On May 26, 2020, the European Space Agency (ESA) conducted a hot test run of a fully additively manufactured rocket thrust chamber at the German Aerospace Center (DLR). The first test lasted 30 seconds, and other tests are expected within this week. ESA will collect and analyze the test data.
Integrated cooling runner
According to ESA, the 3D printed thrust chamber under test has only three parts that can power the upper layers of future rockets. The number of parts in the thrust room of additive manufacturing is reduced from hundreds to three, which shortens the production time and reduces the cost, and significantly improves the competitiveness of the liquid propulsion engine in the European launch vehicle.
The full-size thrust chamber under test has a 3D printed copper alloy lining with integrated cooling channels, and the outer layer is a high-strength jacket built by cold air spraying. 3D printed thrust chamber manifolds and integral fuel injection are also additively manufactured.
The production and testing of these 3D printed parts have been carried out in ESA's "Future Launcher" preparation plan.
ESA stated that the full-scale 3D printing thrust chamber tested this time is based on the technology and method verified in 2019 by ETID (Expander-cycle Technology Integrated Demonstrator-ETID).
ESA has tested four configurations of ETID in total. ETID has three new combustion chamber geometries and designs. Two different injector heads were also tested, including full 3D printed nozzles, and a regenerative nozzle that optimizes the engine cycle by maximizing heat absorption. Both the combustion chamber and the nozzles use the heat of combustion to preheat, and therefore "expand" the hydrogen propellant before combustion. The flow of cold hydrogen also has the effect of cooling the hardware, keeping the temperature within a reasonable range during operation.
ESA conducted a total of 23 tests on ETID, with a total running time of 2707s. During the test, 49 different operating points were reached, including testing the behavior in the "extreme" state, such as increasing the flow of cold hydrogen in the system, and therefore "supercooling" the hardware during operation. The tests show the versatility of the ETID design and can operate over a wide mixing ratio and chamber pressure range. Multiple operating points will also facilitate calibration, which is used to design a subsequent engine and predict the numerical model of its performance.
Since May of this year, we have successively witnessed the remarkable results achieved by the aerospace 3D printing application.
At 18:00 on May 5, the new member of China's "Fat Five" family, the Long March 5B rocket, carried a new-generation manned spacecraft test ship and a flexible inflatable cargo return cabin test cabin, and ignited from the Hainan Wenchang space launch site. The prelude to the "third step" mission of China's manned spaceflight project. The new generation of manned spaceship test ship not only completed the first 3D printing space experiment, but also carried the world’s first cubic star deployer based on metal 3D printing technology. In the same period, the fully 3D printed core-level binding support developed by the 211 Factory of the First Academy of China Aerospace Science and Technology Group Co., Ltd. successfully passed the flight assessment verification.
On May 31st, SpaceX's latest manned dragon spacecraft was successfully launched at the 39A launch pad of the Kennedy Space Center in the United States. 3D printing has played an important role in the manufacture of the launch vehicle Falcon 9 and the manned dragon spacecraft and the helmets of two astronauts.
3D printing has become a core technology in the field of aerospace manufacturing. Especially in the field of rocket engine manufacturing, 3D printing has become an important "bargaining chip" for aerospace manufacturing organizations to capture the next generation of economical and reusable rocket engines. The 3D printed thrust chamber involved in ESA's recent test drive is a key competitive track for additive manufacturing of rocket engines.
The trend of "a hundred schools of contention"
Copper alloy thrust chamber components
Aerojet Rocketdyne used powder bed selection laser melting 3D printing technology to manufacture copper alloy thrust chamber components. In 2017, it passed the ignition test conducted by the US Defense Production Act Title III project management office. The tested 3D printed copper alloy thrust chamber components are full-size. This thrust chamber will replace the thrust chamber components of the current RL10C-1 engine. The 3D printed copper alloy thrust chamber components consist of two copper alloy parts. Compared with the traditional manufacturing process, the selective laser melting 3D printing technology brings a higher degree of freedom to the design of the thrust chamber, allowing designers to try advanced structures with higher thermal conductivity, such as integrated internal cold aisles. The enhanced thermal conductivity makes the design of the rocket engine more compact and lightweight, which is exactly what the rocket launch technology needs.
NASA made progress in 3D printing of copper alloy parts in 2015. The manufacturing technology is also laser melting 3D printing in selected areas. The printing material is GRCo-84 copper alloy. The 3D printed parts manufactured by NASA using this technology are the rocket combustion chamber lining. The part is divided into 8,255 layers and printed layer by layer. The printing time is 10 days and 18 hours. In 2019, NASA announced a new copper alloy 3D printing material GRCop-42, which is a high-strength, high-conductivity copper-based alloy material that can be used to produce near-completely dense 3D printed parts, such as rocket combustion chambers Liner and fuel injector panel.
Nickel-based superalloy integrated thrust chamber
Material: IN718 nickel-chromium alloy; equipment: SLM280
CellCore worked closely with SLM Solutions, using nickel-based superalloys and selective laser melting technology, to successfully achieve the integrated molding of a multi-function thrust chamber. In the 3D printed thrust chamber, the cooling duct is part of the design and is formed with the entire cavity in the same production process. The integrated rocket engine, combined with the injector and thrust chamber, simplifies many individual components into one, and only through the laser selective melting process can a multi-functional integrated lightweight structure be realized. The internal structure developed by CellCore is distributed throughout the rocket engine, which is not only suitable for heat transfer, but also improves the structural stability of the components.
Integrated more than 100 cooling channels
In 2019, China's dark blue aerospace liquid oxygen kerosene engine once again conducted a long-range test drive in the thrust room, with great success. In terms of thrust performance, Deep Blue Aerospace has optimized the design of the main functional components and used a large number of 3D printing processes to achieve a technical leap from 95% to 99% of the efficiency of the domestic liquid oxygen kerosene rocket engine thrust chamber, reaching the international advanced level.