Tas Hall Effect Plasma Thruster Module Assembly

TAS HALL EFFECT PLASMA THRUSTER MODULE ASSEMBLY

Alain BLANC(1), Anthony NAULIN(2), Pierre-Marie AGEORGES(3), Fabrice CHAMPANDARD(4), Michel LYSZYK (4) (1)TAS, 100 Bd du Midi, BP 99 - 06156 Cannes la Bocca, E-mail : [email protected] (2)TAS, 100 Bd du Midi, BP 99 - 06156 Cannes la Bocca, E-mail : anthony.naulin@ thalesaleniaspace.com (3)TAS, 100 Bd du Midi, BP 99 - 06156 Cannes la Bocca, E-mail : pierre-marie.ageorges@ thalesaleniaspace.com (4)TAS, 100 Bd du Midi, BP 99 - 06156 Cannes la Bocca

ABSTRACT Hall effect plasma thruster module on generic spacecraft offers unique advantages for most of the An extended generation of Hall effect Plasma usual telecommunication missions as it allows the Thruster Module Assembly (TM) has been designed reduction of Spacecraft launch mass. by THALES ALENIA SPACE in the frame of the Xenon Propulsion System (XPS) . The XPS is used on This paper shows the major interactions between the new generic ALPHABUS platform jointly under mission needs, subsystem equipment , then qualification by THALES ALENIA SPACE and mechanism. ASTRIUM in the frame of a CNES and ESA support 2. HALL EFFECT PLASMA THRUSTER and funding . MODULE TECHNICAL DESCRIPTION The XPS Thruster Module take benefits from : 2.1. THE THRUSTER MODULE ASSEMBLY - Thruster Orientation Mechanism (TOM) from THALES ALENIA SPACE mechanism This paragraph details the composition of the Hall based on a flight proven heritage and effect Plasma Thruster Module : improved by a delta design. One of the main achievement here has been to introduce this improvement while keeping the qualification 2.1.1. Architecture heritage : life time and thermal qualification status. - Use of the PPS1350 Hall effect Thruster from SNECMA to perform satellite in flight corrections (North/South Station Keeping, wheels offloading, etc...) This paper presents : - The Xenon Propulsion System, called Hall effect Plasma Thruster Module (TM) composition. - The development logic followed, including manufacturing and acceptance testing. - This paper shows the major interactions between mission needs, subsystem equipment , then mechanism. The first application to the ALPHASAT satellite is presented It also permits to highlight that the mastery of such equipment is a major need for a Prime.

Figure 1. Thruster Module 1. INTRODUCTION The function of the Xenon Propulsion System is to 2.1.1.1. Procured equipment provide inclination and eccentricity control for North/South station keeping and in addition it allows - 2 PPS 1350 (one nominal, one redundant) unloading of reaction wheels. Furthermore, XPS is also Each thruster are manufactured and used for top-up operation. acceptance tested by SNECMA

______‘14th European Space Mechanisms & Tribology Symposium – ESMATS 2011’

Constance, Germany, 28–30 September 2011 445 - 4 Xenon Flow Controllers (XFC), 2 XFCs are - a mobile plate or radiative plate associated to each thruster. The XFC includes - a gimbal assembly a thermo throttle which allows to control the Xenon mass flow. - a structure made of five feet - 2 Filter Unit (FU) located upstream each - 2 linear actuators plasma thruster in order to limit - 2 switches giving the zero-reference position electromagnetic conduction from the thruster towards the Power Supply (TAS-F ETCA) - a hold-down and release mechanism - 2 Hot Interconnection Box located on the TOM mobile plate (TAS-F ETCA)

Figure 2. FU and HIB

Figure 3. PPS1350 and XFC

2.1.1.2. Equipment designed and manufactured by TAS

- Thruster Orientation Mechanism - A honey comb baseplate, designed to guarantee structural integrity - One set of Xenon feeding pipes and electrical Figure 4. TOM ALPHABUS mechanism harness to thrusters and XFCs, including a Some module equipment are integrated at mechanism flexible part accommodated through TOM level, mainly located at the mobile plate level : gimbals assembly. - Optical Solar Array and active thermal control - One set of thermal control devices (thermistors, heaters, OSR and MLI). - Flexible harnesses to supply thrusters - Individual shim under each thrusters, - Tubing determined for each missions 2.2.2. Major performances datas 2.2. FOCUS ON THE EQUIPED THRUSTER - Angular range : ±12° around each axis ORIENTATION MECHANISM, THE “SKELETON” OF THE HALL EFFET - Resolution step better than 0.005° (0.0027° THRUSTER MODULE on each gimbals’ axis and 0.0019° on combined axis)

