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Dennis Chamberland's
Science and Exploration
Today

 


 
 


One of the fictional plot devices often used in science fiction is called the “inertial damper”.  It’s a single switch that an author can throw and get around the nuisance of not having any gravity in a space story.  Writing a realistic plot without gravity is nearly as problematic as living in it for real.  So they just throw the inertial damping switch and the problem goes away.  Well – as a writer, I think that’s cheating!  So did Arthur C. Clarke.  And so did he and Kubrick’s in the timeless classic, 2001-A Space Odyssey where he designed the magnificent Discovery – a long distance space voyager that produced artificial gravity for real.  The movie still stands head and shoulders above any made since as the most dramatically realistic space venture ever conceived.  And as far as space ships go, the Discovery is unmatched not only in its beauty but also in its realistic functionality as well.  As a matter of fact, if the Discovery were built as Clark conceived it, it could fly to Jupiter today!

But, did you know that artificial gravity is most certainly NOT a scifi gimmick?  It is very real and it is very easy to back it up with real world physics!  In fact, the most interesting aspect of the Discovery was its artificial gravity generator that will actually work.  

But before we get into that, let us digress just two decades before the Clarke-Kubrick team filmed the Discovery on a movie set.  And so, now returning to an earlier time and a less dramatic (and expensive) set, we enter into the study of Albert Einstein. Because he had no money or way to set his experiment up and run it, he set it up and ran it in his mind.  It was a process he called the “thought experiment”.  This experiment he called the “Demonstration of the Principle of Equivalence”.  Here Einstein put a man in an elevator in deep space and sealed him up so that there was no way he could see out.  Then he placed another man in an identical sealed elevator on the surface of the earth.  Then he accelerated the elevator in space to 9.8 meters/second/second.  Then he asked each man inside each elevator car to conduct a definitive experiment to prove whether they were in space or on the surface of another planet.  Each occupant then conducted various experiments, but, alas, neither could tell whether they were merely moving in linear acceleration or sitting still inside a gravity well on the surface of a planet!  Dr. Einstein thereupon concluded there was absolutely no difference between the two – that mass in acceleration or a static mass in a gravity field were physically the same in reference to gravity – the principle of equivalence!

Now holding tightly to that thought, let us now go outside to my gorgeous 1977 Corvette.  Getting inside, we strap in, point it down the street and jam all the way down on the accelerator.  What have we here?  Well, we have a gravitational drive!  Or we have an inertial damper, or we have a gravitational generator or we have an artificial gravity machine!  According to the principle of equivalence, there is absolutely no difference.  If I strapped a g-meter to my vest, it would definitely record rising g’s as my Corvette screamed down the street.  I have created artificial gravity – or in the truest sense of Einstein’s brilliant thought experiment, I have not created artificial gravity at all – but real gravity right there in my classic car!  Indeed, there is nothing artificial about it at all – as my body presses back against the seat, as my coffee turns over and spills on my lap, as the crystal ball hanging form my mirror bends toward me, the gravity I have created is very, very real indeed and there is no experiment that could differentiate it from the earth’s gravity.

Hanging onto that thought, let us now go back to space.  All we need to do to correct weightlessness is spin our spacecraft and – presto-chango – weightlessness disappears!  And it wasn’t even magic or sloppy scifi scicobabble – it was just basic, first semester physics.  Mass in acceleration is equivalent to gravity.  Now if we match up another fascinating physical principle we can have our gravity and not have to expend constant energy.  For according to the principle of centripetial force, a rotating object is always in acceleration and the only energy we have to spend is the start up energy!  After that we can have our constant acceleration for free if nothing (like friction) acts to slow it down!  If you are not a math freak, skip the next line and go on to the next paragraph.  If you are, here’s how that works:  a=v^2/r and F=m1m2/r^2.  Awesome!

Here is how incredibly powerful that idea really is.  We have struggled for decades now to try and figure out how to solve a growing list of 10,000 engineering, biological, physiological and ergonomic problems associated with microgravity.  Instead, all we need to solve is a single engineering problem which Clark and Kubrick already solved for real – spin our spacecraft.  Now we can rid ourselves of the curse of microgravity forever.  Merely spinning a spacecraft isn’t exactly difficult science. 


However, (if you can actually believe this) there are actually opponents of artificial gravity out there hiding in the various academic and engineering bushes.  The most prevalent  argument used against employment of artificial gravity has been the added mass it will take to spin a spacecraft because a structure in constant acceleration must be stronger than a static structure.  This is true.  But in a paper published at Princeton Space Studies Institute in the 1970’s provided ample evidence that the mass penalty is only 25% - which in the long run is actually less than the mass penalty for the accumulated added mass of speculated engineering gadgets required to make up for the lack of gravity!  Others have complained about the various inductions of Coriolis force by an artificial gravity generator. (That describes secondary forces induced by rotation – which accounts for rotation of air masses on earth.)  It is true that these forces may be inconvenient – but at least they aren’t debilitating or deadly like exposure to long term microgravity.


In another study by the Case for Mars group, it was demonstrated that a manned spacecraft configuration can be spun around using a tether – certainly the poor man’s artificial gravity –but it works just fine!

But, I must end this by digressing to the wonderful and even ingenious design of the Discovery.  The Discovery is simply the most functional and beautifully designed spacecraft in human thought.  Not only is it striking to the eye, it is also astonishingly functional in that its main living structure is a spun cylinder situated inside of its bulbous forward end. If I were going to design and build a spacecraft for long term missions, it would look so much like Discovery, I would have to give the Clarke-Kubrick team due credit.  Believe me – there is simply no other way to fly in space!
 
 
 

Dennis Chamberland

 
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