Sonic boom or bust? Dreams of super-fast jet travel revival face headwinds

* Two of three firms pursuing supersonic jets eye private market

* Fuel efficiency, noise, economics seen as major challenges

* New generation supersonic jets seen priced at $100-$200 mln

By Jamie Freed

Dec 22 (Reuters) - Supersonic passenger travel, which died out with the Concorde's demise in 2003, will make a comeback by the mid-2020s if three entrepreneurial U.S.-based companies can make jets quiet and efficient enough to win over buyers and fliers.

Fifteen years ago, Boeing Co cancelled plans to build the near-supersonic Sonic Cruiser, the last big attempt by a major manufacturer to speed up commercial travel.

Now Japan Airlines Co Ltd and Virgin Group are backing one of the three U.S. supersonic projects, Denver-based Boom Technology Inc, which plans a 55-seat all business class jet.

Lockheed Martin Corp is partnering with Aerion Corp to develop smaller supersonic business jets, with Spike Aerospace Inc also targeting the private jet market given many see the super-rich as the likeliest early adopters of supersonic travel.

Concorde was developed in the 1960s, meaning this is hardly a new technology. But the programme was government-backed, with only 14 jets ever delivered to then-government owned British Airways and Air France. Other airline orders evaporated as the purchase price soared and they were eventually retired as maintenance costs rose and passenger revenue fell.

New players are relying on venture capital funding models.

"This is more about engines and economics than it is about airframes," Richard Aboulafia, the vice president of analysis at aerospace research firm Teal Group, said of the challenges of a supersonic revival.

To make the project economics stack up the engines need to be far more fuel efficient and less noisy than those used by Concorde or fighter jets.

That has proven tough to engineer, especially at higher speeds like the Concorde's Mach 2, which halved the travel time from London to New York to 3.5 hours.

'REALISTIC PROJECT'

Engine manufacturers and jet makers have spent decades improving fuel efficiency, expanding range and reducing noise.

But to get up to mach speed, a supersonic jet requires an engine core more like those on the commercial jets of the 1970s and 1980s which noisily gobble more air and fuel.

"A large fraction of the benefits we have in efficiency and noise reduction we are going to lose as soon as we have to go back to that sort of architecture," said Daniel Edgington-Mitchell, an aerospace engineering lecturer at Melbourne's Monash University.

Aerion, the most advanced of the proposed supersonic jet projects, is working with GE Aviation to develop an engine based on a core used in F-16 fighters and Boeing 737s that was developed in the 1970s, a GE spokesman said.