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. 🙂🚀
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"
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.
@@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.
@@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?
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.
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.
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.
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.
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.
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.
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.
@@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.
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.
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
I build a falcon heavy water rocket, the nose is heavy 250gr, it’s almost 1m long, the balance is great but it feels heavy, I hope it’s powerful enough, if I make it lighter than it isn’t balanced anymore
I am really interested in building and flying this kind of rocket . Would you be so kind to give me an Idea about how much money does it take to build the rocket and the launcher and the other equipment needed to launch ..Thanks you really will help me out in my Quest to Fly the rockets ...!
To start off in water rockets you really only need a bicycle pump, some PVC tubing and an old plastic soda bottle. You can make rockets with that setup and fly to a couple hundred feet. You can then progress to larger rockets and more sophisticated recovery systems and more complex payloads. The rockets shown in this video probably cost a couple of hundred dollars each to build. Have a look here for some tutorials on how to get started: www.aircommandrockets.com/construction_index.htm And here are some more articles on it: www.aircommandrockets.com/article_index.htm
It should be posible to increase performance using different a gas. CO2 is very soluble in water . And solubility increases with pressure ... At high pressure the water will hold a lot of CO2 , during 'burn' the pressure goes down releasing more CO2 from the water and this will help keep pressure high ... What about a rocket with petrol as the fluid and pressurized oxygen with afterburner?
It's frankly astounding that this exact propulsion theory has the capability to quadruple our current dV capability. Check out Nuclear Saltwater rockets for more.
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.
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....
Great Test. To get better video of the launch, get further away, and hold the camera in your hands with your arms straight. Follow the rocket accent with your arms straight and camera below your eyes. Keep from moving the camera off the rocket as much as possible. Post process the video putting a red circle around the rocket while in the sky as otherwise it is invisible due to the low resolution of the video image.
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.
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.
wait, hold on a second. If you drive on the underside of the road, why are you having so much trouble with these rockets? Just put them in the street and let them fall into the sky?
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.
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.
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 😀
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.
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.
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?
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 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.
Noise due to expansion of the High Pressure Air into the lower pressure Rocket. This delta Pressure (feed pressure - rocket pressure) decrease as loading of air continues, less expansion equals less noise. Initially, the delta-P across the expansion Valve is high enough to produce Supersonic Flow, the Mach number of this flow decrease as delta-P decreases. Are you going to try charging your rockets with CO2 instead of air? Should be able to increase engine performance with more expansion in the "engine bell" of the motor. Supersonic CO2 expanding to accelerate the Water, yielding higher exhaust velocities.
Interesting, I would have expected choked flow for almost the entire fill. We have not done CO2 experiments yet, but yes CO2 will give you better performance due to its higher molecular mass. The problem with CD nozzles is that they are only effective during the gas phase of the thrust, but can be slightly detrimental during the water phase. This is why water rockets typically don't use them.
I love the water rockets. I had a 2 stage set back in the sixties, that had a launch pad and remote control panel with pressure guage, pump and release control built in. I wonder if anyone uses high pressure steam, instead of air or air & water? It would of course be dangerous and definitely not a child or beginners setup.
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.
Not an expert,just a thought... If you've used a saline solution,with maximum ammount of dissolved salt,would the higher density water be better for propulsion?
Higher density liquids don't necessarily give you more altitude. Although it will generate higher thrust, you are also having to lift a heavier liquid that is still in the rocket. Here is a detailed look at this: ruclips.net/video/Fu3rIiPy_18/видео.html
Why the Rocket COUD have Crashed. If the Parachutedor doesn't open at uperg G the rocket speed up again. the air rushing against the Parachutedor coud force it closed . I had the same Problem befor
The servo motor never activated. We found that part of the servo motor still in the locked position. If it was unlocked then air flow actually helps to open the parachute door with this design.
Out of curiosity, why not use heated water. Ie water, heated in the rocket while under pressure. Adding a small expansion zone, prior to the bell, you could probably flash to steam on exit from expansion chamber from pressure differential and the stored heat energy of the water. You'd need less water volume for the same static thrust and could potentially maintain thrust for more than 1/2 a second. This is just something I thought while watching the video and recalling a boiler explosion I was once witness to. It may have been done already, I know little about this, and you obviously do it this way for a reason. I just don't know what that is.
