2 Stage Water Rocket - Part 19 - Flight Analysis
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- เผยแพร่เมื่อ 16 มิ.ย. 2024
- In part #19 we have a look at some of the numbers behind the flights shown in part 18. We also compare the flights to simulation results as well as a couple of other observations.
- วิทยาศาสตร์และเทคโนโลยี
![Fc ครับ ขอแนะนำให้รู้จักกับ "น้องเปียโน" l [Nickynachat]](http://i.ytimg.com/vi/HQU6Q_IYTLo/mqdefault.jpg)
You really are a rocket scientist! I'm impressed with the level of detail you are putting into theses videos they just keep getting better!
Cheers :)
Your explanations are so clear and easy to understand. A great resource for people learning about the topic.
What a great TH-cam video. Thoroughly enjoyable! So interesting to walk through the possible reasons for the discrepancies between the sims and the real data. Top stuff.
This is so great George, thanks for sharing. Admire your curiosity and honest, thorough approach to the analysis. Excited to continue following this awesome project.
Thank you Benjamin :)
Man, super interesting. Well done.
I loved your calculation on the Glory phenomenon.
Keep experimenting, maybe you would achieve one day a reusable steam stage without parachute before Arca :)
Thanks for all the informations behind the scenes. Very impressing!
Hi George, the bending of the rocket under pressure might be due to less longitudinal carbon fiber strands on the outside of the bending curve. You could adjust this by laminating carbon roving onto the shell. If you want a stiffer tank section for the next build, you could consider using high modulus carbon fiber. This is a lot stiffer than the usual stuff but has almost no elongation at break. Interesting project, thanks for sharing
Thanks for the info Patrick, will keep this in mind for future builds.
Interesting method of the altitude calculation! Great analysis, new vent holes and ideal expension of the divergent..waiting for the next video!
Cheers Kyiv Rocket Club. We're going to have to do some high pressure tests with the expansion nozzle on the ground first to try to measure the thrust and compare it to a straight through nozzle. That would be something we look at after this project is finished.
Nice! Just found your channel and when I was wishing for an update you uploaded!
I was surprised to see that you only got 3 G acceleration. I would have thought it would have been higher . But 3000 feet is a remarkable achievement, well done sir !
3G? ... the acceleration was ~82G. (16:13)
Brilliant, careful analysis. Really amazing Engineering. I didn't even realise this sort of thing was done!
I love these kind of videos, so interesting to see how you solve problems I would normally just ignore!
"You can probably guess what we need to do to the nozzle to improve performance even further."
Yes, yes I do.
Engine bell
@@handsanitizermk.268 I'm excited to see this! I guess they guys and girls from Air Command Rockets are also happy about experimenting with some sweet sweet engine bells. Although: Could you use some dry ice for pressurization, cooling and maybe some continuous thrust? It might be a step away from an elegant air/water rocket, but maybe worth a try.
@@handsanitizermk.268 the challenge (or maybe not) would be the sealing. I'm thinking of it having a straight cone and the sealing on the smallest part of the nozzle. The coupler for that should match the profile of the nozzle bell. That will add more structural integrity to the rocket, given that this is a second stage.
@@handsanitizermk.268 Yep, the still image shows that the divergent section of the nozzle has an undersized exit diameter since the foam undergoes additional expansion after leaving the nozzle. No need for a "bell" shape. Just a conical divergent section is fine.
That's quite interesting about the foam. I might have to try some experiments.
I personally have deduced that it increased the thrust by extending the time that mass was being ejected from the nozzle [be that right or wrong remains to be tested] as well as a slight acceleration boost, but upon seeing the rate of expansion shown in the still photo, I am under the impression at least a slight additional gain might be further be had from adding a thrust bell to the nozzle assembly. ~( 'w')/
Again...yet to be tested. ~( ,m,)~
Hmmm words NASA has never contemplated, "We need a foam compensated Throat/Nozzle expansion ratio".
