Hermসs: The hypersonic aircraft is designed to fly from NYC to London in 90 minutes.

(CNN) – Nearly two decades after Concord’s retirement, interest in supersonic travel is growing, and several super-fast planes are being built. Airlines seem interested: United has already committed itself to offering supersonic routes by early 2029.

But what about hypersonic travel, which happens at the speed of the Mac5 – five times the speed of sound – and above? It will take a flight from New York to London in just 90 minutes, compared to about three hours for Concorde and six to seven hours for a regular passenger jet.

Is it even possible?

Hermione, an Atlanta-based startup whose goal is to create hypersonic aircraft, believes so. It is already testing a new type of engine that says it will eventually reach Mach 5 (over 3,000 miles per hour). The engine is designed for a small, unmanned hypersonic aircraft Hermাসs is currently building for the US Air Force, but on a larger scale it will be able to power a passenger aircraft.

That passenger plane is a long way off – Hermione hopes to take it to the air for the first test flight before the end of the decade in 2029 – but because its technology will have to be built almost entirely from the ground up, the company is already planning it.

For starters, it will be much smaller than the current airliner and even Concorde, which had a capacity of about 100 passengers.

“To help shape our aircraft, we’ve basically created a business model for an airline,” said AJ Piplica, CEO of Herms. “We focused on business class and first class travelers, and then played with some parameters like speed and operating costs. What came out of it was an aircraft with a 20-passenger cabin,” he added.

This is not far from the capabilities of a large commercial jet, which means there will only be one class.

“We hope it will be profitable in today’s business class prices,” said Piplica, adding that it is difficult to determine how much people would be willing to pay to fly five times faster, because “you really can’t answer this question unless there is a product and You have the real data. “

Faster than before

The plane’s range would be about 4,000 nautical miles, enough for a transatlantic route from New York to Paris, but not for a transpacific route from LA to Tokyo, which would require a stop.

Routes over land, such as LA from New York, are out of the question due to noise rules: breaking a noise barrier produces a loud boom, which usually occurs over water.

To understand how daring the concept of a Mach 5 passenger plane is, it is useful to look at flight speed records.

The fastest Mac 9.6 (about 6,800 miles per hour) that any aircraft with an engine has ever flown, a record was set by NASA X-43A in 2004 – an unmanned aircraft with a length of about 12 feet.

Because that flight lasted only a few seconds, the record for the longest lasting flight on March 5 belongs to the Boeing X-51, another unmanned test aircraft that flew more than three minutes in March 2013 at Mach 5.1 (about 3,400 miles per hour). Both aircraft had to be launched from a height by a B-52 bomber, and then brought into motion by a rocket, highlighting the complexities of such high-speed flight.

For aircraft with people on board, the current absolute speed record is the Mac 6.7 (4,520 miles per hour), set in 1967 by the X-15. It was originally a rocket with a seat, designed for record-breaking, and had to be launched from a height by a B-52.

For an air-breathing aircraft – that is, powered by a jet engine instead of a rocket – capable of automatically taking off and landing, the speed record is “only” Mach 3.3 (approximately 2,200 mph), set by SR-71 Blackbird, A military spy plane, in 1976.

Concorde’s top speed, one of only two supersonic passenger aircraft to fly commercially, was the Mac 2.04 (1,350 miles per hour).

The proposed Hermione passenger aircraft, therefore, could break the current record for the fastest air-breathing aircraft by a large margin, and by flying for an extended period of time on March 5, it would surpass an achievement in current unmanned test vehicles (of course, other aircraft before Herms). May lose these records in the future).

‘Mature technology’

Not surprisingly, the company’s primary focus is on engines. Tests began in February 2020 for a new type of engine design based on an existing model used in fighter aircraft and built by General Electric.

It will be a hybrid of two traditional technologies: a turbojet, similar to what airliners use, and a ramjet, a type of engine that operates only at supersonic speeds and above. Initially, the engine will power the Quarterhorse, a smooth hypersonic drone that Hermione is building through a $ 60 million partnership with the U.S. Air Force.

Interestingly, when designing a jet engine to go faster, the parts are moved instead of being added. In a turbojet, air enters from the front and is first compressed by rotating the blade (to increase its power potential), then ignited by mixing with the fuel. The resulting hot gas explodes through the rear of the engine, pushing the aircraft forward.

On top of the Mach 3, however, there is no need to compress the air: it will compress itself as soon as it enters the engine, simply by reducing the speed so much. Therefore, for speeds above Mach 3 and up to Mach 6, an engine type called ramjet is often used – so called because it literally floats in the air. It has no moving parts, unlike turbojets, but it doesn’t work at speeds below Mach 3 at all.

Hermসs will use its hybrid engine in turbojet mode when taking off and landing, as well as at subsonic speeds. Then, the engine will slowly reconfigure itself in a Ramjet mode as it reaches Mach 3 and Mach 5.

“The turbojet part and the ramjet part themselves are mature technologies that we’ve been using for 50 years. The strategy is to combine them, so we designed our own architecture around an off-the-shelf turbojet engine and then built it থেকে from there,” says Piplica.

SpaceX Inspiration

There are a number of issues that Hermes is not working on right now, such as the need to use any kind of sustainable fuel – as the use will be much higher than current jets – and the extreme temperatures that the hypersonic fuselage plane must be able to withstand.

Concorde’s speed, which traveled at less than half the speed of Hermione’s estimated speed, was limited by the temperature at which the windows and other interior surfaces became warm to the touch at the end of a flight.

The SR-71 Blackbird, on the other hand, had to make titanium, a rare metal that can withstand extreme heat, and the cockpit glass was made of quartz, with the outside temperature reaching 600 Fahrenheit during one mission.

In response to skepticism about Hermione’s chances of success and the need for a potentially large amount of funding, Piplica bears a resemblance to Elon Musk’s SpaceX.

“I think people asked the same question about the new space industry in the early days of SpaceX,” he said. “People looked at the orbit entry and said it should cost a billion dollars, but with SpaceX Falcon 1 it did for 90 million dollars.”

Hermione plans to build and finance a variety of aircraft en route to her passenger plane, as well as the development of SpaceX’s Falcon 1, Dragon, Falcon Heavy and Starship rockets, which ultimately serve as a vision of interplanetary spacecraft and work with it. NASA and commercial partners.

“There’s really nothing like Hermione, although many similar projects have come and gone in the past,” said Richard Abulafia, an aviation analyst at Till Group. “It never seems to be working. If they could magically create a hypersonic transport by the end of the 2030s and the ticket price is within the business class range, yes, it will be successful. Range. “

If and when a hypersonic passenger plane becomes a reality, what will it be like to fly in it?

“It’s going to be like Concord,” Piplika says “You’ll be faster than today’s plane, where you’ll feel pushed back in your seat for about 30 seconds to a minute or more.

“That experience will probably last 10 to 12 minutes. But once you get to Mach 5, 100,000 feet or more, it will be a really smooth ride. There’s not much air traffic, and the atmosphere is relatively gentle.”