As expected, the basis of any
serious discussion underlying the conjecture of
'reactionless propulsion ', must include an overview of classical
mechanics, dynamics, and possibly relativity and gravitation, to
better understand ourselves and our world. It's natural therefore
to begin with the thoughts of Galileo, Newton, Mach and other
profound thinkers since their views were, after all, central to the development of modern science and technology. The ideas and
concepts introduced by these scientists were truly revolutionary
in nature but they were also much more.
They were a catalyst or hooks, if you like, on which future generations of thinkers could hang whole paradigms of reality. They pondered the nature of things and concepts such as time, magnetism, force ,matter, mass, energy, inertia, light, gravity, etc. concepts which today are used by us all, almost as a reflex action without much further thought about the struggles which led to their universal adoption.
Today these ideas have been put to good use by engineers and scientists around the world. Technology has made life easier, at least for the people living in the industrialised nations, with the burden of heavy, repetitive and dangerous work delegated, in the most part, to machines and robots. Indeed it almost seems as if the current rate of technological advance cannot be sustained for much longer. This view has been popular among some physical scientists who remind us that, in physics at least, a paradigm shift is long overdue and that we should perhaps be looking to the coming revolution in the biotechnologies in view of the stagnation of advancement in physics. This is the easy way out.
Currently there exists a relatively small group of scientists and engineers mainly, but not exclusively, in the U.S. who are actively pursuing research towards three fundamental but all important goals. (1) studying proposed methods of propulsion that do not require the expulsion of mass. (2) looking at ways to minimise interstellar travel time, perhaps even circumventing the speed of light limit. And (3) the development of new energy delivery systems which are crucial to the first two goals. The work in the U.S. is being sponsored by NASA under the BPP or Breakthrough Propulsion Physics Program. However, the level of recent funding to the group has amounted to less than half a million dollars, ( the proverbial drop in the ocean ) which leads one to wonder just how serious these efforts are considered by the U.S. government. Other groups in Italy, France, England and elsewhere are primarily self-funded and as such are greatly limited in the scope of their work.
Current launch technology has its roots in the ancient Chinese art of fireworks. Indeed, all solid fuel launch boosters are direct descendants of the black powder rockets we are all familiar with. Our insistent use of this concept for putting payloads into orbit has, in part, led to the abovementioned stagnation in the further technological and commercial development of a space industry. This antiquated technique has been refined to a fine art and is the central reason for the astronomical launch costs of the past and the present. Nevertheless, if you speak with anyone in the field they will tell you " It's the best we can do ... there is no alternative to this sledge hammer approach...". This is only partly true. In the 60's and 70's there was talk, among industry and government pundits, of breakthroughs in force-field propulsion, of attaining 100g to 1000g accelerations, nullification of the effects of inertia, and even anti-gravity! These announcements appeared in rather conservative journals and newspapers such as 'Missiles and Rockets', 'Aviation Week', 'Interavia' (a well known aircraft technology magazine still published today), 'Popular Mechanics' , 'Aerospace Engineering', 'Nature', 'The New York Herald Tribune', and many others.
Anyone of the lines of basic research hinted at in these publications can potentially lead to useable hardware if enough funding had been available to those investigating the various proposals. Today we know little, if anything, of the outcome of those initial attempts to change the course of history. All we know for sure is that either the proposals were never followed through, due to lack of sufficient scientific credibility or adequate resources, or, alternatively, as some industry observers have intimated, such research may have been redirected under government sponsored, ( DOD, NSA, DOE etc.), efforts. Certainly there is no evidence to suggest that it was a lack or diminution of interest that has led to the historically low levels of research activity in this field.
We have arrived at a juncture. With the imminent first launches of payload, to be used in the construction of the international space station (tot. cost approx. 100 billion dollars US), about to take place, it is perhaps a good place to take a step back and to reassess our options. I am, as indeed many others, are convinced that the all important index of the scientific and technological maturity of a species is the capacity to break the gravitational bounds which have held us earthbound since the beginning. Not just for a few pioneers, but for all the inquisitive and the curious who aspire to see the globe from afar and dream of other worlds that we may visit. This measure of the facility, (or lack thereof), with which we can leave the earth (into low earth orbit) is the ratio of the cost per unit mass. Currently at around 10,000 dollars per kilogram.
After all is said and done this remains the most important problem for the 21st. century, i.e. to bring this ratio way down by at least 3 orders of magnitude. This core problem merits the full and undivided attention of all physical scientists and engineers who are both qualified and share a deep interest in the field. When this problem is solved, if indeed such a solution exists, it will surely mark the next level of development for Homo sapiens.