A Closer Look At The Future of 3D-Printed Rockets
Over at Relativity Space, the company is now entirely focused on the development, manufacturing, and testing of the Terran R launch vehicle. While at first, the company was primarily working on the Terran 1 rocket, with its maiden flight complete, Relativity has officially moved on and retired the small lift vehicle. They learned a lot of valuable lessons primarily in the manufacturing process and are now applying these skills to the next rocket.
However, going from an expendable 3D-printed rocket that’s 110ft (34m) tall to a reusable 270ft (82m) tall 3D-printed rocket is a big change. So big that despite the experience gained from Terran 1, Relativity now faces a host of new challenges throughout the development process. With this in mind, the company has already made some significant progress on major components and even infrastructure.
This includes new factories, Aeon R engine tests, and new large printers, just to name a few. Here I will go more in-depth into the design of this rocket, Relativity’s 3D printing goal, what to expect in the coming months, and more.
Terran R’s Plan
Originally, when Terran R was first announced, Relativity provided graphics and information on the capabilities of this system. The company had an idea of what they wanted, but weren’t exactly sure the design or even application of this next-generation rocket. This was the case up until a big update and redesign to practically the entire system.
In its current state, Terran R will be a partially reusable, 3D printed, medium-to-heavy lift orbital launch vehicle. In a company statement Relativity said, “Building on over seven years of Relativity Space’s experience, learnings, and momentum gathered through its Terran 1 program – the world’s first 3D printed rocket to fly and reach space – Relativity is accelerating the company’s focus on Terran R to meet significant and growing market demand. Terran R also represents a large leap towards Relativity’s mission to build humanity’s multiplanetary future, eventually offering customers a point-to-point space freighter capable of missions from the Earth to the Moon, Mars, and beyond” they said.
Looking at the two vehicles, the technologies created throughout the Terran 1 program were intentionally envisioned to build direct experience relevant to Terran R. This approach was not the easiest path to get Terran 1 to the launch pad – as an ambitious first vehicle – but it hoping to enable Relativity’s team to capitalize on a significant experience base while executing Terran R.
Foucsing on the Terran R system, as a two-stage, 270-foot-tall rocket with an 18-foot diameter and a 5-meter payload fairing, Relativity describes Terran R as a customer-centric next generation launch vehicle designed to meet the needs of commercial companies and government entities sending payloads into LEO, MEO, GEO, and beyond.
Terran R will prioritize first stage reusability, with the capability of launching 23,500kg to Low Earth Orbit (LEO) or 5,500kg to a Geosynchronous Transfer Orbit (GTO), both with downrange landing, or up to a maximum payload of 33,500kg to LEO in expendable configuration. Horizontal integration to the vehicle will be supported through a standard Payload Attach Fitting (PAF) interface, with payload integration configurations available for clusters of constellation satellites, single large satellites, or other unique spacecraft. While the company originally planned to launch this rocket in 2024, they have since moved that date back to a more realistic 2026 estimate.
Designed for rapid reusability and development iteration speed, Terran R is a 3D printed rocket, with initial versions using aluminum alloy tank straight-section barrels in a hybrid manufacturing approach, which allows Relativity to meet the rapid launch and ramp rate timelines necessary to serve overwhelming market demand, including servicing Relativity’s signed customer backlog of $1.65B in Launch Service Agreements (LSA’s) and additional several billion dollars in active customer LSA dialogue.
To put the size of this rocket in perspective, each Terran R requires approximately 6 times more 3D printing by mass than Terran 1. 3D printing technology for Terran R is strategically used to reduce vehicle complexity and improve manufacturability, with continued company focus on redefining what is possible with large scale additive manufacturing. Initially, Terran R will use the same proprietary printed aluminum alloy as flown on Terran 1 with a focus on supply chain scaling. However, a third-generation aluminum alloy, designed for improved performance of an orbital vehicle mission life beyond 20 reusable flights, is in active development.
