Rocket and spacecraft manufacturer SpaceX’s Starship prototype has exploded during test-firing at its private launch site in Boca Chica, Texas, US.

Named as SN4, this full-size experimental vehicle was the fourth version of SpaceX’s fully reusable rocket programme designed for affordable human space travel.

The explosion occurred during an operation to test-fire its Raptor rocket engine. It is expected to have been caused due to a fuel leak.

The 394ft-tall rocket is designed to ferry humans and 100t of cargo to the Moon and Mars.

SN4 had completed the cryogenic pressure test on 26 April and conducted a test firing last month equipped with a Raptor engine.

The vehicle was also put through hot-fire tests prior to test-firing on Friday.

Besides SN4, the company’s three previous Starship prototypes also failed. Meanwhile, the company is working on additional prototypes. SN5 is currently under assembly stage.

Nasa awarded SpaceX and two other companies a combined $1bn to develop rocket systems capable of ferrying cargo and humans to the Moon.

The company is developing the system to fly passengers around the Moon in 2023 and land Nasa astronauts on the lunar surface by 2024.

The US Federal Aviation Administration has also granted SpaceX a licence to begin Starship’s first suborbital flight tests.

In a separate development, First SpaceX Crew Dragon with two Nasa astronauts arrived at the International Space Station.