If a rocket wants to overcome the gravity of the earth and accelerate to the first cosmic speed, all and only it relies on the reaction force generated by the engine’s backward injection of working fluid. Therefore, the level of rocket engines directly determines a country’s ability to enter space. Building a stable and reliable high-thrust engine is not only the hardest indicator to measure a country’s aerospace capabilities, but also a comprehensive reflection of a country’s top industrial capabilities, which includes a comprehensive assessment of a country’s materials, technology, control, system engineering and other fields. Because of this, there are only a handful of countries in the world that can independently develop large liquid rocket engines. Looking forward to the future development of the space economy, the development and utilization of space resources, the construction of large-scale space stations, and even the popularization of space tourism all depend on one key factor: how to significantly reduce the cost of entering space, and rocket engines are at the core of it.
From the perspective of rocket engines, they are mainly divided into solid rocket engines and liquid rocket engines. I won’t leave the solid rocket motor aside for now, but I’ll mainly talk about the liquid rocket motor here.
From the perspective of liquid rocket engines, countries initially used room-temperature propellants, including nitro oxidizer/hydrazine, hydrogen peroxide/kerosene, hydrogen peroxide/pentaborate hydrochloric acid, and nitric acid/kerosene. Among them, nitro oxidizer/hydrazine was the most used, followed by hydrogen peroxide/kerosene. Hydrogen peroxide/pentaborate hydrochloric acid, and nitric acid/kerosene were used as propellants. The former Soviet Union made two models, and no one else did. From the perspective of nitro oxidizer/hydrazine, my country has made many models, including YF-2, YF-2A, YF-3, YF-20, YF-20B, YF-20K, YF-20C, YF-2 1. YF-21B, YF-21C, YF-22, YF-22F, YF-22B, YF-22C, YF-22K, YF-22E, YF-23, YF-23F, Y F-23H, YF-23B, YF-23C, YF-24, YF-24B, YF-24C, YF-24F, YF-24K, YF-24E, YF-25, YF- 25K, YF-36, YF-40, YF-40B, YF-40C, YF-40D, YF-50D, YF-50E, RD-01, RD-01MV, TH-31. Technically, our country chose to start with dinitrogen tetroxide/uniform dimethylhydrazine, not because it is good, but because it is “sufficient” and “available”. It is liquid at room temperature and can be poured into missiles and rocket tanks for a long time to meet the military needs of combat readiness and rapid response. This was the choice made in the early days of the founding of the country when my country urgently needed “two bombs and one satellite” to defend national security and establish its status as a great power. Compared with low-temperature propellants, its materials, processes, and ground support systems pose fewer challenges, allowing us to solve the “whether or not” problem first despite a weak industrial base. It is precisely with this “poisonous hair” system that we have successfully developed gold-medal rockets such as the “Long March 2” series, launched returnable satellites, and achieved manned spaceflight, laying the foundation for my country’s aerospace power. The same is true for the United States. Its early rocket and missile industries also started with storable room-temperature propellants, which was an inevitable choice under the technical conditions and military needs of the time. The core propellant combination chosen by the Americans is dimethylhydrazine/mixed hydrazine and dinitrogen tetroxide. This is a “self-igniting” combination that ignites on contact and is highly reliable. It can be stored in launch silos or submarines for a long time. The “toxic hair” technology in the United States is very mature, and the main models include LR-81-BA-9, LR-87-AJ-9, LR-87-AJ-11, LR-91-AJ-11, TR-201, R-4D, and AJ-10-138. The Soviet rocket engine technology started from the legacy of the German V-2. The V-2 used liquid oxygen/alcohol. Therefore, the R-1 and R-2 obtained by the Soviet Union through imitation and improvement of the V-2 in the early stage also used liquid oxygen/alcohol. Then the Soviet Union found a very unique technical path: nitric acid/kerosene. Although the performance of nitric acid is not top-notch, it is liquid at room temperature, can be stored, and is easier to handle than liquid oxygen. Kerosene is cheap and easy to obtain.
