The SS2S team completed an initial feasibility study and is currently in the design phase. They are also actively building a 1/4-scale motor. Due to technical and regulatory concerns, they could not go with a multi-stage rocket, so they will use a 2-phase segmented motor. In this type motor, the lower part of the propellant burns (phase 1), there is a coast period while a delay grain burns, and then the top portion of the motor ignites (phase 2).
Here is a summary of the preliminary vehicle specs:
- Number of stages: 1 (dual-phase operation)
- Vehicle size: 10" (25.5 cm) diameter by 26' (7.9 m) overall length
- Liftoff mass 1100 lbs (495 kg).
- Allotted payload mass 15 lbs (6.8 kg).
- Full vehicle recovery
- Propellant type, cast Potassium Nitrate/Sorbitol (KNSB)
- Propellant mass 885 lbs (402 kg), consisting of 6 BATES segments per phase (12 total)
- Burn time 8.5 seconds each phase (17 sec. total)
- Motor average thrust, 6665 lbf (29.6 kN)
- Coast time between firings, 16 seconds











2 comments:
How does the coast phase improve performance? Does it reduce drag losses?
You are correct. Aerodynamic drag is proportional to air density and the square of the velocity. Thus, is is beneficial to let the rocket coast prior to 'second stage' ignition.
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