The friend should play Kerbal Space Program. It will be a fun way to show that yes, it’s really hard, but it is possible to play around with orbital mechanics and get to the moon.
And then it will show that an unsteerable rocket with infinite fuel and a chair strapped to it is also possible, just really really hard.
I imagine the latter isn’t too hard, you just have to get it right just before leaving the atmosphere (quick saves help); however, isn’t landing (not crashing nor rolling around) on the Mün without steering straight up impossible?
Though I can see some rocket landing on a planet with an atmosphere…
… so, when are we launching?
On a serious note, I think I was wrong.
Assuming you can get into Mün’s SOI with an incredibly precise trajectory, you can MAYBE, sort of, lose kinetic energy by simply burning “upwards” at certain points, until you’re basically repeatedly going upwards then downwards relatively to the Mün. Its rotation is a problem, but tbh I haven’t played KSP in years and ffs I’m studying IT, not… whatever KSP is.
