...The WaveRider — which is small, wingless, and resembles a shark — uses a special "scramjet" engine — shorthand for "supersonic combustion ramjet," says Daniel Lametti at Slate — to reach speeds of up to 4,500 mph. A standard Boeing 787, for example, tops out at 647 mph. The jet works by gobbling fast-moving air into an engine, where it mixes with fuel and is then ignited to produce thrust. Ordinary planes, on the other hand, require the help of turbines to achieve the same effect. As a result, the scramjet is able to reach "dazzling speeds" with no moving parts...
[The downsides?] For starters the jet can't start from a standstill, and therefore needs to be dropped from another plane to become airborne. "Since forward motion is what pushes air into the engine, the plane must be brought up to speed before ignition," says Slate's Lametti. That also means the WaveRider is incredibly difficult to start up: One military report likens producing thrust on the scramjet to "lighting a match in a hurricane and keeping it burning."
Okay, I'll ask the obvious question: why can't it be equipped with a traditional jet engine to get to sufficient speed on its own?
* According to Joe Biden.
Hat tip: BadBlue News Service.