IEPC-93-251 2284

OPERATION OF A BRASSBOARD PCU WITH A LOW POWER ARCJET

R. Di Stefano' and W. D. Deininger."BPD Difesa e Spazio. Colleferro, ITALY

G. Parisi* and E. Detoma*FIAT CIEI - SEPA. Torino. ITALY

ABSTRACT

Characterization testing of a brassboard PCU was conducted using a 1 kW arcjetto examine PCU/engine behavior and validate the overall PCU architecture. The PCUwas characterized by a switching frequency of 33 kHz and can operate in either constantpower or constant current mode. The MOD-B arcjet was used for the tests and had aconstrictor with a diameter of 1.02 mm and a length of 0.59 mm while the electrode gapwas set at 0.4 mm. A gas mixture used to simulate hydrazine was fed to the engine atmass flow rates of 50 and 60 mg/s while the thruster was supplied by the PCU withcurrents between 8 and 14 A. The PCU was able to start and run the arcjet in all casesand showed the generally expected behavior.

NOMENCLATURE INTRODUCTION

BOL Beginning-of-Life Several electric propulsion subsystemBPD BPD Difesa e Spazio (Company) technologies are presently under development inDAS Data Acquisition System Europe for orbit maintenance of geostationaryDC Direct Current satellites; arcjets, ion engines and SPT thrusters.'IPA Isopropyl Alcohol Low power arcjets (1 kW-class) can offer substantialLVDT Linear Voltage Displacement propellant mass savings with respect to currently

Transducer used chemical propulsion systems due to their higherMOD-B Low Power Arcjet Used For specific impulse. Arcjet systems also have a lower

Testing Described in This Paper dry mass and are less complex than ion engine andMOS Metal Oxide Semiconductor SPT systems while, based on specific impulsePCU Power Conditioning Unit considerations alone, ion engine and SPT systemsPFS Propellant Feed System typically provide a larger propellant mass reduction.PWM Pulsed-Width Modulated Arcjet thrusters also minimize spacecraft integrationSEPA FIAT CIEI Divisione SEPA difficulties with monopropellant or bipropellantSPT Stationary Plasma Thruster chemical systems which include hydrazine while ionSSPA Studio di Sistema Propulsione ad engine and SPT systems require a separate propellant

Arcogetto feed system. Arcjets also have a much smaller beamSI Start-Up Unit Capacitor Charging divergence angle than either ion or SPT engines

Switch easing satellite integration geometric constraints. InS2 Start-Up Unit Start Switch addition, SPT thrusters suffer from significantlyS3 Start-Up Unit Diode/Inductor By higher material erosion rates than arcjets (or ion

Pass Switch engines). In fact, insulator material is eroded fromTZM Molybdenum Alloy SPT engines which, if deposited on theVP-2 Vacuum Facility No. 2 at BPD communication satellites antennas, could2%ThW 2% Thoriated Tungsten Metal significantly inhibit communication systems

effectiveness. Therefore, electric propulsion systemsbased on arcjet thrusters are of particular interest andare presently being developed world-wide with* Member Technical Staff, Electric Propulsion laboratory and advanced development work on arcjet

Laboratory. Space Division. laboratory and adanced development ork on arcetConsultant. Manager Electric Propulsion Laboratory. technology is ongoing in Italy, '9 Germany .'-Space Division. Senior Member AIAA. Japan, 4"' and the USA 29" with system qualification

+ Member of the Technical Staff. complete in the USA.3"'O

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In a flight configuration, each arcjet satellite MOD-B ENGINE DESCRIPTIONpropulsion subsystem will include an arcjetassembly, power conditioning unit and PCU/Low power arcjet characterizationinterconnecting power cable. The PCU is required testing was conducted using the MOD-B engineto start-up and operate the arcjet once a flow of which is shown in Fig. 1.2" 6 This engine waspropellant has been established. The PCU will designed for low cost flexibility in engine geometrygenerally require feedback control since the arc changes while trying to better mimic the thermalexhibits a non-linear, negative resistance load. characteristics of flight-oriented engines than otherTherefore the PCU is generally composed of a high laboratory model arcjets. The MOD-B configurationvoltage start-up unit, a power converter, input and used for these tests included a 2% thoriated tungstenoutput filters, a feedback control system and internal (2%ThW) nozzle insert with a 1.02 mm-diameterdiagnostics. Much development work has occurred and 0.59 mm-long constrictor. The conical nozzleon arcjet PCUs and is based on PWM. DC-DC had a 200 half-angle and an area ratio of 100. Theconverter topologies with switching frequencies in propellant was tangentially injected into the plenumthe range of 15 - 20 kHz.2' 3' -' 7-9. 3 .3s 5. 9. -41 3 Recent chamber through four. 0.5 mm diameter injectorswork has shown that higher switching frequencies do with a semicircular cross-section. The injectorsnot impact engine operation and therefore hold were milled into a molybdenum insert. The cathodepromise to reduce the mass of the PCU." was a 3 mm-diameter. 2%ThW rod with a 15 mm-

