BepiColombo Mission and the Solar Electric Propulsion System (SEPS) - - PowerPoint PPT Presentation

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BepiColombo Mission and the Solar Electric Propulsion System (SEPS) - - PowerPoint PPT Presentation

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BepiColombo Mission and the Solar Electric Propulsion System (SEPS) Neil Wallace 17/ 10/ 2018 ESA UNCLASSI FI ED - For Official Use BepiColombo Mission to the planet Mercury ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018

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ESA UNCLASSI FI ED - For Official Use

BepiColombo Mission and the Solar Electric Propulsion System (SEPS)

Neil Wallace 17/ 10/ 2018

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ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 2

BepiColombo

Mission to the planet Mercury Launch: 0 2 :4 5 :3 8 BST, 2 0 th Oct 2 0 1 8

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ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 3

BepiColombo – why explore Mercury?

  • Mercury is the missing piece to better

understand the evolution of our Solar System – it is a planetary ‘odd-ball’

  • Data that can be acquired from ground

based observations is very limited

  • Two space science missions have

previously explored Mercury:

  • Mariner 10 (flyby – 1974)
  • MESSENGER (orbital mission, 2011/ 2015)
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ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 4

BepiColombo – why explore Mercury

  • The BepiColombo mission will place two independent spacecraft, each

containing a suite of scientific instruments, in different Mercury orbits to follow- up on the MESSENGER findings and investigate:

  • Origin and evolution of a planet close to the parent star
  • Interior structure, geology, composition, surface composition and craters
  • Vestigial atmosphere (exosphere): composition and dynamics
  • Magnetized envelope (magnetosphere): structure and dynamics, dual spacecraft

mission to separate inner and outer fields,

  • Origin of magnetic field
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ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 5

BepiColombo – Main challenges

  • Mercury is innermost planet in the solar

system, 0.3AU from the Sun:

  • Spacecraft needs to survive the extreme

thermal environment with different s/ c surfaces exposed simultaneously to 15kW/ m 2 (10 Solar constants), planetary surface temperatures up to 450°C and 4K deep space

  • Large amount of energy needed to

manoeuvre between Earth to Mercury orbits

  • Forces a unique spacecraft configuration

employing high specific impulse (SI) electric propulsion (EP)

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ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 6

MTM Mercury Transfer Module MPO Mercury Polar Orbiter MMO Mercury Magnetospheric Orbiter MOSIF MMO Sun-shield and interface

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ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 7

BepiColombo – spacecraft configuration

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ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 8

BepiColombo – spacecraft configuration

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ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 9

BepiColombo – spacecraft configuration

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ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 10

Launch m ass: 4 ,1 0 0 kg

  • MPO P/ L: 80 kg
  • MMO P/ L: 45 kg
  • MPO: 1,150 kg
  • MMO: 285 kg
  • MTM: 1,160 kg, Xenon fuel: 580 kg
  • MTM Chemical fuel: 160 kg
  • MPO Chemical fuel 670 kg

Delta-V

  • 4000 m/ s electrical cruise
  • 80 m/ s chemical cruise
  • 1,000 m/ s chemical orbit descent

MTM Propulsion:

  • 4 x 145 mN ion engines,
  • Isp = 4,200s, 290 mN max
  • 16 x 10 N thrusters, 8 x 22 N thrusters

Dim ensions:

  • Overall height 6.3m
  • Span: 30.4 m
  • Solar Array: MTM: 13,200 W, 2 x 21 m 2
  • Solar Array: MPO: 2,000 W, 8.2 m 2

MPO Propulsion:

  • 8 x 5 N thrusters
  • 8 x 22 N thrusters
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ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 11

  • The spacecraft employs a high

temperature multi-layer insulation (MLI), includes a titanium ceramic outer layer to protect all spacecraft surfaces exposed to solar illumination

  • r Mercury albedo

BepiColombo – Thermal solutions (MPO)

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ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 12

  • Cannot encapsulate the entire spacecraft

because the MPO also needs to reject waste heat generated within its own interior –

