Report on the bepicolombo critical equipment review ii
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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:

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Report on the bepicolombo critical equipment review ii

Report on the BepiColomboCritical Equipment Review II

held at ESTEC, Noordwijk, 18. Dec. 2008


Critical equipment review objectives
Critical Equipment Review Objectives

The objectives of the Critical Equipment Review are:

  • 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.

  • Identification of backup solutions and their maturity at technological and/or system design level.

  • Establishment of cut-off dates by which a decision on backup solution has to be taken.

  • Initiation of any identified near-term urgent counter-measures.

  • Recommendation on PDR schedule.

// Rappel du titre //


List of critical items reviewed

Solar Arrays

Solar Cells

Solar Array Substrate

Shunt- and Blocking Diodes

Slip Rings for Solar Array Drive Mechanism

High Temperature Cables

Antennas

Thermal and RF Coatings

Antenna Reflector Assembly

Sunshield (MOSIF) Thermal Coating

High Temperature MLI

Solar Electric Propulsion Grid Lifetime

// Rappel du titre //


Design driving critical elements

Design driving critical Elements

1_ MTM Solar Array

2_ MPO Solar Array

3_ Electrical Propulsion

4_ HGA (ARA coating, Feed, Waveguide)


Mpo orbit

MPO Orbit

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

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


Mpo solar array changes since cer i

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



Mpo power status

MPO Power Status

  • 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

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


Hga baseline and back ups for pdr

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 4/2009

Back-up: Cu sandblasted mass impact on feed and HGA (2/09)

Waveguides: Low CTE (CSiC) TDA completion 6/2009

Back-up: Ag plated Ti Process verification by 4/2009


Mass budget
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.

// Rappel du titre //





Mass risks and opportunities

Mass Risks and Opportunities

Risks:

HGA Feed failing Ag coating technology

Longer MPO yoke 1.2 % lower system margin

Separation Mechanism early development status

Opportunities:

Solar Arrays: 4 panel MTM solar array +1.4 %

Deletion of hot spot loss factor

Reduction 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


Antenna Systems

Identified Critical Technologies

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


2 mosif sunshield design

MOSIF Thermal Coating

2. MOSIF sunshield design

New baseline:

Truss framework with HT MLI

49 kg

Design at CER1:

Single screen sunshield

Sunshield: 44kg

(with reinforcements: 85kg)



Conclusion

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


Pdr schedule

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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