NASA kicks off ACTE testing

a reply to: Zaphod58

Yes, I can see the problem, when fighters once in a while breaks the sound barrier over land here, people think Armageddon is on. What kind of discomfort are we talking about? Is it harmful or dangerous? I guess we are talking about people on the ground? Perhaps seaside air-strips at strategic places around the world, breaking the sound barrier way out over the ocean? But aye, boom reduction is interesting, but at the same time bending the laws of nature isn't easy. Perhaps if they made a sound bubble round the craft? Spreading the wave over a bigger area?

a reply to: Utnapisjtim

General discomfort and minor ear pain are usually described as possible effects. Propagation is why they have to go 250 miles first. A boom under the right conditions can rattle shelves almost 100 miles away.

a reply to: Zaphod58

But sound waves travel along the earth, don't they? Does the boom occur the same way in accelerated free fall as well? The cloud like thing that occurs, isn't that one always vertical? I suppose entry angle and shape has some influence. If they managed to make a vehicle that could deliver the plane up to the edge of space, and then enter free-fall and break the sound barrier in a near vertical incline, and then roll over and off you go at staggering speeds. That'd be wicked! Mother of all roller-coaster rides.

a reply to: Utnapisjtim

The vapor cloud has nothing to do with them going supersonic. It can form around any aircraft. I've seen it around a P-3.

It's caused by low pressure and high moisture levels. It's more common at transonic speeds, but can happen at any speed.

a reply to: Zaphod58

Do you see them using this to modify the wing tip dihedral as well?
Possibly canards composed of entirely flexible tech?

a reply to: cavtrooper7

They'll be able to change quite a few aspects of the wing. When the Mission Adaptive Wing flew in the 80s, it was able to change the curve of the wing to affect lift generated.

I don't know if they'll be able to affect dihedral, but this will make the overall efficiency of the wing improve in a big way.

a reply to: Zaphod58

Ok, I always thought that vapor cloud showed up when a plane broke the sound barrier. Thanks for clearing that up. But back to my main question, does the sonic book come if you move vertically downwards? That Red Bull Baumgarter who jumped out of the balloon a while back, he broke the sound barrier, as for speed, but there was no boom involved. Is the boom the amplified sound of the plane engines or does it go bang whether the plane is noisy or soundless? I could probably figure this out on my own, but if you don't mind? I wouldn't know where to start looking.

a reply to: Utnapisjtim

Most sonic booms are actually a double boom. One when the nose goes supersonic, one when the air "fills in" the "hole" behind the aircraft. They're so close together you can't hear the separation except with something like the shuttle.

To answer your question, shape plays a huge role in the boom. In the case of a person, they're too small to cause a noticeable boom.

There is a good bit of evidence that prior to the X-1 breaking the sound barrier the XP-86 did it at least twice. The aircraft was in a dive, and there was a distinct boom heard.

originally posted by: Utnapisjtim

Yes, I can see the problem, when fighters once in a while breaks the sound barrier over land here, people think Armageddon is on. What kind of discomfort are we talking about? Is it harmful or dangerous? I guess we are talking about people on the ground?

The Soviets once designed a series of projects to cruise at something like a 100-150' at supersonic speeds over massed Chinese infantry. They deliberately shaped the fuselage to maximum effect.

a reply to: _Del_

Yes, and in general, military vehicles, including planes and choppers, tanks and so on, are often designed to make plenty more noise than necessary. The sound of an approaching formation of B-52s must be absolutely terrifying.

They have completed 22 flights so far, with just the trailing edge flaps. They started with them set at 0 degrees, and ended with them at 30 degrees, and included a -2 degree setting. Each flight was completed with a single setting. In the third quarter of this year they're going to start flight testing that includes moving the flaps in flight, which will require reinstalling the flap actuators.

Are there any weight and or space trade-offs/advantages to the mechanical workings of the flap assemblies? I wonder how well they can be scaled up to say A380 size or if they are able to perform as well at say high super sonic speeds?

a reply to: Sammamishman

Yeah, you can remove some of the motors and other heavy equipment needed for the flaps, so you'll save a pretty good bit on weight, and space both with this. There's no reason it wouldn't work on any sized aircraft.

a reply to: Zaphod58

Less weight and less drag surely means better fuel economy, no? The big airlines could make big savings if this can be applied to large passenger jets

a reply to: nelloh62

Better fuel economy, less noise for passenger comfort among other things.

a reply to: Zaphod58

Any idea on the figures for fuel economy? Even 1 or 2 % is a huge fuel saving for long haul

a reply to: nelloh62It seems to me that the first aircraft did not have ailerons or flaps, but instead "Bent" the wings. Old tech if you ask me

Added: "Wing Warping". wright.nasa.gov...

a reply to: All Seeing Eye

Yeah, I think its old tech, but the leap has been making it useful for modern jets, i.e fuel and weight savings. Just found this article, so it looks like it can be adapted for large aircraft.

www.nasa.gov...

Better

Was talking to a friend who only just flown his WW1 Eindekker and it has wing warping.The Fokker system is differential whereas Bleriot was a one to one system which caused a few control reversal problems.Apart from an overly sensitive elevator (all moving stab) the monoplane was a delight in the air.