Multi-stage Details, Acceleron III assembled

We have updated our main site with some development photos showing the Acceleron III booster with the sustainer on top. The details may be found here:

http://www.AirCommandRockets.com/day36.htm


There is still lots more work and testing to be done, but finally we have an idea of the overall dimensions.
____________________________________________________________________

Our First Splicing tests

We had our first go at splicing yesterday. We used the symetrical splicing method first to see how well it will work. We used PL Premium glue kindly donated by Team Parental Advisory.

The symmetrical splicing method is described here:
http://www.geocities.com/wrgarage/const.htm



We need to leave it for a few days to dry and then we will pressure test it. The collar was made by heat shrinking a section of a larger bottle over another cold water filled bottle. It was a little warped, but should be okay. Doing it this way gives you a really tight fit over the bottles to be spliced.

We will probably make up sections like this and then join them neck to neck so that the number of splices is minimised. The 22mm throat is big enough that any choking effects are negligible within the rocket. The sections being screwed together also means you can replace a section should it burst or get damaged.
__________________________________________________________________

development progress

This last week has been a bit quiet on the development side of things due to other commitments, parties and the like. With those things out of the way, development will again continue this week.

I also received the 10 new micro-servos I've been waiting for for a couple of weeks. I built a small test circuit from a 555 timer to check them out and they seem pretty good and look like they will do the job. I have yet to measure the current consumption so that we can choose our batteries in case we need more power. Having the servos on hand now means we can complete the deployment systems for a number of rockets. We will also need to update the flight computer software to generate the appropriate pulse train to drive them.

This week we also plan on having a go at doing some splicing of bottles, so we can do some more burst tests.

__________________________________________________________________

Flight Computer V1.3

We have finished the V1.3 Flight computer code and also took some photos. The full details of the design is available here:

http://www.AirCommandRockets.com/flight_computer_V1_3.htm



While retaining the same functionality of V1.2, the new flight computer is lighter ( 37 g with battery), uses a single battery design and has a greater selectable range of delays ( 3 - 11 seconds in .25 second intervals.)

__________________________________________________________________

Staging Mechanism Update

This weekend we spent a few hours in the workshop building the necessary components for the staging mechanism and upgrading the booster.

Some photos of the progress of the staging mechanism are available here:

http://www.AirCommandRockets.com/day35.htm


___________________________________________________________________

Starting Multistage Work

Having flown the Acceleron I & II booster a total of 16 times now, we are happy with how it has been performing.

So last night we spent a couple of hours designing the staging mechanism for the booster. And I think we finally have a good plan. The release will be based on a Gardena release mechanism rather than a crushing sleve. The main reason is that with the gardena mechanism, you can release the rocket exactly when needed, rather than when the pressure drops inside the main booster as with a crushing sleve. Also all our existing nozzles will fit the sustainer. The other main reason is that we know that the Gardena mechanism can hold higher pressures up to at least 220+ psi. We want to be able to retain the design once we start reinforcing the bottles. Lastly the crushing sleeve method doesn't lend itself very well to the construction of CD nozzles, which we plan to revisit especially with the sustainer.

Full details of the design will be published once we build it and we know that it works.

Acceleron II has now been disassembled and will get a couple of upgrades:
1. Each booster segment will be extended by a further 2L capacity to help with the greater payload. This means that the total capacity of the booster will be close to 25L.
2. The dummy payload will be replaced by a new payload pod that will house the flight computer, camera, parachute and staging mechanism actuator. The staging mechanism will be mounted just above the pod. The pod will also be used to support the sustainer and protect the payload contents from the spray during separation.

The first sustainer will most likely be based on two 1.25L bottles joined together and will look similar to "OO", with the exception that it will also have a flight computer, camera and side deployment. Eventually when we buy an altimeter we will put that in there as well.

We are more likely to spend this weekend in the workshop rather than launching rockets as we are keen to see how it will go.
___________________________________________________________________

Vertical racing

We had a go at simultaneous launches again this weekend. It was fun as usual, and we even tried foam in all three rockets at the same time.


