Design and Development of Solid Rocket Boosters
If you follow space news, you probably know that plenty of modern rockets rely on liquid fuels these days. Still, it was solid rocket booster technology that paved our way to the stars. The term “solid” means that a rocket is powered by solid fuels. Even now, there is no universal solid rocket booster design because this type of engine can be used either as a side thruster or a rocket upper stage. If you have ever watched a rocket launch, you probably know that this technology is loud and showy. Think of Space Shuttle launches, with all that flames coming out of the nozzles. A launch site is enveloped in smoke, and the rocket makes noises that are almost unbearable. And while these boosters are surely impressive to watch at launch, what do we know about them?
Solid rocket boosters ensure that rockets have enough impulse in the beginning stages of their flight. They contribute to developing the thrust that’s needed, and they work briefly for only about two or three minutes. These engines are simple in their operation and design because the solid rocket booster development process involves using an engine together with a fuel tank. But there is more to this tech than meets the eye.
How are solid rocket boosters made?
Solid rocket motors integrate every subsystem that’s needed for the ascent, entry, and flight of the motor system. They include avionics, structures, pyrotechnics, thrust vector control, deceleration, range safety, retrieval systems, and thermal protection. Actual boosters are made from the same materials and follow the same logic as the entire rocket. It’s a simple and reliable method, but not without its drawbacks.
Solid fuel systems are effective but not recoverable, which is the primary challenge with such boosters. More challenges include thermal environments, subsystem integration, and severe loads. Some subsystems evolved during programs that involved design changes. Most recent design changes were made to parachutes, range safety systems, thermal protection systems, and a few other systems as well. However, despite the relative simplicity of operations, solid stages are unrecoverable and are prone to ignite on accident, endangering spacecraft and its crew. In this regard, liquid fuels may offer a reusable and less accident-prone alternative, but this technology also has its drawbacks.
How does a solid-fuel rocket booster work?
Solid engines won’t be abandoned for as long as there are solid fuels to propel rockets. These engine boosters ensure higher thrust, so these boosters are perfect for carrying heavier payloads. Let’s consider Elon Musk’s approach if you want to learn better about solid rocket booster opponents. Musk thinks solid boosters are not necessary, mostly because they are impossible to recover and reuse. Since such types of boosters don’t adjust thrusts and are not re-ignited, it’s impossible to control land them as well. While experiences with shuttles prove that some solid boosters can be restored, this option is too expensive and doesn’t work.
A solid rocket booster operates in parallel with the main engines. This happens for the flight’s first two minutes, and the additional thrust that’s necessary for an Orbiter to escape the Earth’s gravitational pull is achieved. The rocket booster’s solid fuel is usually aluminum-based. It’s the same type of Aluminium that’s found in kitchen foil wraps, but it also features Oxygen from the ammonium perchlorate chemical.
What is the most powerful solid rocket booster?
Until 2011, the most powerful rocket booster was a space shuttle booster. However, after the space shuttle program closed, Ariane 5 solid engines took over. NASA was, in the meantime, engaged in the development of a new Space Launch System (SLS), and this system was all about implementing the best shuttle tech to surpass former technology. To not use a 4-segment accelerator, an SLS instead uses a 5-segment solid propellant. The propellant is not as toxic as HTPB. And this propellant is called polybutadiene acrylonitrile (PBAN).
PBAN provides 25% more fuelling and improves avionics. When there are liquid propulsion engines involved as well, SLS turns into the most powerful rocket in the world, says NASA. Such boosters could have us returning to the Moon at some point. NASA scheduled its first SLS test launch back in August 2022, but it delayed it for about 40 minutes because there were problems with an engine. So, as can be clearly seen here, solid boosters can still cause certain problems. And their power is determined only by the technology used when building them.
However, solid fuel (unlike liquid one) does not call for complex ground infrastructure, which is very expensive to build. So, even though solid booster tech is old-school and without a flaw, it looks like it will remain relevant — especially if we consider that NASA is still betting on it with its new SLS project.