long, 2 mm-diameter front section. The cathodeThis paper describes initial low power ended with a conical tip which had an included angle

arcjet/PCU characterization test activities conducted of 600 and a tip radius of 0.3 mm. The cathode wasas part of an ASI-funded systems study activity inserted through the rear of the engine and held bybeing conducted by BPD Difesa e Spazio (BPD) in a Swagelok connector. The electrode gap was set atsupport of low power arcjet system implementation 0.4 mm. To eliminate potential problems from thein Europe. The overall systems study covers the unequal thermal expansion of different materialsdefinition of a Reference Mission: 4 detailed arcjet within the engine, a stainless steel spacer ring waspropulsion subsystem specifications and requirements placed within the rear assembly nut to maintain thedefinition 6' 7 based on the Reference Mission sealing pressure at the graphite gasket. Theconstraints; and layout of the overall propulsion compression spring compensated for the differentsubsystem including design of its primary thermal expansions between the boron nitridecomponents 8 along with identification of critical insulator and the TZM outer engine body andareas and delineation of a development plan to insured continuous contact between the insulator, gasachieve subsystem ground qualification by the mid- injection insert and anode piece. Hydrazine wasnineties. The arcjet PCU development activity' 3. 4 1" injected near the rear of the engine to provide somehas been carried out as part of this system study regenerative cooling of the engine and pre-heating ofcontract by FIAT CIEI - Divisione SEPA (SEPA) in the propellant.support of BPD and has also included thedevelopment of an arcjet electrical simulator" and BRASSBOARD PCU ARCHITECTUREdefinition of diagnostics package options.'"9

Ansaldo Ricerche has supported SEPA by The Power Conditioning Unit is a specialdeveloping the PCU inverter unit. These activities power supply designed to convert the satellite buswere conducted to provide an appropriate power (solar arrays or batteries) to a usable form tobackground for definition of a flight-type PCU. The start the arc and to precisely control the electricalMOD-B low power arcjet was used for these tests. current or power supplied to the arcjet. TheFollowing a description of the apparatus and characteristic parameters are inferred from thefacilities, the test procedures are reviewed. Then the preliminary specifications of the arcjet and areresults of MOD-B arcjet/brassboard PCU summarized in Table 1 while a block diagram of thecharacterization testing are discussed. The PCU unit is shown in Fig. 2.'""5 During testing, a Farnellstart-up transient and initial steady-state performance DC power supply Model H 60/50 was used to supplyare presented along with the PCU response to power to the PCU simulating the satellite bus.changes in the load and commanded output current.

The PCU is shown schematically in Fig. 313APPARATUS AND FACILITIES and is composed of two main functional units: the

Control Unit and Inverter Unit. The Control UnitThe MOD-B arcjet design. brassboard PCU controls PCU operation to force the Inverter Unit to

architecture and test facilities are reviewed below, deliver a constant current or a constant power to the

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arc. Additional functions within the Control Unit for of 2 x 103 mbar. Bellows were used to damp

provide monitoring of the basic operational vibrations through the connecting pipes. A

parameters (Signal Conditioning and Monitoring capacitance manometer with an accuracy of ±0.15%

Block), safety override (Safety Block), start-up of the reading was used to measure the vacuum

sequencing (Start-Up Block) and general supervision chamber pressure.

of the PCU operation (Supervisory Block). The

controller unit provides both constant current control Prior to arcjet operation using the

and constant power control. brassboard PCU. the engine behavior wascharacterized using a laboratory power supply

The Inverter Unit is a PWM step-up power system. The laboratory power supply system. Fig. 4.

supply delivering constant current or constant power was composed of a main power supply and a start

to the arcjet and also provides the start-up pulse to up circuit connected in parallel. The start-up system

the arcjet. The inverter unit includes the PWM was composed of a high voltage/low current power

modulator, driver and MOS bridge, main supply unit, a 5 pF capacitor bank, a diode block

transformer, rectifier, output filter/start-up circuitry and a 1.4 pH inductor. The matching of the

and the DC/DC converter. The PWM block supplies electrical characteristic of the main power supply

the driving pulses to the MOS-bridge switches via and the engine was accomplished by a 0 to 11 ohm

the driver circuitry. The pulse width is proportional ballast resistor in series with the thruster. The

to the voltage of the control signal Al. The variable ballast resistor was also used to reduce the

switching frequency is 33 kHz. The main current spike during the capacitor bank discharge

transformer is used as a step-up element to provide and to compensate for the main power supply

the relatively high-voltage required to sustain the arc ramp-up time. The inductor was connected to

discharge. In addition, it provides electrical isolation increase the capacitor bank discharge time and to cut

between the power bus and the arc electrodes. current oscillations during the ignition transient. A

