2. In this presentation, I will show you the
general design of liquid-propellant thrusters. I
will then explain to you how a specific
propellant is chosen for a space mission. This
includes the efficiency (enthalpy change per
gram), environmental impact, safety and
toxicity of a propellant and an evaluation of
the use of an ignition system or a catalyst.
3. The idea of a liquid-propellant
engine is fairly simple. The fuel
and the oxidizer are pumped
into a combustion chamber, and
there they ignite to create a
high-pressure and high-velocity
stream of hot gases. The highpressure and high-velocity is
caused by the high temperature
(when temperature increases,
kinetic energy increases and
pressure increases as well).
When the gas exits the rocket by
the nozzle, the rocket lifts up
with great acceleration and
speed.
4. A multistage rocket is a rocket
with several stages that each
include an engine and a
propellant. Each stage is
mounted on one another, and
when the propellant in a stage is
fully burnt, the rocket simply
ejects the stage, making place to
the stage above it to thrust the
rocket. Usually, the first stage is
at the bottom and is usually the
largest. The second stage is the
one above the first stage, and is
usually the second biggest stage
and so on.
5. Having a multistage rocket for a long-range
space mission is very advantageous. When
the propellant is fully burnt in a stage, the
rocket simply ejects the stage. This causes
the rocket to be lighter, which makes the
rocket go faster and gain acceleration. Not
only do you gain acceleration, but you also
need less gas for your trip since the engines
won’t have to work as hard to propel the
rocket.
6. A hypergolic propellant is a propellant composed of
a fuel and an oxidizer that spontaneously ignite
when they come in contact with each other. The
advantage of using a hypergolic propellant is that
there is no need of an ignition source in order to
make them combust. Little energy is needed to
make them react, which means they are very
reliable. An example of a hypergolic propellant is
the Methylhydrazine and the Nitrogen Tetraoxide.
The Methylhydrazine is used as the fuel, and the
Nitrogen tetraoxide is the oxidizer.
7. Choosing the propellant for this space
adventure will not be an easy task. Many
criterias will have to be evaluated. The
efficiency (kJ/g), environmental impacts,
safety and toxicity and the evaluation of the
ignition system or catalyst will all be
considered into the choice.
8. H2 + ½ O2 = H2O deltaH = -241.8kJ/mol
H2 = 2.02 g/mol
½ O2 = 15.99 g/mol
Molar Ratio: 1:2
n = m/M
n = m/M
1 = m/(2.02)
½ = m/(31.98)
m = 2.02g
m = 15.99g
15.99 + 2.02 = 18.01g
-241.8kJ/mol /18.01g = -13.43kJ/g
Hydrogen and Oxygen efficiency: -13.43 kJ/g
9. Environmental Impact
The environmental impact of the Hydrogen and Oxygen
reaction only produces water vapour, which is harmless to
humans. Water vapour is the dominant greenhouse gas in
the atmosphere, but it does not affect temperature by itself.
It only amplifies the already warming planet.
10.
11. Safety Precautions
Hydrogen Gas: Hydrogen is a highly reactive gas. With only
23% air, hydrogen gas will ignite. Simple friction will cause
hydrogen to ignite. Also, hydrogen fire is invisible, so you
would discover the fire by simply walking into it.
Oxygen Gas: Oxygen gas supports combustion. Any
material will ignite faster into an oxygen-only environment.
Do not smoke or expose an open-fire anywhere near oxygen.
12. Catalyst/Ignition System
There are two ways to ignite hydrogen and oxygen. The first
one is to bring a little spark of 20 microjoules or let the
hydrogen and oxygen autoignite at a temperature of 540
degrees Celsius at normal atmospheric pressure.
13. Qwater = (200)(4.19)(280-0)
Qwater = 234640J
-Qmethylhydrazine = Qwater
-234640J = 234640J
-234.64kJ
H2NN(CH3)2 = 60.1 g/mol
n = m/M
n = 4.8/60.1
n = 0.08
234.64/0.24 = -977.66kJ/mol
-977.66/34.23 = -28.56 kJ/g
2N2O4 = 183.92g/mol
n = m/M
0.16 = m/183.92
m = 29.43g
14. Environmental Impacts
Methylhadrazine produces Nitrogen gas, Carbon Dioxide and Water Vapour when it
combusts.
