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 | Slide 2 Launch: 0 2 :4 5 :3 8 BST, 2 0 th Oct 2 0 1 8
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) ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 3
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 ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 4
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) ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 5
MMO Mercury Magnetospheric Orbiter MOSIF MMO Sun-shield and interface MPO Mercury Polar Orbiter MTM ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 6 Mercury Transfer Module
BepiColombo – spacecraft configuration ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 7
BepiColombo – spacecraft configuration ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 8
BepiColombo – spacecraft configuration ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 9
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: MPO Propulsion: Dim ensions: • 4 x 145 mN ion engines, • 8 x 5 N thrusters • Overall height 6.3m • Isp = 4,200s, 290 mN max • 8 x 22 N thrusters • Span: 30.4 m • 16 x 10 N thrusters, 8 x 22 N thrusters Solar Array: MTM: 13,200 W, 2 x 21 m 2 • Solar Array: MPO: 2,000 W, 8.2 m 2 • ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 10
BepiColombo – Thermal solutions (MPO) • 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 or Mercury albedo ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 11
BepiColombo – Thermal solutions (MPO) • 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 ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 12
BepiColombo – Thermal solutions (MPO) ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 13
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 on these panels directly mounted to heat-pipes to spread the heat across the entire panel ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 14
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 on these panels directly mounted to heat-pipes to spread the heat across the entire panel ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 15
BepiColombo – Thermal solutions (MTM) • 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 ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 16
BepiColombo – the journey to Mercury Professor Giuseppe ‘Bepi’ Colom bo ( 1 9 2 0 – 1 9 8 4 ) http: / / www.esa.int/ spaceinvideos/ Videos/ 2017/ 07/ Animation_ University of Padua, I taly visualising_BepiColombo_s_journey_to_Mercury ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 17
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. ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 18
SOLAR ELECTRIC PROPULSION SYSTEM (SEPS) ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 19
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 ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 20
Solar Electric Propulsion Thruster (SEPT) Solenoid ` Front Backplate and Pole Inner pole Xe flow Accel Grid Main flow Baffle Xe flow Cathode Screen Keeper Grid Cathode CATHODE Cathode ASSEMBLY Tip Anode Discharge Chamber Insulators Feromagnetic Circuit Stainless Steel Xe flow Titanium Alloy Neutraliser Molybdenum Carbon Tantalum NEUTRALISER Magnetic Field Line Earth ASSEMBLY screen ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 21
Solar Electric Propulsion Thruster (SEPT) ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 22
Solar Electric Propulsion Thruster (SEPT) ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 23
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 off-loading etc. ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 24
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 ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 25
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 off-loading etc. ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 26
FCU- xenon flow control unit • Development and qualification by Moog- Bradford Engineering F IV1 FCV1 FCV2 IV2 T1 T2 P LPT1 P LPT2 HTR T3 FR1 FR2 FR3 Main Cathode Neutraliser Images courtesy of Bradford Engineering Flow Flow Flow ESA UNCLASSI FI ED - For Official Use Neil Wallace | 17/ 10/ 2018 | Slide 27
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