Analysis of Parachute Design

We know that parachute is used to land something from a high altitude safely. Parachute may have different size, shape and also holes on the parachute sheath. There must be the best parachute for landing a food during war, for free fall and also for a demonstration. This investigation will find the effect of size, shape and holes on landing of parachutes.

A parachute is essentially a device that is used to slow down the speed or motion of an object. A parachute is typically used through atmosphere by creating a force called anti-gravitational force that counters the gravitational force. A parachute can also provide stability as it creates a drag when falling. [1] 

Literally, ‘parachute’ is derived from the word ‘para’ and ‘chute’ which means against and falls respectively. This word originates from Ancient Greek and French. The first soft parachute was invented in 1973 but the event was not witnessed. It was developed by Blanchard using silk. Up until that point, parachutes were all made with rigid frames. [2] 

THE IDEA OF THE INVESTIGATION

A recent television program “Backyard Science” on TVIQ in Astro Channel had tried an experiment on parachute. The experiment was based on normal competition of soft landing. They figured how to land an egg from a high place to the ground without damaging the egg.

The experiment in the show triggered me to find more about parachutes. I watched several videos on parachutes and realized that parachutes have different shapes. I wanted to investigate how shapes affect the way parachutes land. While browsing through the internet, I found out that there are holes on parachutes. So I start to make an experiment on parachutes by using simple baskets as the load and garbage plastic bags as the parachutes. I personally create the parachutes and vary the shapes with round, triangle and square. The number and size of holes are also created accordingly.

2.0 RESEARCH QUESTION

The research question for this Extended Essay is to find the right shape of the parachute for the best soft landings with the least dispersion from the targeted place of landing together with the ideal number of holes needed and the right size of the holes.

3.0 HYPOTHESIS

My Extended Essay is about producing a parachute that can land the longest time so that the time of impact is increased by creating the most air resistance. In addition, the parachute must land on the targeted place which is actually vertical to where the parachute is launched.

The initial assumption is that, the bigger the surface area of the parachute, the more air resistance it produced to create a drag on the parachute. Consequently, the time taken for the parachute to land is increased. This is for the first characteristic of my parachute.

The second characteristic is to make the parachute land on the targeted place which is vertical to the place where the parachute is launched. The assumption made is that, by creating holes, it may reduce slightly the air resistance, thus the parachute will wander less and falls almost vertically. The more holes are created, the more exact the parachute will fall at the targeted place. The same case applies when the size of the holes is increased. The bigger the size of the holes on the parachute, the more exact the parachute lands on the targeted place.

Some effects must be taken into consideration, as the holes are created; the time taken for the parachute to reach the ground is reduced. Thus, to make the ideal parachute, the right shape, the right number of holes and the right size of holes need to be investigated thoroughly. That is the research questions of my extended essay.

4.0 METHODOLOGY

4.1 METHOD DEVELOPMENT AND INITIAL PLANNING

Designing the methodology or the method development for this investigation requires plenty of patient and energy. First and foremost, for the parachute sheet, I substitute the sheet with a garbage bag. A few surveys have to be done to find the most suitable garbage bag to be used for this investigation as it involves the shape of the sheet. The thickness of the garbage bag has to taken into consideration too, as it may differ from the actual parachute sheet. Last but not least, the cost of all materials involved is also taken into account. Besides using garbage bags as substitutes for the parachute sheet, I use strings to hold the sheet to the load. I use a normal string and a basket that has holes as the load. The reason I used such basket is to make my model easier. This is because I can make use of the existing holes in order to tie up the string that is connected to the parachute.

After a few discussions with the supervisor, it is agreed that the sheet be varied by changing the shape, size and number of holes on it. Based in the initial planning, I intend to investigate the effect of shape and number of holes on the parachute in order to obtain the most efficient parachute. In this investigation, an efficient parachute is one that can reach the ground with the longest time and as near as possible to the targeted place of landing.

The first parachute launching was set outdoor between two buildings. The results of the experiment are not reliable because of wind factor which affect the results. This is a type of limitation. So, I decided after that to conduct the experiment indoor. I opt for the academic building at MARA College Seremban as it is readily available. The parachute was initially planned to be launched from the second floor of the building. It is later changed as the parachute may hit the stairs at the floor below. So, the first floor of the building is chosen instead (Figure 1).

