# Launch Performance Degradation of the Rupture-Type Missile Canister
## 1 Introduction  
A missile canister protects the missile from foreign matter inflow, shock vibration, and weather such as rain and snow, and facilitates smooth ejection at launch. The typically preferred canister cover is the rupture-type, which is easily manufactured and gives excellent handling convenience. However, if the missile canister cover fails to rupture at a missile launch, it could possibly interfere with the adjacent structure. The rupture-type canister cover is circular in shape and is installed with a sabot between the missile and canister to guide the missile during launch. The sabot is made of urethane foam and restrains displacement in the radial direction. Springs installed between the canister and missile are broken away with the missile, thrown out, and finally, they fall. The missile canister cover, which is also made of urethane foam, is ruptured by the propellant ignition impact pressure formed inside the missile canister and is removed. Cover remnant analysis: [PERSON], [PERSON] et al. [1] originally devised the rupture-type canister cover through their patent, confirming that the reliability of the cover opening would be increased by applying notches on the surface. [PERSON], [PERSON] et al. [2] performed the first structural analysis and validation test for the rupture-type canister cover. [PERSON], [PERSON] [3] demonstrated the mechanism for the cover to open by internal pressure propagation in the missile canister through computational fluid dynamics. [PERSON], [PERSON] et al. [4] described the behavior of the rupture-type cover opening through a comparison of a field test with a real rocket motor. However, the aforementioned studies did not recognize that cover remnants caused by improper manufacturing or insufficient internal pressure build-up may affect other components inside the canister owing to mutual collisions or contact with each other. Material deterioration analysis: with respect to the material deterioration of the urethane foam associated with the parametric study presented below, several foregoing studies are discussed. [PERSON] [5] demonstrated that the general form of the strain-stress curve for polymeric foam has both plateau anddensification processes, unlike metals. The report of the Argonne National Laboratory [6] states that the degradation of urethane foam may be related to the following causes: temperature effect, water immersion, biodegradation, and ultraviolet radiation. Among these, the temperature and radiation effects were believed to be the main contributors to the weakening strength and stress with long-term storage. At 90 \({}^{\circ}\)C, the compressive strength of the material dropped to half owing to the softening of the polymers and damage caused by radiation, which is believed to not be critical. Material property variation in high-speed analysis: the dynamic behavior of the material at high speed was investigated in several studies. In general, the Johnson-Cook constitutive model was introduced to reflect the strain rate effect on the strain-stress curve under a high-speed environment [7]. Problem statement: to quantitatively analyze the effect of the presence of remnants on the ejecting performance of the missile in terms of structure, we conducted an impact analysis based on a commercial finite element analysis (FEA) tool. In several field tests, we observed that cover debris may exist due to improper manufacturing and lack of ignition pressure, and there has been almost no consideration of a scenario where the cover debris is not entirely removed after ignition. In a certain flight test, the missile failed to launch as the ring structure of the canister interfered with the rear wing in the middle of lift-off. We hypothesized that the ring structure might be detached by a certain contact-induced force based on the cover debris. In this regard, we conducted an FEA-based impact analysis to quantitatively analyze the cause of the failed event.