June 11, 2013
Bryan Palaszewski, a researcher and scientist at the NASA Glenn Research Center, gave a presentation on various concepts for advanced propulsion systems. In his presentation he discussed his current research of high performance propellants, specifically gelled fuels and high energy density materials, and a series of advanced space concepts ranging from a solar sail design to a nuclear thermal design.
In the beginning of his presentation, Bryan went over the basics of a rocket. He started off with the fundamental rocket equation and the definition of specific impulse (Isp), which is a measurement of efficiency of a rocket or jet engine and it is used to compare efficiencies of different rockets. Isp represents the force with respect to the amount of propellant used per unit time. With a higher Isp, a rocket can have a lower propellant flow rate to produce a given thrust which makes for a more efficient system. The common solid rocket has an Isp of 250 sec which is low compared to the Isp of more advanced concept designs such as 10000 sec Isp for ion thrusters. Bryan then talked about his research in using metalized gel propellant as a method of propelling rockets faster. These metalized gel propellants are denser, have a higher energy density, and produce a higher Isp than chemical rockets. Extensive research is being conducted to further the technology of these metalized gel propellants.
Next, Bryan described various conceptual designs for advanced propulsion systems. He first started off with the solar sail concept. The solar sail is a spacecraft with a large surface of mirrors that uses radiation pressure or solar pressure for propulsion. The radiation pressure is a combination of light and high speed ejected gases from a star which pushes on the large mirror surface to propel the spacecraft to high speeds. To achieve high speeds, however would take a long time due to the low force that the pressure exerts on the sail. Next, Bryan dove into more complex concepts. The Bussard Ramjet, which was theorized by Robert Bussard in 1960, is a ramjet variant of a fusion rocket which uses electromagnetic fields as a ram scoop to collect and compress hydrogen from space. The mass is collected and then constricted until thermonuclear fusion occurs. Then the magnetic field directs the energy from the fusion as thrust. Another design uses an ion thruster, a form of electric propulsion. Using electrostatic or electromagnetic forces, thrust is created by accelerating ions. While the thrust from an ion thruster is very low, the Isp is very high due to the high acceleration of the ions. Yet, another design that Bryan discussed was Project Orion, a nuclear propulsion concept. Simply put, this spacecraft ejects thermo-nuclear bombs out the back end and rides the shock waves from the explosion of the bomb.
Overall, Bryan has been doing some very interesting and complex research in the field of advanced propulsion. His research on metalized gel propellants may unlock a new method for high efficiency rockets for space exploration. Along with the gel propellants, there are a multitude of different advanced propulsion systems that are being researched in the hopes of making interplanetary travel more of a reality.