2.2.1. Global Architecture - TOM mass : 14.5 kg - In Orbit Lifetime : 15 years The Thruster Orientation Mechanism provided by TAS has a standard architecture of Electric Propulsion Pointing Mechanism (EPPM), composed of the 3. HALL EFFET PLASMA THRUSTER following elements : MODULE DEVELOPMENT LOGIC

446 3.1. DEVELOPMENT LOGIC The Thruster Orientation Mechanism was developed and qualified in the frame of the project STENTOR initiated by CNES 10 years ago to launch a French 3.1.1. Heritage technological satellite. TOM has acquired a successful flight heritage on Eutelsat 10 since June 2004. 8 TOMs The Plasma Propulsion System (PPS) has been are in orbit, 17 TOMs have been delivered. developed and qualified through STENTOR , ASTRA- 1K and GEi programs (AMC satellites). The 3.2.1.2. Delta qualification : origin and driver SPACEBUS 4100 C1 PPS is based on the Plasma Propulsion System from ASTRA-1K and STENTOR Due to performance evolution (the baseline at Thruster but with SPT 100 thrusters and new avionics interfaces Module level is the use of two PPS1350-G) and (100V and “Rubi” TM/TC interfaces ). ALPHABUS mechanical environment (higher than the The SPACEBUS 4100 C1 PPS reference configuration qualification status), a delta design of the TOM has is extended to cope with PPS1350-G thrusters instead been performed. of SPT 100 ones : The main challenging delta design driver was to - PPS 1350-G has completed its qualification strengthen the mechanism structure but to conserve : (environmental tests, life test ) to reach 8500h - thermal qualification status. (with one cathode and 10532 h (It=3,38 MNs) with two cathodes - lifetime qualification status - TOM mechanism adaptation for the PPS 1350-G thruster ( 4.4 kg each instead of 3.5 3.2.2. Test followed kg for SPT 100) Delta qualification test plan includes all the mechanical environment test to demonstrate that the reinforcement 3.1.2. Alphabus baseline performed fulfil the ALPHABUS requirement. ALPHABUS XPS for nominal range is derived from The below flow chart summarises the qualification test existing SPACEBUS version PPS based on the sequence. PPS1350-G thrusters configuration. Dedicated tasks are set up for subsystem design adaptation: TOM DQM model

- implementation to cope with Alphabus Functional tests constraints and requirements

- Alphabus TOM Delta qualification Sine and random vibration test (2 PPS 1350) and pyro release test - Secondary structure optimization

- X axis shift of thrusters on TOM mobile plate Functional tests up to 50 mm (not applicable for ALPHASAT) Launch vehicle shock - Top-up/ On Station mission : Thruster and pyro release test

Module adaptation on thermal aspect (radiator extended on rear part ) Functional tests

Except the above mentioned activities, development TVAC test : thermal set up validation for flight and qualification efforts, all the other equipment model needed for the ALPHABUS have been developed and qualified in the frame of SPACEBUS. Functional tests

3.2. DELTA QUALIFICATION PERFORMED Dismounting and expertise AT EQUIPED MECHANISM LEVEL Figure 5. TOM ALPHABUS DQM Test sequence

3.2.1. Delta qualification logic at mechanism 4. BENEFITS FOR A PRIME TO MASTER THE THRUSTER MODULE 3.2.1.1. Heritage

447 4.1. VERTICAL INTEGRATION : AN IDEAL - TOM performances control tests (Angular OPTIMISATION OF ASSEMBLY AND TEST range, slew rate, resolution, accuracy, reproducibility) All integration and test are performed in house TAS. The main benefit is to fully optimise sequence for 4.2. MECHANICAL SIZING : AN IDEAL assembly and test. OPTIMISATION OF DYNAMIC MECHANICAL BEHAVIOUR 4.1.1. Optimisation of assembly sequence 4.2.1. Global sizing logic Some module part are integrated at mechanism level. This element are mainly located on the mobile plate : One of the challenging mechanical sizing driver is to - Optical Solar Reflector and active thermal take into account the modal signature of : control - the mechanism - Flexible harnesses to supply thrusters - the mechanism support structure - Tubing - the spacecraft The TOM obtained is an “equipped” mechanism. - the plasmic thrusters The objective of mechanical analysis is to avoid any mechanical coupling.

