Successful ZhuQue 2 ushers in the era of methalox orbital rockets
The first rocket to put a payload into orbit using methalox propellants – liquid methane and oxygen – is Chinese. The second flight of the ZhuQue 2 (ZQ-2, also called Suzaku-2) made a successful flight today, July 12, 2023, making the Chinese pioneers in the practice of placing into orbit using methane engines. The launch took place at 09:00 Beijing time (01:00 UTC) from Jiuquan Spaceport. Several Western companies invest in methalox propellants, but none had succeeded in launching a spacecraft into space using this type of propulsion. ZQ-2 Y2 launched its second stage into orbit, supposedly with a fixed test payload, with orbital parameters of 431 km by 461 km, inclined at 97.3 degrees to the equator.
The ZhuQue 2 is a private rocket similar to the CZ-2C and CZ-2D built by Chinese state academies, with the difference that it uses liquid oxygen and methane instead of hydrazine and nitrogen tetraoxide. This rocket is capable of launching up to four tons of payload into a sun-synchronous orbit. In March of this year, LandSpace had already confirmed that the second Zhuque-2 had completed assembly and was being prepared for a launch attempt “in the coming months”. The Zhuque-2 is capable of carrying 6,000 kg of payload in a low orbit of 200 km or 4,000 kg in a 500 km Sun-synchronous orbit. The rocket was initially planned to launch in 2020, however in 2019 it was pushed back to 2021, and later to December 2022. It has a takeoff weight of 216 tons and uses four TQ-12 engines in the first stage, each with a thrust of 67 tons. The second stage uses a vacuum-optimized TQ-12 with an 80-tonne thrust in combination with an 8-tonne thrust TQ-11 engine that acts as a 'vernier' thruster.
A private company using proven state-owned technology
Beijing Lanjian Space Science and Technology Company, or “Blue Lightning” (Chinese 北京蓝箭空间箭空间科技有限公司, or Beijing Lanjian Kongjian Keji Yuxian Gunsi, Beijing Blue Arrow Space Technology Co. Ltd., registered trademark of Landspace – officially a private company) was founded in June 2015, with the solid-fuel rocket Zhuque-1 (朱雀一号, Zhuque-1, ZQ-1). This rocket suffers a breakdown during its first launch on October 27, 2018, after which the developers changed its design to use methalox.
On 14 December 2022, a previous launch of a ZQ-2 failed, when the first stage worked normally, but the second stage malfunctioned due to an early shutdown of the vernier engines after the main engines had apparently completed a good burn. It was the world's first orbital launch attempt by a methane-powered launch vehicle, and it was the first methane launch vehicle to reach space – but without entering orbit.
The ZQ-2 project started in September 2017, and development was announced in April 2018. The general scheme was copied from existing Chinese products – the Long March 2C and 2D, with two stages – the first with four engines of the 70-ton class, controlled tipping; the second has a similar main engine and a four-chamber steering engine, which also performs the function of additional propulsion. The standard diameter is 3.35 meters, the total length is 49.5 meters, and the launch weight is 219 tons with a launch thrust of 268 tf. The cargo is housed in the fairing, which has a diameter of 3.35 m and a length of 8.24 m.
In May 2019, LandSpace conducted test firings of its TQ-12 engine at its test facility in Huzhou, Zhejiang Province. Research and development chief Ge Minghe said the engine had a thrust of 80 tonnes. The Huzhou facility would be capable of producing around fifteen ZQ-2 rockets and 200 TQ-12 engines as of 2022, according to CEO Zhang Changwu.
Methane as a rocket fuel has several advantages, despite the early research efforts of various space agencies on methane-powered rocket fuels, it remained in the stage of technical verification and exploration throughout the 20th century. It wasn't until the 2020s, after more than half a century of technological development, that methane-fueled engines finally reached the threshold of practical application. Almost simultaneously, the technology of reusable rockets matured, which propelled the use of methane as a propellant and made it a promising "favorite" for future rocket propulsion.
The history of liquid oxygen methane rocket engines dates back to the early 1930s. The launch of the Hocker-Winkler rocket in March 1931, as you mentioned, marked an early attempt at utilizing liquid oxygen methane as a propellant.
The Hocker-Winkler rocket, pioneered by Johannes Winkler, had a distinct design from contemporary rockets. The fuel was stored in a pipe, and the single-engine was located at the center of the rocket. However, the rocket's flight was limited, reaching a height of only about 60 meters. Due to its lack of practical value during that era, the Hocker-Winkler rocket did not gain significant recognition or make significant advancements.
Since then, the radicalization and development of liquid oxygen methane rocket engines have seen gradual progress and increasing attention in recent years. Technological advancements, research, and the need for more efficient and environmentally friendly propulsion systems have contributed to the renewed interest in liquid oxygen methane rockets. These advancements have paved the way for the exploration of methane as a propellant in modern rockets and its potential as a viable option for future space missions.
In the 1960s, U.S. aerospace companies initiated early explorations into the practical application of methane-containing rocket fuel. They accumulated extensive experience in the preparation and use of liquid oxygen methane propellant. In the 1980s, China also conducted preliminary studies on methane-containing rocket fuel engines. They conducted tests on methane and propane electric heat transfer and thrust chamber ignition, achieving initial results. Several aerospace research units worldwide have amassed a wealth of research findings and experience, providing a solid foundation for the development of liquid oxygen methane engines.
Other countries such as the European Space Agency (ESA), Russia, and India are also conducting research on liquid oxygen methane engines. However, practical engine models have not yet been produced, and the research is still in the early stages.
The advantages of methane as a rocket fuel have contributed to its increasing popularity as a "new favorite" in rocket propulsion. Despite earlier research efforts, various limitations and considerations hindered the practical application of liquid oxygen methane engines throughout the 20th century. They remained in the stage of technological verification and exploration without achieving significant recognition.
However, in the 2020s, after over half a century of technological development, liquid oxygen methane engines have finally reached the practical stage. This coincided with the maturation of recoverable reusable rocket technology, which prompted the utilization of liquid oxygen methane propellant to leverage its strengths and overcome its weaknesses. As a result, methane has emerged as a promising choice for future rocket propulsion.
Advantages of methane as a rocket fuel:
1. High efficiency: The mixture ratio and combustion temperature of methane and liquid oxygen result in a high specific impulse, meaning it generates a higher exhaust velocity for a given thrust. This allows rockets to achieve higher speeds and more efficient fuel utilization.
2. Environmentally friendly and low carbon: Compared to traditional rocket fuels like solid propellants and toxic liquid fuels, methane combustion produces lower levels of carbon dioxide emissions. It is considered a more environmentally friendly fuel choice, helping to reduce adverse impacts on Earth's climate.
3. Renewable energy source: Methane can be produced through various methods, including natural gas cracking and renewable sources such as biomass and synthetic gas. This makes methane a part of sustainable development and energy diversification.
4. Reusability: Combining methane fuel with reusable rocket technology can significantly reduce the cost of space launches. Methane fuel causes less wear and tear on the engines and propulsion systems, extending their lifespan and making rockets more cost-effective.
With ongoing technological advancements and increasing demand for sustainable energy, methane as a rocket fuel is gaining more attention. It is considered a promising choice for future rocket propulsion, expected to drive space technology to higher levels.