Closely Spaced Modes Of Launch Vehicle And Isolation From Its Engine

With the application of new high-thrust engines, the mechanical environment of launch vehicles continues to deteriorate, so effectively isolating the transmission of vibration from the engine to the satellite and other equipments becomes a big problem. This paper uses Patran software to model the launch vehicle and uses Nastran software to do the post-Processing. We use the traditional multi-branch beam modeling in order to reduce unnecessary mode calculations. Because beam model simplifies the physical structure much larger, according to the physical structure of launch vehicles, here establishes a three-dimensional model in order to check the established beam model. It's calculated that the maximum error of the beam model's natural frequencies is 6%, so we can simulate the real structure of the launch vehicle very good.By calculating, we find the modal of carrier rockets is intensive and it isn't suitable for active vibration isolation, so here on the use of passive methods, we use metal rubber pad to isolate the rocket engine .Here the parameterized PCL language is used to model, by the Visual C + + software's auxiliary programming, to realize parameters 'visual change and the batch of the modal and the transmission rate. Finally, analyze and calculate the large number of parameters' results to determine that the parameters of metal rubber have effect on carrier's frequency and transmission rate.This paper mainly studies that the metal rubber pad's height and cross-sectional area have effect on the effect of the metal rubber's vibration isolation. With the increase of its height or area, the vibration isolation effect of the metal rubber is getting better and better, but effect's change gradually slows down. When each engine's metal rubber is 0.1m height and its cross-sectional area is 0.6m~2 , its transmission rate can be reduced about 50%, isolation effect can be very good.