I read a book (or possibly a series of books) in the UK, probably in the late 80s, that’s stuck with me ever since, and I’d love to know if anyone can identify it.
The basic story revolved around a group of kids (3-4?) that had been put in a (British?) boarding school by their parents while they went off to do something (mining?) in space. The kids somehow managed to piece together a spaceship and blast off to find them.
I’m remembering the spaceship as being an asteroid hollowed out in a spiral shape like a nautilus shell. It had a rocket at the center on one side. There may have been a pictorial diagram in the book too.
Beyond that, I don’t remember much of the rest of the story, although there was definitely a point at which they find an empty ship. There’d been some sort of nuclear accident on it; someone had written “THTH” on the wall, which turned out to mean “too hot to handle”.
Anyone got any ideas?