Shockwave Images Help NASA In Development of 'Quiet' Supersonic Jet (go.com)

An anonymous reader writes: NASA is working on developing a next-generation supersonic jet that can break the sound barrier with a soft "thump" instead of a sonic boom. They are using a technique called schlieren imagery to "visualize supersonic flow phenomena with full-scale aircraft in flight" with the sun as the backdrop for the photos. According to a NASA blog post, viewing shock waves and their density is crucial to the project so engineers can work on a design to minimize those reverberations. While the Quiet Supersonic Technology (QueSST) research aircraft is being developed, stunning images were captured of a supersonic jet flying at Mach 1.05 with the sun in the background. NASA says when QueSST is operational, it could "unlock the future to commercial supersonic flight over land," essentially ushering in a new era of aviation that could allow us to get from point A to point B faster and without the loud roar of the Concorde as it breaks the sound barrier.

Comments

More important than the sonic boom

[Nutria]

Are modern engines as efficient at Mach 1.5 as they are at Mach 0.9?

Re:More important than the sonic boom

[Anonymous Coward]

No, which is what doomed the Boeing Sonic Cruiser. Airlines prefer cheap operating costs over aircraft speed. In fact, they typically run their current fleet slower than the aircraft are able to cruise, for fuel economy reasons.

Re:More important than the sonic boom

[AK Marc]

The physics works differently at 0.9 than 1.1. For small planes, it may be easier to sustain 1.5, rather than 0.9. But the passenger jets aren't fighters, and would likely see increases for all increases in speed.

Re:More important than the sonic boom

[Aviation Pete]

Are modern engines as efficient at Mach 1.5 as they are at Mach 0.9?

No. The engine doesn't notice the speed, the intake takes care of that. But to create thrust, the exhaust flow must be faster than the intake flow, and making the exhaust flow faster lowers the overall efficiency of the engine. This is why subsonic engines have a high bypass ratio while for supersonic engines bypass ratio must be kept low.

Re:More important than the sonic boom

[NotAPK]

There's a bit more to the story than that.

While Boeing was developing its own supersonic airliner, they were faced with the tough task of competing against Concorde, which was already established and flying. Instead of competing, the entrenched US aviation industry smeared the supersonic airline industry and encourage an FAA sanction prohibiting Concords (or any supersonic airliner) from flying supersonic over land.

It's funny that they are now looking into this again, and all their old fear-mongering is biting them on the ass.

FAA information.

Concorde.

An example of how there is a lot of confusion regarding take off noise (which was indeed very loud) and the sustained sonic-boom during supersonic flight. The author of that page also states that he's been unable to acquire data detailing the noise at ground level caused by the sonic boom from a Concorde. My own search has also been futile...

Re:More important than the sonic boom

[sycodon]

Yes.

The Raptor's two Pratt & Whitney F119-PW-100 engines pump out 35,000 pounds of thrust each (compare that to the 25,000-29,000 pounds of thrust for each engine on an F-15). Combined with the sleek aerodynamic design, the engines allow the Raptor to cruise at supersonic speeds with less fuel consumption than any other aircraft.

So the technology is out there.

NASA or NACA?

[fsagx]

This headline could have been from the 40's or 50's. This is the way supersonic flow has been visualized as long as it has been studied. The supersonic wind tunnel and the Schlieren setup at the university I attended appeared pretty ancient to me in the 1980s.

This will only be used on business jets, if at all

[Aviation Pete]

Supersonic flight adds a new source of drag, called wave drag, which comes on top of all other drag. It depends on the slenderness of the plane, but can easily double the total amount of drag. Optimizing the design for less pronounced shock waves will increase drag yet again, so fuel consumption per mile flown will make the cost of supersonic travel prohibitive. After all, the travel speeds of modern airliners (Mach 0.78 to 0.855) is typically a bit lower than the design speed of early jet airliners like the Convair 990 (Mach 0.87) or the Vickers VC-10 (Mach 0.89). That was half a century ago!

But there is a pocket of aviation where progress has been made in flight speed: Business jets! While the first generation flew more slowly than airliners (Lockheed JetStar, Lear Jet 25), the latest designs are quite a bit faster (Cessna Citation X, Gulfstream V) at up to Mach 0.935. Why? There is a peeing contest going on among their owners who is the fastest. A very small segment of mankind is licking their fingers at a new chance for showing off. A supersonic business jet would be a sure sell to this crowd, even if the operating cost per mile doubles.

Well, see it this way: This is a chance for the other 99.9% of mankind to lower the Gini coefficient a bit.

Re: Great, just what we need

[cyber-vandal]

Being cramped in a plane for two hours instead of 10 sounds like an improvement to me.

Re:This will only be used on business jets, if at

[Maury Markowitz]

> Supersonic flight adds a new source of drag, called wave drag [wikipedia.org],

As the author of the article you are linking to (if you don't believe me, click History and look) I find it somewhat odd that you apparently didn't *actually read it*.

Wave drag is primarily and effect in the *transonic* from about M0.8 to 1.1 or 1.2, and then basically disappears at speeds above that. Jet airliners spend a significant portion of their flight time dealing with it, which is why it is important for modern air travel.

Supersonic aircraft do indeed use much more fuel than subsonic, but it's not due (primarily) to wave drag, and designing to lower boom does not necessarily upset it for the worse.

You really want faster travel? Fire the TSA.

[xxxJonBoyxxx]

>> allow us to get from point A to point B faster

You really want to travel faster? Fire the TSA.

Re:Great

[sycodon]

Actually, being able to get from point A to point B faster than a day's worth of travel will probably save countless billions in time and money for everyone from executives to a family going to Disney World, or Europe.

To get from the middle of the country to either coast takes about 4 hours in the air. Add in the precursor activities and post arrival activities and it's an entire day wasted.

Consider a Family of four going to Disney on either coast. A one hour flight vs. 4 (at best, if you get a straight through) will save you four meals, two hotel rooms for a night, and take up one less day of your vacation time.

With the Supercruise capabilities we see on F-22's it may even mean lower fuel consumption per hour.

Re:Great

[sycodon]

If you are going to drive, then drive. Enjoy the sites.

If you are flying, then you obviously have no interesting in those things. So it is in the best interest of everything to fly there as quickly as possible.

Re:This will only be used on business jets, if at

[Aviation Pete]

Where does the article even hint at wave drag disappearing at higher supersonic speed?

Wave drag is primarily and effect in the *transonic* from about M0.8 to 1.1 or 1.2, and then basically disappears at speeds above that.

Wrong. Why don't you do some basic fact-checking yourself before wrongly accusing others?

Re:Great

[unrtst]

Actually, being able to get from point A to point B faster than a day's worth of travel will probably save countless billions in time and money for everyone from executives to a family going to Disney World, or Europe.

Bah humbug! YMMV, but for me, most of my travels are within 400-1000 miles or so (or 1 - 3 hours in the air). For those on the shorter end of that, it often takes less time to just drive it once you take into account time to get to/from the airports, screening, baggage claim, etc. While supersonic may provide a noticeable difference in some cases, they really need to reduce the end point issues if they want it to seem significantly faster.