I'm reliving my childhood watching cartoons from the 60s and 70s on Saturday mornings. While I never got into Thunderbirds, I was a big-time fan of Fireball XL-5 and Stingray. I even had a few Fireball XL-5 toys. :-)
But it seems I got these episodes out of order and just realized this was the last episode. It seems like they weren't even trying anymore. Junk science is junk science, but even for a kids' show, this is the most ridiculously stupid junk science I've seen in a long, long time. LOL
A magnetic planet has the highest gravity in the GALAXY, and it's being used to pull the moon away from the Earth. LOL They know there's a problem when the moon is 10 minutes late rising??!! Fireball XL-5 is pulled to the magnetic planet but their flying cycles don't get stuck to it. LOL Steve solves the whole problem by spraying a gun around at invisible aliens ... evidently because they didn't want to bother with one or more new marionettes for the last show.
Of course, Gerry DID somehow let the moon idea stick in his mind, because he made a moving moon the absurd premise for his live action Space 1999 ... as boring a show as I've ever seen.