4.2 EXPERIMENT PROCEDURE

First of all, the garbage bag must be cut to the shape needed. In this investigation, the garbage bag is cut into square shape (65cm x 65cm), round shape (radius 65cm) and triangle shape (base 65cm and 65cm height). This set of parachutes is to test that they can land on the ground at the longest time and that they also can land on the targeted place. Once the parachute is done, the parachute with square sheet is released first from the top of 1 storey academic building (height). The time taken for the parachute to land is taken and recorded by using a stopwatch. For the data on whether parachutes can land on the targeted place, a measuring tape is used to measure distance from the centre point (X sign on the target face) to where the parachute land. The experiment is then repeated five times for each shape so that the average time taken and distance can be measured.

After the first model or shape is done five times, the same procedure is repeated for the next shape of parachute which is round shape and then the triangle shape. While doing the triangle parachute, some difficulties are encountered. This is due to the shape of the parachute itself which makes it difficult to act like a normal parachute. Sometimes the parachute falls abruptly. The experiment is still done until five readings are taken.

After all shapes of parachute have been tested, the other variables are tested next. The next variable is the number of holes needed in order to make the parachute land on the targeted place. Four holes are created on the parachute sheet. By using the same sequence (square, round and triangle), the experiment is started all over again. For the first 4 holes, the size is 2cm in diameter. The distance between holes is situated equally so that the air resistance can disperse equally around the parachute, hence enabling parachute to travel in a straight path. For this investigation, the readings are only taken three times. This is because based on the first experiment; the readings do not vary much hence it is sufficient to take only three readings.

The numbers of holes are increased from four to eight after the previous experiment is done. The assumption is that with increasing number of holes, the time taken for the parachute to reach the ground is less. At the same time, the place where the parachute lands are much more exact to the place targeted. The aim of this experiment is to find the most efficient parachute design that is one that has the longest time for landing and yet falls on the exact or targeted place. So the size of holes is increased. The same procedure is repeated but the size is increased from 2cm to 5cm.

When the size of the holes is increased, it is expected that the parachute will fall even faster and may fall directly on the targeted place. The effect will be more significant when the number of 5cm holes is changed from four holes to eight holes.

5.0 RESULTS AND ANALYSIS

5.2 GENERAL OBSERVATION ON BEHAVIOUR OF PARACHUTE EXPERIMENT

Qualitative Data

Right after the basket (mass) is released, the parachute sheet immediately will open to resist the gravitational force, and thus the time taken to fall is reduced.

When the parachute is falling, is observed that the parachute with round shape is most stable as the basket did not swing. Compared to the other two shapes, rectangular parachute can still be considered as stable but triangular parachute is very unstable.

When the parachute hits the ground, there is sound produced. It is the sound of impact. As the number of holes is increased the volume of the sound increases whereas time taken to reach the ground decreases.

5.3 COMPARISON BETWEEN DIFFERENT SHAPES OF PARACHUTES ON LANDING

Different shapes of parachute sheet will affect the time taken for the parachute to land. This is because of the area of each shapes is different. The distance where the parachute lands to the targeted spot is actually determined by the holes on the parachute.

For the square parachute, the formula for area of square is;

Since the square parachute length is 65cm and the width is 65cm, thus the area is 4225cm2.

For round parachute, the formula of the area is equal to the formula of a circle which is;

The r is representing the radius of the circle. Since the radius of this round parachute is 65cm, the area is 13273cm2.

And for the last shape which is the triangle parachute, the formula is;

By using the formula stated above, if the height and the base of triangle are both 65cm, the area of the triangle is 2112.5cm2.

Air resistance depends on the shape or the cross sectional-area of the falling object which is the parachute in this experiment. The bigger the shape or cross sectional area, the more or effective the air resistance in countering the opposing motion of the parachute. [3] Thus, the air resistance to the round parachute is the most effective than the air resistance that acts upon square and triangle parachute. The round parachute falls with a smaller acceleration and takes longer time to reach the ground even though the mass are all the same. Table 6 below shows the detail data of the experiment based on the shape of the parachute.

To check the degree of precision of the data, we can calculate the coefficient of variation by using the formula stated below. If the degree of precision calculated is less than 1, the data is taken to be precise.

