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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Pulse Oximeter

[Mike] is building his own Pulse Oximeter which uses light to measure the oxygen saturation in blood. One collateral benefit of this measurement is that pulse rate can be calculated from the same data. The parts used for the detector include a red LED, infrared LED, and a TSL230R light intensity measuring chip. As explained in the video above, each LED is shined through the tip of your finger and onto the light sensor. The IR LED is used as a baseline and compared to the red LED, which has some of its intensity absorbed by the red blood in your finger. This is a pretty approachable biometric concept so you may want to start here before moving on to more involved biometric interfaces.

[Thanks Russ]

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