ODR Flight!... and lots of learning!

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Photo credit Peter Barrett

I had the absolute pleasure of attending the Midland Sky event held by the midland rocketry club last weekend where I finally got to fly the Open Development Rocket or ODR. In simulation I had it flying to 2900 feet and in real life it was a little heavier I felt it was going to fly a little lower as I thought the simulated design was at its optimal weight.. however I was incorrect and indeed it went higher! It shot off the pad on its 38mm Cesaroni H152 2 grain motor and went into a near perfect vertical flight up to an apogee of 3255'.

Photo credit Peter Barrett

It nosed over and deployed the drogue chute at apogee correctly and began to descend, it was supposed to fall back to 500' and then the quantum altimeter was supposed to blow the other charge to release the main chute. What actually happened was that at around 2000' it deployed the main early, I can tell it happened here from the change in steepness of the decent rate on the graph output from the altimeter. I don't think that this was when it fired the main ejection charge but rather the nosecone was shaken off and it dragged the main out. It does highlight an area of ODR that needs a redesign - the upper section of ODR that contains the main chute is really too small. In an effort to get some space back I had reduced the shoulder of the nosecone and despite it being reasonably tight it came loose. Interestingly I had left the motor ejection charge in place and on its longest delay setting and based off the openrocket simulation I believe that this would have fired around the same time that the early main deployment occurred. Perhaps it produced a bit of an extra kick/movement to help dislodge the nosecone?

 The altimeter data states that the charge channels were fired at the right altitudes so I believe everything worked... but that I needed to design a bigger upper section and then have a better longer nosecone shoulder and retention. All good learning.

So the result... well.. A LOOOOOONG walk! ODR drifted a long way with its 152 second long flight and I did fear that it was lost! That said we had a good line on where it lay and a fantastic recovery operation was performed. All round nice chap Stuart Livings jumped in my scruffy car and we drove as far as we could towards ODR. Parking in a farmyard we then set out on foot to get ourselves on the line/bearing we thought ODR lay on, Stuart then used his drone with FPV to fly out on the line and he quickly discovered ODR apparently having made a good landing some distance ahead. He kept the drone locked above ODR and that gave me an easy heading to walk to and recover her! Many thanks Stuart. So I definitely take some learning from this but overall I am pretty pleased, I definitely feel that this was a positive failure mode, meaning that if you are going to fail its better to fail where the results are a slower descent rather than a faster descent that's close by!

ODR Rocket deployment groundtests

Got a bit of time this afternoon to do some ground tests of the deployment system of the ODR opensource rocket. Its my first dual deploy rocket so I'm learning lots as I go. One thing I definitely discovered is its quite tight in the upper section where I plan to fly the main chute...I was using some quite thick webbing as the recovery bridle which I might replace with some thinner kevlar to try and reduce the volume of stuff I need to cram in there... failing that I could always reverse the roles of the sections and fly the main chute in the lower section of the airframe. For more details of the ODR opensource rocket check out this post.

Making Drogue and Main parachutes... aka SEWING IS HARD!

I'm trying to get the ODR rocket build finished and am finalising the electronics bay for dual deployment where it will blow a charge and release a tiny drogue parachute at apogee and then deploy another charge to push out the main chute at a predetermined altitude on the way down.

I wanted to use a crossform parachute after all the work I put in working through the maths of them (paper and calculator spreadsheet here) and as ever I wanted to make them myself...although 5 hours in on the sewing machine I began to question why!

For my Panta Rhei flight I used a reasonably heavy ripstop nylon and I cut it with a soldering iron which gave an excellent edge that required no hemming, however this wasn't suitable for the job for the ODR rocket. I needed to consider packed sizes of the chutes as ODR is a slim rocket with not masses of room in either section for the recovery system. As such I wanted to use some very lightweight ripstop nylon I have as it would pack much smaller, however I also needed it to be strong as with dual deployment the main chute is deployed when the broken air-frame is falling at some speed. I designed the drogue to bring the falling air-frame down at about 20 meters per second as I had seen similar fall rates on online that others had used. The main is designed to further drop the descent rate to around 5 meters per second which is quite a large change in velocity so it needs to be pretty strong.

I decided that I would cut the nylon traditionally and then stitch a double hem to add strength to all the edges. I first used baking paper to cut an over size pattern and then cut the rectangle sections and pinned the hems. This was essentially the same process for the tiny drogue and for the main. I made 2 rectangles and then pinned and stitched them together to form the cross. The sewing machine I borrowed of my daughter is an excellent albeit small machine and it didn't have the clout to stitch through the 2mm nylon cord I was using for shroud lines so they are hand stitched onto the drogue. For the main chute I wanted to reinforce the area that the shroud lines attached to on the chute and attached some small squares of ripstop into each corner, this took ages to do as I hemmed the squares first and then attached them but it should hopefully increase the chances of the chute surviving deployment!

If I had access to a more capable machine and also had more room in the air-frame and could overbuild the chutes slightly I would definitely consider making the lines continue all the way through the chute to make a very strong version.

I've not quite finished yet and have to fit the shroud lines to the main but I've finished the shroud lines on the drogue chute and am pleased with the way I have worked out to terminate the attachment end. I first measure out the desired length (1.6 times the length of the rectangle side from the calculations which equalled 56cm) and then stitched the lines together. I then individually stitched a matching length loop into the end of each of the 8 shrouds and then I stitched the 8 shrouds together and finally with the aid of a bit of stitching and a few drops of superglue I wrapped all the shroud ends in some thick polyester thread. Very pleased and I will use the same technique with the shrouds on the main.

Finally .. whilst I had my daughters small sewing machine set up I stitched some small Nomex fireproof blankets to protect the parachutes from the deployment charges. I definitely rushed these through and they are rough but functional!..

