Rocket Design - Fundamentals of Rocket Theory

total impulse

defined as the thrust force F over the operating duration, or the "burning time" t of the motor engine

specific impulse

the total impulse per unit weight of the propellant

effective exhaust velocity

the average equivalent velocity at which propellant is ejected from the vehicle

final mass

the mass of the vehicle after the rocket has ceased to operate when all the useful propellant mass has been consumed and ejected; includes all components that are not useful propellant and may include payload

propellant mass fraction

indicates fraction of propellant mass in an initial mass

thrust to weight ratio

expresses the acceleration that the engine is capable of giving to its own loaded propulsion system mass

momentum

a vector quantity defined as the product of mass and velocity

characteristic velocity

used in comparing the relative performance of different chemical rocket propulsion system designs and propellants

nozzle

it produces thrust

exhaust gases

they are pushed from combustion into the throat region of the nozzle

throat

has a smaller cross-sectional area than the rest of the engine, gases are compressed to high pressure

conical nozzle

oldest and the simplest configuration; easy to fabricate; the walls of the nozzle diverge at a constant angle

bell/contoured nozzle

similar but more efficient to conical design; more compact, most commonly used nozzle shape today; minimizes the turning divergence losses

annular nozzle

a.k.a. the plug or altitude compensating nozzle; least employed due to greater complexity; combustion occurs along a ring or "annulus"

"plug" refers to the center body that blocks the flow from what would be the center portion of a traditional nozzle

radial out flow nozzles

E-D, R-F, H-F nozzles

expansion-deflection nozzle

works similar to a bell nozzle; exhaust gases are forced into a converging throat region of low area before expanding in a bell-shaped nozzle. BUT flow is deflected by a plug

reverse-flow nozzle

the fuel is injected from underneath, but the exhaust gases are rotated 180º thereby reversing their direction

horizontal-flow nozzle

the fuel is injected sideways, but the exhaust is rotated 90º

radial in flow nozzles

spike, truncated aerospike nozzle

spike nozzle

named for the prominent spike center body; also described as a bell turned inside out

truncated aerospike nozzle

removed pointed spike altogether and replace with a flat base; will have some internal supersonic waves and will show a small but real loss in thrust compared to a nozzle with a full central spike