X-In-the-Loop Methodology and Simulation Platform For Controller Development of Gravity-1

The Gravity-1(YL-1) launch vehicle has been extensively optimized in terms of its overall layout which in turn has increased the functional and performance demands on the control system. To thoroughly validate and verify the control system, the X-In-the-Loop simulation methodology was implemented from the verification of the YL-1's concept phase. Throughout the entire development cycle, from the initial concept demonstration to the flight test,simulations under sevral modes including Model-in-the-Loop(MiL), Software-in-the-Loop(SiL) and Hardware-in-theLoop(HiL) were executed following the V-V process which ensuring the correctness and robustness of the control system. Specifically, MiL simulation are primarily used to verify the accuracy and robustness of the control strategies and parameters. SiL simulation focused on verifying the correctness of the code implementation. Whereas HiL testing mainly checked the operational correctness of the flight control hardware, the compatibility of flight control software within the flight control computer and the correctness of hardware I/O. In addition to these, further semi-physical simulations were possible on the HiL platform by replacing models of controlled objects with real devices such as IMUs and TVC actuators. And realistic flight conditions were replicated through turntables, TVC actuator loading tables etc.to achieve a more comprehensive validation and verification of the control system.

Rapid Launch of Medium-Sized Solid Carrier Rockets at Sea With High Reliability and Convenient Intelligence

Gravity-1 solid-propellant carrier rocket utilizes a three-vertical testing and launch mode, and adopts a sea-based launch method. As the demand for satellite launches continues to grow, the scarcity of launch site resources,and the consideration of cost savings, the need for rapid testing and launch of carrier rockets has become increasingly strong. The capability of rapid testing and launch has even become one important aspect of evaluating a rocket. This paper focuses on the characteristics of the Gravity-1 solid-propellant strap-on medium-sized carrier rocket and designs and implements a highly reliable, convenient, and intelligent low-cost rapid testing and launch solution. The main aspects include the design of a highly reliable dual-redundant ground architecture and the application of ground-based shelf products.

Introduction and Prospects of Gravity-1 Launch Vehicle’s Sea-Based Three Verticals Testing and Launch Mode

Gravity-1 was the world's first carrier rocket to adopt the sea-based “three vertical” testing launch mode. This article introduces the overall layout of the launch site and the workflow of rocket testing and launch for its maiden flight mission. The process of vertical assembly, vertical testing, vertical transportation, and sea-based hot launches are explained. Additionally, it provides an outlook on the improved “three vertical” testing and launch mode for future missions, such as land-based launches, rapid launches, and remote sea launches.

Trajectory Design and Flight Result of Gravity-1 Launch Vehicle

Gravity-1(YL-1) launch vehicle completed its maiden flight from the Yellow Sea near Haiyang City, Shandong Province, on January 11, 2024, this mission successfully launched three Yunyao satellites into their 500 km orbit. The YL-1 has a performance of 4.2 tons for 500 km sun-synchronous orbit and 6.5 tons for low Earth orbit. The success of YL-1 has further enriched China's launch vehicle spectrum, and will facilitate the launch of medium and large satellites and satellite constellations. In this paper, the flight ballistic solution of YL-1 is introduced. The flight trajectory consists of seven flight segments. The trajectory design comprehensively considered the characteristics and safety requirements of the vehicle to achieve effective utilization of the performance. Through comparative analysis of the flight trajectory and the predicted trajectory, the result confirmed that the flight trajectory was consistent with the design results, the design methodology was correct, and the flight test met the expected requirements. Subsequently, the vehicle will be employed for commercial application launch services.

Application of Modelica Based Multi- Domain Modeling and Simulation for Gravity-1

In the R&D phase of Gravity-1(YL-1), a multi-domain modeling and simulation technology based on Modelica language was introduced, which was a recent attempt in the practice of modeling and simulation method for launch vehicles in China. It realizes a complex coupling model within a unified model for different domains, so that technologists can work on one model. It ensured the success of YL-1 first launch mission, supports rapid iteration, full validation, and tight design collaboration.