Given the high switching frequency of the PWM by-pass switch was also installed to avoid diode and

controller, a ferrite core has been selected for the inductor overheating. Referring to Fig. 4. the

main transformer. The rectifier block rectifies the capacitor bank was charged by closing switch Sl

AC output current from the main transformer using while switches S2 and S3 were open. Then, the arc

a high-speed silicon half-bridge or full-bridge was ignited by opening switch S1 and closing switch

rectifier configuration depending on whether the S2. As soon as the arc was stable, switch S3 was

main transformer has a center-tapped or normal closed to by-pass the diodes and inductor. The start

secondary. The first solution is the most appealing up and run voltages were measured by voltage

because the power losses of the rectifiers are half of probes with attenuation factors of 1000 and 100.

the other configuration but it requires a larger respectively. The probes had an accuracy of ±3%.

volume. The output filter and start-up circuitry A calibrated shunt, in series with the anode current

block implements the output filter using only an feedline, was used to measured the arcjet current.

inductor. The same inductor is used to provide the The current was measured with an accuracy of

high voltage pulses to initiate the electrical discharge ±0.5%.

between the electrodes. The DC/DC converter is a

resonant power supply and derives its power from The propellant feed system (PFS) provided

the power bus (in this case the Farnell power a controlled flow of a gas mixture simulating

supply). It provides three isolated outputs which are hydrazine (N, + 2H,) to the arcjet. The nitrogen

used to supply the MOS-drivers. the stan-up and hydrogen mass flow rates were controlled by

circuitry and the logic circuitry, dedicated thermal-type mass flow controllers with alisted accuracy of ±1% and then injected into a

FACILITIES AND INSTRUMENTATION mixing manifold. Downstream of the mixingmanifold, the total mass flow rate of the gas mixture

The MOD-B arcjet/PCU tests were was measured by a Coriolis force-type mass flow

performed in Facility VP-2 of BPD's Electric meter with an accuracy of ± 2%. Pressure

Propulsion Laboratory. This facility is described in transducers were placed at the mixing manifold and

detail elsewhere: '"' and summarized below. The vacuum chamber door. The latter served as the

facility is based on a 1.6 m-long. 0.8 m-diameter feedline pressure measurement transducer. The

steel vacuum chamber connected to a vacuum plant pressure transducers had listed accuracies of ±0.5%

composed of a four-stage. Roots blower-based and ±0.3%, respectively. Two bottles for each gas

pumping group. The vacuum system provided a were available in the storage area of the PFS. The

pumping speed of 19.000 m'/hr at an inlet pressure bottles were connected in parallel to allow empty

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22B7 IEPC-93-251

bottle removal and replacement without interruption The engine piece parts were then assembled. Priorof a test cycle. to positioning the cathode in the engine body. a

preliminary leak check was conducted to verifyThe thrust balance was a parallelogram, proper engine assembly. The electrode gap was set

swing arm-type device. The thrust balance is by inserting the cathode rod into the engine until theillustrated in Fig. 5 with the MOD-B arcjet mounted cathode tip touched the converging cone of thealong the support beam by means of a thermally anode, then pulling back the cathode by the desiredisolated clamp interface. The thrust was calculated gap setting. The gap was measured by means of aby measuring the support beam displacement using micrometer with a resolution of 5 x 103 mm. Aa linear variable displacement transducer (LVDT). leak check of the assembled engine was made byThe thrust balance calibration was performed by pressurizing the engine to 4 bar with compressed air.correlating the LVDT output to the displacements Leaks were detected using a liquid leak detector.caused by sequential application of four known The resistance between the cathode and anode wasweights. The weights simulated a thrust range of checked for infinite impedance. The engine was0.068 to 0.282 N. The sensitivity of the thrust then attached to the thrust stand interface.balance was 0.14 N/V. The least squares linear fitsindicated that the standard error of the measurement PCU Installation A schematic of the connectionswas about ±2 mN corresponding to approximately between the PCU. DC power supply and the data1% of the reading. The thrust measurement was acquisition system (DAS) is shown in Fig 6. Thisaffected by a thermal drift of the zero point. Tests architecture enabled all of the measurementsindicated that thermal drift was mainly caused by the (current, voltage, specific impulse, efficiency, gasthermal elongation of the thruster support beam. A mixture flow rate...) to be monitored and controlledcomparison of the calibration curves before and after using a personnel computer-based DAS. Thea test indicated that the thermal drift affected the transients of the voltage and current were recordedcalibration zero offset only."- 6 Therefore. the thrust with a digital oscilloscope.measurements were performed by turning off theengine after each cycle and recording the zero drift. Test Stand Integration The MOD-B engine was thenThen the thrust was corrected by subtracting the mounted within the test stand of Facility VP-2 aszero-drift from the measured values, was shown in Fig. 5. This included mounting the

engine on the thrust balance support and making allTemperatures on the body of the engine and of the mechanical, electrical and fluid connections.

