What are the characteristics of the new generation of Long March carrier rocket?

The new generation of Long March launch vehicles are mainly developed in response to the development needs of my country's aerospace industry, in line with the development trend of launch technology, and in response to the fierce competition in the international market. They are a new series of launch vehicles with obvious technical path differences and improved functional performance compared with the previous generation of launch vehicles.

The previous generation of Long March rockets supported the vast majority of satellite launches

To understand the new generation of Long March carrier rockets, we must first look back at the previous generation of Long March carrier rockets.

my country's first generation of carrier rockets was based on a toxic propellant system composed of nitrogen tetroxide and UDMH, and a main engine module with a single thrust chamber thrust of 70 tons. They were first developed by my country's Long March 2 carrier rocket and became the basis for the development of subsequent carrier rockets.

Long March 2F carrier rocket (Photo by Su Dong, a reporter from China Aerospace News)

Based on the technology of "Long March 2", a variety of series of Long March launch vehicles have been developed by bundling boosters, adding a third stage, etc., including the "Long March 2" series, "Long March 3" series, "Long March 4" series, etc.

The first-generation launch vehicles currently in service support the vast majority of my country's current satellite launch missions, covering low-Earth orbit, sun-synchronous orbit, geosynchronous transfer orbit and the farther lunar-Earth transfer orbit.

Overall idea and design concept

With the development of the times, the technical potential of the old generation of Long March rockets has been basically tapped. Against this background, my country decided in October 2006 to develop a new generation of launch vehicles. my country's new generation of launch vehicles follows the overall idea of ​​"one series, two engines, and three modules", and implements the design concept of "universalization, combination, and serialization". That is, by combining two power systems of liquid oxygen/kerosene and liquid hydrogen/liquid oxygen, three diameter rocket modules of 5 meters, 3.35 meters, and 2.25 meters, through different modular combinations, a new generation of launch vehicle series with different carrying capacities is formed to support various launch missions in my country.

Green, non-toxic, pollution-free

Looking at the new generation of launch vehicles, their biggest feature is that they are “green and non-toxic”.

my country's first generation of launch vehicles was inherited from liquid missiles, and the main propellant combination used was unsymmetrical dimethyl hydrazine and nitrogen tetroxide, which are toxic propellants. Unsymmetrical dimethyl hydrazine, in particular, is not only colorless and odorless, but can also enter the human body directly through the skin. Even if it falls to the ground, it can react with the air to produce dimethylnitrosamine, which is highly toxic to the liver, and remain in the soil and groundwater. These conventional propellants need to be strictly protected during a series of processes such as ground transportation, storage, and refueling, otherwise they will cause irreversible harm to the natural environment and human health. The treatment of conventional propellants requires huge costs, which is not in line with the international development trend of green environmental protection.

At present, mainstream launch vehicles abroad all use liquid oxygen hydrocarbon green environmentally friendly propellants. my country needs to follow the development trend in space exploration activities and achieve environmental protection and environmental friendliness. In view of this, replacing these toxic propellants with non-toxic green propellants and reducing the danger of ground launch preparations has become one of the important considerations for my country to develop a new generation of launch vehicles. The new generation of launch vehicles uses non-toxic and pollution-free liquid oxygen, liquid hydrogen, and kerosene as the main propellants.

Four new engines

The second outstanding feature of the new generation of launch vehicles is “module universality”.

In order to save development costs to the greatest extent, my country's new generation of launch vehicles has implemented the idea of ​​modular development. The most perfect embodiment of this is the engine of the new generation of launch vehicles. In the development of the new generation of launch vehicles, four new rocket engines were mainly developed, namely the 120-ton YF-100, the 50-ton YF-77, the 9-ton YF-75D, and the 18-ton YF-115.

