Cubdriver

Do we really need another Concorde? I think this is a dumb idea. As much as I love novel and creative aircraft designs this one seems like a non-starter. The only thing these airplanes would offer Concord did not offer is a more spread out sonic boom and synthetic fuel capability; not worth billions in R&D in my view. Use the money to develop better fuels and engines for the existing jet fleet and even have some money left over for a tax rebate.

NASA asks for Concepts for the Next Supersonic Airliner

msmspilot

See, that's the thing. A lot of projects like this never deliver the product originally envisioned, but they do deliver a lot of technological advances which are incorporated into new designs and into retrofits.

Is it worth it? Well, you can never put an ROI on R&D. Sucks for the number cruncher types.

Edit: You can never put a real ROI on R&D.

whatthe6789

Did anyone notice this little tidbit?

"Both the Boeing and the Lockheed Martin designs place the engines on top of the wings rather than below like those on the Concorde. Since jet engines are very good at converting fuel into noise, the goal is to have some of that roar shielded from the ground by the wings."

I guess I never realized that the sonic booms originated from the sound coming from the engines...

Cubdriver

Sonic booms come from the underside of the nose. You can spread out the pressure gradient of the shock wave somewhat by using a concave/convex shape under the nose, so-called "shark" nose. That idea has been around for decades and it works but cannot remove the boom entirely. What the engine placement above the wing deals with is sound pressure footprint near major airports which is a larger consideration with low-bypass ratio turbojets used on supersonic airplanes. When the shear layer coming out the back is compacted into a smaller relative diameter noise made by the engine goes way up, which is one reason modern subsonic a/c designs tend toward higher bypass ratios, aside from thermodynamic efficiency which is the main reason. Remember the early 737s with JT8Ds and how loud they were? The JT-series is also used in supersonic aircraft as a low-BPR design.

rickair7777

I think NASA is correct in exploring this. A supersonic airliner has been shown to be somewhat practical using 1960's technology...it's not unreasonable to assume that the application of subsequent technical advances combined with specifically targeted R&D might yield a system which would could be safe, green, and make economic sense (compared to concorde).

Of course similar advances applied to subsonic transports would mean that an SST would still be less green and more expensive than subsonics. Whether it would be economically viable would come down to regulatory considerations and demand for fast travel. You would need to manufacturer more than 20 of them to get an ROI...way more than 20.

tuna hp

I think that they could actually be pretty feasible, its just the materials question and the shock wave question. The pure turbojet engines that would be used are mechanically more efficient than turbofans, and they should provide higher propulsive efficiency at around Mach 2 where I assume this plane is flying. And drag should actually be LOWER flying supersonic than in the transonic ranges that planes are flying now. If they can fix the noise problem and if they can build them light enough (presumably with composites), then it should work. Supposedly the concorde was very profitable.

DYNASTY HVY

Concorde was profitable indeed .
Concorde - An Untimely and Unnecessary Demise


Fred

msmspilot

This article does not include initial acquisition cost. The "didn't make money" I heard was that BA and AF got the Concorde for next to nothing because their respective governments paid the R&D cost and it didn't get passed on to the airlines. If it had been priced to sell to make a profit for the manufacturer, BA and AF couldn't have recouped the cost.

Also, your article is interesting, but there is a difficulty in doing cost estimates for something that you don't have all the data on. The 3x fuel cost for maintenance rule works well on small airplanes, but I don't know that you can assume it for a Mach 2 F1 racer of the sky.

Cubdriver

The number given to us in aerospace college was 75 for most large and/or fast jets (fighters, bombers, large transports). To be practical, a next-gen SS airliner would have to be largely derivative of the Concorde because a clean sheet airplane of this kind is not feasible without government subsidies. The 787 was a clean sheet design, and the developmental obstacles for even such a conventional subsonic airplane were daunting. The economic model does not work for another Concorde in my view. There would have to be a massive shift over to SS transoceanic routes in order for it to work, an unlikely scenario. A supersonic business jet is a modest possibility, however. Aerion has a design they still working on. NASA is helping them with the aerodynamics of a wind tunnel model.

Cubdriver

Sorry but this post is wildly erroneous. It is a matter of simple Newtonian physics F=ma that greater efficiency comes accelerating a larger mass of air a smaller amount than a smaller mass one a larger amount. This is why the fan diameters of subsonic jets have steadily grown over the years. While fighters cannot use high BPR engines for the most part, they have steadily enjoyed bypass ratio increases within the tolerance of their design limits.

CD above the speed of sound is not lower than below the speed of sound. I challenge you to produce anything supporting this statement. Fighter jets do not cruise at SS speeds because they must use inefficient afterburners to do so. Even allowing that more efficient designs are available that do not depend on afterburners (F-22, F-35, Concorde), overall efficiency is lower no matter how you slice it in the SS regime because you are depending on acceleration rather than mass flow rates. Wiki article on supercruise.

As for the profitability issue, the pricing structure for the Concorde was far on the right of the price versus quantity plot. That's fine, you can sell one ticket a year at say 5 million dollars each and still make profit. Passenger space flights use that model. But to launch a premium transportation mode without expecting enormous developmental costs is silly, and that's what we are talking about here.