Proud to have a rocket article in Hackspace magazine!

Rather wonderfully a couple of months this back the mighty Hackspace magazine visited Midland Rocketry Clubs "Midland Sky" event and flew a couple of their own model rockets and met and chatted with everyone there. They explained they wanted to run some rocketry features in an upcoming issue... And indeed the have in issue 12. It's not all rockets but there's a good chunk of rocket articles in there covering model rocket 101, interviews with the mighty thrust vectoring Joe Barnard/BPS space and also an article by yours truly! Based on a document I wrote up off the back of my rocket design workshops my article takes people through designing and simulating a rocket using the Openrocket software. Really pleased to be included and hope it helps bring a few new people to look at rocketry. You can download a free pdf of Hackspace magazine via the website but can also order a print copy which also can be found in all good magazine stockists! 

Scratch built 29mm rocket anchor point (Or why do things the easy way!)

So I am working on a design for a minimum diameter 29mm rocket air-frame which means that the motor directly fits into the complete internal diameter of the rocket with no space around it. Common practice with larger rockets is to use an internal motor mount tube mounted in some centring rings, the fore centring ring usually is where the builder will place an eyelet or lifting bolt that will be the anchor for the recovery system/parachutes etc.

Obviously without this centring ring you need to come up with a different solution. I want to have the option of using the motor ejection charge so needed something that gases can expand through but also it needs to be strong. I recently picked up 2nd hand an aluminium anchor point for a larger 38mm air-frame off another rocket builder via Facebook and a discussion followed about how with a smooth metal outer finish it was difficult to get them to adhere/epoxy to the inside of an air-frame. So my idea was to make a similar anchor point to receive a lifting eye but to make it slightly under size and then knurl it to be a better fit and to maximise the keying surface for when it is epoxied into the air frame tube. The knurling is pretty badly done and definitely not decorative but it is definitely going to allow a small amount of epoxy to create the strong bond needed.

So why the "Why do things the easy way" bit... Well... after a search of the material/scrap pile I didn't have a piece of aluminium of large enough diameter to make this component. So I have done it the hard way! I started of making a very crude casting from some melted aluminium! With my very dinky little kiln!

I then poured the melt into a crude mould made from some of my diy casting sand (silica play sand and bentonite clay sourced from cat litter (unused... I a NOT that much of a cheapskate!)







The crude casting was then chucked up in the lathe (the cheap 2nd hand mini lathe I bought a while back) and turned to round.


I then realised none of the suitable boring tools I had actually fit in the toolpost of the mini lathe so I parted off the job and transferred it to my old faithful perfecto lathe and bored out the inside. Its somehow more pleasing when you really have made something from scratch!

One Mix Yoga review

For many years I have been a fan of ultraportables... I owned (and still have) an original eee pc701 when they came out and I have owned a litany of PDA devices over the years and regular readers (a select group of amazing individuals) may recall I recently got Linux up and running on my linx1010b tablet.

I'd lusted a lot after a gpd pocket when they were released last year but the lack of an SD slot put me off. I loved the form factor however and so when I saw the very similar One Mix Yoga which has an SD slot I decided to take the plunge. The final push was that it had a backlit keyboard... Great for a bit of late night browsing or indeed checking a rocket simulation in a tent at a rocketry meet!

It's a great machine, preconfigured with Windows 10 it boots quickly and everything works. Mine had a stuck pixel on arrival but I am happy to report that it unstuck with some usage and has resolved. I'm not really a windows fan but do reluctantly use it occasionally so the plan was to try and get it dual booting windows and some flavour of Linux.

I'd seen that a few things weren't working for people under Linux on the one mix yoga, most noticeably sound, so I was prepared for some issues. I was also prepared after my linx 1010 Linux experiences to have some screen orientation issues to resolve. I tried 3 or 4 Ubuntu flavoured distros before settling on the most recent version of Ubuntu Mate. Having tried lubuntu, xubuntu and vanilla Ubuntu I was struggling to get screen resolution correct (it's a pretty hi Res screen) and was therefore delighted to click the Hidpi option in Ubuntu mate which instantly resolved all my tiny icon/font/cursor issues. I found that I could make my screen orientation settings persist under Ubuntu mate and I quickly resolved and got screen brightness controls working. WiFi works and hibernation is good... But I still haven't found time to resolve getting sound working or indeed swapping the axis on the touchscreen... An issue I faced and resolved on the linx 1010b.

So it's now setup to dual boot and this works well.. giving me an ultraportable linux box for doing bits of work on the go but I can also boot into windblows if I require a bit of surfing/media/youtube.

It is amazingly portable... Fits into a cargo pants pocket easily and is pretty lightweight. Despite having a slightly slower processor than the gpd pocket I find it's fine for some libreoffice on the go or for a bit of Openrocket rocket design work. The reversible hinged screen makes it an excellent ereader and flipping the screen disables the keyboard which means you don't disturb your reading with random keypresses.

Open Source Cubesat Workshop 2018

As Red would say "YES"!

I had the pleasure of travelling to this years OSCW that was once again hosted at an European Space Agency campus ESAC the European Space Astronomy Centre just outside Madrid, Spain. I equally had the pleasure of staying with the Libre Space Foundation crew including some of the core team but also some of the global contributors.

There is so much I could say about the talks and the event but I don't know how to summarise it all! So instead I will just say that the quality of presentation was great and it really is re affirming and heartening to see so many communities forming around the opensource development of space technologies. Staying with and meeting some of the wider Librespace contributors makes one feel part of something amazing and left me invigorated and wanting to contribute more. Here follows a small photo dump!

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!