America's SpaceX company has conducted a key test ahead of the maiden flight of its new rocket – the Falcon Heavy.
In what is known as a static firing, all 27 engines on the launcher's first stage were ignited together to check they are flight-ready.
The procedure, conducted in Florida, lasted only seconds and the rocket was clamped to keep it on the ground.
The Falcon Heavy will be the most powerful launcher in the world when it eventually lifts off.
Depending on the analysis of Tuesday's test, that could occur before the end of the month.
SpaceX, however, has taken a very deliberate approach to the development of the Falcon Heavy, and will only authorise a launch when its engineers are entirely happy.
The possibility of a second static test at the Kennedy Space Center is not out of the question if something is seen in Wednesday's data that requires further study.
The Falcon Heavy is essentially three of SpaceX's workhorse Falcon 9 vehicles strapped together.
But the triple-booster configuration has demanded a number of specific alterations, including a strengthening of the central core booster.
The 27 Merlin engines at the base of the rocket should be capable of generating almost 23,000 kilonewtons of thrust – slightly more than double that of the world's current most powerful rocket, the Delta IV Heavy, which is operated by US competitor United Launch Alliance.
The 70m-tall Falcon Heavy is designed to put up to a maximum of 64 tonnes in low-Earth orbit, although in reality it will be rare that the vehicle lofts that much mass.
SpaceX intends to land the rocket's boosters back on Earth after launch – as is the company's usual practice today with the Falcon 9 – and that necessarily negates some performance.
But the new capability would mean the firm in future has no difficult launching the biggest military and commercial telecommunications satellites – and still recover all three first-stage boosters.
The introduction of the rocket should also open up some fascinating possibilities to send much bigger payloads beyond Earth orbit than is currently possible. This could include sending astronaut capsules to the Moon, or bigger robots to Mars.
Because the maiden flight of any rocket carries a higher degree of risk, the Falcon Heavy will not take up a meaningful payload when it finally launches.
Instead, SpaceX CEO and chief designer Elon Musk has decided to put his old sportscar on the top of the Falcon Heavy. His idea is to send this red roadster towards the orbit Mars takes around the Sun.
Jonathan.Amos-INTERNET@bbc.co.uk and follow me on Twitter: @BBCAmos