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Space Propulsion and Power Systems > Electric Propulsion Systems > Flashcards

Electric Propulsion Systems Flashcards

Wada's stuff

1
Q

Orbit Achievement requirements

A

High Thrust, High efficiency, Low precision

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2
Q

Orbit adjustment requirements

A

High precision, efficiency not an issue

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3
Q

Disposal requirements

A

High Dormant reliability, High efficiency, low precision

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4
Q

Advantages of Electrical over Chemical propulsion?

A

Less propellant used
Higher efficiency
able to provide low thrust for a long period of ime

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5
Q

Three major categories of electric propulsion

A

Electrostatic
Electromagnetic
Electrothermal

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6
Q

Types of electrostatic propulsion

A 
Ion bombardment
Colloid Ion
Contact Ion
Field Emission
Microwave (radiofrequency) ion
Plasma seperator Ion
Radioisotopic Ion
Hall effect
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7
Q

Types of Electromagnetic propulsion

A 
MagnetoPlasmoDynamic
    -Steady state vs Quasi-steady state
    -Self-field vs applied field
Pulsed plasma
Helicon plasma
Inductive pulsed plasma
Electron-cyclotron resonance
Variable specific impulse plasma
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8
Q

Types of electrothermal

A 
Resistojet
Arcjet (Dc vs Ac vs Pulsed)
Electrothermal Hydrazine
Microwave Electrothermal
Pulsed Electrothermal
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9
Q

Characteristics of an Electric propulsion system

A

Typically uses much less propellant than chemical rockets due to a higher exhaust velocity
Due to limited momentum change the thrust is much weaker than chemical rockets (unsuitable for launch from earths surface)
Electric propulsion can provide a small thrust for a long period of time (ideal for deep space)

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10
Q

Why choose Electric propulsion?

A

Used in low-thrust manoeuvres
Attractive mass savings
Applications requiring high velocity increments
for N-S station keeping (50 m/s per year)
for orbit raising (1 to 5 km/s)
for orbit transfer from LEO to GEO (6km/s)
Attitude control in LEO

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11
Q

what is an ion

A

A charged atom or molecule

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12
Q

What is Ionisation

A

The process of electrically charging an atom or molecule by adding or removing electrons

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13
Q

What is Plasma?

A

An electrically neutral medium of unbound positive and negative particles

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14
Q

What is the net charge on a plasma?

A

roughly zero

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15
Q

Main principles of a Resistojet

A

Propellant is heated
Usually using an incandescent filament
Thermal Energy converted into Kinetic energy in nozzle with a high expansion ratio

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16
Q

Common propellants for a resistojet

A

Hydrogen, Helium, Water, Ammonia and Hydrazine

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17
Q

Principles of an Arcjet

A

Centrally located cathode surrounded by an anode, High voltage electric field is generated between them.

Propellant is injected between the two electrodes, passing through an arc and being electrically heated.

Hot gas is then accelerated through a nozzle thermodynamically

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18
Q

Arcjet Propellants

A

Hydrogen
Ammonia
Hydrazine

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19
Q

Hydrogen Considerations

A

Advantages
High specific heat and thermal conductivity
Disadvantages
Difficulty in storage
Suffers from Frozen Flow losses in Nozzle Expansion

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20
Q

Ammonia Considerations

A

Advantage
Liquid does not require refrigeration
Disadvantage
Heavy molecule which dissociates into low-molecular-mass constituents which introduces frozen flow losses

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21
Q

Hydrazine Considerations

A

Advantages:
Can be dual used for a combination propulsion system on satellites. Can be easily stored
Disadvantages
Chemical erosion problems are intensified at higher specific impulses. Heat transfer problems at the nozzle and chamber.

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22
Q

What is FAC?

A

Flow Accelerated Corrosion

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23
Q

What is MET?

A

Microwave Electrothermal

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24
Q

Principles of MET

A

Heat a propellant gas using a microwave-generated plasma

CD gas-dynamic nozzle expansion

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25
Q

How many electrodes does a MET use to generate plasma?

A

none; plasma generated without electrodes

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26
Q

What is Flemings left hand rule used for?

A

Electric motors

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27
Q

What is Flemings right hand rule used for?

A

Electric Generators

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28
Q

What does MPD stand for?

A

MagnetoPlasmoDynamic

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29
Q

Advantages of MPD?

A

Isp in the range of 1500-8000s
Efficiencies of 30-40%+
Exhaust Velocity beyond 110,000 m/s

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30
Q

MPD Issues?

A

Consumes a lot of power
High efficiencies (30+%) are only reached above 100kW
Cathode erosion
When operated below 200kW, the self induced magnetic field becomes insufficient; external field required

31
Q

what does VSIMR stand for?

A

Variable Specific Impulse Magnetoplasma Rocket

32
Q

How does VSIMR Work?

A

Helicon Antenna ionises gas to form plasma
Magnetic coils create a field to confine plasma
ICRH antenna heats plasma to millions of degrees
Magnetic Nozzle directs plasma flow, accelerates gas; converting Et to Ek.

33
Q

what does PPT stand for?

A

Pulsed Plasma Thruster

34
Q

How does PPT work?

A

Arc passes through fuel, causing ablation and sublimation.
Heat generated by arc converts gas from sublimation to plasma.
Plasma is propelled between cathode/anode
Lorentz force is exerted on the plasma, causing thrust

35
Q

What does PIT stand for?

A

Pulsed Inductive Thruster

36
Q

How does PIT work?

