Stratolaunch is a behemoth airplane, featuring a wingspan longer than a typical American football field. It is currently the world's biggest airplane, and it just had a successful runway taxi test on Feb. 25.

It weighs over 500,000 pounds. It's so big that it needs two fuselages — the main body of an aircraft — and two separate cockpits. It's being designed to launch rockets into low-Earth orbit.

Stratolaunch To Debut In 2019

The plane has undergone a bevy of tests since its unveiling in June last year, and it's scheduled to debut in 2019. The most recent runway tests saw the aircraft reach top speeds of 46 mph with all flight surfaces in place, according to Microsoft cofounder Paul Allen, also founder and chairman of Stratolaunch.

Suppose it successfully flies in 2019, it will be the largest airplane to ever lift off, a record currently held by Hughes H-4 Spruce Goose. Stratolaunch has a maximum takeoff weight of 590 metric tons, significantly surpassing the capacity of commercial airlines.

Launching Rockets

The company hopes that launching rockets from the plane could be a less expensive method than space launch options currently available. That sounds tremendously ambitious, but space entrepreneur Gary Hudson believes it could be successful, in part because Allen is, well, rich.

"If they choose wisely, they could provide crew and light cargo services to [low-Earth orbit] for considerably less than current prices," said Hudson. "If they don't, they will become a footnote to astronautical history for having built the world's largest plane." If the plane doesn't amount to anything useful, he added, it would become another case of the aforementioned Spruce Goose airplane, which flew only once.

Launching from high altitude has key advantages over ground-based space launches, said Hudson. For starters, rocket engines perform better in reduced atmospheric drag and low pressure in such altitudes. Plus, whereas a grounded rocket might wait up to a week to coincide with a spacecraft or space station passing by overhead, an airplane can go to an optimal launch point anytime from any runway that's large enough, according to Hudson.

But the huge drawback is payload capacity. Typically, a spacecraft only is as 1 or 2 percent heavy as the rocket launching it. That means if Stratolaunch is able to carry only 550,000 pounds, its payload will be somewhere between 5,000 to 10,000 pounds. That's a huge number, but not enough to compete with, say, SpaceX's Falcon Heavy.

Below is a video of Stratolaunch's taxi runway test. If you have any thoughts about the project, including the planned 2019 debut, sound them off in the comments section below!

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