Spacecraft design

Design Features

Spacecraft design In addition to the characteristics of general aircraft design, there is also its own characteristics:

1 spacecraft design is different due to the task Differences, such as communication satellites, broadcast satellites use transponders, reconnaissance satellite adopt camera and camera, Earth resource satellite has remote sensing equipment, moon spacecraft has a moon, etc. Spacecraft, structural forms of different uses are almost completely different.

2 is designed to be compared to the carrier, rail selection, weight, size, structure, electrical and environment, must be compatible with the carrier.

3 Unlike the rocket design, the spacecraft design not only considers the mechanical environment and thermal environments in the emission and reintegration, but also considers the space environment at the time of the track (see the space environmental impact).

4 spacecraft needs to be integrated with the ground test system and the subscriber station (network), coordinated with each other, and solves the long-distance information transmission problem.

5 long continuous work has a higher requirements for reliability design.

Design content

Similar to the general aircraft design, spacecraft design is usually divided into conceptual research, feasibility demonstration, program design, primary design, and decentral design 4 stages. The task of spacecraft design is to make the spacecraft load as much payload under limited weight, volume, and other constraints, which can run long-term reliably on the track, and the spacecraft that needs to return will return to the earth safe and reliably. The payload of the spacecraft refers to the special system that completes the regulatory space mission, which is the project that the spacecraft design is first determined. The main indicators of the spacecraft include: function, limited weight and size, track precision, life, economy and reliability, etc., the spacecraft used multiple times also has repeated number of times. Many spacecrafts often determine the power required to consume when feasibility demonstration, and to coordinate with the ground user system and public cabin. On this basis, it is determined that the technical pathway realized by key divisions and component projects, such as the high-precision track and attitude control of the broadcast satellite, the structure of the solar battery, high-power row wave pipe, etc. Then, it is preferred to determine the overall plan of the spacecraft and the sub-system scheme, and perform the active design after the primary design and test, finally completed engineering drawings and technical documents for normal production and use. Overall solutions include: shape and overall structure, public cabin, track and propulsion system, posture control method, thermal control, power system, tracking, telemetry, and remote control, manned and return to other design content.

Shape and overall structure Select the

spacecraft structure can be divided into ontology and can expand the components. The shape, size, and layout design of the primitive part, divide the structural space. The determination of shape and size depends primarily on the track type, stable mode, and the space limit of the carrier rectification. The shape design of the return spacecraft mainly considers aerodynamic and pneumatic heating. The shape of spin stabilizing satellites should be referred to as the spin shaft, and the three-axis stabilizing satellite can be some symmetrical multiface. The spacecraft is usually divided into several compartments in the structure, and the returned spacecraft typically only returns to reinjub weight. Solar battery wings, expandable antenna, gravity gradient rod, and the like can be unfained component requirements, so as to avoid failure of the entire flight task due to their failure.

Public cabin

The satellite service cabin for different payloads can be loaded to complete different valid loads. Earth application satellite consists of two parts: payload and guarantee the service cabin (also known as guaranteed system) that is properly operated on the track. Earth's application satellites in the same type of task is generally the same, so it is possible to design a common service cabin (ie, public cabin) to achieve a multi-purpose purpose. The public compartment design is carried out in the design of the satellite and sub-system schemes in order to properly adjust the technical state of the service cabin as appropriate under the conditions of maintaining the total weight of the satellite, can adapt to the requirements of different payloads. Modern application satellites have formed several typical structural forms, such as structures in combination of four side walls and central architectures, as a "π"-shaped member as the main body.

Track design and propulsion system

According to the mission of the spacecraft, the most favorable operational track is selected, and the energy consumption is minimized and the control is simple. It is easy to observe. Typically, track selection is limited by rocket carrying capacity, guidance accuracy, control station layout, and launch target position, often requires a propulsion system on the spacecraft, making it a motorized flight, changing the ability of the track. The solid rocket engine is simple, and the liquid rocket engine can be started multiple times. Ventively change the rails that often use large thrust. In order to correct orbit errors or achieve long-term track control, small thrust engines that can be used multiple start and work life, such as single component, two-component or other high energy propulsion systems.