This is an example of a calculation to obtain the degree of precision of the data. The example is based on the data for time taken for a square parachute.

First, calculate the degree of precision for the time taken. The average time taken is 1.88 sec. The calculation is shown below

Then the standard deviation of 0.158 is obtained from the calculation shown below

Finally the coefficient of variation can be calculated after the average and the value of standard deviation are found. The coefficient of variation is 8.4 as obtained from calculation shown below

The value of the coefficient of variation is higher than 1. This shows that the data obtained for the time taken for the square parachute to reach the ground is not precise. This might be due to some limitations that occurred during the launching of the parachute. The limitation is discussed in the evaluation section.

For the other set of data the calculation is not shown as the calculation is similar. Here is the summary of the coefficient of variation for the data:-

5.4 COMPARISON BETWEEN DIFFERENT NUMBERS OF HOLES ON LANDING

The purpose of holes based on research, it is to prevent the parachute from oscillating. In my experiment, the parachute does not oscillate and the holes are not preventing the parachute from oscillating since no oscillation occurs. The holes on my parachute actually make the parachute to land even closer to the targeted place of landing.

Even though I try to create a parachute that can land almost vertically on the targeted spot, I also want the parachute to land softly which means a longer time is needed to reach the ground. As the number of holes increases, the time taken for the parachute to reach the ground is decreases. This is because, as stated before the bigger the shape or cross sectional area, the more effective the air resistance in countering the opposing motion of the parachute. [4] Thus when holes increases, it actually decreases the area of the parachute and eventually makes the parachute reach the ground faster. This can be proven by calculating the area of the parachute after the holes are introduced. First calculate the area of the holes. Since the holes are round in shape, the area is calculated by using the formula,

The diameter of the holes is 2cm. Hence the radius is 1cm. By using the formula, the area for each hole is 3.14cm2. There are 4 holes introduced to the parachute, thus the total area loss is which is 12.57 cm2. In table 9 on the next page shows the final area of parachute after the holes are introduced;

From above data, once again we can see that the area of the parachute is differing by;

This is contrary to my first purpose which is to land the parachute with the longest time. Hence, in this particular experiment, I just want to check my assumption that holes can make the parachute land on the targeted place.

Besides, I also change the number of holes to investigate whether the number of holes does give an effect to the place of landing. The detail data for this experiment is presented in the next page.

Based on the data in table 11, it shows that when the number of holes increased, the place where the parachute lands is nearer to the targeted place. This is because when more holes are created, the more it approaches the free fall concept. Free fall is when an object is acted upon by a gravitational force only. [5] It can also explain on the other way round, same like the previous. The area of the parachute after 8 holes are created is as follows;

From the data on the previous page, we can see that the area of the parachute is differing after number of holes increased by;

As the area of the parachute decreases, the air resistance will against the parachute also decreases. Hence the parachute will land more vertical compare to the less number of holes. A free fall is when an object falls vertically.

The same steps are taken to calculate the degree of precision as previous done. This is to ensure whether the data obtained is precise or not. The calculation is again not shown since the calculation is exactly similar with the calculation before. Here is the summary of the degree of precision for the data of comparison between different numbers of holes on landing.

5.5 COMPARISON BETWEEN SIZES OF HOLES ON LANDING

In this investigation, it is just to check whether the size of the holes on the parachute will affect the place of landing. Based on previous understanding, the holes function to make the parachute land vertically. As the number of holes increases, the place where the parachute land is nearer to the targeted place. Take note that when more holes, the less time taken to reach the ground. Thus, this test has nothing to do with the time taken, just for the distance where the parachute land.

It is said that when the holes are bigger, the parachute may reduce the air resistance and hence it almost resemble the free fall theory. Imagine if the big holes are doubled the number? The place where the parachute land will be much more nearer compare to other situation but the time taken is the least. Table 14 on the next page is the data for the parachute with larger holes which is changed from diameter 2cm to 5cm. Data for parachute with small holes (2cm) is the data in table 11.

For this set of data, once again the coefficient of variation is calculated so that we can see how precise the data is. The calculation is similar to both previous data. The calculation is not shown and the result is tabulated below.

