Posts with «rocket» label

Tiny Radio Tracks Your Balloons

The name of the game in rocketry or ballooning is weight. The amount of mass that can be removed from one of these high-altitude devices directly impacts how high and how far it can go. Even NASA, which estimates about $10,000 per pound for low-earth orbit, has huge incentives to make lightweight components. And, while the Santa Barbara Hackerspace won’t be getting quite that much altitude, their APRS-enabled balloon/rocket tracker certainly helps cut down on weight.

Tracksoar is a 2″ x .75″ x .5″ board which weighs in at 45 grams with a pair of AA batteries and boasts an ATmega 328P microcontroller with plenty of processing power for its array of on-board sensors. Not to mention everything else you would need like digital I/O, a GPS module, and, of course, the APRS radio which allows it to send data over amateur radio frequencies. The key to all of this is that the APRS module is integrated with the board itself, which saves weight over the conventional method of having a separate APRS module in addition to the microcontroller and sensors.

As far as we can see, this is one of the smallest APRS modules we’ve ever seen. It could certainly be useful for anyone trying to save weight in any high-altitude project. There are a few other APRS projects out there as well but remember: an amateur radio license will almost certainly be required to use any of these.


Filed under: radio hacks

You’re Never Too Young to Be a Rocket Scientist

We’ve been keeping tabs on the progress SpaceX has made toward landing a rocket so that it can be reused for future orbital launches. As you would imagine, this is incredibly difficult despite having some of the world’s greatest minds working on the task. To become one of those minds you have to start somewhere. It turns out, high school students can also build guided rockets, as [ArsenioDev] demonstrates in his project on hackaday.io.

[Arsenio]’s design targets amateur rockets with a fuselage diameter of four inches or so. The main control module is just a cylinder with four servos mounted along the perimeter and some fancy 3D printed fins bolted onto the servo. These are controlled by an Arduino and a 6DOF IMU that’s able to keep the rocket pointing straight up. Staaaay on target.

We saw this project back at the Hackaday DC meetup a month ago, and [Arsenio] was kind enough to give a short lightning talk to the hundred or so people who turned up. You can catch a video of that below, along with one of the videos of his build.


Filed under: Microcontrollers, transportation hacks

Hacklet 68 – Rocket Projects

There’s just something amazing about counting down and watching a rocket lift off the pad, soaring high into the sky. The excitement is multiplied when the rocket is one you built yourself. Amateur rocketry has been inspiring hackers and engineers for centuries. In the USA, modern amateur rocketry gained popularity after Sputnik-1, continuing on through the space race. Much of this history captured in the book Rocket Boys by Homer Hickam, which is well worth a read. This week’s Hacklet is dedicated to some of the best rocketry projects on Hackaday.io!

We start with [Sagar] and Guided Rocket. [Sagar] is building a rocket with a self stabilization system. Many projects use articulated fins for this, and [Sagar] plans to add fins in the future, but he’s starting with an articulated rocket motor. The motor sits inside a gimbal, which allows it to tilt about 10 degrees in any direction. An Arduino is the brain of the system. The Arduino gathers data from a MPU6050 IMU sensor, then determines how to steer the rocket motor. Steering is accomplished with a couple of micro servos connected to the gimbal.

 

Next up is [Howie], with Homemade rocket engine. [Howie] is cooking some seriously hot stuff on his stove. Rocket candy to be precise, similar to the fuel [Homer Hickam] wrote about in Rocket Boys. This solid fuel is so named because one of the main ingredients is sugar. The other main ingredient is stump remover, or potassium nitrate. Everything is mixed and heated together on a skillet for about 30 minutes, then pushed into rocket engine tubes. It goes without saying that you shouldn’t try this one at home unless you’re really sure of what you’re doing!

 

Everyone wants to know how high their rocket went. [Vcazan] created AltiRocket to record acceleration and altitude data. AltiRocket also transmits the data to the ground via a radio link. An Arduino Nano keeps things light. A BMP108 barometric sensor captures pressure data, which is easily converted into altitude. Launch forces are captured by a 3 Axis accelerometer. A tiny LiPo battery provides power. The entire system is only 23 grams! [Vcazan] has already flown AltiRocket, collecting data from several flights earlier this summer.

