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Paul Allen's Stratolaunch Finally Flies The World's Biggest Plane (geekwire.com)
"Stratolaunch, the aerospace venture founded by the late Microsoft co-founder Paul Allen, sent the world's biggest airplane into the air today for its first flight test," report GeekWire.
The twin-fuselage plane, which incorporates parts from two Boeing 747 jumbo jets and has a world-record wingspan of 385 feet, took off from Mojave Air and Space Port in California for a flight that lasted two and a half hours. For more than seven years, Stratolaunch has been working with Mojave-based Scaled Composites on the project, which aims to use the plane as a flying launch pad for orbital-class rockets. The first flight test had been anticipated for months. "We finally did it," Stratolaunch CEO Jean Floyd said today during a briefing.
Stratolaunch's plane, which has been nicknamed Roc after a giant mythical bird, took off at 6:58 a.m. PT and went through a series of in-flight maneuvers, including roll doublets, yawing maneuvers, pushovers and pull-ups, steady heading side slips and simulated landing approach exercises. Stratolaunch said it reached a maximum speed of 189 mph and maximum altitude of 17,000 feet.... The plan ahead calls for further tests over the next 12 to 18 months, with the aim of getting the plane fully certified by the Federal Aviation Administration. Stratolaunch has already struck a deal to use Northrop Grumman's Pegasus XL rocket to send payloads weighing as much as 816 pounds (370 kilograms) to low Earth orbit...
Stratolaunch's air-launch system is designed to carry multiple rockets up to an altitude of about 40,000 feet, and then drop them into the air to fire up their rocket engines. The advantage of such a system is that it can take off from any runway that's long enough to accommodate the plane, fly around bad weather if need be, and launch a satellite into any orbital inclination.
Stratolaunch CEO Jean Floyd said their team had dedicated the flight to Paul Allen.
"[A]s the plane lifted gracefully from the runway, I did whisper a 'thank you' to Paul for allowing me to be part of this remarkable achievement."
Stratolaunch's plane, which has been nicknamed Roc after a giant mythical bird, took off at 6:58 a.m. PT and went through a series of in-flight maneuvers, including roll doublets, yawing maneuvers, pushovers and pull-ups, steady heading side slips and simulated landing approach exercises. Stratolaunch said it reached a maximum speed of 189 mph and maximum altitude of 17,000 feet.... The plan ahead calls for further tests over the next 12 to 18 months, with the aim of getting the plane fully certified by the Federal Aviation Administration. Stratolaunch has already struck a deal to use Northrop Grumman's Pegasus XL rocket to send payloads weighing as much as 816 pounds (370 kilograms) to low Earth orbit...
Stratolaunch's air-launch system is designed to carry multiple rockets up to an altitude of about 40,000 feet, and then drop them into the air to fire up their rocket engines. The advantage of such a system is that it can take off from any runway that's long enough to accommodate the plane, fly around bad weather if need be, and launch a satellite into any orbital inclination.
Stratolaunch CEO Jean Floyd said their team had dedicated the flight to Paul Allen.
"[A]s the plane lifted gracefully from the runway, I did whisper a 'thank you' to Paul for allowing me to be part of this remarkable achievement."
Launching rockets from airplanes has been done before but the plan with Stratolaunch is to do so on a larger scale with functionally a bigger rocket. There are some advantages and some disadvantages. One major disadvantage is that there's functionally a size limit: one cannot really put that large a rocket on a plane (and the fact that to get this to work they need to use what is by multiple metrics the largest airplane ever reflects that).
The plane is functioning to some extent like a reusable first stage, but a plane isn't likely to go as high or as fast as as a true first stage, like the Falcon 9's first stage, so it isn't the same as having a true reusable first stage in terms of power.
At the same time, a plane is a well understood, reliable technology. Another connected advantage of air launch is that one is much less beholden to weather events. since the plane can fly above or around bad weather. The Falcon 9 in contrast frequently needs to be delayed due to weather issues (which are made worse in its case because it is a very long and thin rocket); one does have things like the Soyuz which is able to launch in functionally blizzard conditions, but that's pretty rare for a rocket and is in a large part due to the fact that it was originally designed to be an ICBM.
This is a spectacular piece of aerospace engineering, basically a huge flying wing built to lift several hundred ton boosters.
The recent SpaceX Falcon 9 Heavy launch with full booster recovery destroys the economic advantage of air launch.
SpaceX's success indicates that launching can become a refuel and repeat process, so there is no need for a hugely expensive aircraft launch vehicle. Especially as that aircraft has limited speed and range and requires an enormous runway to operate from, which undercuts the idea that it can launch to any azimuth from anywhere.
From a business perspective, the operation was successful, but the patient died. Sad.
The biggest advantage is lower air pressure. Rocket engines must keep the pressure of the exhaust gas higher than the atmosphere the launch in. This means the engines at sea level launch will have a lower exhaust speed and therefore be less efficient.
Next you don't have to push through 40,000 feet of atmosphere. Rockets launched from sea level do not accelerate at their maximum rate because they want to reduce loss due to air resistance.
Third is flexibility of launch location. You can now launch from anywhere your plane can get to. Launching from the equator to geostationary orbit is easier than going form south Florida.
Last you start a little higher and with an initial velocity. This is probably the least advantage but it still counts. Rockets are all about change in velocity and its an exponential equation. Want to go an extra 1500m/s double the size of your rocket. So a little initial altitude and velocity can mean a huge difference in the amount of fuel needed to reach your intended orbit.
The real problem is that Stratolaunh was designed with a much larger SpaceX rocket in mind that got cancelled. So the 3x Pegasus is a fallback plan.
Considering how rarely Pegasus launches (43 launches in 29 years), it doesn't seem like a wining proposition.
Stratolaunch can probably fly higher than the L1011, which would give Pegasus new mission options it did not have before.
The Pegasus L1011 is the last L1011 flying in the world, so it would be a shame to see it be retired, but I suppose that is the lifecycle of aircraft.
I'm a good cook. I'm a fantastic eater. - Steven Brust
The original plan was to sling huge rockets in the middle, but the rockets are cancelled and so they're only launching the tiny Pegasus rockets now
the energy of 2.2lb (1kg) of payload at launch is approximately 275 kJ but to
Sorry, but you are doing the wrong maths. Rockets are not like cars, the important metric is delta-V, not energy.
Calculating kinetic energy to achieve orbit is a rookie error. - unless you happen to have a giant rail gun or space elevator.
This is why rocket "power" is always quoted in Newtons, not Watts.
Take a look at the Rocket Equation: https://en.wikipedia.org/wiki/...
The maths is just simple algebra, no calculus needed - have fun!
Neither "energy" nor delta-V ( velocity/momentum) are the reason for air launch though.
It avoids problems of getting through the low, dense atmosphere, and you can have a more efficient rocket if it only has to operate in thinner air.
But Elon Musk stated that the total benefit amounted to 5% payload increase, so they scrapped the idea. Its easier to just build a 5% bigger rocket.