A99931 331 th AIANASME/SAElASEE Join Propulsion Conferenc J 111 For permission to copy or republish, contact American institute of Aeronautics and Astronautics 1801 Alexander Bell Drive, Suite 500 Reston, Virginia 20191-4344 Olwen Morgan ([email protected]) Dennis Meinhardt ([email protected]) PRIMEX Aerospace Company Redmond, Washington Abstract: Monopropellant propulsion systems offer many advantages for mid-size spacecraft, ha&ding simplicity of operation, high reliability, and Ilow cost. Much effort recently has 0een centered on developing lower toxicity propellants and electric propulsion altesnatives, and many of these options show significant promise. This paper will show that hydrazine monopropellant propulsion systems continue to be an excellent choice for many spacecraft applications, and that on-going work to simplify designs and fueling carts bas reduced costs and increased simplicity. We will also explore trade studies where some of these other propulsive options are shown to be more appropriate. Introduction REA Rocket Engine Assembly REM Rocket Engine Module Since their first flight application in 1966 on Martin TLV ThresholdLimit Value Marietta’s Titan I launch vehicle’s Transtage, UDMH Unsymmetrical Dimethyl Hydrazine monopropellant hydrazine rocket engines with Introduction/Historv spontaneou? catalyst have often been the propulsion of choice. Hydrazine as a propellant offers The advantages of hydrazine as a monopropellant was substantially improved specific impulse over cold recognized early on. In 1949, the Jet Propulsion gas, and hydrazine systems require half as many Laboratory funded both engine and catalyst development, tanks, propellant lines, and valves as a comparable and has been credited with the start of the industry’. bi-propellant system. Versatile and dependable, a Catalytic hydrazine thrusters and systems have evolved monopropellant thruster will operate in steady state, sinca their first space flight in 1966, becoming less on-pulse, and off-pulse modes. mission specific and more commercially oriented. Over Nomenclature time, PRIMEX Aerospace Company (formerly Rocket Research Company and Olin Aerospace Company) has ACGIH American Conferenceof GovernmentalIndustrial designed, built, and tested monopropellant hydrazine Hygienists thrusters for many purposes including some key ACS Attitude Control System interplanetary missions. In the year 2000 we expect to CSD Chemical SystemsDivision, United Technologies ship our lO,OOO* thruster. We are particularly proud of DFA Design for Asstmbly our contributions to the following interplanetary missions: DFM Design for Manufacturing EHT ElectrothermalHydrazine Thruster Viking 1 and Viking 2’. Landed on Mars in 1975. F Thrust, N Actively guided descent using three 2700N GE0 Geosynchr&ous or GeostationaryOrbit throttleable engines for a soft landing, as well as GPS Global Positioning System HAN Hydroxyl Ammonium Nitrate attitude control and delta-V for the cruise stage. HPB Hydrazine PropellantBlend Voyager 1 and Voyager 2. Launched in 1977, these IDLH Immediately Dangerousto Life or Health satellites are still operational today as they approach ISP Specific Impulse, set LEO Low Earth Orbit the heliopause. The 20N and 445N engines have LTHG Low TemperatureHAN Glycine long since been jettisoned, but the 1N REAs are still MIT Minimum Impulse Thruster functioning nominally. MMH Monomethyl Hydrazine NIOSH National Institute for Occupational Safety & Magellan. Launched in 1989 with residual Viking Health 20N REAs, Voyager 1N REAs, and new MR-104A NVR Non-Volatile Residue 445N REAs mounted on four similar but non- OAM Orbit Adjust Module identical Rocket Engine Modules, this satellite OSHA OccupationalSafety and Health Administration mapped the surface of Venus for four years. Fuel and PAC PRIMEX AerospaceCompany valve temperatures were substantially hotter than PEL PermissibleExposure Limit expected; operation at 140 “C was validated in Pf Feed or Inlet Pressure,Bar support of this mission3. PPT PulsedPlasma Thruster Copyright01999 by theAmerican Instituteof Aeronauticsand Astronautics. All rights reserved. American Institute of Aeronautics and Astronautics 99-2595 0 Mars Pathfinder. Mars landing July, 1997. MR- the middle, catalytic monopropellants offer low cost, 11 IC 4.4N REAs provided attitude control flexibility, and a wide thrust range. Figure 1 shows during the cruise stage and to position the theoretical performance for a range of monopropellant satellite to deploy the rover Soujourner. choices. Table 1 shows some physical properties. @ Mars Climate Orbiter and Mars Polar Lander. Hvdrazine Mars mapping and landing expected in the fall of Hydrazine propulsion systems offer the greatest heritage 1999. Cruise stage REMs for both satellites and of the candidates with a wide array of choices in qualified 7-lContent 1600 I I , I / Low Temp / HAN/Glycine __ Blend I I I I --- . 