A long winter has a way of making a lot of us northerners a little bit squirrly. In [Build N Pulsejets]’s case, squirly enough to mount a home-made propane-powered pulse-jet to a kids’ kick scooter ...

A nuked‑pulse rocket, by contrast, trades that extreme lightness for a much heavier, shielded vehicle that might “only” reach perhaps 10 percent of light speed, stretching the cruise time to around 44 ...