on various components of the thrust stand were The engine was mounted along the main axis of themeasured by means of K-type thermocouples. The thrust stand support bar and aligned horizontally withanode temperature was measured by means of an the point of load application on the calibrationoptical pyrometer with a wavelength range from 0.8 weight loading bar. Following engine alignment, theto 1.1 pm and a listed accuracy of ± 1 OC. The cathode and anode current feed cables werepyrometer had a spot size of 5 mm at a distance of connected. To prevent unexpected arc discharges.1 m. the exposed cathode current feed connections were

covered with a high temperature resistant insulator.RESULTS AND DISCUSSION The propellant feed connection was then made.

The test procedures are described below Engine Leak Test The propellant feed line wasfollowed by a description of the MOD-B/PCU test pressurized to 20 bar with filtered nitrogen to checkresults. for leaks in the line connections. No visible leakage

was allowed. The pressure was then slowly ventedTESTING PROCEDURES to atmospheric pressure.

The procedures included preparing the Thrust Balance Calibration Prior to sealing theengine for the test cycle; installing the PCU in the vacuum chamber and activating the vacuum plant.VP-2 facility: test stand integration: leak testing the the thrust measurement balance was aligned to insuresystem: calibration of the thrust stand: execution of accurate and reliable thrust measurements. Thethe test and; engine component and PCU check. alignment controls included:These steps are described in more detail below.

* Command the DAS to remove the thrustEngine Preparation All of the metallic parts were balance locking mechanism and lift thecleaned with alcohol (IPA) and dried with nitrogen. calibration weights from the loading bar.

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* Control the alignment of the loading bar in START-UP CIRCUIT VERIFICATIONthe horizontal direction and within thevertical plane of the engine support bar. This test was conducted to verify the

nominal parameters of the high voltage pulses* Control the loading and unloading of the required to initiate the arc discharge between the

weights on the loading bar. Repeat the anode and cathode of the arcjet thruster. The PCUactivity several times to guarantee proper was operated in its current-controlled mode with anweight application on the bar and seating input voltage of 60 V and an output current of 14 A.within the retainer. The test was conducted using two different

mass-flow rates: 50 mg/s and 60 mg/s. Figures 7* Control the alignment of the LVDT and 8 show the start-up pulses for 50 mg/s and 60

transducer bore within the transducer core mg/s respectively. The pulses show peak values ofwith weights applied and removed. The 2580 V and 2500 V respectively. The pulse shapesbore must situated near to the center of the are nominally the same. The recorded values arecore for best performance, lower than the values of the pulse measured on 900

ohm resistive load (Fig.9).13'" because at the ignition* Lock thrust balance in place and close the of the arc in the arcjet it's equivalent resistance

vacuum chamber, drops to a low value (7 ohm).

After the final pressure was reached in the vacuum SETTLING TIME MEASUREMENTchamber, the thrust balance was calibrated. A leastsquares linear fit was used to determine the thrust The settling time of the output current frombalance force versus LVDT voltage correlation. The the PCU. at the ignition of the arcjet, was measured.calibration was repeated until a correlation The PCU was operated in current-controlled modecoefficient of better than 0.9998 was obtained, with an input voltage of 60 V and a 15 A output

current. Again, two values of the mass-flow rateTest Execution A gas mixture simulating hydrazine were used: 50 mg/s and 60 mg/s. Figures 10 and 11(N, + 2H) was used for the PCU characterization show the profiles of the output current for 50 mg/stests. The test sequence was started by activating and 60 mg/s. respectively. The settling time is aboutthe PCU with the mass flow rate at either 50 or 60 the same for two mass flow-rates (400 ps).mg/s and the PCU current set point selected. Datawere recorded by the DAS using a sampling rate of OPERATION AT NOMINAL POINT2 s during the start up and 10 s during the test. Datawere printed every 60 s. The thrust values were The tests were intended to demonstrate thecorrected by subtracting the zero-shift measured at capability of the PCU to control the parametersthe end of each cycle. (current and power) around the nominal point. Prior

to the start of the PCU characterization tests, theComponent Check The engine and PCU were laboratory power supply system was used toexamined at the end of the test. The component establish baseline engine operating characteristics.conditions and critical dimensions were controlled Figure 12 shows the baseline voltage-currentand documented, characteristics for MOD-B arcjet operation with the

laboratory DC Power Supply (SORENSEN typeCHARACTERIZATION TEST RESULTS DCR 300-35A) at arcjet mass-flow rates of 50 and

60 mg/s. These characteristics were also measuredThe following functional tests were conducted at using the PCU powered with a FARNELL DCBPD with the PCU using the MOD-B 1 kW arcjet as Power Supply type H 60-50. These data points area load: also shown on Fig. 12. The characteristics at 60

mg/s are in good agreement.- START-UP CIRCUIT VERIFICATION- SETTLING TIME MEASUREMENT PCU Response to a Chance in Load The PCU was- OPERATION AT NOMINAL POINT: operated in current-controlled mode with a 12 A

