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TRANSCRIPT
SES Proprietary |SES Proprietary
PRESENTED BYEric Kruch
PRESENTED ON24 October 2017
EPIC Workshop 2017
SES Perspective on Electric
Propulsion
SES Proprietary |
SES Perspective on Electric Propulsion Agenda
2
1 Electric propulsion at SES today
A. SES Fleet Overview
B. Growth of Electric Propulsion in the SES fleet
C. Drivers for Electric Propulsion
2 Trade Off Considerations
A. Performance Trade-Offs
B. System Implications considered by Operators
C. Change in the Launcher Industry Landscape
3 How Electric Propulsion fits within SES Procurement
4 Conclusion
A. Needed electric propulsion improvements
EPIC Workshop 2017 – SES Perspective on Electric Propulsion
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Electric Propulsion at SES today
SES Proprietary | 4EPIC Workshop 2017 – SES Perspective on Electric Propulsion
5 GEO satellites under procurement (4 full electric propulsion)
15 MEO satellites under procurement (8 hydrazine, 7 full electric propulsion)
Electric Propulsion at SES todaySES Fleet Overview
SES Proprietary | 5EPIC Workshop 2017 – SES Perspective on Electric Propulsion
Electric Propulsion at SES todayGrowth of Electric Propulsion at SES
SES has been flying Electric Propulsion for over 20 years
02468
101214161820
2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022
Propulsion types repartition for launched satellites
Electric
Mixed
Hydrazine + Arcjet
Chemical
SES4,5 (SPT100 + Biprop)
SES9 (XIP + Biprop)
SES15 (XIPS) SES17 (SPT140)SES12,14 (SPT140)
SES10 (SPT100 + Biprop)
Electra (PPS5000)
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Electric Propulsion at SES todayDrivers for Electric Propulsion
30 years of commercial satellites evolution from Astra 1A to SES-12
Significant evolution in payload mass and power over this period
Body size: 1.5 x 1.7 x 2.1 mDry mass: 900 Kg
Launch mass: 1800 Kg Solar panel span: 19 mPayload Power: 1.6 kW16 active transponders
Body size: 2.1 x 2.35 x 5.3 mDry mass: 4250 Kg
Launch mass: 5470 Kg Solar panel span: 42 mPayload Power: 15.1 kW76 active transponders
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Cost of launching a satellite has always been a barrier to entry for new satellite businesses and a huge penalty compared to terrestrial solutions
In recent years, the launch industry started to address this issue through more economical but less powerful launchers, e.g. SpaceX Falcon 9, Soyuz from Kourou
Due to the increasing mass of commercial satellites, some could not be launched by these launchers, despite clear economic advantage
This triggered the need to reduce drastically the satellite launch mass
• Liquid propellants typically represent 50 to 60% of a GEO chemical propulsion satellite dry mass
EPIC Workshop 2017 – SES Perspective on Electric Propulsion
Electric Propulsion at SES todayDrivers for Electric Propulsion
SES12, with a dry mass above 4200 Kg, was only made possible through an electric propulsion subsystem
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Trade Off Considerations
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Electric propulsion offers an Operator a higher specific impulse, resulting in a lower launch mass to achieve the same on-station lifetime
• High thrust (typ 1-500N) and low Isp (typ 200-350 sec) for chemical propulsion
• Low thrust (typ < 0.3 N) and high Isp (typ>1500 sec) for electric propulsion
The following table (based on a 2000Kg dry mass) illustrates the huge launch mass gain granted by electric propulsion
EPIC Workshop 2017 – SES Perspective on Electric Propulsion
Trade-off ConsiderationsPerformance Trade-offs – Launch Mass
The mass represented by an electrical solution is increasing the choice among the potential launchers which can considerably improve the launch cost
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BUT at the expense of the satellite time to orbit
Time spent between contract signature and in-orbit delays the revenues and the satellite profitability, it is thus crucial to minimize it
• The following table (based on a 2000Kg dry mass) illustrates the significant duration imposed by electric propulsion
EPIC Workshop 2017 – SES Perspective on Electric Propulsion
Trade-off ConsiderationsPerformance Trade-offs – Time to Orbit
2000
2500
3000
3500
4000
4500
5000
100 150 200 250 300 350 400 450
Mas
s [K
g]
EOR Duration [days]
Falcon9 case - mass vs EOR duration
HET - Dry Mass
