Post on 01-Feb-2016
description
Report on the BepiColombo
Critical Equipment Review II
held at ESTEC, Noordwijk, 18. Dec. 2008
Critical Equipment Review Objectives
The objectives of the Critical Equipment Review are:
1. Assessment of the status of readiness and the development schedule of critical equipment items, for which a Technology Readiness Level (TRL) of 5 (“Component and/or breadboard validation in relevant environment”) has not been fully reached.
2. Identification of backup solutions and their maturity at technological and/or system design level.
3. Establishment of cut-off dates by which a decision on backup solution has to be taken.
4. Initiation of any identified near-term urgent counter-measures.5. Recommendation on PDR schedule.
19/12/2006// Rappel du titre // 2
List of critical items reviewedSolar Arrays
Solar CellsSolar Array SubstrateShunt- and Blocking DiodesSlip Rings for Solar Array Drive Mechanism
High Temperature CablesAntennas
Thermal and RF CoatingsAntenna Reflector Assembly
Sunshield (MOSIF) Thermal Coating High Temperature MLISolar Electric Propulsion Grid Lifetime
19/12/2006// Rappel du titre // 3
Design driving critical Elements
1_ MTM Solar Array
2_ MPO Solar Array
3_ Electrical Propulsion
4_ HGA (ARA coating, Feed, Waveguide)
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MPO Orbit
Page 5
MTA = 114° MTA = 90°
MTA = 38°
MTA
SUNMTA = 0°0.31 AU
Perihelion
MTA = 180°0.47 AUAphelion
MTA = Mercury True Anomaly
MTA = 270°
One revolution of Mercury around Sun: 88 Earth days
One Mercury day: 59 Earth days
MPO orbit inertially fixed
MTM Solar Array Changes since CER I
Status at CER I:
Compliant power output assuming 230 °C qual. Temp. (BC-ASO-TN-69257)
PDR Baseline today:
Changed to 5p to avoid temperature > 200 °C qual. temp. (CER I recommendation). Less risk, proof by test until 5/2009.
Provides surplus power before Venus for partial compensation of SEP Isp reduction
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Baseline 4 p 34.8 m² 222.9 kg nom.
Growth Potential 5 p 40.8 m² 262.9 kg nom.
Baseline 5 p 40.8 m² 288.4 kg nom.
MPO Solar Array Changes since CER I
Status at CER I:
Compliant power output for baseline assuming 230 °C qual. Temp. (BC-ASO-TN-69256)
PDR Baseline today:
1 string less due to HDR design inside panel Power analysis targeting for minimum solar array temperature
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CER I Baseline 15 string/p 6.8 m² 46.6 kg
Growth Potential 20 string/p 8.22 m² 56.25 kg
PDR Baseline 19 string/p 8.22 m² 56.25 kg
Update of SA sizing parameters
.
Page 8
Modified Cosine law for high temperatures ↓
Miss-pointing reduced from +/-1° to +/- 0.5 deg ↑
Progressive UV degradation calculated over life time
MTM
MPO
↑
→
Gridfinger degradation removed ↑
3G28 cells with Al AR coating (-5% power) MPO ↓
Qual. Temperature 200°C instead 230°C ↓
20 mA reverse current Diodes (instead 2 mA) ↓
MPO Power Status
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P/L S/C
230°C compliant nominal
ca.6000 esh 1590 Watt (180 W)
205°C compliant nominal nominal
1055 Watt (100 W) (Ka-Band off)
230°C
3000 esh230°C
3000 esh
230°C nominal120 esh 840 W off (Ka-Band off)
Operations
nominal
Mercury True Anomaly(MTA)
SA PowerMaximum
Temperature
(Ka-Band off)
(Ka-Band off)
Aphelium
Perihelium
1100 W nominal
Survival Mode
840 W offMTA 20-50°
Baseline(5 days)
MTA 20-50° Longer Yoke
•Fully power compliant except for MTA 20-50° baseline (11 % of Mercury year)
•Compliance for MTA 20-50° achievable by longer yoke
•Solar Array temperature 200-230 °C for about 9120 esh
Electrical Propulsion
Status at CER I:– Grid erosion problem identified (Working group initiated)
PDR Baseline today:
Use of unmodified grid design and beam voltage (schedule)
Implement Anode Voltage reduction to 31 V according to 2000 h test • Isp reduced from 4640 s to 4378 s • Mass Impact Xe + 28.5 kg - 1.2 % system margin
Surplus SA power until Venus allows higher thrust in early cruise • 20 % higher thrust saves delta v of 146 m/s• Xe saving -12 kg + 0.5 % system margin
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HGA baseline and back-ups for PDR
HGA Reflector: Thermal coated Ti TBC by HT RF reflectivity test Back-up: Bare Ti TBC by HT RF reflectivity test
Antenna Feed: Ag plated Ti Process verification by 4/2009Back-up: Cu sandblasted mass impact on feed and HGA (2/09)
Waveguides: Low CTE (CSiC) TDA completion 6/2009Back-up: Ag plated Ti Process verification by 4/2009
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Mass Budget
Mass margin achieved for PDR design amounts to 14.0%. • Positive result: This takes into account robust design solutions for Solar
Arrays, Solar Electric Propulsion and Chemical Propulsion System. • Risks: Finalisation of SCA at high temperature still not completed.