Attitude Control mode

To complete the responsible task, you need to reasonably select the gesture of the spacecraft. In a certain control method, the influence of the interference torque is used to stabilize the spacecraft on the expected gesture. Commonly used posture stability: spin stability, double spin stability, stability of gravity gradient, magnetic moment stability, and three-axis stability. Spin stability, gradient gradient stability and magnetic moment stability are passive, and the precision is low. The three-axis stability is active, high precision (see aerosphere attitude control). Re-changing the gesture of the spacecraft, usually also uses active control. The choice of posture control is mainly required for the task, working life, orbit characteristics and posture accuracy of satellite. Modern spacecraft adopts spin stable and three-axis stability.

The thermal control method

The temperature of the spacecraft on the track is very large, using thermal control to control the temperature of the spacecraft (mainly internal instrumentation) within a certain range, Improve the temperature environment of the instrument and reduce the fluctuations and unevenness of the surface temperature of the spacecraft (see aerospheric heat control). The spin stability can be used to uniformly subjected to a sunshine. The selection of the transmitting window can meet the limit of thermal control on the range of the solar projection angle and the maximum shaded area time. For the mutual influence of the fever instrument, take a reasonable layout of the working procedure and the heat generation, to ensure a certain heat dissipation area, set the necessary insulation barrier, arrange the heat pipe and local electric heating on the structural frame to improve Hot environment.

Power System

The weight of the original battery (such as zinc-silver oxide battery) increases with the increase of working hours and power, and is used for spacecraft for small power short-term flight. The manned spacecraft is powered by high-power fuel cells, and the water it produces can be used for astronauts. Most spacecrafts have long life (7 ~ 10 years), and the power supply is mainly dependent on the instantaneous power that can be provided, generally up to 10 ³ ~ 10 ⁴ watt, the power is larger or away from the solar spatial detector, which is generally nuclear power. Spin stabilizing satellite typically attaches solar cells on the body side surface to constitute a body-loaded solar cell. Three-axis stabilization satellite uses a sun-to-day solar battery array power supply system, compared to the body's utilization by 3 times. The cadmium-nickel battery is charged at the sunshine area, powered in the shaded area, and its life can be improved by controlling the discharge depth and the ambient temperature. For example, the track cycle is a near-land orbital satellite of 100 minutes, and the discharge depth is generally taken by 20%, while the geosynchronous satellite can be increased to 50% to 60%. Temperature is generally controlled within 0 ~ 30 ° C. The new type of nickel-hydrogen battery is longer than the cadmium nickel battery, but has not yet been widely used (see a spacecraft power system).

Tracking, telemetry and remote control

Spacecraft tracking, telemetry and remote control equipment, together with ground measurement and control stations, to measure the operational orbit of spacecraft and various divisions Performance parameters and remote control of spacecraft. Generally, with a wide directional beam to meet the coverage requirements of the ground test station at runtime.

Manned and returned

Manned spacecraft requires a complete set of life security systems, command cabins and track cabins are completely sealed, temperatures, humidity, pressure Environmental security facilities such as control, oxygen supply, carbon dioxide purification and trace pollution control, water supply, food and waste treatment, such as water supply, feeding and waste treatment system (see Man Spacecraft Life Saving System). The aerospace manipulation system should be automatically controlled and manipulated, and there is a display device to provide a system of the shipper. Generally, there is a life-saving equipment such as lifeguards, and the astronauts push the astronaut from the carrier rocket when there is a malfunction. The orbitals of spacecraft and spaceplanes should have a gesture determination and control system that can complete a variety of tasks, and can be used as a macropo flight. Manned spacecraft is also equipped with equipment and space suit, remote robot arm, etc. The spacecraft used in one time is blunt, the axially symmetrical spin is used as the heat-insulating structure of the reanying body, and the anti-to-ground is reduced to recycle with parachute. The space planes used multiple times often use lift-based fuselage, triangular wings to fly and multiple-use thermal layers to solve pneumatic heating problems.

