High Pressure Water Rockets
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- Опубліковано 28 лип 2024
- Water rocket highlights from our recent trip to Mullaley, NSWRA's high power launch site. We launched Dark Shadow at its highest pressure to date at 1000psi and also the Nova water rocket at 450psi.
- Наука та технологія
Update 29/5/21: I've managed to fix the altimeter by replacing the LCD screen and hooking up a new battery. I was able to read off the altitude for the Nova rocket that crashed. The altitude was 1,445 feet or 440m. Not bad for a little rocket.
So glad that you turned the camera the right way up at the end! It's been over 50 years since I left Sydney, and I'm still not used to watching British TV the wrong way up!
Shame about the lawn dart. But hey, ho; there'll be another day. 🙂🚀
Anyone who is a decent age can probably remember the old water-powered rockets from the 70's and 80's. To this day, that is one of the coolest toys I ever had. It also taught me to understand the mechanical aspects of the machine and how to repair it. Sorry - nostalgia is a powerful emotion when you begin to age.
yes, me too!! I saw my first one at school in 1971 demonstrated in my science class
I had a few of those in I'd guess the early 60's
Great toys - o boy the lawyers would have a field day with those today, uh?
@@garygerard4290 Oh the days of Lawn Darts .Dodging the darts a dodgy drunken uncle had thrown .
I always wanted one of those water rockets when I was a kid if truth be told I'd still love to have one 😁
@@Interdiction we should totally combine then with water rockets.
The underside of the road!!!! HAHAHAHA love it!
🙃
Here in Oregon the entire show was upside down till the last scene 🤣 kidding.
I've been to Australia and driving on the underside of the road takes a lot of getting used to. ;)
That way the drop bears can't get you.
o well at least they drive on the right underside of the road.
When the pressure in the tank rises, there's less delta p to drive flow into the tank and that's probably why it gets quieter as it fills up
Well stated, too. I love a good youtube comment puzzle
i usume jou mean the presure diference gets less each cycle?
came here to comment this, this must be correct. I assume the noise level is proportional to the delta p across the inlet, which most definitely is decreasing. btw delta p = pressure difference. delta just means "difference in"
@@goatgod yes that's what "less delta p" means. delta means difference or change.
@@scotmcpherson yes jep informd me of that thanks
10:04 So that's why your rockets fly so high!
That reverse thing really got me loled
Greetings from Czech Republic. Absolutely love your videos, great work! It really warmed my heart to hear my mother tongue so unexpectedly.
Díky moc :)
@@AirCommandRockets Taky mě to chytlo za uši, slyšet češtinu uprostřed. Jinak super video i rakety
@@AirCommandRockets sir likewise here im your fan. I have a question. How rockets are launched under water like in submarines does it have a different procedure? And can you do it with your rockets while explaining the technicality involved? Thank you.
@@rjgonzalez9220 We did some under water launches a long time ago. Scroll towards the bottom part of the page: www.aircommandrockets.com/day24.htm
@@AirCommandRockets impressively beautiful i hope you can post it on you tube. I notice the rocket is already running beneath the water till it lauch. Can you mimic a submarine lauched rocket were the rocket shoots upward then after it reaches above the water the rocket would ignite its engines and fly. Can this be possible?
As always, very entertaining! Particularly the driving joke at the end - gave me a good giggle! Looks like you need a checklist to not forget things like opening the cylinder, etc. Pity about the wind and the offering to the gods! Great to see you guys out there again!
Thanks Willie, yeah about that checklist .... it would help if I remembered to bring the printout! :) I need a checklist for my checklist. The wind on the following day was even worse, and although we put our high power pyro rocket out on the pad, we decided against launching it. I'd say the wind was closer to 35km/h at times. Most other people also decided against launching theirs.
Didn't expect you here, astro guys like rockets too :D Love your channel
When I was a kid in the 60s we had toy rockets you would fill it a quarter with water and attach it to a hand pump/launcher. Loads of fun, probably don't make them anymore.
Me, too!!
We made our own with coke bottles.
@@africanelectron751 yes coke bottles and air compressor ours would let go at 45psi
They do still make these. Look on amazon.
Had one in Germany in 1951, was 6 years old then.