- PCU Response To A Change In Load output current. The engine mass-flow rate was set- PCU Response To A Current Change at 60 mg/s. After the engine was turned on and- PCU Operation In Constant-Power Mode reached steady-state operation, the voltage was 82.5

V (Fig. 13. channel 1) according to the electricalThese tests are discussed below, characteristic shown in Fig. 12. Then the mass-flow

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rate was reduced to 50 mg/s with the same output ACKNOWLEDGMENTScurrent (Fig. 13. channel 2). The new current andvoltage were: 12 A and 76.2 V. respectively (Fig. The authors would also like to thank M.14). These are close to the expected values of 12 A. Magnanimi and D. Monaco for operating the72.5 V (Fig 12). facilities and assistance in conducting the tests.

Figure 15 shows the current and voltage vs. The research described in this paper wastime during one hour of operation at a mixture conducted by BPD Difesa e Spazio/FIAT CIEI andmass-flow rate of 50 mg/s with the output current set sponsored by the Italian Space Agency (ASI)at 12 A and the PCU in current-controlled mode. through contract No. 165-AF-1991. FIAT CIEIOperation was quite steady. The measured thrust served as subcontractor to BPD while Ansaldowas 0.201 N over this time period. Ricerche supported FIAT CIEI by developing the

inverter unit of the PCU. The contract technicalPCU Response to a Current Change The PCU was monitor at ASI is M. F. Rossi.operated in current-controlled mode with a 12 Aoutput current. The mass-flow rate was set at 60 REFERENCESmg/s. The voltage and current are shown in Fig. 13.The PCU output current was then changed to 8 A. 1. Bartoli. C. and Saccoccia, G., "European Electric PropulsionThe corresponding measured current and voltage Activities in the Era of Application." IEPC-91-003, 23rd IEPC.were: 8.25 A and 91.2 V (Fig 16). These values are Seattle. WA USA Sep ember 1993

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Development Program." Review Report No. 6. BPD Difesa ePCU Operation in Constant-Power Mode The PCU Spazio. Colleferro. Italy. BPD Publication No. NT AS3 11.03

Is.:l. 30 October 1992.was then operated in power-controlled mode at 1000W with the propellant (simulated hydrazine) 3. W. D. Deininger. E. Tosti. R. Di Stefano. F. Paganucci, F.mass-flow rate set at 60 mg/s. The voltage 84.1 V Scortecci and M. Andrenucci, "ASTP-3 MPD-Arcjet Development(channel 1) and current 11.67 A (channel 2) Program." Final Report -Draft. BPD Difesa e Spazio, Colleferro.measured during the test are shown in Fig. 17. The Italy. BPD Publication No. NTEAS300003. 23 July 1993.

actual power output to the engine was 976 W. The 4. G. Cruciani. M. Glogowski, W. D. Deininger and A. Trippi.difference between the set power and the actual "Advanced Laboratory Model, I kW-Class Arcjet Enginepower is due to the resolution of the setting Testing." IEPC 91-044. 22nd IEPC. October 1991.potentiometer. Then the mass-flow rate was changedto 50 mg/s. The voltage and current values changed 5. . D. Deininger. M. Glogowski. G. Cruciani. F. Scortecci and

, 1M. Andrenucci. "Comparison of Low Power Arcjet Operation Atto 77 V and 12.7 A for a power of 978 W according BPD and Centrospazio." AIAA 92-3115. 28th JPC July 1992.to the expected values (Fig. 18).

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suport ns s d Testing of a 1 kW Arcjet Using Hydrazine." IEPC-93-082. 23rdthat the PCU was able to start and operate a low IEPC. Seattle. WA. USA. September 1993.power arcjet under all conditions tested. Start-upvoltages of 2500 V were measured for the particular 9. E. Tosti and W. D. Deininger. " Emission Spectroscopy of aMOD-B low power arcjet geometry used during the I kW Arcjet Operating with Simulated Hydrazine," IEPC-93-134.tests. A settling time of 400 ps was found. The 23rd IEPC. Seattle. WA. USA. September 1993.

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23. Willenbockel. H.. Matthaeus. G. and Kinnersley. M.. 40. Smith. W. W.. Yano. S. E.. Armbruster. K., Roberts. C.."Development of a Power Control Unit for a Low Power Arcjet." Lichtin. D. and Beck. J., "Flight Qualification of a 1.8 kWIEPC-93-047. 23rd IEPC. Seattle. WA. USA. September 1993. Hydrazine Arcjet System." IEPC 93-007.23rd IEPC. Seattle. WA.

