Space Propulsion Flashcards
What are some (4) different energy sources of chemical space propulsion systems?
- Solid
- Liquid
- Hybrid
- Gel (in development)
What are some (3) different energy sources of electric space propulsion systems?
- Electro-static
- Electro-magnetic (in development)
- Electro-thermal
What are some (4) different energy sources of nuclear space propulsion systems?
- Solid-core (in development)
- Liquid-core (theoretical)
- Gas-core (theoretical)
- Radioisotope (in development)
What are some (5) different energy sources of non-chemical, non-electric and non-nuclear space propulsion systems?
- Cold gas
- Solar sail (in development)
- Photon (theoretical)
- Antimatter (theoretical)
- Beamed energy
What is the formula for thrust F?
F = mdot * ve + Ae * (pe - pa) = mdot * ce
(F is thrust, mdot is mass flow, ve is exhaust velocity, Ae is exhaust area, pe is exhaust pressure, pa is ambient pressure, ce is effective exhaust velocity)
How can thrust be obtained and which way is the more efficient?
- High mass flow
- High exhaust velocity
High exhaust velocity is more efficient as it means carrying the least amount of propellant possible
What is the formula for the specific impulse?
I = F/(mdot * g0) = ce/g0
(I is specific impulse, F is thrust, mdot is mass flow, ce is effective exhaust velocity, g0 is gravitational acceleration)
What are 7 propulsion types ordered by highest specific impulse?
- Electrostatic
- Electromagnetic
- Electrothermal
- Bipropellant
- Mono-propellant
- Solid propulsion
- Cold gas
What are 7 propulsion types ordered by highest thrust?
- Solid propulsion
- Bipropellant
- Mono-propellant
- Electromagnetic
- Cold gas
- Electrothermal
- Electrostatic
What are 5 important things to consider when choosing the propulsion system?
- Mission requirements
- Energy source, propellant and system
- Reliability and Flexibility
- Maximize performance for lowest cost
- Maximize thrust-weight ratio
What are the advantages (7) of solid propulsion systems?
- Few components
- High thrust
- Wide thrust range
- Variable thrust
- Storable
- High reliability
- Cheaper than liquid systems in production
What are the disadvantages (9) of solid propulsion systems?
- Few components
- One thrust profile
- Ignitable
- Non-extinguishable
- Not re-ignitable
- Need to be stored
- Not environmentally friendly
- Not reusable
- Compared to liquid propulsion lower performance
What are 10 applications of solid propulsion?
- Boosters
- Upper stages
- Stage separation
- Acceleration of upper stages
- Breaking
- Rescue capsules
- Small launchers
- Sounding rockets
- Roll acceleration
- Military applications
What are 5 components of a solid-based propulsion system?
- Motor casing
- Propellant block (combustion chamber)
- Isolation separating propellant block and casing
- Igniter
- Nozzle (and TVC, Thrust Vector Control)
What is a thrust profile and what are 3 properties of it?
A function of the propellant surface geometry and resulting regression rate. They can be:
- Regressive (Thrust lowers over time until depleting)
- Neutral (Thrust remains approximately constant over time until depleting)
- Progressive (Thrust rises over time until depleting)
What are 5 examples for neutral thrust profiles?
- Dogbone
- Slots and Tube
- Rod and tube
- Star
- Wagon Wheel
What is an example of a progressive thrust profile?
Internal burning tube
What is an example of a progressive-regressive thrust profile?
Multiperforated
What 6 factors does burn rate generally depend on?
- Nature of energetic material (ingredients and mixture ratio)
- Chemical composition (catalysts, modifiers, additives)
- Physical effects (particle size distribution, presence of wires or staples)
- Manufacturing process (in-place mandrel vs. plunged mandrel)
- Operating conditions (pressure, initial temperature, radiation, heat loss, acceleration)
- Mode of operation (steady vs. unsteady)
What are 9 important issues to consider for the choice of a specific propellant formulation?
