LOHAN fires up sizzling thruster
First test of Vulture 2 powerplant
Video Things are moving apace at the Low Orbit Helium Assisted Navigator (LOHAN) headquarters, and last weekend we did a first test firing of the proposed powerplanet for the Vulture 2 spaceplane.
As regular readers will know, we're currently working on the Rocketry Experimental High Altitude Barosimulator (REHAB) experiment, to see if the motor will fire at low pressure and temperature.
However, we thought we'd check out a couple of other performance parameters before sticking LOHAN in REHAB, namely the thrust and external casing temperature. Both are important considerations for our Southampton Uni Vulture 2 design team.
Here's the motor with its G-class reload (clockwise from left: reload, motor case, sealing ring, end cap and nozzle)...
The reload kit comes with an AeroTech Copperhead ignitor, but since they're legendarily so fragile that just looking at one the wrong way will cause it to fail, we kept it in its cardboard shipping tube until absolutely necessary.
For measuring the temperature, we hooked up a K-type ring thermocouple to a digital thermometer...
...and here's our apprentice boffin Katarina with the assembled test rig:
As you can see, we attached the motor to a large block of wood by means of some steel pipe clips, although it isn't clamped in hard, meaning it can move up and down freely.
The motor is sitting on a set of electronic kitchen scales. The vertical configuration of the motor is because the scales will only work when horizontal. At the top, you can see the connections for the Copperhead ignitor, running ultimately to an ignitor box and a big 12V car battery.
Solid-fuel rockets, cold temperatures and O-rings...
I seem to recall hearing something about that combination... now where was it...?
...sorry... ...just leaving...
An alternative igniter
Big Clive has an igniter here - extremely cheap, probably very reliable, but does require a 12v power source:
Copperheads are more commonly known as "Crapperheads". Essentially they are double sided copper clad filmwire cut in to narrow strips with one end stamped in to a zigzag crinkled shape for about 5 to 10mm and then dipped in a pyrogen. Which, I think, is mixed with carbon to make it slightly conductive/give it enough resistance. As mentioned they are notoriously unreliable.. Often fine copper whiskers from their being guillotined in to strips short the two copper layers out.
Look for e-matches like Davyfires or similar. These are the proper tool for the job.
Also there should'nt be any heat issue with the casing temp. Part of the US regs (NFPA 1127 iirc) which the motors must meet to be allow them to be sold define max external temp the motor casing can reach. Also remember that most hobby rockets of the size that take these motors use a cardboard or phenolic impregnated paper/card motor tube for the motor mount. They dont have any issues with the temperature that the casing reaches.