(CNN) - Virgin Galactic, Richard Branson's space tourism startup, will attempt Thursday to send its rocket-powered plane closer to space than it's ever been.
The company has conducted three test flights over the past eight months that have pushed its supersonic plane progressively higher. On its fourth test flight, scheduled for Thursday, Virgin Galactic will attempt to blow past its previous record of 32.3 miles — and potentially reach the 50-mile mark, an altitude that the US government used to award astronaut wings and some consider to mark the edge of space.
"Overall the goal of this flight is to fly higher and faster than previous flights," the company said in a blog post. "We plan to burn the rocket motor for longer than we ever have in flight before."
The mission will aim to more closely match the flight profile that Virgin Galactic plans to use for commercial missions. Soon, Virgin expects to take paying customers to the edge of space. A smooth flight Thursday could put the company closer to becoming the world's first operational space tourism business. It's a feat Virgin has worked toward for 14 years.
Rather than aiming for space using a NASA-esque vertically launched rocket, Virgin Galactic uses a rocket-powered space plane dubbed VSS Unity, a craft more comparable to the supersonic X planes developed by the US military.
At launch time, VSS Unity will take off from a Mojave runway attached to its mothership, WhiteKnightTwo. Then, about 43,000 feet in the air, VSS Unity's pilots will command the plane's release. After a few seconds of coasting, VSS Unity's rocket engine will roar to life and drive the vehicle directly upward at supersonic speeds.
If the pilots notice any abnormalities, they have the option to cut the engine burn short.
"This is test flight. You are going to be watching a no-kidding test flight with all of the novelty and excitement and risk that goes along with a real test flight," Virgin Galactic CEO George Whitesides told reporters Wednesday. "We're obviously hoping for a good day tomorrow but the risk of a not good day is still possible."
Ideally, if all goes as planned Thursday, VSS Unity will soar to a peak altitude of just about 50 miles and the pilots will experience a few minutes of weightlessness. Also on board will be a flight test dummy and four unnamed research payloads from NASA's Flight Opportunities Program that will help simulate the weight distribution of having passengers on board.
As VSS Unity falls back toward Earth, it will fan out a large tail, called a feather, that will orient the plane as it cuts back through the Earth's atmosphere. It will then glide back toward Mojave for a runway landing.
Virgin Galactic has not said when it plans to begin commercial flights.
"Incremental flight test programs are by definition open-ended and, to a great extent, each test depends on the data from the test that precedes it," the company said. "There is no guarantee that everything will work perfectly first time and, like all programs seeking to take bold steps, we will inevitably have times when things don't go as planned."
Commercializing space travel
Branson's space venture suffered a major setback in 2014 when its first space plane, VSS Enterprise, broke apart during a test flight, killing co-pilot Michael Alsbury and injuring pilot Peter Siebold.
The tragedy spurred critics of space tourism who have deemed such projects irresponsibly risky. But Virgin Galactic bounced back.
The company is squared up to compete directly with Blue Origin, the space company founded by Amazon billionaire Jeff Bezos in 2000 to offer suborbital tourism flights.
Both companies are still in the testing phase. And Blue Origin — which plans to fly tourists on an automated, vertically launched rocket — has yet to conduct a crewed flight or begin selling tickets.
Virgin Galactic says about 600 people have reserved tickets, priced between $200,000 and $250,000, to ride aboard its supersonic plane. Some have waited over a decade for their shot.
When asked about Virgin Galactic's competitors in a recent interview with CNN Business, Branson said it was not a "race."
"Safety's all that matters if you're putting people into space," he said.
Branson, who plans to be on the first passenger trip aboard VSS Unity, has said he hoped Virgin Galactic's pilots would reach space before December 25.
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