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 • THERMAL MODEL UPDATING AND ANALYSIS RESULTS • PM#03- 05-06 April 2006

2. INTRODUCTION • Thermal analysis has been performed on the Antenna configuration as it was at ALMA Kick-Off meeting • Main objectives were: • To debug and validate the analysis flow checking the tools used for exchanging temperature maps for thermal distortion analysis • To support the successful completion of the Design Concept definition phase

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 re-design, as input for the execution of the thermal distortion analysis. • The following activities have been done by AASI: • Updating of the Geometrical Mathematical Model (GMM) and the Thermal Mathematical Model (TMM) • The thermal analysis for significant load cases covering the operational scenario and generation of the temperatures maps for the thermal distortion analysis

4. Thermal Modelling Activity • GMM • The GMM of the Antenna has been updated in the following areas by using THERMICA S/W on the basis of the re-design activities (relevant geometrical data taken from 3D PROENGINEER CAD model): • Antenna Base • Electrical Distribution and Switchboard Control Cabinet • Electrical Cabinet for Nutator • UPS Cabinet • Battery Box • HVAC Main Unit • Outdoor Cryogenic Compressor • Elevation Drive

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 External Skin Nodal Breakdown (Internal skin numbering = External Skin + 500)

8. Thermal Modelling Activity • GMM (Cont’d) • BASE and Cylinder Thermal Protection Nodal Breakdown

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

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

11. Thermal Modelling Activity GMM (Cont’d) Yoke Arms Nodal Breakdown

12. Thermal Modelling Activity GMM (Cont’d) Brakes Nodal Breakdown (numbering scheme: Brake –Y nodes  Brake +Y nodes + 1000) View +X -Y View -X +Y

13. Thermal Modelling Activity GMM (Cont’d) Cabin External Nodal Breakdown (internal node numbering scheme: external nodes + 9)

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

15. Thermal Modelling Activity GMM (Cont’d) BUS Nodal Breakdown

16. Thermal Modelling Activity GMM (Cont’d) Reflector Nodal Breakdown

17. Thermal Modelling Activity GMM (Cont’d) Legs Nodal Breakdown Leg 1/2 Leg 7/8 Leg 5/6 Leg 3/4 Legs 5/6 and 7/8 Legs 1/2 and 3/4

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 ESATAN S/W in the following steps: • Introduction of the linear conductors network, the radiative network and the thermal loads generated by THERMICA. • 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 redesign activities and providing input thermal loads in the frame of the thermal-distortion analysis. • Eight nominal and one sensitivity analysis cases have been identified which are suitable to meet both the above scopes. • Thermal analysis output temperatures are available for the structural finite elements model through a specific procedure for mapping 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 • Case 7 provides the maximum absolute temperature differences with respect to the integration temperature of the antenna (like Case 1), but with the sun that partially illuminates the Reflector panels to have the maximum gradient on the Antenna Reflector • Case 8 provides the maximum temperature gradient on the Antenna Reflector and between Reflector and BUS, having the sun that partially illuminates the Reflector panels and the cold wind on the BUS • Case 9 provides sensitivity to the thermo-optical properties of the Antenna Reflector panels with respect to the identified worst hot case (case 1).

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. Sensitivity to Reflector Panels Thermo-Optical Properties (Case 9) • Passing from an / ratio of 4 (nominal cases with rhodium film on the reflector panels) to about 8.4 (corresponding to rhodium film removal  Case 9), the absorbed solar flux is retained in the system and the temperature of the antenna reflector could reach the peak of 170°C in the area around the focal plane (namely in the zone with the lower view factor toward the environmental sinks).

31. Conclusions • Debugging and validation of the analysis flow has been completed. • Tool used to exchange temperature maps for thermal distortion analysis has been successfully verified • No criticalities in the antenna temperatures are shown by the current analyses • 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. • As shown by sensitivity analysis (Case 9), thermo-optical properties of rhodium film applied over the reflector panels would avoid high panel temperatures in the extreme worst hot case 1 (hot conditions, no wind, Antenna pointed directly to the Sun). • The final Antenna design will be extensively analysed in order to verify and demonstrate that all the requirements are met.