Rocket Sciences

1. LIQUID FUELS

2.  Many chemicals have been used and tested
but only a few have been used in the
production of rocket engines which are:

3. i. Hydrocarbon fuels
ii. Liquid Hydrogen (H2)
iii. Hydrazine (N2H4)
iv. Unsymmetrical Dimethylhydrazine
(CH3)2NHH2
v. Monomethylhydrazine
(CH3NHNH2)

4. Hydrocarbon Fuels
 Petroleum contains a large variety of different HC
chemicals and most of them can be used as a rocket
fuel.
 Most common types are those that are used with
other applications and engines such as gasoline,
kerosene, diesel oil and turbojet fuel.
 Their physical and chemical properties have a wide
difference in the crude oil from where they were
refined with the chemical process used in their
production.

5.  Generally petroleum fuels form yellow white
flames and give good performance.
 They are easy to handle and low cost supply.
 A particular refined petroleum product is
called RP-I which is a mixture of saturated
and unsaturated HC and is used with liquid
oxygen in ATLAS, DELTA, TITAN-I &
Saturn rockets.

6.  Saturated hydrocarbons alkanes are the simplest
of the hydrocarbon species and are composed
entirely of single bonds and are saturated with
hydrogen.
 Unsaturated hydrocarbons have one or more
double or triple bonds between carbon atoms.
Those with double bond are called alkenes.
Those with one double bond have the formula
CnH2n (assuming non-cyclic structures).Those
containing triple bonds are called alkynes

7.  CH4 (Methane) is a cryogenic HC fuel.
 It is denser than liquid H2and low cost.
 It is used in the booster engines of launch
vehicles with liquid oxygen.

8. Liquid Hydrogen (H2)
 Liquid H2 gives high performance when
burnt with liquid fluorine and liquid oxygen
and is a great coolant.
 Liquid H2 is the lightest and the coldest with
a specific gravity of 0.07 and a B.P= 20 K.
 Due to very low temperature there is a
problem of selecting suitable tank and piping
materials as many metals become brittle at
low temperatures.

9.  Due to its very low temp. liquid H2 tanks and
lines should be well insulated to minimize
the evaporation of hydrogen or the
condensation of moisture or air outside.

10.  All common liquids and gases solidify in
liquid H2 and these solid particles blocks
the pipes and valves.
 So care should be taken before inducting
the propellant.
 Mixture of liquid H2 and solid O2 can be
explosive.

11.  Liquid H2 has two types:
i. Ortho-hydrogen
ii. Para-hydrogen
 Liquid H2 is used with liquid O2 in the main
engine of the space shuttle.

12.  Liquid H2 gives non toxic exhaust gas with
oxygen.
 It is used successfully to launch space
vehicles due to its high specific impulse and
just increasing the specific impulse a little the
payload capability also increases.

13. Hydrazine (N2H4)
 It is used both as a bi-propellant and a mono
propellant fuel.
 It has its related organic compounds (MMH)
& (UDMH) which have same physical and
chemical properties.
 Hydrazine is a toxic and colorless gas & has a
high freezing point (274.3 K)
 It has a short ignition delay and gives instant
ignition with nitric acid and nitrogen
tetraoxide.

14. Unsymmetrical Dimethylhydrazine
(CH3)2NHH2
 It forms a more stable liquid at high temps.
 It has a low freezing point (215.9 K) & high
B.P( 336.5 K)
 When it is burned with an oxidizer it gives
slightly lower values of specific impulse than
pure hydrazine.

15.  UDMH is usually mixed with (30-50) %
hydrazine.
 It is used in the Titan missile, launch vehicle,
lunar landing and take off engines.
 UDMH is used in Russian and Chinese
rocket engines.

16. Monomethylhydrazine
(CH3NHNH2)
 It is extensively been used in space craft
engines as a fuel specially in small attitude
control engines with N2O4 as an oxidizer.
 It is a better shock resistant, better heat
transfer, better liquid temp. range than pure
hydrazine.
 Like hydrazine its vapors can be ignited
easily in air. Materials that are compatible
with hydrazine are also compatible with
MMH.

17.  Specific impulse with storable oxidizers
usually is 1 or 2 % lower with MMH than
with hydrazine.
 Both UDMH & MMH are soluble in many
HC but hydrazine is not.
 All hydrazines are toxic materials but MMH
is the most toxic when inhaled and UDMH is
least toxic.
 MMH decomposes at 491 K.