JSB Rocketry

Click here to edit subtitle

Era Overview

The Start of the 'Present and Future' stage can be marked by our first Spliced pair of bottles and the introduction of the Guide Rail. We have also made a new launcher that we made from scratch only taking the Air valve from the old launcher. The new launcher is more versatile as it allows us to peg it down and attach a guide rail. I will go through each of the new features of our water rockets.

FEEL FREE TO SKIP TO THE LAUNCH VIDEOS AT THE BOTTOM OF THE PAGE!

The Parachute Release System:

This is the main part of the rocket that helps recover it after a launch. The spliced bottles are strong but not sound. Thus if the rocket crashes then the bottles can be damaged and this causes them to leak. We found this is a few launches. So we needed a way of recovering the rocket. The parachute release system seemed a good way of recovering the rocket. Thanks to Air Command who provided a short sharp tutorial on the release system-we got to work. . Each time the parachute fails to deploy or open gives us new opportunities to improve on the design. Since the original we have improved the design in ways such as making the shorter and wider  to suit the shape of the parachute, using a hot tent peg to put holes in the corners to stop the bottle ripping on heavy impact, using lighter and smaller servos, and using elastic to help pull the parachute out of the capsule. Recently development would include using electronic timers to control when the servo is activated.

Recently because I have been at school etching my new circuit board I was also lucky enough to cut out some release systems for the rocket on the laser cutter out of corroflute. The circles are difficult to cut out by hand and the laser cutter makes short work of it. This simplifies the process and makes it quicker meaning a working release system can be produced in minutes. Several have been made already so if one is destroyed then others can be quickly fabricated so that a working rocket can be up and running immediately rather than having to go back home and rebuild the rocket.

Fins

In the second stages of the water rocket design we used simple corroflute fins made out of a piece of old corroflute I found in the loft. These fins were simple triangles attached to the side of the rocket with sellotape  These were not very good as they were not very secure. So now we have used a old lemonade bottle neck to glue some larger fins to it which allows us to move them between different rockets. Using 3/4 fins is best as more than 4 will not guarantee a more stable rocket, only more weight.

Recently  we made a new fin can that is unique to any before...this a far more effective solution to the problem. The fins are firstly glued in place at regular intervals and then further reinforced with fibreglass. Two folds are made where the fin can meets and a Nut and Bolt can be put through to secure it to the rocket, acting as a large clamp. This has worked well and it means that it can be easily moved between rockets and provides a firm attachment point. 

Nose Cone

During July I have also started to develop a new nose for the rocket to help gain a few extra feet as the bottles I use are quite stubby and hence cause more. Also be because I am using a larger nozzle for this rocket, drag is directly proportional to the square of velocity, because the rocket is traveling faster, the blunt nose cone will significantly reduce the altitude. I found a well suited bottle and after trawling the web for some time found that plastic Easter eggs work well as the nose cone tip. After buying the bottle, I sanded down the writing and markings and applied a few coats of prima, making sure to fill any lumps or holes. Then spray painted the cone blue and there it is. The nose cone simply shares the same screws as the release mechanism. This allows easy mounting and changing on other rockets.

Spliced Bottles

The key to splicing water rocket bottles is the glue that you use. It needs to be strong. Very strong, and it needs to bond well to PET plastic as lemonade bottles are made of this plastic. We found from Air Command that polyurethane glues bond best with PET. In axminster a shop sold Titebond glue that was exactly what we needed. We try a splice and it went up to 100 psi which was going to be our operating pressure. It didn't explode. We used Tesco's 2 litre bottles because we found that the thread on them was not big enough to fit the tornado coupling. Plus the bottles are only 17p! Because they were only water bottles, they deformed alone. However in a spliced pair, that only deformed a little bit. To solve this we bought some glass strapping tape. We tried this on another pair and pressure tested them to 120 psi. After we analysed them and the spliced showed no signs of leakage and the bottle hadn't deformed, showing that the tape helped hugely!! 

