Launch day timeline for Relativity Space’s Terran 1 rocket

EDITOR’S NOTE: Updated March 22 with new launch date.

Relativity Space’s Terran 1 rocket on Launch Complex 16 at Cape Canaveral Space Force Station. Credit: Relativity Space / Trevor Mahlmann

Relativity Space’s 10-story-tall Terran 1 rocket will encounter the most extreme aerodynamic forces of its eight-minute test flight around 80 seconds after liftoff from Cape Canaveral. That’s a key moment when the company’s engineers hope to confirm the 3D-printed rocket can withstand the rigors of launch.

The expendable Terran 1 rocket is set to blast off from Launch Complex 16 at Cape Canaveral Space Force Station during a three-hour window opening at 10 p.m. EDT Wednesday, March 22 (0200 UTC Thursday, March 23). Forecasters expect good weather for the launch of Relativity Space’s first rocket.

Read our mission preview story for details on Relativity Space and the Terran 1 test flight.

The 110-foot-tall (33.5-meter) rocket will be powered up for final pre-flight checkouts early Saturday.


• T-minus 7 hours: Vehicle power-up and checkouts

• T-minus 4 hours: Personnel clear the launch pad; Methane and liquid oxygen loading begins

• T-minus 60 minutes: Propellant loading complete

• T-minus 16 minutes: Launch director performs pre-launch readiness poll

• T-minus 10 minutes: Automated countdown sequence begins

In the final 10 minutes of the countdown, the Terran 1 rocket’s nine methane-fueled Aeon 1 engines will be thermally conditioned for flight through a procedure known as chilldown. The ignitors will be primed, and the Terran 1 will switch from its ground power supply to internal power. The strongback at the launch pad will be partially retracted in the final minutes before launch.

• T-minus 1 minute, 10 seconds: Terminal countdown begins to run checks for launch commit criteria

• T-minus 6 seconds: Ignition of Terran 1’s nine Aeon 1 main engines; Automated health check begins

• T-minus 0 seconds: Four hold-down devices release the Terran 1 rocket for liftoff

Credit: Relativity Space


• T+plus 0 seconds: Liftoff of the Terran 1; Nine Aeon 1 engines producing 207,000 pounds of thrust

• T+plus 12 seconds: Engine thrust vector controllers begin pitching the Terran 1 rocket downrange

• T+plus 1 minute, 20 seconds: Maximum aerodynamic pressure

• T+plus 2 minutes, 40 seconds: First stage main engine cutoff

• T+plus 2 minutes, 45 seconds: Terran 1’s 80-foot-long first stage separates from the second stage

• T+plus 2 minutes, 51 seconds: Ignition of Aeon Vac engine producing 25,400 pounds of thrust

• T+plus 7 minutes, 43 seconds: Second stage engine cutoff

• T+plus 8 minutes: Terran 1 in orbit

The Terran 1 rocket fires nine methane-fueled Aeon main engines during a hold-down test-firing at Cape Canaveral. Credit: Relativity Space

ROCKET: Terran 1

PAYLOAD: “Good Luck, Have Fun” test flight; No customer payload

LAUNCH SITE: LC-16, Cape Canaveral Space Force Station, Florida

LAUNCH DATE: March 22/23, 2023

LAUNCH WINDOW: 10:00 p.m. – 1:00 a.m. EDT (0200-0500 GMT)

WEATHER FORECAST: 95% chance of acceptable weather



TARGET ORBIT: 124 miles by 130 miles (365 kilometers by 373 kilometers), 28.5 degrees inclination


  • 1st launch by Relativity Space
  • 1st launch of Terran 1 rocket
  • 151st launch from Launch Complex 16
  • 13th orbital launch attempt based out of Cape Canaveral in 2023

Email the author.

Follow Stephen Clark on Twitter: @StephenClark1.