  • Solution a radiator that allows simultaneous

heat rejection from the planet and from the spacecraft

BepiColombo – Thermal solutions (MPO)

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ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 13

BepiColombo – Thermal solutions (MPO)

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ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 14

  • The MTM also employs a

sun-shield to shadow the underside of the spacecraft and the ion thrusters

  • The shape of the MTM is

designed to have the side radiator panels always in shadow

  • The high dissipation

electrical units are located

  • n these panels directly

mounted to heat-pipes to spread the heat across the entire panel

BepiColombo – Thermal solutions (MTM)

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ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 15

BepiColombo – Thermal solutions (MTM)

  • The MTM also employs a

sun-shield to shadow the underside of the spacecraft and the ion thrusters

  • The shape of the MTM is

designed to have the side radiator panels always in shadow

  • The high dissipation

electrical units are located

  • n these panels directly

mounted to heat-pipes to spread the heat across the entire panel

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ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 16

  • The orientation of the

MTM and MPO Solar arrays are constantly varied as a function of solar distance to reduce the energy density and maintain array within thermal design limits

  • The leading edge of the

array and the yoke are also shielded to prevent direct solar illumination

BepiColombo – Thermal solutions (MTM)

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ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 17

BepiColombo – the journey to Mercury

Professor Giuseppe ‘Bepi’ Colom bo ( 1 9 2 0 – 1 9 8 4 ) University of Padua, I taly

http: / / www.esa.int/ spaceinvideos/ Videos/ 2017/ 07/ Animation_ visualising_BepiColombo_s_journey_to_Mercury

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ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 18

BepiColombo – MPO and MMO orbits

  • MPO: polar orbit for global

coverage (1500 x 480 km)

  • MMO: highly elliptical for

magnetosphere coverage (11639 x 590 km)

  • The inclination for the MPO &

MMO orbits are the same to restrict the ΔV

  • The initial MMO perigee of

590km was chosen such that the MPO perigee drops to 480 km during the MPO orbit insertion burns.

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ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 19

SOLAR ELECTRIC PROPULSION SYSTEM (SEPS)

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ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 20

Solar Electric Propulsion System (SEPS)

  • 3 xenon tanks – 580kg of xenon
  • High pressure regulator (bang-

bang regulation)

  • x4 T6 ion thruster, each mounted

to independent gimbal mechanism

  • x4 xenon flow control units
  • x2 Power processing units
  • Interconnecting harness and

pipework

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ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 21

`

Anode Solenoid Earth screen Xe flow NEUTRALISER ASSEMBLY Neutraliser Xe flow Cathode Xe flow Main flow CATHODE ASSEMBLY Screen Grid Accel Grid Baffle Discharge Chamber Backplate and Inner pole Cathode Keeper Front Pole Cathode Tip

Insulators Feromagnetic Circuit Stainless Steel Titanium Alloy Magnetic Field Line Molybdenum Carbon Tantalum

Solar Electric Propulsion Thruster (SEPT)

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ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 22

Solar Electric Propulsion Thruster (SEPT)

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ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 23

Solar Electric Propulsion Thruster (SEPT)

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ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 24

Solar Electric Propulsion System (SEPS)

  • The four thrusters are clustered

together, recessed into the MTM structure

  • Each thruster is mounted on a

gimbal mechanism that allows the thrust vector to be adjusted for the different thruster combinations, s/c CoG migration, momentum wheel

  • ff-loading etc.
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ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 25

Solar Electric Propulsion System (SEPS)

Video of thruster pointing mechanisms testing can be found at:

http: / / www.esa.int/ spaceinvideos/ Videos/ 2017/ 07/ Mercury_Transfer_Module_electric_pro pulsion_thruster_steering_test

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ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 26

Solar Electric Propulsion System (SEPS)

  • The four thrusters are clustered

together, recessed into the MTM structure

  • Each thruster is mounted on a

gimbal mechanism that allows the thrust vector to be adjusted for the different thruster combinations, s/c CoG migration, momentum wheel

  • ff-loading etc.
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ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 27