What you are referring to is called a steam rocket. These exist and people have flown them, but it is a different kind of propulsion method to a traditional water rocket. Water rockets don't rely on a phase change for propulsion like steam rockets do. Traditional water rockets just use a cold compressed gas to push on a cold liquid. Steam rockets certainly have their challenges mostly in making a pressure chamber that can also withstand the heat and be lightweight at the same time.
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.
First, at 4:10, what kind of spider is that? I've never seen one like it. Second, suppose you used a propellant denser than water? Would that add to or detract from the altitude achieved? On the one hand, you're pushing more mass out the nozzle, but on the other, you need to lift more mass.
Have no idea what spider that is. There was a huge variety of spiders on the field. Very good question about the density of the water, and good insight why denser liquids don't necessarily translate to higher altitudes. We looked into this a couple of years ago, here is a video where we did some experiments with different densities: ruclips.net/video/Fu3rIiPy_18/видео.html
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.
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
we have a lot of large farms here our family owns 90km² and that's barley coincided a medium size farm. there are farms well in to the 1000km² and over range literally takes an hour or so to cross at high way speeds 100km/h / 60mph. when moving large equipment like air seeders even on our medium size farm it can take 30 mins to get form one side to the other that's with all the gates open be for you get to them its handy having little brother🤣
Fun Fact : the largest farm in Australia is Anna Creek at 5,850,000 acre / 23674.1km² / 9140 mi² that's about 2 times the size of New York or almost 4 times the size of LA going off 2015 stats.
None of the gases we use go liquid at these pressures. Although using CO2 gives you better performance compared to air because of it's higher molecular mass.
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!
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.
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.
So nice video again i love to see fly the rockets again , but suddently a spider YaY!! Im arachnofobic !! Poor rocket, but yes sometime can chras happend. And so awesome place you living. Greeting from Hungary Sopron !!
@@AirCommandRockets Probably I would send someone for the rocket ,or just build an other ha ha ha. Im building water rockets too but I make aerodinamic cover from spotwelded aluminium cans shiny side , looks great , but not so far advanced as your work.
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.
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.
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.
@@AirCommandRockets The radios normally use an 18650 Li battery, but that gets about a week of operation. For the duration of the flight, anything that puts out about 3.5V would work. I have the ones based on the t -beam v1.1 modules. You wouldn't have to mount the oled display. What is cool about it is that there is a mobile phone app that talks to a nearby module which shows the location of all the others on a map w/ distance (so you could have one on the rocket, plus one next to you). Good luck, I think you have a really cool project here.
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.
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. 🙂🚀
The underside of the road!!!! HAHAHAHA love it!
🙃
Here in Oregon the entire show was upside down till the last scene 🤣 kidding.
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
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.
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.
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?
The damage to the launcher really illustrates how much forced you've packed in there
1000psi is NOT to be messed with
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.
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.
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
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.
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
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
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.
Great as always! Sorry for the rocket, hope you can recover it.
Slyšel jsem češtinu! :) Skvělá videa, díky
It's about time someone shows the real view "Down Under" ......
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.
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.
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
I build a falcon heavy water rocket, the nose is heavy 250gr, it’s almost 1m long, the balance is great but it feels heavy, I hope it’s powerful enough, if I make it lighter than it isn’t balanced anymore
I am really interested in building and flying this kind of rocket . Would you be so kind to give me an Idea about how much money does it take to build the rocket and the launcher and the other equipment needed to launch ..Thanks you really will help me out in my Quest to Fly the rockets ...!
To start off in water rockets you really only need a bicycle pump, some PVC tubing and an old plastic soda bottle. You can make rockets with that setup and fly to a couple hundred feet. You can then progress to larger rockets and more sophisticated recovery systems and more complex payloads. The rockets shown in this video probably cost a couple of hundred dollars each to build. Have a look here for some tutorials on how to get started: www.aircommandrockets.com/construction_index.htm
And here are some more articles on it: www.aircommandrockets.com/article_index.htm
It should be posible to increase performance using different a gas.
CO2 is very soluble in water . And solubility increases with pressure ... At high pressure the water will hold a lot of CO2 , during 'burn' the pressure goes down releasing more CO2 from the water and this will help keep pressure high ...
What about a rocket with petrol as the fluid and pressurized oxygen with afterburner?
It's frankly astounding that this exact propulsion theory has the capability to quadruple our current dV capability.
