Questions -
1. A particular rod for the structure of a spacecraft must be able to withstand an applied force, but still function properly. Compare the properties of aluminum 7075-T6 and AISI 1015 steel to decide which is best for the problem described below. The dimensions of the rod are as follows: volume of 10 m3, cross-sectional area of 0.1 m2, factor of safety of 2, and a σmax of 150 MPa. The physical properties of the aluminum 7075-T6 are: σyield of 505 MPa and density, ρ, equal to 2810 kg/m3; and the properties of AISI 1015 steel are σyield of 315 MPa and density, ρ, equal to 7870 kg/m3.
2. Imagine a spacecraft outer shell can be modeled as a thrust cylinder with a radius of 35 cm and a height of 50 cm. The thrust cylinder must be strong enough to support the axial load placed on it by launch without either failing in compression or by buckling. Assume the maximum load on the shell is the thrust of the boost motor, 50kN. Determine the thickness of the shell required to support this load, also determine it's mass. State any assumptions or load factors you use.
3. Rocket motor casings may be fabricated from either of two steels :
(a) low alloy steel yield 1.2 GPa toughness 70 MPa √m,
(b) maraging steel yield 1.8 GPa toughness 50 MPa √m
The relevant Code specifies a design stress of yield/1.5.
Calculate the minimum defect size which will lead to brittle fracture in service for each material, and comment on the result.
4. Conduct a trade study to look at what type of structure and what material should be used for the main shell (thrust cylinder) for a 2500 kg communications satellite to be launched on a vehicle with a similar launch load environment to the space shuttle. Assume you have a typical mass budget for this structural element (12% of total spacecraft mass).
5. You are the structural engineer for the new GPS payload for the GPS gen III spacecraft, designed to be launched on the Delta series of launch vehicles. Your payload has a mass of 75 kg. It will be mounted in the spacecraft on a plate. Assume damping ratio is 0.05. What plate bending stiffness is needed to allow a safe natural frequency for the payload using the Delta launch vehicles? Obtain the power spectral density for a Delta IV launch vehicle and determine rms response for your design.