- Burn rate r = a * pc^n
- Mechanical properties (temperature dependent, viscoelastic)
- Operational temperature range
- Hazard classification
- Aging
- Toxicity
- Throttling requirements
- Rheology / Processability
- Production cost
What are good mechanical properties in a propellant essential for?
- Low maintenance
- Storability
- Good aging characteristics
- Thermal cycling resistance
- Easy processing
- Good ballistic properties
- Reliability
What are the advantages (6) of liquid propulsion systems?
- Wide thrust range (1 micronewton to 8000 kilonewton) depending on cycle
- Variable thrust
- Can be designed to be re-ignitable
- Can be environmentally friendly
- Can be reused
- High performance
What are the disadvantages (3) of liquid propulsion systems?
- Depending on cycle and number of propellants a high number of components
- Depending on cycle can have long production times
- Complex in start-up and shut-down
What are the 4 main components of liquid rocket engines?
- Feed system
- Control
- Monitoring
- Thrust chamber
What are 4 important components of a thrust chamber in liquid rocket engines?
- Injection dome
- Buffer injection elements
- Injector elements
- Cooling channels
What are the advantages (3) of electric propulsion?
- Many applications
- High specific impulse, leading to reduced propulsion mass fraction and potentially lower launching cost
- Demonstration of orbital performance since more than 15 years
What are the disadvantages (2) of electric propulsion?
- Long timespan for orbit raising, leading to higher radiation exposure
- High power consumption
What are 3 examples of electrothermal propulsion systems?
- Arcjet
- Resistojet
- Microwave plasma
What are 2 examples of electromagnetic propulsion systems?
- Magnetoplasma
- Pulsed plasma
What are 4 examples of electrostatic propulsion systems?
- Grided ion
- Hall effect
- Field emission
- Colloid ion
What is the formula for conversion of electric work in kinetic energy?
P = 1/2 * mdot * ve^2
(P is power, mdot is mass flow, ve is exhaust velocity)
What is the formula for the maximum achievable thrust in electric propulsion?
Fmax = (2 * P)/ve
(Fmax is maximum thrust, P is power, ve is exhaust velocity)
What are the advantages (6) of hybrid propulsion systems?
- Inherent safety
- Throttling capability
- On demand termination
- Re-ignition
- Higher performance compared to solids
- Can be environmentally friendly
What is the disadvantage of hybrid propulsion systems?
- Lower performance than liquid propellants
What are the advantages (5) of gel propulsion systems?
- Non newtonian
- Can be designed to be re-ignitable
- Can be designed to be reusable
- Higher performance than solids
- Storable
What is the disadvantage of gel propulsion systems?
- Non newtonian
What is the general idea behind a nuclear thermal rocket engine?
- Continuous nuclear fission releases heat
- Propellant (e.g. hydrogen) is heated while cooling reactor fuel
- Heated propellant is expanded in a typical convergent divergent laval type nozzle
What is a drawback of nuclear thermal rocket engines?
A shield has to be installed to protect the spacecraft and possibly crew from radiation, which significantly increases the mass of the engine
What is the general idea behind a solid core reactor?
- Propellant cools chamber wall and radiation shield
- Propellant passes through reactor core and is heated by thermal energy
- Release of nuclear fuel
- Some hot gas is tapped off to drive the turbine
What are the advantages (2) of cold gas propulsion systems?
- Low complexity
- No hot components
What is the disadvantage of cold gas propulsion systems?
They have a lower specific impulse
What is the advantage of a solar sail?
- Simple, few components
What are the disadvantages (2) of a solar sail?
- Low thrust
- Distance to Sun is critical
What is the general idea behind a solar sail?
- Incoming solar rays are deflected and produce a resulting thrust
- Propulsion due to radiation pressure
- With total reflection: 6.7 mN of thrust per MW of influx
What is the general idea behind BEP (Beamed Energy Propulsion)?
Stationary energy source provides spacecraft carrying only propellant with energy via a beam station
What is the general idea behind the ablative plate principle (double pulse)?
