The Long March 6 carrier rocket is the first solid bundled rocket in the mainland, and the core stage of the rocket adopts a liquid oxygen kerosene engine, and four solid engines are bundled as boosters. Different from the conventional launch vehicle ignition process, when the rocket is launched, the first stage engine of the Long Six modified carrier rocket core is ignited first, and the four solid engine boosters are ignited. Solid engines can not implement emergency shutdown once ignited, therefore, before the solid booster ignition provides a strong take-off thrust for the Long Six Modified rocket, it is necessary to diagnose the health status of the rocket core stage liquid engine, and the solid booster performs the ignition procedure under the premise of ensuring the health of the core stage engine.
So, how to do a comprehensive health check for the rocket engine before launch? The designers of the eight presidents and six changes of the rocket of China Aerospace Science and Technology Group Co., Ltd. have equipped the liquid engine of the rocket core stage with a "health steward", that is, the engine health diagnosis system. This "health steward" must accurately judge the working state of the liquid engine after starting in a very short period of time, and cannot mistakenly shut down the normal working engine due to its own failure. According to the designer, there is no precedent for the application of engine health diagnosis system in rocket launches, and the success of this launch mission further verifies the correctness of the health diagnosis system design and the reliability of engineering applications.
Fast: Health status can be determined between the whiskers
In fact, the mainland's liquid launch vehicles have a set of emergency shutdown system, this system is usually set in the ground cabinet, once in an emergency, the ground equipment can issue a shutdown command. But this time, the designers of the Long Six Rocket moved the system to the rocket. Although this integrated and miniaturized design system is only the size of a B5 book, its powerful chip computing power, rapid and accurate acquisition of engine parameters and real-time diagnosis cannot be underestimated. In 2.5 seconds after the ignition of the core-level liquid engine, the health diagnosis system enters the engine diagnostic window; from 2.5 to 2.8 seconds, in just 0.3 seconds, the "health steward" needs to diagnose the health of the engine on the basis of a large amount of data collected in the early stage: if the engine is detected to have problems, it is necessary to complete the automatic emergency shutdown of the faulty engine between the whiskers, and ensure that the solid booster no longer performs the ignition procedure, which can be described as the "strongest brain".
Quasi: "Double safety" ensures that the engine does not shut down by mistake
Can an engine health diagnostic system be reliable? What should I do if the data collection is wrong? Will I turn off the normal engine by mistake? Designers are bold in their designs and careful to verify. Massive data analysis is the basis of accurate judgment, for this reason, the designers of the Long Six Rockets have combined the engine system to conduct detailed research on the parameters of the engine health diagnosis system, find the law of parameters from tens of thousands of seconds of test data, determine the diagnostic algorithm of the health diagnosis system, and conduct hundreds of simulation verifications to ensure that the engine does not shut down by mistake, and find faults as soon as possible.
Although the diagnostic algorithm has undergone a series of tests and verifications, the designers decided to install a "double insurance" on the first flying arrow of the Changliu change. To this end, they equipped the rocket with three identical diagnostic systems to diagnose the engine state at the same time, and if there are two or more system diagnostics at the same time to determine the existence of the fault, the engine failure is considered. It's like having three referees in a game, and two or more referees judging a player to be fouled before a penalty can be imposed.
Stable: Successfully passed the test of "Ice and Fire Double Heaven"
For the health diagnosis system to work properly, it must have a healthy "body", to what extent should it be healthy? The core stage engine of the Changliu modified rocket is a low-temperature liquid oxygen kerosene engine, the temperature of liquid oxygen is minus 183 ° C, even under the protection of the "water insulation and thermal insulation suit" provided by the designer, the environment around the health diagnosis system is still minus 40 ° C; after the engine ignition, the surrounding temperature rises sharply to 130 ° C, and accompanied by strong vibration, the working environment is extremely harsh.
In order to train the health diagnosis system to strengthen the "physique", the model team carried out a large number of verification tests according to the environment at the time of take-off of the rocket, from minus 40 °C to minus 130 °C, high-strength impact, electromagnetic compatibility test, more than 1,000 intensive assessments... The product is improved again and again, and then improved after the test, and finally the product is practiced to the satisfaction of the designer. In order to assess the performance of the product in the real environment of the engine, the health diagnosis system has participated in the real test assessment of the engine for 6 times, successfully completed the engine health diagnosis, fully verified the environmental adaptability of the health diagnosis system, and laid a solid foundation for the successful first flight of the Changliu reform rocket.
Photo: Sun Gongming
Source: Beijing Daily Client | Reporter Niu Weikun Correspondent Wang Meng
Editor: Cai Wenqing
Process Editor: Dan Guo