HET - Launch Mass
GIT - Dry Mass
GIT - Launch Mass
The higher thrust of a chemical propulsion reduces the time between launch and on-orbit, allowing the customer to have the satellite in operation quicker
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Spacecraft system design
• Need for increased electrical power capability, and for heavy power processing units which are highly dissipative. In combination with higher dissipative payloads, this may trigger the need for more efficient thermal control, lighter solar arrays, more efficient solar cells
• Plume effects, solar arrays interconnector and OSRs erosion leading to performance degradations
• Potential need for auxiliary propulsion system and larger reaction wheels for initial de-tumbling, safe mode, faster anomaly recoveries
Space environment
• Low thrust => long (in the order of 200 days) orbit raising duration => increased time spent inside the Van Allen belt => extensive exposure to radiations leading to higher solar array power degradation and other potential environment effects
EPIC Workshop 2017 – SES Perspective on Electric Propulsion
Trade-off Considerations System implications considered by Operators (examples) (1/2)
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Technological risk, maturity
• New electric thrusters with no or limited on-orbit heritage have an unknown inherent technological risk that can be evaluated only with time
• Most propulsion system components (valves, regulators…) are not tested with Xenon because its expensive. This could lead to potential undisclosed long term issues
Schedule risk, qualification duration
• The timeframe for new technologies to go from concept to validation and qualification can be rather long
• Low thrust of electric propulsion means very long life tests
EPIC Workshop 2017 – SES Perspective on Electric Propulsion
Trade-off Considerations System implications considered by Operators (examples) (2/2)
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Future Launcher capabilities
• More powerful launchers coming (e.g. Falcon heavy, Ariane6) may allow to send much heavier chemical propulsion satellites to geostationary orbit
• On the other hand, the removal of the big constraint represented by launcher capabilities may reduce the impact related to transfer orbit duration
EPIC Workshop 2017 – SES Perspective on Electric Propulsion
Trade-off ConsiderationsChange in the Launcher Industry Landscape
Both chemical and electrical thrusters should thus still play a role in future satellite designs
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How Electric Propulsion fits within SES Procurement
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Commercial geostationary spacecrafts are strongly dependent on financial aspects. Satellite, but also launcher, insurance and operational costs have an important weight
SES is thus looking at the overall S/C in orbit price per sellable unit (where a sellable unit, e.g. classical transponder, MHz or Mbit, is depending on the target market)
EPIC Workshop 2017 – SES Perspective on Electric Propulsion
How Electric Propulsion fits within SES Procurement
In the end, SES does not specify the propulsion technology, but specifies the capability, need date and price target. The satellite vendor presents the most optimal
propulsion subsystem(s) to SES for each specific mission
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Conclusion
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For SES, electric propulsion has allowed embarking more payload and less fuel on recent satellites while staying within launcher capability. This has come at the cost of extended time to orbit, extended time to revenue, and increased time spent in higher radiative environment
Potential avenues of investigation at this workshop
• increasing the thrust per power ratio while keeping sufficient high specific impulse
• combining satellites with faster electric orbit raising capability and light chemical last stage added to launchers
• modular S/C design approach (chemical propulsion module dedicated to orbit raising only)
EPIC Workshop 2017 – SES Perspective on Electric Propulsion
ConclusionElectric Propulsion Improvements
The launch mass benefits of electric propulsion combined with a much reduced time to orbit is highly desirable
SES Proprietary Q2 '16 – Executive Committee – SES PPT Template – KSM – md
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