View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Embry-Riddle Aeronautical University The Space Congress® Proceedings 1967 (4th) Space Congress Proceedings Apr 3rd, 12:00 AM Simulated Space Testing of Propulsion Units and Systems Joel Ferrell ARO, Inc. Rocket Test Facility, Arnold Engineering Development Center, Arnold Air Force Station, Tennessee Follow this and additional works at: https://commons.erau.edu/space-congress-proceedings Scholarly Commons Citation Ferrell, Joel, "Simulated Space Testing of Propulsion Units and Systems" (1967). The Space Congress® Proceedings. 4. https://commons.erau.edu/space-congress-proceedings/proceedings-1967-4th/session-14/4 This Event is brought to you for free and open access by the Conferences at Scholarly Commons. It has been accepted for inclusion in The Space Congress® Proceedings by an authorized administrator of Scholarly Commons. For more information, please contact [email protected]. SIMULATED SPACE TESTING OF PROPULSION UNITS AND SYSTEMS 1 Joel Ferrell2 ARO , Inc. Rocket Test Facility Arnold Engineering Development Center Arnold Air Force Station, Tennessee ABSTRACT for future exploration and utilization of both near space and deep space required An estimate of the major simulation duplication of the environmental condition requirements for high-altitude tests of within controlled space simulation facili­ rocket engines and rocket engine systems is ties . As missions or objectives have become presented. The facilities required to pro­ more extensive and complicated, rocket vide the parameters desired are examined engine development problems have multiplied in terms of simulation capability, exhaust manyfold . handling requirements, and some of the requirements for test cell and specialized In the earlier days of rocket develop­ installation and instrumentation equipment . ment, it was reasonably possible to define Presentation includes environment required and correct the major problems by using for hybrid rocket systems as well as con­ sea-level condition test stands. Rocket ventional engines. Selected high-altitude chamber pressures were sufficiently high to tests of rocket engines and spacecraft and provide supersonic gas velocities at the spacecraft and missile subsystems which exit of the single, simple exhaust nozzle at have been conducted in recent months at the sea-level conditions, and the extrapolation Arnold Center are described. A forecast of of major performance from sea-level condi­ future test requirements is also included. tions to vacuum conditions was quite straightforward and reasonably accurate. As the missions have become more extensive, the INTRODUCTION systems associated with the upper ' stages and the space vehicles have become more compli­ The expansion of scientific activities cated. The present generation of space pro­ in the exploration and use of near and deep pulsion systems, such as the Apollo Service space has imposed a tremendous challenge to Module System, the Titan III Transtage , the designers and engineers. The pace at which Lunar Module Systems, the Surveyor, and the man can proceed to explore and safely Ranger, could not have been successfully endure the hostile environment of near and developed in a reasonable length of time deep space is, in a strong measure, depen­ without the use of vacuum test facilities . dent upon his ability to simulate the ex­ pected conditions in a laboratory and sub­ In general, the testing of components ject the equipment and various systems to and complete engines to define performance, tests closely approximating the mission durability and reliability at low pressure requirements . With the launching of man conditions is a routine employed by all in­ into space, the environments encountered in dustry. One additional major step has been space and the detailed control required to utilized in the Rocket Test Facility of the ensure the successful accomplishment of a Arnold Center. The installation of a com­ mission without loss of life impose a great plete £lightweight vehicle and the operation burden on the designers of the systems in­ of its propulsion systems under vacuum con­ volved. To accomplish the goal of provid­ ditions has been accomplished. The objec­ ing a suitable system without full use of tive of this approach is to determine the ground simulation facilities is not feasi­ adequacy of the integrated vehicle systems ble. to function through complete mission simula­ tion , including simulation of the coast Tremendous strides have been made in periods between the firing cycles and the the last half century in the maximum veloc­ mission profile . Although this is another ity and maximum altitude capabilities of step forward, it should not be considered propulsion systems. To