Sounds likes shades of Eskimo’s descriptions of snow... Plagiarism? ;-)
I have yet to compile a "definitive" list.
They call it "Launch to Space with an Electromagnetic Railgun". I call it a nice first step.
In the document, concern is expressed about safety downrange, noise, durability of the "launch tube", and other matters.
I can help them out. As you may recall, I want to build such a facility in Antarctica. No problems downrange, no complaints about noise. Plenty of room to spread out the launch facility.
We could probably take advantage of the current equivalent of Pikrete, or Pykrete. Maybe reinforced with carbon fiber and other essentials. This eminently practical construction material could be used not only for portions of the orbital vessel, but also for the launch tube as well.
Imagine a four-pole metal/plasma induction railgun, supplemented with magnetic control coils to help keep the craft centered and steady.
Build the launch tube inside an appropriately positioned stable glacier, with the walls strengthened with our formulated Pykrete, and the control rails embedded in the cylindrical walls. Presto! One freight train launched into orbit!
Each launch would probably use up about a million dollars worth of electricity, so I'm not sure how feasible my plan to irrigate the deserts with suborbital snowball tossing would work. The water might be a little pricey.
Still, it is a way to at least utilize the facility, as opposed to amortizing it. And it does allow one to "ramp up" the engineering on the way to being able to launch massive amounts of mass into orbit for a fraction of the current cost (pun unavoidable).