World's largest plane makes first flight over California

[Shannow]

Originally Posted by Astro14

Originally Posted by tcp71

What happens when the pilots in the two cockpits disagree? It looks like a Siamese red headed stepchild. What happens when the rocket engine wash hits it? Not to downplay the engineering, but it strikes me much like a Howard Hughes spruce goose project rather than a viable space launch vehicle. Call me cynical...

Other large airplanes have two pilots. Are you assuming that they won't be able to talk to each other? I'm not certain how many pilots will be at the controls on this thing, but I don't see crew coordination as an issue. The Spruce Goose was a fascinating airplane, but underpowered. With 6 4056, this airplane will have over 330,000# of thrust. About the same power/weight at max gross takeoff as a 747-400, which had good power. With the relatively straight, and very long wing, it should lift off at lower speed than the 747-400 and climb more rapidly. The airplane is viable.

Personally, as an engineer, I'd like to see some connecting support structure around the tail area. Initial look is that there's huge rotational inertial loads around the centroid of the joining wing structure (pitch up/down of the two aircraft structures), plus differential aerodynamic loads (the inertial will be WAY more)....it looks like a hard ( but necessary) design.

 

[BusyLittleShop]

Typical Burt Rutan flying H design... whether its a Around the World Voyager or the Boomerang commuter or a cargo carrier or a flying car or a Reno air racer only Burt champions the basic H as the best aeronautical solution... Voyager Commuter Flying car Reno Air Racer

 

[DoubleWasp]

Well, when they needed to trash a satellite, they used a plane to launch the missile. So makes sense that if you want to get something into orbit, you start high as possible. A drop launch should make sure the plane is clear of any rocket blast.

 

[JHZR2]

I'm not really up on this stuff. Is the intent to launch a rocket off of the airframe, or to release the rocket from the airframe and then let it ignite while falling? The structure is intriguing, would have thought they would have to connect tails.

 

[4WD]

Check the links I posted ... they show an animation of a rocket launch ,..

 

[DoubleWasp]

Good explanations for a lot of things. Launch will be a drop launch. Ignition won't occur until rocket is released. The company making the rockets currently drops them from L1011's. Tail, like the Virgin Galatic launcher, is not joined in the middle so there is nothing to receive aerodynamic turbulence from the payload mounted to the center wing

 

[Shannow]

Yeah, but note that all the "H" planes that BLS displayed have a closed arrangement for the transmission of inertial forces. A Rocking Couple of an extended fuselage (Inertial effects are proportional to length to the power of 4) about the common centroid of winglett cojoining the two fueselages is a serious design feature. I agree that getting rid of the tail structure is good from turbulenace....I can't fathom how they maintained the required torsional rigidity, without introducing low cycle fatigue in what appears to be a normal wing section. A normal plane can't "torque" itself against the wings enough for the wings not to move. A dumbell (long fuselage) at either end of a torsional column (the inter fuselage winglett) is a design point that draws the interest of (well at least this) mechanical engineer.

 

[emg]

The separate tails always looked strange to me, but they must have a good reason for it. In terms of fatigue, my guess is that this will make fewer flights in its lifetime than a busy airliner would in a year, so that may not matter.

 

[Astro14]

Originally Posted by Shannow

Yeah, but note that all the "H" planes that BLS displayed have a closed arrangement for the transmission of inertial forces. A Rocking Couple of an extended fuselage (Inertial effects are proportional to length to the power of 4) about the common centroid of winglett cojoining the two fueselages is a serious design feature. I agree that getting rid of the tail structure is good from turbulenace....I can't fathom how they maintained the required torsional rigidity, without introducing low cycle fatigue in what appears to be a normal wing section. A normal plane can't "torque" itself against the wings enough for the wings not to move. A dumbell (long fuselage) at either end of a torsional column (the inter fuselage winglett) is a design point that draws the interest of (well at least this) mechanical engineer. It's OK if you don't get the question...

I think that's why the airplane is remarkably heavy - there is a lot of structure in that center wing box. Both to resist torsional loads from the rocking of the fuselage sections, and to carry the external payload. I'm not an engineer. But I was surprised at the 800,000# weight of the airplane (full up, including fuel). The 747-400, for comparison, weighed about 410,000# with all the passenger accommodation and interior bits installed. A brand new airplane, delivered from the factory, without interior, was closer to 325,000# (a friend picked up the YAL-1 prototype from Boeing, and that's about what the empty airframe weighted). Fuel capacity on the 747-400 was 379,000# for 14 hour flights with reserves. This airplane has 150% the consumption, but the mission profile is much shorter, so let's suggest a generous 300,000 max fuel load, that gets it up to altitude and several hours of cruising. That still leaves an airplane that weighs about 500,000# zero fuel weight. Or about 1.5 times as much as the 747-400, with similar length and longer wings. That figure surprised me, that's all. I reckon it's all structure to carry those loads, torsional, payload, etc.

 

[DoubleWasp]

Originally Posted by Shannow

Yeah, but note that all the "H" planes that BLS displayed have a closed arrangement for the transmission of inertial forces. A Rocking Couple of an extended fuselage (Inertial effects are proportional to length to the power of 4) about the common centroid of winglett cojoining the two fueselages is a serious design feature. I agree that getting rid of the tail structure is good from turbulenace....I can't fathom how they maintained the required torsional rigidity, without introducing low cycle fatigue in what appears to be a normal wing section. A normal plane can't "torque" itself against the wings enough for the wings not to move. A dumbell (long fuselage) at either end of a torsional column (the inter fuselage winglett) is a design point that draws the interest of (well at least this) mechanical engineer. It's OK if you don't get the question...

