2. Rocket science – the facts
Before we begin the design and construction of our bottle rockets it
is important we understand some of the science behind the fun. The
next few pages detail how rockets work and the uses we have for
them from entertainment to our exploration of outer space.
How does a rocket work?
If a balloon is filled with air and then
released it speeds along – a rocket
works in the same way. A mixture of
hydrogen and oxygen fuel explodes all
the time, pushing hot gas out of the
back of the rocket and propelling it
along.
Firework rockets are the simplest form
of heat engine. They are packed with a
propellant, a powder that burns fiercely.
The smoke and hot gases stream from
the base and drive the rocket upwards,
while the long stick keeps the rocket’s
flight straight. The propellant is slowly
consumed by combustion, and finally the
burning powder ignites an explosive
charge which expels the glowing stars.
3. How are spacecraft
launched?
Earth’s gravity is so strong that rockets are needed to propel
satellites and other spacecraft out of the atmosphere and into
space. Many spacecraft are launched by solid-fuel boosters, which
are rocket engines that, like firework rockets, contain a solid
propellant. Solid-fuel rockets can produce great power but, once
ignited, they cannot be shut down; they fly until all the propellant
has burned.
Spacecraft that require repeated firings of their engines, often for
manoeuvring in space, have liquid-fuel rocket engines. Liquid
hydrogen and liquid oxygen are often used.
The space shuttle has five principal rocket engines. These are two
huge solid-fuel boosters fixed alongside the orbiter, and three
liquid-fuel main engines at the rear of the orbiter. These five
engines only take the shuttle into space. Other smaller liquid-fuel
engines are used to attain and level orbit and to manoeuvre the
shuttle in space.
4. What happens to rockets
after launching a
spacecraft?
Rockets are only needed for
the first few seconds of a
spacecraft’s journey. They
then fall back down to
Earth, land in the sea and
are recovered by special
ships.
How do spacecraft land
back on Earth safely?
Spacecraft such as Apollo and Soyuz
both land in the sea when they come
back to Earth.
5. However, the Space Shuttle is specially designed to land like a
normal aeroplane on a runway.
6. Design team
Organise yourselves into groups of no more than five people.
You will need:
• Project team supervisor
• 2 x design engineers
• 2 x construction team
You will need to collect:
• 1 plastic pop bottle
• scissors
• ruler
• string
• duct tape or glue
• coloured pens
• coloured card or paper
The Project team supervisor will be responsible for overall control of
the rocket design and build process. They will ensure the team works
together and co-operates at all stages of the design and build
process.
The design engineers will be responsible for the design of the
rocket. In particular, the nose cone, tail fins and rocket livery i.e.
any external decorations such as flags or names.
Construction
The construction team will be responsible for
the final assembly of the rocket and at this
7. stage of the project all team members will be involved in completing
the rocket under their supervision.
Design information – your
mission
Create one bottle rocket that will fly straight and remain aloft
for a maximum amount of time.
Part one: the tail fins
Use scrap paper to work out the size of fins needed for your
rocket. Once you have got the size correct then use this scrap
paper as a template and get the coloured card; fins will be made
from it. Cut three shapes out of the folded bottom in the shape that
the diagram shows. Your fins will be triangular.
9. Mark straight lines on the bottle by putting the bottle in the door
frame or a right angle and trace a line on the bottle with a marker.
Use these lines as guides to place the fins on the bottles.
Make three fins and tape them on the rocket. Be sure that the fins
are spaced equally around the rocket body. This can be achieved by
using a piece of string and wrapping it around the bottle and marking
the string where it meets the end. Mark the string and lay it flat on
a metre-stick or ruler. Find the circumference of the bottle by
measuring the length of the string to the mark. Once you know the
circumference, then you can divide it by three to find the distances
the fins should be separated. Secure the fins to your bottle with
duct tape.
Part two: the nose cone
Use the scrap paper to make a template for your nose cone.
Once you have got the size correct then use this scrap paper as a
template and get the coloured card; the cone will be made from it.
Then, using scissors, cut out the nose cone shape and trim the cone
to make it symmetrical. Use your plastic bottle to check your cone
will fit properly. (Hint: the diameter of the bottom of the cone
should be a little wider than the diameter of your plastic pop bottle).
The picture above gives you an idea of the approximate shape that
the nose cone should be. Secure the nose cone to the top of the
rocket using glue or duct tape.
10. Part three: the livery
Now the major parts of construction are
completed, it is time to name and decorate
your rocket. Use plain or coloured paper
and pens to do this. You may like to include
a flag or put the names of your team
members on the outside of the rocket.
At this stage of the process you can be
as creative as you like so have fun!
Important
information
In order to be successful throughout the different stages of this
project it is important that all team members contribute and do the
following:
• listen and respect other peoples ideas and suggestions
• have sensible discussions when necessary
• co-operate and work together as a team
On launch day
Once all rockets are completed and ready for lift off all teams will
move to the launch area (the sports field) and from a safe distance
will observe the rocket launches taking place that day.
Whilst waiting for your team’s rocket launch you are asked to remain
behind the safety barrier and most importantly to wait quietly and
behave sensibly.
