Acceleron V - build thread

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Postby Wingnut » Fri Jun 05, 2009 8:47 am


"Adjacent" will certainly be the more efficient configuration. If they're "stacked", the lower canopy will create an area of turbulence above it which will render the upper chute less effective. A single chute is the most efficient configuration, in terms of weight versus deceleration, but multiple chutes sure does look good.

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Postby october sky » Fri Jun 05, 2009 11:56 am

I do agree with you Mike but they could still be staggered and far enough a part not to "block" the other, would you agree ? :wink:
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Postby air.command » Tue Jun 09, 2009 2:10 pm

Acceleron V build update:

The booster is now painted and assembled, with removable fins and all electronics fitted. We still need to attach the parachutes and sustainer guides (tonight).

The top ring brace is made from laminated balsa with a wrap of fiberglass.

We've now done full pressure tests on the individual spliced pairs of bottles up to the operating pressure of 130psi and held them there for 2 minutes. Out of 18 pairs of bottles only 10 didn't have any leaks. 9 are used by the rocket so we have one spare for the day. We can easily replace a pair of bottles should a leak develop.

We've done pressure tests of the assembled booster segments up to 110psi (to check for leaks in the couplings without putting too much stress on the bottles)

We've tested the baseplate to full operating pressure to make sure it won't buckle on the launch pad from the force of the three boosters.

Since we cannot really run any electrical wires through the airframe we have to run them on the outside. We have to make sure there is plenty of slack in the wires as the entire rocket will stretch about 2cm in length when pressurised. If this slack is not built in to the design you could easily pull wires out of their plugs.

The whole stretching issue (in all dimensions) really drives a lot of the design in terms of how things are attached to each other and what clearances you must provide. The same goes for the launcher. Everything has to be a little bit loose yet rigid enough to prevent things from getting wedged under pressure.

Below is a progress photo of the booster:
Image
The dual flight computers are in the center of the image with wires leading up to the pressure switch, and down to the staging servos. They also go out around the ring to the two parachute deployment mechanisms (other side). I decided to put the flight computers on this booster segment with their respective batteries in order to axially balance the rocket more. Originally they were next to the parachutes. One flight computer is triggered by pressure (the primary one) and the other is triggered by a g-switch.

Here the sustainer is undergoing a full pressure test:

Image

We've run preliminary simulations on the rocket now that we have an overall weight. According to the sim we should get staging at around 30m AGL with a release velocity of ~35m/s. The sustainer sim predicts apogee at 276m after release. Which puts it in the 300m region all up. However that is only under ideal conditions. I generally consider that only 70-80% of that will actually be achieved (if things go well). Hopefully we will end up somewhere in the 230-250m range (~800 feet). We're flying an altimeter on the booster as well so we can capture some data about speed and release timing. We match up ground/inflight video timing to the altimeter data so that we can see when things happened in relation to altitude.

There will be 3.4L of water in each booster segment for a total of 10.2L in the booster and 1.7L in the sustainer.

What is hard to predict is the sustainer flight performance since we will be using foam, instead of just water.

Now that we have the rough figures I can set the appropriate timings for staging and recovery in the booster and sustainer's flight computers.

I've also been doing some tests on our Flycamone cameras since one cut out after about 1 minute on the last launch. I have read a lot of reports that the batteries are marginal in the cameras and when it is a little cold and the battery is a little older you can experience power issues. I tested the recording on one of them, and it gave 4.5 minutes, 1.5minutes, 43 seconds and 2 seconds worth of recording on 4 subsequent recordings. It sure looks like a power issue to me even though the camera was mostly charged. I think I read somewhere that the power button needs to be in the OFF position while charging it, but I may have had it in the ON position during the charge and perhaps it did not charge properly. The other camera recorded for ~14 minutes before cutting out. They both had plenty of room on the memory cards.

I won't have time to do it by this weekend but I think I'll be building external power supplies for the cameras for next time.
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Postby strud » Wed Jun 10, 2009 8:25 am

So all good for this weekend then ?

Will definitely come along to watch this one.

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Postby Kryten » Wed Jun 10, 2009 8:56 am

strud wrote:Will definitely come along to watch this one.

Me too - it should be awesome
Fantastic work as usual, George

strud wrote:So all good for this weekend then ?


Keep an eye on the NSWRA thread - launching at Doonside is likely to be put on hold for a few weeks :cry:
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Postby air.command » Wed Jun 10, 2009 9:12 am

Kryten wrote:
strud wrote:Will definitely come along to watch this one.

Me too - it should be awesome
Fantastic work as usual, George

strud wrote:So all good for this weekend then ?


Keep an eye on the NSWRA thread - launching at Doonside is likely to be put on hold for a few weeks :cry:


We are targetting to be ready for launch this weekend. One word of advice though, you may want to park your car a little further away. :?

My biggest worry for the day is not that it may explode, develop a leak, veer of course, get caught in a tree, release the sustainer towards the ground ... but that it will land on something or someone that it shouldn't. I was thinking of setting it up a bit further away since we really don't know how it will go.
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Postby ROCKet STAR » Wed Jun 10, 2009 10:01 am

air.command wrote:My biggest worry for the day is not that it may explode, develop a leak, veer of course, get caught in a tree, release the sustainer towards the ground ... but that it will land on something or someone that it shouldn't. I was thinking of setting it up a bit further away since we really don't know how it will go.


There is nothing more exciting than an unpredictable rocket. ;)
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Postby air.command » Tue Jul 07, 2009 8:32 am

We had a good time this weekend at Doonside launching the rocket for the first time. :D
I've posted the full update of the flight here:

http://www.AirCommandRockets.com/day78.htm

The update includes photos and a video of the flight. Although the flight was not ideal, we did learn a great deal about the performance of the rocket and we tested a lot of things on it for the first time.

