/_1073 . : H2 ARCJET PERFORMANCE MAPPING PROGRAM /A/ -=._ 0 Subcontract 90-1314/7293 ..... .'_, _PORT -,I" ...............9.2.-.R.-1.6.15 ",0 0 cO 0 _n 0', Z _ 0 Prepared for: O N ::Texas _Tech.- Univer=l_y)NASA_ LeRC_$DI_O Submitted by: Rocket Research Company Olin Aerospace Division 11441 Willows Road N.E. . Redmond, WA 98073-9709 January 31. 1992 ROCKERTESEARCCHOMPANY _lin _nos_,_c_o_v_s_(_. REDMOND, WASHINGTON .... MDB#3d/i 11888-H2AJ m H2 ARCJET PERFORMANCE MAPPING PROGRAM Subcontract 90-1314/7293 FINAL REPORT L 92-R-1615 Prepared for: Texas Tech. University/NASA LeRCISDIO Submitted by: Rocket Research Company Olin Aerospace Division 11441 Willows Road N.E. Redmond, WA 98073-9709 January 31, 1992 MDB#3d/117866-H 2AJ DOCUMENT REVISION RECORD i / DOCUMENT NO. REVISION DESCRIPTION OF cHANGE/ EFFECTIVITY AND DATE REVISION AND PAGES AFFECTED i Orig. 1/31/92 214192 m N = = : 0434 REV A |3/81) i TABLE OF CONTENTS PAGE 1.0 INTRODUCTION/SUMMARY 2.0 REVIEW OF PASTWORK 5 qlE 3.0 DESIGN/ANALYSIS SUMMARY 5 4.0 TEST FACIUTIES/PROCEDURES 17 = = z 5.0 TEST RESULTS 23 6.0 DISCUSSION 26 m 7.0 CONCLUSIONS/RECOMMENDATIONS 41 m,y REFERS 41 we=/ APPENDIX - TEST DATA m roll MDB#3d/117866-H 2AJ LIST OF FIGURES FIGURE PAGE 1-1 Gianninl Arcjet Concept 1 1-2 Isp vs. Efficiency - Hydrogen Propellant, 10 kW 4 2-1 Giannini Thruster 6 2-2 H2 Arcjet Data Comparison 7 _ 3-1 Giannini Scaling 9 3-2 Analysis Results - Giannini Style Thruster 10 3-3 Regenerative Thruster Design 11 3-4 Arcjet Assembly 13 3-5 Arcjet Piece Parts 14 3-6 Non-Regenerative Thruster Design 15 3-7 Finite Element Thermal Model 16 3-8 Final Thermal Model Predictions 18 4-1 Vacuum Level vs. H2 Mass Flow 19 4-2 Electrical Power Delivery Schematic 20 4-3 Giannlnl Arcjet Propellant Schematic 21 5-1 Isp vs. Efficiency - Hydrogen Propellant 24 5-2 Isp vs. Efficiency- Hydrogen Propellant, 10 kW 25 5-3 Anode Temperature Profile - Specific Power = 60 MJ/kg 27 5-4 Anode Temperature Profile - Power = 10 kW 28 5-5 Arc Voltage vs. Arc Current 29 5-6 Arc Voltage vs. Mass Flow Rate 30 5-7 Inlet Pressure vs. Mass Flow Rate 31 6-1 Predicted Specific Impulse vs. Enthalpy 33 6-2 Arc Off Isp vs. Specific Power 35 6-3 Regenerative Gas Power vs. Specific Power 36 6-4 Thermocouple Locations 38 6-5 Estimated Radiation Losses vs. Specific Power 39 6-6 Estimated Radiation Losses vs. Efficiency 4O MDB#3d;117866-H 2 AJ LIST OF TABLES TAB_ PAGE 4-1 Instrumentation List 22 i 6-1 Regenerative Thrust Data, 10 kW 34 37 6-2 Radiation Loss Estimates, 10 kW i,w IIjL _ i == _I__L: a = -- -_ T MDB#3dl117866-H 2 AJ w ,%1 _ FINAL REPORT zz w H2 ARCJET PERFORMANCE MAPPING PROGRAM Subcontract 90-1314/7293 -_ SDIOINASA/Texas Tech. 1.0 Introduction/Summary w _ This is the final report for subcontract 90-1314/7294 prepared for Texas Tech. University __ by Rocket Research Company. This work was performed during the period of March, 1991 to January, 1992. M High power H2 arcjets are being considered for electric powered orbit transfer vehicles Im (EOTV). Mission analyses Indicate that the overall arcjet thrust efficiency is very important since Increasing ihe efficiency increases the thrust, and thereby reduces the total trip time for the same power. For example, increasing the thrust efficiency at the same specific impulse from 30% to 40% will reduce the trip time by 25%. For a 200 day mission, this equates to 50 days, which results in lower ground costs and less time during which the payload is dormant. Arcjet performance levels of 1200 seconds specific impulse (Isp) at 35% to 40% efficiency El m with