High Temperature High Gain Antenna for BepiColombo

TSA-HTHGA-Status-Presentation ESTEC Noordwijk 2005-02-23

Technology Status Review

High Temperature High GainAntenna

forBepiColombo


1. Status of Accomplishment of the current Technology Development Activity


1.1 Objectives of TDA High Temperature High Gain Antenna

• Demonstration of critical technologies in particular

– High temperature environment

– Radiation environment• Critical technologies in this sense are:

– New materials & processes with high temperature operating capabilitiesfor the antenna reflector

– High temperature capable materials/components wrt mechanical, tribological and electrical issues for the two axes pointing mechanism

– High temperature capable materials for the RF chain (feed, waveguides, cables, transitions…)

• Very low mass antenna design


1.2 The High Temperature High Gain AntennaMain Requirements

total mass <20 kg (1.5m); < 14 kg (1.0 m)

Mass of mobile parts < 10 kg (1.5 m)

Eigenfrequencies stowed/deployed >50 Hz / >2.5 Hz

Quasi static design loads +/- 25 g along any coordinate axis

Operational Temperature Range -150 °C < T < 250 °C

Max heat flux to s/c radiative/conductive 1000 W / 10 W

Max temperature MPO top surface 150 °C

Gain X-Band frequency X1frequency X2

>38.5 dBi (1.5m) >35 dBi (1.0m)>39.8 dBi (1.5m) >36.5 dBi (1.0m)

Gain Ka-Band frequency Ka1frequency Ka2

>50.3 dBi (1.5m) >46.5 dBi (1.0m)>50.5 dBi (1.5m) >46.7 dBi (1.0m)

Cross Polarisation < - 25 dB max rel. Peak to Peak

VSWR < - 25 dB (X and Ka-Band)


1.3 The High Temperature High Gain Antenna

According to the TDA SOW the HTHGA consists of:

• The Antenna Reflector Assembly

• The Antenna Pointing Assembly

• The Radio Frequency Chain


1.3.1 The Antenna Reflector Assembly

The Antenna Reflector Assembly comprises:

• The parabolic main reflector

• The hyperbolic sub reflector

• The supporting back structure

• The tripod

..\hsf-Modelle\20050218__HTHG_Antenna_BB_Assembly.hsf


1.3.2 HTHGA DesignOverall BB Mass Budget

PART MATERIAL AMOUNT MASS [kg] FM?Main Reflector Shell C/SiC 1 2,330 3,107reflective coating Kepla 1 0,550 0,550Main Reflector Support Structure C/SiC 1 1,790 1,790Sub reflector Shell C/SiC 1 0,130 0,173reflective coating Kepla 1 0,030 0,030Sub Reflector Support Structure C/SiC 1 0,254 0,254Tripod C/SiC + Ti 1 0,719 0,719APM-Adapter-Structure C/SiC 1 0,339 0,339APM-Adapter-Flange Ti 3.7164 1 0,158 0,158Dual Feed Support 1 0,181 0,181

6,481 7,301

APM 7,467 7,467

HRM Dummies 2,223 2,160

Waveguides CFRP 0,250 0,250

Dual Feed Horn Al 1,064 1,064

Antenna BB Support Truss Steel 3,616Boom Steel 4,637 1,500Bolts & washers 0,600 0,600

26,338 20,342

Sub Total ARA

Total BB Mass


1.4 1.4 –– Thermal AnalysisThermal AnalysisUpdates Updates sincesince last PM 4last PM 4

APM Thermal Model totally updated

Feeds Thermal Model detailed

Analysis results presented for Load Case LC1.1

Perihelion / Reflector Worst case (Hot case / Mercury in Perihelion ; Cs=14499 W/m² ; CDR LC1.1)Sub-systems worst cases are currently analysedorbital parameters : CDR status

CDR AI about planet temperature and RF loss to be included, S/C internal T° TBD by ESA

SunMercury

MPO

Earth


1.4 Thermal Analysis1.4 Thermal AnalysisKey results Key results -- C/C/SiCSiC partsparts

- Reflector : Max. 422.7 °C (incl. +30K margin)

(Conical & Cylindrical Support Structure reduces the VF with Space)

- Sub-Reflector : Max. 413 °C (incl. +30K margin)

Calculated Temperatures w/o MARGINS


1.4 Thermal Analysis1.4 Thermal AnalysisKey Results Key Results -- FeedsFeeds

- Feeds : Max. 213.5 °C (incl. +30K margin)