As aerospace shifts from military orientation to civilian exploration, environmental protection and economic needs have become more prominent, and the research and development of liquid oxygen kerosene technology has accelerated. However, as of today, there are still only a handful of countries in the world that can produce liquid oxygen kerosene engines, including China, the United States, Russia, South Korea, Ukraine, Europe, India, and Germany. Among these countries and regions, Europe, India, and Germany all have only one model, while Ukraine mainly inherited products from the former Soviet Union. Although South Korea has three models: KRE-075, KRE-075V, and KRE-007, the KRE-075 engine was developed based on the 15-ton liquid oxygen kerosene engine drawings provided by the Southern Design Bureau of Ukraine. KRE-075 V is based on the improvement of KRE-075 for high-altitude environments. Although KRE-007 is the first practical upper-stage liquid engine in Korean aerospace history, its specific impulse is not as good as RD-0210, RD-0211, and RD-0212. Therefore, the only real players are China, the United States and Russia. Our country’s liquid oxygen kerosene engines are being produced by both the national team and private enterprises. The main models of the Sixth Academy of Aerospace Science and Technology include YF-100, YF-100K, YF-100M, YF-100N, YF-115, YF-130, YF-135, YF-102, YF-102V, and YF-102R. In addition to the Sixth Academy of Aerospace Science and Technology, there are also some private companies that are also doing this, such as: Tianbing Technology (Tianhuo-11, Tianhuo-12, Tianhuo-12V), Galaxy Power (Cangqiong-50, Cangqiong-90), Deep Blue Aerospace (Thunder-R1, Thunder-R1, etc.) Ting-RS), Oriental Space (Force-85, Force-110), Aerospace Engine (Yanyu-1A, Yanyu-11), Tianhui Aerospace (Xiaolong-1, Honglong-1, Qiaolong-1), China Aerospace (Liqing-1, Liqing-2), etc. The main companies in the United States that can produce liquid oxygen and kerosene engines include Rocketdyne (S-3D, MA-5, MB-3, RS-27, F-1, H-1), SpaceX (Merlin 1C, Merlin 1D), Rocket Lab (Rutherford), Firefly Aerospace (Beetle-1, Lightning-1, Miranda), and Launcher (E2). Russia’s liquid oxygen kerosene rocket engine technology is very mature and enjoys a global reputation for its powerful thrust, extremely high combustion efficiency and unparalleled reliability. The main models include NK-9, NK-15, NK-15V, NK-33, KS-50, RD-58, RD-105, RD-107, RD-108, RD-110, RD-111, RD-448, RD-461, RD-010 5. RD-0109, RD-120, RD-170, RD-172, RD-180, RD-151, RD-191, RD-191M, RD-191MR, RD-1 71M, RD-171MV, RD-0110, RD-0110R, RD-0124, RD-0124MS, although some models have been retired, their overall strength cannot be underestimated. Russia once established a technological lead in the field of liquid oxygen kerosene engines by virtue of its oxygen-rich prechamber staged combustion cycle technology and multi-combustion chamber design. The RD-180 engine (a dual-combustion chamber version of the RD-170) was exported to the United States for use in the Atlas V launch vehicle. Although the United States later decided to terminate the purchase due to political reasons, the outstanding performance of the RD-180 is obvious to all.