Check out Nuclear Saltwater rockets for more.
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.
australian rocket program :D
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....
Great Test. To get better video of the launch, get further away, and hold the camera in your hands with your arms straight. Follow the rocket accent with your arms straight and camera below your eyes. Keep from moving the camera off the rocket as much as possible. Post process the video putting a red circle around the rocket while in the sky as otherwise it is invisible due to the low resolution of the video image.
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.
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.
You should also put something to measure how many Gs it's pulling on take off.
The rocket does around 80G on launch.
The volume decreases as it fills because the incoming air is slowed by the backpressure so the frequency of the sound is smaller
wait, hold on a second. If you drive on the underside of the road, why are you having so much trouble with these rockets? Just put them in the street and let them fall into the sky?
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.
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.
Underside of the road, I knew it! You guys just flip your videos over and act like nothings different.
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 😀
Enjoyed the video. Do Australian cars have cup holders inverted and affixed to the car headliner?
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?
Zdravím Čechy, zaslechl jsem ve videu češtinu.
Noise is proportional to flow rate. More back pressure in the rocket means less flow >> less noise
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.
At the end of the video, flat earthers are like see, I told you so.
That nearby hill AND those patterns in the land at 2:58 ARE intriguing, too
Use multistage with ejection spring load to gain thrust from inertia
Differential pressure and flow rate would be my first evaluation of the loading noise difference.
The sound reduces because the rate of flow decreases as the pressure differential reduces
Come on by yourself drone man find more fun that way 200 buck good one
Just remove the parachute and you have an even more extreme variation of lawn darts
Thumps up for the rocketsand another on for the unterside of the road
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.
I would like to see 5x 500mL drinking cans used
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?
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 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.
What would a steam rocket 🚀 do 🤔 research time.
I loved all the propaganda right up until 10:04 :)
teacher : no running on the side of the pool !
me : 1:21
Noise due to expansion of the High Pressure Air into the lower pressure Rocket. This delta Pressure (feed pressure - rocket pressure) decrease as loading of air continues, less expansion equals less noise. Initially, the delta-P across the expansion Valve is high enough to produce Supersonic Flow, the Mach number of this flow decrease as delta-P decreases. Are you going to try charging your rockets with CO2 instead of air? Should be able to increase engine performance with more expansion in the "engine bell" of the motor. Supersonic CO2 expanding to accelerate the Water, yielding higher exhaust velocities.
Interesting, I would have expected choked flow for almost the entire fill. We have not done CO2 experiments yet, but yes CO2 will give you better performance due to its higher molecular mass. The problem with CD nozzles is that they are only effective during the gas phase of the thrust, but can be slightly detrimental during the water phase. This is why water rockets typically don't use them.
I love the water rockets. I had a 2 stage set back in the sixties, that had a launch pad and remote control panel with pressure guage, pump and release control built in.
I wonder if anyone uses high pressure steam, instead of air or air & water? It would of course be dangerous and definitely not a child or beginners setup.
There have been a number of steam rockets built. Here is a really well engineered one: ruclips.net/video/zLjaBDZ2J2o/видео.html
you must have very stick tyres in Australia.
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.
Not an expert,just a thought... If you've used a saline solution,with maximum ammount of dissolved salt,would the higher density water be better for propulsion?
Higher density liquids don't necessarily give you more altitude. Although it will generate higher thrust, you are also having to lift a heavier liquid that is still in the rocket. Here is a detailed look at this: ruclips.net/video/Fu3rIiPy_18/видео.html
Why the Rocket COUD have Crashed. If the Parachutedor doesn't open at uperg G the rocket speed up again. the air rushing against the Parachutedor coud force it closed . I had the same Problem befor
The servo motor never activated. We found that part of the servo motor still in the locked position. If it was unlocked then air flow actually helps to open the parachute door with this design.
Out of curiosity, why not use heated water. Ie water, heated in the rocket while under pressure. Adding a small expansion zone, prior to the bell, you could probably flash to steam on exit from expansion chamber from pressure differential and the stored heat energy of the water. You'd need less water volume for the same static thrust and could potentially maintain thrust for more than 1/2 a second. This is just something I thought while watching the video and recalling a boiler explosion I was once witness to. It may have been done already, I know little about this, and you obviously do it this way for a reason. I just don't know what that is.
