Those Fabulous Jet-Powered Firebirds
by T. L. Stone

Harley Earl, GM chief of styling and originator of "longer, lower, wider," was a visionary designer. He gave the automotive world tail fins, demonstrated that cars could be made lower and still have enough room for a man wearing a hat, and believed that oblongs were naturally more interesting and attractive than squares.

Earl was also influenced by the world around him, and nothing in 1953 excited him quite as much as the newest, postwar generation of jet airplanes. One which particularly interested him was the Douglas Skyray pictured above.

Could he, he wondered early in 1953, design a test vehicle that would capture the "feeling" of the Marine attack plane? It would have be a working vehicle. It would have to be a test-bed for GM's most modern and ambitious projects. And, of course, it would have to be jet-powered.

Jets were almost magic in 1953. No other type of machine, other than a rocket (or a bomb) can equal a gas turbine's power to weight ratio. A turbine powerplant also has a lower part count compared to, say, a V-8 piston engine.

Well, it just so happened that GM had a department working on developing gas turbines for buses. The engine was called the GT-300, and engineers thought that it could be road-tested in a GM coach by 1955.

Fine, said Earl (or something similar), slim it down a bit to fit in a car, and I'll design the car for it.

Yes, sir, said the engineers, and then they probably cringed.

The car was to become the XP-21, America's first turbine-powered passenger vehicle. GM Research constructed the chassis. Engineering provided the brakes, transmission, and other essential controls. Earl's own styling department designed and crafted the sleek fiberglass body.

The car was ready by late in 1953.

Mauri Rose, three-time Indianapolis 500 winner, drove the car at GM's Arizona proving grounds. This quotation is from the April 1954 issue of Motor Life:

"I noticed the utter lack of vibration. As an engineer I was well aware of the fact that a turbine, with no reciprocating moving parts, probably is the smoothest power package in motion. It is."

"The smoothness made me conscious of the car's chassis and suspension. In other words, the lack of vibration - vibration was something I had become accustomed to in years of race and test driving - left me free to think of other things."

"It was like being accustomed to working in a room with a clock ticking - and then have the clock stop ticking. It was a little confusing for a moment. It was contrast."

"... a turbine-driven car has characteristics definitely different than a piston engine car. The engine idles at 8,000 rpm, but one can control the car at any speed from zero on up. However, the car continues to cruise right along when you close the throttle. Compression deceleration isn't there."

The XP-21 had some disadvantages. It was noisy, hot, and demonstrated some rather poor fuel economy (which GM did not publicize), but the experiment was seen as being worthwhile.

Work continued on the XP-21, and variations.

By 1956, GM marketing was continuing the popular "Motorama" concept, which was a traveling car show intended to increase interest in (and purchases of) GM products.

One of the show cars had a body made of titanium. Dubbed the Firebird II, it featured an "electronic brain" that would operate the car's steering system. It had a new engine, the revised GT-304 "Whirlfire." A regenerator section in the turbine engine recovered waste heat as well as improving fuel economy (which was still unpublished). A crowd-pleasing feature was the installation of "conic silencers" in the engine intakes (visible in the photo below), which would allow the machine to operate in polite neighborhoods.

Soon, a Firebird would drive itself.

Here's how it happened. In 1958 GM Engineers working on the experimental "Autoguide" system buried a cable in the test track at the GM Technical Center in Detroit. Then they mounted a pair of antennae on the bottom of the front bumper of a test vehicle (the original "curb feelers?") and adjusted the car's analog computer to keep the steered course over the cable. After a couple of weeks of testing, it more or less worked.

So they called the press. "Look, ma - no hands!" The press loved it.

Hmm, thought the engineers. Their demonstration car steered nicely, but could they make their control computer also deal with braking and acceleration?

A few months later, they had that working. The test chassis had no steering wheel, but it had a small, side-mounted control stick that operated the car's steering, throttle, and brakes.

GM had invented the first "fly-by-wire" automotive application. They called it "Unicontrol."

A forward push of the control stick accelerated the car, while a rearward pull applied the brakes. Lateral movements operated the car's steering. The engineers even built "speed sensitivity" into the system, to prevent inputting large control changes that might put the car into an uncontrolled spin at speed. (And, if you're wondering, one rotated the knob to the left to select reverse).

Another innovation was called "Cruisecontrol," without a space in between, which is understandable somewhat when one considers that the other part of the Unicontrol system, the guide wire-following part, was called "Autoguide."

Meanwhile, Harley Earl had moved on. Now rockets had seized his imagination. His team was at work on a new Firebird concept car which would include the latest variation of the gas-turbine engine and the Unicontrol System. A press release described the new Firebird as a car "which a person may drive to the launching site for a rocket to the moon."

Now, just guess what this car would look like!

Here it is in denuded form:

The Firebird III first "flew" in August 1958, again at the Desert Proving Grounds in Arizona. An interesting feature of the new design was the incorporation of a completely separate accessory motor which produced 10-bhp to operate the car's hydraulics and electrical systems. This arrangement left the entirety of the main engine's output to propel the car.

And here it is with its clothes on:

These three vehicles still exist, and they are sometimes shown at automobile concourse events.

To visit the definitive site for the jet-powered Firebirds, containing many articles and photographs of all three Firebirds, as well as an online reprint of the Mauri Rose article mentioned above, go to Conklin Systems - the Firebird Pages. (Emmett Conklin was a test driver and engineer for GM. He drove the XP-21 before Mauri Rose and was involved in the design and testing of all the turbine-powered Firebirds.)

Copyright © 2002 T. L. Stone
All rights reserved

Images: Skyray, McDonnell-Douglas Cars: General Motors Corporation

Flights of fancy, rendered in fiberglass and steel. Concept cars capture our attention and, sometimes, our imagination. Thanks for reading this.