AIAA 98-3328

THE EXPRESS/T-160E FLIGHT HARDWARE DEVELOPMENT EFFORT

Todd Peterson, NASA Lewis Research Center, Cleveland, OHDoug Alien, Schafer Corp., Dayton, OH

Kent Koester, Space Power Inc., San Jose, CAVladimir Baranov, Keldysh Research Center, Moscow, Russia

Anatoly Romashko, NPO-PM, Krasnoyarsk, Russia

Abstract

In the course of evolving and refining electric propulsion systems for multiple government and commercialapplications, Hall-Effect Thruster (HET) technologies have come to the forefront as an efficient and effective meansof performing numerous propulsion functions. In keeping with the Ballistic Missile Defense Organization (BMDO)HET technology initiatives, Former Soviet Union (FSU) thruster technologies have been developed in partnershipsbetween the U.S. and Russia with the Russian Hall Effect Thruster Technology (RHETT) program. The BMDO-sponsored progression of HET technology development is continuing with the higher power, more efficientEXPRESS/T-160E flight hardware development project. In-space stationkeeping capabilities of a 4.5 kWe Hall-Effect Thruster (HET) on a Russian EXPRESS-A communications satellite will be demonstrated by the T-160Ethruster subsystem in late CY 1999. Overall subsystem and individual component overviews for the upcomingspaceflight test of the Russian HET and US Power Processor Unit (PPU) are described along with currentdevelopment status. The project is pressing towards a system-level Preliminary Design Review (PDR) in early Julywith all project partners, customers and interested government agencies.

Introduction

The EXPRESS/T-160E project was initiated in Marchof 1997 to develop and demonstrate a scaled-up,enhanced version of existing Hall-Effect Thruster(HET) system technology in a North-SouthStationkeeping (NSSK) role on a Russian EXPRESScommunications satellite.1 The Ballistic MissileDefense Organization (BMDO) -sponsored 4.5 kWeHET technology development project will generate thefirst xenon-fed electric propulsion device to be operatedin space at a 5 kWe input power level. This T-160Ethruster system will be demonstrated on EXPRESS-3A(Figure 1), the third of the new generation EXPRESScommunications satellites designed and built by NPO-PM in Krasnoyarsk, Russia.

The T-160E thruster, Flow Control Unit (FCU) andXenon Filter/Getter (XeFG) are being developed byKeldysh Research Center (KeRC) in Moscow, Russia.This thruster design incorporates multiple HET designimprovements to increase both performance and thrust

Copyright © 1998 by the American Institute of Aeronautics andAstronautics, Inc. No copyright is asserted in the United Statesunder Title 17, U.S. Code. The U.S. Government has a royalty-freelicense to exercise all rights under the copyright claimed herein forGovernment Purposes. All other rights are reserved by thecopyright owner.

Figure 1. NPO-PM EXPRESS Satellite

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efficiency. Xenon provided by the EXPRESS spacecraftis routed through the FCU to the T-160E anode ring andactive cathode in a precisely controlled manner. Xenonflowing to the two thruster cathodes is cleansed by theXeFG before exiting the FCU.

Space Power Incorporated (SPI), as the project primarycontractor, is responsible for design and fabrication ofthe Power Processing Unit (PPU) and for T-160Ethruster system integration. Mass and cost reduction arekey goals in the advanced power processingdevelopment of the EXPRESS/T-160E PPU. This isbeing achieved through a modular power supplyapproach using Commercial-Off-The-Shelf (COTS)converter modules. These modules have high powerdensity and low specific mass characteristics, allowinglight-weight, compact packaging of the PPU. Byutilizing the modular approach, the PPU technologyalso breaks away from the past "one-of-a-kind" PPUdesigns by allowing customization (i.e., power levels,voltages, currents) while retaining the same overalldesign and design features. Significantly reducedthermal management and ElectroMagnetic Interference(EMI) filtering requirements also result from thisinnovative, modular PPU design approach. PPUreliability is enhanced by using converter modules in aseries-parallel array configuration. Flight packaging andqualification and acceptance testing of the PPU will beperformed by TRW, Redondo Beach, CA.

In addition to providing the overall T-160E systemphysical integration and testing with the EXPRESS-3Asatellite, NPO-PM is also responsible for the xenonpropellant, main xenon control valve, "diode block", themounting structure for the thruster and FCU/XeFG,EXPRESS launch and operations and T-160Esubsystem command and data collection. A simplifiedschematic of the overall T-160E subsystem layout onthe EXPRESS-3A satellite is shown (Figure 2).