Great job!!
i didnt know that a water rocket could have 2 stages,
awesome work!
Although it would come at the cost of diminishing returns, you could in theory have several stages. ~( 'w')/
Its just not very profitable to stack very many of them. ~( ,m,)~
One three stager went 654 feet. That inspired me big time xD
th-cam.com/video/OFAo0QBPVo8/w-d-xo.html
REALLY want to see them put a larger nozzle on this thing and see what better expansion does to the thrust.
Hi, thank's for this interesting video ! :)
The Drag coefficient depends of the speed. You can simulate the drag coefficient with RASAero II. It will give you a curve, not just a value.
Where could I find the Javascript version of the Water rocket simulator ?
Cheers, I'll give RASAero II a go. It's always good to have extra tools. The water rocket simulator hasn't be released yet. I still have some more work to put into it, just have to find the time. When it's finished, I will put it up on the web.
So can we expect a bell nozzle in the future??
Most likely :) We'll have to do some work on the test stand for this.
@@AirCommandRockets I know in sugar rockets it does not take much divergent section to make an improvement in performance, and that a straight conical nozzle is almost as good as a perfectly curved de Lavel nozzle. That foam shot says to me it's time for a better nozzle. I'd be really interested to see the results.
BTW I made the 3d rendering function in Open Rocket and it still always makes me so happy to see it on youtube, especially an amazing project like yours. Great work!
Thanks Bill, :) Yeah, a conical nozzle is what we are most likely to have a go with since they are so much easier to machine. We'll need to update the release head to fit the nozzle, probably seal it in the throat portion of the nozzle. We'll run some ground tests on the test stand first to see how effective it is with the foam.
Nice work on the OpenRocket rendering! :) I use the program quite a bit, mostly for mid/high power rockets.
@@AirCommandRockets Thanks! My work on it is just a little add-on, the other folks do the heavy lifting.
Great job George! To think about rocket shadow and find sun position to determine altitude it is an amazing technique. I would have never thought about that possibility. About foam increasing thrust I think will be easy for you to set some static tests to measure the thrust curve with different % of soap. Maybe is a combination of effects. Soap is heavier than water so when mixed you have some more speed because of viscosity change and a bit more of mass with same volume.
Cheers. The mass increase here due to adding 20mL of shampoo to 2L of water is not significant. It is less than 0.5% more mass. In our case about 10g more compared to the 2000g for the water. I'm not sure how much viscosity plays part, as again the concentration of the shampoo is very low, and viscosity of shampoo is actually higher. I believe most of the benefit is due to the increase in exhaust velocity due to the bubbles expanding as they exit the nozzle.
Hi ! yes of course , I was not aware that soap was in so small quantity. But why soap influence bubble expansion ? If we pressurize water and gas the gas has a diffusion into the liquid. When pressure drops you have the bubbles. It works like sparkling water when you open the bottle cap. Maybe the soap has an influence on gas diffusion into the liquid. More gas into water&soap could mean more bubbles..so higher expansion.
@@PieroAcme With soap there can be probably more bubbles,
which remain from the filling.
I wonder if something more can be done to reduce laminar drag? I'm thinking a surface like shark skin or even dimpled like a golf ball.
Tanks!
Another interesting video George. You seem to be getting great results with your timer calculations, but Is there a reason why you don't use the altimeter to release the chute?
Thanks Derek. That is the long term plan to use the altimeter to release the chute. We have done this before and will definitely need to when it is flying as a two stage since it will be harder to predict apogee. We only have one of the stratologger altimeters that has a pyro output, (the other altimeters we use don't have any output for apogee) and so we only fly the stratologger rarely, as I've been unable to get a hold of a second one.
We find the timer works well for most of the flights so we just use that. The timer is easier to replace than the altimeter. :)
I like the atari shirt!
when watching the previous video I was thinking the exact same thing when looking at the halo on the ground from the onboard footage. By the way that's not a glory, the specific name for that effect is heiligenschein.