Presently we use two glues, one for the overlap which provides the seal for the air pressure, and the sleeve over the top provides the strength for the spliced as stronger glues tend to leak. We have pressure tested these to 140 PSI with the new compressor and they were fine, not exploding with no stress marks. We will do a burst test to determine safe launch pressures, at the moment we are ok for 130 PSI.

Because we have noticed stress marks on the necks of the bottles, I decided to start making splices out of a new type of bottle. Previously I have been making the splices out of 2 liter water bottles, and although they are cheap, they burst at around 80 psi which is slightly worrying considering that I pressurize them to 110! We feel that it wouldn’t be a good idea to pressurize to the target pressure of 130 psi because they may explode. Because of all this I have decided to make a test splice out of lemonade bottles giving a final volume of 3.4 l using the asymmetric splicing technique. The bottle was pressurized to 130 psi and didn't explode and there were no stress marks. Therefore all further splices that aren't fibreglasses will be made of these bottles- it is also convenient that we have a large collection of this specific bottle!

Tornado Couplings

To connect the Spliced Bottles together, you will need some Tornado Couplings. These can either be made or bought. We decided after much consideration to buy them as it would be quicker, easier and safer, to help fit the 15mm Launch Rod through them we machined them out using a stepped drill piece. They now have a internal diametre of around 18mm. We first had difficulty selling them due to the fact that they require a very tight lock. We solved this via the use of Washing Machine washers which were fine for a while but leaked and still needed tightening quit significantly. We solved this problem with a pair of Rubber O-Rings which act as washers, and give a really good seal and yet can be undone with two fingers. 


Below is a link to where we got the couplings:


http://www.ebay.co.uk/itm/like/250929799055?showlimghlp=true&lpid=92&device=c&adtype=pla&crdt=0&ff3=1&ff11=ICEP3.0.0&ff12=67&ff13=80&ff14=92&ff19=

Update:

We have now purchased these new couplings (to the left) after reports of stress marks on the see through couplings. The new ones have a better sealing surface for the O-Rings and have been pressure tested to 130 PSI all holding with no stress indicated. We will fly them on our new rocket at 200 PSI.

Fiberglass Reinforcement

To reach higher pressures safely, a technique used by Water Rocketeers to reinforce bottles is to wrap them in fiberglass and use Epoxy Resin to hold the fibreglass in place. 


My Dad's friend kindly gave me some 200 gsm plain weave fiberglass and for Christmas I asked for some West System 105 Epoxy Resin and 206 Hardener as other Water Rocketeers had had some great success with this combination. We used one of our standard spliced bottles as the pressure chamber but without the Titebond sleeve on the outside as the Fibreglass acts as the Strong part of the glue. The white flexible Polythene glue acts as a airtight seal. The fibreglass is cut to size and the ends of the cloth are cut to for flaps that wrap around the end of the bottle. The first splice we cut the flaps to small and ended up with some folds, so now we do 14 flaps each 60mm long at each end. We intend to take the bottles to around 180-200 psi so we decided to give the bottles 2 wraps in fibreglass with a 50mm overlap. Basing our results on Air Commands data these bottles with have a burst pressure of 300 psi+ which is a good safety margin for us as our compressor can only go to 200 psi!


To do the fibreglassing you need a Rotisserie. We made one from a Wind-Screen wiper motor and some Sofa Caster Wheels. Some 20mm PVC pipe and MDF finishes the Rotisserie that keeps the bottle moving while the Epoxy is drying and prevents it all from running to one side. Bulbs can also be used as the Slow Harder cures at around 25 degrees Celsius which is just above room temperature. The Bottle is spun for 45 minutes before turning off the Rotisserie and leaving for two days.


Once the bottle has fully cured a Dremel is used to remove any rough edges that aren't neat and the bottle is given a wash in warm water. After that the bottle is taken slowly to 150 psi in the Garden where it creaks around a bit!! After that we take the bottle to 200 psi at the launch site so that if the bottle explodes it will not disturb the neighbors. 

