For an approximate design of aerospike nozzle, some numerical and experimental studies and conclusions are given here. The numerical simulations contain of both the Method of Characteristic and the solving of the Navier-Stokes equations. The experimental system and several kinds of the test aerospike nozzle are showed here. Some tests and calculations curves are presented and explained. Introduction Aerospike nozzle is much complicated in structure than that of the bell nozzle, so the optimized structural design of an aerospike nozzle has more questions need to be answered in ahead. For example, what's the best inclination angle of the side nozzle cell? How much effect to the nozzle performance that the plug base will cause when the supersonic gas flow around the base is closed or unclosed? The study conducted here is trying to answer questions like these. Experimental System The schematic diagram of the experimental system is showed in Figure 1. The system mainly includes the gaseous Oxygen supply system, the pressurized feed system of the fuel ethyl alcohol, the pressurized water circulating cooling system, the high-pressure air source, the vacuum pump and two large cylindrical vacuum exhaust tanks, the amplifier * Professor, School of Astronautics, BUAA f PH.D. Student, School of Astronautics, BUAA * Engineer, School of Astronautics, BUAA Copyright © 2001 by the American Institute of Aeronautics and Astronautics Inc. All right reserved. and computer data acquisition system, manual controlling and monitoring system, the cubic test vacuum room and the test aerospike engine inside it. The measuring parameters are mainly composed of two chamber pressures, chamber temperature, 2-4 oxygen head pressures, 2-4 fuel head pressures, chamber pressure and temperature of the igniter, head oxygen and fuel pressures of the igniter, mass flow rates of oxygen and fuel. Test Aerospike Nozzle After thousands of optimized performance computations have been done by using Method of Characteristic, several kinds of aerospike nozzle configurations have been formed. The configurations composed of bell side nozzle circular-linear composite structure with curved plug contour shown in Figure 2 and Figure 3, rectangular throat linear aerospike nozzle with different side nozzle angles (Fig. 4) and water cooled square shape linear aerospike nozzle (Fig. 5). Most of them will be used to do the experiments to confirm the effectiveness of the design. The model in figure 2 is a practical useful model suggested by us. The benefit of it is that the conventional axisymmetrical thrust chamber can be used with little change, and that the base is always closed both on ground and in a certain flight altitude. The model in figure 3 is a simplified one by using of 14 conical nozzles, 4 thrust chamber heads and one common chamber. The base mass flow rate percent can be adjusted according needs. This model was designed specially to test the optimized base mass flow rate. The model in figure 4 is a two-cell aerospike 1 America Institute of Aeronautics and Astronautics c)2001 American Institute of Aeronautics & Astronautics or Published with Permission of Author(s) and/or Author(s)' Sponsoring Organization. nozzle and is specially used to test the best inclination angle of the primary nozzle or side nozzle. The model in figure 5 is a four-unit aerospike nozzle. Two of them are made up of 5 thrust chamber units, and the others are formed by 2 units. Each unit will be cooled by water so that the model can work in a higher temperature and longer time. It was specially designed to test the effects with or without base closing. Test Results From the tests, some important parameters such as thrust, chamber pressures are measured. Some other interested parameters such as nozzle efficiency, mass flow rate can be calculated by the measured data. Briefly speaking, the results will mainly contained of the multi-tube ignition properties to 14 separated thrust chamber cells, the altitude performance compensating property and its comparison for different nozzle structures, the performance contribution by the plug base and so on. Figure 6 shows the test results of multi-tube ignition. Figure 7 gives the ignition property of the test model in Figure 4. Figure 8 presents the working procedures of the same model. In figure 6, Tj, Pi? P0head and Tc represent the temperature and pressure inside the chamber of the igniter, pressure of the oxygen head position and the temperature at the exit position of several igniter tubes, respectively. Figure 7 still shows the working procedure of the igniter, but it is a procedure accompanying the working procedure of the aerospike engine. Here Pfhead is the fuel head pressure. Figure 8 shows the results of aerospike engine (model in figure 4) of the same test as shown in figure 7. Here F, Pc, PCOhead> Pcftead and Tc represent the thrust, common chamber pressure, one oxygen and one fuel head pressure of the engine, and the common chamber temperature. Numerical simulations Figure 9 shows the optimized results by using Method of Characteristics (MOC). The given conditions are chamber pressure pc =3.0MPa, stagnation temperature T* =3260K, expansion ratio of the primary nozzle 8j =1. From this figure we can see that the best primary nozzle inclination angle 8 is nearly equal to 30 at different backpressure or height. Figure 10 gives the similar results by solving the Navier-Stocks (NS) equations. Figure 11 given the computed results of the cooling at the primary nozzle throat cross section. The calculation conditions are pc =3.0MPa, T* =3260K, the inner wall thickness 8=1.2/ww, the width and deepness of the tunnel 1.7X 1.2. Here, Twg, Twi, Twaterin and Twaterout represent the gaseous sidewall temperature, the liquid sidewall temperature, the water inlet and outlet temperature, respectively. Conclusions For the test research are still undergoing, the complete conclusions can't be given now, except that the best inclination angle of the primary nozzle is probably about 30°. Another conclusion is that the angle will be affected strongly by other parameters . The thrusts of the aerospike nozzle is a function ofpc, Sj, 0, pa, total expansion ration et and the base mass flow rate. This will be also shown later. Reference [1] Dai Wuye, Liu Yu, Zhang Zhengke, Qin Lizi, Wang Yibai, "Numerical investigation on Linear Aerospike Nozzles," Prepared for 37 AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, AIAA2001-3568, Salt Palace, Salt Lake City, UT, 8-11 July, 2001. America Institute of Aeronautics and Astronautics c001 Am eican Intitute of Aenautics & Astnautics or Pulished w ith Perm ision of Auor(s) ad/or Auor(s)' Spsoring O rgazation. A m erica Intitute of A eroautics nd A strautics c)2001 American Institute of Aeronautics & Astronautics or Published with Permission of Author(s) and/or Author(s)' Sponsoring Organization. Figure 2. Circyiar-Mnear composite aerospike oozzle model. Figure 3 Circular-linear composite aerospike nozzles without cooling Figure 4 Rectangular throat linear aerospike nozzles with changeable side nozzle angle Figure 5 Water-cooled square shape linear aerospike nozzles America Institute of Aeronautics and Astronautics c)2001 American Institute of Aeronautics & Astronautics or Published with Permission of Author(s) and/or Author(s)' Sponsoring Organization.