Ahh ... good to know about the name of the phenomenon. Thanks!
Air Command Rockets No worries! Great series. And I may be mistaken, as heiligenschen is mainly used referring to dew causing the effect. Opposition Surge or the opposition effect is used when it's caused by a very rough surface, in this case a field. Fun fact, lunar regolith is retroreflective for this very reason! The rocks are so porous from being unweathered, and you can see this brightening around astronauts' heads in some photos taken from the moon. It's also why a full moon is far more than twice as bright as a 50% illuminated moon.
If possible, I'd like to see a pummus stone or other way to make the foam MORE foamy. Though, maybe too much foam might start causing issues in other ways, like incomplete evacuation. In fact, the foam might vastly change the optimum water level. Time for some 2l science!
Great videos - love it. I'm not a rocket engineer but... I work in the oil and gas world and we add surfactants (shampoo ?) to our water for pumping to reduce the friction losses (the term is slickwater - it lowers the water viscosity & hence reduces friction loss in the pipe/nozzle). Could this be another factor ie reduced nozzle friction losses and therefore more energy available for thrust ?
Another awesome video George. Quick one as it might be useful for my paraglider line tension prototype, where can I find the fuse app? I have a lot of data from different channels to interpret and visualise from .csvs and don't seem to find a simple program for it. Thanks for everything!
Thanks Andre, the Fuse app is something I wrote several years ago, because I too needed a tool to "fuse" data together from several different sources. It's a little outdated now, but still useful. I'm currently re-writing it to make it cross platform, as the old one supported only Windows. Please send an email to www.aircommandrockets.com/contact.htm
@@AirCommandRockets Thanks so much, didn't realize it was homebrew :) sent
My immediate thought about the initial air pressure drop was the air mass movement during acceleration. Could you put a hole or two at the very point of the nose cone to reduce that effect?
That's a good question, I am not sure how that would affect the air pressure if the hole is exposed directly to the on-coming air stream. It may behave differently depending on if the other vent holes are open or closed as well.
Have you considered using a GPS logger, which would not have the pressure error that a barometric altimeter does? Skydivers use a GPS that goes by the name of FlySight -- it's lightweight and logs at 10 Hz, I believe. As well, it uses Doppler data to measure velocities, which would improve your precision there over using differences in position data.
GPS could certainly be an option, though I am not sure what kind of altitude resolution could be achieved. I though it was around the 10m mark but could be wrong. GPS can also lose lock under high acceleration, but again I am not sure if that applies in this scenario or not. Having a GPS though on board would be useful for other things.
I am thinking that the effects you are seeking are directly correlatable to the viscosity of the liquid used as your propellant. As such, consider adding pure glycerine to water. It may also breakdown in UV better (ensuring that the farmer who owns this land is a happy camper).
That's a good point about the Glycerine, that's one of the reasons we only use low concentrations of the shampoo.
@@AirCommandRockets it is my impression that you are trying to enhance the effect of a two-phase flow. This may be along the lines of what you are looking to achieve - www.sciencedirect.com/science/article/abs/pii/S0301932218307717
@@AirCommandRockets I guess what I am suggesting is that you consider a higher concentration.
Could you install an accelerometer to improve the speed estimates? Heck, there must be some really fancy ways of measuring rocket speed. I wonder if anyone has ever tried to use doppler shift? You could have a little RF transmitter on the rocket transmitting a sine wave, and then measure the doppler shift in the signal from a receiver on the launch pad. (or the other way around, as I guess you could use a stronger transmitter if it was on the ground, with a little receiver on the rocket that could record some data to process later.)
yay I love the Atari shirt XD
At 2:38 he says: "This data was collected with the Zlog model 6 altimeter, from Hexpert systems."
