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A water rocket is a type of model rocket using water as its reaction mass. The pressure vessel (the engine of the rocket) is constructed from thin plastic or other non metallic materials (usually a used plastic soft drink bottle) weighing 1,500 grams or less. The water is forced out by compressed air. It is an example of Newton's third law of motion.

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David Currier from Elwood, IN, USA,
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Congratulations to Khairul- SMK Seksyen 24(2) for the new Class D record of 281.07 feet (85.67 meters)

Acceptable descent profile?

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Acceptable descent profile?

Postby bugwubber » Mon Mar 31, 2014 1:20 pm

WRA, just wanted to get your take on this- this is a non ballistic recovery rocket. No chute, just falls sideways. Is this slow enough?

HK-A_2014331_129.png
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Re: Acceptable descent profile?

Postby WRA2 » Mon Mar 31, 2014 5:19 pm

bugwubber wrote:WRA, just wanted to get your take on this- this is a non ballistic recovery rocket. No chute, just falls sideways. Is this slow enough?

HK-A_2014331_129.png



The rule states 33 feet per second at touchdown. Any kind of recovery that achieves that speed is allowed (chute, steamer, wing/glider, tumble, side glider, etc.)

28.95 feet per second would meet the criteria.

All launched parts of rocket which travel over 6 meters (20 feet) in altitude must have a recovery system which limits their descent rate at time of touchdown at ground level to a maximum velocity of 10 meters/second (33 feet per second)


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Re: Acceptable descent profile?

Postby bugwubber » Mon Mar 31, 2014 8:51 pm

WRA2 wrote:
bugwubber wrote:WRA, just wanted to get your take on this- this is a non ballistic recovery rocket. No chute, just falls sideways. Is this slow enough?

HK-A_2014331_129.png



The rule states 33 feet per second at touchdown. Any kind of recovery that achieves that speed is allowed (chute, steamer, wing/glider, tumble, side glider, etc.)

28.95 feet per second would meet the criteria.

All launched parts of rocket which travel over 6 meters (20 feet) in altitude must have a recovery system which limits their descent rate at time of touchdown at ground level to a maximum velocity of 10 meters/second (33 feet per second)


Great! Thanks.


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Re: Acceptable descent profile?

Postby Water Rocket Expert » Tue Apr 01, 2014 10:12 am

Oh no, here he goes getting a record!

WRA2, would my altimeter work for testing descent rate on a unreinforced flight. It is peak altitude but it has descent rate feature.


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Re: Acceptable descent profile?

Postby WRA2 » Tue Apr 01, 2014 4:18 pm

Water Rocket Expert wrote:Oh no, here he goes getting a record!

WRA2, would my altimeter work for testing descent rate on a unreinforced flight. It is peak altitude but it has descent rate feature.


If you combine it with a good simulator and or video of the flight. You know the peak altitude. If you took video or used an onboard camera (better) you can figure the time the rocket took to descend from apogee to the ground and figure out feet per second from that.


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Re: Acceptable descent profile?

Postby bugwubber » Tue Apr 01, 2014 10:49 pm

Water Rocket Expert wrote:Oh no, here he goes getting a record!

WRA2, would my altimeter work for testing descent rate on a unreinforced flight. It is peak altitude but it has descent rate feature.


Well, whether we do or not, in this case I'm more interested in making sure the design conforms to WRA safety rules before I start telling others how to make it.


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Re: Acceptable descent profile?

Postby Water Rocket Expert » Wed Apr 02, 2014 2:36 pm

WRA2 wrote:
Water Rocket Expert wrote:Oh no, here he goes getting a record!

WRA2, would my altimeter work for testing descent rate on a unreinforced flight. It is peak altitude but it has descent rate feature.


If you combine it with a good simulator and or video of the flight. You know the peak altitude. If you took video or used an onboard camera (better) you can figure the time the rocket took to descend from apogee to the ground and figure out feet per second from that.


So does that mean we don't have to have onboard video, just good ground based video? That would be awesome because the camera I am using right now is too heavy for a 2 liter rocket.


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Re: Acceptable descent profile?

Postby WRA2 » Wed Apr 02, 2014 3:40 pm

Water Rocket Expert wrote:
WRA2 wrote:
Water Rocket Expert wrote:Oh no, here he goes getting a record!

WRA2, would my altimeter work for testing descent rate on a unreinforced flight. It is peak altitude but it has descent rate feature.


If you combine it with a good simulator and or video of the flight. You know the peak altitude. If you took video or used an onboard camera (better) you can figure the time the rocket took to descend from apogee to the ground and figure out feet per second from that.


So does that mean we don't have to have onboard video, just good ground based video? That would be awesome because the camera I am using right now is too heavy for a 2 liter rocket.


Your question was on how to determine the descent rate of your rocket.

Cameras are required onboard for all competitions except the flight duration:

http://www.wra2.org/WRA2_Class_C_Rules.php

No exceptions.


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Re: Acceptable descent profile?

Postby Water Rocket Expert » Thu Apr 03, 2014 2:30 pm

Thanks! I probably should have looked at the rules first.


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Re: Acceptable descent profile?

Postby U.S. Water Rockets1 » Sat Apr 05, 2014 10:07 pm

If you are interested in the descent rate only at the moment of landing, you can also use a reference object in the ground based video. You can see at that frame number the rocket is level with some object of a known height (you can measure it at any time) and then count the frames it takes to reach the ground from that point. The video file will have a set number of frames per second, you can figure out how many seconds it took to travel the known distance and divide to get feet per second.


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Re: Acceptable descent profile?

Postby Water Rocket Expert » Mon Apr 07, 2014 6:53 am

U.S. Water Rockets1 wrote:If you are interested in the descent rate only at the moment of landing, you can also use a reference object in the ground based video. You can see at that frame number the rocket is level with some object of a known height (you can measure it at any time) and then count the frames it takes to reach the ground from that point. The video file will have a set number of frames per second, you can figure out how many seconds it took to travel the known distance and divide to get feet per second.


I know, although I am trying to find average FPS, that is why I am using my altimeter to shorten the work.


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Re: Acceptable descent profile?

Postby Alien Space Agency » Sun Nov 22, 2015 1:16 am

Wait, PA altimeters are acceptable with descent rate?


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Re: Acceptable descent profile?

Postby bugwubber » Tue Nov 24, 2015 9:14 am

Alien Space Agency wrote:Wait, PA altimeters are acceptable with descent rate?


You have to have an onboard camera so descent rate can be derived from elapsed time.


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Re: Acceptable descent profile?

Postby Alien Space Agency » Wed Nov 25, 2015 7:55 am

But logging altimeters are still required, right?


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Re: Acceptable descent profile?

Postby WRA2 » Wed Nov 25, 2015 10:53 pm

for our altitude competitions logging altimeters are required for the following classes (A, B, and E). Peak altimeters are allowed for Class D.


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