4.2.2. Analyses performed

Figure 6. Picture of mobile plate equipment

4.1.2. An optimized acceptance test sequence Figure 7. Physical and Condensed Models of XPS propulsion module The optimised assembly sequence avoids a phase of dismounting at Hall effect Plasma Thruster Module level. The consequence is that vibration and TVAC test are requested only at mechanism level acceptance. At Thruster Module, the acceptance sequence is therefore limited to assembly verification and functional test within TM configuration : - Visual and dimensional inspection - Electrical controls check of the electrical continuities, resistances and isolations, valve opening - Locking and release tests with alignment controls (without pyrotechnically actuation)

- Internal leakage at MEOP on XFC valves. Figure 8. S/C + Support + XPS module FE model

448 lifetime , firing schedule wrt season over one year. - Mechanism components thermal qualification status Challenge of thermal sizing is to optimize in term of mass, heater lines power consumption and the active and passive thermal control. A global thruster Module thermal model is built including all equipments and adding all thermal control components as : - O.S.R. (Optical semi reflector) and supporting radiators Figure 9. XPS module +Support mode X Hz - M.L.I. (Multi Layer Insulation) and supports - Heaters lines (heaters and thermistors). The mechanical analyses permit to determine the The mechanical structure interfacing thruster module principal modes frequencies of the propulsion module base plate and Spacecraft panels is also modelized. mounted on the satellite, then to compare these frequencies to the spacecraft main frequencies. 4.3.2. Analyses performed The sine response analyses permits to determine the A nodal method is used to build thermal models and amplifications and I/F loads, and to evaluate the impact performed corresponding sizing analysis. and acceptability on input level of thrusters module notching criteria. 4.3.2.1. Thermal model : mechanism The supporting structure is adjustable (compared with spacecraft and mechanisms) at the different stage of the project : the knowledge of its design parameters permits to find the best global mechanical behaviour compromise.

4.2.3. Conclusion

The synergy between mechanical engineers at mechanism and system levels permits to obtain an optimization of the dynamic mechanical behaviour.

4.3. THERMAL SIZING : AN IDEAL OPTIMISATION OF THERMAL BEHAVIOUR

4.3.1. Global sizing logic Figure 10 : thermal model of TOM mechanism : 4.3.2.2. Thermal model : module The aim of the thermal analysis is to demonstrate the adequacy between : - Thruster Module thermal control - System thermal constraints linked to Thuster module location in Spacecraft and corresponding thermal environment (temperatures for external spacecraft surfaces, interfacing structures, reflectors, fluxes form solar arrays, …); System firing strategy : firing duration (several hours) over a day and

449 Figure 13 : typical results of firing thruster and its Thruster Module MLI environment for hottest conditions (solstice, end of life)

Thruster 4.3.3. Conclusion Module OSR The thermal behavior of the thruster module depends on firing sequence (defined at system level in accordance with mission needs). The thermal mapping and thermo-elastic analyses are optimized with a thruster module fully modelised in the satellite global model. 2 PPS 1350 thrusters

4.4. CONCLUSION : COST SAVING Figure 11 : Thruster Module thermal model The major conclusion of this paper is that the ( PPS 1350, OSR & MLI) Assembly, Integration and Test sequences are optimised, and consequently cost and planning are too 4.3.2.3. Thermal model : spacecraft optimised.

5. FLIGHT HERITAGE WITH ALPHASAT The Thruster Orientation Mechanism was developed and qualified in the frame of the project STENTOR initiated by CNES 10 years ago to launch a French technological satellite. TOM has acquired a successful flight heritage on Eutelsat 10 since June 2004. 8 TOMs are in orbit, 17 TOMs have been delivered. The delta designed TOM and the TAS Thruster Module will flight for ALPHASAT (launch foreseen in 2012), the first commercial application of ALPHABUS platform.

Figure 12 : Location of Thruster Module ALPHABUS platform on North panel CONCLUSION This paper shows the major interactions between 4.3.2.4. Thermal results mission needs, Xenon Propulsion System equipment , then mechanism. Thermal analysis allows to demonstrate that active and passive thermal control implemented keep all units It also permits to highlight that the mastery of such within their design temperature ranges over spacecraft equipment is a major need for a Prime. lifetime (transfer orbit, geostationary orbit during 15 years) and justify heater lines design (heater line sizing ; location of thermistors). ACKNOWLEDGEMENT

H4 thruster ON Many thanks to Emilie COULAUD & Yann MICHEL 150 from CNES, and Jean Michel LAUTIER from ESA for 140 130 their high level of implication all along the project 120

110 100 90

60 TEMPERATURE(°C) 50

0 0 10800 21600 32400 43200 54000 64800 75600 TIME (s) n115_ref thrust ON -Z n48_align shim -Z n35_ATC pilot n42_blade++Z n43_blade+Z

450