Buy Link for the altimeter (Z6):
www.hexpertsystems.com/zlog/z6-order.html
Could you be hitting choked flow in the nozzle? I'd be surprised if you're breaking mach 1 in the water phase, but might be exceeding Mach 1 in the air phase. I'd be pretty suprised if compressible multiphase is well-studied since multiphase flow research is incredibly challenging, and isn't well-explored outside of applications applicable in industry. I definitely agree that you're seeing underexpansion at the nozzle exit. You've probably got a lot more potential performance in the rocket than you've seen so far.
If I remember correctly during the water only phase at this pressure the water is coming out at about 30m/s. This is a straight through nozzle without a divergent section, so during the air pulse I would be expecting only Mach 1 flow. With an expanding nozzle I would then expect > Mach 1 flow in the air phase. The big question is what is the exit velocity of the foam, and more importantly the velocity of the bubble surface (the water) as the bubble expands when it emerges from the nozzle. It would be interesting to find out if the foam can be accelerated to supersonic speeds out of a divergent nozzle. The complication of course is that the flow is not constant due to the dropping internal pressure.
@@AirCommandRockets I'm seeing a lot of air coming out in the jet in those stills at launch, which might be the gas dissolved in the water (which would be encouraged a ton by adding shampoo). Maybe there's something going on with sound propagation between the air bubbles and the water phase? That could depress the speed of sound a ton if it's got to cross from one to the other a ton. Thinking about the speed of sound changing that much just from the flow conditions is making me more than a little nauseous lol. I've never seen that sort of underexpansion in strictly subsonic flows, but that might be the limits of my experience talking.
So why do you think the foam creates such a noticeable improvement? Does it somehow increase the efficiency of the transfer of energy from the air to the water?
That's a good question, and I don't have a definitive answer. I have looked but have not been able to find any information on this yet. I suspect it is mostly caused by a higher exhaust velocity of foam compared to water. Water at this pressure comes out I think at around 110km/h and regular air comes out at sonic speed, and foam would be somewhere in between there.
I believe it’s due to the shampoo lowering the viscosity of the working fluid, which reduces losses, allowing a higher exhaust velocity.
Wouldn't the detergent increase viscosity? I would think the effect more likely due to the surfactant reducing surface tension of the water and thus promoting flow through the nozzle, and also extension of the ejection mass ejection duration due to the water being contained partially as foam - somewhat more even spread of ejection mass density than water on its own followed separately by the air plume.
I think the exhaust velocity is the key. To calculate the flow speed of water at the end of the nozzle we can use Bernoulli's equation, because the water is incompressible. I suppose that foam can be treated as high density compressible gas.
@@AirCommandRockets I think that such expansion of foam stream after the nozzle indicates that the supersonic flow occurs. Foam which is getting through the nozzle throat continues to expand. I'm very excited with thoutht about experiment with de Laval nozzle :D I'm curious how much more performance would it provide.
Ever thought about using two altimeters at different heights inside the nozzle to validate the accelerated air theory?
Yup, we do want to do this experiment at some stage. We'll probably build dedicated hardware using pressure sensors and record at higher sample rates.
Could you please share the links to the app(Fuse) you are using to compare the data?
Could a water rocket launched from a vacuum tube potentially go higher? I'm thinking a long tube that would be evacuated, with a short rocket to maximize acceleration in the drag free environment(resembling pingpong vacuum launchers). It seems right in line with carbon neutral launching methods.
I would expect you could make a tube like that and have it work. You could Have an extra pressurized reservoir behind the rocket that would help push it up the tube even faster.
What about springs to give the rockte an extra push...?
13:15, I am not seeing much concaving of the jet stream, but I would guess that widening the nozzle would help make it faster.
Was just about to post the same, a diverging hypersonic nozzle would use this lost thrust in the overexpanded exhaust. However I'm not sure how foam and water fits into this idea... Ps. If too heavy for the booster, just a diverging nozzle on the upper stage would be most effective due to lower pressure (1000m staging height has about 10% lower pressure)
@@minibeyse :D thanks for a reminder to this video, I haven't looked at rocket science for a couple of months :)
Nice job i researching for my lev one certification launch do you know where you can by h motor grains?
