american sst

The Forgotten American Concordes – Boeing 2707 – Lockheed L-2000 SST

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When we think of supersonic passenger air travel, most people will think of Concorde, the joint British & French design which operated from 1976 until 2003 and up until this day, has been the only long term supersonic passenger jet service to operate.

What many people don’t know is that in the 60’s a 70’s there were three other competing designs from the United States and Russia.

The Russian Tupolev Tu-144 was the first commercial supersonic transport aircraft (SST) which had its first flight 2 months before Concorde on 31st December 1969.

However, after a crash at the Paris air show of 1973 and another in 1978 it was grounded after just 55 flights, though it remained in use as a research platform well in to the 1990’s.

The other two American designs are less well known about because despite huge government backing and that supersonic transport was to be the next big thing after the moon landings neither of the designs by Boeing and Lockheed made it in to the air.

The story starts in 1962 when the British and French governments announced that they jointly build a new airliner that could travel at over twice the speed of sound which was to be called the “Concorde”.

This was to be the most advanced civilian aircraft in the world, showing that European aircraft manufacturers could create the most leading-edge designs, something that the Americans believed that they were the best at.

To meet this new challenge and rescue American national pride,  President John F Kennedy stated that America would build it’s own supersonic transport aircraft and that it would be both bigger and faster than the European design.

Two designs, one from Boeing and the other from Lockheed were selected for further development and as an incentive the US government would pay for 75% of the programs cost.

The Lockheed L-2000 design was almost a scaled up Concorde and intended to fly at up Mach 3.0 or 2300mph while carrying 270 passengers for a range of 4,000 miles.

The development of smaller fighters like the French Mirage III fighter and the Russian MiG-21 had already proven the delta shape wing similar to Concorde could easily go to Mach 2 and beyond and this was the route that Lockheed chose.

Boeing on the other hand opted for a much more complex swing wing design that would be straight at low speeds which would improve the takeoff and landing and then swing back to become a delta wing as the speed increased.

Boeing’s 2707 design was supposed to be able to fly at Mach 2.7 or 2000mph and carry more than 270 passengers for more than 4,200 miles.

After much testing, the Boeing 2707 design was chosen as the winner on 1st January 1967.

Progress though, was far from smooth, one of the main features that the 2707 was meant to have was the ability to fly hundreds of miles an hour faster than Concorde but this created huge implications plane.

Kit Mitchell, who was the principal scientific officer at the then Royal Aeronautical Establishment (RAE) in the 1960s, and also worked on Concorde.

Kit said that the Boeing 2707’s main problem was that it was trying to do too much and that so much of the technology required was still in its infancy.

Military jets could fly supersonic but even then it was for only a few minutes at a time and not for 4 hour flight like the airliners were expected to. The technology required to do this in the 1960’s was as almost as much of a challenge as sending a man to the moon.

Concorde got around many of these issues because even though it flew at Mach 2, it wasn’t so fast as to require exotic materials and brand new untested designs. Concorde was effectively the next step up from the V bombers that the British had already developed.

One of the biggest issues was the extra speed that was required. Concorde flew at Mach 2.0 or 1350mph, the Boeing was meant to fly 650mph faster.

Due to the compression of the air, Many fuselage parts on the Concorde were heated to over 100C and the nose tip reached 127C when cruising at Mach 2.

The body Concorde was 300mm or about 1 foot longer at supersonic speeds than it was on the ground.

This expansion and contraction of the body could lead to metal fatigue if not carefully maintained. It also meant that Concorde had a relatively short airframe life of 45,000 hours compared 100,000 for that of a Boeing 747 and that would have an impact of the overall cost to the airlines.

Everything from the window seals to the electrical wiring had to be designed for a hot plane. Because the Boeing was going to be so much faster they could not use aluminium but instead the plane would be made from titanium which would also push up the cost dramatically.

The swing wing design which worked well on smaller two-seater fighters, when scaled up to a 300 seat airliner, needed to be so big and strong that it would make the plane too heavy.

So after a huge amount of work, the designers had to drop the swing-wing design and return to the drawing board and go back to the delta wing design of the Lockheed and Concorde.

By the time Concorde was flight testing, and the Boeing was still in the design phase, people became all too aware that the sonic boom created by these planes was going to be too much of a problem and as such supersonic flight over land was banned in most countries. This meant that the only viable routes were over the Atlantic from the east cost of the united states to the west cost of Europe.

With these with limited routes, the amount of seats that could be sold was greatly reduced and the prospect of supersonic flight was dealt a huge blow.

But what really finished the Boeing and Concorde in the end, even before the one and only crash of the Air France concorde in 2000, was the cost of fuel and travelling at supersonic speeds uses a lot of it.

With the inefficiency of jet engines at low speed, Concorde burned 2 tons of fuel just taxiing to the runway and the Boeing was also going to be very fuel hungry plane to operate.

The thinking at the time was that if you could fly to your destination in half the time you could do twice as many journeys and charge a premium, so fuel efficiency was not a top priority.

When the supersonic designs were created in the 60’s, fuel was cheap but by the 1970’s when they were due to be coming in to service, the price had risen, together the recession of 1971 and government cuts, it ended up terminating the Boeing 2707 project.

The two prototypes were never finished and with both the loss of government contracts and with the recession in the civilian aviation market, Boeing ended up cutting over 60,000 jobs.

The Boeing 2707 became known as “the airplane that almost ate Seattle.” As a result of the mass layoffs and so many people moving away from the city in search of work, a billboard was erected near Sea-Tac airport in 1971 that read, “Will the last person leaving Seattle – turn out the lights”

Ironically, the plane that saved Boeing from going bankrupt was originally thought of as a stop gap measure whilst supersonic planes took over air travel,  that plane was the Boeing 747 Jumbo jet.

Despite the project’s failure, Boeing learned a lot from the 2707 and much of this made its way into other experimental vehicles the aerospace giant built in the following decades, including some of the unmanned vehicles built in recent years.

The super-critical wing, a design tweak that came out of the 2707 project is now routinely used on modern airliners to limit shockwaves and reduce drag.

While Lockheed’s ill-fated L-2000 design will live on thanks to the collaboration between Nasa and Lockheed to fly an experimental demonstrator to research the supersonic aircraft of the future.

So Maybe in years to come, a US-built supersonic airliner will finally take to the skies.

Paul Shillito
Creator and presenter of Curious Droid Youtube channel and website www.curious-droid.com.

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