What you are referring to is called a steam rocket. These exist and people have flown them, but it is a different kind of propulsion method to a traditional water rocket. Water rockets don't rely on a phase change for propulsion like steam rockets do. Traditional water rockets just use a cold compressed gas to push on a cold liquid. Steam rockets certainly have their challenges mostly in making a pressure chamber that can also withstand the heat and be lightweight at the same time.
I like it very much. Down Under.
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.
First, at 4:10, what kind of spider is that? I've never seen one like it. Second, suppose you used a propellant denser than water? Would that add to or detract from the altitude achieved? On the one hand, you're pushing more mass out the nozzle, but on the other, you need to lift more mass.
Have no idea what spider that is. There was a huge variety of spiders on the field. Very good question about the density of the water, and good insight why denser liquids don't necessarily translate to higher altitudes. We looked into this a couple of years ago, here is a video where we did some experiments with different densities: ruclips.net/video/Fu3rIiPy_18/видео.html
2:20 it like evaporated
It sure gets off the pad quick. :)
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
I think there will be a lot less traffic on "the other side of the road"...hahaha
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.
that's a bigass pencil you got there
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: ruclips.net/video/Gqm9xIJp9ms/видео.html
Impressive Fields in Australia ^^
Yup lots of space here. A lot of the fields seen in the video even from apogee are owned by the one farmer.
we have a lot of large farms here our family owns 90km² and that's barley coincided a medium size farm. there are farms well in to the 1000km² and over range literally takes an hour or so to cross at high way speeds 100km/h / 60mph. when moving large equipment like air seeders even on our medium size farm it can take 30 mins to get form one side to the other that's with all the gates open be for you get to them its handy having little brother🤣
@@phalanx3803 Where is "here"?
@@AirCommandRockets i was talking about Australia as whole. my farm is in the Mallee.
Fun Fact : the largest farm in Australia is Anna Creek at 5,850,000 acre / 23674.1km² / 9140 mi² that's about 2 times the size of New York or almost 4 times the size of LA going off 2015 stats.
How about a cannon that launches the rocket?
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.
Wow the acceleration is amazing
Guys, are you from Czech Republic? Because at 7:26, this sir was speaking Czech.
Původně z Prahy. :)
Surprised you don't have a spotter downrange to save search and retrieval time🤔
It's usually all hands on deck to get the rocket prepped and launched.
Perhaps instead of 'air' use nitrogen or another pure gas that will not go liquid itself at the pressures you are using?
None of the gases we use go liquid at these pressures. Although using CO2 gives you better performance compared to air because of it's higher molecular mass.
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 :)
I had no idea water rockets could be so high performance.
Do you have a G-load tracker? If so, what was max rating?
Acceleration is in the order of 80G
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.
10:03 Lol funny. upside down.
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.
So nice video again i love to see fly the rockets again , but suddently a spider YaY!! Im arachnofobic !! Poor rocket, but yes sometime can chras happend. And so awesome place you living. Greeting from Hungary Sopron !!
Thanks! :) There were so many spiders on the field, literally hundreds of thousands, and you had to walk through their webs to retrieve your rockets.
@@AirCommandRockets Probably I would send someone for the rocket ,or just build an other ha ha ha. Im building water rockets too but I make aerodinamic cover from spotwelded aluminium cans shiny side , looks great , but not so far advanced as your work.
Y'all need a flame diverter.
Hey there, I love your rockets and videos.
Cheers! :)
How about a two-stage rocket?
Is there some book about thermodynamics of water rocket?
This has a good analysis of how water rocket thrust works www.et.byu.edu/~wheeler/benchtop/pix/thrust_eqns.pdf
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.
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.
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.
You could put one of the meshtastic LORA radios in it. They have GPS and the LORA radios will easily cover the distance.
Thanks for the suggestion, I will have to investigate this further as it certainly seems a plausible solution.
@@AirCommandRockets The radios normally use an 18650 Li battery, but that gets about a week of operation. For the duration of the flight, anything that puts out about 3.5V would work. I have the ones based on the t -beam v1.1 modules. You wouldn't have to mount the oled display. What is cool about it is that there is a mobile phone app that talks to a nearby module which shows the location of all the others on a map w/ distance (so you could have one on the rocket, plus one next to you). Good luck, I think you have a really cool project here.
10:05 take that, flat earthers!
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.