The 3 key stages:
One of the main critical aspects, when it comes to manufacturing the Harness, is the Harness thermal design. Harness is subjected to extreme temperatures in space. To prevent the Harness from being damaged by temperature stress during its lifetime and optimise its mass, subsystem manufacturers need to :
- Build the complete Harness thermal model
- Predict the Harness final flight temperatures during the full duration of the mission
- Implement the findings in the design and manufacture of the Harness.
Update the aerospace derating standards:
The wire derating factor is a scaling factor that applies to the current for single wire to account for reduced current for single wire in real-world operating conditions compared to the conditions under which the current for single wire was rated.
If the wire temperature in real-world conditions is higher than the wire temperature under which the current for single wire was rated, the wire conductor temperature will increase.
As the wire resistance is a function of the wire conductor temperature, the wire resistance will increase.
As a result, the current carrying capacity of the wire will decrease and therefore the wire will be derated.
The derating factor (K) is a function of the number of wires in the bundle (N). A high maximum wire temperature relative to the temperature under which the current for a single wire was rated implies a high derating factor which leads to a high number of wires in the bundle, which ultimately leads to an increase of mass.
The aerospace derating standards use the current of a free wire at its maximum temperature (120°C or 200°C). This approach is over-conservative for many modern spacecrafts because the temperature of wire never reaches 120°C or 200°C in most of the real cases.
It is therefore recommended to verify and update the aerospace derating standards by calculating the wire temperature by taking into account local environmental conditions and the exact physical characteristics of the wires rather than current derating rules and allow the use of validated thermal models for space harness design optimization.
How it works:
You build the 3D thermal model of Harness as a solid element using the Finite Element Method (FEM) to precisely calculate the axial and radial conduction into the bundle.
The wires of the bundle will be modelled as concentric solid cylinders according to the layers arrangements of wires, so the axial and radial conduction into the bundle will be calculated automatically.
The radiation from the external side of the shield to the environment will be computed automatically as well. The radiation between the wires and themselves into the bundle will be calculated automatically.
Results
Benefits: Known approach.
Limitations:Building the detailed thermal model of the Harness is very time-consuming.
Why it matters:
Standardising the thermal model of the Harness will both reduce time and allow the optimisation of Harness mass which affect the space system development budget.
We’re thinking:
We will build the detailed thermal model of Harness and fully parametrise all the wires properties such as power dissipated by a wire, volume of wire, radius of wire, average thermal conductivity of the wire, etc. in a way that different types of wires or layouts of bundle’s section could be analysed automatically from the same Harness thermal model.
In doing so, the users will also be able to automatically identify the worst-case layout of the bundle’s section by taking into account the wire diameter and the current in each wire.
We will validate our Harness thermal model with the testing data, and make it accessible to the entire space thermal engineers’ community via our Digital Engineer® Try it now
Share
Author
