Structures

Question 1

Storage Loads Characteristics (3):

Answer 1

• 1 g
• “Aggressive” atmosphere - leads to corrosion
• Sustained tensile loads

Question 2

Launch: Quasi-static Characteristics (3):

Answer 2

• Launch propulsion results in increasing acceleration
• Strongest at transonic buffeting or stage separation
• Felt ‘uniformly’ by entire S/C (-5.5 g, 2.5g)

Question 3

Launch: Sine vibration Characteristics (3):

Answer 3

• Low-frequency transient vibrations
• ‘Shaker’ test (5Hz - 100 Hz)
• Check for resonances -> amplification -> damage

Question 4

Launch: Acoustic Random Vibration Characteristics (2):

Answer 4

• In lift-off, sound reflected from the ground

- Structural response is predicted in terms of random vibration

Question 5

Primary Structural Loads: (3)

Answer 5

1) Storage:
- Atmosphere aggresive -> corrosion

2) Launch:
- Quasi-static
- Shock
- Sine Vibration
- Acoustic Loads

3) In-space Loads:
- Orbit Maneuvers
- Thermal Expansion
- Assembly stress (holding components together)

Question 6

Types of structures: (3)

Answer 6

1) Primary:
- Withstand the most significant launch loads

2) Secondary:
- Antennas
- Deployment systems
- Withstand medium loads

3) Tertiary:
- Clamping components
- Cases/Housing of subsystems
- Mounting structures

Question 7

Mention at least 4 (of 7) Primary Structure design characteristics:

Answer 7

1. Carries the satellite’s own weight
2. Ensures proper load path from satellite to launcher
3. Allows mechanical interface between Sat. and launcher
4. Stiff enough to deal with critical eigenfrequencies
5. Material with good thermal & electrical properties
6. Easy access to components
7. Proper alignment of components even under extreme temperature conditions

Question 8

Launch: Shock Characteristics (4):

Answer 8

• Seen during stage separation, docking
• High Frequency, large accelerations
• Problem for equipment more than structural
• Attenuated quickly in structure and joints

Question 9

The Primary Structure is defined by (3):

Answer 9

1) Architecture
2) Type of structure
3) Type of packing

Question 10

In Primary Structure, Architecture refers to these characteristics (3):

Answer 10

1) Cross-section of the satellite (hex, octa, cross, etc)
2) Shape of the satellite body
3) Open or closed architecture (i.e body)

Question 11

In Primary Structure, the basic Type of Structures are (6):

Answer 11

1) Monocoque cylinder
2) Lead Frame
3) Lattice Frame
4) Stiffened Shell Frame
5) Sandwich Structure
6) Isogrid Structure

Question 12

In Primary Structure, Type of Packing should have these characteristics (7):

Answer 12

1) Lightweight
2) High Pack Density
3) Favorable load path to structure
4) Favorable thermal conditions
5) No impact in neighboring systems
6) Easy Access
7) Cheap to manufacture

Question 13

Type of Packing Characteristics: Panel Mounting (3)

Answer 13

• Components are mounted in housing panels
• Allows easy access and favorable
• Low Packing density

Question 14

Type of Packing Characteristics: Deck Mounting (4)

Answer 14

• Components are mounted in internal panels
• Higher Pack Density
• Unfavorable component access
• Poor Heat Transport

Question 15

Type of Packing Characteristics: Slot configuration (4)

Answer 15

• Components are designed as slide-in modules
• Very High Pack Density
• Mostly Favorable access to component
• Poor Heat Transport

Question 16

Criteria for structure materials - Material Properties (9)

Answer 16

• Specific strength
• Specific stiffness
• Stress corrosion cracking resistance (SCC)
• Fracture and fatigue resistance
• Thermal expansion coefficient and conductivity
• Density
• Corrosion sensitivity (e.g. radical oxygen)
• UV resistivity
• Radiation sensitivity

Question 17

Major Selection Criteria for Materials (3):

Answer 17

1) Loads and Load Response
2) Flight Proven (ESA & NASA Standards)
3) Cost