Last month, the United Kingdom announced that it was investing $90 million in what was being billed as the most groundbreaking aeronautical development since the jet engine. The public investment would be used along with private funds to build a prototype of a SABRE engine, a propulsion system that would make the world’s first true “space plane” possible.

This supersonic aircraft, called Skylon, would be able to take off from any runway in the world, accelerate to five times the speed of sound using a hybrid jet-rocket engine, then transition to rocket mode to break through the Earth’s orbit and reach outer space. After dropping off a payload of satellites, astronauts, or tiny screws, the Skylon could return to land on the same runway less than 48 hours later. Used as a traditional aircraft, the Skylon could take 300 passengers from London to Sydney in four hours. This feat would easily surpass the speed and passenger load of the airplane industry’s crowning technological achievement, the Concorde, which retired from service nearly 10 years ago after more than 25 years of transporting travelers across the Atlantic at still unparalleled velocity. News of this British superjet made it seem as though the Concorde’s rightful heir might finally arrive.

The groundbreaking technology behind the SABRE engine was based on a seemingly simple concept: A precooler would allow the jet portion of the hybrid engine to cool itself as it achieved the intense heat and power necessary to send it to Mach 5—2½ times faster than the Concorde on its best day. This crucial precooler technology was tested in 2012 to the satisfaction not only of the company that designed it, but also of the European Space Agency. Because the rocket portion of the engine would be on the aircraft itself, the Skylon would also be completely reusable and require only routine maintenance. “Access to space, access to anywhere in the world within four hours is on the cards,” said Alan Bond, the founder of Reaction Engines, the company behind SABRE.

Reports from scientists and science journalists in Britain were breathless. “This truly is a game-changer and it truly is something that only is available in the UK,” said the Guardian’s astronomy writer Stuart Clark. “I think the next few decades we might see some of the science fiction dreams we’ve had actually come true.”

The director of England’s Cranfield Space Research Centre, Steve Hobbs, said the Skylon could have the same impact on the current generation of aerospace engineers as Apollo did in capturing the hearts of Americans or Britain’s own Concorde had in inspiring the Brits. (The Concorde was a joint project between France and Great Britain.) The plan calls to have a prototype of the hybrid jet-rocket engine built by 2017 and the actual plane built by 2019 or 2020, with flights to the International Space Station carrying 15 tons of cargo to follow a few years later.

If the Skylon sounds like an impossible dream that would give Icarus or even the Concorde’s infamously ambitious designers pause, that’s because it probably is. “It looks great from a science fiction standpoint, but it’s really, really tough to do,” says John Hansman, the head of MIT’s International Center for Air Transportation. “Even if you can get the engine to work, it’s extremely challenging to get the entire airplane design to work.”

The costs are astronomical, too. The British government’s financial contribution to the project is just a small fraction of the billions needed to complete it. “Just to do a run-of-the-mill, state-of-the-art subsonic aircraft engine, you’re talking a $1 billion bill,” says Stephen Trimble, an editor at the industry publishing site Flightglobal. “It’s really hard to see that unfolding in the next seven or eight years.”

Still, if similarly pessimistic appraisals had been right about the 1.3 billion pound (7 billion pounds in today’s sterling) program to build the Concorde in the 1950s, ’60s, and ’70s, then one of man’s greatest technological feats would never have taken off. Traveling at 1,354 miles per hour, or more than twice the speed of sound, the Concorde could go from Paris to New York in 3.5 hours, less than half the time of a normal aircraft. “This most graceful of aircraft embodied our dreams of transcendence,” said Salman Rushdie in describing the plane. “[For a] brief, fabulous period we exceeded our limits … we [escaped the grip] of the surly bonds of Earth.”