The New Launcher

Our old launcher was the first one we ever got. It was deigned for very small rockets and not for multi-bottle rockets. Plus, because it was bought from a manufacture it was difficult to customise. When we started to build a larger rocket using the spliced bottles we decided that we needed a launch tower or a guide rail to help support it going up as this is the part of the journey of the rocket were the least amount of the air is flowing over the rockets fins and making it unstable. We had done some research and found that a guide rail would be the most suitable as it would enable us to change the diameter of the rocket via using different sized bottles, and the concept is easier as it requires less supports as there is only one support unlike a tower which has at least 3. Plus our old launcher had a faulty release mechanism and was starting to bend/rust. So we set about making a new launcher our of plumbing parts from B&Q. We used the Air hose adaptor from the old launcher but other than that this launcher is new from scratch. It uses a pull string instead of a hydraulic system like the old, as it allows us to stand further away from the rocket during pressurisation, and it simpler as it uses a meccano lever and cable tie to release the Gardena attachment. 

The guide rail consists of a curtain rail on a piece of wood. With old tent poles as the supports. These (along with the base) are pegged into the ground using tent pegs. To stop the Poles coming apart we used some pins to slot in. The launcher can be transported when you fold the poles up and then they are held in place with some velcro and a ribbon. 

NEW- LAUNCHER UPGRADE!
Recently we have now made an attachment that conveniently allows us to launch rockets using a 15 mm nozzle rather than the standard 9 mm. This allows larger volume rockets. The new attachment simply clips into the standard 9 mm  and allows a larger release head- which means we don't have to make a new launcher and the air connection stays the same simplifying the design. (See Picture to the right).

Compressor and Airhose

To compressor larger rockets, we invested in a larger compressor that can fill rockets far quicker, and to higher pressures than the car  tire compressor from Halfords! This compressor, has quick connect attachments to attach to the launcher and a non-return valve built in for rockets without a launch tube. The airhose also allows us to stand further back from the pressurized rocket and we can turn of the compressor without having to go near the rocket unlike the older compressor. Below is a table with some of the fill rate we have calculated using the 130 psi flow rate as the compressor fill rate is exponential, meaning that as more pressure there is in the rocket the longer it will take to keep pressuring. To simplify the calculations we stuck with the 130 psi flow rate:


We used this formula: P1 x V1 = P2 x V2


P1 = Pressure of atmosphere (1 bar)

V1 = Volume of air need to compress

P2 = Final Pressure in Rocket

V2 = Volume of Rocket


The flow rate's of the compressor at the two target pressures below were found via the compressors specs on the website.


2.5 US gallons = 9.4635

2.5 US gallons would take 5:02 at the 200 psi flow rate

2.5 US gallons would take 2:29 at the 130 psi flow rate


5:02 / 9.4635 = 0.53045913 litres per min at 200 psi

2:70 / 9.4635 = 0.2324721 litres per min at 130 psi


The results are below (the results do not include the amount of water taking up part of the volume):

Click to edit table header
 
 
Rocket:
 Time to 130 psi (minutes):
 Time to 200 psi (minutes):
Blue Diamond 1 (5.3 litres)
  1:12
  2:48
Blue Diamond 1a (3.3 litres)
  0:46
  1:45
Blue Diamond 2 (8.6 litres)
  1:54
  4:37
Blue Diamond 2a (6.6 litres)
  1:18
  3:18
Blue Diamond 3 (11.9 litres)
  2:42
 6:19
Blue Diamond 3a (9.9 litres)
  2:00
 4:55
Blue Diamond 4 (15.2 litres)
  3:03
  7:00
Blue Diamond 4a (13.2 litres)
N/A
  N/A

Nozzles

When constructing a launcher it is important that you think about how you attach your rocket to the launcher without it flying off. We have 3 different Nozzle sizes, 7mm, 9mm and 15mm. These use standard Garden Hose Release Heads. The smaller nozzles can only be used on smaller rockets as they do not produce a large amount of thrust for a heavier take off, yet they give a more sustained burn through to apogee, meaning a longer burn, but not as peak powerful as a larger nozzle. A larger nozzle will give a short large amount of thrust for a shorter time meaning the a larger peak of thrust for not a long time, the heavier the rocket the larger the nozzle needs to be.