Practice on Gravity-1 Rocket Dynamic Characteristics Design

Since the Dongfeng-2 missile, full-vehicle modal testing has been established as an indispensable part of the development and testing of rocket and missile models. However, as rockets have been developed larger, the cost and duration of such tests have significantly increased, magnifying their impact on model development. This article follows the process of the modal testing practice of the Gravity-1 rocket, reviewing and summarizing the design process of the rocket's dynamic characteristics. Initially, the article introduces common modeling techniques for launch rockets, including the mass-beam model and the hybrid element model. It then discusses the relationship between the structural dynamics model of the launch rocket and modal testing, aiming to reduce testing costs through refined structural dynamics modeling methods. Subsequently, the article describes the dynamic characteristics design process of the Gravity-1 carrier rocket, categorizes structural parameters, and studies how the selection of structural parameters affects the predicted dynamic characteristics of the rocket. Finally, it elaborates on the design of the modal testing scheme and the dynamic characteristics design based on the test data.

Technical Characteristics and Innovations of the Gravity-1 Launch Vehicle

On January 11, 2024, the Gravity-1 launch vehicle successfully carried out its maiden flight from a mobile sea platform off the coast of Haiyang in Shandong Province, sending three meteorological satellites, Yunyao-1 satellite No. 18-20, into an orbit about 500 km above the ground. The successful debut flight of Gravity-1 broke many records such as the world's largest solid launch vehicle, the first sea-launched strap-on launch vehicle in the world, with the maximum carrying capacity of current commercial launch vehicle in China. This flight marked a big step in the field of China's commercial space launch application. A new breakthrough has been made, which is of great significance for further expanding China's diversified and large-scale launch capabilities of medium and low orbit satellites, expanding the spectrum of China's launch vehicle types, and promoting the development of space science.

High Precision Guidance System of the Gravity-1 Launch Vehicle

In the development of the Gravity-1 launch vehicle, solid rocket motors without a thrust termination mechanism created great challenges for ascent guidance. To resolve this problem, the Gravity-1 GNC system used cross product guidance in the core 2nd stage, and a nonlinear adaptive guidance algorithm in core 3rd stage, in order to achieve high orbit injection precision. On January 11, 2024, the Gravity-1 launch vehicle successfully carried out its maiden flight from a mobile sea platform off the coast of Haiyang in Shandong province, inserting its payload into a low earth orbit at an altitude of 500 kilometers, validating the guidance algorithm.

Analysis of the Gravity-1 Sea Launch System and Technical Features

Sea launch has the characteristics of flexible launching points, high landing area safety, and good economy. In recent years, it has become one of the important launch methods. Since 2019, China has carried out a total of 11 successful sea launches. The Gravity-1(YL-1) sea launch system consists of a launch vehicle system and a sea launch platform. The sea launch program includes roll on/roll off boarding, sea mooring, sea maneuvering, anchoring and positioning, system testing, and formal launch. Through the maiden flight of YL-1, the design and manufacturing technology of large tonnage dedicated launch ship, launch vehicle vertical transfer and roll on/roll off boarding technology, anti-shake technology for sea launch, simple inflatable flexible insulation protective cover technology, and remote wireless measurement and control technology have been fully verified.

Digital Simulation Platform for Satellite Launch Mission Verification

To simulate the satellite launch mission under a general platform which could be used in a full-digital mode as well as in a semi-physical way, is an important way to certify the mission design performance as well as technical feasibilities, and it relates to complex system simulation methods such as multi-disciplinary coupling, multi-language modeling as well as interactive simulation and virtual simulation technologies. This paper introduces the design of a digital simulation platform for satellite launch mission verification.The platform has the advantages of high generality and extensibility, being easy to build up. The Functional Mockup Interface(FMI) Standard is adopted to achieve integration of multi-source models. A WebGL based 3D visual simulation tool is also adopted to implement the virtual display system which could display the rocket launch process and rocket-satellite separation with high fidelity 3D virtual scenes. A configuration tool was developed to map the 3D objects in the visual scene with simulation physical variables for complex rocket flight control mechanisms, which greatly improves the platform's generality and extensibility. Finally the real-time performance had been tested and the YL-1 launch mission was adopted to demonstrate the functions of the platform.The platform will be used to construct a digital twin system for satellite launch missions in the future.