a large degree , the the final step in the requirement to develop progress made in this area has been depend­ true space propulsion systems . ent on the ability to simulate the expected flight conditions in ground test facilities. Some of the major design and opera­ The complex process of simultaneously pro­ tional problems associated with facilities ducing maximum thermodynamic performance, for high altitude tests of rocket engines maximum structural performance, and maximum and propulsion systems are described in reliability in the rocket propulsion systems this paper . Solutions to many of these 1 The research reported in this paper was sponsored by Arnold Engineering Development Center, Air Force Systems Command, Arnold Air Force Station, Tennessee, under Contract No . AF 40(600)-1200 with ARO, Inc. Further reproduction is authorized to satisfy the needs of the U. S. Government. 2 Chief, Rocket Test Facility 14-17 problems have been incorporated in the less than 0.1 psia because the usable operational test units of the Rocket Test thrust increments even in vacuum condi­ Facility. A discussion of several selected tions are not sufficient to offset the programs recently completed in the Rocket weight and moment of inertia of the con­ Test Facility and a description of the taining nozzle walls. An order of magni­ various types of facilities used are in­ tude difference between exhaust nozzle exit cluded. pressure and test cell ambient pressure is adequate to provide accurate ballistic per­ MAJOR DESIGN AND OPERATIONAL PROBLEMS formance data. PRESSURE ALTITUDE, TEMPERATURE, AND VACUUM REQUIREMENTS Another area imposing design complica­ tions is the effect of exhaust gases on Pressure altitude is utilized to adjacent structures. This effect is pres­ define the ambient conditions for essen­ ent in all types of propulsion systems tially all rocket engine tests. During from reaction control systems to main stage launch, the decreasing ambient pressure is propulsion units. The absolute limiting the main influence causing a change in the altitude for tests designed to provide data operational condition of the rocket . systems. on the heating of adjacent surfaces is Variation of pressure is a function of pres­ entirely dependent on the geometric orien­ sure altitude within the range from sea­ tation of the engine with respect to the level to 200,000-ft pressure altitude. The structure and is also a strong function of normal area of interest for rocket propul­ the engine geometry and operating condi­ sion systems can be estimated rather close­ tions. In general, tests should be con­ ly by assuming an order of magnitude de­ ducted at actual operating altitudes at crease in pressure for each 50,000-ft in­ least up to a value which results in jet crease in altitude. For tests designed to impingement interactions that are strong determine the ballistic performance of enough to cause separation of the flow from rocket engines, a minimum altitude pressure the structure surf ace. of 0.01 psia or a maximum pressure altitude of about 175,000 ft is required. The environmental effects on the mate­ rial characteristics of epoxy-filled abla­ The simulation of background tempera­ tive engines, such as those currently in ture levels during engine operations may be use and under development, are basically of substantial importance for certain long-term effects and would be expected to engine configurations. For regeneratively occur during the extended orbital coast and ablatively cooled engines, the back­ periods and not during the short engine ground temperature levels during engine operating times. Typical earth orbit alti­ operation are not important as long as the tudes subject the vehicle to pressures of temperature level does not exceed approxi­ l0-10 mm Hg 0 during a mission. Such pres­ mately 600 or 700 R. On the other hand, sures are difficult to attain or even mea­ the background temperature levels may sig­ sure on a laboratory scale. Indications are nificantly affect the performance of that the areas of interest impose a vacuum radiation-cooled engine components. It is requirement in rocket tests down to pres­ generally presumed that dark space is an sure levels of l0-7 mm of Hg. infinite heat sink which behaves thermally as a blackbody at 7°R. It is shown in Ref. EJECTOR-DIFFUSERS 1 that a background temperature level of 180°R provides adequate simulation for To handle the large volume of gases material t·emper atures of 540°R and above. created during the combustion processes of rocket firings involves the utilization of Although the ambient pressure and back­ many techniques to provide the altitude ground temperatures are considered to be simulation capability in a test cell. The the primary environmental