Research On The Aging Performance Of Htpb Propellant Under Vacuum High-low Temperature Cycling Temperature Conditions

With the development of Micro-Nano satellite technology,the solid rocket thrust has a wide range of application prospects in the field of rapid mobility due to its advantages of simple structure,high work reliability and rapid work.However,in a spatial complex environment,there is an insufficient study of the structure and pharmaceutical column integrity,propellant preparation,and service life in the thrust system,and space aging is one of the key factors affecting the development of the thrust.Therefore,the aging properties of HTPB(terminal hydroxyl polybutadiene)propellant at a vacuum high and low temperature cycle is carried out,and the spatial aging and space storage life of the propellant is obtained,which is important guiding significance for the development and preparation of the thrust structure and the integrity design of the pharmaceutical column in the space environment.In this paper,HTPB propellant is used as the research object,the aging test systems are built and the aging performance law of different pre-response HTPB propellants in vacuum high and low temperature cycle temperature is analyzed.Compared with the normal pressure,vacuum aging mechanism is gained and the storage life of the propellant is predictive.Meanwhile it showed that the physical damage and the material strength should be reduced during the development of the propulgent,and control the size of the AP particles(ammonium oricate),which can be improved the performance of the space solid thrust.The main research work of this paper includes:(1)The aging performance of propellant in atmospheric high-low temperature cycling temperature environment is researched.The study shouwed that during the normal cycling aging,the propellant undergoes thermal decomposition reactions,oxidative cross-linking reactions,‘post-curing’ reactions,and degradation chain scission reactions,among which the effect of degradation chain scission reaction is more obvious.On the whole,the strength and initial modulus of the propellant showed a downward trendand the elongation showed an upward trend with the increase of aging time.The propellant becomes hard in the early stage of aging and soft in the later stage of aging.In addition,the studies have found that physical injury caused by the temperature cycling and AP particle decomposition led to the "dehogin" of the propellant,caused damage to the bonding properties of the adhesive,and accelerated the aging rate of the propellant.(2)The aging performance of the propellant under different pre-strains in the vacuum highlow temperature cycling temperature condtions is researched.The study showed that the chemical reaction in the vacuum aging process is the same as that of atmospheric cyclic aging,but the effect of the oxidation cross-linking reaction is more obvious.In the early stage of aging,the mechanical properties of the propellant are mainly composed of the "post-curing" reaction and the degradation chain scission reaction.In the middle and later stages of aging,the mechanical properties are more obviously affected by oxidative cross-linking.The study also found that the moisture absorption properties of the OA particles in the propellant are suppressed,which improves the vacuum aging performance.there is a "hysteresis" phenomenon in the maximum elongation of the propellant,that is,the response rate of the propellant’s tensile strength affected by chemical aging is faster than the maximum elongation.During the entire aging period,the "dewetting" phenomenon of the propellant under vacuum is mainly caused by physical damage(attribute to the the temperature cycling and pre-strains),AP particle decomposition,and the strength of the material itself.(3)The storage life estimation of propellants is carried out.Based on the law of the maximum elongation in the normal pressure,the linear aging mathematical model is established;Based on the law of vacuum aging performance,the aging performance and the aging time were changed.Then,the piecewise function aging mathematical model was established,and the storage life of the propellant is estimated.The result shows that the storage life of the propellant under atmospheric high-low temperature cycling environment conditions is about 5.0 years,and its aging rate is 4 times the constant temperature aging rate at 25°C(calculated based on the storage life of 20 years);Under vacuum high-low temperature cycling environment,the storage life of 0% pre-strained propellant is 3.5 years to 6.1 years,the storage life of 5% prestrained propellant is 2.5 years to 3.5years,and the storage life of 9% pre-strained propellant is1.4years to 3.7 years.From the above,the storage life is low in the cycle temperature environment,in the existing preparation technique.Combined with normal pressure and vacuum aging conclusions,the pre-stress of the propellant should be reduced as much as possible,the size and shape of the AP particles should be controled,and the initial strength of the propellant should be appropriately reduced,in order to actively reduce the operating temperature fluctuation of the thruster,to improve the aging performance of the propellant and enhance the life of the solid rocket thruster.