A rotationally skew fold membrane for the spinning solar sail is discussed to examine the deployment characteristics. The membrane is characterized by double corrugation fold and is advantageous in the complete folding and compact storage. Spinning experiments with scaled models are performed to investigate the geometrical and deployment characteristics. As the result of the spinning experiments, it is indicated that the rotationally skew fold membrane is completely deployed and there is a minimum spin rate to complately deploy. The fact that the spin-direction wrapped membrane realizes quick deployment is also indicated. To investigate the dynamic characteristics, a non-dimensional similarity parameter derived with the theoretical analysis for one-dimensional Z-fold membrane is expressed by the geometrical parameters as the radius, folding pitch, material properties and spin rate. The theoretical similarity parameter is applied to the results of the spinning experiments and indicates the effect of the folding pitch of the rotationally skew fold membrane. Also the similarity parameter based on the experimental results is introduced.

The inner liner of a combustion chamber of a cryogenic liquid rocket engine is exposed to a high load induced by the high temperature of the hot gas and the low temperature of the coolant. The high load causes some inelastic strain that accumulates with each operational cycle until the fracture or rupture of the inner liner. A model that can reproduce the propagation of damage under a thermally cycled load is essential for precisely predicting the chamber life. However, the damage propagation phenomenon or the quantitative value of the damage was so far not fully discussed using the damage data obtained from basic testing of a rocket chamber material. The purpose of the present study was to investigate a precise prediction model based on damage mechanics for simulating the damage propagation of a rocket chamber material. In this study, low cycle fatigue test data at a high temperature (900 K) were analyzed, and damage models that could reproduce the damage propagation under cyclic load conditions were investigated. Then the parameters were identified to reproduce uniaxial test data. These damage models were also subject to a finite element method analysis of a thermomechanical fatigue panel test in order to quantitatively evaluate the deformation, damage propagation, and life of a chamber wall. The analysis of low cycle fatigue test data at 900 K suggested a specific model that could precisely reproduce the damage propagation phenomenon and the basic material test data. From the results, it was confirmed that the model could predict the location of crack initiation.

Stress corrosion cracking (SCC) growth tests were conducted on type 316L stainless steels (SS) with different cold rolling reductions of 10 to 40 under a simulated boiling water reactor coolant condition. In these tests, constant loads were applied to each compact tension(1 T CT) specimen to maintain the initial stress intensity factors(K) to 20 MPa m or 30 MPa m. The crack growth rate increased with increasing the micro-Vickers hardness(Hv) and was larger than the tentative criterion of SCC growth rate for work hardened L grade SS proposed by Kumagai, et al. at Hv 250. However, the crack morphology of specimens with high cold rolling reductions(Hv 250) was quite different form that observed in the actual components. Only a 10 cold rolled specimen with Hv230 showed intergranular cracking, the same cracking morphology as that in the heat affected zone of the damaged shrouds. This result would suggest that the heavily cold rolled specimens with Hv 250 should not be used to obtain the crack growth data for prediction of SCC propagation behavior in the actual components because of the different crack morphology.

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