Design requirements

The harsh aiming requirement may affect the design of the spacecraft body and constrain for the task. In addition to known quality and power constraints, the spacecraft must be carefully designed to meet the requirements of flight laser communication terminals. Some of them consider the following aspects.

(1) Platform Jitter Environment: The harsh aim requires a requirement for the spacecraft vibration environment, which will provide a requirement for spacecraft quality balance and structural stiffness.

(2) layout: In order to provide a laser communication terminal to provide a unobstructed optical sight, a variety of constraints may be proposed to the spacecraft's layout. In particular, the laser communication terminal mounted on the spacecraft body, the spacecraft attitude must be aimed at the field of view of its optical system. If there is also an RF link, the optical system sight also needs to be aligned with the visual axis of the high gain antenna to operate at the same time in radio frequency and optical downlink. In addition, the temperature control requirements of the laser communication terminal also require a requirement for the direction of the radiator.

(3) Attitude Control Preception: The performance of spacecraft attitude control must be high enough to ensure that the gesture uncertainty, the control is not sensitive, aimed at the forefinger and the like, and the role of the laser communication aiming control subsystem. Scope. Moreover, depending on the actual aiming control loop bandwidth, it is also possible to make a constraint for the maximum allowable attitude change rate of the spacecraft that meets the desired aiming accuracy.

(4) Data Storage and Management: To allow the optical link using the ARQ protocol to run reliably, the data storage amount on the spacecraft must be greater than the expected downlink of the ground data processing time. The amount of data. For flight laser communication terminals working with tens of Mbps, such data storage requirements may be a problem that needs to be considered when designing.

(5) design requirements. The overall design requirements of technology are to ensure that spacecraft designed can meet the specific needs of users or society. Moreover, these needs are the service functions required to achieve various features such as coverage, weight loss, deep space exploration, such as communication broadcast, navigation positioning, ground observation, scientific research, manned space, Deep-space detection, etc. Spacecraft technology requirements include technical performance indicators, adapt to various external environmental requirements, life and reliability requirements and facilitating production and manufacturing requirements.

(6) economic design requirements. Economic design requirements include reducing costs and improving benefits. Benefits include economic benefits and social benefits. The size of reducing cost and improving benefits is an important factor in evaluating the advantages and disadvantage of spacecraft engineering system. Spacecraft designers need to design a spacecraft capable of producing expected benefits at the total amount of investment and investment intensity.

In the overall scheme design, make full use of public platforms and existing mature technologies are effective ways to reduce cost, reduce risks, improve efficiency; make full use of computer technology, develop and apply spacecraft multi-discipline integrated design Platform and overall simulation technology, optimize spacecraft design, shorten the design cycle, to ensure the design quality, which is another effective way to improve efficiency; make full use of system engineering concepts, use system engineering methods, strengthen management, optimize the development technology process, Shorten the development cycle, improve development quality is also an effective way to reduce costs and improve efficiency.

(7) time design requirements. Time design requirements are very important for any engineering system design. According to the concept of system engineering, a project will lose its should have the value if the development cycle is too long. Especially in the fierce competition in the market economy, the design requirements of time are greater. It is necessary to ensure fast, good, and the province's development of spacecraft that meets the user's requirements is an important goal of the overall plan design. Whether it can develop spacecraft that meets the user's requirements in a shorter time is a standard for evaluating the overall plan design.

(8) Design requirements for risk. Spacecraft belongs to high-tech, high-risk products. How to reduce the risk of spacecraft in technology, economic, time, etc., is of great significance to the overall design of spacecraft. Technical risks include significant impact on the use or benefits due to the failure of the design mistakes or spacecraft function or performance indicators fail to meet the predetermined requirements. Economic risk is that economic benefits and social benefits are too poor, or they fail to achieve expected economic benefits and social benefits. When the risk refers to the development cycle exceeds the scheduled requirements. Overall scheme design To ensure that spacecraft has no risk or reduces risk to the lowest level.