190 200 210 220 230 240 250 260 270 280 290 Vacuum Specific Impulse, Isp (set) dual 300N REMs on the lander for the first thrusters, as well as tanks, latch and pyro valves, service actively guided descent since Viking landed on valves, and all the other items needed to assemble a Mars. propulsion system. Their reliability is high, its performance is moderate, and its cost relatively low. Its While hydrazine has a strong heritage, other long-term storage stability is excellent. propellants and blends offer potential for improved performance and reduced toxicity. Some of these Compatible dual mode thrusters exist for missions choices include low temperature HAN-based requiring large delta-V, and electrothermal hydrazine propellants with performance approaching that of thrusters and arcjets offer high performance compatible hydrazine, high temperature HAN-based propellants choices for such applications as geostationary satellite with performance approaching that of a bi-propellant station-keeping. One of the issues associated with system, hydrogen peroxide, and hydrazine blends. hydrazine is its toxicity. While novel fueling approaches can mitigate some of the toxicity concerns, other Pronellant Choices propellants show promise of reduced toxicity and For extremely small satellites (10 kg class), attendant reduced fueling costs. propulsion is usually not an option. For slightly Low Combustion Temperature Hvdroxvl Ammonium larger satellites (100 kg class) with low propulsive Nitrate (HAN) Blends requirements, cold gas has typically been used. For launch vehicles, only solid motors and/or liquid bi- Laboratory thruster testing with “low combustion propellant stages are adequate to escape earth’s temperature” blends of HAN/Glycine (refer to Figure 1) gravity. Electric propulsion systems offer high has demonstrated proof of concept for this new family of specific impulse, but carry both the cost and weight environmentally friendly monopropellants. These HAN of the electronics and power conditioning hardware blends have a higher density and lower melting point than with them. But for a broad band of applications in hydrazine, and because there is no toxic vapor pressure, Copyright01999 by theAmerican 3 Instituteof Aeronauticsand Astronautics. All rights reserved. American Institute of Aeronautics and Astronautics 99-2595 ground support operations are simplified. Additionally,-with these HAN-based blends, there are no identified carcinogenic issues. Table l-Physical Properties of Some Typical Monopropellant Fuels Characteristic Hydrogen Peroxide, 90% Melting -11.5 Point, “C Boiling Point, 113.5 Not 141.7 T Measured Specific 1.0 1.42 1.4 Gravity Figure 2-HAN Thruster Firing at Sea Level Explosion 232 Not 149 Temp, “C4 available Hiah Performing Hvdroxvl Ammonium Nitrate (HAN) Long-Term Excellent if Slowly Slowly Blends Storage kept decom- decom- High temperature HAN-based monopropellants also show Stability blanketed poses to poses to promise. Theoretically, performance will approach that with inert form form of conventional bi-propellant systems, but without the gas acidic bi- water and need for dual tanks, dual valves, dual propellant lines and products oxygen other duplicate system hardware. The biggest challenge Toxicity- 0.01 Vapor 1.0 offered by the high temperature blends is their ACGIH TLV, pressure decomposition temperatures, with gas temperatures ppm ranging near 2200 “C. Material choices and ignition Toxicity- G-+%2- 1.0 methods for monopropellants at these temperatures are OSHA PEL, 1 pressure limited. Recent ignition testing with a blend of HAN, ppm methanol, and water shows promise for monopropellants Toxicity- “” 75 with specific impulses of 270 or greater. NIOSH IDLH, ppm Hvdroaen Peroxide Other Strong Hydrogen peroxide has been proposed for use in small Precautions oxidizer, satellites instead of nitrogen propulsion7. Laboratory corrosive testing, using bench-distilled hydrogen peroxide resulted Figure 2 shows a flight concept HAN thruster firing in an impressive display of thrust with few attendant risks with the “low temperature” HAN/glycine (LTHG) to the by-standers. But lack of long term stability of propellantI blend. This thruster was made from the hydrogen peroxide renders it impractical for most satellite same materials of construction used in a hydrazine applications. However, hydrogen peroxide would appear thruster. Demonstration tests, like that shown in to have significant applications for monopropellant Figure 3, have shown clean, reliable, stable attitude control thrusters when coupled with a bi- decomposition/combustion of the propellant in a propellant system