Relativity Space is moving on from the Terran 1 rocket to something much bigger

Relativity Space made a flurry of announcements on Wednesday about its past and future. The company is going bigger, and it has already started to do so.

In an interview with Ars, the company's chief executive, Tim Ellis, discussed the cause of its Terran 1 launch failure and lessons learned for the future and looked ahead to big changes planned for the company's next launch vehicle.

Foremost among these changes is the plan to move directly into development of the Terran R rocket. In response to customer demand, Ellis said, this rocket is getting even bigger than before. A fully expendable version will now be able to lift a staggering 33.5 metric tons. This sets up Relativity to compete directly with the largest players in the global launch industry.

"It's a big, bold bet," Relativity Space Chief Executive Tim Ellis said in an interview. "But it's actually a really obvious decision."

Terran 1

The company's first rocket made its debut launch on March 22, and the first stage performed as expected, with a nominal stage separation. However, at 2 minutes and 48 seconds into flight—two seconds after ignition of the second-stage Aeon engine—the engine did not achieve full thrust.

Relativity's investigation of the failure is ongoing, but Ellis said that when the Aeon engine's main valves were commanded to open, they opened slower than expected. There was also a problem with the oxygen pump, likely due to a "vapor bubble" at its inlet. As a result of all this, the engine's gas generator did not light, and the engine never reached full power.

The second stage would reach an altitude of 134 km before it reentered Earth's atmosphere and landed harmlessly in the Atlantic Ocean. Ellis said Relativity obtained good data from the second stage all the way through the reentry process.

The company feels good about the data collected from the flight, as Terran 1 made it further into space than the debut launches from a majority of small rocket companies. It also validated the company's test and launch program, he said, and its approach to 3D printing large parts of a rocket.

"Terran 1 was always meant to develop technologies that were pushing the bounds for what was needed for Terran R," Ellis said.

But now, it's time to move on. Relativity Space is negotiating with NASA to move the one existing commercial launch on Terran 1—the Venture Class Launch Services Demonstration 2 mission—onto another rocket, possibly the Terran R. In other words, there will be no more Terran 1 launches.

Terran R

And so Relativity Space is pivoting, hard, to a much larger rocket. The company began discussing the Terran R concept nearly two years ago and has spent considerable time since then refining the rocket's design. The new plan for the Terran R is significantly changed from what was first announced in June 2021:

• The second stage will now be expendable, at least for several years, because it does not make economic sense to fly these stages back, Ellis said. The mass penalty in terms of propellant was just too high. One day the company may fly a fully reusable vehicle.
• There will be a version of Terran R with a fully reusable first stage, capable of 20 re-flights. It will have a payload capacity of 23.5 metric tons to low-Earth orbit. Additionally, an expendable version of the Terran R rocket will carry 33.5 metric tons to low-Earth orbit. This places the vehicle firmly into the class of "heavy lift" rockets.
• Relativity is moving away from an approach to additively manufacturing the entire Terran R rocket. Ellis said the Terran R will still be a "3D printed rocket," but initial versions (at least) will use aluminum alloy straight-section barrels. This is necessary, he said, to serve "overwhelming market demand" for a vehicle of this size.
• The rocket will now be powered by 13 Aeon engines, instead of a cluster of seven. This will give the rocket an enormous amount of thrust, 3.35 million pounds. This is comparable to that of Blue Origin's New Glenn rocket, which has 3.85 million pounds, and a version of United Launch Alliance's Vulcan rocket with four boosters, which has 3.1 million pounds of thrust.
• First-stage reuse plans look similar to a Falcon 9 first stage, with grid fins and multiple engine burns to control re-entry. The rockets will land on a drone ship in the Atlantic Ocean and be refurbished at Relativity Space's facilities at Cape Canaveral Space Force Station in Florida.
• Instead of targeting an aspirational launch date of 2024 for the Terran R, Relativity Space now has a realistic goal of launching the rocket in 2026.

There are many changes here, but one of the biggest is moving away from the goal of a fully reusable launch vehicle.

"I'm calling it a prioritization of first stage reuse just because the economic benefit is so much greater," Ellis said. "And since we need to get into market, and get to a higher ramp rate as quickly as possible, it just made sense to focus company resources on that. It's a much more pragmatic initial solution."