Strap a rocket to the underside of a plane. Fly it up several miles. Drop it. The engine ignites, and the rocket and its payload zoom to space.
That is what Virgin Orbit, one of the multitude of companies started by Richard Branson, plans to do Sunday or Monday. It is a demonstration of a new rocket system for sending small payloads to orbit.
When is the launch?
Virgin Orbit, based in Long Beach, Calif., announced two potential windows for the launch on Sunday and Monday. Early on Sunday, the company announced on Twitter that the day’s attempt was being called off.
“If at any point we see an issue or an anomaly that we need time to understand, we’re going to take that time,” Dan Hart, chief executive and president of Virgin Orbit, said in a telephone news conference on Saturday. “And so there is certainly a significant likelihood that we don’t get through countdown on our first pass.”
Mr. Hart said the weather on Monday looked favorable for the test.
How does the launch work?
A modified 747 named Cosmic Girl will carry the rocket, LauncherOne, under its left wing. (Virgin Orbit is taking advantage of a design quirk of the 747: a pylon used to ferry an extra engine.)
Taking off from Mojave Air and Space Port, the plane will head west over the Pacific Ocean and will then turn south. At an altitude a bit below 35,000 feet, or about 6.5 miles up, Cosmic Girl will fly upward at an angle and drop LauncherOne. A few seconds later, the booster stage of the rocket will ignite, and the rocket will then arc upward into the sky.
The jet’s 6.5-mile head start off the ground is not that much of a help, because it not does not have much upward velocity. The rocket still needs to accelerate to a speed of 18,000 miles per hour to achieve a stable orbit around Earth.
If all works, a small test payload will end up in orbit. But Will Pomerantz, vice president of special projects at Virgin Orbit, noted that about half of maiden flights do not succeed. To avoid adding to the debris around Earth, the payload will be placed in a low orbit and will fall back into the atmosphere, where it will burn up.
Even if the flight is not entirely successful, the data gathered would be useful. The ignition of the rocket engine — the first time it will have been done in flight and not on a test stand on the ground — is “the key moment in this flight,” Mr. Pomerantz said. “We’ll keep going as long as we can after that, potentially even all the way to orbit.”
Why launch a rocket from an airplane?
An airplane is essentially a mobile launchpad, enabling rocket launches from many more locations. If there is a thunderstorm, the jet can fly around or over it. And flying over the ocean immediately reduces the risk to people below if the rocket explodes.
“What that gives us is incredible flexibility,” Mr. Hart said. “In fact, we have mobility. We can fly to space from any place which can host a 747. Which is almost any place.”
How much can LauncherOne launch?
The two-stage rocket can lift up to 1,100 pounds — Mr. Pomerantz said a typical payload would be about 650 pounds — to low Earth orbit. Only smaller satellites can fit within the rocket’s four-foot-wide payload section. The cost is fairly low, however: about $12 million.
Mr. Hart said the company had orders for launches that added up to hundreds of millions of dollars.
LauncherOne is one of a slew of small rockets under development by many companies to carry smaller satellites to low Earth orbit. With advances in computer chips and miniaturization, powerful satellites can now be much smaller than in the past. Competitors include Rocket Lab, which has successfully launched its rockets from New Zealand and has set up a second launchpad in Wallops Island, Va.
While Virgin Orbit would be slower than Rocket Lab in getting a payload to orbit, it would be ahead of the other emerging competitors.
Astra, another start-up building a small rocket, was poised to win at least part of a $12 million prize from the Defense Advanced Research Projects Agency. But while the rocket was fueled on a launchpad in March, the launch attempt was called off because of technical problems. Astra has not made another launch attempt since then.
While many industry observers expect only a few companies to win enough business to survive, “I don’t see it as very packed,” said Mr. Hart, who expressed optimism that the emerging market will be larger than many expect.
Another of Mr. Branson’s companies, Virgin Galactic, is using the same concept on a larger rocket plane called SpaceShipTwo, to take paying passengers on up-and-down trips where they can experience a few minutes of weightlessness and view Earth from the blackness of space.
Virgin Galactic, which has now become a publicly traded company, is separate from Virgin Orbit.
Orbital Sciences, now part of Northrop Grumman, developed a similar air-launched rocket called Pegasus, which first flew in 1990. Most recently, it launched a NASA satellite, the Ionospheric Connection Explorer, to orbit in October. But in recent years, Northrop Grumman has found few customers interested in Pegasus, which costs several times more than LauncherOne