The Physics of Star Trek Read Online Free PDF Page B

question
     that has been raised by many trekkers over the years: How can the
    
    
     Enterprise
    
    
     bridge crew “see” objects approaching them at warp speed? Just as surely as the
    
    
     Stargazer
    
    
     overtook its own image, so too will all objects traveling at warp speed; one shouldn't be
     able to see the moving image of a warp-speed object until long after it has arrived. One
     can only assume that when Kirk, Picard, or Janeway orders up an image on the viewscreen,
     the result is an image assembled by some sort of long-range “subspace” (that is,
     super-light-speed communication) sensors. Even ignoring this apparent oversight, the Star
     Trek universe would be an interesting and a barely navigable one, full of ghost images of
     objects that long ago arrived where they were going at warp speed.
    Moving back to the sub-light-speed world: We are not through with Einstein yet. His famous
     relation between
    mass and energy,
    
    
     E=mc
    
    
     2
    
    
     ,
    
    
     which is a consequence of special relativity, presents a further challenge to space travel
     at impulse speeds. As I have described it in chapter 1, a rocket is a device that propels
     material backward in order to move forward. As you might imagine, the faster the material
     is propelled backward, the larger will be the forward impulse the rocket will receive.
     Material cannot be propelled backward any faster than the speed of light. Even propelling
     it at light speed is not so easy: the only way to get propellant moving backward at light
     speed is to make the fuel out of matter and antimatter, which (as I describe in a later
     chapter) can completely annihilate to produce pure radiation moving at the speed of light.
    However, while the warp drive aboard the
    
    
     Enterprise
    
    
     uses such fuel, the impulse drive does not. It is powered
    instead by nuclear fusionthe same nuclear reaction that powers the Sun by turning hydrogen
     into helium. In fusion reactions, about 1 percent of the available mass is converted into
     energy. With this much available energy, the helium atoms that are produced can come
     streaming out the back of the rocket at about an eighth of the speed of light. Using this
     exhaust velocity for the propellant, we then can calculate the amount of fuel the
    
    
     Enterprise
    
    
     needs in order to accelerate to, say, half the speed of light. The calculation is not
     difficult, but I will just give the answer here. It may surprise you. Each time the
    
    
     Enterprise
    
    
     accelerates to half the speed of light, it must burn 81
    
    
     TIMES ITS ENTIRE MASS
    
    
     in hydrogen fuel. Given that a Galaxy Class starship such as Picard's
    
    
     Enterprise-D
    
    
     would weigh in excess of 4 million metric tons,
    
    
     3
    
    
     this means that over 300 million metric tons of fuel would need to be used each time the
     impulse drive is used to accelerate the ship to half light speed! If one used a
     matter-antimatter propulsion system for the impulse drive, things would be a little
     better. In this case, one would have to burn merely
    
    
     twice
    
    
     the entire mass of the
    
    
     Enterprise
    
    
     in fuel for each such acceleration.
    It gets worse. The calculation I described above is correct for a single acceleration. To
     bring the ship to a stop at its destination would require the same factor of 81 times its
     mass in fuel. This means that just to go somewhere at half light speed and stop again
     would require fuel in the amount of 81x81= 6561 TIMES
    
    
     THE ENTIRE SHIP'S MASS!
    
    
     Moreover, say that one wanted to achieve the acceleration to half the speed of light in a
     few hours (we will assume, of course, that the inertial dampers are doing their job of
     shielding the crew and ship from the tremendous G-forces that would otherwise ensue). The
     power radiated as propellant by the engines would then be about 10
    
    
     22
    
    
     wattsor about a