Solid Rockets in Rocketry

What is Solid Rocket

Solid Propellant Rocket
1. A solid fuel-oxidizer mixture (propellant) is packed into the rocket, with a cylindrical hole in the middle. 2. An igniter combusts the surface of the propellant. 3. The cylindrical hole in the propellant acts as a combustion chamber. 4. The hot exhaust is choked at the throat, which, among other things, dictates the amount of thrust produced. 5. Exhaust exits the rocket.


Based on propellant used in rockets , We can classify the rocket propulsion into following categories.

1.Solid Propellant Rocket 

2.Liquid Propellant Rockets 

3.Hybrid Rockets ( solid+liquid )

Rockets propulsion works with fuel ignition.  And gets thrust by expelling mass at high speeds . For this we need propellant( fuel and oxidizer). In liquid propulsion we store oxidizer and  fuel in different tanks . But this is not a case with Solid Rockets. Obviously ,we can get good combustion efficiency when the fuel and oxidizer are mixed properly. We can mix liquids easily , but it is not for solid rockets .

Grain Propellant
Rocket motor Grain structure and thrust
Different Grain structures and respective thrust characteristics

For this reason, we have to mix oxidizer and fuel. And should cast the propellant into Grains. Grains are cross-sectional structures of solid propellants . Maintaining grain shapes result in thrust characteristics with time. Different structure shows different results. So we have to select the grain structure based on our requirements. Having space in center of grains creates more efficiency rather than completely gets filled with propellant.

Solid Rocket Propellants

The below are few widely propellants in missions.

Highly Efficient Fuels
  • APCP(Ammonium Perchlorate Composite Propellant) consists both fuel and oxidizer.
  • HTPB (Hydroxyl-terminated polybutadiene) a rubbery fuel which binds fuel and oxidizer.
Less efficient fuels: 
  • Gun powder(black powder): Carbon(fuel)+KNO3(oxidizer)+ Sulphur (stabilizer)
  • Zinc-Sulphur : Zinc(fuel)+Sulphur(oxidizer).

Solid Rockets Advantages 

  •  Less mechanically moving parts and complexity
  • Highly cost effective, best suitable as boosters

Drawbacks with Solid Rockets

  • Difficult to control:  As the fuel is solid and mixed before the launch , we can’t control fuel burnings in flight time. If it one’s ignited , it can’t stop burning. 
  • As Throttle control is difficult. This is not at all applicable for precise maneuvering in spacecraft or rockets.
  • Low Specific impulse.
Conclusion: If you wanna play with rockets , solid rockets are easier than liquid rockets in terms of both cost and complexity.
Stay Tuned to get more engineering of Rockets and Drones.

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