USA. September 1993.24. T. Yoshikawa. K. Onoe. T. Ohba. H. Yoshida. H. Suzuki andS. Morimoto. "Development of a Low Power DC Arcjet for Space 41. C. J. Sarmiento and R. P. Gruber. "Low Power ArcjetPropulsion." AIAA-87-1058. 19th IEPC. May 1987 Thruster Pulse Ignition. " AIAA-87-1951. 23rd JPC. June 1987.

25. T. Yoshikawa. K. Onoe. H. Yoshida. S. Kotani. 11. Suzuki 42. R. P. Gruber. "Power Electronics for a I kW Arcjet Thruster.and K. Uematsu. "Operating Characteristics of a I kW Hydrazine " AIAA-86-1507, 22nd JPC. June 1986.Arcjet Thruster." IEPC-88-108. 20lh IEPC. October 1988.

43. R. P. Gruber. R. W. Gott and T. W. Haag. "5-kW Arcjet26. H. Suzuki. K. Miyoshi. T. Yoshikawa and R. Nagashima. Power Electronics." 25th JPC. July 1989."DC Arcjet System for North-South Station Keeping ofGeosynchronous Satellite." AIAA-87-1039. 19th IEPC. May 1987. 44. M. Andrenucci and M. Sandrucci. "Development of a Power

Conditioner for a I kW Arcjet." IEPC-91-029. 22nd IEPC.

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2291 IEPC-93-Z51

Viareggio, Italy, October 1991. Subsystem and Its Components (Preliminary)." BPD Difesa eSpazio. Colleferro. Italy. BPD Document No. NTEARC00001.

45. W. D. Deininger and E. Detoma. "Definition and Trade-Off May 1993.of Low Power Arcjet Missions and System Parameters." IAF-92-0611. 43rd CIAF. September 1992. 49. S. Ferrari and E. Detoma. "Low Power Arcjet Diagnostic

Package Preliminary Design." FIAT CIEI - Divisione SEPA.46. W. D. Deininger. M. Atilli and R. Di Stefano. "Preliminary Torino. Italy. SEPA Doc. No. RR21040 Rev. 0.Specifications and Requirements for a Dual Mode On-BoardPropulsion System with an Arcjet Subsystem for North-South 50. S, Ferrari. E. Detona. W. D. Deininger. E. Tosti. F.Station Keeping." BPD Difesa e Spazio. Colleferro. Italy. BPD Scortecci. G. Capecchi and J. Scialdone. "Options and TradeoffDocument No. SSTARC00001. 30 October 1992. fora Spacebome Arcjet Diagnostics Package." IEPC-93-143.23rd

IEPC. Seattle, WA. USA. September 1993.47. W. D. Deininger. M. Attili. M. Vulpiani and E. Detoma."Low Power Arcjet System Requirements Definition for North- 51. G. Cruciani. E. Tosti. M. Glogowski. W. D. Deininger and G.South Station Keeping." AIAA-93-2223. 29th JPC. June 1993. Baiocchi, "Description of Arcjet Test Facilities at BPD," AIAA

90-2660. 21st IEPC. July 1990.48. W.D. Deininger. M. Vulpiani. R. DiStefano. E. Tosti. E.Detoma and S. Ferrari. "Description of an Arcjet Propulsion

Table 1. PCU Specifications.

Parameter Value

Input Power (W) 1800

Output Power (W) 1620

Input Voltage (V) 50 - 85

Output Current (A) 13.5 - 18

Output Voltage, Steady-State (V) 90 - 120

Output Voltage. Start-up (V) 4500

Pulse Energy (mJ) 50

Maximum Current Pulse in 2 ps (A) 5

Efficiency (at BOL) > 0.9

Phepullt leIOD. H, Ml - .

Craphle CUsket Compresla 'pellsat Ilet

•SIC i ClIels 1

L*Graph Cu IascetlAnode Cap

S•gelGk Ca lajectlesaede

•amp Fittit Inser Cathler

Figure 1. Schematic of MOD-B Low Power Arcjet.

Page 8 IEPC-93-251

IEPC-93-251 2292

P.t. ISV

0 ~ Al

-IS~TAU ChtW9N2 CIM

Is

Power supply0i fo Aln279215 G t rv

------< s u 5 erpp l y 1 0 0 0

2C --u -- <I 0 for A .BI it Arc~

swiclng4 M iure 3. 7 E 20ria Schemati o r I.

Page l 9--- <EPC9152 1

2293 IEPC-93-251

By-pass switch S3

- 1.4 pH 0-11ohm

+ L-N->-- -W(MAIN POWER

ArcjetSUPPLY

HIGH VOLTAGE

POWER SUPPLY -"o/ L S1 S2

Figure 4. Schematic of Laboratory Power Supply System.

CERAMIC SUPPORT RODS

MULT-WT. CALIBRATION SYSTEM LOCKING CLAMP WATER COOLED|~ I |HEAT SHIELD

THIN METAL HINGES

FLEX PIVOTS

Figure 5. MOD-B Arcjet Integrated Onto The Thrust Balance.

