Cambridge postgraduate student [Adam Greig] helped design a rocket avionics system consisting of a series of disc-shaped PCBs arranged in a stack. There’s a lot that went into the system and you can get a good look at it all through the flickr album.
Built with the help of Cambridge University Spaceflight, the Martlet is a 3-staging sounding rocket that lifts to 15km/50K feet on Cesaroni Pro98 engines. [Adam]’s control system uses several Arm Cortex M4s on various boards rather than having just one brain controlling everything.
Each disc is a module that plays a specific role in the system. There are a couple of power supply boards sporting twin LTC2975 able to supply custom power to a dozen different circuits. The power system has a master control board also sporting an M4. There’s an IMU board with the guidance system — accelerometer, magnetometer, gyroscope, and barometer, all monitored by an algorithm that computes the rocket’s position and attitude in-flight. There’s a radio board with a GPS receiver and an ISM band radio transceiver for telemetry, as well as a datalogger with 10 thermocouple measurement channels. Engines are controlled by the pyro board which controls firing currents on four different channels. The vertical spacers also serve to transmit power and data to neighboring boards.
If you’re interested in learning more, check out the project’s code and schematics on [Adam]’s GitHub repository.
[Adam] is no stranger to these pages, with his Nerf Vulcan turret published a few years back, as well as his balloon tracking rig published more recently. Photos are CC-SA and can be found in [Adam]’s Flickr feed.
There are trends in YouTube videos among various video producers. A few weeks ago, it was all about fidget spinners until some niche tech blog ran that meme into the ground. Before that, the theme was red-hot knives cutting through stuff. The setup was simple; just heat a knife up with a blowtorch, cut through a tomato or golf ball, hit stop on the high-speed camera, and collect that sweet, sweet YouTube money.
[David] from RCExplorer.se isn’t like most YouTube stars. He actually knows what he’s doing. When the latest trend of rocket-propelled knives hit the tubes, he knew he could blow this out of the water. He succeeded with a fantastic rocket-propelled machete able to slice through watermelons and fling itself into the woods behind [David]’s house.
Unlike most of the other YouTube stars trying their hand at rocket-powered slicers, [David] is doing this one right. He’s using hobby rocket motors, yes, but they’re reloadable. [David] crafted an engine casing complete with a proper nozzle machined out of stainless for this build. The rocket sled itself is an aluminum bracket bolted to a piece of carbon fiber plate that travels down a rail with the help of four skateboard wheels. A machete is then bolted to the plate, which is propelled down the track a bit faster than 200 km/h.
When it comes to rocket-propelled knives, the word ‘professional’ really doesn’t come into play. This, however, is an amazing piece of craftsmanship that you can check out in the videos below.
Continue reading “Swedish Rocket Knives”
Although the thrill of launching rockets is usually found in their safe decent back to Earth, eventually you’re going to want some data from your flight. Everything from barometric pressure, GPS logging, and acceleration data is a useful thing to have, especially if you’re trying to perfect your craft. [zortness] over on reddit created a data logging board created especially for amateur rocketry, a fabulous piece of work that stands up to the rigors of going very fast and very high.
The design of the board is a shield for the Arduino Mega and Due, and comes with enough sensors for over-analyzing any rocket flight. The GPS logs location and altitude at 66Hz, two accelerometers measure up to 55 G. Barometric, temperature, and compass sensors tell the ground station all the data they would need to know over a ZigBee 900MHz radio link.
Because this is an Arduino, setting up flight events such as deploying the main and drogue chutes are as easy as uploading a bit of code. [zortness] built this for a 4″ diameter rocket, but he says it might fit in a 3″ rocket. We just can’t wait to see some videos of it in action.
LVL1 has a new rocketeering group. This rocket engine testing platform is the first project to come out of the fledgling club. The purpose of the tool is to gather empirical data from model rocket engines. Having reliable numbers on thrust over time will allow the team to get their designs right before the physical build even starts.
The rig uses a pine base, with a PVC frame, threaded bolts, and a PVC cuff for mounting the engine in place. It is set to fire up in the air, directing the thrust down onto a scale. The flex sensor in the scale is monitored by an Arduino, and should be able to hold up to the 5000
pounds grams of thrust max which this type of engines can put out. The data is pushed via USB to a laptop computer where it is stored in a spreadsheet.
Calibration would be an issue here. But as long as they’re always using the same strain sensor the numbers will be accurate enough relative to each other.
Last month, the Cambridge University Spaceflight society launched two stages of their Martlet 1 three-stage rocket. After seeing our call for rocket builds, they sent in a launch report. We’re glad they did; it’s an amazing piece of work that screams into the atmosphere faster than the speed of sound.
The society is designed the three-stage Martlet 1 with the goal of reaching 15km (50,000 feet) over a launch range at Ben Armine in Scotland. This launch was a test of stage separation, intended to work out any bugs in the system before going to the full-sized rocket.
When Martlet 1 takes off, it’s 1st stage engine fires for 5 seconds and coasts for another 9 seconds. In the video after the break, the guys expected to hear the pop of the second stage igniting after 14 seconds. The team forgot to account for the fact the rocket would be 3km in the air at that time, and thanks to the slowness of sound the second stage was heard though the clouds at 25 seconds after launch.
With rockets, hardly anything goes exactly as planned, so unfortunately the team only recovered the bottom half of their rocket. After searching over 60 square km for the second stage, the guys realized it might be lost to the moors of Scotland. Hopefully the second stage will turn up soon so the full 3 stage stack can be realized.
Check out the launch videos after the break.
Continue reading “Two-stage rocket climbs to 15 km, promptly gets lost”
If you’re building model rockets you want to make sure they fly straight, and most of that is dependent on the stabilizer fins. It has long been a problem come assembly time. How can you make sure that they’re being aligned without any variation? [Rrix] mentioned that one technique is to use a square to position them perfectly perpendicular to the bench on which the rocket is being assembled. But this is still prone to error. His method uses a couple of precision jigs made out of cardboard.
He designed this pair of jigs in Inkscape, then used the files to fabricate them out on a laser cutter. It worked like a charm, but led him to another issue that can be solved in a similar way. Model rockets have rail guides that travel along a rod attached to the launch pad as the craft accelerates to a point where the fins have enough effect to keep it going in a straight line. If those guides aren’t straight, your fin alignment will be all for naught. His second version of the jigs includes a cut out for these guides.
When someone writes in and says, “Hey, I strapped a camera to a rocket and took videos of it launching!” it’s really hard for us to not get suckered in. Try as we might, we just couldn’t resist taking a look at the videos [Vlad] recorded of his model rocketry “exploration”.
Inspired by our 4th of July post featuring POV videos of bottle rocket launches, he bought himself an 808 keychain camera and decided to try his hand at some high flying video. He strapped the camera to his 46” Estes rocket with a few pieces of scotch tape in an effort to keep weight down, and set off to his launch pad.
He used a Estes C6-5 engine for each launch, which he estimates took the rocket up to a height of 300 feet rather than the typical 500 feet, due to the added weight. While not particularly useful, the video is still awfully fun to watch, and perhaps it will inspire others to mount cameras on even larger, more powerful rockets.
We can only hope.
Continue reading to check out the videos [Vlad] shot, but be warned, the descent is vertigo-inducing.
Continue reading “Model rocketry from the rocket’s point of view”