It was built for and won the Rainhill Trials of the Liverpool and Manchester Railway (L&MR), held in October 1829 to show that improved locomotives would be more efficient than stationary steam engines.

Although he was in frequent contact with his father in Liverpool and probably received advice from him, it is difficult not to give the majority of the credit for the design to Robert.

As the first railway intended for passengers more than freight, the rules emphasised speed and would require reliability, but the weight of the locomotive was also tightly restricted.

[13] Robert Stephenson was able to report to Henry Booth on 5 September 1829 that Rocket[a] had performed initial manufacturer tests with flying colours at Killingworth.

[17] No other locomotive at the trials could match anything like Rocket's performance reliably, with partners Booth and Stephensons sharing the £500 winnings and showing that stationary engines were unnecessary, with sceptics such as Rastrick being convinced.

[18] The opening ceremony of the L&MR on 15 September 1830 was a considerable event, drawing luminaries from the government and industry, including the Prime Minister, the Duke of Wellington.

The day was marred by the death of William Huskisson, the Member of Parliament for Liverpool, who was struck and killed by Rocket at Parkside.

The cylinders were altered to a near-horizontal position, compared to the angled arrangement as new; the firebox capacity was enlarged and the shape simplified; and the locomotive was given a drum smokebox.

On 22 October, of that year, an operational trial was held with disappointing results; one witness observing, that "the engine could not be made to draw a train of empty carriages".

The locomotive had a tall 16 ft smokestack chimney at the front, a cylindrical boiler in the middle, and a separate firebox at the rear.

Previous locomotive boilers consisted of a single pipe surrounded by water (though the Lancashire Witch did have twin flues).

Rocket had 25 copper[33] fire-tubes that carried the hot exhaust gas from the firebox, through the wet boiler to the blast pipe and chimney.

This arrangement resulted in a greatly increased surface contact area of hot pipe with boiler water when compared to a single large flue.

By 1830, Stephenson's past employee Timothy Hackworth had re-designed his return-flued Royal George as the return-tubed Wilberforce class.

[34] Rocket also used a blastpipe, feeding the exhaust steam from the cylinders into the base of the chimney so as to induce a partial vacuum and pull air through the fire.

[9] Like the Lancashire Witch, Rocket had two cylinders set at angle from the horizontal, with the pistons driving a pair of 4 feet 8.5 inches (1.435 m) diameter wheels.

[36] Most previous designs had the cylinders positioned vertically, which gave the engines an uneven swaying motion as they progressed along the track.

Again like the Lancashire Witch, the pistons were connected directly to the driving wheels, an arrangement which is found in subsequent steam locomotives.

These early fireboxes formed a separate water space from the boiler drum and were connected by prominent external copper pipes.

[39] Two years later, the replica was used again in the Al St. John film, The Iron Mule, directed by Keaton's mentor, Roscoe "Fatty" Arbuckle.

In 1979, a further, working replica Rocket was built by Locomotion Enterprises in the Springwell workshops at the Bowes Railway for the 150th anniversary celebrations.

[48] It has a shorter chimney than the original to clear the bridge at Rainhill: successive additions of ballast and heavier rail have raised the track, leaving less headroom than in the 19th century.

In 2020, Hornby announced a newly tooled 00 Gauge model of Stephenson's Rocket with three coaches and crew members as part of their Centenary range.

It was available as a standard model and a limited edition with commemorative certificate of authentication in retro 1963 Hornby Centenary Tri-ang Railways packaging.