What good is it having a blog without some pretty pictures?
I really need to get out and fly again… haven’t tried since BALLS, I think. Oh well. Here’s some old ones… like here, when things go right… a 98mm N motor with 42″ of propellant (82% solids, 6% Al with a dash of CuO) pushing my school’s rocket “Del Carbon”, made using the techniques I talked about in the composite layups post (yay shameless trackback #2…)

Here’s when things go wrong. We (me and the school group) tried to do a carbon fiber cased O motor, but we had a “peel failure” between the casing layers. The case delaminated and allowed the forward bulkhead to fly out on pressure-up, absolutely torching Les Derkovitz’s rail. We’re still sorry, Les:

Whew. Glad the Flickr integration works well too.

I added text on Vacuum Bagging to the Composite Layups post. It’s a bit tedious without pictures; hopefully I can get a few tomorrow or the next day to help out a bit. Go tear it apart and let me know what needs to be added!

This is the motor that started it all. We got our name at this event, and this motor was the first motor to be fired with the “TDK Propulsion” branding on the flight card. Joe Cox, Charlie Cox, and SpartaChris (aka Chris Williams) built this 12″ Talon, and Todd and I provided the power plant:

The motor worked well, although the rough deployment at apogee caused the casing to be kicked and subsequently damaged upon landing. A new one is ready to go on the lathe, though, so no worries.Lessons learned:

• Use a stronger motor retainer — 6″ hardware is heavy, no matter what Todd says.
• Forward insulation is a good thing — the bulkhead of the motor got a little toasty and actually melted in one spot. It’s now in the BURP bin. Apparently the larger hardware produces more heat than can be carried away (volume goes up by the cube, surface area by the square…) so this makes sense, as we haven’t seen this on smaller motors, and the aluminum content of this propellant wasn’t inordinately high (5%).
• Aft insulation disks work great — we used 1/16″ G10 on top of the nozzle carrier to protect it from the same fate the bulkhead suffered.
• Nozzle carriers work great, too — this motor had a nozzle made from a 3.75″ diameter chunk of graphite for the nozzle insert, held in place by an aluminum nozzle carrier. We expanded the exit cone into the nozzle carrier a bit, which surprisingly wasn’t harmed by the exhaust flame one bit. I still don’t understand why it doesn’t melt — maybe the flow velocity is so high that it doesn’t have time to heat soak the part. Either way, carriers work. Save a graphite tree and use them. CAD drawings forthcoming.

I’ve grown pretty decent over the years at creating composite aerostructures. From my first attempt at fiberglassing a body tube to the latest projects with prepreg and vacuum bagging, I figure it might be fun to share my version of creating composite structures with the world. Read on »