So there we go, learnt loads and got to grips with the small sewing machine... I could definitely do with continuing a bit of sewing to increase my skill at it!

Screwdrivers, Allen keys and nut spinners.....My current kit

So even for me this is a geeky post! I wanted to share this current collection of tools which I am very pleased with and its covering most of my maker needs for screwdrivers, nuts and bolt driving and more. I have stacked of other larger drivers and kit but this seems at the moment to really hit the spot and cover a lot of bases in my day to day making of electronics and rockets and also maintaining my 3d printers and CNC's. So above from right to left is my Wera Tool Check Plus, my Xiaomi/Wiha 24 in 1 driver kit, my Sealey STM103 torque screwdriver and then a 1/4" to 4mm adaptor and finally a set of 4mm sockets rangeing from 2.5mm to 5.5mm. The Wera Tool Check Plus is a pricey but glorious bit of kit, the mini zyklop wrench included is a joy to use with its tiny degree ratchet and small size making it great for reaching and working inside tight assemblies. There are loads of reviews about the Wera Tool Check online so check em out!

The Xiaomi/Wiha 24 in 1 kit is a little gem... Wiha are a great German tool brand and apparently they loved what xiaomi were doing and partnered with them to make this set. Its definitely aimed at small electronics and phone assembly/dissasembly (makes sense in terms of the Xiaomi connection) but contains a range of mini torx, as well as allen, posidrive and other 4mm tools. Its available on lots of chinese retailers like banggood and fasttech etc and it is definitely worth the (not masses) of money. The driver handle has a spinning head to allow one handed use and is smooth and comfortable and oozes quality. The magnetic tray and the metal box all work flawlessly and make you (well me) want to keep it all in order! (rare for me!)

So the Sealey stm103 is a torque screwdriver that works by sensing the amount of torque you place on it.. it reads out the torque on the display, it has numerous modes and can read peak torque or, as I find more useful, you can define a desired torque and when the sensor detects you have reached it it will both bleep, buzz and also an LED lights. Its amazing that this can be bought for less than £35 and comes with a certificate of inspection and calibration etc. Very handy indeed. Finally the 1/4" to 4mm adaptor has been a great find and expands the repertoire of both the Tool Check and the Xiaomi/Wiha kit. Over the years I've had a few variable cheap multi driver 4mm kits and therefore have accumulated a few spares in that format.. including the small set of quite cheap and cheerful sockets... however at that scale and for low torque they continue to serve well.

So there we go... geeky post, but all this lives together most of the time as a little kit and I find it invaluable!

USB soldering iron hack

Been a big fan of these cheap and cheerful USB soldering irons since discovering them via @biglesp ... There's a couple of things with them, the first one is the well known fact that it's best to run them off a USB battery pack as otherwise they present a bit of current at the tip. This leads to the second thing that bugged me and I fixed! So the iron is designed to only heat the tip when the user has it in their hand..  it achieves this with a touch switch and also a motion detection system. The trouble is is that my USB power bank auto switches the power on and off when it detects a draw at the socket. This meant that I could plug the iron in and use it but if I put the iron on the stand and it timed out it would turn off but also wouldn't wake the USB supply when I retouched/moved the iron meaning I would have to pull the USB cable out and reinsert. So... I have modified it to be permanently on. The instructions are pretty straightforward..  remove the yellow wire to the touch switch that you can see in the top picture and then also remove the silver tube component (a small tube with a soft spring inside which acts as the movement detection switch). Finally you then need to bridge the 2 pads to close where the silver tube switch would have been (see picture below). Now your USB iron is always on!

Open Boat Tail rocket... Maiden flight!

OBT_maiden_7July18 from concretedog on Vimeo.


Ardent readers of this blog (all 6 of you!!) will recall a while back I designed and built a small rocket with a boat tail and I finally got chance to fly it at a family and friends BBQ last night. It flew really well on a classic Estes B6-4 motor. It was a really still evening but (even though I flew a pretty tiny parachute) it still managed to end up drifting the wrong way and landing in a thicket in a bog! After much rummaging however the rocket was recovered successfully!

I'd designed it with around 5 grams of mass in the payload section and as it was a maiden flight I didn't fancy sticking a pricey altimeter in it so a willing volunteer was found in one of my European Space Agency lego minifigs!

If you fancy building or improving on my design, it's all opensource and available here. 

Thanks to Rob for shooting this video on his phone!

ODR, Open Development Rocket. Now Opensource!

So here it is! Some of you who follow me on twitter may have seen me talking about this rocket build but this is the official release of the project. A while back I released the OBT small rocket design and this is the next opensource rocket ODR. ODR is either pronounced "owther" and is the mystical Norse force or could be O.D.R standing for Open Development Rocket! 

ODR started as a project for my needs, having passed my L1 high power certification I wanted to build an airframe that could fly well on L1 power but could also serve as a learning and testing platform. Therefore ODR has been designed with a large electronics/avionics bay and can be configured for single or for dual deploy recovery systems. Its simulated in OpenRocket and can fly on G-I 38mm reloads and as soon as I actually fly it I will update the project. 

There are numerous sections I need to finish and some parts that need much better documentation but I have done some docs and have supplied all the files on Gitlab. The main tubes are phenolic tubes purchased in the UK from the excellent (I have no link with them other than am a customer) Blackcat Rocketry. All the other components are designed in opensource free software and the files are included. It has used CNC routing and a 3d printer but equally could be done with a printer and a laser cutter. So find your local makerspace/fablab etc. 

Here is the ODR repository

So get in touch via Gitlab and or twitter @concreted0g if you have questions and I'll try my best to help. And yeah... that's a librespace foundation sticker... lets claim space.. the libre way.