Help With Parachutes

[caricature_of_intimacy]

Hey there. I'm a senior in Mark Twain Junior High School now (8th grade) and I was wondering if someone could help me with my science fair topic. My question is what affects the flight of a parachute.

I'm planning on testing multiple variables, but I'm finding it hard to find variables that when I test them, I can measure the dependent variables.

So far, I've come up with the material that a parachute is made out of, the shape of the parachute, and the area of the parachute material.

If anyone could help me come up with other variables, it would be greatly appreciated.

Thanks!

[caricature_of_intimacy]

Also, since I'm doing the material a parachute is made out of, what kind of materials could I test? In other words, which materials would be ideal for testing?

Once again, thanks in advance.

[caricature_of_intimacy]

Anddd one more question.

What would be the ideal dependent variable? Speed, drag, etc.? And since I'm actually doing multiple experiments to test different variables, should I use the same dependent variable in each experiment?

And once again, thanks!

[ghariman]

Hi there,

A parachute uses the concept of increasing drag on a falling body to decrease it's velocity during a fall.

A good website to start reading would be this:
http://en.wikipedia.org/wiki/Parachute

You have chosen very good variables to start with.
I found a website about materials used for parachutes:
http://www.asp-rocketry.com/recoverydevices.html
However I think those materials would be hard to come by. So instead you should try other 'fabric' type of materials. Start with the most simple ones (that may not even work) like newspaper. Then how about grocery plastic bags. How about grocery paper bags ? If you have time go to a local fabric store/art store and try buying some fabrics there.
One thing to note down from your experiment on the different materials used is it's strength and pliablity/flexibility and also how porous (how easy the material lets air through) it is.

Some good dependent variables to jot down would be:
- speed of falling body vs. variables
- time for parachute to open from start of fall vs. variables
- strength of parachute vs. variables (how heavy of an object can a certain material hold ? Or will certain shapes and size of parachute design tend to fail to open ? Or would open but then close again in mid air ?)
- you can also do a matrix of experiment to test materials vs. area. That is do certain materials require less area to perform the same as other material that require a larger area for a certain weight ?

I also watched a TV show once on the NASA ROVER parachute design. They were having problems deploying the parachute during scaled test as the parachute would fail to open up. It turns out that the hole opening at the top of the parachute was too small. So you could also investigate what parachute shapes need holes at the top to open ? And why do some need them and others don't.

Good luck with your experiment !

[caricature_of_intimacy]

Ghariman,

Thanks for taking your time to reply!

You said that I may want to note the porosity of the materials I used. I went to search for how to measure porosity, and I came across this:

http://en.wikipedia.org/wiki/Porosity#M ... g_porosity

I decided to measure the porosity of my materials the way that Wikipedia claims is the easiest, the volume/density method (the first method listed). I think I understand this method, but I'm a tiny bit unsure. Could you maybe give an example with real measurements (i.e. 5mL, 3g) and show me how to measure the porosity?

Also, I have seen on a couple of websites where they say to use a plastic shopping bag as the material for a parachute. I did some research on plastic bags and the different kinds, and it seems that there are multiple types of plastic bags. If I were to test a plastic bag, should I just list "plastic bag" as one of the materials I tested, or should I try and look into what the plastic bag I used was actually made of?

And one more thing - I've been having a lot of trouble trying to figure out which materials to test. Plastic bags, nylon, and possibly polyester are the only things I can come up with. Are there any other materials you can suggest?

Thank you so much!

[Louise]

Ghariman,
[snip]

And one more thing - I've been having a lot of trouble trying to figure out which materials to test. Plastic bags, nylon, and possibly polyester are the only things I can come up with. Are there any other materials you can suggest?

Thank you so much!

Parachutes used to be made of silk. Depending on how large your parachute is, it might not be too expensive to buy some silk fabric.

You could test different types of plastic bags or different thickness or weaves of a fabric.

Louise

[ghariman]

Hi There,

Well I actually didn't really think about how to measure porosity of the material. The link that you gave seems to try to measure porosity of materials for liquid material (ie. water). It seems that methods used to test these may be too complicated for you to do (requires specia equipments) such as explained in the link: http://www.fibtex.lodz.pl/57_20_81.pdf

Try reading briefly this link (go to very bottom) also:
http://www.kitebuilder.com/techsheets/Fabrictech.htm

If you get really stuck with trying to measure porosity perhaps you could just quantify it with words. For example make 3 catagories: Air tight (plastics), somewhat porous (papers), very porous (fabrics).

Sorry for not being able to help much! Good luck again.

Ghariman,

Thanks for taking your time to reply!

You said that I may want to note the porosity of the materials I used. I went to search for how to measure porosity, and I came across this:

http://en.wikipedia.org/wiki/Porosity#M ... g_porosity

I decided to measure the porosity of my materials the way that Wikipedia claims is the easiest, the volume/density method (the first method listed). I think I understand this method, but I'm a tiny bit unsure. Could you maybe give an example with real measurements (i.e. 5mL, 3g) and show me how to measure the porosity?

Also, I have seen on a couple of websites where they say to use a plastic shopping bag as the material for a parachute. I did some research on plastic bags and the different kinds, and it seems that there are multiple types of plastic bags. If I were to test a plastic bag, should I just list "plastic bag" as one of the materials I tested, or should I try and look into what the plastic bag I used was actually made of?

And one more thing - I've been having a lot of trouble trying to figure out which materials to test. Plastic bags, nylon, and possibly polyester are the only things I can come up with. Are there any other materials you can suggest?

Thank you so much!