Relativity Space Terran 1 “Good Luck, Have Fun” Launch

Relativity Space plans the first launch of their Terran 1 small satellite launcher on 2023-03-23 in a three hour launch window between 02:00 and 05:00 UTC (the window opens late in the evening of March 22nd in western hemisphere time zones). The code name for the mission is “Good Luck, Have Fun”. As a test launch, no payload is on board other than a 1.5 kg metal ring, which will be placed in a 200×210 km low Earth orbit at 28.5° inclination. For this flight, the rocket is not equipped with a jettisonable payload fairing, and both the fairing and payload will remain attached to the second stage of the rocket if and when it reaches orbit. Launch will be from Space Launch Complex 16 at Cape Canaveral Space Force Station in Florida, the first launch from that site since it was last used for Pershing missile tests in 1988. Weather is forecast as 90% favourable for launch.

Relativity Space and its Terran 1 rocket were described here in a post on 2022-03-31, “Relativity Space—3D Printing an Orbital Launcher”. If it successfully reaches orbit, Terran 1 will be the first rocket powered by liquid methane/oxygen engines to do so, beating United Launch Alliance, SpaceX, and Blue Origin to that milestone. Both the rocket and its ten Aeon 1 engines (nine on the first stage, one on the upper stage) are made by additive manufacturing (3D printing), with around 90% of the launcher (by mass) consisting of 3D printed components. The company claims this reduces part count on the vehicle by a factor of 100 compared to conventional construction. Payload capacity is stated as 1250 kg to low inclination low-Earth orbits and 900 kg to Sun-synchronous orbit; as noted, this test mission will carry no payload. The advertised cost per launch is US$ 12 million.

Here is a pre-flight preview from Everyday Astronaut.


Today’s launch attempt was scrubbed after initially counting down to the 70 second mark where the automatic launch sequencer cut off due to the liquid oxygen temperature in the second stage being out of specified limits. After a delay to analyse the problem, the countdown was reset to 45 minutes to launch and resumed. With 23 minutes to go in this second attempt, the scrub for the day was announced. As of the end of the Webcast, the date and time for the next launch attempt had not been announced.



For who don’t think in quaint U.S. time zones, that’s 18:00 to 21:00 UTC on 2023-03-11.


The second launch attempt is on for 2023-03-11 in a three hour window starting at 18:00 UTC. I have updated the main post with the new date and time and a live player for the launch.


After an extended hold waiting for winds aloft to abate, the countdown went to almost to the T−70 second mark when it was halted due to a “fouled range”—a boat had strayed into the exclusion zone. After the boat had moved on, they resumed the countdown, lit the engines, then aborted the launch a half second before liftoff.

After this attempt, they evaluated the situation and decided to try again, recycling the countdown aiming for a liftoff right at the end of the launch window. They counted down toward that, and then the automatic sequencer stopped the countdown at T−45 seconds. That meant missing the window, so the launch attempt was scrubbed for the day.

We’ll have to wait and see what they have to say about what went wrong and when they’ll try again.

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SpaceX has spoiled us – making us forget just how difficult launching a rocket really is. So many things that can go wrong and cause a launch abort.


The third launch attempt is proceeding toward a launch on 2023-03-23 in a three hour launch window between 02:00 and 05:00 UTC. I have updated the main post with the new launch time.

Weather is forecast as 95% favourable for launch.


Fantastic visuals on the main engines approaching max-Q. Well done, Relativity Space!

Looks like stage two is a bust, though.


After delays due to high winds aloft and a boat straying into the exclusion area offshore (Why don’t these boats ever delay SpaceX launches? Oh, I forgot Elon’s orbiting laser battle stations.), the Relativity Space Terran 1 launched normally. Cue the replay video in the main post to 1:20:58 to pick up the countdown at one minute before liftoff.

