THK "Pollux" Solid Fuel Booster

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THK "Pollux" Solid Fuel Booster
Part image
Solid rocket booster by

Radial size Medium, Radial mounted
Cost (total) 6 000.00 Funds
(dry) 2 520.00 Funds
Mass (total) 51.50 t
(dry) 8.00 t
Drag 0.2-0.3
Max. Temp. 2200 K
Volume  ?
Impact Tolerance 9 m/s
Research Tech tree heavy rocketry.png Heavy Rocketry
Unlock cost 15 000 Funds
Since version 1.8
Part configuration solidBoosterTHK.cfg
Solid rocket booster
Maximum thrust (1 atm) 1 155.56 kN
(vacuum) 1 300.00 kN
Isp (1 atm) 200 s
(vacuum) 225 s
Fuel consumption 78.56 Units of fuel/s

Thrust vectoring No
Fuel 5800.0 Units of fuel
Burn time (1 atm) 65.6 s
(vacuum) 73.8 s

The THK "Pollux" Solid Fuel Booster is a solid rocket booster (also known as an SRB) used to provide a short burst of additional thrust to a rocket. It comes as a single unit. The engine and fuel tank are one single part which means that it isn't possible to increase the burn time for it by adding more fuel tanks.

It is the only 1.875m solid rocket booster.

Product description

The Pollux is an engineers best friend. Is your rocket a little too low thrust to get off the pad efficiently? Put one on. Still not enough? Put on a pair. Try six of them if that's still not enough. Or if you're feeling really craft, you can launch your entire rocket with just these tried and true solid rocket motors.



Like other SRBs, the Pollux can be fired once, and cannot be shut down or throttled once active. While assembling a vessel, it is possible to adjust the amount of solid fuel and thrust using tweakables in the VAB or SPH. If planned properly, this can provide some control during flight.

Once ignited, a Pollux with full fuel and thrust will burn for 73.8 s. If jettisoned while empty, it can parachute to a safe landing with three Mk2-R Radial-Mount Parachutes.

The minimum thrust required for the Pollux to lift its own weight off Kerbin's surface at sea level is about 44%, or about 505.2 kN.

The Pollux can be radially mounted like other SRBs to increase thrust and TWR during liftoff. Due to its large size and thrust, it can also be used as a standalone first stage, mounted below the rocket.

In career mode, the Pollux is unusually cost effective for many use cases; it delivers a greater impulse per cost to an attached rocket than any other solid booster does.


  • Initial Release