I get it. I have no doubt that there is a lot of undesirable forces at play here. But does it not follow that "optimal" or not, if you make it strong enough, that it will take it? Since the area of interest (center wing) is already bearing an extraordinary load from the payload, would this area not already be built like the proverbial brick outhouse? But I do understand the problem. A force acts on one horizontal stabilizer. That force is acting on a lever (the fuselage). The other stabilizer is doing its job: Stabilizing. So now that force is acting to hold a lever that is attempting to change position (transferred via center wing). So how does the whole thing not start dancing Dubstep in the sky? But we know it doesn't. So how in the world did they manage the act of making the whole assembly **that** rigid? And if those forces aren't turning the plane into a passable impression of a third grader engaging in slap-fight, then what are those forces doing? Good question for the engineer who penned it, because I'm definitely not smart enough to know. All we do know is that this is the second operational launcher of this type. They know something perhaps we don't.

 

[4WD]

One of the interesting aspects of the dual fuselage is it seems ideal for a "low boy" trailer to drive right under for the payload latch up … and I'm sure they will have "mission control" on the off side from pilots and thier engineers …

 

[PimTac]

The news is out that this project is being shut down. Reminiscent of the Spruce Goose.

 

[AdmdeVilleneuve]

A discussion on the Roc's potential future uses below. Given all the other options available, it may have limited interest. https://www.thedrive.com/the-war-zo...argest-airplane-with-an-uncertain-future

 

[Cujet]

Originally Posted by PimTac

The news is out that this project is being shut down.

Paul Allen had the vision. His family does not. Hence the shutdown. Sad to see the family simply shut down his dream.

 

[DoubleWasp]

Seems quite the stupid thing to do when they have a running model ready to go. I can see this happening in the vaporware stages. But to dump the thing right after proving a working model? Weird.

 

[PimTac]

Originally Posted by DoubleWasp

Seems quite the stupid thing to do when they have a running model ready to go. I can see this happening in the vaporware stages. But to dump the thing right after proving a working model? Weird.

On the other hand, if there is any viability in the project someone else can step in and fund it. Paul Allen's sister, Jody is running the foundation now. She doesn't have the vision that Paul did and she has admitted that. The foundation also owns the Portland Trail Blazers and the Seattle Seahawks. She is not a big sports person so that is another area being watched. She has mentioned that she wants to continue the project that finds old WW2 wrecks. If all the projects Paul Allen has funded, that one has been very successful and memorable. The next couple of years will tell the story.

 

[MolaKule]

Originally Posted by DoubleWasp

I get it. I have no doubt that there is a lot of undesirable forces at play here. But does it not follow that "optimal" or not, if you make it strong enough, that it will take it? Since the area of interest (center wing) is already bearing an extraordinary load from the payload, would this area not already be built like the proverbial brick outhouse?

Any wing that is going to carry high loads has at least two Spars and a number of Ribs and Stringers. There are a number of options to strengthening wings: 1) Most wings have two spars; One could always add a third Spar; 2) Make the Spars larger, i.e., larger cross sections; 3) use tougher Spar materials such as Ti-6AL4V 4) use more or larger stringers; 5) add more ribs, i.e., space them closer together.

Originally Posted by DoubleWasp

But I do understand the problem. A force acts on one horizontal stabilizer. That force is acting on a lever (the fuselage). The other stabilizer is doing its job: Stabilizing. So now that force is acting to hold a lever that is attempting to change position (transferred via center wing). So how does the whole thing not start dancing Dubstep in the sky? But we know it doesn't. So how in the world did they manage the act of making the whole assembly **that** rigid? And if those forces aren't turning the plane into a passable impression of a third grader engaging in slap-fight, then what are those forces doing?....

I would think that once the moments of each major section of the airplane structure are determined, those moments would then be inserted into the Flight Control Computer's, Control Law Equations to mitigate any unwanted or induced motions. The article above stated that Northrop Grumman's "Scaled Composites" division actually designed and built the aircraft, so maybe Northrop Grumman has an interest in furthering the project?

 

[Cujet]

Originally Posted by MolaKule

I would think that once the moments of each major section of the airplane structure are determined, those moments would then be inserted into the Flight Control Computer's, Control Law Equations to mitigate any unwanted or induced motions.

I'll bet that's exactly how they did it. Today's fly by wire flight controls are off the shelf components, programmed accordingly. That brings to mind the famous X-29 with it's unstable forward swept wing and necessary fly by wire configuration. The newer models of Gulfstream business jets now incorporate fly by wire flight controls. It may seem that it's just an electronic version of the previous mechanical flight controls. Not so! Besides turbulence mitigation, a good example is that both ailerons go up and the horizontal stab moves appropriately upon landing to spoil lift and increase brake function. This is so effective, the G650ER can sometimes make the first taxiway!

 

[billt460]

Originally Posted by Cujet

That brings to mind the famous X-29 with it's unstable forward swept wing and necessary fly by wire configuration.

Or the German Hansa Jet business jet that never was able to establish a market. A bit ahead of it's time. https://en.wikipedia.org/wiki/Hamburger_Flugzeugbau_HFB_320_Hansa_Jet

 

[DoubleWasp]

True enough. And NG does have a high level experience with both FBW and apparently unstable flight designs (B2).