An electric rocket engine is one of the most efficient and highly usable forms of propulsion technology in existence today. It’s main advantage over conventional types of rocket engines is that there is no need for an engine combustion chamber like with a solid-fuel rocket. Instead, the electric motor ignites its fuel at a high pressure and combustion occurs at a very high temperature. This means that there are no toxic particles or byproducts to deal with after the blast, making electric rocket motors highly reusable. The main disadvantage of using electric powered space vehicles is the relative inefficiency of such systems relative to traditional solid-fueled vehicles. Also, since an electric rocket engine requires no combustion chamber, reliability is greatly increased.
There are two general types of electric rocket engines; those that use liquid propane as the primary fuel, and those that use solid fuels. In the case of the latter, the liquid oxygen tank (oxygen tanks are also available for solid-fueled liquid rockets) and an air tank (which carry the oxygen) are included in the “rocket.” While liquid oxygen boosters are extremely reliable, they’re not as effective at getting a human spacecraft to the velocity needed for a manned mission.
A solid-fueled rocket is quite different. In this case, the oxidizer is actually part of the rocket, and a solid rocket is much less likely to undergo catastrophic failure than its liquid-fuel counterpart. One key design feature of solid-fueled versions is the use of a solid engine of some kind for propulsion. A solid-fuel rocket doesn’t lose its momentum along the way, and the engine burn times are significantly longer than for liquid-fueled counterparts. This is why solid-fueled models of various kinds have been used for years in applications where high energy-efficiency is a primary concern, such as research and experiments (atoms produce their own energy through nuclear reactions, and using them for propulsion does not make them expendable).
Electric Rocket Engine
An alternative type of propulsion to propel a rocket into space is a “closed cycle” system. The most well known is a solid rocket booster using liquid hydrogen (sometimes also containing oxygen) in a combustion chamber. As the boosters ignite, they produce thrust in the form of exhaust gas or exhaust flame. A liquid Epsom salt solution is sprayed onto the thrust areas, and as the Epsom salt solution itself burns, it generates a tremendous amount of thrust in the form of exhaust gases and burning waves. These systems are also used to power ion rocket engines.
Another type of electric propulsion used for space missions is electric thrusters. Electric thrusters can work in two distinctly different ways. In the first case, the electric motor (or its equivalent, a “stage” of wire harness) pushes a wire harness through a field into a thrusting position. In the second case, the electric thrusters convert mechanical force into electrical thrust.
The most efficient of these systems is the ionization method. This works by shooting ions (from an onboard battery) at a long metal tube inside the engine’s combustion chamber. The electric energy created in this process causes the metal tube to be propelled ahead of the thrust vector generated by the rocket engine, increasing the thrust of the spacecraft or vehicle.
In the case of electric propulsion using electric rocket thrusters, the spacecraft is commanded to leave the thrust vector at the end of the channel, where it will create an incredible amount of thrust on its own. It must be noted that the spacecraft must remain within the channel’s cross-section. The problem, however, is that if the vehicle is outside the section while using electric propulsion, there is no provision to use fuel-solen thrusters to achieve the needed thrust. Instead, the only method available is to fly the craft along a specially-designed trajectory.
The final type of electric propulsion system is the solid rocket concept. Unlike the ionic and plasma thruster methods, this concept relies on solid fuel. This includes solid-fueled boosters as well as fuel pellets onboard the craft for the purpose of boosting its forward momentum. When the booster is no longer needed to maintain the vehicle’s direction of flight, the process to de-orbitate the vehicle and cut-off its descent will be used. Once it is safe to eject from the rocket, this type of thruster is no longer required.