scramjets

Though NASA has built small, high-speed aircraft called scramjets that can travel at speeds up to Mach 10, this engine technology is not ready for commercial aviation.

The Daily Princetonian, 2009-06-03 2008

Professor John Fielding, Head of Aerospace at Cranfield University said that the prohibitive cost of scramjets would be a ‘major issue’ before any commercial design could be developed.

Experimental ‘Scramjet’ Sets Hypersonic Speed Record | Impact Lab 2010

Once the Air Force guys prove that hypersonics can be done with flights that last minutes (like X-51), not seconds (like X-43), then the hope is that the floodgates will open and scramjets won't be seen as just engineer's pipedreams by the guys who hold the purse strings.

X-51 Waverider Set to Fly This Fall - NASA Watch 2009

Considering how far the work on scramjets has gotten the main sticking point is a turbojet with the capacity to accelerate the craft to high mach 3 speed at which juncture the ramjet would take over and the turbojet would be hidden in an enclosure.

X-51 Waverider Set to Fly This Fall - NASA Watch 2009

British scientists have worked on designs for scramjets but do not expect one to be available for commercial flights until at least 2020.

Experimental ‘Scramjet’ Sets Hypersonic Speed Record | Impact Lab 2010

It seems to me NASA has an incredibly long list of things they'd _like_ to do from scramjets to men on Callisto.

NASA Presidental Transition Action Item Log - NASA Watch 2008

SHARP was originally designed as a testbed for hypersonic engines for scramjets – jets that are accelerated to high speeds, then use a specialized engine of their own to push up to 8 or 9 times the speed of sound.

Hydrogen Gas Cannons Could Launch Payloads to Orbit (w/video) | Universe Today 2010

A big problem with scramjets, though, is that you have to get them going three times faster than the speed of sound just to start them up.

Space Plane 2007

(You've also got one hot engine -- keeping scramjets from melting is another big engineering challenge.)

Space Plane 2007

You can run me with training wheels or scramjets, but it's me both times.

The Year's Best Science Fiction 23rd Annual Collection Dozois, Gardner 2006