The test of the Zhuque-3 test rocket was successful. What is the level of my country's reusable rockets?

Produced by: Science Popularization China

Produced by: Trantor Space (popular science creator)

Producer: China Science Expo

Recently, my country's independently developed Zhuque-3 reusable vertical recovery test rocket completed a 10-kilometer-level vertical take-off and landing return flight test at the Jiuquan Satellite Launch Center. This is another milestone since the Zhuque-3 VTVL-1 verification rocket successfully completed the test in January 2024.

The Suzaku-3 is a product of Landspace, a privately-owned carrier rocket company in my country, and is the latest model in the Suzaku series of rockets. Landspace began testing the Suzaku-1 in 2018, and has developed it to the current Suzaku-3 VTVL-1 verification rocket, which marks a major breakthrough in my country's commercial aerospace industry in reusable carrier rocket technology. The future development direction is to develop reusable, high-capacity, low-cost carrier rockets.

Live images of the Blue Arrow VTVL-1 rocket conducting a 10-kilometer altitude recovery test

(Photo source: Landspace)

Blue Arrow Aerospace Suzaku-3 large reusable rocket vertical return technology VTVL-1 test rocket

(Photo source: Landspace)

Why develop reusable rockets?

A reusable rocket is a launch system that can partially or completely recover rocket components and reuse them. The space shuttle is actually a reusable launch system, but its problem is that it cannot be used at a low cost.

According to data from a 2018 meeting of NASA's Ames Research Center, the space shuttle sent a 27.5-ton payload into low-Earth orbit at a cost of about $1.5 billion, or about $54,500 per kilogram, while the Falcon 9 launch vehicle used for commercial launches sent a 22.8-ton payload into low-Earth orbit at a cost of $62 million, or about $2,720 per kilogram. Obviously, although the space shuttle is also a reusable launch system, its launch cost is too high and it will eventually be eliminated.

The space shuttle program also involved issues with the safety of thermal insulation devices, which forced NASA to have another space shuttle ready at another launch site when launching one, ready for rescue at any time, further increasing launch costs.

Two space shuttles were standing at the launch station at the same time, and one was on standby for rescue. As a result, although the space shuttle is a reusable launch system, the launch cost is extremely high.

(Image credit: NASA)

The current definition of reusable rockets focuses more on their low cost. In other words, if low-cost operation cannot be achieved, then the meaning of reusability will be lost. From the perspective of launch vehicles, the bottleneck that currently hinders the large-scale development of low-Earth orbit is the cost issue. The cost here is not the total cost of rocket launch, but the cost per kilogram of payload entering orbit calculated based on the launch quotation and payload mass.

Data from the Center for Strategic and International Studies (CSIS) show that the current cost per kilogram of payload for the Falcon Heavy rocket to enter low-Earth orbit is $1,500, lower than the $9,167 per kilogram of payload for Europe's Ariane 5G launch vehicle and the $4,320 per kilogram of payload for the Proton rocket.

If the cost of sending satellites into orbit is reduced, large-scale development of low-Earth orbit or commercialization of low-Earth orbit will become possible. This is the goal of developing reusable rockets as a space power. For example, the Qianfan Constellation Project, the Honghu Constellation Project, and the GW Constellation Project of China Star Network currently require tens of thousands of satellites to be sent into low-Earth orbit. In April 2020, my country included satellite Internet in the scope of new infrastructure for the first time.

The reduction in launch costs also means that we can send more satellites into orbit. If we use a large-thrust reusable launch vehicle, the cost of building a space station will be lower, the size of the space station will naturally increase, and its functions will be further extended.

The construction of Qianfan satellite constellation has begun

(Photo source: CCTV)

What is the principle of reusable rockets?

At present, the reusable rockets developed by my country focus on the recovery of the first-stage booster, so as to achieve reusability. The recovery method is to let the booster land vertically after completing its mission. To make the first stage of the rocket land vertically, it is necessary to control the direction of the engine spray and the attitude of the rocket. During the landing process, the engine generates an upward reaction force by spraying air downward, gradually controlling the falling speed of the first stage, and at a certain height from the ground, the landing legs are deployed, and finally a fixed-point vertical soft landing is achieved.

