Why can't Artemis II just launch right away? This is what it takes to get astronauts to the Moon and back

We could be just weeks away from the launch of Artemis II, the first mission to take humans to the Moon since the end of the Apollo programme.

Artemis II will not land on the Moon, but will instead take a crew of four astronauts around the far side of the Moon and back again.

This will give the crew a rare opportunity to see something only a select few astronauts have ever witnessed: the side of the Moon that never faces Earth.

The Artemis II crew is comprised of Commander Reid Wiseman, Pilot Victor Glover and Mission Specialists Christina Koch and Jeremy Hansen.

As you might expect, launching astronauts to the Moon is no easy task.

Beyond the feat of building a rocket to safely launch a space capsule that can keep four human beings alive during a journey to the Moon and back, there are many other things to consider.

As NASA's confirmed Artemis II launch dates show, the window is months-long, taking into account all matter of eventualities.

Here's a quick look at what needs to happen before launch, and why Artemis II can't simply launch as soon as the astronauts are ready.

Find out more about the mission with our quick Artemis II facts.

Preparing for Artemis II launch

As we saw with Artemis I, delays to the launch of Artemis II are highly possible.

NASA has said it "will pause to address any issues during the test or at any other point should technical challenges arise."

There are numerous aspects of the launch that engineers will need to keep an eye on, both during the launch itself and during the 'wet dress rehearsal', the latter scheduled for the end of January 2026.

One key aspect is the loading of fuel. NASA engineers will be inspecting the loading of liquid hydrogen and liquid oxygen into the rocket.

Artemis I's wet dress rehearsal was postponed, for example, as a result of difficulties that occurred during liquid hydrogen loading.

And, NASA says, the ground team will measure how much gaseous nitrogen accumulates in the space between the Orion crew module – the spacecraft where the astronauts will be – and the launch abort system hatches, as this could pose a safety issue for the ground crew.

The 'closeout crew', who are responsible for securing the astronauts into the Orion capsule, will use the rehearsal to practise procedures without the astronauts on board.

If any issues arise with the wet dress rehearsal, NASA may need to postpone or arrange further dress rehearsals to make sure everything is ready for launch day.

Then there's the 'rollout' of the Space Launch System rocket and the Orion module, scheduled for Saturday 17 January 2026.

This is the procedure of rolling the rocket and capsule out of NASA's Vehicle Assembly Building, ready for launch.

But the assembly may need to be rolled back in, if engineers feel extra work needs to be done prior to launch.

"Following a successful wet dress rehearsal, NASA will convene a flight readiness review where the mission management team will assess the readiness of all systems, including flight hardware, infrastructure, and launch, flight, and recovery teams before committing to a launch date," the agency says.

Determining the launch date

Once NASA is happy with the rocket, module and ground teams, and that the dress rehearsals have shown all is ready for launch, the agency needs to decide when Artemis II's lift-off date will be.

The launch window opens on 6 February 2026, but NASA has listed further potential launch dates up to 6 April 2026, so we could be waiting months for the final launch of the mission.

There are multiple things to take into account, a large one being the fact that the Earth and the Moon aren't stationary bodies in space.

Earth is orbiting the Sun, and the Moon is orbiting Earth. To make things even more complicated, Earth and the Moon are both spinning.

That's why the launch dates come in batches throughout one week, followed by about three weeks without launch dates.

Then there's the weather to take into account. Artemis I, for example, faced multiple delays, including as a result of tropical storms that would have made planned launch dates unsafe.

Here are the key factors that determine the Artemis II potential launch dates.

Getting the Earth orbit right

The date and time of the Artemis II launch needs to enable the Space Launch System – the rocket – to deliver Orion – the capsule keeping the astronauts safe – to a high Earth orbit.

That's because the astronauts won't simply launch from Earth in a straight line to the Moon.

Artemis II will launch into a low-Earth-orbit, before shifting to a second high-Earth-orbit.

At this point, teams on the ground will check everything's in order, before giving the go-ahead for the crew's onward journey to the Moon.

Making a move for the Moon

The 'trans-lunar injection' is the name given to the final manoeuvre – the final 'push' – that will allow the Orion capsule to break free of its Earth orbit and head towards the Moon.

This will set Artemis II on a 'free return trajectory', in which the spacecraft uses the Moon's gravity to 'slingshot' around the Moon, expending only tiny amounts of fuel for minor engine burns to finesse its trajectory where required.

In order for this to be possible, the Earth-Moon alignment needs to be just right on launch day.

Orion needs sunlight

It's not just Earth and the Moon that flight engineers need to consider. They've also got to consider where the Sun is, too.

The Orion capsule's European-built service module has four solar panel wings to provide power.

Each of these wings is 2m x 7m, and each solar panel is about 2m x 2m in area.

NASA says the wings' combined panels could provide enough electricty to power two three-bedroom homes.

As a result, the Orion capsule needs sunlight, and can't be in darkness for more than 90 minutes at a time.

Mission planners therefore select launch dates that mean Orion won't effectively experience a solar eclipse during the flight, where the Moon is blocking sunlight from reaching its solar panels.

The astronauts need to get home

Finally, the Artemis II launch date must be able to put the astronauts on a trajectory to and around the Moon, bringing them home safely and allowing for a successful re-entry into Earth's atmosphere, ready for splashdown in the Pacific Ocean at the mission's end.

Are you excited for the launch of Artemis II? Let us know your thoughts on the mission by emailing us at contactus@skyanightmagazine.com