While it was truly beautiful both as a piece of design and a feat of technology, the Concorde was grounded for a reason: It was one of the greatest economic boondoggles of all time. Because of the ground noise from the sonic booms caused by supersonic aircraft when they break the sound barrier, flying the Concorde (or any civilian supersonic jet) over the continental United States was outlawed. The plane’s costs and the limited distance it was able to travel meant that only 14 planes were ever used for commercial flight, and its principal routes connected London or Paris with New York or Washington, D.C. Very few people could afford a $12,000 round-trip ticket to scarf down Caspian Osetra caviar, truffle-stuffed roast guinea fowl, and Pol Roger 1986 Cuvée Sir Winston Churchill champagne on a ride from London to New York alongside Sting. “[Of 100 passengers at full load] there’s only about 10 people who were paying full fare,” said MIT’s Hansman. “Everybody else was on upgrades.” Not to mention the environmental waste—more than 6,800 gallons of fuel per hour.

The Concorde was such a phenomenal financial loser that Richard Dawkins coined the term “Concorde fallacy” to describe the phenomenon when people throw good money after bad because they have already invested so much into a failing endeavor. Ultimately, after rising maintenance costs and financial losses following its first and only deadly crash—an accident that was probably not the result of an engineering failure in the plane itself, for what it’s worth—the Concorde was put out of its misery in October 2003.

In spite of its well-earned reputation as one of the great economic debacles of the 20th century, the dream of the Concorde is still so profound that every year or so a new “Son of Concorde” is minted by the media as the plane’s spiritual successor. These “new Concordes” have actually been around since even before the original one retired. In 2002, a prototype of a Japanese supersonic plane called “the Javelin” exploded over the Australian Outback during a test flight. The Soviets built their own version of the Concorde, the Tupolev Tu-144 or Concordski, that was mothballed after just 55 flights and two dramatic crashes. The United States also attempted to build its own American supersonic jet— designed by Boeing—that would seat 277 passengers and travel at Mach 2.7. “I want the United States to continue to lead the world in air transport, and it is essential to build this plane if we are to maintain that leadership,” said Richard Nixon, announcing the project. “In the year 1978, when it will fly commercially, Tokyo will be as close to Washington, D.C., as far as hours are concerned, as London is today.” The plan was halted in 1971 after the Senate sensibly rejected further funding due to environmental concerns.

While no true successor appears to be on the horizon, a few “Concorde light” models under development in the United States actually have the potential to do what the Concorde did—take really rich people across the globe really fast. These mini-Concordes, so to speak, would seek to provide business travelers with supersonic flight on small private jets, rather than on commercial aircraft. The startup firm Aerion has been testing technology for a supersonic business jet that would transport eight to 12 passengers at speeds upward of Mach 1.6—fast enough to cut the New York to Paris travel time to 4½ hours. Gulfstream, meanwhile, is working on a similar private business jet, as is Boeing. In order to be economically viable, these new planes would have to figure out how to eliminate or mitigate the sonic boom effect that makes traveling across the continental United States untenable.

Even testing the technology would require getting lawmakers to grant permission for civilian supersonic flights over land. “Trying to change a law to allow very, very rich people to go a lot faster than less rich people over the same airspace—it’s not the easiest one to justify,” said Flightglobal’s Trimble.

These tiny, private jets for billionaires don’t seem quite as inspiring as a first-of-its-kind, superfast 100-seat commercial aircraft that accepts Air France and British Airways frequent-flyer miles. That the technological dream of a Son of Concorde will remain grounded by economic and environmental realities is probably not such a bad thing. The most viable of these proposals continue to be environmentally costly, high-tech toys for superrich people, rather than inspiring visions of man’s ability to create things indistinguishable from magic.

Even so, there’s nothing wrong with dreaming bigger about rocket planes, or even more bizarre supersonic transportation possibilities. As the Concorde proved, sometimes those dreams take flight.

Correction, Aug. 9, 2013: Due to a captioning error by Getty Images, the lead photo in this article was initially labeled as a scale model of the Skylon plane instead of a SABRE engine. The photo has been removed and replaced.

