We've been collecting 2L bottles from friends and family over the last couple of months to make up more spliced pairs for the new Acceleron booster. After we had a few leak problems with the last spliced-pair batch we're now trying the sikaflex glue as a sealant in the joint area but PL premium as the main glue that holds the splice together.
All up Acceleron V has three segments in the cluster and each segment uses 3 x 2L spliced pairs giving a total volume of almost 33 liters. Up until now we have been using 10mm nozzles on the Acceleron boosters but with the larger volume and larger weight of water we have decided to go with the larger 13mm nozzles we use with our drop away boosters. Including the second stage, the total liftoff weight is now going to be approaching 16 kilos. Switching to the new nozzles would have also meant that we would have to machine new nozzle seats for the old Acceleron launcher.
Instead we decided to adapt the booster launcher to work with the Acceleron rocket. The old Acceleron rocket uses a speargun release mechanism, so we are replacing this with custom made aluminium gardena nozzle mounted on the baseplate that holds the cluster together. This nozzle will fit into the existing Gardena central release head.
Because this launcher's minimum nozzle spacing does not allow the three segments to be up against each other like in the old Acceleron rocket, we are going to separate the cluster segments further from each other. This will require a new baseplate for the cluster. This again will be made from aluminium and reinforced with fiberglass. By separating the cluster segments we will be able to lower the second stage release mechanism pod further down in between the segments allowing the second stage to also sit lower in the booster. This will help partially solve one of the problems we've been having with the old Acceleron rockets, namely the stability of the second stage on the end of the staging mechanism. The length of the Acceleron booster and the location of the staging mechanism prevented us from making the second stage any longer. If the second stage had been much longer there was the danger of snapping the rocket at the staging mechanism during the boost phase. By lowering the second stage between the segments, we can use the segments themselves as guide rails for the second stage. This will allow us to build a second stage around the length of an Axion or Hyperon rocket.
The second stage will be pressurised through the central release head allowing it to use a different pressure to the 1st stage. The Acceleron parachute(s) will now be located in the space between the spliced pairs.
With the second stage supported by the segments, it will also mean that the second stage can have a boat tail for better drag efficiency.