 

Finally we have [J. M. Hopkins] who is working on a huge project to do just about everything! High Power Experimental Rocket Platform includes designing and building everything from the rocket fuel, to the rocket itself, to a GPS guided parachute recovery system. [J. M. Hopkins] has already accomplished two of his goals, making his own fuel and testing nozzle designs. The electronics package to be included on the rocket is impressive, including a GPS, IMU, barometric, and temperature sensors. Data will be sent back to the ground by a 70cm transceiver. The ground station will use a high gain human-guided yagi tracking antenna with a low noise amplifier to pick up the signal.

If you want more rocketry goodness, check out our brand new rocket project list! Rocket projects move fast, if I missed yours as it streaked by, don’t hesitate to drop me a message on Hackaday.io. That’s it for this week’s Hacklet, As always, see you next week. Same hack time, same hack channel, bringing you the best of Hackaday.io!


Filed under: Hackaday Columns

Open Source 3D Printed Rocket Engine controlled by Arduino

Fubar Hackerspace (New Jersey) member Graham has been working on an open source liquid fuel rocket engine with regenerative cooling and precise flow control built on Arduino Uno.  In order to test it he’s also built a cool rig for testing propellant flow control:

My project is building Open Source 3D Printed Rocket Engines with Arduino microcontrollers. As an individual interested in building liquid fueled rocket engines as a hobby I quickly realized there were almost no resources online or forums to share or learn from others. I decided to combine my interests in Software, hardware and open source projects to develop and build a functioning liquid fueled rocket engine. However, unlike most other projects it had to be open source and easily re-produced.

In order to ensure it was as open source as possible I used the Arduino Uno board and IDE to develop software to safely control the engine. To meet the easily reproducible requirement I decided that 3D printing was the right approach rather than labor/time intensive traditional machining.

The end result is an engine that can easily be reproduced or modified. This gives others interested in this hobby a starting point for best practices, safety, etc… so that future projects aren’t starting out from scratch.

All of my design files and software are on GitHub  and a detailed description of the write-up is on the FUBAR labs makerspace wiki 

Here’s the video of the testing of the 3D Printed GOX/Ethanol Injector:

Arduino Blog 27 Feb 09:58

Open Source 3D Printed Rocket Engines controlled by Arduino

Fubar Hackerspace (New Jersey) member Graham has been working on an open source liquid fuel rocket engine with regenerative cooling and precise flow control build on Arduino Uno.  In order to test it he’s also built a cool rig for testing propellant flow control:

My project is building Open Source 3D Printed Rocket Engines with Arduino microcontrollers. As an individual interested in building liquid fueled rocket engines as a hobby I quickly realized there were almost no resources online or forums to share or learn from others. I decided to combine my interests in Software, hardware and open source projects to develop and build a functioning liquid fueled rocket engine. However, unlike most other projects it had to be open source and easily re-produced.

In order to ensure it was as open source as possible I used the Arduino Uno board and IDE to develop software to safely control the engine. To meet the easily reproducible requirement I decided that 3D printing was the right approach rather than labor/time intensive traditional machining.

The end result is an engine that can easily be reproduced or modified. This gives others interested in this hobby a starting point for best practices, safety, etc… so that future projects aren’t starting out from scratch.

All of my design files and software are on GitHub  and a detailed description of the write-up is on the FUBAR labs makerspace wiki 

Here’s the video of the testing of the 3D Printed GOX/Ethanol Injector:

Arduino Blog 27 Feb 09:58

Nerf gun progress

The Nerf gun prototype is coming along nicely.  The students have tested the launcher up to 120 psi, built a prototype tilt and pan mechanism in Lego, and today hooked up a small reservoir behind the solenoid valve on the barrel to a bigger reservoir using an air hose.

