Sungyong An

Scaling and Evaluation of Pt/Al2O3 Catalytic Reactor for Hydrogen Peroxide Monopropellant Thruster

A scaling methodology of hydrogen peroxide monopropellant thruster is described. As the decomposition process of the hydrogen peroxide on the surface of catalyst bed is extremely complex, empirical method was taken for design purposes. A small-scale thruster was fabricated and important design parameters, including temperature at different locations of the catalyst bed, were measured. Based on the measurement, the catalyst bed size as a function of the propellant flow rate was estimated. Using the scaling methodology, a catalyst bed configuration for a thruster capable of delivering 50 N was estimated. The thruster built on this design produced 42 N at sea level and specific impulse of 123 s.

Chugging Instability of H2O2 Monopropellant Thrusters with Reactor Aspect Ratio and Pressures

Among the three types of instabilities, the low-frequency instability (chugging instability) was experimentally investigated with respect to the chamber pressure and aspect ratio (L=D) of catalytic reactors in a monopropellant thruster. ThreeH2O2 thrusterswere used, and two parameters were found to be the dominant factors that generated a chugging instability of the order of several tens of hertz. Ahigh chamber pressure and lowL=D values (lowpressure drop across the catalyst bed) were preferable for reducing pressure oscillation inside the reaction chamber. In addition, it was found that these two parameters were not independent but coupled; therefore, the point where chugging instability occurred varied slightly depending on the interaction between these parameters.

Comparison of Catalyst Support Between Monolith and Pellet in Hydrogen Peroxide Thrusters

The effect of catalyst support on the performance of monopropellant thrusters was investigated. In the present study, two support materials (monolith honeycombs and alumina pellets) were tested and their relative performances were compared. A reference catalyst (Na 0.2 MnO 2 ) was coated on both catalyst supports, and 90 wt% hydrogen peroxide was used as the monopropellant. Two test thrusters of different sizes were fabricated, and the performance of each thruster when using monolith honeycomb and alumina pellets as the catalyst bed was evaluated by measuring the product-gas temperature at the rear end of the catalyst bed and the pressure of the gas at the front and rear ends of the catalyst bed; during these measurements, the feed pressure of the propellant was fixed. Under the given test conditions, the performance of the thrusters was better when using alumina pellets as the catalyst support than when using monolith honeycomb. Since the monolith support was less reactive than the pellets, pressure buildup in the former case was relatively small; consequently, the chamber pressure and temperature were lower when using the monolith support than when using the pellet support. The pressure drop across the catalyst bed was moderate in both cases (0.02-0.1 bar in the case of a monolith and 0.3-0.7 bar in the case of a pellet catalyst).

Performance Characteristics of Hydrogen Peroxide/Kerosene Staged-Bipropellant Engine with Axial Fuel Injector

A1200N vacuum-thrust-class staged-bipropellant engine that uses decomposed hydrogen peroxide as an oxidizer and kerosene as a fuel was developed and tested with the aim of investigating an axial fuel injector integrated with a distributor. This fuel injector geometry, where fuel is injected into the turbulent flow of decomposed hydrogen peroxide, was tested to evaluate the influence of the designed injector on engine performance with respect to the equivalence ratio, the pattern of fuel injection orifices, and the characteristic length L . For characteristics such as autoignition and stable combustion, firing tests over awide range of equivalence ratios from 0.26 to 1.86were carried out. Autoignition was successfully achieved under all experimental conditions. The pressure rising time from monopropellant to bipropellant mode and the pressure fluctuation in the combustion chamber were approximately 100 ms and less than 1:1%, respectively. In the parametric study, the characteristic velocity c and its efficiency were influenced by the pattern of fuel injection, whereas varying the orifice diameter had no effect. The effect of L was also estimated, and the c efficiency was measured to be over 95% for all equivalence ratios at an L of 1.20 m.