Nitrogen gas composes 78% of the air we breathe. Breathing too much nitrogen will
cause suffocation. Nitrogen is often used as a fertilizer in the envrionment. Food that
is rich in nitrogen elements can cause the oxygen transport of the blood to decrease.
Nitrogen mixed with oxygen creates nitrous oxides, which can be harmful to the
brain.
Carbon Dioxide is negatively influences the quality of our air and also is one of the
worst greenhouse gas. It causes extreme weather change and global temperature
increase. Companies now have carbon taxes, which are taxes put on companies
based on the amount of carbon dioxide released into the atmosphere.
Oxygen gas supports combustion. Any material will ignite faster into an oxygen-only
environment. Do not smoke or expose an open-fire anywhere near oxygen.
15.
16. Safety Precautions
Unsymmetrical Dimethylhydrazine is a toxic
liquid that is used as a propellant. It is
carcinogen and it can explode near oxidizers.
Keep far away from any ignition source or any
heat sources. Do not inhale. Wear proper lab
equipment, because if USDM comes in contact
with the skin, the skin will absorb USDM.
19. Environmental Impacts
N-Dodecane and Oxygen produces carbon dioxide and water
vapour. Carbon Dioxide is negatively influences the quality of
our air and also is one of the worst greenhouse gas. It causes
extreme weather change and global temperature increase.
Companies now have carbon taxes, which are taxes put on
companies based on the amount of carbon dioxide released
into the atmosphere.
21. Safety Precautions
N-Dodecane: Must be kept away from any ignition source or any
source of heat because it is a combustible liquid. It is hazardous if
it is inhaled and slightly hazardous in contact of skin. Wear proper
lab equipment nearby the product (glasses, apron, gloves, etc). It
is hazardous to the lungs and the central nervous system if
inhaled.
Oxygen Gas: Oxygen gas supports combustion. Any material will
ignite faster into an oxygen-only environment. Do not smoke or
expose an open-fire anywhere near oxygen.
22. Catalyst/Ignition Source
N-Dodecane auto-ignites at a temperature of
203 degrees Celsius. N-Dodecane also ignites
when mixed with oxygen in the combustible
chamber with heat. Since N-Dodecane is a
cryogenic propellant, it needs an ignition
source which is heat.
24. Environmental Impacts
Ethanol produces Carbon Dioxide and Water Vapour when it
combusts with oxygen.
Carbon Dioxide is negatively influences the quality of our air and also
is one of the worst greenhouse gas. It causes extreme weather
change and global temperature increase. Companies now have
carbon taxes, which are taxes put on companies based on the
amount of carbon dioxide released into the atmosphere.
Oxygen gas supports combustion. Any material will ignite faster into
an oxygen-only environment. Do not smoke or expose an open-fire
anywhere near oxygen.
25.
26. Safety Precautions
Ethanol is a toxic substance that when it is
ingested, it can be very harmful. Ingesting ethanol
in large quantities can cause coma or death. It has
similar effects as alcohol when ingested. Ethanol is
a very inflammable liquid. Ethanol is also
carcinogenic, which means that it can cause
cancer. Needs to be sealed tightly and needs to be
far from ignition sources or heat sources. Needs to
be kept away from oxygen gas as well.
27. Catalyst/Ignition System
Ethanol autoignites at a temperature of 425
degrees Celsius. It also ignites when mixed with
oxygen in a combustion chamber when heat is
applied to the mixture.
28. Even though Unsymmetrical Dimethylhydrazine
and Nitrogen Tetraoxide has a better efficiency than
Hydrogen and Oxygen, I chose Hydrogen and
Oxygen as a propellant for the space adventure. It
has an efficiency of -13.43kJ/g, has a mass of 18.01g
which is the lightest and has very few environmental
impacts. Hydrogen and Oxygen are also safer than
the other propellants.
