Solid Propulsion

Solid Propulsion

Solid Fuel

Solid-fuel rocket engines were the first engines created by man. They were invented by the Chinese in the 13th century and have been widely used since then. The "rocket's red glare" in the American National Anthem, which was written in the early 1800's, refers to the small solid-fuel rockets that were used to deliver bombs and incendiary devices during the War of 1812.

The creation of solid-fuel rocket engines is fairly simple. They are made up of solid (dry) chemicals that, when ignited, burn very rapidly but will not explode. The exhaust gasses are directed through a nozzle that helps control and direct the gasses, providing accurate and even thrust.

Although not generally used for interplanetary propulsion, solid chemical fuels are used in solid-rocket motors. Since solid-rocket motors cannot be throttled (turned off and on at will), they are of little use as a primary propulsion system for interplanetary missions. Solid-rocket motors are typically used in booster applications, to assist a spacecraft in lifting off from the Earth's surface.

Currently, the most visible example of solid-rocket motors can be seen on NASA's space shuttle. The two white solid-rocket boosters (SRBs) are mounted to either side of the orange external fuel tank, as shown in the image below. This image also shows the enormous plumes of toxic exhaust gasses that are created by the SRBs.

Propellants for solid-rocket motors are made from a wide variety of substances, selected for low cost, acceptable safety, and high performance. The selection is strongly affected by the specific application. Typical ingredients are ammonium perchlorate (a granular oxidizer), powdered aluminum (a fuel), and polybutadiene-acrylonitrile-acrylic acid (a fuel that is liquid during mixing and that polymerizes to a rubbery binder during curing). This combination is used in major U.S. space boosters (e.g., the space shuttle and the Titan). (Hoiberg, 2000)

Solid-fuel rocket engines have three important advantages over liquid-fuel engines:

• Simplicity
• Low cost
• Safety
• They also have two disadvantages:
• Thrust cannot be controlled
• Once ignited, the engine cannot be stopped or restarted

The disadvantages mean that solid-fuel rockets are useful for short-lifetime tasks (like missiles), or for booster systems. When you need to be able to control the engine, you must use a liquid propellant system.

 

 

Please email me anything you think would be a useful addition to this site. Your help will benefit the other people who visit this site.