The damage to the launcher really illustrates how much forced you've packed in there
1000psi is NOT to be messed with
That nearby hill AND those patterns in the land at 2:58 ARE intriguing, too
The decrease in volume is likely caused by the increased chamber pressure. Higher pressures prevent the vibration (deformation) of the chamber and thus attenuate the sound.
It must be something along those lines.
As the pressure in the tank rises, the velocity of the air decreases.
@@spacemanmat good point
About 4:30, my hypothesis is as the rocket is filled, the pressure differential between the scuba tank and rocket decreases, resulting in slower, less violent air flow.
Bingo
4:41 As the pressure gradient between the gas tank and the rocket reservoir gets lower, the gas enters the rocket reservoir at a lower speed and therefore less energy can be converted from the slower moving gas to sound resulting in the noise dropping as filling progresses.
Also, there is shampoo in the water tank. As the gas enterest, it creates water bubbles. These bubbles dampen the sound as well.
The audio variance is a function of volumetric density. Audio travels at a different amplitude as the density increases.
Also, the natural frequency of the hollow space (compressible void) increases (like how the tone rises when blowing into a filling bottle), allowing for less lower tones to oscilate.
@@theGoogol It's a resonant body and the available space will influence volume.
@@fakshen1973: Exactly :) It also has an effect on the container (like how a half filled bottle sounds different when struck on the empty part and when struck on the full part). It's a very complex system of pressure vs volumetrics vs harmonics vs material properties. It's equally amazing that these factors are pre-calculated and accounted for in modern day high tech.
The decrease in sound volume recorded during pressurization is due to the incoming air not compressing or expanding as much when the pressure is higher.
Woah this is so impressive, the engineering, the electronics, the maths. This is the first video I've seen of water rockets and this seems awesome!
Best thing of all I stumbled across some fellow Australians! Hey from Far West NSW!
Thanks. Water rockets can be highly addictive :)
Each time the rocket is pressurized there is less of a pressure differential between the rocket and the air cylinder, so the flow velocity into the rocket is likely reduced.
I believe that the sound is more likely lowering in volume because as the tank is pressurized the walls become stiffer and make it harder for sound to travel through it. I think the sound comes from the bubbles of air gluging up through the water so another explanation could have to do with the speed the bubbles rise at different pressures though you can test my first guess by flicking the tube at 100 psi then repeating it as you increase pressure.
@@evilcanofdrpepper I think you're sort of right, the tank wall is like a bell, the increased pressure acts as a brace for the walls of the tank, and dampens it s resonance. that plus the reduced pressure differential I'd say. technically a stiffer wall should let sound 'through' more easily, the way a well pumped bike wheel lets you feel more of the road surface in the ride. then again im not a professional in any sense.
Slyšel jsem češtinu! :) Skvělá videa, díky
I believe the decrease in tone recording is because of a decrease in the volume of air being able to pumped in due to resistive pressure. Cheers, Billy in Canada
Nice to see you back!
You take water rockets to a whole new level and I respect that
Cheers. :)
amazing... thank you George...it has been a long year and a half... looking forward to the next set of videos... cheers!
Thanks Stu. :) We're working on the next video at the moment.
Great as always! Sorry for the rocket, hope you can recover it.
Love your work George.
Wooo! Another sick ACR video! Glad to see you guys getting to go out and launch HPR again, last year was pretty rough.
Yeah, it was really nice to get out of Sydney for the weekend and go to a wide open paddock and play. :)
1) the sound goes less loud because the tension caused by the pressure build up makes the shell much more rigid ergo less vibrations.
But would you expect a higher pitch? like stretching a guitar string? The pitch really didn't change.
Loved seeing this in action!!
As to timemark 4:30, as the pressure in the rocket increases, the flow rate of gas slows down and thus quieting it. Thanks for your video. Blessings to you.
4:41 I'd guess the reason the sound gets quieter as the pressure rises is due to the changing impedance of the air inside. When sound passes from one medium to another, it experiences attenuation (reduction in amplitude) due to impedance mismatching. Initially, the air inside the rocket is at atmospheric pressure, so the impedance is the same inside and out. As the pressure rises, the impedance will change, resulting in amplitude losses as the sound is transmitted through the rocket.
Amazing job guys!
Very well done!
Thanks :)
I think the volume goes down as pressure is added because it changes the resonance frequency of the model due to internal stresses. Similar to how a piano or guitar string changes in sound as it gets tightened.
