The design of the spacecraft covers a large area, including the design of robotic spacecraft (satellites and planetary probes), and spacecraft for outer space (space shuttle and space station).
Video Spacecraft design
Origin
The design of the spacecraft was born as a discipline in the 1950s and 60s with the advent of the American and Soviet space exploration programs. It has since grown, though it is usually less than comparable terrestrial technology. This is for the most part due to the challenging space environment, but also the lack of basic R & D, and other cultural factors in the design community. On the other hand, another reason for the slow travel application space design is the high energy cost, and low efficiency, to achieve orbit. This cost may be seen as an "overhead" that is too high.
Maps Spacecraft design
Engineered area involved
The design of the spacecraft brings together aspects of various disciplines, namely:
- Astronautics for mission design and design requirements derivation,
- System engineering to maintain the basic design and subsystem requirements derivation,
- Communication techniques for the design of subsystems that communicate with the ground (eg telemetry) and do various things.
- Computer engineering for the design of on-board computers and computer buses. This subsystem is based primarily on terrestrial technology, but unlike most of them, it must: address the spatial environment, become highly autonomous and provide higher fault tolerance.
- This can combine the chamber components that are hardened with quality radiation.
- Software engineering for on-board software running all on-board applications, as well as low-level control software. This subsystem is very similar to terrestrial real-time design and embedded software,
- Electrical engineering for the design of power subsystems, which generate, store, and distribute electrical power to all equipment on the plane,
- Control theory for attitude design and orbit control subsystem, which directs the spacecraft correctly, and maintains or alters the orbit according to the mission profile; the hardware used for actuation and sensing in space is usually very specific to the spacecraft,
- Thermal engineering for the design of thermal control subsystems (including radiators, insulation and heaters), which maintain environmental conditions compatible with the operation of spacecraft equipment; This subsystem has very specific space technology, because in space, radiation and conduction typically dominate as a thermal effect, by contrast with Earth where convection is usually the main one,
- Propulsion techniques for the design of the propulsion subsystem, which provides the means of transporting the spacecraft from one orbit to another,
- Mechanical engineering for the design of spacecraft structures and mechanisms, as well as the selection of materials for use in a vacuum. This includes beams, panels, and enhancements or attachable separation devices (to separate from the launch vehicle).
Spacecraft Subsystem
Structure
The spacecraft bus carries a load. The subsystem supports payload and helps in pinpointing the payload correctly. It puts the charge in right orbit and keeps it there. It provides household functions. It also provides orbit and maintenance of attitudes, electric power, commands, telemetry and data handling, structure and rigidity, temperature control, data storage and communications, if necessary. The payload bus and the spacecraft may be different units or may be merged units. The booster adapter provides an interface carrying the load with the vehicle (payload and shared bus spacecraft).
The spacecraft may also have a propellant load, which is used to push or push the vehicle up, and the stage of the propulsion kick. Commonly used propellants are compressed gases such as nitrogen, liquid such as monopropellant hydrazine or solid fuel, used for speed correction and attitude control. In kicking stages (also called apogee boosters, propulsion modules, or integral propulsion stages) a separate rocket motor is used to send the spacecraft into orbit of its mission. When designing a spacecraft, the orbit to be used should be considered to the point as it affects the attitude control, thermal design, and power subsystem. But this effect is secondary to the effect it has on the charge due to orbit. So when designing missions; designers choose such an orbit that improves payload performance. The designer even calculates the performance characteristics of the required spacecraft such as pointer, thermal control, power quantity, and duty cycle. The spacecraft is then made, which meets all requirements.
Attitude Determination and Control of Attitude
Attitude determination and subsystem control (ADCS) are used to change the attitude (orientation) of the spacecraft. There are several external torques that work on the spacecraft along the axis passing through its center of gravity that can redirect the ship in any direction or can rotate. ADCS cancels these torques by applying equal and opposite torque using propulsion and navigation subsystem. The moment of body inertia must be calculated to determine the external torque which also requires determination of the absolute attitude of the vehicle using the sensor. The property called 'gyroscopic stiffness' is used to reduce the spinning effect. The simplest spacecraft achieves control by spinning or interacting with Earth's magnetic or gravity fields. Sometimes they are out of control. The spacecraft may have several bodies or they attach to important parts, such as the arrangement of the sun or a communication antenna that requires an individual pointing attitude. To control the attitude of frills, actuators are often used, with separate sensors and controllers. Different types of control techniques used are:
- Passive Control Technique.
- Spin Control Techniques.
- Three-axle Control Technique.
Telemetry, Tracking, and Command
Telemetry, tracking, and orders (TT & amp; C) are used for communication between spacecraft and land systems. The functions of the subsystem are:
- Control the spacecraft by the operator on earth
- Receive uplink commands, process and send them to other subsystems for implications.
- Receive downlink commands from subsystems, processes and send them to earth.
- Inform constantly about the position of the spacecraft.
Communications
The process of sending information to the spacecraft is called uplink or forward link and the reverse process is called downlink or return link. Uplink consists of commands and start tones where as downlink consists of telemetry status, start tone and may even include charge data. Receivers, transmitters and wide-angle antennas (hemispheric or omnidirectional) are major components of basic communications subsystems. Systems with high data rate can even use directional antennas, if required. Subsystems can give us coherence between uplink and downlink signals, with the help of which we can measure the tariff-doppler shift. The communication subsystem is measured by data rate, permissible error rate, communication path length, and RF frequency.
Most spacecraft communicate using radio antennas - satellite communications. Some spacecraft communicate using lasers - either directly to the ground as with LADEE; or between satellites such as with OICETS, Artemis, Alphabus, and European Data Relay Systems.
Power
The power power subsystem (EPS) consists of 4 subunits:
- Resources (Batteries, solar cells, fuel cells, thermoelectric pairs)
- Storage unit (Number of batteries in series)
- Power Distribution (Wiring, turning on, shock protection)
- Power Settings and Controls (To prevent overcharging and overheating)
Thermal
The thermal control subsystem (TCS) is used to keep the temperature of all spacecraft components within certain limits. The upper and lower bounds are defined for each component. There are two limitations, namely, operational (in working conditions) and survival (in non-working conditions). Temperature is controlled by using insulators, radiators, heaters, lattice and by providing a proper surface finish to the components.
Propulsion
The main function of the propulsion subsystem is to provide a boost so as to alter the translation speed of the spacecraft or to apply torque to change its angular momentum. There is no requirement of impulse and therefore there is not even a requirement of propulsion equipment in the simplest spacecraft. But many of them need a controlled boost in their systems, so their design includes some form of meter drive (a propulsion system that can be turned on and off in a slight increase). The thrusts are used for the following purposes: to change the orbital parameters, to control attitudes during thrusts, correct speed errors, maneuvers, against the power of interference (eg, drag), and control and correct angular momentum. The propulsion subsystem includes propellant, tank, distribution system, pressure, and propellant control. It also includes a booster or engine.
References
- Wertz, James R.; Wiley J. Larson (1999). Space and Design Mission Analysis (3rd ed.). Kluwer Academic Publishers. ISBN: 1-881883-10-8.
- "Solar flying screens from science fiction come true". Popular Mechanics .
Source of the article : Wikipedia
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