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  (Source: Boeing)

  (Source: Boeing)
The X-48B finally takes flight

The X-48B blended-wind experimental aircraft has been profiled twice before on DailyTech. We first brought you news of the aircraft in May 2006 -- at the time the X-48B was scheduled to take to the air for the first time at the end of 2006.

As is the case with many complex research projects, that first flight was delayed. In March of this year, DailyTech noted that the Air Force, Boeing and NASA were getting close to flight trials for the X-48B. Again, months passed and nothing happened.

Today, we're happy to report that the 8.5 percent scale X-48B finally took to the air on July 20. The 500-pound, 21-foot remotely-piloted aircraft stayed aloft for 31 minutes and reached an altitude of 7,500 feet before touching down at Edwards Air Force Base.

"Friday's flight marked yet another aviation first achieved by a very hard-working Boeing, NASA and Cranfield team," said Dryden Blended Wing Body project manager Gary Cosentino. "The X-48B flew as well as we had predicted, and we look forward to many productive data flights this summer and fall."

The X-48B is powered by three turbojet engines. The engines have the ability to propel the aircraft at speeds up to 138 MPH and can push it to a maximum altitude 10,000 feet.

The research gathered from the X-48B program will be used to help develop next-generation blended-wing military and commercial aircraft that are more fuel efficient, offer increased cargo/passenger space and are quieter than their traditional counterparts.

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138MPH?!?!
By Cobra Commander on 7/27/2007 1:51:52 PM , Rating: 1
Sounds awfully slow...????




RE: 138MPH?!?!
By Brandon Hill (blog) on 7/27/2007 2:10:13 PM , Rating: 3
It's a scale model remote control research plane, not a full-size craft.


RE: 138MPH?!?!
By jay401 on 7/27/2007 2:47:47 PM , Rating: 5
maybe that's 8.5% of the full-size speed too ^^


RE: 138MPH?!?!
By helios220 on 7/27/2007 2:50:46 PM , Rating: 4
Obviously the engines on the 8.5% scale model are not the engines that will be on the full scale production aircraft.

The point of scale tests of this nature are to test the aerodynamic tendencies of the blended wing shape, not to replicate the exact performance of a final product. The 138 MPH speed is no real indication of the speed of a full size platform with full sized engines.

What you also may be missing in the article is the 500 pound weight of the scale model. A single contemporary GE90-94B engine weighs 16,644 pounds. I’d be interested to know the weight and thrust of the scale model engines, but regardless 138 MPH is not too shabby for such light weight engines.


RE: 138MPH?!?!
By killerroach on 7/27/2007 3:07:15 PM , Rating: 2
Well, 8.5% scale would mean each dimension is 8.5% of the original, meaning the volume (and presumably mass) would be .0614% of the original. By those figures, you'd end up with your finished bird being somewhere in the neighborhood of 400 tons, more than enough to support your modern aircraft engines.


RE: 138MPH?!?!
By bubbacub616 on 7/27/2007 3:52:14 PM , Rating: 2
"presumably mass" is a pretty big assumption. i doubt that mass will scale linearly with size.

to compare, a 747 is around 130 tons. given that one of the proposed benefits of BWB design is a lighter aircraft i therefore find myself disputing your assumptions.


RE: 138MPH?!?!
By Anonymous Freak on 7/27/2007 5:11:29 PM , Rating: 2
The benefit is lighter design compared to equivalent capacity. BWB is a *LOT* bigger than a 747. 400 tons may not be out of the question for an aircraft the same length and wingspan as a 747, since it will have many TIMES the usable interior volume.


RE: 138MPH?!?!
By bubbacub616 on 7/27/2007 3:52:35 PM , Rating: 2
"presumably mass" is a pretty big assumption. i doubt that mass will scale linearly with size.

to compare, a 747 is around 130 tons. given that one of the proposed benefits of BWB design is a lighter aircraft i therefore find myself disputing your assumptions.


RE: 138MPH?!?!
By Danthrax on 7/27/2007 5:26:54 PM , Rating: 4
quote:
i doubt that mass will scale linearly with size.


The mass will scale linearly with volume, so killerroach is right, it will be 0.0614% of the mass, if everything is scaled accurately. Of course, models are somewhat simplified, so the model will be somewhat heavier than a perfect scaled replica would be.

quote:
a 747 is around 130 tons


The max takoff weight of a 747 is 900,000 pounds, which is over 400 tons. So this BWB model is right where we'd expect it to be.

As to 138MPH, the Reynolds Number for the scale model will be very different than for the full sized aircraft. In effect, the model will experience much more viscous air, so 138MPH is quite reasonable.


RE: 138MPH?!?!
By Keeir on 7/27/2007 6:51:02 PM , Rating: 2
1. Scale models for aerodynamic purposes are rarely fully scale models due to the desire to have flight condition full sized Reynolds numbers with the much smaller devices.

2. Due to the smaller size, many structures that would be peiced in a final aircraft will be monolithic/extra large

3. Certain materials are very difficult to form properly into small models, but can be formed correctly at larger sizes for additional wieght savings as well

At least I hope so, because at a structures wieght of 814 kips for BLB (in comparision, the empty wieght of the 747-8I/F is 410 kips) there won't be alot of room left over for cargo once the fuel has been loaded. The 747-8 series has a maximum cargo wieght of around 140 kips and a Maximum Take Off Wieght of 970 kips. That says to me, to fly the plane requires 420 kips of fuel.