The volume decreases as it fills because the incoming air is slowed by the backpressure so the frequency of the sound is smaller
As pressure inside the rocket rises it comes closer to equalization with the supply tank. As they equalize the rate of flow decreases. You're initially hearing a high rate of transfer, but as the rocket fills the flow rate decreases. If allowed to continue without theoretically exploding - the air flow will decrease and decrease to a zero flow when both tanks are equalized.
The filling noise decreased in subsequent bursts as the delta decreased; the greater resistance of higher pressure inside the reservoir reduced the flow rate. Less flow = less noise.
This seems the be the consensus with people commenting here. It makes a lot of sense.
The pressure difference across every bit of your pressurising system decreases as the rocket pressurises. So the mass flow rate reduces, flow velocities decrease, turbulence reduces, noise reduces.
The noise decreases as the pressure builds, as I ponder, because there is more air inside. Each pump represents a smaller percentage of the total air. It also moves slower because it's compressed to a smaller size.
Nice footage from the onboard camera.
Differential pressure and flow rate would be my first evaluation of the loading noise difference.
Very cool, much more sophisticated than the plastic toys of the 60’s that I had fun with!
As the air is pressurized inside the tank, this decreases the velocity from the new air coming in. The decrease in velocity means a lower Reynolds number in turn resulting in a more laminar flow for the Fuild(air) resulting in less noise
the sound is the high velocity flow along the tobes, small high frequency vibrations caused
I agree it's the air flowing through the launch tube that causes the sound. It sounds metalic
Awesome work!
Enjoyed the video. Do Australian cars have cup holders inverted and affixed to the car headliner?
fantastic documentation of the flights! well done.
Cheers! :)
Regarding the pattern of decreasing amplitude you saw in the sound waves during pressurization pulses-I wonder if it’s because the stiffness of the pressure chamber’s outer wall increases as you add pressure, such that the walls can’t resonate as much with each subsequent pulse?
i loved this video, i will wait for the next horizon part
Hey there, I love your rockets and videos.
Cheers! :)
You need a long nozzle to expand the water into bubbles before it comes out and you can't get work from it anymore. As soon as the pressure is released, a wave of bubbles propagates from the nozzle exit inwards. Within a microsecond your entire water volume becomes a dense foam.... problem is you also already kicked it out during launch.
The decrees in volume that the microphone picks up is due to a reduction in the flow rate of air in to the rocket as the pressure increases. That thing get off the ground in a hurry, nice work!
teacher : no running on the side of the pool !
me : 1:21
I have no real clue but I would assume that as the pressure got higher, so does the density, muffling the sound more.
Hello George, nice launch's and nice flight ! It's amazing ! Bravo !
Thanks Francois, and Happy new year!
Absolutely george best wishes for health and happiness to you and your family!
I've always wondered how the angular momentum increases as the distance from the axis of spin increases.
Best of luck for future projects..Luv watching your videos..cheers.
Cheers! :)
I think the noise reduction may have been to a lower flow rate as the potential was decreasing as the pressure was increasing in the rocket. Since the pressures were closer to equal as from the incoming and actual pressure. Less flow, less noise
Amazing video!
4:36 I think the reason the volume decreases, is the energy comes from the difference in pressures between what is in the vessel, and what is coming from the tank. as the pressure gets closer to equivalent, there is less force driving it in?
The foam streaks that Nova leaves in the sky are really impressive. Have you been tailoring the profile of the nozzle to optimize the expansion ratio?
Thanks Dan. No, the nozzle is just a straight through 7 mm hole. Expansion nozzles are planned for a test campaign probably sometime after we finish our Horizon rocket.
As the pressure in the rocket increases the infill speed that the air is traveling at from the scuba tank to the rocket drops slower and slower until both the rocket and the air tank are at the same pressure then there is nothing pushing the air either way so the flow would stop completely, that is why it gets quieter as it fills, the speed of the air is slowing down so its not as noisy, I trust this makes sense 😀
Great stuff!