- The thermal design of the reflector rear area has been improved to reduce the feeds max Temp. but not enough to allow the use of Aluminium w/o risks : Structural checks and material change have to be discussed

-Sheldahl : 350°C for sunshield must be acceptable, anyway, sunshield improvement TBD

-First results of the WC analysis show a significant increase of the max. Temperatures


Spec -30K margin

Spec (either max allowable material temperature or equipment spec)


Rotary Joints : Max. 180.0°C Clamp ring : Max.178.1°C

APM Bearings : Max. 178.0°C Crown wheel : Max. 175.1°C

Stator/rotor : Max. 178.7°C Motors : Max. 243.6°C

APM model update allows a fine check of the different APM components with different Max. allowable Temperatures. ( all temperatures incl. +30K Margin)

1.4 Thermal Analysis 1.4 Thermal Analysis Key results Key results -- APMAPM



1.4 1.4 –– Temperature evolution since last PMTemperature evolution since last PM

Element / Tmax consolidated (°C) CDR PM4 Actual Max. Spec Temp. evolution

422.7 N/A

N/A

N/A

N/A

TBD/Alu

290/400

N/A

N/A

250

240

300

240

240

200

417

=

=

=

300

339.1

213.7

377.2

209.2

146.4

175

180

243.6

176.5

178.7

178.1

Remark

Reflector 360.2 396.3 Reflector Rear face partly covered with MLI + CSS reduces VF with Deep Space

Sub-Reflector 398.1 406.7 Strong VF with Reflector

Conical support structure 319.3 Isolated from Reflector with MLI

Cylindrical support structure 320.2 Conductively coupled to warm reflector

Dual Feeds 235.6 270 Thermal design optimized / isolated from reflector

Sunshield 363.4 370.0 VF with Reflector and Sub-Reflector

APM Bearings

APM Rotor/Stator

WG 200.6 205.6

Lower Boom 162.2 161.4 New APM model with coherent internal dissipations distribution

APM Flange 176.2 175.1

RJ 183.9 185.9

Actuators 216.6 217 New APM model with coherent internal dissipations distribution

APM parts


1.5 Dynamic Analysis – Natural Modes

1st Natural Mode: 53.8 Hz7% Margin to required 50 Hz

5th Natural Mode: 70 Hz

First Reflector Mode


1.6 Thermal Distortion Analysis ResultsBest Fit Surface Errors

LoadcaseCorrection of rigid

body motionCorrection of rigid

body motion

RMS [µm] RMS [µm]focus shift

[mm] RMS [µm] RMS [µm]focus shift

[mm]

T750s - cold Case (CDR LC12) 26.49 12.48 -0.086 21.27 21.22 -0.009

T5500s - hot Case (CDR LC13) 25.65 25.25 0.027 40.00 36.63 0.069

T7000s - Gradient 29.38 28.11 -0.026

CDR DesignNew Design

no Analysis performed

Correction of rigid body motion and focal length

Correction of rigid body motion and focal length

ConclusionThe thermo-elastic deformations of the new design are smaller than those ofthe design of CDR status.

• Hot Case: T= 5500 s (LC13 in CDR documents)• Cold Case: T= 750 s (LC12 in CDR documents)• Maximum gradient: T= 7000 s (no CDR loadcase)• Antenna is 125 degree tilted (Hot Case configuration)


1.7 Pointing Analysis Antenna Modeling/results

• Feed System:- located at nominal position- 12dB Taper at sub reflector edge

7.15 GHzcase theta [°] phi [°] amplitude [dB] phase [°] path difference [mm]nominal 0,0000 0,0000 35,07 6,50 0,0000T750s 0,0681 -34,9523 35,06 6,40 0,0117T5500s 0,0685 -55,1856 35,05 3,60 0,3380T7000s 0,0684 -52,3502 35,05 4,30 0,2564

Position of Maximum

34.8 GHzcase theta [°] phi [°] amplitude [dB] phase [°] path difference [mm]nominal 0,0000 0,0000 49,29 -94,30 0,0000T750s 0,0684 -35,7747 49,26 -94,30 0,0000T5500s 0,0687 -55,8552 49,23 -108,20 0,3329T7000s 0,0677 -53,9836 49,20 -104,60 0,2466

Position of Maximum


1.8 ARA BB Manufacturing Status

• Laminating moulds/tools for main and sub reflectors inhouse available

• Lay-up programming and program testing for both reflectors completed

• Lay-up of both reflector shells completed

• Green body curing of both reflector shells completed

• Pyrolysation pending (tooling definition& procurement, availabilty of facility)

• Manufacturing of cone, inner cylinder and tripod tubes planned for March

• ARA assembly planned for May


1.8 ARA BB Manufacturing Status Sub Reflector Shell Lay-up


1.8 ARA BB Manufacturing Status Main Reflector Shell Lay-up


1.9 Materials & Process Sample Test Program

Thermal Cyclingin Vacuum

at ARCS

Radiation Testwith protons

at PSI

Radiation Testwith VUVat ESTEC

Life / Degradation Tests

Mechanical Tests, BOLMech. Strength

(tension, shear, ILS)Elastic Prop.

