Unique airplane designed to replace first stage of ground-launched rockets. Paul Allen showed off his new rocket-launching plane today, and it’s BIG | Ars Technica One might say several things about this but for me, it shows how absurdly strong carbon-fiber structures can be. Those are three of the biggest turbofans available on each wing. In the center would hang the rocket (deadweight) comprising a large fraction of 250-ton payload. However, during takeoff when that deadweight gets dragged upward, and at 'drop' (when the airplane gets suddenly lighter), the whole thing does not break in the middle.
push over to build speed smooth pull up to increase attitude, speed decays push over to low or zero G and release rocket pull and turn right, rocket maintains attitude with cold thrusters after clearance, rocket ignites Reference: Toss bombing - Wikipedia Bob Wilson
According to past local news articles (Allen, Vulcan, and a lot of aerospace activities are homed here), numerous components of this aircraft are not fresh designs, but are simply systems taken from used B747s. Engines, landing gear, cockpits, flight deck, etc. Just looking at it, the center wing span must be exceedingly strong and stiff compared to normal aircraft. The fully loaded craft will have more separate and widely spaced body and payload masses than normal craft. These will bounce around in stronger and more complex vibration / shake modes when the vessel gets thrown around in turbulence. Also, with its comparatively heavy payload fraction and light fuel load fraction, an in-flight launch abort means having some extremely heavy landing weights. Normal airliners can dump a lot of fuel to get down to safe landing weight, but I suspect launch customers wouldn't be happy about dumping an entire payload when an indicator light shows a common anomaly prior to rocket release-ignition. Maybe liquid fueled rockets can dump their fuel, such as in the original plan for a modified Centaur booster that was supposed to launch the Galileo probe from the Space Shuttle on its way to Jupiter. A problem there was that a 10 minute normal fuel burn would need to be dumped from the Shuttle wingtips in 60 seconds during a shuttle inflight launch abort with emergency return. That plan was scrapped after the Challenger disaster, and Galileo had to move to a less energetic unmanned launch vehicle. (This actually had some connection to ground test equipment I was working on at that time.) Solid fuel rockets can't dump their fuel loads.
I cannot imagine that Stratolaunch could land with a big firestick still under the belly. Am I wrong? 747s and 380s take off with similarly heavy bellies. But engine thrust is connected thereto through whacking big/strong wing boxes. Here there will be a sliver of carbon fiber, relatively speaking. That is the amazing part. ++ Yes recycling 747 hardware kept development costs low. Great that anyone can buy that hdw 'cheaply' now if they want to put something big in the air.
First thought upon seeing a photo, "It's a giant Lightening." Impressive that it doesn't need additional bracing between the two bodies. Another though is why haven't flying wing designs been adopted for commercial uses.
That is what I'd like to know. I'm not imaging it either. For take off, yes. Landing, no. An A380 datasheet shows a max takeoff weight of 640000 pounds above its empty weight. But the max landing weight is a mere 252000 pounds above empty. Corresponding figures for a certain 747-400 are 472000 and 249000 pounds, respectively.
Yes big difference. When upgoing the 'unloading dynamic; of landing gear is within benign limits (if I may say so). When downgoing, it can vary a lot depending on circumstances.
This does sound like a very sensible approach. But a British person would make wildly different assumptions about what you were doing if you were to mention "toss bombing". Once again, divided by a common language.
Odious paperclip@9. Perhaps it does not need to be said that Paul Allen only signs the cheques*. Real aerospace engineers design the gadget. *pandering
We (wrongly) think of the ground, where the body holds up the wings, but in the air, the wing holds up the body.
Yes. One would hope that the pilots won't find that they have to switch the plane off and switch it back on again. Perfect English. Thank you.
Ya, the wheel trucks are on paired fuselages, what, 25 meters apart? Center of lift points (and thrust points for engines) may be 50 meters apart. Connected by a sliver of carbon fiber.
Isn't this a crucial issue when it comes to what @tochatihu , @fuzzy1 and @Trollbait are discussing? I'd assume that the bodies are extremely light. Other than the space rocket itself, the weight is going to be pretty much all fuel, and it looks like a lot of that could be going in the wing/crossbeam. So before launch, weight would still be concentrated in the middle, where it would be on a normal plane. Or am I wrong? I have been known to be.
Paul isn't to blame for that, he retired due to illness (non-Hodgkin's lymphoma, a cancer), long before Clippy or Bob happened. I seem to remember Melinda having greater connection to that. At least to Bob, a predecessor of Clippy. All this stuff is crucial. When it lands, there is a lot of shock loading, and heavy masses hanging out on long cantilever arms far from the landing gear. In the air, all those masses at opposite ends of tube connections cause a lot of wild flexing modes and high bending stress when the vessel is hit with turbulence. With a regular plane, all the payload and a good fraction of the craft mass is inside a single large cylinder, a fairly efficient mechanical shape. But for the Stratolaunch, the payload is outside, and two heavy fuselage/wing/tail structures are connected by a much skinnier 'flattened cylinder' (a.k.a center wing span), less mechanically efficient than a normal fuselage. Bending stresses will be wicked. "... the empty airplane... weighs approximately 500,000 pounds. ... It will carry about 250,000 pounds of fuel and a rocket payload of up to 550,000 pounds or 275 tons, giving it a maximum takeoff weight of 1.3 million pounds — equal to the fully loaded weight of the A380." Paul Allen’s colossal Stratolaunch plane emerges from its lair | The Seattle Times That empty weight puts it between those of a B747-8 and an A380. That is still a lot of mass to split into two big chunks on opposite ends of the center wing.
Wouldn't a flying wing design be better at handling those stresses? The two fuselages and attending bits wouldn't be hanging from the wing, but built into the wing. I'm guessing design cost is the issue because the commercial plane industry has little to no experience with the concept from having stuck to the cylinder with wings layout.
The design and build cost would be exceedingly high for a single unit. Save it for something that will spread it across hundreds of units.
