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Lesson 9:

Solid RocketPropulsion

Basics

Dr. Andrew Ketsdever

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Solid Rocket Motors

A solid rocket motor is a sstem t!at uses solidpropellants to produce t!rust

Advanta"es

# $i"! t!rust# Simple

# Stora%ilit

# $i"! densit &sp

Disadvanta"es# Low &sp 'compared to li(uids)

# *omple+ t!rottlin"

# Di,,icult to stop and restart

# Sa,et

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Solid Rocket Motors

Solid rocket motors are used ,or

# Launc! ve!icles

$i"! t!rust '!i"! -/ ratio)

$i"! stora"e densit

# Ballistic Missiles

Propellant stora%ilit

0+cellent a"in" 1uick response

# stora%ilit

# !i"! -/ ratio)

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Solid Rocket Motor *omponents

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2!ermal &nsulation

Desi"n involves:#Analsis o, com%ustion c!am%er environment

Sta"nation temperature

Sta"nation pressure

Propellant "ases 'material compati%ilit)

# Selection o, insulation material

# Material t!ickness determination ,or various

areas o, t!e motor case# -or t!e clindrical part o, t!e case3 t!e wallsare onl e+posed to !ot com%ustion "ases att!e end o, t!e %urn

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2!e 4o55le

2!e desi"n o, t!e no55le ,ollows similarsteps as ,or ot!er t!ermodnamic rockets# 2!roat area determined % desired sta"nation

pressure and t!rust level

# 0+pansion ratio determined % am%ientpressure or pressure ran"e to allow ma+imume,,icienc

Ma6or di,,erence ,or solid propellantno55les is t!e tec!ni(ue used ,or coolin"#A%lation# -i%er rein,orced material used in and near t!e

no55le t!roat 'car%on3 "rap!ite3 silica3 p!enolic)

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A%lation

Meteorite# Re7entr speed o, 8 7 kmsec

# 0+treme !eatin" in t!e atmosp!ere

#A%lation and internal ener" modes cooled t!e

meteorite t!rou"! its ,all

A%lation "as cloud

Dissociation

&nternal ener" deposition

# Ston7&ron *lassi,ication

'9;< o, all meteorites)

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&"nition Sstem Lar"e solid motors tpicall use a t!ree7sta"e

i"nition sstem# &nitiator: Protec!nic element t!at converts electrical

impulse into a c!emical reaction 'primer)

# Booster c!ar"e

# Main c!ar"e: A c!ar"e 'usuall a small solid motor) t!at

i"nites t!e propellant "rain. Burns ,or tent!s o, a second

wit! a mass ,low a%out 88 o, t!e initial propellant "rain

mass ,low.

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Propellant =rain

2wo main cata"ories

# Dou%le Base: A !omo"eneous propellant

"rain3 usuall nitrocellulose dissolved in

nitro"lcerin. Bot! in"redients are e+plosiveand act as a com%ined ,uel3 o+idi5er and

%inder

# *omposite: A !etero"eneous propellant "rainwit! o+idi5er crstals and powdered ,uel !eld

to"et!er in a matri+ o, snt!etic ru%%er %inder.

Less !a5ardous to manu,acture and !andle

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*onventional *omposite

-uel# ;7< Powdered Aluminum

>+idi5er# ?;7@< Ammonium Perc!lorate '4$A*l>A or

AP)

Binder# 78< $dro+l7

2erminatedPol%utadiene '$2PB)

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-uels

Aluminum 'Al)# Molecular /ei"!t: ?.9 k"kmol

# Densit: @ k"mC

# Most commonl used Ma"nesium 'M")

# Molecular /ei"!t: .C k"kmol

# Densit: 8@; k"mC

# *lean %urnin" '"reen) Berllium 'Be)

# Molecular /ei"!t: 9.8 k"kmol

# Densit: C k"mC

# Most ener"etic3 %ut e+tremel to+ic e+!aust products

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>+idi5ers

Ammonium Perc!lorate 'AP)# Most commonl used

# *l com%inin" wit! $ can ,orm $*l

2o+ic

Depletion o, o5one

Ammonium 4itrate 'A4)

# 4e+t most commonl used# Less e+pensive t!an AP

# Less ener"etic

# 4o !a5ardous e+!aust products

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Binders

$dro+l 2erminated Pol%utadiene

'$2PB)

# Most commonl used

# *onsistenc o, tire ru%%er

Pol%utadiene Acrlonitrile

'PBA4) 4itrocellulose 'P4*)

# Dou%le %ase a"ent

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Additives

sed to promote

# *urin"

# 0n!anced %urn rate '$ME)# Bondin"

# Reduced radiation t!rou"!

t!e "rain 'darkenin")# Satis,actor a"in"

# Reduced crackin"