Variable Thrust Engine Research Articles

Characterization of pintle engine performance for GO2/kerosene propellants

Liquid rocket engine with a wide range of thrust variations has drawn much attention in recent years. A GO2/kerosene deep-throttling variable thrust engine using a liquid–gas pintle injector is presented and tested with aim of characterizing engine performance, regulating capability, and heat flux distribution. Three-dimensional numerical simulations are conducted to investigate the flame appearance and spray characteristics of the engine. The SST k-omega model is used for modeling turbulence, the Wave model is used for modeling the secondary breakup, and a multi-step quasi-global combustion mechanism and eddy dissipation concept model are used for modeling combustion. The GO2/kerosene pintle engine achieves stable combustion at 0.18 ∼ 4.35 MPa with a thrust of 21.30 ∼ 864.70 N. The thrust ratio of the pintle engine is 40.6:1 indicating a deep-throttling variable thrust capability. The thrust regulation of the pintle engine using the closed-loop control has high accuracy and response speed, as well as high disturbance suppression capability. The effects of combustor pressure, spray characteristics, and reactants concentration distribution on flame appearance and heat flux distribution of the engine are studied in detail. The engine equipped with a liquid–gas pintle injector could ensure a good atomization effect and high combustion efficiency by actively adjusting the propellant injection pressure drop coefficient. This work will provide a reference for the design of the pintle injector and thermal protection system of deep-throttling variable thrust rocket engines.

The Investigation of Plume-Regolith Interaction and Dust Dispersal during Chang’E-5 Descent Stage

The plume-surface interaction that occurs as a result of a variable-thrust engine exhaust plume impinging on soil during landings is critical for future lunar mission design. Unique lunar environmental properties, such as low gravity, high vacuum, and the regolith layer, make this study complex and challenging. In this paper, we build a reliable simulation model, with constraints based on landing photos, to characterize the erosion properties induced by a low-thrust engine plume. We focus on the low-thrust plume-surface erosion process and erosion properties during the Chang’E-5 mission, aiming to determine the erosion difference between high- and low-thrust conditions; this is a major concern, as the erosion process for a low-thrust lunar mission is rarely studied. First, to identify the entire erosion process and its relative effect on the flat lunar surface, a one-to-one rocket nozzle simulation model is built; ground experimental results are utilized to verify the simulated inlet parameters of the vacuum plume flow field. Following that, plume flow is considered using the finite volume method, and the Roberts erosion model, based on excess shear stress, is adopted to describe plume-surface interaction properties. Finally, a Lagrangian framework using the discrete phase model is selected to investigate the dynamic properties of lunar dust particles. Results show that erosion depth, total ejected mass, and the maximum particle incline angle during the Chang’E-5 landing period are approximately 0.2 cm, 335.95 kg, and 4.16°, respectively. These results are not only useful for the Chang’E-5 lunar sample analysis, but also for future lunar mission design.

Iterative Guidance Algorithm for Lunar Soft Landing

A closed-form explicit guidance algorithm for the deceleration, attitude adjustment and final landing phases before lunar probe soft landing is presented in this paper. Guidance with a variable-thrust engine is extended from the iterative guidance mode (IGM) to satisfy the terminal velocity, position, and attitude constraints. The closed form expression, obtained by integrating the acceleration and shutdown time, is analysed to obtain an explicit ex-pression for the velocity and position requirements and vertical touchdown of the spacecraft toward a designated landing site with high terminal accuracy. The influence of the attitude constraint on the motion equation is analysed to calculate the attitude, which is the physical control variable for the guidance loop. The variable thrust IGM formulation ensures the least switch of the thrust magnitude profile based on the analysis result of the residual flight altitude. The simulation results demonstrate that the proposed multi-constrained iterative guidance method can help accomplish an accurate lunar soft landing and that employed the algorithm is simple and easy to implement in engineering practice.

A novel approach for optimal trajectory design with multiple operation modes of propulsion system, part 1

Efficient performance of a number of engineering systems is achieved through different modes of operation - yielding systems described as “hybrid”, containing both real-valued and discrete decision variables. Prominent examples of such systems, in space applications, could be spacecraft equipped with 1) a variable-Isp, variable-thrust engine or 2) multiple engines each capable of switching on/off independently. To alleviate the challenges that arise when an indirect optimization method is used, a new framework — Composite Smooth Control (CSC) — is proposed that seeks smoothness over the entire spectrum of distinct control inputs. A salient aftermath of the application of the CSC framework is that the original multi-point boundary-value problem can be treated as a two-point boundary-value problem with smooth, differentiable control inputs; the latter is notably easier to solve, yet can be made to accurately approximate the former hybrid problem. The utility of the CSC framework is demonstrated through a multi-year, multi-revolution heliocentric fuel-optimal trajectory for a spacecraft equipped with a variable-Isp, variable-thrust engine.

The development of 7500 N variable thrust engine for Chang’E-3

To implement orbit maneuvering, rendezvous and docking, and soft landing on planets, the throttling liquid rocket engine is preferable. The 7500 N variable thrust engine applied in the ChangE-3 prober is the first throttling liquid rocket engine in china. It can throttle fast with high precision and continuous variability based on the control commands. The trajectory correction and soft landing on the moon is accomplished. This paper provides the development of the 7500 N variable thrust engine, including the technique scenarios, the key technologies and the tests. The test and flight results show that the system is feasible, its performance is high and it works reliably.

Application of the Mira 150A variable-thrust engine to manned lunar flying systems.

Covers advancements in spacecraft and tactical and strategic missile systems, including subsystem design and application, mission design and analysis, materials and structures, developments in space sciences, space processing and manufacturing, space operations, and applications of space technologies to other fields.