I am in you rocket club not America
I would have a look here: ausrocketry.com.au/motors-igniters/motors . Do you have a casing, or is that something you are going to borrow? That will determine what you will need to get.
600 Km/h whaaaaaat
And, what happend if you cover the noose cone with perforated vinyl? I think in a golf ball
So then... Is there a thrust bell in the future of this project? ~( 'w')/
Probably not for this project, we would have to change the release head on the staging mechanism, but it will be something to look into after this project. We would run some static tests first on the test stand.
How about experimenting with different hull surface treatments? ...or is this something already fully under control? (I am more a hydrodynamics guy:))
Sure there is always scope for surface treatment both internal and external surfaces for better airflow on the outside and better water flow on the inside. Any recommendations?
There must be some aerodynamics experts out there? Is surface roughness useful at those speeds?
Would a graphite surface in the water tanks produce useful roughness? No idea, but.... :)
A smooth surface performs better in this instance.
I guess that us much due to the high pressure. (should check Reynolds, ...)
Is there a program for determining the ideal bell nozzle shape and size?
www.dept.aoe.vt.edu/~devenpor/aoe3114/CD%20Nozzle%20Sim/index.html
www.aerorocket.com/Nozzle/Nozzle.html
@@AirCommandRockets Thanks
Sir, which software you are using to check the graph?
The program is called "Fuse". I wrote it several years ago, but I am re-developing it at the moment so that it's cross platform. Here is an old video of some of the functions: th-cam.com/video/xht-j-EQMLg/w-d-xo.html
Rocket science
I wonder how typical shampoo vs something like snow foam shampoo would compare....
How do they differ? I am not familiar with snow foam shampoo.
@@AirCommandRockets Snow foam makes a really dense foam when aspirated correctly, so curious if that change would change performance. Here is me using one particular brand, but there are many on the market. You can see how it sticks to the car. th-cam.com/video/pUkhoAAmB60/w-d-xo.html
What High Power pyro motor
is your water rocket at 1000 psi equivalent to?
At a pressure of 1000psi, total impulse is about 240Ns . That puts it in the H motor class. They have a really fast burn, so it makes it about H1200. I haven't done the numbers yet for the first stage but it will be probably in the J class.
Pouce bleu pour le tee-shirt
Where can we get the updated simulator?
There is still a little more work I need to do to it, but when that's done, I'll put it up on the website.
@@AirCommandRockets Great, thanks! because I noticed you updated the website to! Finally, just a quick note, you are getting to speeds where you start to have to account for the compressibility of air, that might be another reason for the difference in the simulated vs real values. When you release the sim, could you also release the math on which it is based?
Dean Wheeler did a good writeup of the maths behind water rocket flight. His simulator is based on these equations. www.et.byu.edu/~wheeler/benchtop/pix/thrust_eqns.pdf
Did you try with Diet Coke and Menthos?
Hi can someone tell name of program used at 2:57
The program is called Fuse. I wrote this program a couple of years ago to allow us to do analysis of waveforms from multiple sources. Unfortunately this program is not commercially available (yet).
@@AirCommandRockets Thanks a lot you are awesome. Your videos always gives me motivation i and some my friends we are creating water rocket will be pleasure for me to share with you our rocket
I used a altimeter who detect th apogee and was connected to my prachut deployment system!!! So.... why are you using a timer for the parachut deployment suystem?? I don't want to teach you anything lol Just want to understand!!!
We only have one altimeter that has output for apogee detection that we can use to trigger deployment. All of our other altimeters only record data. We fly this altimeter only when we need to, to reduce the risk of losing it in a tree or a crash. As a result we almost always use timers since they are cheap and quite reliable. When this rocket is flown as a two stage we will definitely use it to deploy the parachute because it will be a lot harder to predict where apogee will be.
ola good night, I'm from Brazil and would like to manufacture here a rocket with this technology of yours. could the Lord help me with the first raisins in my construction already a strong embrace.
Thailind