- Laser pulse scatters particles from plate
- Particles spread
- Second laser pulse causes detonation of particle cloud
- Detonation wave propels plate
What is the general idea behind the concave mirror principle (single pulse, atmospheric)?
- Laser is focused by mirror and heats contained air
- Ejection of plasma
- Cavity is flooded by ambient air
What is the general idea behind the antimatter drive principle?
Annihilation of a proton and an antiproton releases high energy gamma radiation (A kg of matter with a kg of antimatter releases the same energy as 43 megatons of TNT)
Which 7 propulsion systems can be classified as thermal?
- Solid
- Liquid
- Hybrid
- Gel
- Electrothermal
- Solid-core
- Liquid-core
What is the formula for the mixture ratio Ro/f or MR?
MR = mdotox / mdotfu
What are the 3 assumptions we make for analysing an ideal thermal rocket?
- Adiabatic flow, 1D, steady state, frictionless
- Eventual solid or liquid phases of the exhaust are in thermal and kinetic equilibrium (homogeneous propellant composition)
- Thermally ideal gas with constant specific heat capacity cp (isentropic exponent = cp/cv = const.)
What is the definition of an isentropic process?
It is an idealised thermodynamic process that is both adiabatic and reversible. The work transfers of the system are frictionless, and there is no net transfer of heat or matter.
What is the definition of an adiabatic process?
It is a type of thermodynamic process that occurs
without transferring heat or mass between the thermodynamic system and its environment.
How do pressure, temperature, volume and Mach number change with respect to their position in a laval nozzle?
- Temperature is highest in the converging section and drops significantly in the throat, afterwards slowing its fall until the end
- Pressure is the highest in the converging section and drops significantly in the throat, afterwards slowing its fall until the end
- Volume is lowest in the converging section and rises sharply in the throat, afterwards slowing its ascend until the end
- Mach number is lower than 1 in the converging section, 1 at the throat and higher than 1 in the diverging section
What are the properties of a gas generator cycle?
- Open cycle (efficiency losses)
- More robust in terms of turbopump efficiencies leading to easier component design
- Can be implemented in wide chamber pressure ranges
- Any propellant possible
- Additional monopropellant used to drive the turbines in the beginning
What are 10 properties of liquid propellants?
- storable
- cryogenic
- hypergolic / non-hypergolic
- stable
- shock-resistant
- explosive
- corrosive
- toxic / environmentally friendly
- newtonian / non-Newtonian
- exotic (i.e, extremely expensive)
What are 9 favorable qualities of propellants?
- High energy content, high exhaust velocity
- High propellant density and low vapour pressure to reduce tank mass
- Good ignition properties and stable combustion
- Low viscosity to minimize pressure loss in pipings and cooling channels
- High specific heat capacity, high coefficient of thermal conductivity, high critical temperature for effective use in chamber cooling
- High chemical temperature stability (no or low coking) for effective use in chamber cooling
- Low trend of particle deposition in injector and chamber
- Low toxicity of all propellants as well as typical reaction products
- Good availability and low cost
What are advantages (3) and disadvantages (3) of a gas generator?
Advantages:
- Simple interface between combustion chamber and turbine
- Independent subsystem development possible
- Moderate pump discharge pressure
Disadvantages:
- Pulse loss due to gas generator
- Low turbine efficiency (minimisation of throughput)
- Additional power loss due to higher mixing ratio
What are advantages (3) and disadvantages (3) of an expander?
Advantages:
- Simple engine design
- Ignition of main combustion chamber only
- Low turbine inlet temperature
Disadvantages:
- Combustion chamber pressure < 100 bar
- Only integral development due to complex intersections between
turbo pump and combustion chamber
- High pump outlet pressure
What are advantages (3) and disadvantages (3) of staged combustion?
Advantages:
- High combustion chamber pressure possible without loss of specific impulse
- Compact turbine design
- No separate turbine outlet
Disadvantages:
- Only integral development due to complex intersections between
turbo pump and combustion chamber
- High pump outlet pressure
- Complex engine start
