I just did a search, and only found my earlier HN account of reading the USENET post from someone working at JPL. Yes, you can discount such towers as fanciful nonsense. Physically possible, but politically and economically infeasible as of now. Another rec.arts.sf.science post described how our civilization could sterilize the biosphere, but it would involve global civilization spending decades doing nothing but seeding the surface with nukes, just to set them all off simultaneously. A number of prominent scientists used to post there with wild back of the envelope calcs. Someone working at JPL did write up a proposal to build an exponential truss tower using hyper pressurized balloon tanks made from boron. I'm sure of this. In any case, it's interesting only as an intellectual exercise.