lifetimes of over 1000 hours are needed to support EOTV missions. The power level targeted for the present work was 10-15 kW. Such a thruster can be used to support EOTV's having power levels from 20 kW and higher by firing several thrusters simultaneously. Although higher efficlencles are generally obtained at higher powers, it was W thought that this power level provided an appropriate balance between efficiency and near term mission suitability. Little work has been done recently to optimize the H2 arcjet performance. Work done in the 1960's by the Giannini Corporation focused on a unique arcjet configuration wherein the arc attaches in a subsonic region upstream of the throat, and which used regenerative cooling passages to improve the efficiency. This configuration is shown in Figure 1-1. Very high efficiencies were quoted for this configuration, and a 500 hour lifetest was completed at 1000 MDB#3dl1171)66-H 2 AJ I _r GIANNINI ARCJET CONCEPT q,V (-) L , CONSTRICTOR ANO0_ ( + ) i L-- NOZZLE = ! L' R OPELLANT INJECTCR _% r_ Ill Figure 1-1 m = r seconds Isp and 55% efficiency at 30 kW input power. In theory, this configuration reduces the frozen flow losses by increasing the recombination in the subsonic constrictor. The regenerative passages both cool the constrictor region and pre-heat the incoming propellant. These high efficiency levels were not achieved during tests conducted at AVCO during the same period, nor has NASA or RRC come close with recent Conventional arcjet tests. Because of the potential to achieve very high efficiency levels, the objective of this program was to evaluate the ability of a scaled (_iannini-style thruster to achieve the performance levels quoted in the previous literature while operating at a reduced nominal powel; of 10 kW. To meet ._ =. this objective, a review of the past literature was conducted, scaling relationships were developed and applied to establish critical dimensions, a development thruster was designed with the aid of the plasma analysis model KARNAC and finite element thermal modelling, test hardware was fabricated, and a series of performance tests were conducted in RRC's Cell 11 vacuum chamber with its null-balance thrust stand. z z ' rL=_ The results obtained with the single configuration tested are encouraging. The thruster operated v-._a very stably over a power range of from 4 kW to 12 kW. There was virtually no erosion seen after approximately 20 hours of operation. Performance values were very repeatable. The efficiency levels obtained up to about 950 seconds Isp were significantly higher than for w_S=_._. conventional designs. Above that Isp level, the efficiency was lower. These trends are shown in _m Figure 1-2 for 10 kW thruster power, along with RRC IRAD and NASA conventional data. Although the initial results fall short of reproducing Gianninl's reported performance levels, it is recommended that further investigations of this novel arcjet concept be conducted. Body r temperature measurements and estimates of the effectiveness of the regenerative passages suggest that the efficiencies could be improved by reducing the thermal losses to the long subsonic constrictor. As will be discussed in more detail in the rest of the report, it appears that the constrictor was sized too large for this power level. Modifications to Increase the temperature of the constrictor region are also recommended. Specific design recommendations z •are presented in section 7.0 Conclusions/Recommendations. m = MDB#3d/I17866"H2AJ ,I..I 0 .,-, a_ ew a i J m (spuooes)dsl