Austrian physicist Ernst Mach (1838-1916) was the first to note that as an aircraft approaches the speed of sound, shockwaves build up in front of the nose and present a physical barrier that an aircraft has difficulty passing through. This is called the sound barrier. Though both designs had to address the effects of this 'compressibility' factor, the DH 108 and the X-1 were two fundamentally different aircraft.

Specifications

			Bell X-1		De Havilland DH 108
	Length		9.44 metres		8.16 metres
	Wingspan		8.53 metres		11.88 metres
	Engine		Liquid-fuelled four-chamber rocket		Goblin IV jet
	Maximum speed		Mach 1.06		Mach 1

Mach 1 = speed of sound

Design

The British De Havilland DH 108 design was at the forefront of jet development. It was fitted with revolutionary swept wings, which assisted in lessening compressibility factor. The wings were also found to improve the effects of drag and add stability in super fast flight. The aircraft's overall design was based on an existing Vampire jet fighter's fuselage, though drastically changed to omit the original double body and tail fins. However, the DH 108 was still a jet.

The X-1, however, was constructed as an experimental aircraft (hence the 'X' designation) to investigate transonic flight. Unlike a traditional jet, the X-1 was basically a rocket or manned missile. The design was heavily influenced by observations of the incredibly stable 50-calibre bullets in ballistic tests. The resulting fuselage design looked remarkably like an up-scaled bullet with small straight wings. Where the British had gone for the latest jet design and engine, the Americans had opted for extreme power and had based their plane on a rocket.

Engines

The basic principle of the jet engine is to accelerate a small mass of air at an incredibly high velocity. Air enters the front of the engine and is compressed by a series of fans. Fuel is introduced to the compressed air and ignited in a central combustion chamber resulting in a massive boost of energy. This power is then vented out the back of the engine where it provides colossal thrust (and also drives turbines to turn the frontal compression assembly).

With the Goblin IV jet at full power the DH 108 could produce nearly 4000 pounds of thrust.

The X-1 used a rocket that burnt liquid fuel for its incredible power. A rocket basically works by managing a controlled explosion. With the X-1, test pilot Chuck Yeager could ignite and shut off four rocket chambers. The craft was dropped from a mother ship aircraft (a B29 bomber) and then fired. With all four chambers blasting, Yeager broke the sound barrier on 14 October 1947 with over 6000 pounds of thrust. What a ride!