RE: 138MPH?!?!
By HotFoot on 7/30/2007 3:01:23 AM , Rating: 2
I'm wondering what this group is trying to prove by flying this scale model. Surely it must be stability/controllability of an unconventional design. However, the similarity criteria are so far from matching that it will limit the usefulness of the results. Really, with a scale model, it's hopeless to match any of the similarity criteria, ie:

1) Mach number: as has been pointed out, there's not much hope of getting to 0.8-0.9 M range with this model or these engines (the criteria is missed by a factor of over 4.25). No matching Mach number means no matching pressure distribution over the wings (though the model design can be fudged to compensate at least somewhat). That totally changes the aerodynamic response of the flight control surfaces, to mention one thing.

2) Reynolds number: proportional to length scale * velocity scale. In this case, the Reynolds number is un-matched by a factor of around 50. I'm sure the boundary layer is tripped using some roughness strip-esque technique, but even so, how useful will the collected data be?

The model can be completely flyable, but how much will that mean in terms of a full-scale, full-speed aircraft?


RE: 138MPH?!?!
By bubbacub616 on 7/27/2007 6:56:05 PM , Rating: 2
"The mass will scale linearly with volume, so killerroach is right, it will be 0.0614% of the mass, if everything is scaled accurately. Of course, models are somewhat simplified, so the model will be somewhat heavier than a perfect scaled replica would be."

thank you for making my point

a planes weight is generally taken as being the unladen load. which is 130 tonnes for a 747 (you are correct in stating that the max load is 400). This is all a moot point since this is an experimental radio controlled model that we are using to extrapolate data. We need to see full size prototypes flying before the internet reading public can make conclusions about the viability and load caring capacity of BWB designs.


RE: 138MPH?!?!
By Triring on 7/29/2007 10:57:48 PM , Rating: 3
What in the hell are you talking about???

Mass and volume only scale linearly if it is made with the same material in the exact weight ratio. Since we do not know what this model was made out of it is meaningless.

It could be made out of paper and plywood for all we know, and the electrical wiring will be much more complex larger size means heavier standard landing gears and so on and so forthe.


RE: 138MPH?!?!
By Jammrock on 7/27/2007 10:08:44 PM , Rating: 2
I believe the plane's end goal is upper atmosphere hypersonic flight. The theory is that if you fly above the area into the lower mesosphere (about 50 km or 30 miles) you can fly at MACH 5+, i.e. hypersonic. To save on fuel the plane would little skip, like a stone on a pond kind of skip, off the stratosphere so the only time the plane would require heavy fuel burn would be to accelerate back up after the "bounce," and then slow burn while you drift up and then down.

All theoretical, of course, but that's the rough plan, and the X43 and X48 are supposed to the very early predecssor for this kind of travel. The hope is along the lines of NYC to Tokyo in under 5 hours. Not too shabby.


RE: 138MPH?!?!
By JeffDM on 7/30/2007 1:10:14 AM , Rating: 2
I don't think this blended-wing model was intended to go hypersonic. The sweep on the picture shown doesn't have enough of a backwards sweep to sustain supersonic travel. The X-43 you mention has a much more rakish wing sweep.

The idea of BWB isn't for supersonic or hypersonic, the idea of blended wing is to carry a LOT more passengers and cargo without being a lot more expensive, meaning less cost per passenger/per package/etc.


RE: 138MPH?!?!
By roadhog74 on 7/30/2007 3:50:52 AM , Rating: 2
The most critical times for an aircraft is take off and
landing. At these times you would expect the full sized
edition to be traveling about this speed.

So I would expect that they would be able to gain quite
a lot of data that is significantly more important than
how it behaves at MACH 0.9.


Wait- did I miss something?
By Comdrpopnfresh on 7/27/2007 1:22:06 PM , Rating: 2
8.5% model? How big is the real thing supposed to be?

Also, 136 mph doesn't sound right. You'd think turbo-jets could get the thing going...




RE: Wait- did I miss something?
By h0kiez on 7/27/2007 1:41:36 PM , Rating: 4
Uhhh....

21' / .085 = 247'?

I'm not a mathemetician, but this one doesn't seem that complicated. Oh yeah...I'm guessing the full scale one will be faster too.


RE: Wait- did I miss something?
By spluurfg on 7/27/2007 2:00:49 PM , Rating: 2
247 feet would be just longer than a 747. I'm not totally sure if 8.5% is scaled just from the length... it might be by volume, so the resulting aircraft wouldn't be quite so large... don't forget that if you, say, double each dimension of a rectangular object, its area increases by a factor of four and its volume by a factor of eight. Granted planes aren't rectangular...

Anyway, 130ish mph is pretty slow, but don't forget it's just a small model... also, since the whole thing looks pretty much like a flying wing, the idea may be to get more lift at a given speed than a conventional fuselage+wing approach, allowing you to fly at slower speeds economically (as speed increases linearly, the force of drag increases exponentially).


RE: Wait- did I miss something?
By masher2 (blog) on 7/27/2007 2:33:07 PM , Rating: 3
> "Granted planes aren't rectangular..."

The cube-volume relationship holds for any object geometry, not just rectangles. So I think we can assume the full-size vehicle would have (1/0.85)^3 = 1600 times the volume of this scale model.

> "I'm not totally sure if 8.5% is scaled just from the length..."

That's the typical usage of the term "scale model". I don't think 247 feet is out of the question for the full-size craft. Remember that a blended-wing variants contain significantly less passenger space, when compared to traditional craft of roughly the same size.