5.6 SELECTION FOR IDEAL PARACHUTE

Since this Extended Essay is to find the best parachute that can reach the ground in longest time and that can land nearest to the target point, the longest average time taken for landing in take into consideration. Besides, for the parachute that can land nearest to the target point, the smallest average distance is considered.

Base on data collected, the shape of parachute that land the longest average time is the round parachute. Thus other shape of parachute will not be selected. The next criterion is chosen by calculating r2-value in the regression statistics. The r2-value is calculated automatically by using Microsoft Excel 2007.

The r2-value will show which combination of round shape and holes is the ideal parachute. The more the value of r2 is approaching to 0, the more likely the parachute to be chose. On the next page is the result of the r2-value.

The r2-value for round parachute with 4 small holes

Based on table 17, the most likely combination of parachute that will be selected is round parachute with 8 small holes (0.82072) followed by round + 8 big holes (0.786996), round + 4 big holes (0.766919) and lastly round + 4 small holes (0.669984).

6.0 EVALUATION

Throughout the experiment, there are some factors that cause limitation to my data. First and foremost, a major limitation of wind. At first I do the experiment outdoor between two buildings. The place is windy and causes my parachute to land far from the targeted place. This is overcome by doing the experiment indoor. Then, there is a limitation of a launching place, which is not high enough. The initial planning is to launch from the second floor which is approximately 12 feet from the ground floor. Then it is changed to the first floor. The time taken is very short for every reading for example not exceeding 3 seconds.

The experiment also requires one to climb up the stairs and record the time taken for the parachute to land. I record the time from where I have launched the parachute by only using the sound of impact as the indicator that the parachute had reached the ground.

7.0 CONCLUSION

From this Extended Essay, I conclude out that in order to make a parachute, there are several factors are significant that effect to the safety of the load or human being using it.

For minor reasons, I now know how to tackle or to conquer the soft landing competition which involves the usage of parachutes.

For major reasons, to create a genuine parachute that are used to carry human beings, the factors like shape and holes are very vital and now I know the factors and how it functions.

Based on this Extended Essay, the best parachute is the one that can reach the ground the longest time and that can land nearest to the target point. The round parachute is found to be the parachute that land at longest time with average time taken for landing is 2.24 seconds compared to square parachute (1.88 seconds) and triangle parachute (1.02 seconds).

When there is no hole, the parachute will disperse furthest from the targeted place. The bigger the holes and the more the holes, the more accurate the landing. On the other hand, the time taken is short hence the landing is rather abrupt or not soft. The round parachute with small holes is found to be the parachute that land at shorter distance from the targeted place which is 1.08m for 4 small holes and 0.96m for 8 small holes compared to round parachute with no holes (1.198m). The round parachute with big holes is not chosen for the best parachute because the time taken to reach the ground is shortest. This is because as the holes become larger, the time taken is very fast thus creating a greater impulsive force.

In conclusion, base on the r2-value, the best and ideal parachute is one that is round in shape and having eight numbers of small holes. The average time taken is 1.70 seconds and the average distance (dispersion) is 0.96 metre while the r2-value is 0.82072.

8.0 FURTHER RESEARCH

In my extended essay, I only take into consideration the shape of the parachute and the holes on the parachute. These factors affect time taken for parachute to land and also the place where it lands. Further research can also be done under the same topic.

The other factor that may be used in future research is length of string. Investigation can be done to determine whether different lengths of strings connected to the parachute can affect the way it lands.

Other factors, for example, materials the parachute is made of and number of strings attached can also be investigated.

It would be interesting to find out the outcome of this investigation in the future.

9.0 BIBLIOGRAPHY

Books

Chang, S. L. (2007). FocuSSuper Physics SPM. Malaysia: Pelangi.

Teek, F. S. (2007). Success Physics SPM. Malaysia: Oxford Fajar Shah Alam.

Websites

(n.d.). Retrieved January 17, 2010, from http://sg.answers.yahoo.com/question/index?qid=20080131162150AA2iOT5

History of the Parachute. (n.d.). Retrieved January 17, 2010, from http://inventors.about.com/od/pstartinventions/ss/Parachute.htm

Parachute. (n.d.). Retrieved August 11, 2009, from Wikipedia, The Free Encyclopedia: http://en.wikipedia.org/wiki/Parachute