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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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1500g Weight Limit

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bugwubber
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1500g Weight Limit

Post by bugwubber » Fri Sep 20, 2013 9:40 am

So a year into things and I think it is finally starting to sink in.

1500g limit means I should only be loading LESS than 1.5 liters of water into any water rocket.

How much less is determined by the weight of the rocket.

Which in turn means I should plan for rockets that are 6 liters or less in volume.

WRA am I interpreting that correctly?

Bugwubber


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arjan
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Re: 1500g Weight Limit

Post by arjan » Fri Sep 20, 2013 10:16 am

bugwubber wrote:So a year into things and I think it is finally starting to sink in.

1500g limit means I should only be loading LESS than 1.5 liters of water into any water rocket.

How much less is determined by the weight of the rocket.

Which in turn means I should plan for rockets that are 6 liters or less in volume.

WRA am I interpreting that correctly?

Bugwubber
Hi Bugwubber,

Rule number 1 from the single stage competition rules:

Rocket mass cannot exceed 1,500 grams. This is the total dry weight of all flying components in a flight ready condition including the pressure vessel, fins, nosecone, payload bay, camera, altimeter, flight computer, deployment system, batteries, and nozzle (no reaction mass).

So in the WRA2 rules the reaction mass is not included in the 1500 grams maximum weight.


Arjan

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Team Seneca
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Re: 1500g Weight Limit

Post by Team Seneca » Fri Sep 20, 2013 10:29 am

bugwubber wrote:So a year into things and I think it is finally starting to sink in.

1500g limit means I should only be loading LESS than 1.5 liters of water into any water rocket.

How much less is determined by the weight of the rocket.

Which in turn means I should plan for rockets that are 6 liters or less in volume.

WRA am I interpreting that correctly?

Bugwubber
It seems clear to me that rule says for water rockets the weight limit is 1500g for the empty weight of the rocket.


Bill W.
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bugwubber
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Re: 1500g Weight Limit

Post by bugwubber » Fri Sep 20, 2013 12:17 pm

Team Seneca wrote:
bugwubber wrote:So a year into things and I think it is finally starting to sink in.

1500g limit means I should only be loading LESS than 1.5 liters of water into any water rocket.

How much less is determined by the weight of the rocket.

Which in turn means I should plan for rockets that are 6 liters or less in volume.

WRA am I interpreting that correctly?

Bugwubber
It seems clear to me that rule says for water rockets the weight limit is 1500g for the empty weight of the rocket.
Oh ok, misreading too much lately then.


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Re: 1500g Weight Limit

Post by bugwubber » Fri Sep 20, 2013 12:20 pm

Guess I could have answered my own question by reading the entire statement...

Rocket can be any shape or size but cannot exceed 1,500 grams. This is the total dry weight of all flying components in a flight ready condition including the pressure vessel, fins, nosecone, payload bay, camera, altimeter, flight computer, deployment system, batteries, and nozzle.(no reaction mass) A heavy mass falling from high altitude can be very harmful to persons or property.


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Re: 1500g Weight Limit

Post by bugwubber » Fri Sep 20, 2013 1:01 pm

The source of my confusion came from reading NAR, FAA, NFPA rules and trying to understand how they reconcile with WRA. Did this drive y'all nuts?

NAR:
Size. My model rocket will not weigh more than 1,500 grams (53 ounces) at liftoff and will not contain more than 125 grams (4.4 ounces) of propellant or 320 N-sec (71.9 pound-seconds) of total impulse.

FAA:
(a) Class 1—Model Rocket means an amateur rocket that:
(1) Uses no more than 125 grams (4.4 ounces) of propellant; (ok that's specific)
(2) Uses a slow-burning propellant; (does this remove water rockets from Class 1 definition?)
(3) Is made of paper, wood, or breakable plastic; (does this mean they don't want us to use flexible plastic?)
(4) Contains no substantial metal parts; and (wow could they have used a more vague term?)
(5) Weighs no more than 1,500 grams (53 ounces), including the propellant. (I'm reading this as total liftoff weight)

NFPA:
Water powered, why would they care about water rockets? If we assume that the word propellant (which isn't defined by itself in the NFPA code) means a substance that produces thrust through combustion, water rockets have none. They define model rockets as having "model rocket motors" and model rocket motors must have "solid fuel propellant". Oh and mass launches now have to have expanded safety perimeters? Boy, every world record attempt for multiple launches sure violates that! They also want to discourage people from making "home built" rocket motors. Good thing water rockets don't have motors!


:DH:

Again, I am following WRA rules regardless.


Bugwubber

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