Subselene: Lunar nuclear powered melt-tunneling for high-speed transit tunnels (osti.gov)

This was published in 1986.

Tunneling with nuclear machines on Earth had been under consideration for decades before [1]. It's not entirely clear why it was abandoned, but most likely something didn't work out in practice like it was supposed to do in theory.

[1] https://nationalinterest.org/blog/buzz/americas-mad-scientis...

i posted Subselene (1986) because the earlier 1973 proposal to do similar on earth (Subterrene) was also submitted recently,

https://news.ycombinator.com/item?id=28559927