12.5 Typical Application of System Integration and Assembly
417
The instruments with alignment requirements included attitude control subsystem
instruments, scientific payload instruments, propulsion subsystem instrument and
separation instruments. The assembly process of instrument with alignment requirement was a process of installation and adjustment. During assembly, adjustment
should be made while the alignment is measured. The adjustment gaskets were
adjusted the alignment accuracy requirement was satisfied. In order to ensure the
alignment accuracy of instrument assembly, it was also possible to apply a positioning pin which was replaced with a screw before launch. In the Chang’E-3
lunar lander, there were instruments with alignment requirement including gyro
assembly, star sensor of attitude control subsystem, engine and thrusters of propulsion subsystem and EUV camera of scientific payload subsystems, whose alignment
requirements were higher. Two methods including adjustment gasket and positioning
pin were applied to meet the fine-tuning requirements and high-precision assembly
was achieved.
2. Assembly of Instrument with Sealing Requirement
In spacecraft, there is sealed design in many positions, which is generally applied
detachable sealed connection with sealing material including rubber sealing gaskets
and sometimes other sealing materials, such as fluorine plastic, metal and material in
special environment (such as high temperature and chemical corrosion environmental
material). For seals with elastomeric seals, a groove shall be machined at the mounting
flange or fitting to install the seal. In the Chang’E-3 lunar lander, the major seals were
the sealing of propulsion subsystem pipeline. The sealing methods of welding and
screw ball joint connection were applied with good performance.
3. Alternative Assembly
In system assembly process, sometimes the alternative of the instrument is required.
For example, the structural alternative is necessary in mass property measurement or
mechanical environmental tests. The thermal alternative to simulate thermal property is necessary in thermal environment tests. When the modules or projectile are
connected in assembly facility, the pyrotechnic alternative is used. The key of alternative assembly is the control of technical status of alternative items. In the development in parallel of the Chang’E-3 lunar lander, the alternatives were often applied in
tests. During the assembly process, the name and code number of products should
be strictly controlled and the uniqueness should be checked and confirmed. Before
launch, all alternatives in spacecraft should be strictly removed and confirmed.
4. Assembly of Ground Protection
The protection for the protrusions and key components on spacecraft surface is an
important part of system integration and assembly process, so as to prevent damage or
contamination of key components such as camera lens, plug, socket, pipe connectors,
igniter of pyro, nozzle of engine and thruster with ground protection during ground
assembly operations, transportation, test and storage. Ground protection shall be
designed in red color and hollow for warning and visual purposes. The protrusions
and key components on the surface of the Chang’E-3 lunar lander were protected in
417
The instruments with alignment requirements included attitude control subsystem
instruments, scientific payload instruments, propulsion subsystem instrument and
separation instruments. The assembly process of instrument with alignment requirement was a process of installation and adjustment. During assembly, adjustment
should be made while the alignment is measured. The adjustment gaskets were
adjusted the alignment accuracy requirement was satisfied. In order to ensure the
alignment accuracy of instrument assembly, it was also possible to apply a positioning pin which was replaced with a screw before launch. In the Chang’E-3
lunar lander, there were instruments with alignment requirement including gyro
assembly, star sensor of attitude control subsystem, engine and thrusters of propulsion subsystem and EUV camera of scientific payload subsystems, whose alignment
requirements were higher. Two methods including adjustment gasket and positioning
pin were applied to meet the fine-tuning requirements and high-precision assembly
was achieved.
2. Assembly of Instrument with Sealing Requirement
In spacecraft, there is sealed design in many positions, which is generally applied
detachable sealed connection with sealing material including rubber sealing gaskets
and sometimes other sealing materials, such as fluorine plastic, metal and material in
special environment (such as high temperature and chemical corrosion environmental
material). For seals with elastomeric seals, a groove shall be machined at the mounting
flange or fitting to install the seal. In the Chang’E-3 lunar lander, the major seals were
the sealing of propulsion subsystem pipeline. The sealing methods of welding and
screw ball joint connection were applied with good performance.
3. Alternative Assembly
In system assembly process, sometimes the alternative of the instrument is required.
For example, the structural alternative is necessary in mass property measurement or
mechanical environmental tests. The thermal alternative to simulate thermal property is necessary in thermal environment tests. When the modules or projectile are
connected in assembly facility, the pyrotechnic alternative is used. The key of alternative assembly is the control of technical status of alternative items. In the development in parallel of the Chang’E-3 lunar lander, the alternatives were often applied in
tests. During the assembly process, the name and code number of products should
be strictly controlled and the uniqueness should be checked and confirmed. Before
launch, all alternatives in spacecraft should be strictly removed and confirmed.
4. Assembly of Ground Protection
The protection for the protrusions and key components on spacecraft surface is an
important part of system integration and assembly process, so as to prevent damage or
contamination of key components such as camera lens, plug, socket, pipe connectors,
igniter of pyro, nozzle of engine and thruster with ground protection during ground
assembly operations, transportation, test and storage. Ground protection shall be
designed in red color and hollow for warning and visual purposes. The protrusions
and key components on the surface of the Chang’E-3 lunar lander were protected in