Hybrid rocket engine uses acrylic as fuel

We are fascinated by the hybrid rocket engine which [Ben Krasnow] built and tested in his shop. It is actually using a hollow cylinder of acrylic as the fuel, with gaseous oxygen as an oxidizer. We’re already quite familiar with solid rocket propellant, but this hybrid approach is much different.

When a rocket motor using solid propellant is lit it continues to burn until all of the fuel is consumed. That is not the case with this design. The acrylic is actually burning, but if the flow of oxygen is cut off it will go out and can be ignited later. This also opens up the possibility of adjusting thrust by regulating the pressure of the oxygen feed.

[Ben] milled the test rig in his shop. It’s a fat acrylic rod through which he bored a hole. There are two aluminum plates which complete either end of the chamber. The intake has a fitting for a valve which connects to the oxygen tank. There is a nozzle on the outflow end. Check out the video after the break to see a full description. You’ll also get a look at the toll the combustion heat takes on the rig.

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Rocket propellant manufactured from old newspaper

It turns out that old newsprint can be a bit explosive; at least when it’s combined with the proper ingredients. [Markus Bindhammer] worked out a way to make solid rocket propellant from newspaper. Judging from the test footage after the break the home made engines work great!

There isn’t a long list of ingredients. In addition to newspaper you’ll need some potassium chlorate (KClO3) which serves as an oxidizer, white wood glue, and PVC pipe. The KClO3 is ground with a mortar and pestle, then run through a sieve before being combined with the wood glue. This combination is painted on the newspaper which is then rolled up with a glass rod at the center. This is allowed to harden before going into the PVC. The excess is trimmed and the whole thing is baked in a convection oven at 105 C for two hours.

If this process doesn’t suit you maybe cooking up a batch of sugar-based propellant is worth a try?

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Hackaday Links: July 25, 2012

Ever wonder what CPU dev boards look like?

In the realm of highly confidential hardware, it doesn’t get much more secret than upcoming CPUs coming out of Intel. Somehow, a few CPU dev boards wound up on eBay, and [Leon] was cool enough to save all the pictures (Polish, Google translation, or translate in the sidebar). There are a few ongoing auctions right now, but we’d settle for this LGA 1156 breakout board. So cool.

No, we’re not linking directly to the free stuff

TI is giving away a brushless motor controller powered by a Stellaris ARM processor. [Chris] says he’s ordering one to figure out how to make a Stellaris dev board out of the giveaway. This controller is designed for e-bikes, so at the very least we see a few ginormous UAVs in someone’s future.

More rocket stuff!

One of [Bill]‘s older hacks was taking a CVS disposable digital camera (remember that?) and stuffing it into the nose code of an Estes D-powered rocket. There’s a ton of videos of the flights [Bill] put up on YouTube.

On another note, [CyberPunk] built a half-scale model of a swing-wing rocket launched glider (pics: 1, 2, 3, 4). He’s currently building the full-size version capable of carrying RC and video gear and wants some feedback.

So, CAD on a tablet?

[spuder] caught wind of a tablet-based engineering notebook a few people are working on. They’re looking for some feedback on their demo video. We think it’s cool – especially the ability to share stuff between devices – but CAD on a tablet makes us extremely skeptical. Tell them what you think; we’d love to see this make it to our phone.

Now if they only made one for editing WordPress posts….

Test-driven development just got cooler. Here’s a Tamagotchi for Eclipse that you ‘feed’ by going from red to green and refactoring your code. Be careful, because having the same code test as red twice will kill your little code ninja.

And now I’ll rant about you.

A few days ago, I posted [Becky Stern]‘s light-up handlebars project, and one comment surprised me. Who says guys can’t sew? It’s time to confront the gender roles that show up whenever sewing is used in a project. I’m doing a tutorial on how to sew a parachute, but I need your help. It’ll be a two-parter: one on how to actually use a sewing machine, and another for how to make a ‘chute. Is there anything else you’d like to see?

Firing rocket engines in the wrong direction — this is only a test

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.

Rocket telemetry from UAV hardware

When we posted our call for rocketry hacks and builds, we expected to see a few altitude sensors and maybe a GPS module or two. Apparently, we forgot similar hardware is very popular in the remote-controlled aircraft world, and can be successfully added to a rocket as [Kevin] and his ArduPilot equipped J motor rocket showed us

The ArduPilot is a small Arduino comparable board designed for UAVs, quadcopters, and other whirligigs not powered by rocket motors. To get real-time telemetry from his rocket, [Kevin] attached a GPS receiver and an XBee transmitter. When launched on an H165 motor, [Kevin] was able to keep a radio lock on his rocket, allowing him to pull down data in real-time.

There are a few drawbacks to using the ArduPilot to collect flight data; the ArduPilot only reports ground speed, a somewhat useless feature if the vehicle is going straight up. Also, there is no way for [Kevin] to record data to an SD card; the ground team must be able to receive the XBee, lest bits of data go missing. For most rockets the radio issue shouldn’t be a problem. [Kevin] launched the same hardware on a J motor and was able to receive data from 3600 AGL.

Launching rockets and recording video

Since we put out a call for model and amateur rocketry hacks, we’ve been getting a lot of submissions on our tip line. Here’s two that found their way to us yesterday:

Upgrading an original

Back in the early 70s, Estes released a rocket with an 8mm movie camera attached to the nose of the rocket. It was called the Estes Cineroc, and is an excellent demonstration of engineering prowess to fit a movie camera inside a cardboard tube. The Cineroc is somewhat of a collector’s item, so of course there’s a reproduction kit with a payload bay large enough for [Bob Marchese]‘s 808 key fob video camera. His launch video looks awesome, has color, and doesn’t need to be mailed off to Estes to be developed.

Much better than a lightbulb and a button

Remember the old yellow (or blue, and I think maybe a red one) push-button launch controller? Equipped with an arming key (a piece of wire), batteries, and a button, that controller wasn’t much to write home about. [Joe Niven] built his own launch controller with multiple LED lights, buzzer, continuity checker, and a battery tester. Not bad for a 555 and a pair of 4000-series logic chips.

Two-stage rocket climbs to 15 km, promptly gets lost

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.

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