ElectricPropulsionComponentsMountingArrangementon Satellite

FCUs (2)andSPT-100s(2)

T-160EFCU and XFG

PPUXenon Tanks(80 Atmospheres)

Antennaeand Sensors

raan

Figure 2. T-160E Subsystem on EXPRESS-3 A

NASA Lewis Research Center (LeRC) has overallproject management responsibility for theEXPRESS/T-160E project under the direction of theoverall project customer, the Ballistic Missile DefenseOrganization (BMDO). NASA LeRC also providesproject system-level testing (breadboard, qualificationand acceptance) of the T-160E subsystem, as well asleading overall Integration & Test (I&T) and systemsintegration activities in conjunction with SPI. SchaferCorporation acts as the BMDO programmaticrepresentative within the project, and also providessystem integration and coordination expertise. Theoverall EXPRESS/T-160E project organization isshown below (Figure 3).

Program On

SystemEngineering and

CoordinationSenate Corp; :•

: Arlington, Yfc:;>

jjanization

ProgramDirection

BMDO/TOI/SR

....... ... ... i ......__........_.. ._.__._... _Thruster System

TestingNASAlaRC

Cleveland, e»f

CoDRPDRandCOBPanete

iProject Manager

NASA LeRCCfevrtamijOH

; Todd Petersow" .

Prime ContractorSpace Power, Inc.

San Jose, CAOr. J. Kent Koester

..-..--- i - - - - - -— —Spaceflight

Qualification andEngineering

TRWRedondo Beach, CA

ContrastingNASA LeRC

etewbnffcOH

iThruster

Fabrication andQualification

KeRCMoscow, Russia

VehicleIntegration and

OperationsNPO-PM

Krasnoyarsk, Russia

Figure 3. EXPRESS/T-160E Project Organization

Project status will be reviewed and critiqued in an earlyJuly 1998 system-level Preliminary Design Review(PDR). All components have undergone breadboardand/or prototype testing, with resulting minormodifications to hardware, logic control and operationalprocedures. System-level breadboard testing of the T-160E subsystem is underway at NASA LeRC, withcompletion scheduled for September 1998. EngineeringModel (EM) designs are either nearing completion(thruster, FCU) or are in midstream (PPU). PreliminaryEXPRESS satellite integrated vibration testing with T-160E, FCU and PPU mass models will be performed byNPO-PM on EXPRESS-1A this summer. System-

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level breadboards and simulators will be shipped toNPO-PM for functional checkout with an EXPRESSfunctional simulator later this year.

The flight version of the T-160E thruster system willcurrently be delivered to NPO-PM in the second half of1999. No official launch date for EXPRESS-3A existsat this time, although November 1999 is the projectedgoal for EXPRESS-3A launch. Operation of the T-160E system in space is targeted for launch plus 3weeks, and the project goal for T-160E operation is 1year. The system will be fired 30 minutes per day forNSSK for two 120 day periods per year. Operationaldata from the T-160E system and selected EXPRESSdata will be provided by NPO-PM to the project teamfor analysis and comparisons with ground-based testing.The project team will also be directly involved in T-160E operations through a ground station at NPO-PMin Krasnoyarsk, Russia.

Project Objectives

In continuation of the technological "push" RussianHall-Effect Thruster (RHET) program sponsored byBMDO, the primary EXPRESS/T-160E projectobjective is to assure potential customers that this HETproduct is space qualified and is compatible with theoverall host spacecraft. Overall Project goals can besummarized as follows:

• Conduct a successful in-space test of the Russian4.5 kWe T-160E thruster, Russian Flow ControlUnit and U.S. Power Processing Unit on a RussianCommunications Satellite (EXPRESS)

• Develop and demonstrate several new breakthroughtechnologies (higher thruster efficiency, power leveland performance; modular, reconfigurable PPUdesign; decreased PPU mass and cost)

• Demonstrate negligible spacecraft impacts duringT-160E system operations (communications,attitude control, thermal management, satellitesurface degradation)

• Operate the T-160E thruster subsystem for aminimum of 100 hours to validate the system andallow data comparisons with ground test results

• Develop and validate a domestic/internationalproject model for developing, fabricating, testingand integrating T-160E systems

In addition to overall project and program objectives andgoals, the project has also developed qualitative successcriteria. In order to gauge and validate the EXPRESS/T-

160E international team/project model and the successof developing spacecraft-compatible, leading-edge HETsystem technologies, the following criteria will be usedto judge the overall project:

