NASA 'quiet' supersonic jet is nearly ready for flight | Hacker News Reader

NASA 'quiet' supersonic jet is nearly ready for flight

theregister.com

9 pointsLinuxBender9 comments

While I don't see this making a major difference to existing passenger flight, except for the most wealthy, I can see this as having a huge impact on certain types of cargo. Time sensitive cargo like human organs for transplantation and overnight international packages. While major air carriers will probably be lukewarm about supersonics, I imagine UPS will be looking at this pretty closely.

Mach 1.4 is a bit underwhelming.

If commercial supersonic flight has any hope of being economically viable, one of the prerequisites will be cruising below Mach 2.

Why?

I've previously written a few relevant comments that hopefully answer in parts:

[1] https://news.ycombinator.com/item?id=27386119

[2] https://news.ycombinator.com/item?id=35124271

[3] https://news.ycombinator.com/item?id=35126733

Relative to say Concorde, acquisition costs and direct operating costs need to decrease and # of revenue-generating flights/time need to increase for viability. All of these point to slower speeds. If the perceived boom noise of the "quiet" supersonic designs is low enough, supersonic overland flight could potentially be permitted (NASA is trying to make this possible via this X-plane), with vastly more addressible market. Low boom limits the Mach number.

Reducing longhaul international flight times by up to 40% is not underwhelming if you fly frequently. A 380 does 0.8 mach.

I wonder what the situation will be in terms of fuel efficiency. Obviously it will take more energy per second to push through the atmosphere, but that may be defrayed by not having to hold the airplane up as long.

How many people would buy a 0.60x duration flight if it involved a reciprocal price tag of 1.66x the money?

People are paying 1.66x precovid flight costs right now in all classes. Business to Europe from Australia on the majors can exceed $15,000. There would be a market for speed: first and business class already pay a premium to get Perth London as a 16+h direct to save at most 2-3h on the Sydney London "kangaroo route" -total journey time is still around 22h.

Now, put refuelling stops in, but get total flight time down to 16h or better, and from Sydney not Perth and with hub based hookup options outside of LHR.

Here's the hypothetical concord route plans albeit briefly at mach 2+ (supersonic was banned across much of the planned route)

https://simpleflying.com/london-to-sydney-on-concorde-how-lo...

> I wonder what the situation will be in terms of fuel efficiency. Obviously it will take more energy per second to push through the atmosphere, but that may be defrayed by not having to hold the airplane up as long.

The relevant metric is mass of fuel burned per passenger seat-distance. In American units, this would be (lbs. fuel)/(pax-seat mi.). This measure allows direct comparison of differently sized airplanes with different design ranges and cruise speeds.

Take a look at Figure 1.2.7 in this study a Boeing-led team performed for NASA: https://ntrs.nasa.gov/citations/20100030607 . There were plenty of study contracts awarded under this project - Lockheed Martin did a good study as well, but the Boeing one was the first I found.

The dual/tri class band includes the (lbs. fuel)/(pax-seat mi.) for a high-efficiency large subsonic transport. Call it about ~0.1 for this aircraft type. Note the target of the study, which requires state-of-the-art technology or beyond, is 0.3 for a low-boom supersonic cruiser.

Even taking credit for efficiencies beyond Concorde technology levels, and cruising slower than Concorde, it's still ~3X the fuel burn per pax seat-mile compared to a modern high-efficiency subsonic transport. So reduced flight time is more than offset by the energy expended to fly fast and carrying fewer people in a given flight. The picture will be uglier still for supersonics compared to target efficiencies for next-generation subsonics.

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