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IEPC-93-251 2294

0000000000

OCLoSC oo 1 2

BREADBOARD

VOLTAGE

P C IEEE-488 BUS D A S -4-

PERSONAL COMPUTER DATA ACQ.SYSTEM

O U CURRENT

Figure 6. Schematic of PCU Integration Within Test Stand.

-3, 000C u 2_.CCO 00 us 7, 01 00Q u

_______ J__ "i i_± -

+

Timobaso Osly/Poe Reference Made a c -r7 mMcin 1.OC us/div -3.C00000 us Left Realt-me (NORMAL) vmrker1 - -!7. 8.75 V

delo V VV) - 1.29 VSensitivity Offeet Probe Coupling

Channgl 1 706 V/div -2. 11950 k. 14".3 1' de BW li m (1H ahm)

Triger Edge

On Negative Edge Of Chonl

Trigger Level

___. .._ _ .____.. __ ... _ _ ,I I______ ._____

Chon - -70.500 V (<lee reject OFF)

Figure 7. MOD-B Start-Up Pulse at 50 mg/s Using PCU.

Pae IEPC-93-251 P Coupng

Channel 1 706 V/div -2.11950 k'.' 141.3 .i dc W Hiir (IN ohm)

Trlgger mode * Edge

On Negalive Edge Of ChoniTrigger- Level

Choni - -708.SCO V (noise reJect OFF)Holdo ff - 40.000 ne

Figure 7. MOD-B Stan-Up Pulse at 50 mg/s Using PCU.

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2295 IEPC-93-251

Timeba.. Delay/Pae Reference gods a4~rMain 1.00 ur/div -3.00000 us Left Realtime (NORMAL) V.-Oke,2(o1) - 458.750 Vy

Vmalke~ cal) -- 17. 1975 VSensitivity Offset pro"e Copingi as, t V c.1 i- _:.5a. V

Channel 1 70a V/div -2.21950 kV 141.3 .1 dc BW lim (im chm)

Trigger mode e EdgeOn Negative Edge Of ChantTrigger- LevelChanl - -700. 500 V (noise reject OFF)

Ho Idoff - 40.00 OW n

Figure 8. MOD-B Start-UP Pulse at 60 mg/s Using PCU.

CHI 2V 1% !us 3.41 V VERT

CH1gndJ

....q ..... . S .. 4 t-It. .0* .

Figure 9. Start-Up Pulse Delivered By The PCU To A 900 Ohm Resistive Load. 1 31

Page 12 IEPC-93-25 1

IEPC-93-251 2296

-8 0.000 us ___________ _____4g.0.0 us 40000_ ______ ____

Tiess Delay/Poo Reference MadeMain 200 us/div -500.000 us Left Realtime (NORMAL)

Seneitivity Offset Probe CouplingChannel 2 2.50 V/div 5.000C00 V 1.000 .1 dc SW lrn UMN ohm)

Trigger made @ EdgeOn Positive Edge Of Chan2Trigger Level

Chcn2 - 1. 25000 V (noise reject OFF)Holdoff - 40.000 no

Figure 10. PCU Output Current Transient at Start-Up;,

Shows Settling Time at a Mass Flow of 50 mg/s.

-50C. 00 s______ 400. 000 us ___________ _____1. 40000 m

Tiebse Delay/Pos Refesrence MadeMain 200 us/div -800. 000 us Left Realtime (NORMAL)

Sensitivity Offset Probe CouplingChannel 2 2.50 V/div 5.00000 V 1.000 .1 dc B8W lim (IN ohm)

Trigger mode . Edgeon Positive Edge Of Chan2Trigger LevelChcn2 - 1.25000 V (noise reject OFF)

Holdeff - 40.000 no

Figure 11. PCU Output Current Transient at Start-Up:

Shows Settling Time at a Mass Flow of 60 mg/s.

Page 13 IEPC-93-25 1

2297 IEPC-93-251

100

90 -

S 80so " .. 0 0w

S 70 - .

60-.. .

50 I I5 10 15 20 25

CURRENT (A)

50 mg/s 60 mg/s 50 mg/s with PCU 60 mg/s with PCU----- --- -- A -- 0 * IFigure 12. MOD-B V-I Characteristics at 50 and 60 mg/s;

Using Laboratory Power Supplies and PCU.

0 0-00 500. 009 s_. 00000

Tliebaee Delay/Poe Referenae Made NarkereMain 100 ue/div 0.0000 e Left Realtime (NORMAL) Vmaorker-2(c) - 0.00000 V

Vmarkerl Ccl) - -8.250C0 V

Seneitivity Offset Probe Coupling delto V (cc) - 8. 2000 vChannel 1 40.0 V/div -40.0000 V 10.00 .1 do BW 11m (1M ohm)Channel 2 8.00 V/div 8.00000 V 2.000 01 dc BW lim (IM ohm)

Trigger mode I EdgeOn Positive Edge Of ChantTrigger LevelChani - 0.00000 V (noise reject OFF)

Holdoff - 40.000 ne

Figure 13. PCU Voltage and Current Output at 60 mg/s.

