Saturday, January 22, 2011

Review: Massive Gassive

This is a cluster rocket based on a Crayon bank, which will help eat up my stash of D12-0s. It has one central 24mm motor mount surrounded by a ring of six motor mounts. On three sides, there is an additional 24mm mount, for a total of 10. The name of this rocket just popped into my head one day. I hadn't heard or thought of this phrase for years. My thanks to The Greaseman!




The center seven tubes extend up into the crayon and terminate in a 54mm-98mm centering ring. This ring supports the 6 tubes that surround the central mount. The outer three motor tubes end at the body tube. The following photo shows the business-end with motors loaded.


The fins are made of Luan plywood. They are glued in the motor mount joints, and are slotted so they slide over the body tube. I glued the fins to the body tube using 5-minute epoxy and used PC-7 2-part epoxy paste to fill the gap between the motor mounts. I was not impressed with the latter. It was hard to work with and took a long time to dry. Once it was fully set, I added epoxy fillets.

I painted the fins with the new Krylon H2O latex paint. This paint is almost completely odorless and cleans with water. You still need to use it in a ventilated area due to the propellants used. It goes on thick, and evens out for a smooth finish. I painted in some wind and laid it on too thick (so what else is new?). The runs were easy to deal with and, unlike regular spray paint, the blotted runs evened back out. The real test will be the durability of the paint. If it holds up well, I will be using more of it.

Based on the RockSim model, I added 8 oz. of lead shot held in place with 2-part foam from Giant Leap. Ten D12's should be the equivalent of small H120 and should be pretty cool.

The rocket flew on 4/22/2005 at the 3rd Annual TRF Reunion. I used a central D12-5 with an augmented charge, and 9 D12-P motors. I lit all ten with quickmatch and one igniter.

The boost was fantastic up until burn-out when the cone drag separated, causing a massive zipper in the Massive Gassive. The following photos show the flight sequence.


Courtesy of Rocketmaniac


I normally would have replaced the entire upper portion of the tube, but since the crayon is a non-standard size I had to fix it. I first cut out the zippered area and made myself a stuffer tube (ie a full-length coupler) to fit in the crayon's body. Once the stuffer was in, I then matched the missing areas and cut out sections of scrap tubing to fill the gaps. If these had been as thick as the crayon tube, then I would have been a lot closer to complete. Since they weren't, I both filled the cracks between these pieces and built the area up with fill'n'finish. An epoxy based filler would have been better, but the f'n'f was easier and I had it on hand. Since the crayon's cone would no longer fit, I cut off the plastic shoulder and added a longer phenolic shoulder. It is glued into the cone and will also be held in by 4 screws. This photo shows the filled tube and the shoulder while the glue sets. The shoulder is hollow to allow for more chute room, and the cone will now come down o n a separate chute.



The Massive gassive flew again on 5/14/2005 at MDRA's ESL-85 and redeemed itself. I packed the main chute in the nose cone and held it it with a strip of masking tape. The nose cone's chute was wrapped in a chute protector and was loaded in the body. I added tape until the cone was quite snug. I'd have no drag separation today! The ten D12s lifted it to a nice altitude and it ejected near apogee, maybe a skosh early. Deployment was perfect. Missed the launch but here's the aftermath.


The most recent flight was at ESL-120. It flew on a central E9-6 and 9 D12's. Cool boost! We heard the ejection charge a couple of secs after apogee. A second later it came apart and recovered just fine. This was an '8' on the pucker factor scale.