niklas wingborg foi, energetic materials

SWEDISH DEFENCE RESEARCH AGENCY

Niklas Wingborg2007

Niklas Wingborg

FOI, Energetic materials

Chemical Rockets

Performance and propellants


Niklas Wingborg2007

Principle of rocket engines

mVF e FtI

Combustion chamber Nozzle

Throat Exit

mFmFtI psp //


Niklas Wingborg2007

Principle of rocket engines

De Laval nozzle

M<1 M=1 M>1

Tc Tt<Tc Te<Tt


Niklas Wingborg2007

Gustav de Laval, 1845-1913

1883 AB Separator → Alfa Laval

1893 AB de Lavals Ångturbin → Stal-Laval AB → ALSTOM Sverige AB


Niklas Wingborg2007

Rocket propellant classification

Propellant = fuel + oxidizer

Liquid propellants

– Bipropellant (storable, non-storable, hypergol)

– Monopropellant

Solid propellants

Fuel + oxidizer gas + energy


Niklas Wingborg2007

Propulsion systems in the Ariane 5

Cryogenic main core stage

Vulcain engine

Upper stage with storable propellants and Aestus engine

Solid propellant booster


Niklas Wingborg2007

Propellant performnace

Propellant content: up to 90%

Not unusual with 50%

The performance of the propellant very important

Propellant figure of merit: Specific impulse, Isp

Isp unit: Ns/kg, m/s or s

m

F

m

FtI

psp


Niklas Wingborg2007

Specific impulse, Isp

Optimum mixture oxidizer/fuel high Tc

High heat of formation, ΔHf high Tc

High hydrogen content low M

M

TI csp

CO2 44 g/mol

CO 28 g/mol

N2 28 g/mol

H2O 18 g/mol

H2 2 g/mol


Niklas Wingborg2007

Calculation of specific impulse

Nozzle/chamber

– Pressure in combustion chamber, pc

– Nozzle expansion– Pressure ratio: pc/pe

– Area ratio: Ae/At

– Chemical equilibrium or frozen equilibrium

Propellant

– Chemical composition of fuel and oxidizer

– Heat of formation of fuel and oxidizer

– Mixing ratio fuel/oxidizer


Niklas Wingborg2007

Thermochemical computation

Computer programs for calculation of thermochemical equilibrium and Isp

NASA CEA (chemical equilibrium with applications)

– NASA Reference Publication 1311 (June 1996)

Equation of state: ideal

Chemical equilibrium minimizing ΔG = ΔH-TΔS

CEA can be obtained for free

– http://www.grc.nasa.gov/WWW/CEAWeb/

– http://www.openchannelsoftware.com/projects/CEA


Niklas Wingborg2007


Niklas Wingborg2007

Liquid rocket propellants


Niklas Wingborg2007

Common liquid rocket propellants

Oxidizers

– Liquid oxygen, O2

– Dinitrogen tetroxide, N2O4

– Nitric acid, HNO3

– Hydrogen Peroxide, H2O2

Fuels

– Liquid hydrogen, H2

– Hydrazine, N2H4

– Monomethylhydrazine– Methane– Unsymetrical dimethylhydrazine– Kerosene– Ethanol


Niklas Wingborg2007

Liquid oxygen (LOX), O2

Non storable oxidizer

Nontoxic

Mp= -219oC, Bp = -183oC

Used in combination with H2, kerosene, ethanol

Density = 1.14 g/cm3


Niklas Wingborg2007

Dinitrogen tetroxide (NTO), N2O4

Widely used storable oxidizer

Different percentages (1-3%) of nitric oxide, NO, added as stress corrosion inhibitor (MON-1 and MON-3)

MON-1 and MON-3 are used more often than pure NTO

Bp= 21°C, Mp=-11°C, dens=1.43 g/cm3


Niklas Wingborg2007

Dinitrogen tetroxide (NTO), N2O4

Safety concerns

Concern about reactivity of MON with titanium alloys, ignition by friction on freshly formed surfaces (e.g., pyrovalves).

History of accidents

Toxicity of vapor clouds in case of launch mishaps

State governments impose restrictions on transportation of NTO/MON

Space agencies have considered manufacturing NTO (and other toxic fuels) at the launch site to alleviate transportation restrictions


Niklas Wingborg2007

Liquid hydrogen, H2

Non storable cryogenic fuel, Mp= -259oC, Bp = -253oC

Used in combination with LOX

Density = 0.07 g/cm3 bulky fuel tank

Material problems brittle at low temperature

Air / H2 explosive


Niklas Wingborg2007

Hydrazine, N2H4

Can be used as a bipropellant fuel and as a monopropellant

Thermally unstable and cannot be used as a regenerative coolant in bipropellant engines

As a fuel, it is hypergolic with many oxidizers

Positive enthalpy of formation (+50.434 kJ/mol =+12.05 kcal/mol, liquid at 298 K)

Bp= 114°C, Mp=+2°C, dens= 1.00 g/cm3


Niklas Wingborg2007

Hydrazine, N2H4

Hydrazine toxicity concerns

Acute toxicity: short-term exposure

Chronic toxicity: long-term exposure

Volatile

Carcinogen


Niklas Wingborg2007

Monomethylhydrazine (MMH), H3C-NH-NH2

Frequently used storable, hypergolic bipropellant fuel for satellites and upper stages