Transient Behavior of H2O2 Thruster: Effect of Injector Type and Ullage Volume

ROCKET-GRADE hydrogen peroxide has been used as a monopropellant and a storable oxidizer. However, because of the demand for a higher specific impulse, hydrazine andN2O4 are being used as the monopropellant and storable oxidizer, respectively. Recently, due to concerns regarding propellant toxicity, there has been a renewed interest [1] in the use ofH2O2 in propulsion systems [2–10]. A monopropellant thruster is operated in either the continuous or pulse mode. The thrust force and pressure instability are important issues in the continuous mode. For generating the desired thrust, the catalytic reactor size required for completely decomposing the propellant must be determined [8]. However, in the pulse mode (the main operationmode for attitude control systems), the response characteristics of the thruster are important. The catalyst activity, thruster component design (including the injector design), manifold volume, ullage volume in the reactor, and operating pressure influence the thruster response time. Tian et al. investigated the response time when using a combination of PbO and MnO2 catalysts [11]; they found that Ir=Al2O3 is unsuitable for use as a catalyst in a H2O2 monopropellant thruster [12]. Xu et al. studied the activities of various catalysts during H2O2 decomposition [13]. El-Aiashy et al. reported that the catalyst activity ofMnO2 increased when ZnO was added [14]. Hasan et al. reported that the activity ofMnO2 increased when promoters such as Ni, Cu, Bi, and Ce were added [15]. None of the aforementioned studies have addressed the effect of thruster design parameters on response times, although a few researchers have measured the thruster response time. Optimization of the thruster design (determination of the appropriate injector and ullage volume in the reaction chamber) can also influence the response characteristics. Therefore, we investigate the response characteristics of H2O2 monopropellant thrusters for three different thruster designs andmeasure the response times by varying the injector type, reactor volume, and catalyst grain size. AMnO2=Al2O3 catalyst is used for the decomposition of concentrated H2O2 (90 wt%).

Hydrogen peroxide thruster module for microsatellites with platinum supported by alumina as catalyst

This research was financially supported by a grant to MEMS Research Center for National Defense funded by Defense Acquisition Program Administration.

Catalyst Bed Sizing of 50 Newton Hydrogen Peroxide Monopropellant Thruster

A 50 Newton monopropellant thruster being developed for attitude control in a variety of aerospace application systems is described in this paper. Ninety percent hydrogen peroxide was selected as a propellant , since it is much less hazard ous than hydrazine. A scaled down thruster with platinum on aluminum oxide in the reaction chamber was tested to determine propellant decomposition onto a catalyst . The size of catalyst bed was determined as 3 cm in diameter and 4 cm in length from scale up method. A scaled up thruster, 50 Newton level at vacuum, wa s evaluated by decomposition efficiency based on temperature, �T, efficiency of characteristic velocity, �C* , and measurement of thrust. The performance of a scaled up

Development of a Liquid Propellant Rocket utilizing Hydrogen Peroxide as a Monopropellant

This work was supported by the Korea Science and Engineering Foundation(KOSEF) grant funded by the Korea government(MEST) thourgh NRL(No. R0A-2007-000-20065-0)

Autoignition Tests by Injecting Kerosene into Vortex of Decomposed Hydrogen Peroxide

Using decomposed hydrogen peroxide as an oxidizer and kerosene as a fuel, a 1200 N vacuum thrust-class staged-bipropellant engine has been developed and tested with aim to investigate an axial fuel injector integrated a distributor. This fuel injector geometry that injects a fuel into turbulent flow of decomposed hydrogen peroxide was tested to evaluate influence of the designed injector on engine performance. For the characteristics such as autoignition and stable combustion, firing tests over a wide range of equivalence ratio from 0.26 to 1.61 were carried out. Autoignition was achieved in all experimental conditions and pressure variation in the combustion chamber was as low as ± 1%. The efficiency of characteristic velocity, C * , was measured at or over 100% in fuel-lean conditions and from 88% to 94% in fuel-rich conditions at the L * of 0.95 m.

Pulse Response Times of Hydrogen Peroxide Monopropellant Thrusters

The transient behavior of a monopropellant thruster was investigated. Throughout the study, MnO2/Al2O3 was used as the catalyst bed in order to eliminate the influence of the catalyst bed on the transient behavior. Three 50 Newton level test thrusters with different injectors, ullage volumes, and bed sizes were built. H2O2 (90 wt%) was used as the monopropellant in the thrusters and experiments were carried out using these thrusters. The transient characteristics of the thrusters—the ignition delay and the time taken for pressure rise and pressure decay—were determined. Among the injectors considered, the transient characteristics of the shower-head injector are better than those of the spray injector The shower-head injector showed the best performance when a catalyst bed with a small volume was used: the ignition delay was 14 ms; the pressure rise, 108 ms, and the pressure decay, 94 ms.