Payload Bays

When I introduced the spliced bottles into my rockets, I started adding other gadgets to the rocket- such as cameras and reserve parachutes. To do this instead of just putting the compartments that held these in at the top of the rocket, I decided to make use of the space between the spliced bottles as seen in the diagram below. I got the ideas of Air Command as seen on there impressive Polaron G2 with the reserve parachute payload bay. At the present time of me writing this I have been using the Camera bay to a large extent and it seems to be performing nicely as it acts as a fairing for the tornado coupling and allows me to capture the footage of the rocket from an on-board perspective- yet doesn't protrude the outside of the rocket meaning less drag and less likely that any of the parachute cords can get stuck on it. They include a bottle that has a frame made of corroflute plastic inside to hold the desired gadget. The frame is then held in place with screws, and is slotted onto the rocket and the other half of the rocket can then be attached allowing us to fill the rocket on the pad.

Cameras and Altimeter

When we first get into water rockets, we didn't include a Camera or Altimeter because we had no release system. We tried on some occasions putting the Fly DV camera on some of the rockets but we lost 2 or 3 cameras on impact. The footage was pretty cool and new at the time but little else was done. As soon as we developed a reliable release system, it was time to re install the camera in a module faring between bottles to give the camera more protection and a more permanent space in the rocket. We first used the Fly DV camera (to the left) for all our video. This camera is around £30 and is easy to mount in the fairing, and easy to download the footage from. The only downside is the quality of the video (640x480) and the fact that it has a permanent time stamp which cannot be removed with ease. Other than that we now tend  to use it on casual flights when high resolution isn't needed.


Once we had started splicing our rockets were going much higher than before. We were desperate to get an altimeter! Many on the web looked promising, but after some thought, we bought the Hobbyking Altimeter. At first we bought it from the wrong warehouse and it didn't arrive for weeks. But shortly after we switched our order it arrived in about a week. This is a cheap and easy to use Altimeter that does what it says it does. All we needed was an easy to mount, reliable way of recording altitude. it has no launch detect, but simple records changes in air pressure 18 seconds after it is switched on until it is unplugged. You then plug it into the computer and download the data in the form of a distance time graph and search for the peak altitude. The Altimeter is cheap costing around £7.50 from the website and easy to mount with velcro. We tend to use a 50mAh 3.7V Lipo to power it which is cheap and already uses the same charger as the other LiPo's.


The most recent piece of tech we have invested in is the 808 #16 Keychain Cam (as seen on the right). It records fabulously video though a wide angle lens at 720p, and it is no bigger than a large stamp!! The quality really is great. The Battery life and the easy of use is equally impressive. My only downside this camera is that it is difficult to mount in a water rocket. The Wide angle lens along with the awkward shape mean that it has to be mounted outside the rocket, though over the Summer I will try and make a custom fairing to make the camera easier to change between rockets. The files are stored on a Class 10 micro SD card with an amazing 32GB of storage. This camera was a little in the expensive side at £50 but very worth it for the incredible footage you can get. 


For evidence of these piece of tech in use, footage and data is available to view in the YouTube videos.

