Sorry, if you "walk up on a circle" you can't guess at a diameter either. You have to make a geometric construct to find the center so your diameter measurement is correct. You might as well measure the radius at that point.

"Emerging Technologies May Fuel Revolutionary Launcher"

It looks more like the rail truck accelerates the launch vehicle to mach 1 which leaves the end of the track and the scramjet lights and carries it and its payload to mach 10 at about 20 miles altitude. The payload then separates from the launcher, the rocket ignites and sends the payload into orbit. The launch vehicle returns and lands for reuse.

This sounds a lot more feasible than a mach 10 rail gun!

I liked the internet so much better when the prudes were scared of it.
Let's return now to those thrilling days of yesteryear!

I read it as, "Robots attack men with virtual girlfriends."

I thought, jealous robots?!