Another new proposal for a supersonic airliner?

Here we go again with another super-cool design for an airliner that flies faster than the speed of sound.

The latest new concept design is called Skreemr, which -- if developed -- supposedly would carry 75 passengers from London to New York in 30 minutes.

Come ON already. Seems like every time we turn our heads, we're hearing about another proposed supersonic passenger plane.

By now, it's getting hard to separate engineers' dreams from what's likely in a real-world economy.

NY - LON in 90 minutes

In July, Airbus was granted a patent for a supersonic airliner that would fly from New York to London in 90 minutes.

Airbus tried to tamp down all the excitement by saying that this was just one of hundreds of concept patents filed every year.

Last year, Lockheed Martin announced it was working with NASA on a supersonic airliner that would fly from New York to LA in 2.5 hours.

Now, there's the Skreemr -- which looks downright sexy, especially to an aviation enthusiast or engineer.

But if you're among last year's 3.3 billion airline passengers, this is kind of meaningless, at least for now.

How would it work?

Here's how it might work: Skreemr's concept designer Charles Bombardier and artist Ray Mattison propose that this plane would be powered by a scramjet engine.

Unlike conventional jet engines, scramjet engines have virtually no moving parts.

And unlike rockets, scramjet engines would burn oxygen from the atmosphere instead of having to carry heavy tanks full of oxygen.

The Pentagon launched a small, unmanned scramjet aircraft in 2013, which hit Mach 5 -- five times the speed of sound.

Nonetheless, that's a long way from being an airliner.

The man with the plan

Bombardier is an inventor known for his visionary transportation concepts.

Yes he's related to the Canadian aircraft manufacturer.

He has posted more than a few unique ideas on his website including a "futuristic, electric driverless hearse," a sail boat drone and a military submersible aircraft called a Subplane.

"These concepts are far from perfect, but they're meant to get people thinking," Bombardier's website says.

He also writes for the Globe and Mail.

Even Bombardier admits that Skreemr is far from reality.

It might be possible, he writes, for Skreemr "maybe in the distant future ... to fly passengers across oceans at very high speed."

Let's get real: Scramjets are decades away from commercial airliners, and there are several technical challenges that engineers still need to overcome first.

Sonic boom

One big problem is heat.

Objects traveling past Mach 5 can reach upwards of 980 C (1800 F), and there is a limit to the type of materials that can withstand those kinds of temperatures.

The sonic boom is also all but guaranteed when an object breaks the sound barrier, and is a menace in urban areas, meaning that the Skreemr could only travel at supersonic speeds when passing over undeveloped areas.

Bombardier, however, says he has figured that last bit out.

The Skreemr would launch with an electric launch system, allowing it to accelerate at a high speed, before igniting liquid-oxygen and kerosene rockets to help it reach Mach 4 (at which point the scramjet engine would kick in).

Or, alternatively, the plane would launch without rockets initially and could switch to the scramjet engine only when flying over ocean.

A hybrid rocket and jet engine is being developed by Reaction Engines with joint funding by the UK and BAE Systems, which could one day lead to a new supersonic airliner.

The Concorde

Not to be a buzzkill, but there's a reason the Concorde stopped flying twelve years ago: Supersonic travel is expensive and people didn't want to pay for it.

The planes were making less money while facing daunting fiscal hurdles.

Make no mistake, if there's a robust market for these planes in the future, companies will build them.

Sometimes it's hard to distinguish economic viability from nostalgia.

A group called "Club Concorde" has raised £120 million ($186 million) to bring back the Concorde.

The organization -- which describes its members as "ex-captains, ex-charterers and people passionate about Concorde" -- hopes to get one of the decommissioned aircraft back in the skies by 2019, according to the Telegraph newspaper.

Why it shut down

Let's take a minute to remember the dire situation that shut the Concorde down back in 2003.

As the airline industry struggled to recover after the 9/11 attacks, a Paris Concorde crash on takeoff left 113 dead.

Passenger traffic was falling. Ticket prices were high: round-trip between London and New York was as high as $10,000.

Manufacturer Airbus said the planes would need an "enhanced maintenance program in the coming years."

Operator British Airways said that investment couldn't "be justified" in the current economy.

Who would fund it?

What would it take to design, build, test and get approval for a new supersonic airliner?

Back in the 1960s, the gigantic task took the power and wealth of the French and British governments, who paid for it and pushed it to fruition.

Estimated cost to develop and build the first four Concordes: about £1.134 billion ($1.6 billion), according to aerospaceweb.org.

Would governments or private companies be willing to spend that kind of money for a new supersonic airliner today?

Another big unknown: Could a supersonic airliner sustain itself economically?

Is rebirth possible?

An aviation reporter told CNN in September the Concorde could do well if it were used as part of a charter business.

A marketing executive for Aerion Corporation named Jeff Miller told CNNMoney last year that a new generation of small supersonic planes could succeed where the 1960s-era Concorde failed.

Improvements in aerodynamics, engines and composite materials make a supersonic passenger jet rebirth possible because they will save fuel, and ultimately, money.

Aerion is developing a $110 million, 12-passenger business jet capable of hitting Mach 1.6 -- or close to 2,000 kilometers per hour.

Expected delivery of this new supersonic plane: 2022.

One small catch: they would travel a bit slower than the Concorde to cut costs.

What? Slower than a plane that was designed in the 1960s? What's the point?

Yep, the world sure is a sucker for the nostalgia surrounding the Concorde and supersonic flight.

It'll be interesting to see how the reality will take shape.