The technical aspects involve engine thrust adjustment, attitude control technology during the first stage return, etc., and it is also necessary to develop reusable rocket engines. At present, the ideal power for reusable engines is liquid oxygen-methane engines. The Tianque series used by my country's Suzaku-2 is the world's first liquid oxygen-methane engine that has successfully entered orbit. The 200-ton YF215 liquid oxygen-methane engine is also under development. This is my country's first rocket engine that uses full-flow staged combustion cycle technology, which is conducive to my country's expansion of space exploration.

The Suzaku-2 Yao-2 carrier rocket was launched from the Jiuquan Satellite Launch Center in my country

(Photo source: Xinhua News Agency)

Recycling the first-stage booster is of great significance to the reusability of rockets. The cost of reusable engines is relatively high, accounting for about 60% to 70% of the total rocket launch cost, mainly because the engines are relatively expensive. The Falcon 9 uses 9 engines, each of which costs about 2 million US dollars. The cost of the first-stage booster alone costs about 18 million US dollars, which accounts for a large proportion of the 62 million US dollars quoted for a launch.

If there are more boosters, such as three, then the impact of these boosters on the launch cost will be greater. At the same time, the separation altitude of the first-stage booster has not yet left the atmosphere, which is also suitable for recovery, and the technical difficulty involved is much lower than the recovery of the second-stage engine.

The test flight of the Suzaku-3 VTVL-1 verification rocket this time verified the vertical return technology. After the first stage ignited and took off, it reached an altitude of 10 kilometers. This altitude was chosen because 10 kilometers is high enough to verify various disturbances. During the descent, the first stage can use grid rudders, vertical reverse thrust and restart of the rocket engine to jointly control its attitude. These are all what the Suzaku-3 VTVL-1 verification rocket will test.

As the mass of the rocket increases, the landing cushion system is the key to the rocket's soft landing. The cushion device will absorb the kinetic energy and potential energy of the rocket body to ensure the rocket's safe landing under complex conditions.

What are the characteristics of the Suzaku-3 VTVL-1 rocket?

The Suzaku-3 VTVL-1 is positioned as a verification rocket and is an engineering prototype built with a full-size engine. Blue Arrow Aerospace plans to verify a number of key technologies for reusable rockets through vertical take-off and landing recovery tests.

The test rocket is a single-stage liquid oxygen-methane rocket with a body diameter of 3.35 meters, a length of 18.3 meters, a takeoff mass of about 68 tons, and an 80-ton Tianque-12 improved liquid oxygen-methane engine with variable thrust adjustment and multiple ignition capabilities. The body of the rocket uses a high-strength stainless steel body structure, with a 4-piece grid rudder system, and 3 sets of landing buffer mechanisms for soft landing. From the appearance, it can be determined that the Suzaku-3 VTVL-1 is not the finalized model, and is still mainly used for testing. The full-state Suzaku-3 will make its first flight in 2025.

my country's vertical landing technology demonstration

(Photo source: Xinhuanet)

Suzaku-3 full status image

(Photo source: Landspace)

The verification rocket can be distinguished from the rocket that can perform launch missions by its appearance. The verification rocket does not have a fairing and has a simple structure, which only needs to meet the hardware conditions required for testing.

The full-state Zhuque-3 will be equipped with nine improved Tianque-12 engines, which can send a payload of 12 to 21 tons into low-Earth orbit, making it a leading country internationally. After all, China and the United States are the only countries that can currently develop reusable rockets. However, our private aerospace companies are developing many types of reusable rockets. In addition to the Zhuque-3, there are also the Hyperbola-3 launch vehicle, the Tianlong-3 launch vehicle, and so on, forming a competitive situation where a hundred flowers bloom, laying a solid foundation for my country's large-scale development of low-Earth orbit space.

Since reusable rockets are not compared in terms of carrying capacity, the ability of a reusable rocket is not evaluated by the larger the carrying capacity, the better. Instead, it is the cost per kilogram of payload to enter orbit under certain conditions. Obviously, the lower this cost is without affecting the carrying capacity, the better the rocket is. From this perspective, both Suzaku-3 and Tianlong-3 have strong low-cost potential.

References:

1. The cost of space launches has dropped significantly in recent years

2. Space launch to low Earth orbit: How much does it cost?

3. Interstellar Shuttle: A Fantastic Journey of Reusable Rockets

4. Foreign media attention: China has taken an important step in building the "Thousand Sails Constellation"