External Pulsed Plasma Propulsion (EPPP) is something that’s been discussed for some time. In fact, it was originally proposed by Stanislaw Ulam way back in 1947. Unfortunately the public perception of atomic technology as well as pieces of otherwise well meaning legislation have called into question the feasibility of spacecraft that operate using this advanced principle.
Acceleration gradient for a linear plasma wave is:
In this equation, E = electric field, C = speed of light in vacuum, me = mass of the electron, ρ = plasma density, and ε0 = permttivity of free space [source: icfa-usa.jlab.org].
Inertial confinement fusion technology might finally hold the key to producing an affordable deuterium engine that will permit interstellar travel. This concept essentially revolves around the idea that nuclear fusion can be initiated when a fuel target is heated and compressed. The fuel itself can be stored in a pellet or some other easily transportable shape.
Generally the compressed fuel contains a mixture of tritium and deuterium. Considering the fact that this type of fuel would be far less heavy than what would be carried by a fission-powered spacecraft, it would seem that a vehicle could carry much larger supplies of it. As a result it should be possible to actually construct a launch vehicle that could move between star systems.
Naturally this type of propulsion would still take decades if not centuries to move even a few parsecs, and as a result only unmanned probes are ever considered as interstellar payload. In the near term, however, this kind of technology could help to settle the lunar surface and perhaps even Mars. Chemical rockets can be difficult to deal with, and they’re certainly too slow for moving large numbers of personnel.
Lunar and Martian colonies will be constructed for peaceful purposes. To this end, large numbers of civilians will have to move to them. Stable vehicles that can make the trip in time frames that don’t require specialized endurance training will certainly be necessary. To this end these engines might very well enable colonization of the local systems. They could ultimately be used to provide power sources on the planetary bodies as well.
This is especially true if supplies of certain minerals are found on the Lunar and Martian surfaces after further exploration takes place. Regardless, even inertial confinement fusion technology can’t be used to fix one of the most pressing concerns that inhibit the human settlement of the Moon and Mars. Safer launch vehicles will need to be developed. The stresses that existing space capsules place on the human body make them only acceptable to specially trained individuals.
One might surmise that it should nevertheless be easy to launch payloads using chemical rockets or an orbital elevator, which will then dock with spacecraft outfitted with more powerful fusion engines. The docked vehicle could then very easily move beyond Earth orbit once it’s in a position safe enough to fully ignite the main engines.
J.A. Bonometti, & P. Jeff Morton (2012). External pulsed plasma propulsion (EPPP) analysis maturation. 36th AIAA Joint Propulsion Conference DOI: 10.2514/6.2000-3610
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