It provides and is operably secured to liquid rocket thrust chamber head including auto-injection syringe injection and retraction assemblies. Retraction assemblies include that hypodermic needle has hub, there is end cap a part of sealing element to pass through hypodermic needle, it can be arranged between needle hub and end cap by retracting spring and be maintained between some compression, on seal against the retraction assemblies facial sealing surface power spring needle hub, so that sealing element sealing in upper and lower part is defined, the outside of the pressure balanced sealing area between air-breather and sealing area and retraction assemblies.
