Introduction
The
rocket
The
launching pad
The launches
The
physics of the rocket
The
flight simulation
Bibliography
The launches and the reached heights (experimental data)
At the beginning of this experiment,
with the first version rocket, we were not really expert, therefore
we faced some difficulties in placing the bottle so that the opening
was centred with the valve and the air entered into the bottle. Later
on, with the second version rocket, we have changed the valve position,
putting it on the bottom of the bottle (the head of the rocket). At
this point the air inflation is carried out from the top, avoiding any
interference with the water filling the bottom of the rocket (the top
of the bottle).
At the end we focused on the rocket trajectory: we inserted three flaps
(made of paperboard) on the bottle sides and we added a nosecone (a
piece of another 1.5 litres plastic bottle).
(Last suggestions: grind the two bars on the contact points with the
bottle in such a way as to adhere as much as possible to the bottleneck).
The launching operations consist of filling the rocket of water for
about 1/3 of its capacity. The launching pad is then placed on the bottle
mouth, which is locked on the inner tube (now acting as a cap) by the
two bars (connected the spring). All the equipment is now overturned
and the launching pad is fixed to the ground.
We can then start with the air inflation (with a portable compressor),
followed, as last operation, by the measurement of the pressure inside
the bottle.
The launch is then observed with a pointer
(Figure 3), located at a known distance from the launching pad, supplied
of a goniometer which can provide the angle, with respect to the horizon
line, under which the maximum height reached by the rocket is observed.
Through the trigonometric relation:
the height reached by the rocket can be derived.
Some uncertainty estimations for the pointing angles and heights, contrarily
to the air pressure measurement which has been considered unaffected by
errors, have been carried out. In our future experiments we will surely
have the chance to improve our measurements.
The following tab reports the measurements recorded
during a session of launches. With reference to figure n°3, the various
quantities of filling water, as well as the relevant angles under which
the heights reached by the rocket have been observed, have been measured.
Height h0, as can be noticed, is simply the height of the pointer with
respect to the ground. The nominal pressure of the air in the rocket was
2 atm.
In the graphs here below reported, it is plotted
the height reached by the rocket as a function of the mass of filling
water (keeping constant 2 atm the initial air pressure at 2 atm).
Actually, as previously mentioned, we experienced some water leaks through
the valve located under the launching pad. Moreover, when inserting
the manometer on the valve, we newly encountered strong water leaks,
this leading to big air pressure drops.
These problems justify the different heights reached by the two rocket
versions, water masses and nominal pressures being equal.
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