Mechanical Systems Flashcards
What constraints does the launch vehicle place on the spacecraft design?
Mass and volume restrictions as well as style of attachment fitting which is usually a truncated cone
Describe the arrangement for the three and five fixing points in the STS space shuttle
5 point: 4 placed in a rectangular arrangement in the plane of the walls, another placed in the floor
3 point: the same as 5 but with 2 points in the rectangle removed
What are the two main design differences between a typical spin-stabilised and a three-axis stablised spacecraft?
Spin-stabilised has shelf-mounted equipment, and the thruster is in the shape of a cone
three-axis stabilised has panel mounted equipment and a cylindrical shaped thruster
Define Ultimate Tensile Strength
the maximum stress a material can withstand before breaking when stretched or pulled
Define Ultimate Tensile Stress
the maximum stress a material can withstand before breaking when stretched or pulled
Define ductile and brittle
Ductile: able to be deformed without losing toughness; pliable, not brittle.
Brittle: Not able to be deformed without breaking
Define Specific Strength and the units
It is the stress per unit mass, found from dividing the UT strength by the density of the material with units of [Nmkg-1]
Define proof load
the maximum amount of force that a material or fastener can withstand without permanently deforming
Define Specific Stiffness (aka specific modulus)
It is the stiffness per unit mass, found from dividing the UT stiffness by the density of the material with units of [Nmkg-1]
define compliance
The material’s compliance is the inverse of the material’s stiffness
define elastic limit
the point where young’s modulus goes non-linear on the stress over strain plot and the material suffers permanent deformation
Define yield stress
the minimum amount of stress required to cause a material to deform permanently, or plastically, without a significant increase in the applied force
Define rigidity
it is the same as stiffness i.e. it is the extending force divided by the material extension
