Alys Davies
BBC News Live reporter

Image source, AFP

We're now wrapping up our coverage for the day. Sadly SpaceX's Starship didn't make take-off as planned but we will be sure to cover the story on the next scheduled launch day.

In the meantime this is what we've learned today.

• SpaceX owner Elon Musk said the decision to halt the launch was down to an issue with a frozen valve

• The rest of the launch was carried out as a "wet dress rehearsal" - meaning the rocket was loaded with fuel without it actually being launched
• Musk tweeted to say the team had "learned a lot" and will retry in a "few days"
• The SpaceX team will troubleshoot what went wrong in the meantime
• BBC science editor Rebecca Morelle says pressurisation issues are not uncommon when filling rockets with fuel, especially when trying it for the first time

You can read more about the Starship rocket launch attempt here.

Our live coverage was brought to you today by Jeremy Gahagan, Heather Sharp, Ece Goksedef, Malu Cursino, Krystyna Gajda, James Harness, Thomas Mackintosh and myself.

Image source, Reuters

People have been reacting to the postponement of the Starship launch in Texas on social media.

Nasa space flight writer and reporter Tyler Gray wrote, external: "We were on the verge of greatness. We were this close".

"No launch today, blegh. It's seriously the most beautiful day too!" said, external Bloomberg space reporter Loren Grush.

Jonathan Amos
Science correspondent, BBC News

Elon Musk attaches enormous importance to Starship.

He even sent an email to staff at SpaceX in 2021, warning them the company risked bankruptcy unless they sped up development.

The rocket is critical to his satellite project - the Starlink internet broadband network.

He’s launched over 3,000 satellites for this connectivity system, but needs to loft thousands more; and only Starship has the heft to deliver the latest iterations of Starlink spacecraft at the rate required.

He’s also impatient to get on with his project to colonise Mars. Again, only Starship has the lifting power to send serious quantities of people, supplies and equipment to the Red Planet.

Following the postponement of Starship's launch, Elon Musk tweeted , externalto say his team "learned a lot today".

He also confirmed they'd be "retrying in a few days".

Jonathan Amos
Science correspondent, BBC News

Image source, Airbus

The rocket can't just sit on a launch pad for days on end, full of fuel, waiting to lift off.

The propellants are super-chilled and they constantly need to be replenished during a countdown as some of the liquid warms up and vents to the atmosphere.

SpaceX must de-tank while they work through their valve issue and decide on a new flight day.

The rocket doesn't have the equipment on board to main the liquid methane and liquid oxygen in the correct storage state for extended periods.

This equipment is all off to the side of the launch pad in an area called "the tank farm".

This is the moment SpaceX broke the news that the launch was halted for the day - minutes ahead of the scheduled launch time.

Jonathan Amos
Science correspondent, BBC News

As the rocket takes off, and is starting to exhaust its propellant, you need to maintain pressure in the fuel tanks.

It sounds like the valve that brings the gas into those tanks to pressure them became a bit sticky, so SpaceX were not prepared to take the risk launching Starship should something go wrong.

Apart from this it seems to have gone very well indeed. It looks like they might be able to try again this Wednesday or Thursday.

They already have the permissions they need the Federal Aviation Administration for the rest of this week - this will clear the airspace and make sure there's no marine traffic in the area.

So all being well, they should be good to go in the next few days.

SpaceX owner Elon Musk has said on Twitter, external that a "pressurant valve appears to be frozen" and was the cause of today's postponement.

Rebecca Morelle
Science editor

It came close - but with a few minutes go SpaceX has announced that we won’t get to see the rocket fly today.

A pressurisation issue in the first stage of the rocket was the problem.

It’s not uncommon - filling a rocket with fuel is a tricky business - and it’s especially hard the first time you do it.

But while the flight was paused, SpaceX decided to carry on with the countdown. It's a chance to turn this into a wet dress rehearsal - a chance to run through what would happen if the rocket was to fly.

They’ll now have to troubleshoot the pressure issue - to find out exactly what went wrong. It will take a minimum of 48 hours to reset the rocket before they can try again.

Image source, Reuters

The rocket will not launch today, SpaceX say.

They are continuing with the preparations for launch as a "wet dress rehearsal", which means it includes the loading of the rocket with fuel.

The practice will go right up to what would happen ten seconds before launch - then they will stop the clock.

SpaceX says they are about to stop the launch, and will carry it on as a dress rehearsal instead.

The SpaceX team earlier said it was working through a "pressurization issue" and it would not launch today if it wasn't resolved.

Rebecca Morelle
Science editor

Starship is a whopper: fully stacked it stands about 120m-tall.