• Pre-Flight:• Verify T-160E system minimum performance

parameters through test• Meet or exceed EXPRESS satellite integration

requirements• Deliver a system that meets or exceeds

operational requirements

• In-Flight:• Acquire T-160E system and EXPRESS

navigational performance data for comparisonwith ground test results

• Demonstrate satisfactory mutual operationswith EXPRESS systems and subsystems

• Meet or exceed performance requirements forEXPRESS NSSK

• Post-Flight:• Publication of EXPRESS/T-160E flight

operations performance and project summary• Assure that developed technologies are

transitioned to Government & Industry users

In summary, it is the intent of this team that the projectstructure of the EXPRESS/T-160E project will providea successful format for similar, international efforts inaddition to validating the 4.5 kWe HET system forfuture implementations.

Subsystem Description

A block diagram of the EXPRESS/T-160E systemoverview is shown (Figure 5).

Figure 5. EXPRESS/T-160E System Diagram

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The overall system mass allowance is 55 kg, with 25kg allotted to the PPU and 8 kg to the T-160E thruster.Xenon provided by the EXPRESS satellite will beprovided to the HET anode at a nominal flow rate of15.4 mg/s. Flow rate to the selected primary cathode atthruster startup will be on the order of 0.71 mg/s.Cathode xenon flow, controlled by the PPU, ischanneled through redundant FCU flow paths withredundant throttles, shutoff valves, a temperatureregulated throttle heater and the XeFG. A thermothrottlecontrolled by the PPU regulates xenon flow to the T-160E anode to maintain constant discharge current.

A maximum of 5 kWe of power is provided to the T-160E system PPU by three EXPRESS battery cellsrated at 70 amp-hrs. Unregulated voltage input to thethruster system is specified at 35+6 VDC. The thrusterwill only be operated for 30 minutes in solar insolationperiods to allow EXPRESS battery bank chargingduring the discharge required by the T-160E thrustersystem. The T-160E thruster will be operated at 300 Vdischarge voltage at the anode, with a nominal 4.5 - 4.6kWe input from the PPU. The "diode block" providedby NPO-PM furnishes isolation between the T-160Esystem and the battery bank. Ground commandstransmitted to the EXPRESS satellite will enableautonomous thruster control within a set of 6command signals to the PPU. Five analog and eight bi-level telemetry signals will be routed to the EXPRESStelemetry block for transmission to the Krasnoyarskground station.

Minimal thermal interaction with the pressurizedEXPRESS satellite body is permitted. Conduction andradiation paths are therefore minimized from both thePPU and the T-160E/FCU/XeFG assembly. Multi-layer insulation and low-conductivity materials will beapplied to allow less than 100 W of transmittance fromthe PPU and less than 50 W from the tnruster/flowcontrol assembly.

A central mounting ring on the EXPRESS-A satellitehouses all stationkeeping components, including nickel-hydrogen batteries, xenon fuel tanks, xenon distributionsystems, the eight primary SPT-100 (Stationary PlasmaThrusters, by Fakel, Russia) and the T-160Edemonstration subsystem. All of these componentswith the exception of the SPT-100 thrusters and T-160Ecomponents are mounted internal to the satellitepressurized shell. During nominal operation, one SPT-100 is fired as required from the north, south, east andwest faces of the EXPRESS-A satellite. The T-160E

subsystem is mounted adjacent to the south set of SPT-100 thrusters (set of two).

Due to this offset and the desire to aim the higher powerT-160E plume away from EXPRESS external payloadsand solar arrays, the T-160E thrust axis is offset fromthe true-north axis of the satellite by 27 degrees.Inefficiencies in the thrust component result, butsufficient spacecraft geometrical and orbital data willexist to validate the performance of the T-160E flightdemonstration subsystem. One T-160E mounting platehouses the thruster, the FCU/XeFG and the main xenonsupply valve. The T-160E subsystem PPU is housed onits own dedicated mounting plate.

Current Development Status

T-160E Thruster

KeRC has developed a pre-prototype T-160 thruster andtwo prototype T-160E thrusters. The pre-prototype,designed and fabricated in 1996, was used for projectfeasibility studies in late 1996 and early 1997. This T-160 uses cold-start cathodes, and is overdesigned toallow simple change-out of components. It is currentlyused at NASA LeRC as a thruster load simulator fortesting PPU breadboard-level subsystems.

The developed prototype T-160E functionally representsthe current design for the flight demonstration. A photoof the prototype T-160E thruster at LeRC is shown(Figure 5).

