A rocket–ramjet combined cycle engine model, embedding twin rocket chambers driven with gaseous hydrogen and oxygen on the top wall side of a scramjet flowpath, was tested in its ejector-mode operation under sea-level static conditions. Gaseous hydrogen was also injected through secondary injector orifices to pressurize a ramjet combustor located downstream of the rocket chambers. Mixing between the hot rocket plume and cold airflow as well as combustion of residual fuel within the plume with the airflow caused entropy and static pressure increases in the constant-area mixing duct in the original flowpath design, resulting in a limited airflow rate. The mixing duct was redesigned to incorporate divergence from its onset to counter the pressure rise. With the diverging flowpath configuration, the airflow rate was increased by 40 percent. However, this modified flowpath geometry resulted in the formation of a low-speed area, through which the pressure rise in the ramjet combustor penetrated the mixing duct and reduced the incoming airflow rate. Without mechanical contraction near the engine exit, increasing pressure in the diverging portion of the flowpath was difficult, which in turn, resulted in poor mixing between the airflow and the rocket plume. Balancing these factors and additional mixing enhancement are required. The engine performance is then summarized.

火箭-冲压喷气发动机联合循环发动机模型在海平面静态条件下以喷射器模式进行了测试，该模型在超燃冲压流路的顶壁侧嵌入了由气态氢和氧驱动的双火箭舱。气态氢也通过辅助喷孔喷出，以加压位于火箭室下游的冲压喷气发动机燃烧室。在原始流路设计中，恒定面积混合管道中的热火箭羽流和冷气流之间的混合以及羽流中残留燃料的燃烧与气流引起熵和静压增加，从而导致有限的气流速率。混合管道经过重新设计，从一开始就考虑了分歧，以应对压力上升。通过不同的流路配置，气流速率增加了40％。然而，这种经过修改的流路几何形状导致形成低速区域，冲压喷气机燃烧室中的压力上升通过该低速区域穿透混合管道并降低了进入的空气流量。在发动机出口附近没有机械收缩的情况下，很难在流路的发散部分增加压力，这又导致气流与火箭羽流之间的混合不良。需要平衡这些因素并增强混合效果。然后总结了发动机性能。反过来，导致气流与火箭羽流之间的混合不良。需要平衡这些因素并增强混合效果。然后总结了发动机性能。反过来，导致气流与火箭羽流之间的混合不良。需要平衡这些因素并增强混合效果。然后总结了发动机性能。