Head-End Ignition: A Successful Method

[OverTheTop]

Following my recently successful staging flight (O-M) I have written up the method I used for the HEI on the sustainer. For some insight on what I managed to assemble, have a look at this thread on the Australian Rocketry Forum:
https://forum.ausrocketry.com/viewtopic.php?f=8&t=6385



Further details on the flight, including stats and video, are available on this link:
https://forum.ausrocketry.com/viewtopic.php?f=6&t=5019&start=105

 

[tim cubbedge]

What’s your igniter pellet made out of? Also is that an ematch or something else.

 

[OverTheTop]

It is the standard igniter that comes with the CTI M2020 motors. I also added a single eMatch in parallel. They are both glued to a Blue Thunder grain. Details are stated in the link near the top of the original post.

 

[Cameron Anderson]

Is the face shield an Aussie thing? This is only the second time I've seen it, both with Aussies).

 

[OverTheTop]

Hi Cameron. With a fully primed motor being handled, with an augmented igniter, as I was hooking up the electronics to the HEI I would have been silly to not use it. It was a very nervous time for me. I forgot to take it off for the pre-flight pic, but it didn't hurt to be there either.

The University of Sydney team I am mentoring is the other place you have seen it. It was the outcome of their risk analysis that they should use the shields when handling the prepped rocket. My original suggestion was to wear safety glasses or shields when installing energetics. Personally I prefer the shield from a comfort POV. What you don't see in their pics is that they have hearing protection as well. There are a couple of rocketeers that have hearing deficits due to deployment charges going off when carrying rockets on their shoulders. I love their attitude to safety. They scored really well (including full points for safety ) at the recent Spaceport America Cup, taking out first place in the 10k' COTS category and also getting the highest score of all teams at the event. Info here: https://forum.ausrocketry.com/viewtopic.php?f=4&t=6404

 

[Cameron Anderson]

From an ejection charge point of view, a facemask does make sense.

I saw the Sydney team's video on FB, the rocket looked amazing.

I came across your build thread for your HEI. While requiring skill to manufacture, the theory isn't overly complicated and looks quite safe. I'm trying to think of way to do HEI on CTI 38mm motors and Aerotech 29mm and 38mm DMS/LMS motors. Without the aluminium forward closure to machine and tap, I'm at a loss. Drilling a hole through the delay grain, tossing an ignite through, and liberally slathering the top with epoxy seems straightforward but is successful less than half the time (based on threads I've read) and lacks a lockout. I really liked your capacitor to act almost as a buffer.

 

[OverTheTop]

I really liked your capacitor to act almost as a buffer.

The capacitor is not for buffering the igniter drive, but for ESD protection. Any fast-rising voltages on one lead will be coupled directly to the other lead, resulting in greatly reduced voltage across the igniter, making it less likely to be triggered by an ESD event.