Power Control Flashcards
Describe three main elements that the spacecraft electric power system and the main functions of each element.
1) Primary energy source: converts fuel or solar energy into electric power
2) Secondary energy source: stores and subsequently delivers electric power to the satellite system and payload, when the primary system’s energy is not
available.
3) Power control/distribution network: delivers to all appropriate voltage-current levels to all spacecraft loads when required.
List the types of primary energy sources used in a satellite.
Main primary electric energy sources are
1 Solar arrays:
2. Solar heat systems:
3. Nuclear fission systems:
4. Radioisotope thermoelectric generators (RTG):
5. Electrochemical batteries:
6. Fuel cells:
Describe their advantages and drawbacks and missions in which they are mainly used.
solar arrays
i. Solar arrays: are used in majority of modern satellites.
They do not need fuel and can supply by energy for a many years missions.
They need a large area (and mass) of the arrays to provide a significant amount of power. They are vulnerable for radiation damaged and have relatively low efficiency.
Describe their advantages and drawbacks and missions in which they are mainly used.
fuel cells
ii. Fuel cells: are used mainly in manned spacecrafts in few days/weeks missions.
They can provide a significant amount of power but they consume fuel.
Describe their advantages and
drawbacks and missions in which they are mainly used.
radioisotope thermoelectric generators
iii. Radioisotope thermoelectric generators (RTG):
long lifespan, high energy density.
they adversely affect radiation of the satellite whilst in orbit. Also high temperature operation is required for efficient energy conversion. This impacts upon the thermal environment of the satellite.
Describe their advantages and
drawbacks and missions in which they are mainly used.
solar heat systems
iv. Solar heat systems: have higher efficiency then solar cell arrays.
Are under development for the International Space Station (ISS).
Describe their advantages and
drawbacks and missions in which they are mainly used.
nuclear fission systems
v. Nuclear fission systems:
high energy density
can damage the environment.
They were used in Soviet military satellites. But are considered to be used on the ISS.
Describe their advantages and
drawbacks and missions in which they are mainly used.
electro chemical batteries
vi. Electrochemical batteries:
adequate lifetime
require charging
were used in very early missions as a primary source.
Also they are often used in planet landing modules.
Describe design of Radioisotope thermoelectric generator (RTG),In which mission it is preferable power source?
long-duration, deep space exploration and long-term satellite operations.
thermal source
anode & cathode
thermal sink
List the types of secondary electric power sources used in a satellite. At which phases of the
spacecraft mission such the power sources are necessary?
i. Electrochemical battery
ii. Regenerative fuel cell
when primary cannot be used eg eclipse
