From: veritasium
Relativity Space, a startup, has developed the world’s largest 3D metal printer with the aim of printing an entire rocket, including fuel tanks and rocket engines, in just 60 days [00:00:00]. This approach represents a significant shift from traditional aerospace manufacturing methods.
Traditional Rocket Manufacturing
Traditionally, rockets are enormous, complex engineering projects manufactured using conventional techniques [00:03:25]. This often means that before a rocket can be built, the specialized tools to build it must first be constructed [00:03:33].
For instance, to build NASA’s Space Launch System (SLS) rocket, they first had to construct the Vertical Assembly Center (VAC) [00:03:39]. This 170-foot tall tool is used for welding together the domes, rings, and barrel sections of the rocket’s fuel tanks [00:03:47]. The SLS took 11 years of development before one was assembled on the pad [00:04:08].
A traditional rocket engine injector, for example, could consist of over a thousand individual pieces and take nine months to produce [00:08:03]. Similarly, on Space Shuttle main engines, the combustion chamber and nozzle required thousands of very small pipes (1,080 individual pipes) to be formed and then brazed together to create cooling channels [00:08:54]. This was a “ridiculously labor-intensive task” [00:09:06].
Traditional aerospace factories largely build products one at a time by hand, utilizing hundreds of thousands to millions of individual parts [00:13:48]. This paradigm has not significantly changed since the Apollo era [00:13:54]. Automation has not been widely adopted in aerospace due to the low production volume of rockets and the sheer number of parts involved compared to, for example, automobiles [00:15:04].
3D Printed Rocket Manufacturing
Relativity Space’s approach utilizes its large-scale 3D metal printer, named Stargate, to print entire rockets [00:00:00], [00:14:20].
The Printing Process
The 3D printing process for large rocket components, such as fuel tanks, involves:
- Wire-melt technology: An aluminum alloy wire from a spool serves as the raw metal [00:01:38].
- Plasma arc discharge: The wire is fed at about 10 inches per second, and a combination of lasers and plasma arc discharge work simultaneously to melt the metal [00:01:51].
- Precise deposition: The electric waveform is changed every couple of milliseconds to control the deposition of the molten metal [00:01:10]. The temperature is just a few hundred degrees above aluminum’s melting point of 660 degrees Celsius [00:01:22].
- Layer-by-layer construction: The entire body of the rocket is melted together one tiny bit at a time [00:01:30]. Layers are visible on the finished product, but this only adds an extra 5-10% to the mass [00:04:56]. The surface roughness does not cause aerodynamic problems [00:05:19].
- Smaller parts: Smaller, more complex parts like rocket nozzles are typically 3D printed using metal powder and lasers, laying down very fine layers about a 20th the thickness of a human hair [00:09:34].
Advantages of 3D Printing
3D printing offers several significant benefits in aerospace manufacturing:
- Reduced Part Count: One of the major benefits is the reduction in the number of parts [00:08:15].
- An engine injector, which traditionally had over a thousand pieces, can be 3D printed as a single piece [00:08:08].
- Rocket nozzles can have cooling channels for cryogenic propellants printed directly into a single part, eliminating the need for thousands of external pipes [00:09:20].
- A fully 3D printed rocket can have a hundred times fewer parts than a traditionally built one [00:13:37].
- Rapid Iteration: 3D printing allows for rapid iteration [00:10:41]. Parts can be built and tested quickly, then redesigned and reprinted rapidly [00:10:43]. The design can be changed extremely fast because part geometries are controlled via CAD models, with printers printing directly from files [00:11:07]. An entire engine can be built in about a month, allowing for continuous improvement with new versions [00:11:19].
- Optimized Design: 3D printing enables engineers to build parts that would be impractical or impossible with traditional techniques [00:11:54]. This includes smooth, curvy, bio-inspired designs that are just as easy to print as ordinary structures [00:12:00]. The structures can be optimized for stiffness, such as printed stiffeners inside rocket tanks that prevent buckling [00:06:41].
- Material Strength: Counterintuitively, 3D printed materials can be stronger than traditionally built ones [00:10:15]. This is achieved by developing custom alloys in-house and taking advantage of the rapid melting and cooling/solidification process to achieve strong alloys [00:10:21].
- Cost and Time Reduction: 3D printing significantly reduces cost and time. An injector, for example, takes two weeks to print and costs 10 times less than its traditional counterpart [00:08:12]. For a full rocket, this technology aims to lower costs by 5 to 10, or even 100 times, for a fully reusable rocket [00:17:33].
- Automation: 3D printing inherently brings automation to aerospace manufacturing [00:14:41]. Instead of robots assembling millions of individual parts, the assembly is done in the 3D file, and the printer prints them assembled [00:15:50]. Relativity Space’s factory has no fixed tooling, unlike the rest of the aerospace industry [00:13:41].
Challenges and Solutions
Early experiences with 3D printing can be frustrating, resulting in piles of unusable metal [00:02:28]. However, solutions have been developed:
- Warping: Printing a 3D file directly would result in warped and unusable material due to cooling [00:05:30]. Relativity Space invented software that “reverse warps” the part before printing, so the robots print a wobbly shape that becomes perfectly straight (within a human hair’s thickness) as it cools [00:05:40]. This entire process is simulated computationally [00:06:00].
- Material properties: Initial concerns about the strength of 3D printed metals have been addressed by developing custom alloys [00:10:09].
Impact and Future Vision
Relativity Space’s first rocket, Terran One, is designed mostly for low-earth orbit [00:16:01]. Their next rocket, Terran R, is significantly larger (16-foot diameter) [00:12:06] and capable of sending payloads to the Moon and Mars [00:16:05].
The long-term vision of Relativity Space is to shrink their “factory of the future” down to something that can be launched to Mars to build an industrial base there [00:16:19]. This factory is far smaller and lighter than a traditional one [00:16:33].
Even if Relativity’s rockets don’t become the primary launch vehicles, the company is secure because they are now “world experts” on 3D printing rocket hardware, having applied it to areas previously dismissed [00:17:00]. The shift to 3D printing in aerospace is seen as akin to the automotive industry’s shift from internal combustion engines to electric vehicles, where the entire product, factory, and supply chain are transformed [00:12:51].
This technology is poised to lower the cost of space access significantly, potentially making space travel much cheaper [00:17:31]. The ultimate goal is to expand the possibilities of human experience, including the establishment of human civilization on Mars [00:18:05].
Sponsorship This video was sponsored by Omaze, offering a chance to win a trip to space with Virgin Galactic. Part of the contribution from entries supports Space for Humanity, an organization focused on expanding access to space and training global leaders for a sustainable future [00:19:00].