They hope to be able to keep the bigger reservoir up to pressure by occasionally turning on a 12v compressor.  The compressor takes 10A and can’t be run for very long at a time (it brings the system up to 120psi  from 0psi in about 15 seconds), so they’ll have to run it off a relay.  I couldn’t find cheap relays that looked easy to use with 5v control and 12v 10A contacts, but automotive relays are cheap (I found 5 relays and 5 sockets for $5 on Amazon AGT (5 Pack) 30/40 AMP Relay Harness Spdt 12V Bosch Style (40AMP-HRNS)—even with shipping that is only $2.25 each for relay plus socket).  The relay can be controlled by half an H-bridge of the Hexmotor board.  The other half of the H-bridge controlling the solenoid should be fine, as we never need to run the compressor and fire at the same time—we can stop the compressor for a fraction of a second while firing.

They want to have the running of the compressor be automatic, which would require a pressure sensor.  The Freescale MPX5999D would work and is one of the few sensors I’ve seen with a large enough range, but I’m not sure how to mount it.  Standard tire-pressure monitoring sensors and transmitters are cool, but I don’t know if they go up to high enough pressures and I don’t know how to interface to their transmitters—that is almost certainly a more expensive solution. Honeywell has a differential sensor with ports that will go to ±150psi, which may be easier to connect up, but it costs about twice as much and is uncompensated and unamplified: I suspect it would be a lot fussier to work with than the Freescale part.  I’ve ordered a sample of the Freescale part, and read their AN936 application note on mounting (epoxy is your friend).

It turns out that the relays may be useful for other functions, like a linear actuator for the tilt mechanism. Two relays can be controlled from one H-bridge to get forward-backward-stop action on motors up to 30 amps (but no PWM!). Unfortunately, 12v linear actuators seem to run $100 and up, which is more that I want to spend on a single part.  I may ask the students to redesign—either building their own lead-screw mechanism or coming up with a different tilt mechanism.  I don’t think a simple servo motor will do—the beefiest one I have claims only 69 oz-in (0.49 Nm) of torque, which I don’t think will be enough to tilt the gun, even if they can get the hinge very close to the center of gravity.

Another problem has come up: getting more darts.  We have 5 darts that fit the barrel perfectly (1.45cm diameter).  There are plenty of darts sold like that, but they almost all now have larger heads on the end, and the heads don’t slide down the barrel.  The new Nerf clip-system darts are all mini-darts, that have a 0.5″ (1.25cm) diameter instead.  These do not fire well from the ½” PVC, which I measured as having an ID of 1.485cm (0.585″). A chart of PVC sizes I found on line says that 1/2″ ID Schedule 40 PVC is supposed to have an inside diameter of 0.622″, which is almost 5/8″, but that ID can vary by 10%, even along a single piece of pipe—only OD is held to tight specs.  Thicker-walled Schedule 80 is supposed to have 0.546″ ID, which would still be too loose for clip-system darts.

I see four possible solutions:

  • Find a source of (probably non-Nerf) foam darts that are 1.45cm (9/16″) diameter with heads that are no wider than the body. I think that they came with an NXT generation crossbow, so replacement foam darts for that may be what we need. They’re nowhere near as cheap as clip-system darts, but this is still probably the cheapest solution.
  • Buy Nerf  (or other) darts with the right size bodies but oversize heads, remove the heads, and make new ones (out of what?). This would be cheap, but tedious, and the darts would probably fly poorly, unless we made the new heads have a decent weight.
  • Use clip-system darts for compatibility with the popular Nerf guns, but find a smaller diameter tube than the ½” PVC pipe (where? and how would it be connected to the solenoid valve?) It looks like Schedule 40 3/8″ steel pipe has a inside diameter of 0.49″, which is just right, but steel pipe is rather heavy.
  • Use clip-system darts, but convert to the Nerf-standard tube-inside-the-dart launching system.  This limits the effective barrel length to the inside length of the dart (about 4.5cm) and the barrel diameter to the inside diameter of ¼”, which will limit the top speed of the darts (OK for safety, but probably not as much fun).