Figure 5. Prototype T-160E Thruster

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Tests of the prototype T-160E units at KeRC andNASA Lewis Research Center have demonstrated thrustlevels of up to 294 mN with a specific impulse of 1850seconds and thrust efficiency of 56% at the nominalthruster anode input power of 4.5 kWe and anode xenonflow of 15.46 mg/s. A comparison of these data withEXPRESS/T-160E functional requirements are shownto be met or exceeded (Table 1).

PARAMETERThrustU,• di^'harpc

'disrharpt-

TlThrml

Anode Xe FlowRateCathode Xe FlowRateMass

REQUIREMENT260 mN> 1700 s300±5V

ISA55%

15.5 mg/s

0.8 - 1 .2 mg/s

8 kg

EXPERIMENT293.5 mN

1850 s3 00+ 5V

15. 1A56%

15.46 mg/s

0.6 - 0.71 mg/s

9 kg (prototype)< 8 (eng. model)

Table 1. Prototype T-160E Data

Plume profiles and starting transients were also mappedduring LeRC tests and resulting data was provided toNPO-PM in Krasnoyarsk, Russia, the EXPRESSsatellite manufacturer. Thruster random vibration andshock testing at KeRC has resulted in engineeringmodel design updates to anode mounting and wiring aswell as cathode structural improvements. Magneticsystem optimization and cable and supply tubingattachment improvements are also being incorporated inthe design update. These design updates are beingincorporated into the Engineering Model (EM) T-160Eby KeRC.

Preliminary system-level T-160E tests performed atLeRC resulted in the catastrophic failure of theprototype T-160E thruster. Numerous system issuessurfaced during the testing (cathode heater issues, FCUcathode supply valve, auxiliary power supply), and mayhave contributed to the thruster failure. The anodeceramic acceleration channel shifted and tilted outwards,causing a 300V-to-ground electrical short. All hardwarehas been shipped back to the supplier (KeRC - T-160E,FCU/XeFG; SPI - PPU breadboard) for investigation.No conclusive project assessments have yet occurred,but design improvements already in progress address allobvious design concerns stemming from thesepreliminary tests.

The EM T-160E design is currently 70% complete,with the first EM unit expected by September 1998.KeRC will perform mechanical and preliminaryperformance tests before shipment to LeRC for EM T-160E component thermal vacuum performance tests.This EM thruster will then be integrated into theprojects' long-duration (500 hour) qualification tests latethis year. Flight Model (FM) T-160E design will be onhold until preliminary data from the 500 hour test areavailable and analyzed.

Flow Control Unit and Filter/Getter

The prototype FCU/XeFG has been tested at KeRC forperformance, random vibration and mechanical shock.The prototype unit failed during mechanical shocktesting. The subsequent EM unit design is beingmechanically strengthened to ensure survivability perproject requirements and to provide a 5-year design life.In addition, thermothrottle, XeFG heater and diode blockenhancements are being incorporated as the result ofthese preliminary performance tests (Table 2).

PARAMETERFilter/Getter Pwr

Control PowerInlet PressureAnode Xe FlowRateCathode Xe FlowRateMass

REQUIREMENT30±3w

< 8 w2.5+0.1 atm

15.5 ±0.3 mg/s

0.8 ±1.2 mg/s

<0.785 kg

EXPERIMENT28 activation21 operation

< 8 w2.5±0.1 atm

15.5 ±0.3 mg/s

0.7 ±0.15 mg/s

0.78 kg(prototype)

Table 1. Prototype FCU/XeFG Data

A second FCU/XeFG prototype was also tested atLeRC as a part of a preliminary system-level breadboardtest. A cathode flow valve malfunction allowed flow toboth cathodes, resulting in difficult thruster starts. TheFCU/XeFG has been shipped back to KeRC and iscurrently in Moscow customs. KeRC will report theirfindings once the hardware is received and inspected.They will also ensure that the EM FCU/XeFG designprecludes these malfunctions.

Power Processing Unit

An early layout of the PPU design concept is shown(Figure 6). The packaging concept has recently beenaltered and was unavailable in graphics form.

