Artemis II: What is a 'wet' rehearsal?

The countdown to launch is inching ever closer for Nasa's Artemis II Moon mission!

As part of the mission four astronauts will take part in a 10-day mission to fly around the Moon and back again.

It's been 50 years since any country last sent astronauts to the Moon, and the mission is part of Nasa's long-term plan to eventually have astronauts live on the Moon.

The US Space Agency is now aiming to carry out a 'wet' rehearsal of the SLS (Space Launch System) rocket rocket launch on Monday 2 February, with the aim to carry out the real launch from as soon as 8 February onwards, if the weather conditions are right.

But what is a 'wet' rehearsal and why do rockets need to have them? Find out below!

In a school play, a dress rehearsal is a full practice-run of something before it happens.

For the rocket launch, this means that the Nasa teams will run through nearly every single step of the countdown sequence that would happen on the day of the real thing to check that everything is working properly.

Two important things will be missing from the rehearsal compared to the actual launch are: the astronauts and the actual blast off.

The reason it is called a 'wet' dress rehearsal is because the rocket's tanks are filled with liquid propellants, such as liquid oxygen and liquid hydrogen, as opposed to a "dry" rehearsal which doesn't have any propellants.

The 'wet' rehearsal will stop at the point where lift-off would happen.

There are lots of important factors that the Nasa engineers will have to consider before committing to a launch date, the most important of these being weather.

How windy, rainy or hot or cold it is, could have a big impact on the launch.

Just like Goldilocks's porridge the conditions have to be 'just-right' for lift-off to happen.

Currently engineers have worked out three possible launch windows when the conditions might be just right for blast-off.

These are:

The astronauts are currently in quarantine ahead of the launch.

This means that they have to limit their exposure to others to make sure they don't get sick ahead of the mission.

It's called the Health Stabilization Program and usually starts around 14 days before launch.

The astronauts will still continue their training during this period as well as mission simulations and medical checks being carried out.

They will fly to Nasa's Kennedy Space Centre in Florida around six days before the launch.