Page **19** of **41**

### Re: Bottle Rocket B

Posted: **March 10th, 2011, 3:00 pm**

by **space scientist**

sciencegirl23 wrote:kittykat wrote:my rocket is big.... like

five feet big.

(yes it is legal to be that big)

How are you getting over 30 seconds with a rocket that large? Wouldnt it be really heavy..?

For the second question, length isn't a certain indicator of weight, for different building materials and designs have different densities. In addition, the people didn't say anything about getting 30 second times.

### Re: Bottle Rocket B

Posted: **March 10th, 2011, 6:33 pm**

by **sciencegirl23**

kittykat wrote:Wooh got a 30.56 flight time!!

umm yeah she did.

### Re: Bottle Rocket B

Posted: **March 10th, 2011, 8:06 pm**

by **space scientist**

sciencegirl23 wrote:kittykat wrote:Wooh got a 30.56 flight time!!

umm yeah she did.

I remember that post, but I didn't know if the bottle rockets that were mentioned in the posts were the same.

### Re: Bottle Rocket B

Posted: **March 10th, 2011, 9:09 pm**

by **soccerchamp30**

how long does your rocket go for?

### Re: Bottle Rocket B

Posted: **March 12th, 2011, 1:39 pm**

by **Littleboy**

Today I got 25 seconds

Hopefully I can do the same next week and that was not just a fluke. I think we finally figured it out.

### Re: Bottle Rocket B

Posted: **March 14th, 2011, 1:51 pm**

by **space scientist**

robotman09 wrote:The Center of Pressure (CP) is used to make balanceing a rocket easier.

You want the Center of Pressure to be a bit behind of the Center of Mass (CM) to get the best sliding. The only way I know how to find the CP is to use Barrowmans equation which with a little number play will return your backsliders CP

Guide on Calculating CP

I don't understand how subscript is used in the equations. Please may you explain?

### Re: Bottle Rocket B

Posted: **March 14th, 2011, 6:51 pm**

by **robotman**

The subscript is just used to differentiate variables. So Ln just means Length of the nose and so on. So the final equation is just a culmination of the equations above as defined as a variable with the subscript letter.

### Re: Bottle Rocket B

Posted: **March 15th, 2011, 1:34 pm**

by **space scientist**

I still have a few questions about the equations. I don't know when to calculate Xn using the for cone or for ogive equations. I also don't know what (Cn)r is. In addition, if your rocket doesn't have a transition, do you just omit the variable for the transition from the final equation?

### Re: Bottle Rocket B

Posted: **March 15th, 2011, 1:42 pm**

by **Orchdork**

Orchdork wrote:Jocool wrote:quizbowl wrote:Has anyone seen relatively successful scores on non-backsliders?

im doing a non back glider rocket but so far we have only got 3.5 seconds and we go to competition on Saturday

Um..... if it isn't backslider, your rocket is doomed to somewhat fail epically.

well we stuck with our design and we came in 7th place so no epic fail tonight

### Re: Bottle Rocket B

Posted: **March 15th, 2011, 3:44 pm**

by **Littleboy**

This makes me mad. We lost our best rocket in a tree 60 feet in the air.