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Connectors

RL2-7

Figure 6. Early PPU Packaging Concept

Power Processing Unit design and development testefforts are proceeding towards the fmalization ofbreadboard and flight designs. The PPU can be brokendown into four subsystems; Modular Discharge PowerSupply (MDPS), Auxiliary Power Supply (APS),Logic Control (LC) and EMI Filtering. Two MDPSconcepts using modified, off-the-shelf parts have beendemonstrated by successfully driving the T-160 at fullpower in vacuum tank tests. The APS breadboard unithas also functionally provided housekeeping power tothe FCU and T-160E cathodes during T-160E breadboardtests at LeRC. Logic control breadboards are currentlybeing fabricated, but the control logic has beenfunctionally demonstrated by a computer simulatorduring the same T-160E systems tests at LeRC. EMIfiltering design (input, output) is nearing completion.

The PPU manufacturing and qualification plans havebeen developed, and all PPU radiation issues have beenresolved. TRW has begun the PPU packaging task andis planning the PPU environmental test series(qualification and acceptance). The PPU will have anintegral heat sink concept using a wax substance firstused for the Apollo Program Lunar Rover heat rejectionsystem.

Once fabrication and preliminary functional tests arecomplete, the full PPU breadboard will be tested atNASA LeRC in combination with the prototype and/orEM T-160E and FCU/XeFG. Performance at fullpower, EMI (conducted, radiated) and controlfunctionality will be tested. The EM PPU design iscurrently 60% complete.

T-160E Subsystem andEXPRESS-A Integration

Preliminary T-160E system integration tests have beenperformed at NASA LeRC in Vacuum Tank 12. Thetest hardware included the T-160E and FCU/XeFGprototype, lab power supplies, PPU APS breadboard

and a computer control program reflecting PPU LogicControl algorithms. Many issues arrised during thisfirst-ever attempt to integrate and operate the T-160Esystem. Component issues have already beensummarized. Needed modifications to these componentsare underway, with resulting engineering model tests tobegin late this Fall at LeRC. Numerous designimprovements, operational procedure improvements andhands-on knowledge of the full T-160E system resultedfrom these preliminary tests.

All EXPRESS/T-160E electrical, mechanical andthermal interfaces have been defined and specified inproject documentation. PPU packaging envelop andconnector issues have been recently surfaced andresolved. The T-160E thruster startup sequence has beendefined and coordinated with NPO-PM.

Mass simulators of all components have been furnishedto NPO-PM (Krasnoyarsk, Russia) for preliminaryvibration tests on the first of the new EXPRESSsatellites. These tests are expected to occur late thissummer. In order to maximize project hardware use, itis envisioned that all system level T-160E hardware willbe shipped to NPO-PM for early integration tests withone of the EXPRESS-A satellites once the componentsand complete system has been fully tested within theproject. Early BB and EM system hardware will be usedfor functional and fit-check testing on their satellite.Once the full flight T-160E system has been acceptancetested at LeRC, it will be shipped to NPO-PM. Thefull EM T-160E system will have already undergoneform, fit and functional checkout on EXPRESS-3A.The EM set will then be replaced with the Flight T-160E system for final continuity tests prior to launch.

Concluding Remarks

The EXPRESS/T-160E project, the first-ever 5 kWeinput xenon-fed HET flight demonstration system, iswell under way. Flight qualification of this RussianThruster with the U.S. built PPU is moving forwardwith well-defined goals and success criteria. Sufficientschedule margin exists to allow the current path of fullqualification and acceptance testing of both the T-160Esystem at NASA LeRC and the EXPRESS/T-160Esystem integration and test programs. Much valuableinsight has been gained from preliminary component-and system-level testing at SPI, KeRC and LeRC.Design improvements in both the hardware and in thesystem operational processes have lowered the projectsuccess risk immeasurably. The bulk of the effort isstill in front of the project team, with the build-up and

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testing of engineering model hardware at a componentand at a system level. The project team itself, includingNPO-PM, KeRC, SPI, TRW and NASA LeRC, isgaining valuable experience and insight with both the4.5 kWe T-160E system and with the cohesivenessrequired of an international team. Efficiencies are beingidentified to assure maximum use of both hardware andproject team time.

Acknowledgments

The authors wish to express their gratitude for theencouragement and resources provided by the projectcustomer (Innovative Science and Technology Office ofBMDO). They also wish to recognize the continuous,key contributions of those team members whose namesare not listed in black & white here.

References

1. J. K. Koester and C. E. Lazarovici, J. M.Sankovic, G. A. Herbert, V. A. Petrosov and V. I.Baranov, A. Romashko and V. Petrusevich, "TheEXPRESS/T-160E Spaceflight Test Program,"IEPC 97-183, 25th International Electric PropulsionConference, Cleveland, OH, August 1997

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