Jet Foaming Spacer

The Jet Foaming Space helps create a sustained burn in the water rocket. Only using a small inlet, PVC pipe and bubble bath added to the solution. When the rocket is pressurised around 2/3 of the water is forced up into the second splice creating an air gap. When the rocket is launched the water from the top punches a hole in the water in the bottom allowing the water and bubble bath mixture to mix thoroughly to create foam during flight and a sustained burn. Many other rocketeers have had great success with Jet Foaming, not only looking cool, but significantly increasing the altitude of the rocket as well. The previous designs of spacers mean you need a specific design of Tornado Coupling- a quick modification to the design now allows the Spacer to work accordingly with any coupling.


I also put together the Jet Foaming Spacer I have been meaning to make for a while. With all the parts lying around it took less than an hour. Its construction is relatively simply. The inlet cut out on the laser cutter as seen in photo, was Epoxied in place overnight and the end of the PVC pipe was melted slightly to make it expand and rest in the top of the splice. 

Parachutes

When we first thought of having a parachute on our really early rockets, we thought of using bin liners and other types of this plastic. However we found that overall these were not very effective, as they were not symmetrical and they were not very easy to fold. Our first proper rocket with an electrical parachute release system used a kites parachute which had holes in it and was very thick. This wasn't very effective as it was too big to fold and still brought the rocket down to quickly. So we did some research on parachutes so sure enough we made a large umbrella into a parachute, this worked 50% of the time. However it did tangle and was still fairly large when packed. I then did some experimental work with a smaller parachute made of a smaller umbrella. I found that this parachute became far more successful, than the larger one. Because of this I came to the conclusion that smaller parachutes open easier than larger chutes, the reason I believe, is because less air is needed to flow into the chute to make it open. So because of this I made two more small parachutes out of bigger umbrellas via cutting and then hemming the edges. To date I have not had a single tangle, with either of these two chutes. Plus they pack very very small, however the balance of the chance of the chute opening and the impact speed need to be equal. The bigger the rocket, the faster it will fall meaning a larger parachute will have more air to open it. Plus to bring it into a soft landing because it can have a bigger chute, depending on its heavier mass.

Below is a list to our Parachutes we use on our rockets:

Identifiable Name: 


Size of Diameter:            


Shroud Line Length:   


In Service:   


Notes:                               

Lifeboat Umbrella Parachute


1500mm


2000mm


No


This was our first umbrella parachute that wasn't 100% successful. It was made out of an old umbrella, however was to large for our types of rocket, and this is the reason be believe, it tangled regularly . 

Identifiable Name: 


Size of Diameter:            


Shroud Line Length:   


In Service:   


Notes:                               

Lifeboat Parachute (Resized)


800mm


1200mm


Yes


Because the larger version of this parachute was tangling I resized it to make it more reliable and easier to pack in the Side Deployment System.

Identifiable Name: 


Size of Diameter:            


Shroud Line Length:  


In Service:    


Notes:                               

Black Umbrella Parachute


1000mm


1500mm


Yes


This was our first successful parachute that was 80% successful. It was made out of an old handbag umbrella. 

Identifiable Name: 


Size of Diameter:            


Shroud Line Length: 


In Service:     


Notes:

Multi coloured Umbrella


800mm


1200mm


Yes


This was our first fully successful parachute that was. It was made out of an old umbrella, that was trimmed and hemmed with the help of my grandma! To this day we have had no tangles! It was made at the same time as the Yellow Parachute.

Identifiable Name: 


Size of Diameter:            


Shroud Line Length: 


In Service:     


Notes:

Yellow Umbrella


800mm


1200mm


Yes


This was our first fully successful parachute that was. It was made out of an old umbrella, that was trimmed and hemmed with the help of my grandma! To this day we have had no tangles! It was made at the same time as the Multi coloured parachute..

Identifiable Name: 


Size of Diameter:            


Shroud Line Length: 


In Service:     


Notes:

Drogue parachute


500mm


1000 mm


Yes


This is a very small parachute made from a smaller black umbrella. This parachute is a secondary chute and is not designed to be deployed first. Should the first chute fail, this one should bring the rocket down a little slower, but a gently landing will not be certain. The chute just prevents more damage. It has to be smaller because any bigger wouldn't fit in the reserve parachute bay. 

