fully and rapidly reusable. He envisions sending people and satellites into orbit several times a day in the same way that a jet airliner might criss-cross the Atlantic.
In fact, he believed that the car could usher in an era of interplanetary travel for ordinary people.
The upper part of the Starship has been tested in the past with short hops, but this is the first time it will climb its lower stage.
This mammoth booster, called the Super Heavy, was fired while clamped onto the launch mount in February. However, the engines on that occasion were turned back to half their capabilities.
If, as promised, SpaceX goes to 90% thrust on Monday, the stage should deliver something close to 70 meganewtons. This is equivalent to the force required to propel nearly 100 Concorde supersonic airliners on takeoff.
Assuming all goes as planned, the Starship will rise and head down into the Gulf, the 33 engines under the methane-fuelled booster burning for two minutes and 49 seconds.
At that point, the two parts of the rocket will separate, and the upper section, the ship, will continue with its own engines for an additional six minutes and 23 seconds.
At this time, it must have traveled to the Caribbean and traveled in space more than 100km above the surface of the planet.
SpaceX wants the Super Heavy booster to try to fly back near the Texan coast and descend vertically, to fly over the waters of the Gulf. Then let it fall and sink.
The ship aims to re-enter the Earth’s atmosphere after almost a complete revolution of the Earth, descending into the Pacific just north of the Hawaiian islands. It is provided with protective tiling to cope with the extreme heat it will experience during the descent. The bellyflop into the sea is scheduled to take place 90 minutes after liftoff.
In the longer term, SpaceX expects the booster and ship to make controlled landings so they can be refueled and relaunched.
The company experimented in Boca Chica with different methods of making steel vehicles.
There are various models waiting for their turn to fly.
One of the most interested spectators on Monday was the US space agency, Nasa.
It gave SpaceX nearly $3 billion to develop a variant of the Starship that is planned to land astronauts on the Moon.
Garrett Reisman, a professor of astronautical engineering at the University of Southern California, says Mr Musk has ambitions that go deeper into the Solar System.
“He sees Starship as being another giant paradigm shift, an incredible increase in capability — the ability to actually take people on a large scale to Mars,” the SpaceX adviser and former astronaut told BBC News.
“There’s a lot of potential benefit, but there’s also a lot of potential risk because it’s so difficult. Nobody’s built a rocket anywhere near this big — twice as big as the next closest thing.”