An attempt to launch the most
powerful ever rocket into space has been postponed for at least 48 hours.
The vehicle, known as Starship, has been built by entrepreneur
Elon Musk's SpaceX company.
The uncrewed mission on Monday was called off minutes before the
planned launch from Boca Chica, Texas.
The problem appears to have been caused by a frozen
"pressurant valve", Musk tweeted. But SpaceX could try to launch
again later this week.
Starship stands nearly 120m (400ft) high and is designed to have
almost double the thrust of any previous rocket.
The aim is to send the upper-stage of the vehicle eastward, to
complete almost one circuit of the globe.
Before the launch was postponed, Mr Musk had appealed for
everyone to temper their expectations. It's not uncommon for a rocket to
experience some kind of failure on its initial outing.
"It's the first launch of a very complicated, gigantic
rocket, so it might not launch. We're going to be very careful, and if we see
anything that gives us concern, we will postpone the launch," he had told
a Twitter Spaces event.
Thousands of spectators filled coastal locations on the Gulf of
Mexico to witness the event.
It's designed to be fully and rapidly reusable. He envisages
flying people and satellites to orbit multiple times a day in the same way a
jet airliner might criss-cross the Atlantic.
Indeed, he believes the vehicle could usher in an era of
interplanetary travel for ordinary humans.
This mammoth booster, suitably called Super Heavy, was fired
while clamped to its launch mount in February. However, the engines on that
occasion were throttled back to half their capability.
If things go to plan for another launch this week, SpaceX will
aim for 90% thrust, meaning the stage should deliver something close to 70 meganewtons.
This is equivalent to the force needed to propel almost 100 Concorde supersonic
airliners at take off.
Assuming everything proceeds as planned, Starship will rise up
and head down range across the Gulf, the 33 engines on the bottom of the
methane-fuelled booster burning for two minutes and 49 seconds.
At that point, the two halves of the rocket will separate, and
the top section, the ship, will push on with its own engines for a further six
minutes and 23 seconds.
By this time, it should be travelling over the Caribbean and
cruising through space more than 100km (62 miles) above the planet's surface.
SpaceX wants the Super Heavy booster to try to fly back to near
the Texan coast and come down vertically, to hover just above the Gulf's
waters. It will then be allowed to topple over and sink.
The ship is expected to re-enter the Earth's atmosphere after
almost a full revolution of the Earth, coming down in the Pacific just north of
the Hawaiian islands. It's been given protective tiling to cope with the
immense heating it will experience during the descent.
A bellyflop into the ocean is timed to occur roughly an hour and a half after lift-off.
In the longer term, SpaceX expects both the booster and the ship
to be making controlled landings so they can be refuelled and relaunched.
The company has been experimenting at Boca Chica with different
approaches to building the steel stages.
There are various models waiting their turn to take flight.
One of the most interested spectators on Monday will have been
the US space agency, Nasa.
It is giving SpaceX almost $3bn to develop a variant of 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 the ambition to go even
deeper into the Solar System.
"He sees Starship as potentially another giant paradigm shift,
an incredible increase in capability - the capability to truly bring people on
large scale to Mars," the SpaceX advisor and former astronaut told BBC
News.
"There's a lot of potential benefit, but there's also a lot
of potential risk because this is very difficult. Nobody's built a rocket
anywhere near this big - twice as big as the next nearest thing."