Filed under: Pressure gauge, Robotics Tagged: Arduino, foam darts, linear actuator, Nerf darts, Nerf gun, nerf guns, pressure sensor, relay, rocket

Nerf gun prototype 1

The Santa Cruz Robotics Club met again today, for the first time in over a month.  The current project is not the underwater ROV (we’re all getting very tired of waterproofing problems), but an automated Nerf gun.

The club members came up with some very ambitious plans for the Nerf gun (which included getting a Raspberry Pi and doing image processing to have a self-aiming gun), but I’m making them build quick-and-easy prototypes to try out their ideas one step at a time.  I don’t think I can get an Raspberry Pi this summer—the companies doing the distribution aren’t taking more orders (just expressions of interest) and they don’t expect to clear the current backlog until September at the soonest.  They are doing batches of 100,000 units, and that doesn’t seem to be enough to shrink the lead time—if anything, the lead time is growing.

So, giving up on image processing for this summer, there are still a lot of things to build.  For today’s four-hour meeting (which included a 1-hour trip to the hardware store and a fifteen-minute snack break), the goal was simply to test out the basic launcher concept: an air reservoir pressurized by a bike pump, a solenoid valve, and a barrel.

The first prototype. The air reservoir is about 18″ of 1-½” PVC pipe on the left, and the barrel is about 24″ of ½” PVC pipe on the right.

The biggest problem was that the valve has ¾” male pipe threads, but we wanted 1-½” PVC pipe for the reservoir (because we had a piece handy—we may build a bigger reservoir later) and ½” PVC pipe for the barrel (because Nerf darts just fit inside—probably Nerf guns were prototyped with PVC barrels).  Our hardware store run was to get threaded adapters to make things fit.We wanted everything to be joined with screw threads, so that we could disassemble the components and replace them or add elbows as needed.

Note that the ½” PVC pipe is also a good size for compressed-air paper “rockets”.  The term “rocket” is a misnomer here, as all the acceleration occurs while the rocket is on the launcher—it is modeled more like a gun than like a rocket. (But my soda-bottle rocket simulator can model these paper bullets also.)  It would probably best to have a shorter barrel for doing rocket launching—just the length of the rocket and no more, since the longer barrel results in more pressure loss with no gain in launch speed.

The bicycle valve glued into a ½” female-threaded end cap was one I’ve had for a long time, as part of a soda-bottle rocket launcher. I had two of them, and both failed in testing today (the Barge cement holding the valve stem in failed—we’ve now reglued them with a different cement), though we managed some testing before the failure.

The solenoid valve we used was the same model (sold by Sparkfun) as the one used for the vacuum bottle on the ROV.  It has ¾” male pipe threads on each side.  To make it air-tight we had to disassemble it and grease the rubber membrane thoroughly with vaseline or faucet grease, but we had done that months ago, so it did not need to be done today.  The valve only works in one direction, but the high-pressure side is clearly marked by a metal intake screen, so assembling it the right way around is easy.

I was not sure that the solenoid valve would work in this application. It is not the model of valve that the compressed-air “rocket” people have used—those valves cost about twice as much and have female threaded ends rather than male threaded ends. I think that the mechanism they use may open up a bigger channel for air or water than the cheap solenoid valve sold by Sparkfun.

My first concern was that I did not know whether the valve would open up wide enough and fast enough to let a blast of air through to get a clean launch.  Second, I did not know whether we could open and close the valve fast enough to retain pressure in the reservoir for doing multiple shots.

We controlled the solenoid valve with an Arduino and the Hexmotor motor-control board (which is really overkill for one solenoid—a single power transistor would be enough to interface the Arduino to a solenoid, but I did not have one handy).  My son wrote an Arduino program to allow us to experiment with the duration of the solenoid pulse.  If it were too short, the Nerf dart would not leave the barrel.  If it were too long, air pressure would be wasted.  He allowed for 100 µsec increments in pulse duration, under control from commands on the USB serial line.

