LandSpace launched its methane-based ZhuQue-2 rocket on Wednesday. This was the rocket’s second launch after its failed maiden flight in December 2022. Initial claims from the company noted a mission success, marking the first methalox rocket to reach orbit.
The ZhuQue-2 rocket
ZhuQue-2 (Redbird 2 in English) is a rocket designed by the Chinese private company LandSpace. It stands 49.5 meters tall with a rocket body diameter of 3.35 meters. The medium-sized launch vehicle has a carrying capacity of up to six tons into a 200-kilometer low-Earth orbit and up to four tons into a 500-kilometer Sun-synchronous orbit (SSO).
One focus of the development of ZhuQue-2 was green and economically viable methane. According to the LandSpace website, the price of propellant was reduced by 50-90%, comparable to similar Chinese launchers. Furthermore, methane allows for a non-toxic, less-polluting, and more modern approach to fuel the rocket, compared to the hypergolics of the early Chang Zheng family.
Also, ZhuQue-2 utilizes standardization and generalization across the whole rocket. The rocket is made out of off-the-shelf parts when possible, and with that, LandSpace could reduce the cost of the whole stack even further.
The first stage, which features the rocket’s characteristic red bird, is powered by four TQ-12 liquid methane-liquid oxygen (methalox) engines. These are China’s first methane engines used on a launch vehicle. They are gas generator open-cycle engines, which are simpler than other new methalox engines, such as SpaceX’s Raptor or Blue Origin’s BE-4. When combined, four TQ-12 engines are referred to as a TQ-13 engine pack.
At liftoff, these engines produce a thrust of 268 tons. The whole stack has a mass of 219 tons, which brings the overall thrust-to-weight ratio to 1.22. The engines have a nozzle diameter of 1.5 meters and operate on a mixture ratio of 3.5 parts oxygen to methane by mass. The specific impulse at sea level is 284.5 seconds.
The engines were initially fired in May 2019 in preparation to certify them for the maiden flight. Down the line, LandSpace plans to develop this engine into the TQ-12A, providing improved thrust, specific impulse, and mass efficiency.
In the second stage, the rocket still features a TQ-12 engine, assisted by four TQ-11 vernier engines. This will change in one of the upcoming flights with the upgrade to the TQ-15A engine, providing gimbal capabilities and deleting the vernier engines.
After the second stage burn is done, the final insertion burn will only be done by the TQ-11 vernier engines. While the main chamber shuts down, the four verniers will bring the rocket into the final orbit using a more precise thrust.
The first stage of the rocket will also feature reusability in the future. While this is not a topic that LandSpace has detailed so far, it was confirmed that the first stage TQ-12A engine will be built with multiple relights in mind, which is required for a reusable first stage if the company desires to land it propulsively.
Leading up to launch
The first signs of an imminent launch campaign were sightings by Harry Stranger, who used satellite imagery to see that the pathfinder rocket was back on LandSpace’s Launch Site 96. This ZhuQue-2 pathfinder was used in the past for fit checks of the transporter and pad and hinted at a return of the rocket shortly.
In mid-May, LandSpace showed pictures of the rocket’s 3,700-kilometer journey through China to the pad. This transport is also why the common diameter of Chinese rockets, including ZhuQue-2, is about 3.5 meters. Anything bigger than that would limit the rocket’s ability to be transported on roads and trains.
After an initial rollout was spotted in early June, the rocket was soon rolled back to the hangar, presumably because of a second stage release pin malfunction during the third full pre-launch test.
High resolution satellite imagery taken on 2023-07-09 at 00:36:51 UTC shows Landspace's Zhuque-2 flight 2 rocket standing vertical on its launch pad at Jiuquan SLC.
— Harry Stranger (@Harry__Stranger) July 9, 2023
LandSpace then confirmed the rollout and raising of the rocket in a video posted on Chinese social media at the beginning of July. Since then, the vehicle has been sitting vertically on Launch Site 96 at the Jiuquan Satellite Launch Center in China.
ZhuQue-2’s second flight payloads
So far, the payload for this launch remains unknown. It is unclear if LandSpace got another payload on this rocket after the initial maiden flight or if they are flying a dummy payload for this mission. Regardless, the payload fairing is on top of the rocket so that the rocket flew in a comparable configuration to a normal operational flight.
This mission’s mission patch also focuses on the rocket and gives no clues about a potential payload. On the rocket’s site, the flight’s motto “bringing green energy to life” has been released.
ZQ-2’s maiden flight failure
In an investigation report months ago, LandSpace detailed the problems of the first flight. A liquid oxygen (LOX) pump low-pressure outer casting for the second stage vernier engine broke under impact force from the second stage main engine shutdown.
During that moment, the rocket was already traveling at five kilometers per second according to telemetry shown on Chinese social media. With that, it lacked about two kilometers per second to reach orbit successfully.
This was during the event in which the second stage would shut down and let the four verniers take the rest of the flight. During this time, a connection at the LOX inlet pipe broke, which was not properly designed for the shutdown. LandSpace conducted a series of ground tests, reinforcing the failure’s culprit.
This will be the last flight of the TQ-12 upper-stage combination. After flight two, the enhanced TQ-15A will take over, eliminating the problem. The first stage on the maiden flight, including the four TQ-12 engines, performed flawlessly.
The methane race to orbit
After ZhuQue-2 failed the first attempt in late 2022, both Starship and Relativity Space’s Terran-1 did not complete their mission profiles for their maiden launch, and the race remained open.
Starship, ULA’s Vulcan, and ZQ-2 by LandSpace remained in the race, with Relativity Space no longer pursuing Terran-1 operations. Other methane rockets, such as Blue Origin’s New Glenn and Terran-R by Relativity Space, are not expected to fly anytime soon.
Due to chemistry and engineering challenges, methane rockets have not been strongly considered throughout spaceflight history. But with green propellants and reusability being more in focus, methane suddenly shows advantages over traditional fuels.
One of the main challenges of methane is combustion stability, as the boiling point of methane is very close to that of its oxidizer. Hence, the state of matter that both the oxygen and methane molecules are in during the combustion is less evident than it is with hydrogen or rocket propellant 1 (RP-1). This can lead to instability in the pre-burners and main chambers.
Another important factor is the increasingly economical race to build cheaper rockets. Methane is the cheapest of the three more “traditional” fuels, beating RP-1 and hydrogen. Especially with reusable rockets, fuel cost is a much more important factor in the overall economy. Reducing fuel prices can bring huge advantages.
One final advantage of methane over RP-1 is that it lacks the problem of coking. Since RP-1 does not burn clean, it leaves other substances behind that get stuck on the nozzle and can clog the engine plumbing over time. While this has not been a problem with only once-used rockets, it can be a challenge for reusable rockets of the future.
The company LandSpace
LandSpace was founded in June 2015, and its first developed rocket was the ZhuQue-1. The rocket was planned to be a three-stage solid-propellant rocket and performed its maiden flight in October 2018. After this flight, the company entirely moved to develop ZhuQue-2, their medium-lift carrier rocket.
Rumors about LandSpace’s difficult financial situation have appeared in the last few weeks. Hence, the flight of ZhuQue-2 could become an important milestone in the company’s future, as they could aspire to absorb the market of medium-sized SSO payloads currently covered by early-generation Chang Zheng rockets.
(Lead image: ZQ-2 flight 2 launch. Credit: LandSpace)