Of the 12 launches all the rockets survived the day well so we were happy. The update contains photos and a highlights video as usual.

http://www.aircommandrockets.com/day34.htm

We are going to rebuild a couple of the rockets now so there should be something new to see in the next update.

___________________________________________________________________

Progress continues

Because it was too windy to fly this weekend we decided to do more work in the workshop. We manufactured three more aluminium Robinson couplings for extending Acceleron II's capacity by another 6 liters.

We want to fly Acceleron II again before the upgrade, so it will be couple of weeks before it is done. We first need to drink lots of lemonade before that happens!

Otherwise progress is going well on the V1.3 flight computers, with two of them now being finished and tested. We are now creating two 90mm diameter payload/nosecone sections with the deployment system inside them. These are more aerodynamic then our previous ones.

One nosecone will go onto J4 II and the other one will be used for Acceleron II's yet to be named sustainer.
___________________________________________________________________

Foam and CD Nozzle Thrust Data

We have finished processing the thrust data from a couple of weeks ago that compares Convergent-Divergent (CD) nozzles to straight trough nozzles. We did 12 tests in all comparing 7mm and 9mm CD nozzles to 7mm and 9mm straight through nozzles.

The update is here:

http://www.aircommandrockets.com/day32.htm

The tests were done in exactly the same fashion as the last set of static tests when comparing foam and water thrust.

The results were interesting, although not unexpected. The update also includes the data in a spreadsheet format if others want to use it for further analysis.
_________________________________________________________________

Simultaneous Launches and foam flights

In order to get back into flying we decided to have a go at launching multiple rockets simultaneously. Other than being lots of fun, one of the biggest problems was knowing which rocket you should be watching and the other things like nosecones falling off.


We then also flew a number of flights using the Jet foaming technique and 7 mm nozzles. The slow take-offs are quite a contrast to fully open nozzles using only water.

The update is here: http://www.aircommandrockets.com/day33.htm
The update also includes pictures and a video of the day's highlights.

_________________________________________________________________

CD Nozzle Tests

We tested two CD nozzles this weekend. There were 12 tests in all:

• 3 tests with 7 mm straight through nozzle
• 3 tests with 7 mm CD nozzle
• 3 tests with 9 mm straight through
• 3 tests with 9 mm CD nozzle

Since it takes a bit of work to translate the video frames (around 6000 in total) into a spreadsheet it will take some time to do that. Once we have the data in a usable format we will publish it again.


We went through almost a liter of bubble bath solution, but collected the water during the tests so it just didn't go onto the lawn.

We think this will be it with the static tests for a while, as we are keen to get back to real flying.
_________________________________________________________________

Convergent Divergent Nozzles

In order to see if a water rocket can benefit from CD nozzles (de Laval nozzle) while using foam we have built a couple to hopefully test this weekend.


One is a 9mm nozzle (aluminium above) and the other a 7mm (black plastic). The divergent part is conical in shape and has a slope of 4 degrees from the centerline. This value was obtained by reviewing the video and seeing at what angle the spray emerges. The actual angle of the spray varies over time from quite wide to quite narrow near the end as the pressure drops.

The average angle was about 4.7 degrees during the middle of the burn. We chose a value of 4 degrees because our thinking was that if it was more than 4.7, there would be nothing touching the sides during the middle of the burn and hence ineffective. That is just a guess and not based on any scientific or mathematical calculations.

We just want to test to see if there is a noticeable effect when a CD nozzle is used with foam compared to a straight through nozzle. If there is a difference, further tests will be performed to see how the shape can be optimised.

________________________________________________________________

Thrust Data for Water-only and Foam rockets

Well it has taken a while but we finally managed to get some good thrust data for a water-only water rocket and compare it to a water rocket using foam generated by our Jet Foaming technique.

http://www.aircommandrockets.com/day31.htm

The update includes the thrust data curves for 6 firings in total (3 water and 3 foam), as well as an analysis of the results. There is a video that shows how we measure the thrust.


The write up is a bit lengthy but we wanted to make sure that as much data was available for others if they wanted to process the data further or use it in their designs.