The YF-100 rocket engine is a staged combustion cycle rocket engine that uses liquid oxygen/kerosene as propellant. The engine has a ground thrust of about 120 tons, a ground specific impulse of about 300 seconds, a nozzle diameter of about 1.4 meters, and can be throttled by 65% ​​to adjust the thrust. The YF-100 rocket engine uses an advanced oxygen-rich pre-combustion staged combustion cycle, that is, a small amount of kerosene fuel and all liquid oxygen oxidizers undergo a combustion reaction in the gas generator to generate a low-temperature high-pressure oxygen-rich gas. Such oxygen-rich gas drives the gas turbine pump to pressurize the propellant from the tank and squeeze the propellant into the main thrust chamber of the engine for combustion to generate thrust. The YF-100 rocket engine is designed for multiple uses, which enables multiple ground tests of a single engine and has the potential for reuse.

The YF-77 rocket engine is a gas generator cycle rocket engine that uses liquid oxygen/liquid hydrogen as propellant. The engine has a ground thrust of about 52 tons and a nozzle diameter of about 1.45 meters. The YF-77 rocket engine is my country's first independently developed high-thrust, ground-ignition-start hydrogen-oxygen rocket engine.

YF-77 Hydrogen-Oxygen Engine

The YF-75D rocket engine is a closed expansion cycle rocket engine that uses liquid oxygen/liquid hydrogen as propellant. The YF-75D engine has a vacuum thrust of 9 tons, adopts a dual-turbine pump in series, a pre-pump swing scheme, a nozzle area ratio of 80:1, a specific impulse of about 442 seconds, and has the ability to work in a second start.

The YF-115 rocket engine is an oxygen-rich regenerative cycle rocket engine that uses liquid oxygen/kerosene as propellant. The YF-115 rocket engine has a vacuum thrust of 18 tons, uses a gunpowder starter to start and transfer, has a nozzle area ratio of 88:1, and a specific impulse of about 342 seconds.

By combining and using these rocket engines in different quantities, a new generation of launch vehicles has been formed. The Long March 5 uses 8 YF-100s, 2 YF-77s, and 2 YF-75Ds; the Long March 5B uses 8 YF-100s and 2 YF-77s; the Long March 7 uses 6 YF-100s and 2 YF-115s; and the Long March 6 uses 1 YF-100 and 1 YF-115.

A big leap in performance

The third outstanding feature of the new generation of launch vehicles is “performance leap”.

The new generation of launch vehicles has adopted a large number of the latest international technologies. Its engine system, pressurization and delivery system, control system, measurement system, servo system, structural system, etc. are all brand new and can be compared with the world's first-class. Due to the major technological leap, the carrying efficiency has been greatly improved, and the carrying capacity has doubled or increased by orders of magnitude.

The Long March 6 carrier rocket is a three-stage tandem configuration, capable of adapting to simple facility launches, and can be launched quickly in seven days. It has a carrying capacity of 1 ton in a 700-kilometer sun-synchronous orbit. The bundled Long March 7 has a carrying capacity of 13.5 tons in low-Earth orbit and 5.5 tons in a 700-kilometer sun-synchronous orbit. The Long March 5 has a carrying capacity of 25 tons in low-Earth orbit and 14 tons in geosynchronous transfer orbit.

Long March 5 carrier rocket (Photo by Wang Lei, a reporter from China Aerospace News)

Although the Long March 5 has achieved a comprehensive expansion of its carrying capacity, it is still too extravagant as a rocket for daily use. After all, it is not easy to use such a large carrying capacity. Therefore, further improvements were made on the basis of the Long March 7 carrier rocket, namely the Long March 8 for the sun-synchronous orbit and the Long March 7A for the geosynchronous transfer orbit.

The Long March 8 carrier rocket is a two-and-a-half-stage configuration, with the first core stage inheriting the first stage of the Long March 7 carrier rocket, and the second core stage inheriting the third stage of the Long March 3A series carrier rocket. It fills the gap in my country's 3-ton to 4.5-ton carrying capacity for the 700-kilometer sun-synchronous orbit.

The first stage, second stage and booster of the Long March 7A carrier rocket basically inherit the Long March 7 carrier rocket, and the third stage basically inherits the liquid hydrogen and liquid oxygen upper stage of the Long March 3A series carrier rocket, meeting the 5.5-ton to 7-ton carrying capacity for geosynchronous transfer orbit.