The team at Spark Rocket Labs has a goal to send a rocket with a 1 kg payload past the Karman line and recover it. To reach that goal, we have an intermediate goal of designing and flying a minimum-diameter platform that can be used as a test bed for sustainer design. That platform is the SPARK-S4 rocket.
The SPARK-S4 (Solid Propulsion & Ascent Research Kit – Sustainer 4 in) is a modular, minimum-diameter system that breaks the fin can, motor tube, electronics bay, and recovery systems into separate systems that can be swapped and upgraded as necessary.
Specifications
| Length | 78.5 in |
| Weight without motor | 14 lb |
| Motor mount | 98 mm minimum diameter (can adapt down to 54 mm) |
| Body | Filament-wound fiberglass tube and nosecone |
| Fins | 4-fin aluminum Max-Q fin can |
| Primary flight computer | Blue Raven |
| Backup flight computer | Raven 4 |
| Telemetry | Featherweight GPS tracker |
| Cameras | Three Runcam Thumb Pro, 2.7K @ 60 fps (forward, rearward, and straight) |
| Drogue | Rocketman Experimental Drogue 2 ft |
| Main | Rocketman High Performance Cd 2.2 parachute |
| Ejection | Tinder Rocketry Peregrine 12 g |
| Main release | Tinder Rocketry TD-2 explosive bolt |
The sequencing below shows the basic recovery system components and function in cutaway form. The payload airframe is not shown and the rest of the rocket below the recovery plate is hidden. These pictures illustrate the general concept and may not match the final hardware exactly.
Recovery systems package overview
The main shock cord is packed against the av-bay bulkhead. The main chute is packed in a deployment bag and that going in next. A 24 in drogue chute is attached 5 ft down from a 35 ft long 1/4 in tubular Kevlar harness. The end of the harness is connected to the TD-2 pin and the top of the main deployment bag. The main chute is attached to the end of a 10 ft long 1/4 in tubular Kevlar harness. The Kevlar harnesses are attached via 1/4 in stainless steel quick links to 1 3/8 in stainless steel eye bolts on the av-bay bulkhead and main bulkhead.
At apogee
At apogee, a 12 g CO2 charge from the Peregrine system will separate the nosecone from the payload tube / AV bay. There is a backup Peregrine system that will fire 0.5 seconds after the main Peregrine charge fires. The nosecone is held in place with three #2-56 shear pins to prevent premature deployment.
Descent
The two halves of the rocket will fall at an estimated 60 ft/sec until the barometric altimeter senses 700 ft AGL. The TD-2 still has the pin engaged at this time, which keeps the drogue from pulling the main out and also keeps the rocket together.
Main release
At 700 ft the Ravens fire an ematch in the base of the TD-2. That ematch drives a piston forward which releases the TD-2 pin. The drogue chute will pull the main chute in the deployment bag out of the body.
Landing
The drogue chute continues to pull the deployment bag off of the main chute. The deployment bag allows for a quick, gentle deployment. After deployment of the main chute, the booster portion should descend approximately 16 ft/sec (estimated using manufacturer’s data and RockSim analysis). The nosecone will descend separately under the drogue chute at approximately 20 ft/sec.