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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.

Quick question regarding water proofing electronics

Discussion about deployment systems including altimeters, timers, air speed flaps, servo systems, and chemical reactions.
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captike
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Quick question regarding water proofing electronics

Post by captike » Tue Jun 26, 2018 3:13 pm

Hello there,
I'm getting started on building an altimeter/parachute deploy system and was doing some research and immediately had a question. On this page: http://www.uswaterrockets.com/world_rec ... ht_log.htm there is a rocket being launched over a lake. How are they protecting the electronics from being submerged in water, but still leaving static ports in the nosecone/payload section to allow the electronics to work measure the altitude correctly? I don't plan on launching over a body of water, but I would like it to be protected from the elements as much as possible while allowing the electronics to still function. Thanks for your time!



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anachronist
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Re: Quick question regarding water proofing electronics

Post by anachronist » Tue Jun 26, 2018 7:19 pm

It's quite possible THAT rocket has a well-sealed equipment bay with a GPS altimeter. When you're going for a record like that, expense is not an obstacle.

For the rest of us, a soda bottle rocket floats very well. If a parachute sets it down gently tail first, the rocket will likely lay horizontal in the water and the electronics won't get wet, provided the components are positioned away from the sides.

There are also sprayable coatings for electronics that will repel water. A product called Nano Protech has a good demo here:

I share your concern, though. I'd rather launch over a lake than over trees, but prefer not to risk the electronics.



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captike
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Re: Quick question regarding water proofing electronics

Post by captike » Tue Jun 26, 2018 7:54 pm

Oh ok...it seemed counter-intuitive to have an "open" bay on a rocket that lands in water. Thanks for the info.



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U.S. Water Rockets
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Re: Quick question regarding water proofing electronics

Post by U.S. Water Rockets » Wed Jun 27, 2018 10:51 pm

captike wrote:
Tue Jun 26, 2018 3:13 pm
Hello there,
I'm getting started on building an altimeter/parachute deploy system and was doing some research and immediately had a question. On this page: http://www.uswaterrockets.com/world_rec ... ht_log.htm there is a rocket being launched over a lake. How are they protecting the electronics from being submerged in water, but still leaving static ports in the nosecone/payload section to allow the electronics to work measure the altitude correctly? I don't plan on launching over a body of water, but I would like it to be protected from the elements as much as possible while allowing the electronics to still function. Thanks for your time!
That particular design uses the most simple technique possible. The pressure port for the altimeter is in an otherwise completely sealed compartment containing the electronics. Water cannot enter the hole and displace the air inside the compartment without air exiting the tiny hole, so the electronics stay dry the same way the inside of a glass stays try when submerged with the top facing down. This method works in ever position except when the port is exposed to the water line, where air and water can come in and go out at the same time. Waves can make this more likely as the water line rises and falls, so we also added a circuitous baffle to the interior of the chamber to create an indirect path for any water that entered the hole from getting to the interior the electronics bay.

Back then, GPS altimeters were cost and size prohibitive, so we had to get creative with the barometric altimeter. Even those were about $100 each, and we did crash a couple of them going for the record. The cameras back then were awful compared to what is around now too, heavy and expensive. We couldn't afford to get that stuff wet, so we came up with these ideas.

Our soft-drink bottle based rockets use the technique described by anacronist, where the large diameter bottles float high mostly above the water line, so the electronics will stay dry if placed near the centerline of the rocket. Sometimes they would get splashed or sprayed but that never seemed to hurt the electronics. Only servos seemed to be affected by splashed water, so we bought a lot and swapped them at the first sign of erratic movement.



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captike
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Re: Quick question regarding water proofing electronics

Post by captike » Thu Jun 28, 2018 12:45 pm

Ahhh, I see. Very ingenious. So the static port is quite small then? Thanks so much for replying. That makes me feel better...I couldn’t wrap my head around how you would accomplish both tasks at the same time.



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