As mankind continues to move further into the “starry sea”, the development of liquid hydrogen and liquid oxygen engines is no longer an “optional”, but has become a “must have option” for a space power to move into deep space. If you want to send probes to the moon, Mars and even further planets, you will need a huge increase in speed. The core of these tasks is the efficiency of the upper stage engine, and the unparalleled specific impulse is the core and most irreplaceable advantage of the liquid hydrogen and liquid oxygen engine. When performing the same deep space exploration mission, using liquid hydrogen and liquid oxygen upper stages can significantly reduce the amount of propellant carried, thus significantly increasing the payload. Currently, the only countries in the world that can produce liquid hydrogen and liquid oxygen engines are China, the United States, Russia, Europe, Japan, and India. India has two liquid hydrogen and liquid oxygen engines: CE-7.5 and CE-20. CE-7.5 is a hydrogen-oxygen engine developed by India based on the technical characteristics of KVD-1. However, due to India’s relatively backward manufacturing level, the CE-7.5 not only has a slightly lower specific impulse, but also doubles its weight. KVD-1 is an upper-stage engine developed by Russia for India’s GSLV Mk1. It is based on the Soviet Union’s first hydrogen-oxygen engine RD-56. CE-20 is a hydrogen-oxygen engine developed by the Indian Space Research Organization and installed on the GSLV Mark III. The development of Japan’s liquid hydrogen and liquid oxygen engines was first through the introduction of technology. Delta rocket technology was introduced from the United States. After digesting and absorbing related technologies, it successfully developed the LE-5 engine from the late 1970s to the early 1980s. During the development process of LE-5, Japan gradually mastered the core technology of liquid hydrogen and liquid oxygen engines, especially the low-temperature turbine. After the design, manufacturing and testing of the pump, Japan subsequently launched the development of the LE-7 engine. Currently, the main models of Japan’s liquid hydrogen and liquid oxygen engines include LE-5, LE-5A, LE-5B, LE-7, LE-7A, and LE-9. Some of them have been retired, mainly by the Space Development Agency and Mitsubishi Heavy Industries (LE-9). European liquid hydrogen and liquid oxygen rocket engines mainly include Vulcan, Vulcan 2.1, HM-7, HM-7B, and Finch engines. The Vulcan engine was developed by France’s European Power Plant (SEP) from 1984 to 1996 and has now been retired. Vulcan 2.1 is an engine developed by Arianespace on the basis of the original Vulcan engine, and is installed in the core stage of Ariane 6. Relatively speaking, the three countries with the strongest technical strength are China, the United States and Russia. Our country’s liquid hydrogen and liquid oxygen engines mainly include YF-73, YF-75, YF-75D, YF-75H, YF-75E, YF-77, YF-79, and YF-90. The main liquid hydrogen and liquid oxygen engines in the United States include J-2, RS-68, RS-25, RL10, RL10A, RL10B, RL10C, BE-3, BE-3U, and BE-7. Russia’s liquid hydrogen and liquid oxygen engines mainly include RD-0120, RD-0146, RD-54, RD-56, RD-56M, RD-57, RD-57M, KVD-1, and D-57. I won’t go into detail about the liquid hydrogen and liquid oxygen engines of China, the United States and Russia. Our country has written a special article before. If you want to know more about it, you can read that article. The United States and Russia will write separate articles later. It is too much to write here.
With the development of rocket reusability technology, the development of liquid oxygen methane rocket engine technology has become urgent. At this point, there are even fewer players participating. Only China, the United States, Russia and Europe are left. Russia is no longer a core player. There is only the RD-0162 engine, which is still under development. Let’s see if it can be released before 2030. There are two types in Europe: Prometheus (Ariane Space) and MR-10 (led by Italy’s Avio and jointly developed with companies from Belgium, the Czech Republic, Switzerland, France, Austria and Romania). The remaining two countries are China and the United States. The main ones in our country that are producing liquid oxygen methane engines are the Sixth Academy of Aerospace Science and Technology (YF-209, YF-215), the Aerospace Science and Industry (Mingfeng 1, Mingfeng 2), Blue Arrow Aerospace (Tianque-11, Tianque-12, Tianque-12A, Tianque-15A, Tianque-12B, Tianque Que-15B, Lanyan), Interstellar Glory (Focus 1, Focus 2), Kyushu Cloud Arrow (Longyun, Lingyun, Fengyun-100, Fengyun-200), Aerospace Propulsion (Casalong 1, Canglong 2), Lingke Aerospace (Storm-1, Storm-5A), Rocket School (Shannon), Tianhui Aerospace (Red Dragon 2). The main manufacturers of liquid oxygen methane engines in the United States include Blue Origin (BE-4), SpaceX (Raptor 1, Raptor 2, Raptor 3), Rocket Lab (Archimedes Engine), and Relativity Space (Eternal-R).
With the rise of commercial aerospace, rocket engines have become the key to promoting the development of the space economy. Without rocket engines, it would be impossible for humans to enter space. Currently, we are standing on the eve of the outbreak of the “space economy”, and low-cost and reliable launch capabilities are the basis for opening the door to the “space economy”. From a broader perspective, the development of powerful rocket engine technology is the technical prerequisite for human beings to eventually leave the earth, become a multi-planetary species, and realize the long-term continuation of civilization. It carries the eternal dream of human beings to explore the unknown and move towards the sea of stars.
