But First Flight For The Enormous Airplane Not Likely Until 2018

The Mojave Desert has been echoing with the sound of jet engines as Paul Allen's Stratolaunch has been testing the engines for the largest airplane by wingspan to ever be rolled out of a hangar.

Stratolaunch is designed to carry rockets with satellite payloads into the upper atmosphere, where they will be released and launched into low earth orbit. It's a concept called horizontal launch, and eliminates the need to use an expendable or recoverable rocket for the initial boost into space. That makes the rockets lighter, more efficient, and less expensive.
 
Others are planning similar launch services. Perhaps best known among them is Sir Richard Branson's Virgin Orbit, which is working on a scheme to use a Boeing 747 for a horizontal launch platform. But Branson will only be able to push a payload of about 660 pounds into space. Stratolaunch will carry a rocket large enough to deliver over 13,000 pounds into orbit.
 
The Stratolaunch system has a lot in common with Virgin Orbit's 747 platform. Its engines were pulled from two United Airlines jumbo jets, and a 747 also contributed all of the landing gear as well as parts of the wing. It is similar in design to Virgin Galactic's WhiteKnightTwo, which Branson hopes will soon be launching SpaceShipTwo with paying tourists aboard on suborbital flights. That's because both aircraft were designed by Scaled Composites.
 
The project is well behind schedule, according to a report from The Daily Beast online, which reports that by Christmas, Stratolaunch may be "within weeks" of flying for the first time.

(Image from file)

FMI: Original Report