Feedback is always welcome.
________________________________________________________________

Thrust Measurements for Water and Foam

We finally managed to get some good thrust data for water and for foam today. We ran three identical tests for water and three for foam so that we could see how reproducible the results are and how much the two differ. The only thing that differed was the addition of bubble bath to the mix, and use of our Jet Foaming technique to generate the foam. All rocket, pressure, water volume, and other parameters were as close to identical as possible in all the tests.

We were quite happy with the data and were quite surprised by the results. The data will be published on our website as soon as we are done processing the raw data, and had a chance to properly analyse it.

__________________________________________________________________

Thrust Measurement Rig - First Trials

We finished building the water rocket thrust measuring rig today, and did four firings to test it out. The first two tests did not use any dampening on the lever arm and as a result it was virtually impossible to see the scale needle as it flew around so much.

No Dampner in this photo

We then put a disk in a bucket of water on a long lightweight dowel mounted near the scale to act as dampner. This was suggested by Clifford Heath a while back and a similar technique was used by Antigravity Reaseach when they did their thrust measurement. The needle motion was much more steady. Thanks also to Jim Fackert for suggesting the camera pointed at the scale to take readings. We should also thank Gordon M, Richard W, David L, Trevor, Brian and others for useful suggestions on how to set up the thrust measurement rig.

Dampner Added to lever arm

We have plotted the initial thrust curves of an 8L rocket with a 7mm nozzle using only water and then again using foam and the difference in curve shape was quite substantial. We will not publish these initial results just yet, as we would like to confirm the data by repeating the experiment a number of times and then averaging the results. Full data will be published once we obtain it. Hopefully in the next few days.

_______________________________________________________________

Acceleron II Flights

We test flew the Acceleron II booster (18.75 L capacity) three times this weekend with very good results. The encouraging results in the booster's almost always vertical launches means that we are ready to progress to the next stage of development - staging mechanism and the sustainer.

Full details can be found here:

http://www.aircommandrockets.com/day30.htm

We also took some measurements of the speed of the booster just after the start of the air pulse and had a close look at the sound the rocket generates in order to extract accurate timing of events during launch.

The twin parachutes also worked well to bring the booster to a safe landing each time.

________________________________________________________________

Tips for producing water rocket videos

We have updated our site with some useful tips in helping to produce videos relating to water rockets. The update can be found here:

http://home.people.net.au/~aircommand/videotips.htm


_________________________________________________________________

Acceleron II Details

We have updated our main site with detail photos and diagrams of the Acceleron II cluster booster.

http://home.people.net.au/~aircommand/day29.htm

The booster is now finished awaiting launch when the weather improves.

________________________________________________________________

Acceleron II Development

We continue to further develop our Acceleron II booster. We have now added another 6 L of capacity, which makes it almost 19L in total. The nozzles are now 10 mm which is almost 30% more nozzle area.

The top bottle is still the same dummy payload that carries about 600mL of water for ballast that represents the weight of the second stage. That means as it stands the booster lofts about a 750gm sustainer (including water).

The dry weight is now ~1.3 Kg (including the empty dummy payload) which is a bit on the heavy side, but simulations predict an altitude beyond 100m. The booster will, however, only need to travel around 12m before it releases the sustainer at roughly 50m/s = 180 km/h = 112 mph. The simulation is based on 120psi which is what we currently use on this booster. 15-20 more psi is easily achieved, and gain us a few more m/s.

Simulations also show that this Booster / Sustainer combination should be able to achieve altitudes beyond 200 meters (650 feet) with the 120psi - 130psi range.

In this photo the booster still does not have the parachutes fitted. We hope to have it finished this weekend and take it on a test flight weather allowing. Full details of the rocket will be posted on the website once we had a chance to fly it.
____________________________________________________________

Continuing Development

This week we have continued development and design work for the thrust measurement rig, and have manufactured a number of parts for it. We have also bought an analog kitchen scale that will be used to measure the thrust.

More research has been done into nozzle design, and we now have a plan for what designs we will test.

More work has also been done on Acceleron II including bottle reinforcement. More details will be posted in the next web update. There were no launches this week due to other commitments.
____________________________________________________________