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IEPC-93-25 1 2298

0.00000 * __500. u000 _. 000

Tlmebase Delay/Poe Reference Mode MarkereMain 100 ue/dlv 0.00000 a Left Realtime (NORMAL) Vmorke-2 () - 0. 000 V

Vmoaker.1o Cl) - -7. 0200 V

Seneitivity Offeet Probe Coupling delta V (Cl - 7.62500 V

Channel 1 40.0 V/div -40.0000 V 10.00 11 dc BW lim (1M ohm)Channel 2 8.00 V/div 8.00000 V 2.000 I1 dc BW lim (1M ohm)

Trigger mode i EdgeOn Poeltive Edge Of ChaniTrigger Level

Chanr - 0.00000 V (noiee reject OFF)Holdoff - 40.000 ne

Figure 14. PCU Voltage and Current Output at 50 mg/s.

0 -. 000 250. )00 me 500,000 me

.- ... .-.-.- ,-, .... 1 • i - -- = - --- w w- - Il -A--j

Tlmeboee Delay/Poe Reference Made MaorereMain 50.0 me/div 0.00000 a Left Realtime (NORMAL) Vmorker2(ol) - 0.00000 V

Vmrkierii l) - -7.7500 Vdlto V (ci) - 7.75000 V

Seneltivity OCFeet Probe Coupling dt V 7.000

Channel 1 40.0 V/div -40.0000 V 10.00 ,l dc BW lim (IM ohm)

Channel 2 8.00 V/div 4.00000 V 2.000 il dc BW lim (1M ohm) MeaejurmenteV ovg (c2) - 11.5598 V

Trigger mode i EdgeOn Negative Edge OF Chan2

Trigger LevelChon2 - -1.00000 V (nolee reject OFF)

Holdoff - 40.000 no

Figure 15. PCU Voltage and Current Output Over 1 hr of Operation.

Page 15 IEPC-93-251

2299 IEPC-93-251

...--I ---- _-

Timebase Delay/Poe Reference Mode Marke.r

Main 100 ue/div 0.00000 e Left Realtima (NORMAL) Vmrkr2(o) - 0.0000VmokeP C(o1) -- 9.12500delt. V (o) - Q. 12500 V

Seneltivity Offset Probe Coupling

Channel 1 40.0 V/div -40.0000 V 10.00 .1 do BW llm (IM ohm)Channel 2 9.00 V'div 4.00000 V 2.000 .1 dc BW lim (1M ohm)

Trigger mode i EdgeOn Negative Edge Of Chan2Trlgger Level

Chan2 - -1.00000 V (noise rejeot OFF)Holdoff- 40.000 ne

Figure 16. PCU Voltage and Current Output at 60 mg/s InCurrent-Controlled Mode at 8.25 A.

0C. *. -250.9 00 me 500._ 000 me

~ 1-

. --1 -- V

Timebase Delay/Poe Referonce Mode Mas.ursmens

Main 5C.0 me/div 0.00000 a Left Roaltime (NORMAL) V v9g <c

t) - -84.1752 VV avg (02) - 11.e727 V

Sensitivity Offset Probe CouplingChannel 1 40.C V/div -40.0000 V 10.00 Il dc BW lim (1M ohm)Channel 2 8.00 V/div 4.00000 V 2.000 .1 dc BW lim (1M ohm)

Trigger- mode s EdgeOn Negative Edge Of Chan2r'lgger LevelChan2 - -1.00000 V (noise re-ject OFF)

Holdoff - 40.000 no

Figure 17. PCU Voltage and Current Output at 60 mg/s InPower-Controlled Mode at 976 W.

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IEPC-93-251 2300

T Dly/Pon Reference giods Mc.-on.nte~4an 5.0 e/dv 00000 a Lof Reltie (ORML)V cV9 CcI) -- 77.0100 VMai 5.0 o/iv 0.000 a -at oolim (NRML)V avg <a2)- 12.1113 V

Sensitivity Offset Probe CouplingChannel 1 40.0 V/div, -40.0000 V 10.00.01 dc We lrn CIN ohm)channel 2 8.00 V.'div 4.00COO V 2.000 61 dc OW 1rn (,M ohm)

Trigger mode e EdgeOn Hoiative Edge Of Chcn2Trigger Level

Chan2 - -1.00000 V (nois reject OFF)Holdoff - 40.000 no

Figure 18. PCU Voltage and Cur-rent Output at 50 mg/s InPower-Controlled Mode at 978 W.

Page 17 IEPC-93-25 1