Identifiable Name: 


Size of Diameter:            


Shroud Line Length: 


In Service:     


Notes:

Black and White Chute


1200 mm


2000 mm


Yes


This is a large parachute made from an old golf umbrella given to me by a friend at school. This parachute is a primary chute for larger heavier rockets. Via the calculations below we worked out that is parachute should take our regular rocket down at 3m/s.

Parachute Equation:


To work out the size of the parachute, I can use a very helpful equation as seen below:


D = sqrt( (8*m*g) / (pi*Ad*Cd*v2) )


This tells us that the diametre of the parachute is equal to the square root of 8 times the mass of the rocket (kg) times the acceleration due to gravity (9.81m/s/s). Then this answer divided by pi times the density of the air (Ad) (for simplicity sake around 1.22kg/m3). Then times the drag coefficient of the chute (around 1.4 for the traditional dome shape) then times the rockets velocity when it is descending, squared. It sounds rather complex but it is simple with a good calculator!!


This equation is good because you don't want a parachute to small as then the rocket will be damaged on impact, yet to big and the rocket will drift far away even if there is little wind. In basic terms you want the rocket to land at about 3 or 4 m/s. You use that as the velocity. You can then substitute your values into the equation and work out how big your parachute needs to be. 


Example for Blue Diamond 3:


From the Altimeter plot we know that my rocket travels at a decent speed of 4 m/s as we use the simple speed = distance/time (see plot below). We can then put this into the equation to find out how large the parachute is:


D = sqrt( (8*0.9*9.81) / (pi*1.22*1.4*42) )


D = 0.9 metres (900mm). This is correct as on this particular flight the rocket used a 800mm main parachute and a smaller drogue which would add up to around 900mm.


However 4m/s is not perfect, so you simply add in 3 m/s instead of the 4. This gives around 1.2 metres in diameter. So my next parachute will be this diameter all worked out with this equation. For more details please see this great website below:


http://my.execpc.com/~culp/rockets/descent.html

YouTube Videos:

Below are a list of videos of the rockets in-flight and on-board footage from a camera mounted in a payload bay. For more videos please visit my Youtube Channel!!


The videos nearer the top are the more upto date:

New Channel (JSB Rocketry):

<----------    Click here to view and Subscribe to the channel!! 

This video covers two flights undertaken in late October 2014. This Rocket was a made to test the Fiberglassed splices  we are intending to use to break passed 150 metres.

During the remaining weeks of the Summer, we made the most of the long sunny evening at our local playing field and fired off some Water Rockets. The Blue Diamond 1 was flown with foam and the Keychain camera.

Being Lucky enough to get a GoPro 3+ Black for my birthday I couldn't wait to start recording rockets in Slow Motion! This video shows some Blue Diamond 3 flights also testing the new reserve deployment system.

Here are some flights using the RRT1 and our new Blue Diamond 3. This rocket has a volume of 11.9 litres and is the same as the Blue Diamond 2 except from an additional splice section added. The #16 keychain cam was also used along with the HK Altimeter. 

Here are some flights using the new RRT1. Blue Diamond 2 was used along with a new camera and Altimeter.



Old Channel (Jamie Bignell):

Here is the maiden voyage of Blue Diamond 2 with the New Nozzle, New Spliced Bottles, New fins, new Parachute release system and launch rod! Probably to date our highest launches!

Here is the new 15mm Launcher being tested with the Standard Blue Diamond 1 Water Rocket. Notice the dramatic increase in height and speed compared to the 9mm!

This video shows some highlights from various launches of our Blue Diamond 1 rocket.

This video shows some highlights from various launches of our Blue Diamond 1 rocket.

This Abnormal video shows a slow motion launch of our Blue Diamond 1 rocket- I wouldn't normally post this but it is great so why not!

Copyright © 2016 JSB Rocketry