This mission, called "Good luck, have fun", is closely scrutinized because 3D printed rockets could represent a small revolution in the launch industry.
The Terran 1 rocket of the Californian company Relativity Space is scheduled to take off from Cape Canaveral, Florida. The firing window opens at 22:00 local time (02 GMT Thursday), and closes three hours later.
In total, 85% of the rocket's mass has been 3D printed, and the company is aiming for 95% in the future.
The main advantage of the technique is that the manufacturing process is greatly simplified and thus costs are reduced.
With its large 3D printing robots, the company claims to divide by 100 the number of parts compared to a traditional rocket. It also highlights the speed of the method: 60 days, from the raw material to the finished product.
Terran 1 is 33.5 meters high and just over 2 meters in diameter. Its first stage has nine engines, also 3D printed.
It will have to be able to place 1,250 kg in low Earth orbit (small satellites, for example), making it a light launcher. But this first flight does not contain a payload.
The rocket must reach, 80 seconds after takeoff, the point where the aerodynamic force exerted on the craft is highest (max Q, in the jargon). This is the crucial stage of the flight, according to the young boss of Relativity Space.
"We have already proven on the ground what we hope to prove in flight -- that when dynamic pressure and tension on the vehicle are at its highest, 3D printed structures can withstand these forces," Tim Ellis tweeted in early March.
After the first stage of the rocket separates, the second stage will have to continue its journey until it reaches Earth orbit -- 8 minutes after liftoff.
Achieving this step on the first flight would be "unprecedented," according to Tim Ellis.
Indeed, the rocket uses methalox as fuel, a mixture of liquid oxygen and liquefied natural gas (essentially methane). If it succeeds in reaching orbit, it would be the first rocket using this fuel to do so.
Relativity Space, which promotes the long-term vision of humanity living on multiple planets, argues that it is the "future" fuel, the easiest to produce on Mars.
The developing rockets Vulcan, from United Launch Alliance (ULA), and Starship, from SpaceX, must also use this fuel.
A first attempt to launch Terran 1 was abandoned on March 8 due to a fuel temperature problem.
Then, on March 11, takeoff was cancelled twice in the final seconds of the countdown, first because of an automation problem, then because of a fuel pressure problem.
Regardless of the degree of success of the maiden flight of Terran 1, the data collected will also be used for the development of its big sister: Terran R.
This largest rocket, also developed by Relativity Space, should be able to carry 20,000 kg to low orbit.
The company has already signed $1.65 billion worth of contracts, the majority for Terran R, according to Tim Ellis.
One of them was with the company OneWeb, whose constellation of satellites is to provide internet from space.
This type of rocket "medium-heavy is clearly where the most important market opportunity for the rest of the decade lies, with a huge shortage currently in this class of payload," Tim Ellis tweeted.
A satellite operator can wait years to get a place in Arianespace's or SpaceX's big rockets.
Dozens of start-ups have therefore launched in recent years to meet a booming demand.
The number of satellites launched has increased from about 120 in 2012 to more than 2,700 in 2022, according to the specialist company Euroconsult.
© 2023 AFP