Noise is proportional to flow rate. More back pressure in the rocket means less flow >> less noise
The back pressure on the fill valve acts like a shock absorber for the fill resonance
did you ask why the burst's sound level drops as the tank is filled? its either because your rocket is being filled from a reservoir tank which has been pressurized appreciably close to equilibrium with your rockets target fill pressure or alternately, if being filled from a source with a near constant flow rate, the chance for cavitation to occur during the turbulence of the fill decreases as the overall pressure rises distantly from vacuum. (source: my pumps quiet down as i raise the net positive suction head)
The pressure is going from 10L 3000psi tank to ~5L volume (air volume) at 1000psi. So yes there is definitely a drop in the flow rate as it gets fuller.
Wow the acceleration is amazing
I had no idea water rockets could be so high performance.
Maybe the sound-volume decreases because the pressure stiffens up the tank?
I mean: when there is no pressure in the tank, the incoming air flow has an easy time vibrating the tank walls, but as presure builds up the tank walls are becoming ever so stiff, and it is harder to vibrate them.
The volume probably decreased due to the pressure difference. When the rocket is at low pressure a lot of air can flow in as there is little to no resistance. As pressure in the rocket increases the pressure difference is less. Meaning more reisistance to air flowing to air going into the rocket and less available room for the new higher pressure air.
Good works! Are you sure it has lost battery connection instead of mechanical jammed? In your experience what's the best parachute deployment you ever built?
We don't know the root cause of the failure. I know the circuit had power as I checked the Armed LED before launch, and the part of the servo motor that we recovered with the servo horn, it was still in the locked position, so the servo never moved. The best parachute deployment we use is the one on our regular low pressure water rockets. It has flown hundreds and hundreds of times with only very rare fails.
Great video. I hope the rocket gods were appeased.
The sound reduces because the rate of flow decreases as the pressure differential reduces
I think the sound of the pressurization decreases as it's pressurized and the pressure leaves the body less free to resonate and transmit the sound?
It's about time someone shows the real view "Down Under" ......
looked like fun. The ride home made me laugh.
how good! cheers!
At the end of the video, flat earthers are like see, I told you so.
q and a
apogee - is this the same when i shoot arrows up and they seem to hang for sec before tipping over
Apogee just means the highest point of the flight measured in meters or feet above ground. Arrows behave very similarly to rockets near apogee where they slow down to low speed before accelerating again.
Why more noise as the pressure builds up?? My grand mother used to say "empty barrels make a lot of noise as full ones stay silent". Density while increasing the speed of sound attenuates it's amplitude.
I saw this really tiny GPS module. I thought maybe you might be interested. It's called the 'Diatone Mamba GPS/Beidou M220'. 4.9g maybe it will reduce weight too.
Thanks for the suggestion. We would still need to pair it with a transmitter to transmit the co-ordinates back to a home base receiver.
Great Work 👍
Thank you Marcel. :)
nice!! why not launch it with an angle against the wind direction?
When you are going for altitude, you want to point it up. The rocket will naturally want to point into the wind as it flies so it flies up range somewhat before the parachute deploys. If we wanted easy recovery then yes, pointing it into wind would help with that.
Can you use something like a JollyLogic chute release so you don't drift as far?
That is certainly an option, but we would need a drogue chute to slow it down before releasing the main. Drogue-less recovery isn't an option for this rocket design. The chute release and drogue add weight though, so on record attempts that would be a penalty.
As you so eloquently pointed out, you were driving on the underside of the road. BUT, you were also launching your rockets down, not up. :)
really cool!
When pressure increases the flow of air reduces so less sound.
Impressive motor!
I'm new to the hobby, is there any water additive to encourage laminar flow? In hydraulic fracturing (oil field fracing), we use a "friction reducer" to reduce turbulent flow in the well bore.
The friction reducer is a slurry of polymer chains (guar) and surfactants. It will increase the viscosity slightly (5 cp max).
I would think this would result in a higher specific impulse, and therefore higher alt. with the same reaction mass and pressure.
This is a really interesting question. We do use a detergent to generate foam inside the rocket that does give a boost in performance. But I have not considered it terms of encouraging laminar flow. It would be interesting to do a comparison between foam and non-foam with just the detergent dissolved in the water.
Love your videos. I can't wait to see horizon launch :D
What cameras do you use in your rockets?
Thanks Tom. We use the 808 #16 V3 keychain camera, and now also the Mobius Mini V2 HD camera.
@@AirCommandRockets Thanks! I'm building my own rocket with my daughter. I have a cheap go pro clone which is light(ish) but bulky, these look perfect.