FCU- xenon flow control unit

  • Development and qualification by Moog-

Bradford Engineering

Images courtesy of Bradford Engineering

P P

IV1 IV2 FCV1 FCV2 LPT1 LPT2 FR1 FR2 FR3 F HTR Main Flow Cathode Flow Neutraliser Flow T1 T3 T2

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ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 28

Power Processing Unit (PPU) - architecture

  • The thruster requires 5 supplies:
  • Anode
  • Constant current
  • Solenoid/Cathode Heater
  • Constant current
  • Accel Grid
  • Constant voltage
  • Keeper/Neutraliser Heater
  • Constant current
  • Beam
  • Constant voltage
  • ve

Anode +ve

  • Accel. Grid

Neutraliser Keeper

Power Processor Unit

(excluding FCU drivers) Solenoid +ve

  • ve

Beam Supply Cathode Neutraliser Main Flow Solenoid / Heater Supply Cathode Heater +ve Neutraliser Heater

  • ve

Heater / Keeper Supply

  • ve
  • ve

Splice Plate Thruster

Spacecraft Ground
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ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 29 Images courtesy CRISA

  • Each PPU effectively contains 2 systems
  • Discharge, Accel & Neutraliser Supplies

– DANS – Anode, Cathode Heater/Solenoid, Accel Grid and Neutraliser Heater/Keeper – Anode, Cathode Heater/Solenoid are HV referenced and contained within internal Faraday Housing – PPU contains 2 sets DANS – Each DANS can be switched to 2 thrusters

  • Beam Supply Unit (BSU)

– Parallel Beam Supply Modules (BSMs)

  • FCU Drivers

– Drivers can be switched to 2 FCU

Power Processing Unit (PPU) - architecture

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ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 30 Images courtesy CRISA

  • Modular Beam Supply

– Provides a fault tolerant system

  • SEPS PPU contains 4 BSMs

– SEPS requires 145mN minimum which is guaranteed with 3 BSMs

  • Unit interfaces directly to heat pipes
  • Unit footprint = 800mm x 420mm

DANS x2 BSU

Power Processing Unit (PPU) - architecture

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ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 31

Solar Electric Propulsion System (SEPS)

  • Each T6 thruster and its associated

xenon Flow Control Unit (FCU) can be

  • perated via either of the two cross-

strapped Power Processing Units (PPU)

  • Cross-strapped arrangement allows

simultaneous operation of any two thrusters even in the event of the failure of any one system element

BSM1a BSM1b BSM1c BSM1d PPU#1

TSU#1 TSU#2

BSM2a BSM2b BSM2c BSM2d PPU#2 DANS# 3

TSU#3 TSU#4

DANS# 4 DANS# 2 DANS# 1 SEPT #1 SEPT #2 SEPT #3 SEPT #4

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ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 32

Solar Electric Propulsion System (SEPS)

  • Each T6 thruster and its associated

xenon Flow Control Unit (FCU) can be

  • perated via either of the two cross-

strapped Power Processing Units (PPU)

  • Cross-strapped arrangement allows

simultaneous operation of any two thrusters even in the event of the failure of any one system element

BSM1a BSM1b BSM1c BSM1d PPU#1

TSU#1 TSU#2

BSM2a BSM2b BSM2c BSM2d PPU#2 DANS# 3

TSU#3 TSU#4

DANS# 4 DANS# 2 DANS# 1 SEPT #1 SEPT #2 SEPT #3 SEPT #4

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ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 33

SEPS – coupling tests

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ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 34

SEPS – coupling tests

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ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 35

SEPS – full system coupling at spacecraft level

  • The SEPS was enabled and

each thruster operated in discharge only mode

  • Verified every SEPS electrical

and fluidic interface

  • High voltage testing also

performed by enabling beam and Accel grid supplies

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ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 36

BepiColombo – meets the launcher

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ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 37

BepiColombo – meets the launcher

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ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 38

BepiColombo – mission animation

Animation of mission can be found at:

http: / / www.esa.int/ spaceinvideos/ Videos/ 2018/ 06/ BepiColombo_launch_to_Mercury