The Board recommends … “that full evidence and traceability of the sources of mass estimates be provided immediately, that a mass risk assessment be consolidated and that a working level review be conducted.” This translates that also for the MMO these data shall be available on demand by the PDR Board.
19/12/2006// Rappel du titre // 12
Trend Charts of dry mass
Page 13
Trend of MTM Mass from TT1 to CER2
0
50
100
150
200
250
300
350
400
Mai 08 Jun 08 Jul 08 Aug 08 Sep 08 Okt 08 Nov 08 Dez 08
PowerMEPSStructureThermalCPSHarnessMechanismsDMSAOCSTT&C
Definition of solar array loss factors
TT1
PM11
PM12
PM13PM14
Re-Definition of solar array loss factors + SAA characterisation up to 82deg + Smaller Battery
TPA mass saving (harness + pos. Sensor)
CLA feed-back (stiffening)
TT1 improvements
Higher PCDU loss factors + Ti layers in HT MLI Increased PPU dissipation more HPs
Higher PCDU dissipation
CER2Solar Array
update
m [kg]
Trend Charts of dry mass
Page 14
Trend of MPO Mass from TT1 to CER2
0
50
100
150
200
250
Mai 08 Jun 08 Jul 08 Aug 08 Sep 08 Okt 08 Nov 08 Dez 08
Structure
Thermal
Coms
Power
CPS
Harness
AOCS
DMS
Mechanism
Mag Boom
CLA feed-back (stiffening)
PM12 PM13PM14
PM11
TT1
Height increase + radiator size increase
Radiator growth MLI area increase
Ti layers in Blankets
Definition of solar array loss factors
Re-Definition of solar array loss factors
Additional Failure Correction
CER
Assessment from subco for latest launch mass
Brackets
m [kg]
Trend Charts of dry mass
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Trend of MOSIF Mass from TT1 to CER2
0
20
40
60
80
100
120
Mai 08 Jun 08 Jul 08 Aug 08 Sep 08 Okt 08 Nov 08 Dez 08
MOSIF total
Sunshield thermal
Structure
Mechanism
Harness
MLI
AOCS
TT1PM11
PM12
PM13 PM14
Sun sensor bktstiffening deleted
MOSIF cold plate + radiator
thicker coating (50 micron layer)
MMO protection & Stack Analysis feedback
Aluminium to Titanium
CER2
m [kg]
Mass Risks and Opportunities
Risks:HGA Feed failing Ag coating technologyLonger MPO yoke 1.2 % lower system marginSeparation Mechanism early development status
Opportunities:Solar Arrays: 4 panel MTM solar array +1.4 %
Deletion of hot spot loss factorReduction of solar array contamination (by analysis)Dual Junction Cell for MPO BR Reflective cover glass coating optimised for 75°
SAA
Mass impact of opportunities will be assessed for PDR
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Page 17
At CER-1 the following technologies were identified as critical, and so plan/actions to manage them were presented
Thermal Coatings: potentially needed to reduce the temperature of exposed surfaces
RF Coatings: potentially needed for better RF performance of selected materials (i.e. Ti for ARA)
Antenna Reflector Assembly (ARA) Materials: to cope with the predicted temperatures
Feed and Waveguides: Material & technologies needed to cope with RF/RSE requirements
Antenna Pointing Mechanism (APM): improve system I/F to not exceed technology temp. limit
Following actions were assigned by the Board in the frame of CER I:- TN on RSE performance in case of HGA in uncoated Titanium- RF Characterisation of ARA uncoated Titanium- Update MGA & HGAAPA ITT with relaxed TH requirement to get updated
proposals
Identified Critical Technologies
Antenna Systems
2. MOSIF sunshield design
Page 18
Design at CER1:Single screen sunshield
Sunshield: 44kg (with reinforcements: 85kg)
New baseline:Truss framework with HT MLI
49 kg
MOSIF Thermal Coating
Summary of PDR Baseline
Page 19
Baseline Back-up
MTM SA 40.8 m² Trajectory change
MPO SA 8.2 m² Dual Junction Cell
SEPS Low Isp 4378s
No modification
HGA ARA
WG
Feed
Ti with term. coating
Low CTE WG
Ag plated Ti
Bare Ti
AG plated Ti
Cu sandblasted
Conclusion
1_ Design baseline and back-ups for critical technologies are defined for PDR
2_ The system mass margin is below 20 % for PDR
3_ SA temperatures require cell qualification for 230°C/4 SC for 9120 esh
Page 20
PDR schedule
Planning of System PDR dates (TBC CER-board):
– PDR DP inputs of core team to ASD 13 Feb 09– Delivery of System Data Package to ESA 6 Mar 09– Kick/off Meeting / Presentation at ESA 10 Mar 09– RIDs to Industry 22 Apr 09– Answer to RIDs to ESA 30 Apr 09– Colocation Meetings 4/7 May 09– System PDR Board Meeting 29 May 09
For information, the next SPC is planned on 17/18 June 09
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