Why not a "grounded" first stage? Basically power the very first "take off" as a ground based water source. Almost a "gun" first stage?
This initial motion to be followed immediately by what would have been the first stage, as the mass of the rocket starts moving from the ground based propellant.
That's kind of what the launch tube does that goes up through the nozzle. It acts as a piston so that the rocket gets some initial velocity before it starts using air and water. A launch tube can add 10-15% more altitude. That is what we are using here.
Great video!! Have you ever experimented with liquids of different viscosities? It would be interesting to see everything from soda pop to maybe a light mineral oil and their affects on flight.
We have not tried different viscosities specifically, but have done different densities. ua-cam.com/video/Fu3rIiPy_18/v-deo.html Each of the liquids I guess also has a different viscosity.
@@AirCommandRockets for a straight forward thruster
H2O is much better than CO2 or N2 since it has 155sec isp
But in the study they did not mention what temp was the water or to what psi was it compressed
According to your rockets what is the isp you are getting and at what lressure exactl?
@@FirstLast-tx3yj That sounds like a steam rocket. Where the water changes from liquid to a gas. This is a different kind of water rocket. Cold gas acting on a cold liquid.
4:34 if the microphone is located on the tip of the rocket and the water is being filled from the bottom it might be that the sound has to travel trough more water that “absorbe” the sound as it fills up. This seems very simple to explain so I doub i got it right :P
No water flows into the rocket, the rocket already has all the water in it before we start pressurising.
What's the detergent for? Does lowering the surface tension of the water improve efficiency?
It improves performance because it allows us to create foam. Here is some more information on it: ua-cam.com/video/Gqm9xIJp9ms/v-deo.html
warm water(high vapour pressure) and cold water sounds different when agitated or poured maybe the same thing can be pointed out here
The water temperature doesn't change much during the pressurisation, perhaps 1 or 2 degrees at most? There is a fairly small contact area between the warm air and the water.
For the Nova rocket, what kind of low pressure hose do you use ?
We use a scuba LP hose. These particular hoses were designed for scuba hookah diving.
Would a colored smoke generator make it easier to find the rocket? As the chute deploys the smoke generator comes on? I'm not sure if that's feasible. But considering the propensity for damaged electronics on landing, the smoke canister might be a little more reliable on a hard landing. Also the trail of smoke would be easier to locate as the rocket comes down.
That would certainly make it easier to find, but the weight of the smoke generator could be an issue. I don't have direct experience with smoke generators, but if it is something that is burning, (even internally)? This may be an issue if it was to start a fire on landing.
The volume of the audio decreases as the pitch becomes higher frequency.
Bass Sinewaves have a greater geometric area than shorter wavelength high frequencies.
(The reason why you can hear your neighbours bass speakers, but not the tweeters!)
The higher the pressure in the vessel, the faster the wave propagates and oscillates through it, so the pitch will increase.
I think added to that effect is also that the walls of the rocket become more and more loaded as the pressure rises, so they both have a higher eigen-frequency (higher pitch vibration) and a much smaller amplitude for the same force input due to increased spring constant.
That is very impressive.
Water rockets are cool! About the sound. Sound is air in motion right? The onboard camera mic records the normal ambient sound but also records some vibration/resonance . Putt a action cam in one of those underwatercasings an put it on a helmet and walk around. You hear thump-thump-thump, but hardly any talking. I believe that as the pressure increases the pressurevessel material gets under increasing tention and vibrates less (= less air in motion). And less vibration, less vib/res transported through the physical structure it self into the mic. Just my thougts about it, im not well educatet or anything.
Do they angle it into the wind? they should.
The rockets tend to do that themselves. It is called "weather-cocking" the cross wind tends to push on the fins more than the nose, and causes the rocket to pitch over in flight into the wind.
if you are adding more air it takes more energy to move the air its like pushing 1 lead ball or 6 it atleast will change its frequincy (Maybe throw it in a FFT? see if the frequincy only changes) also i see matthew alderfer's answer that is also pretty likely....
hmmm noise volume decreases as it becoes full... well lets see, in the begining, the volume of air going in is quite a bit, thus alot of noise generated, as the pressure increases inside the volume of air rushing in has diminished aking less noise... hows that for a hypothesis?? ;)
Great informative video
Cheers