Next-Generation Design
Starting at the bottom, Terran R’s first stage will be outfitted with 13 3D-printed gas generator cycle Aeon R LOx/Methane rocket engines each capable of 258,000 lb. sea level thrust. The engine composition on the first stage is comprised of four outer fixed engines aligned underneath four landing legs, and nine center gimbaled engines, providing enhanced reliability on vehicle ascent with engine-out capability. On both Terran R stages, the LOx propellant tanks are forward of the methane tanks, separated by a printed common dome. Subcooled cryogenic propellants are used on all parts of the vehicle except for the first stage liquid oxygen system, where subcooling is not necessary to meet performance goals. Both stages use a cryogenic helium pressurization system to enable better press authority when engines are not turned on by reducing ullage collapse. The vehicle also features an in-house developed pneumatic pusher stage separation system.
Shortly after stage separation, the first stage of Terran R will perform a slow flip maneuver using its cold gas Reaction Control System (RCS). Grid fins deploy, followed by igniting engines to complete entry burns, slowing velocity and reducing peak loads and heating. The vehicle design is meant to result in a more stable entry profile with controlled flow separation around the vehicle. Terran R is working toward atmospheric entry with grid fin control. The vehicle will then ignite engines for a landing burn and command the leg slider mechanism to open, which will then passively deploy with the aid of aerodynamics. The first stage will then touchdown on a downrange ship in the ocean. Once the first stage has completed its reentry, it will go for inspection, refurbishment, and recertification for its next flight from Cape Canaveral.
In order for this to be possible, Terran R features two near body-length aero strakes, four unique slider-mechanism landing legs, and four printed actuating grid fins. These features are meant to optimize first stage reusability, enabling rapidly scaled launch cadence for customers together with greater payload to orbit and lower costs versus other reusable architectures. Terran R’s first stage architecture is meant to allow for a high angle of attack reentry, reducing propellant required for reentry burns, aerodynamic design for better reentry stability and improved control authority, and a passively actuated landing leg deployment system which they describe as elegantly simple, lightweight, and highly operable for rapid reuse.
An 18-foot vehicle diameter also aids vehicle stability with lower requirements on landing legs. Terran R will have an electromechanical actuator (EMA)-based engine thrust vector control (TVC) system, and also use EMA’s for grid fin control, in addition to in-house developed avionics and flight software. Additionally, the vehicle features a reentry heat shield on the aft end designed for rapid reusability.
In order for this rocket to not only provide a decent payload capacity but also reuse the first stage, the Aeon R engines need to be extremely powerful and also capable of throttling. So far this component has been the main area of focus with consistent updates from the company. Most recently on the 30th Relativity CEO Tim Ellis tweeted in response to a Aeon R engine fire saying, “Crazy this single engine has 25% more thrust than all 9 combined for Terran 1. It’s a beast and 13 of these for Terran R will be insane during launch and landing!” By now the company has completed a bunch of static fires and tests, even including throttling from 95 to 65 percent thrust.
Already a focus of significant development and testing efforts for the last two years, Aeon R benefits from the heritage of its smaller predecessor, Aeon 1. Migrating many of the same propulsion system architecture decisions from Aeon 1 to Aeon R has unlocked a high rate of iterative design and fast-tracked much of the Aeon R test program. Since mid-2022, Relativity has been underway testing all Aeon R combustion devices at NASA Stennis Space Center – including the main Thrust Chamber Assembly (TCA), gas generator (GG), and gas-gas ignition system – at full scale and 100% power with high combustion efficiency. All engine active valves are developed in-house, with all valves produced, successfully actuated, and in development testing. In February 2023, the company completed its first full build of an Aeon R engine, since then, testing has only ramped up.
Conclusion
Relativity Space has big plans for the future with Terran R. Not only will this rocket be massive and partially reusable, but also entirely 3D printed. We will have to wait and see how it progresses and the impact it has on the space industry.