Compare that with Nasa’s Saturn V (111m), which launched the Apollo missions; and the test version of Nasa’s Artemis rocket, or Space Launch System (SLS) (98m), which will eventually be returning astronauts to the Moon.

In fact, it’s the biggest rocket ever built - and the most powerful too. It’s designed to have up to 75 meganewtons, 17 million pounds, of thrust (the force that propels the rocket through the air). That’s getting on for twice as much as the SLS.

And this is key, because the more thrust a rocket has, the more weight it can lift off the ground - so that means it can carry more stuff into space.

SpaceX estimates it can put up to 150 tonnes in the spacecraft’s reusable form - be that cargo or people.

There's just 20 minutes to go now until the Starship's scheduled launch time.

You can watch BBC coverage of the build up - and then lift off itself - by clicking the button at the top of the page.

Image source, Reuters

Elon Musk has said "anything that does not result in the destruction of the launch pad" would "be a win" - but what does the best case scenario look like?

At launch, SpaceX wants Starship to rise up and head across the Gulf of Mexico, with the 33 engines on the bottom of the Super Heavy booster - the bottom part of the rocket - burning for two minutes and 49 seconds.

Then, 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 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. Eventually SpaceX wants to be able to reuse these boosters, but this one will then be allowed to topple over and sink.

The ship is aiming to re-enter the Earth's atmosphere after almost a full revolution of the Earth, splashing down in the Pacific just north of the Hawaiian islands.

If all goes as hoped, it will land in the ocean 90 minutes after lift-off.

Image source, .

Image source, Reuters

As we've mentioned, Musk has made it very clear that he doesn't expect things to go smoothly with this launch.

Yesterday, in an event on Twitter Spaces, he said he wanted to "lower expectations as much as possible".

"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 said.

“If we do launch, I would consider anything that does not result in the destruction of the launch pad itself to be a win.

"Success is not what should be expected tomorrow. That would be insane."

Musk said the aim of today's launch is "purely, purely learning".

"So you can think of the payload for this mission is information, information that allows us to improve the design of future Starship builds," he added.

He did, however, give "two or three years" as a timescale in which the company hopes to achieve "full and rapid reusability" for Starship.

About 10 minutes ago Elon Musk himself tweeted , external"liftoff in T minus 1 hour" - which means there's one hour until lift-off, scheduled for 0820 local time in Texas, 1420 BST.

Yesterday he said he wanted to "lower expectations as much as possible" and warning there was a risk the launch could be postponed.

Simon King
BBC weather presenter and meteorologist

While the weather generally looks OK with clear skies during the launch window at Boca Chica in Texas, there will be quite a brisk easterly wind developing.

This could be problematic, especially if there is too much wind shear – a change in wind speed, direction or both with height.

SpaceX have said they’ll be keeping a close eye on this part of the forecast during the morning.

Image source, Reuters

The sun has just risen in Boca Chica, Texas, where crowds have gathered to watch the vast rocket lift off.

The launch time was originally set for 08:00 local time (14:00 BST), but a little while ago SpaceX tweeted, external that it would be 08:20 - so had slipped a little.

Their latest tweet , externalhas just confirmed that fuelling of Starship's upper stage is now under way. The rocket fuel has already been fed into the huge Super Heavy booster.

It's a sign that things are moving ahead - though of course there could still be further delays.

We understand that today's launch window ends at 09:30 local time (15:30 BST).

Jeremy Gahagan
BBC News Live reporter

Image source, Reuters

Hello and welcome to our live coverage of the expected launch of the most powerful rocket ever developed.

Hot on the heels of last week’s launch of the European Space Agency’s mission to Jupiter's moons, we’ve a new launch pad to keep an eye on.

Starship, built by the American entrepreneur Elon Musk's SpaceX company, is due to launch from Starbase in the southern US at 08:20 local time (14:20 BST).

Musk has made it clear there’s a multitude of things that might not go according to plan. He hasn’t ruled out the Starship blowing up its own launch pad and said“success is not what should be expected… that would be insane.”

The uncrewed flight is set to lift off from Boca Chica in Texas.The aim is to send the upper-stage of the vehicle eastward, to complete almost one circuit of the globe before splashing down in the Pacific near Hawaaii.

Heather Sharp and I are at BBC mission control where we’re joined by Alys Davies, Malu Cursino, Ece Goksedef and Krystyna Gajda. We’ll also have the experienced team of Science editor Rebecca Morelle and Science correspondent Jonathan Amos on hand to help bring you the latest updates.

Stay with us as we prepare for launch.