To orbit the moon, a space craft needs to move at about 1.5 km/s, or 3300 miles per hour.

So any landing starts with you going at 1.5 km/s and needs to end at the moons surface when you reach about 0 meters per second.

If anything goes wrong with your engines while you slow down, you smack into the moon at either near orbital speeds, or at fighter jet speeds. The window for having an engine failure and being slow enough to survive is so narrow that it might as well not exist.

That’s why Apollo used pressure fed, self igniting engines. As long as 2 valves opened, you had an engine. And Apollo landers had a totally separate ascent engine that worked exactly the same way, so if the landing engine failed, they could just drop the landing stage and return to orbit at practically any time during the descent. They even had a whole procedure of what to do if the ascent engine didn’t light when they were supposed to leave. Everything from jump starting the engine like a car with a dead battery, to physically getting access to the valves and manually opening them.

I hate the current plan for Artemis. I hate that in 55 years, we’ve only managed to make shit more complicated. The current plan is for a vehicle with no abort capability to ignite its 3 turbo pumped, liquid methane fueled engines at least 4 times to get from low earth orbit to the moons surface, with days between ignitions.

A capability that has never been shown to work or even exist in any capacity. Turbo pumps are finally machined pieces of engineering that need to behave exactly right, or they turn a rocket into either a bomb, or a giant tube that can’t move. And the current plan for Artemis calls for these finely crafted pieces of machinery to be subjected to the harsh environment of both space where they’ll sit for at least a week, and multiple ignitions, where they’re subjected to ridiculous temperatures and pressures.

Absolutely ridiculous. We never left an astronaut on the moon in the 60s and 70s, but by god are they trying to open the first graveyard on the moon these days.