Radio Frequency, BOLReflectivityPolarisation

Optical Properties, BOLAbsorptionEmission

Thermal Tests, BOLCTECTCCp

Chemical Surface Analysis,BOLSEM

Material Characterization at Begin of Life

Mechanical Tests, EOLMech. Strength

(tension, shear, ILS)Elastic Prop.

Radio Frequency, EOLReflectivityPolarisation

Optical Properties, EOLAbsorptionEmission

Thermal Tests, EOLCTECTCCp

Chemical Surface Analysis,EOLSEM

Material Characterization at End of Life


1.10 ARA Coating Development

• Goal

– Closed functional surface coating with good bonding on the C/SiC reflector material.

• Targeted Coating System:

– Highly RF-reflecting metallic sub-layer

– Low alpha/epsilon thermal top layer with excellent resistance against harsh Mercury environment. 10µm Ni + 10µm Cu + 40µm (Al+Al2O3)-Gradient Layer


1.10 ARA Coating DevelopmentKepla Coat

C/SiC-Substrate

Kepla-Coat Cu-layer Ni-layer


2. The Antenna Pointing Assembly

The Antenna Pointing Assembly consists of:

• Pointing Mechanism Azimuth stage

• Pointing Mechanism Elevation stage

• Rotary joint for X-Band and Ka-Band

• Hold-down and release mechanisms

HTS-Presentation TSR.ppt


3. The Radio Frequency Chain

The Radio Frequency Chain consists of

• The Dual Band Feed Horn

• The X-Band and Ka-Band waveguides

RYMSA-TSR.ppt


4. What will we have after the end of the study?

• Principle of the antenna structural design demonstrated:

– BB model manufactured

– BB model vibration tested

– Thermal distortion verified by combination of material tests, thermal distortion measurement in reduced temperature range and analytical prediction

– Mechanism BB tested in reduced environment

– Feed horn tested in reduced environment

It will have been demonstrated that BepiColombo will have an HTHGA. With the current knowledge there is show stopper but there is still additional development work to be done!

NO


5. Critical Technology Items not covered by TDA Identification of Delta Development Needs

5.1 High Temperature CFRP Waveguides

5.2 High Temperature Joining/Mating Techniques for C/SiC

5.3 C/SiC Reflector Manufacturing Experience Build Up

5.4 C/SiC Coating Refinement & Process Adaptation

5.5 HT-Feed (Material Change)


5.1 High Temperature CFRP Waveguides Development Needs

• Composite Technology• Plating Technology• Soldering• Manufacturing Technology


5.2 High Temperature Joining/Mating Techniques for C/SiC

• development of HT capable ceramic bonding technique

• Mechanical mating techniques (screws, rivets)

• Tests on sample level

• Component level tests

• Establishment of the joining process

• Establishment of design guidelines


5.3 C/SiC Reflector Manufacturing Experience Build Up

There is currently no reliable experience available with respectto high precision long fibre C/SiC antenna structures. For designing the production tools a data base of the process inherent deformations due to polymer green body curing and pyrolization needs to be established.

A programme needs to be set up to determine the material shrinkage and to derive the design and process guidelines for the moulds.

The fulfilment of this task will require to manufacture a numberof full scale reflector facesheets, to convert them into ceramic, to measure the surface error, correct the tools, manufacture the next one, measure the surface, correct the tool,..... (hopefully not until eternity).


5.4 C/SiC Coating Refinement & Process Adaptation

• The principle of the coating has been demonstrated

• The roughness of the surface coating needs to be improved

• The coating process needs to be demonstrated on full scale flat plates and reflector facesheets


5.5 HT-Feed (Material Change)

• The expected temperatures of the dual feed horn may require a change of the material from Aluminium to a suitable alternative

- Identification of alternative materials

- Design adaptation

- Identification of critical manufacturing processes

- Manufacturing of a HT dual feed horn

- HT dual feed horn RF test

High Temperature High Gain Antenna for BepiColombo

Documents

Transcript of High Temperature High Gain Antenna for BepiColombo