Kevin Nolan

that the Moon captured them and they were in orbit very close, just probably a couple of hundred kilometres above the surface.

And that's why they needed fuel to break away from the Moon and get back to Earth.

But this time, that's why they didn't go so close.

They stayed about 4,000 kilometres.

So all they did was put themselves into a lunar or an Earth orbit, I should say.

But it so happens then that the Moon caught them and then kind of threw them around itself until they come back to the Earth.

So it's a beautiful elegance of use of gravity.

Isn't it?

Yeah.

By the way, we've used this for a long time.

Like the Voyager spacecraft out to the outer solar system, like we slingshotted Voyager around Jupiter, Saturn and Uranus out to Neptune.

So, and they gained speed even in that regard.

And even when we sent, for example, Horizons, New Horizons to Pluto, it would have taken 15 years to get there, but we slingshotted around Jupiter and reduced that to nine years.

So we're very good at this.

There's little what?

Oh, well, there's literally no engines at all.

I mean, they did have a little bit of booster just to correct the actual trajectory.

In fact, what I haven't been able to quite find out is, say they had had an accident on an Apollo 13 level, would they have had enough fuel to really correct the orbit?

I suspect not.

And that, I think, was the risk with this stuff and why they would.