The flight proceeded normally through the point of maximum dynamic pressure (max-Q), considered a major milestone for the 3D-printed airframe to survive. At 1:24:46 the video switched to an on-board camera showing the second stage engine after what appeared to be a normal stage separation. There were flashes of flame from the engine but nothing that looked like ignition and a normal exhaust plume. The velocity started falling immediately after this point and continued to fall as the rocket ascended, presumably following a ballistic trajectory imparted to it by the first stage. At 1:26:56 an announcement was made by the launch director that there had been an “anomaly with stage 2”.

Judging from the video, it looks like stage separation was successful, and there was no apparent damage to the second stage engine, but it failed to complete the start process and deliver thrust. “Air start” of a rocket engine in flight is always a challenge. The U.S. Atlas and Soviet R-7 ballistic missiles were both designed to start all their engines on the launch pad and drop expended boosters in flight to avoid having to solve this problem. See the post here on 2023-03-10 “How Do You Start a Rocket Engine?” and cue to the 32:39 point “Starting a Rocket Engine in Space” for a discussion of the additional difficulties this involves. Some of these cannot be simulated on the ground and must be tested in flight, for example, settling the propellants to the bottom of their tanks so they feed into the engine’s pumps (“ullage”). An in-flight start does not have access to the ground support equipment typically used by first stage engines to start, and must rely upon on-board resources that may behave differently in weightlessness and a vacuum.

Whatever happened, the rocket followed a ballistic trajectory and impacted the ocean downrange. Relativity Space thus missed this opportunity to become the first liquid methane/oxygen rocket to reach orbit, but the apparently flawless performance of the first stage engines from launch to cutoff is a vindication of the propellants and the 3D-printing process used to manufacture them.

The colour of the exhaust plume during the night launch was striking. Here is a time exposure of the launch by photographer John Kraus.

Note how the plume starts out almost white, then becomes reddish as the rocket ascends, and finally shades to a pure blue like the flame on a natural gas stove. My guess is that this is due to unburnt methane in the exhaust plume (because the engines, like essentially all rocket engines, run fuel-rich to reduce temperatures in the combustion chamber and nozzle and improve specific impulse [because the fuel has a lower molecular weight than the oxidiser]) interacting with oxygen in the atmosphere. During the first part of the ascent, the hot methane (CH₄) is burning in the ambient oxygen with a bright carbon flame. As the rocket climbs, this combustion becomes increasingly oxygen-starved as the atmosphere thins, leading first to a reddish plume (Why? I haven’t a clue.) and then the pure blue flame of combustion of the on-board liquid oxygen with methane, with the excess methane being invisibly expelled into the near-vacuum. It will be interesting to see if other methane/oxygen rockets such as ULA’s Vulcan and SpaceX’s Starship also make similar “rainbow plumes”.

The flight didn’t go as well as Relativity Space may have hoped, but it certainly checked off a long list of goals which had never been tested in flight. Once they figure out what happened to the second stage, they should be ready to try again.


Shhh! Don’t let the Global Warm-mongers know that this rocket expels uncombusted methane into the high atmosphere. One of them may know enough about science to recognize that a methane molecule has a much larger “greenhouse effect” than a mere carbon dioxide molecule. Then the rocket may never fly again.

On the other hand, those same Global Warm-mongers had no concern about Biden* blowing up the German/Russian NordStream pipelines and releasing massive quantities of methane into the atmosphere. So maybe I am worrying unnecessarily.



Nine engines burning methane and liquid oxygen! This was taken moments after liftoff—the debris is ice shed from the propellant tanks due to vibration from the engines. This close to the engine nozzles, the plume is the light blue of methane completely burning at high temperature in oxygen. Further down the plume, as it begins to mix with atmospheric oxygen, the plume glows yellow-white with carbon from unreacted methane glowing from the heat.


Here is Scott Manley’s analysis of the Terran 1 launch attempt. His take on the colour changes in the exhaust plume during ascent is the same as mine.