A

Uses a perpendicular Electric and Magnetic field to accelerated a propellant (Usually Ammonia or Argon)
PIT requires no electrodes

37
Q

What are the considerations in the Left hand rule and how are they oriented?

A

Thrust - thumb
Field - forefinger
Current - Second finger

38
Q

What are the considerations in the Right hand rule and how are they oriented?

A

Thrust - thumb
Field - forefinger
Current - Second finger

39
Q

What are the Left- and Right-hand rules applications of?

A

Lorentz force

40
Q

What is Electron Bombardment?

A

A process where neutral atoms are converted to positive ions by bombarding them with electrons.
Electrons are dislodged from the atoms by the fast moving injected electrons, forming ions.

41
Q

Types of solar sail

A

Square
Heligyro
Spinning disk sails

42
Q

Solar Concentrator operation principles

A

Parabolic Concentrator focuses the sun’s heat on to a receiver to heat a fluid/gas

Steam produced in a receiver drives a steam turbine (Rankine Cycle)

Heated gas drives a turbine (Brayton Cycle)

43
Q

What does DIPS stand for?

A

Dynamic Isotope Power Systems

44
Q

What does ORC stand for?

A

Organic Rankine Cycle

45
Q

Orbital considerations when using solar to power satellites?

A

Altitude, eccentricity, inclination, local time, durations of sunlit and eclipse phases

46
Q

What is PMAD?

A

Power Management and Distribution

47
Q

What are the 6 types of PMAD systems?

A 
Regulated bus (BR) with DET
Unregulated Bus (BU) with DET
Semi-regulated bus (BS) with DET
Regulated bus (BR) with MPPT
Unregulated bus (BU) with MPPT
Hybrid bus (BH) with DET
48
Q

What is DET?

A

Direct Energy Transfer

49
Q

What is SR? What does it do?

A

Shunt Regulation, Bleeds of excess power

50
Q

What is MPPT? What does it do?

A

Maximum Power Point Tracking. Extracts the appropriate SA power to maximum

51
Q

What is SA?

A

Solar Array

52
Q

Which processes are responsible for the generation of power in a solar array?

A

Absorption of solar radiation, generating electron-hole pairs

The separation of the electrons and holes across a semiconductor junction, thus generating an EMF.

53
Q

Short circuit current parameters

A

V=0, R=0;

54
Q

Open circuit voltage parameters, Voc

A

I=0, R=inf

55
Q

Maximum power point current parameter, Imp

A

Current at maximum solar cell output

56
Q

Maximum Power point voltage

A

Vmp

57
Q

Fill Factor

A

(IscVoc)/(ImpVmp)

58
Q

Silicon Solar cells

A

convert the visible solar spectrum into electrical power

59
Q

Which bands are TJ-GAS sensitive to?

A

Infrared and UV

60
Q

Power storage types

A

Battery
flywheels
regenerative fuel cells

61
Q

Main tasks for satellite propulsion systems, plus thrust levels and propulsion method

A

Apogee injection - Bipropellant, 400-600N
Orbit control - mono/bi propellant, 10-22N
Attitude control, Mono/bi prop, 1-22N
Additional tasks; Electric, millinewtons-1N

62
Q

What is Isp?

A

Propellant efficiency or thrust/mass rate

63
Q

What is electromagnetic propulsion?

A

The principle of accelerating an object by the utilisation of a flowing electrical current and magnetic field

64
Q

Briefly describe Lorentz force in terms of the combination of
electric force and magnetic force

A

A Lorentz force pushes the
conductor in a direction perpendicular to the conductor and
the magnetic field
(It is the combination of electric and magnetic force on a point
charge due to electromagnetic fields)

65
Q

How can you reduce the cathode erosion problem in an MPD thruster?

A

Use multichannel hollow cathode and lithium propellant

66
Q

How does electromagnetic propulsion (EMP) differ from

electrothermal propulsion system?

A

EMP uses magnetic and electric fields to accelerate an object, ETP uses purely thermodynamic effects.

67
Q

How do you calculate the Electrostatic force?

A

abs(F)=Ke*(Q1Q2)/r^2

where Ek is coulombs constant, Q1 and Q2 are the charges and r is the distance between them

68
Q

What is a solar sail?

A

A form of space propulsion which uses radiation pressure on large, ultra-thin mirrors to accelerate to high velocities.

69
Q

Working principle of a solar sail?

A

Solar radiation exerts a pressure on the sail due to reflection

70
Q

What 6 components make up the EPS block diagram?

A 
Primary power source, Power conditioning,
Energy storage
Charge/discharge control
Power distribution
Power consumer
71
Q

3 types of Hall thruster

A

Stationary Plasma Thruster (SPT)
Thruster with Anode layer (TAL)
Cylindrical Hall thruster (CHT)

72
Q

Advantages/Disadvantages of using a Nuclear Thermoelectric device?

A

Advantage:
No power storage required as constant power generation
Disadvantage: requires lots of shielding, dangerous.

73
Q

Other requirements for EPS design

A

Achieve low cost recurring cost for flight components
Utilisation of flight-proven components
Redundancy concepts
Functional and human-safety related requirements
Facilitation of an architecture with growth potential
Design which can be tested under flight-representative conditions
increased hardness against space radiation

74
Q

Advantages and Disadvantages of BCR and BDR

A

Advantages:
Simplified thermal design
Good electromagnetic compatibility
Disadvantages:
Increased weight from BCR and BCD
More SA power required due to losses in BCR and BCD
Higher control loop effort for bus voltage regulation

Space Propulsion and Power Systems (2 decks)

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