Design, Manufacture, Transport and Integration on-site in Chile of ALMA Antennas

1. Design, Manufacture, Transport and Integration on-site in Chile of ALMA Antennas • GEOMETRICAL AND MATHEMATICAL THERMAL MODELS • AND • ANALYSIS RESULTS • PM#07- 14-15 September 2006

2. INTRODUCTION • Thermal analysis has been performed on the Antenna configuration defined in the frame of the ALMA Design Concept definition phase (Design presented at PM#4 by EIE) • Both Geometrical and Thermal Mathematical Models have been deeply reviewed with the objective of increasing the Antenna modelling accuracy (more surfaces and more thermal nodes) in the different areas, resulting in a more precise input for thermal distortion and error budget analysis • A CAD based thermal software (Thermal Desktop) has been used for this phase allowing the building of more accurate thermal models and a direct exchange of the temperature output maps with Nastran for themal distortion analysis.

3. SUMMARY • A set of analysis results for the whole antenna has been generated by Alcatel Alenia Space Italia, in the frame of the Antenna design consolidation phase, as input for the execution of the thermal distortion analysis. • The following activities have been done by AASI: • Re-building of the Geometrical Mathematical Model (GMM) and the Thermal Mathematical Model (TMM) • Thermal analysis covering the operational scenario for the relevant load cases • Generation of the temperatures maps for the thermal distortion analysis

4. Thermal Modelling Activity • GMM • The GMM of the Antenna has been completely re-built by using Thermal Desktop (CAD based S/W) on the basis of the design consolidation activities (relevant geometrical data taken from 3D PROENGINEER CAD model). • Detail level already reached with the previous THERMICA GMM has been generally further improved by increasing the nodal resolution and including the main surface singularities of the CAD model • In addition, the following Antenna parts have been added and properly modelled: • BUS radial and circular ribs • Cabin Receiver internal structure • Yoke arms and Yokes base internal structure

5. Thermo-Optical properties • All the external surfaces are white painted except the sub-reflector and the Antenna reflector panels. • The antenna sub-reflector surface is anodized aluminium (Alodine 1200 in accordance to MIL-C-5541-class 1A). • The external skin of the reflecting panels is electroformed nickel coated with a rhodium film. Aiming at minimizing its specularity, the surface is engraved in order to have the necessary reflectivity and enable the direct observation of the sun.

6. Thermal Modelling Activity GMM (Cont’d) ALMA OVERALL GEOMETRICAL MODEL

7. Thermal Modelling Activity GMM (Cont’d) BASE Nodal Breakdown

8. Thermal Modelling Activity GMM (Cont’d) Nodal Breakdown of Yoke Base and Arms Internal Structure

9. Thermal Modelling Activity GMM (Cont’d) Yoke Nodal Breakdown (Overall View)

10. Thermal Modelling Activity GMM (Cont’d) Cabin External Nodal Breakdown (internal node numbering scheme: external nodes + 9) 1413 1500 1501 1412 1502 1411 1503 1410 1504 1409 1505 1408 1506 1507 1407 1406 1508 1509 1405 1510 1404 1511 1512 1402

11. Thermal Modelling Activity GMM (Cont’d) Cabin Internal Nodal Breakdown

12. Thermal Modelling Activity GMM (Cont’d) BUS Thermal Model Overall View

13. Thermal Modelling Activity GMM (Cont’d) BUS Secondary Region Nodal Breakdown

14. Thermal Modelling Activity GMM (Cont’d) BUS Upper Closure Nodal Breakdown

15. Thermal Modelling Activity GMM (Cont’d) BUS Circumferential and Radial Ribs Overall Thermal Model

16. Thermal Modelling Activity GMM (Cont’d) Reflector Nodal Breakdown Reflector Nodal Breakdown corresponds to BUS Upper Closure Nodal Breakdown

17. Thermal Modelling Activity GMM (Cont’d) Legs Nodal Breakdown (42 thermal nodes for each leg)

18. Thermal Modelling Activity GMM (Cont’d) Apex and Subreflector Nodal Breakdown Apex Subreflector

19. Thermal Modelling Activity • Thermal Mathematical Model • The TMM of the Antenna has been updated by using SINDA FLUINT S/W in the following steps: • Introduction of the linear conductors network, the radiative network and the thermal loads generated by Thermal Desktop. • Introduction of the routine to properly simulate the radiative exchange in the terrestrial environment (including contribution from water vapour radiation emission) • Accounting of the convective exchange with atmosphere through the heat transfer coefficients provided by the CFD analysis for the considered wind condition

20. Thermal Modelling Activity • Analysis Cases • Thermal Analysis campaign is aimed at supporting the Antenna design consolidation phase activities and providing input thermal loads in the frame of the thermal-distortion analysis and error budget • Eight nominal analysis cases have been identified which are suitable to meet both the above scopes. This presentation covers only six of the investigated cases that are considered relevant for the thermal distortion and error budget. The analysis results for the other two identified cases will be incorporated in the thermal analysis document. • Thermal analysis output temperatures are available for the structural finite elements model through direct mapping of the thermal node temperatures into the structural model.

21. Analysis Cases Summary

22. Analysis Cases Description • Case 1 provides the maximum temperatures on the Antenna and, consequently, the maximum absolute temperature differences with respect to the temperature of the antenna during its integration. Itis the absolute hot case; maximum temperature values are reached on the reflecting panels, whereas the other components are in the shadow of the Reflector • Case 2 provides the minimum temperatures on the Antenna and, consequently, the maximum absolute temperature differences with respect to the temperature of the antenna during its integration • Cases 3, 4 and 5 provide the maximum temperature gradients on the structure along the three co-ordinate axes • Case 6 represents a critical hot case for BUS, Cabin, Yoke and Base

23. AnalysisResults • Summary of min/max temperatures of the Antenna main areas and maximum solar flux absorbed in the secondary focal region: • The maximum absorbed flux of 0.05 W/cm2 is obtained in the Case 1 (worst hot case 1) • The design is compliant to the requirement (<0.3 W/cm2)

24. Analysis Case 1 - Temperature Maps

25. Analysis Case 2 - Temperature Maps

26. Analysis Case 3 - Temperature Maps

27. Analysis Case 4 - Temperature Maps

28. Analysis Case 5 - Temperature Maps

29. Analysis Case 6 - Temperature Maps

30. Conclusions • Debugging and validation of the analysis flow has been completed. • Coherence with the analysis results obtained using the previous thermal models has been checked. • Exchange of the temperature maps for thermal distortion analysis has been successfully done • No criticalities in the antenna temperatures are shown by the current analyses • No critical temperatures are obtained for the apex and subreflector areas • Final verification is to be done by thermal-distortion analysis and error budget, considering also analysis cases 7 and 8 that introduce a high thermal gradient on Antenna Reflector, Bus and Cabin. • The final Antenna design will be extensively analysed in order to verify and demonstrate that all the requirements are met.