Because the glue they used takes 24 hours to set properly, we only tested at low pressure today (20–30 psi).  At those pressures, a 16 msec pulse was not long enough for the dart to clear the barrel, but a 19.2 msec pulse was easily long enough. We were also able to launch a 14g paper “rocket” left over from Maker Faire, though it did not go as high as the approximately 1.6g “Nerf” darts (I think several of the foam darts we have a different brand). We would not have expected it to go as high, since it was only accelerated for its 11″ length, not the 24″ length of the barrel for the darts, and it weighed a lot more.

One thing I thought about was monitoring the air pressure in the reservoir electronically. I doubt that we’ll put a pressure sensor in the reservoir, though, as the sensors I have only go up to 250 kPa absolute (about 21 psi above atmospheric pressure—about as low as we could fire with).  Freescale makes a 145psi (1000 kPa) sensor, the MPX5999D, but it is a differential sensor without port tubes (so would be difficult to mount) and it costs $13.

Perhaps the other thing worth doing today is to analyze how fast the Nerf dart should be going as it leaves the barrel, and how high it should fly if we shoot it straight up.  The physics here is fairly simple, if we assume that opening the solenoid valves connects us to a constant-pressure source. (In practice, we saw about a 10psi or 70kPa drop in pressure after one shot. If the pressure is P, then the force on the dart is P*area.  The cross-sectional area of the foam dart is a little hard to measure, because of the squishiness of the foam, but the inside diameter of the barrel is 1.45cm, for a cross-sectional area of 1.65 cm^2. At 140 kPa (about 20 psi), the force on the dart would be 23 Newtons.  That force is applied for about 60 cm (the length of the barrel), for a total energy of about 14 Joules.

We can use the kinetic energy of the dart to get its speed (E = ½ m v2), so for 140 kPa, the dart should leave the barrel at about 130 m/s or 290 mph. I suspect that we are not getting anywhere near that speed, for several reasons, including leakage of air around the dart, limited speed of air moving through the valve, and friction of the dart in the barrel (mainly from the pressure wave in front of it, but also from rubbing on the sides of the barrel).

We can also use the kinetic energy of the dart to estimate how high it would fly (ignoring air resistance, which is obviously hugely important for a low density object like a foam dart). The potential energy of a mass at height h is , so the height it would go without air resistance is . For 14 Joules and 1.6 grams, that would be almost 900m. I think that 20m is a more reasonable estimate for the height the dart went, though I never could see it near the top of its trajectory.

I tried adding the specs for the Nerf dart and a 60cm barrel to my rocket simulator (to get a crude estimate of the effect of air drag), and for 140 kPa I got an estimated max speed of 132m/s and an estimated max height of 52.6m. I don’t know if that height is reasonable—certainly it is better than the no-air-resistance estimate. The 6.78 second estimated time of flight seems to be fairly reasonable, though we never timed it.

Doubling the pressure increases the maximum velocity by a factor of 1.414, but only increases the maximum height to 60.8 m, a 16% increase. Doubling the barrel length has about the same effect. Air drag is what determines the speed of the dart, and that is the least well-modeled part of my simulation.

On Thursday, when they club meets again, they’ll try experimenting with higher pressures, and see whether 17 or 18 msec pulses are long enough—the shorter the pulse the less air will be wasted, and the more shots they can make from the reservoir.  It may be necessary to design a bigger reservoir or add a compressor to the design, since they eventually want a fully automatic Nerf gun, not the one-shot muzzle-loader that they made as the prototype today.  They’ll also start designing a pan-tilt mechanism for the Nerf gun, probably prototyping it out of Lego Technic components.


Filed under: Robotics Tagged: Arduino, Nerf gun, nerf guns, physics, rocket, simulation, SparkFun Electronics

Rocket Brand Studios Tiny Wheels

Primary image

What does it do?

Autonomous

Drawing on the popularity of the Tiny Tank, I decided that some folks might want wheels instead. I give you, Little Wheels.

The Little Wheels Robot is a great little bot for beginners and experienced robot builders alike. Simple, well designed and cute as a button, it is just a gosh darn good little bot.

Features:

Cost to build

Embedded video

Finished project

Number

Time to build

Type

wheels

URL to more information

Weight

251 grams

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