Image


We think we know what happened and now have a plan in place to make a few minor modifications. We are hoping that the next flight will be more vertical. :wink: I am sure glad we had the backup staging and recovery system as it looks like that's what saved the rocket.

Unfortunately these things don't come with instruction manuals (who reads them anyway right?) but that's what makes building things like this fun. We should have the rocket ready to fly again by the next NSWRA launch day. ..... better bring your helmet just in case though ..... :D
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Postby Kryten » Tue Jul 07, 2009 10:32 am

Bummer about the camera. :cry:
It was certainly an "interesting" flight.
With all the research that George puts into these projects, it was surprising that it wasn't more successful.
It did seem to need more thrust
I think a launch rod/tower/rail would help to keep it vertical until enough tail weight was lost.
I expect a better flight on 25th July
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Postby october sky » Tue Jul 07, 2009 2:12 pm

I just have to say that I love the work you do George. That footage was brilliant again ! 8)

Maybe we should start calling you "Aussie Vern" ! :)
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Postby ~RR~ » Tue Jul 07, 2009 3:38 pm

nice video... 8) and the Flycamone2 recorded to the end, mine didn't look as bad as your does but it still works, and if you can rebuild it go with a bigger external battery...
I like the camera handle to, maybe something like a rifle stock attached may help stay on target :idea: ..... off to the shed now :lol: ....
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Postby air.command » Wed Jul 08, 2009 4:14 pm

~RR~ wrote:nice video... 8) and the Flycamone2 recorded to the end, mine didn't look as bad as your does but it still works, and if you can rebuild it go with a bigger external battery...


Hi RR,

Actually the smashed camera in the sustainer only recorded about 40 seconds and turned itself off prior to launch. :roll: It did not have the external power source. The camera on the booster (the one that survived) had recorded the full flight because it used the external power source.

I've tried to repair it but it looks dead. I've plugged the camera module back in its connector which looked okay. It won't power up even with the external battery. There was a tiny tiny smd resistor broken away from one of its contacts so I resoldered that. There was a tiny inductor that has it's top broken off but the coil and contacts are still good. The camera can however be powered up through the USB port and shows the normal "PC" on the display. I can access the SD card on the camera. Nothing else I can see is broken even after inspecting the PCB from both sides. There is no telling what could be damaged if something shorted on impact. The LiPo battery looks dead and its quite dented from the impact.

I might just have to put it in my shoe box "museum" of smashed parts. :D
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Postby ~RR~ » Wed Jul 08, 2009 5:49 pm

air.command wrote:There was a tiny inductor that has it's top broken off but the coil and contacts are still good.

sounds like the same broken part in mine (but mine still works, just doesn't charge)
here's mine (testing) Imagedodgie-as :twisted: with 2 x AA and 1 x AAA as I couldn't find a 3 x AAA battery holders... then I found the Uniden phone batteries...
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Postby Sumo310 » Wed Jul 08, 2009 6:40 pm

That is really really cool!
I can't wait to see future flights
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Re: Acceleron V - build thread

Postby air.command » Tue Jan 26, 2010 10:21 pm

An overdue update....

Now that we have the last set of flights out of the way, we are focusing all our attention on getting this rocket back in the air again. After the rocket exploded on the pad last year, one of our main concerns had been the bottles withstanding the required pressure. The way we had been splicing them wasn't too bad, but the splices were obviously close to their limits. Despite several pressure tests to full operational pressure, one failed anyway on launch day. One bad one is all that's needed to ruin your day.

The other problem we had was that they were often leaky (result of the porous glue we use) and so we had a low yield rate when making the spliced bottles (spliced-pairs). All the ones on the rocket were non-leaky, but we had to throw quite a few away while making the rocket.

So we set out to try a new splicing and re-enforcing technique to comfortably handle the required 130psi and significantly increase the yield of the spliced bottles.

A little more info and test results on them are here: http://home.people.net.au/~aircommand/day81.htm#splice and http://home.people.net.au/~aircommand/day82.htm

So far the results from this new technique look promising and we have even test flown them to see how they perform under real world conditions. This is what they look like when complete:
Image

Over the last few months we have been collecting bottles from friends and family and have now begun a bit of a production line getting them spliced together and re-enforced.

Here are some 70 bottles, both 1.25L and 2L cleaned and ready to be spliced.
Image

Tonight we finished the first phase of the splicing technique. Trimmed, heat shrunk, ends curled, masking tape applied, cleaned and sanded glue joints, and glued with Sikaflex 11FC. All in all we've put together 12 x 2L spliced pairs and 10 x 1.25L spliced pairs. The big ones go on the booster and the smaller ones go into the sustainer with a few spare. We will be making up 2 identical sustainers for launch day in case something goes wrong with one, we can easily swap over to the other.

Image

We went through about half of the Sikaflex cartridge today.

Next up is gluing the outer sleeve, wrapping with glass strapping tape and using the rest of the bottles to do the re-enforcing.

Some stats about the 2L spliced-pairs:
The spliced-pair made with the new technique fails at 190psi.

The bottle has a cross-sectional area of 9503 mm squared (14.73 square inches) which means that at 190 psi the splice was holding the equivalent of 1,269 kg (2798 pounds) stopping the two bottles from flying apart from each other. That's the equivalent of hanging a small family car from the end of the splice!

Pressure switch

The other issue we noticed on the original flight was that the pressure switch did not work quite well, so we designed and tested a new one which we want to use on the booster to detect burnout and initiate the staging. (Clicking the image below will bring up more details about the pressure switch)

Image


PS. Thanks krusty for showing us how to do little clickable images on the forum. :D
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