STEP 4: BUILDING THE CORE STAGE LOWER SECTION
The lower part of the core stage is very similar to the side boosters, the only difference is the length. The most complex part is the top section with a change in diameter from 60 to 80mm. The top section will contain a payload compartment for the altimeter and the camera. I have re- calculated the core stage in Open Rocket with fins pushed 5 cm forward. Looks ugly but otherwise they would collide with the side booster fins.
Due to the stringers to keep the side boosters in place the stability is still low, only 0,5 caliber. Maybe I'll add some additional mass to the nose cone.
Mounting the Side Boosters
The connection will be very simple: Each side booster has two hooks which hook into a mount on the center core. The basic idea is that the side boosters provide more thrust than the center core and keep the hooks in place as long as the side booster engines are running. As soon as the side booster engines cut off, the core stage will be released. The picture shows a test prototype.
Complete Lower Section
And here for the first time the complete lower section of the "Falcon Not So Heavy" with its side boosters mounted. Bothe sides boosters have 70 cm parachutes stored directly below the nose cone, the center core parachute will stored in the upper section of the core stage.