Can be used as a regenerative coolant in bipropellant engines

Low freezing point (-52°C)

Density = 0.87

Concern about toxicity of vapors (more volatile than hydrazine itself), Bp= +88°C


Niklas Wingborg2007

AMSAT P3-D Launch Campaign Kourou

http://www.amsat-dl.org/launch

N2O4 filling operation MMH filling operation


Niklas Wingborg2007

Aestus: Ariane 5 upper stage engine

Fuel: MMH

Oxidizer: N2O4

MMH regenerative cooling

Multiple re-ignition capability

Thrust: 3 tons

Engine mass: 120 kg

Length: 2183 mm


Niklas Wingborg2007

Chamber

Lc

Rocket engine design

Injector

Ae

At

fo mmm


Niklas Wingborg2007

Injector face

Mass flow and mixing diameter of chamber


Niklas Wingborg2007

Characteristic velocity, c*

Depends on the properties of the propellant

Unit: m/s (but it is not a velocity)

Independent of pressure (as long the reactions don't change)

CEA c*

c*-efficency; ratio between calc. and measured c*

*c

Apm tc


Niklas Wingborg2007

UDMH / HNO3

Characteristic velocity, c*

1*

*

calc

meas

c

c


Niklas Wingborg2007

Propellant

Thrust, pressure and Ae/At

CEA Isp, c*

Massflow

c* and massflow At Ae

Injector and massflow Ac

Propellant Lc

Rocket engine design: summary


Niklas Wingborg2007

Solid rocket motors


Niklas Wingborg2007

Solid rocket motors

Case with propellant Nozzle

Igniter


Niklas Wingborg2007

Solid propellants

Solid mixture of oxidizer and fuel

Oxidizer: Ammonium perchlorate (AP), NH4ClO4

Rubber binder matrix: HTPB

Fuel: Aluminium powder

Burns on the surface

Burn time determined by the smallest dimension


Niklas Wingborg2007

Solid propellant geometry

The case is protected by the propellant

Shape of combustion channel pre-programmed pressure and thrust profile


Niklas Wingborg2007

VEGA


Niklas Wingborg2007

Combustion of solid propellants

Piece of solid propellant: 10x20x50 mm


Niklas Wingborg2007


Small pices of propellants


Niklas Wingborg2007


Small pieces burn fast

The combustion proceeds perpendicular to the surface

Gas generation proportional to burning surface and burning rate, r

pbrAm


Niklas Wingborg2007

r measured at different pressures

a and n calculated

In this case at atmospheric pressure

ncapr



Niklas Wingborg2007

*c

Apm tc

ncapr

pbrAm

n

t

pbc A

caAp

1

1

*

n must be < 1, preferably 0.5 or lower



Niklas Wingborg2007

r is altered by the initial temperature. A warm propellant burn faster


time

pre

ssu

re

T1

T2

T2 > T1


Niklas Wingborg2007

Solid propellant mechanical properties

Cracks in the propellant > Ab > pc

Might lead to failure

Good mechanical properties is important

Must be elastic

Tg < minimum service temperature

Good bonding to case important

Debonding > Ab > pc


Niklas Wingborg2007

Manufacturing composite solid propellants

Liquid rubber (HTPB), AP and Al are mixed under vacuum

When properly mixed a curing agent is added

Continued mixing

Cast in mould to obtain desired shape

Cured at elevated temperatures

Mould = rocket motor

Machining

Final charge X-rayed to detect cracks, voids etc


Niklas Wingborg2007

Not possible to obtain maximum theoretical Isp

Isp limited by viscosity

AP particle size: bimodal or trimodal

Manufacturing composite solid propellants

% AP

Isp

(N

s/kg

)

~80%


Niklas Wingborg2007

Composite solid propellants

Large amount of smoke is formed AP HCL hydrochloric acid Shuttle ~600 tons conc. hydrochloric acid Ariane-5 ~300 tons conc. hydrochloric acid


Niklas Wingborg2007

Current trends


Niklas Wingborg2007

Current trends

Green solid propellants to replace AP (ADN, AN, HNF)

Green cryogenic solid propellants

Green oxidizers (N2O, H2O2)

Hypergolic rocket fuels to replace hydrazine and MMH

Green monopropellants to replace hydrazine

Exotic molecules, HEDM (N4, N8)


Niklas Wingborg2007

Minimum smoke propellants


Niklas Wingborg2007

Why is smoke a concern?

NC-baserat AP/Al/HTPB


Niklas Wingborg2007

Ammonium dinitramide, ADN

NH4·N(NO2)2

Solid white salt

Intended for solid propellants

No chlorine content

Minimum smoke

High performance

Very soluble in water (80% at RT)

Synthesis developed at FOI

Produced on license by EURENCO Bofors in Sweden


Niklas Wingborg2007

ADN-based solid propellants


Niklas Wingborg2007

Solid propellant testing at FOI

Testing of missiles for the Swedish defense

niklas wingborg foi, energetic materials

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