hyperloop was very low air pressure subway tubes for high speed trains. Works for research tesring tracks impractical to infeasible for real world applications. But it apparently what killed high speed rail in california (because wait this will be better)

The cars in tubes thing was a seperate stupid idea.

okular supports signing. But you have to set up your signing certificate outside it and then point it at the certificate database in the backend settings. Creating a signing certificate in adobe, saving that to a file, registering that file with nsdb, setting nsdb as backend in okular, works. Only have to do the setup obcr, then just works.

also when they see this post