The Physics of Star Trek (12 page)

We find that there is roughly one proton in the universe today for every 10 billion
photons in the cosmic background radiation. This means that the original excess of protons
over antiprotons was only about
1 part in 10 billion!
That is, for every 10 billion antiprotons in the early universe, there were 10 billion and
1 protons! Even this minuscule excess (accompanied by a similar excess in neutrons and
electrons over their antiparticles) would have been sufficient to have produced all the
observed matter in the universethe stars, galaxies, planetsand all that we have come to
know and love.

That is how we think the universe got to be made of matter and not antimatter. Aside from
its intrinsic interest, the moral of this story for Star Trek is that if you want to make
a matter-antimatter drive, you cannot harvest the antimatter out in space, because there
isn't very much. You will probably have to make it.

To find out how to do this, we return to the buffalo roaming on the Midwestern plain above
the Fermilab accelerator. When thinking about the logistics of this problem, I decided to
contact the director of Fermilab, John Peoples, Jr., who led the effort to design and
build its Antiproton Source, and ask if he could help me determine how many antiprotons
one could produce and store per dollar in today's dollars. He graciously agreed to help by
having several of his staff provide me with the necessary information to make reasonable
estimates.

Fermilab produces antiprotons in medium-energy collisions of protons with a lithium
target. Every now and then these collisions will produce an antiproton, which is then
directed into the storage ring beneath the buffalo. When operating at average efficiency,
Fermilab can produce about 50 billion antiprotons an hour in this way. Assuming that the
Antiproton Source is operating about 75 percent of the time throughout the year, this is
about 6000 hours of operation per year, so Fermilab produces about 300,000 billion
antiprotons in an average year.

The cost of those components of the Fermilab accelerator that relate directly to producing
antiprotons is about $500 million, in 1995 dollars. Amortizing this over an assumed useful
lifetime of 25 years gives $20 million per year. The operating cost for personnel
(engineers, scientists, staff) and machinery is about $8 million a year. Next, there is
the cost of the tremendous amount of electricity necessary to produce the particle beams
and to store the antiprotons. At current Illinois rates, this costs about $5 million a
year. Finally, related administrative costs are about $15 million a year. The total comes
to some $48 million a year to produce the 300,000 billion

antiprotons that Fermilab annually uses to explore the fundamental structure of matter in
the universe. This works out to about 6 million antiprotons for a dollar!

Now, this cost is probably higher than it would need to be. Fermilab produces a
high-energy beam of antiprotons, and if we required only the antiprotons and not such high
energies we might cut the cost, perhaps by a factor of about 2 to 4. So, to be generous,
let's assume that using today's technology, one might be able to get from 10 million to 20
million antiprotons for a buck, wholesale.

The next question is almost too obvious: How much bang for this buck? If we convert
entirely the mass of one dollar's worth of antiprotons into energy, we would release
approximately 1/1000 of a joule, which is the amount of energy required to heat up about
1/4 of a gram of water by about 1/1000 of a degree Celsius. This is nothing to write home
about.

Perhaps a better way to picture the potential capabilities of the Fermilab Antiproton
Source as the nucleus of a warp core is to consider the energy that might be generated by
utilizing every antiproton produced by the Source in real time. The Antiproton Source can
produce 50 billion antiprotons an hour. If all these antiprotons were converted into
energy, this would result in a power generation of about 1/1000 of a watt! Put another
way, you would need about 100,000 Fermilab Antiproton Sources to power a single lightbulb!
Given the total annual cost of $48 million to run the Antiproton Source, it would cost at
the present time more than the annual budget of the U.S. government to light up your
living room in this way.

The central problem is that as things stand today it requires far more energy to produce
an antiproton than you would get out by converting its rest mass back into energy. The
energy lost during the production process is probably at least a million times more than
the energy stored in the antiproton mass. Some much more effective means would be needed
for antimatter production before we could ever think of using matter-antimatter drives to
propel us to the stars.

It is also clear that if the
Enterprise
were to make its own antimatter, vast new technologies of scale would be needednot just
for cost reduction, but for space reduction. If accelerator techniques were to be
utilized, machines that generate far more energy per meter than those of today would be
necessary. I might add that this is currently a subject of intense research here on
late-twentieth-century Earth. If particle accelerators, which are our only tools for
directly exploring the fundamental structure of matter, are not to become too costly for
even international consortiums to build, new technologies for accelerating elementary
particles must be developed. (We have already seen that our own government has decided
that it is too expensive to build a next-generation accelerator in this country, so a
European group will be building one in Geneva, designed to come on line at the beginning
of the next century.) Past trends in the efficiency of energy generation per meter of
accelerator suggest that a tenfold improvement may be possible every decade or two. So
perhaps in several centuries it will not be unreasonable to imagine a starship-size,
antimatter-producing accelerator. Given the current reluctance of governments to support
expensive fundamental research at this scale, one might not be so optimistic, but in two
centuries a lot of political changes can occur.

Even if one were to make antimatter on board ship, however, one would still have to deal
with the fact that to produce each antiproton would invariably use up much more energy
than one would get out afterward. Why would one want to expend this energy on antimatter
production, when one might turn it directly into propulsion?

The Star Trek writers, always on the ball, considered this problem. Their answer was
simple. While energy available in other forms could be used for impulse propulsion and
hence sublight speeds,
only
matter-antimatter reactions could be used to power the warp drive. And because warp drive
could remove a ship from danger much more effectively than impulse drive, the extra energy
expended to produce antimatter might be well worth it in a pinch. The writers also
sidestepped the accelerator-based antimatter-production problems by inventing a new method
of antimatter production. They proposed hypothetical “quantum charge reversal devices,”
which would simply flip the charge of elementary particles, so that one could start with
protons and neutrons and end up with antiprotons and antineutrons. According to the
Next Generation Technical Manual,
while this process is incredibly power-intensive, there is a net energy loss of only 24
percentorders of magnitude less than the losses described above for accelerator use.

While all this is very attractive, unfortunately simply flipping the electric charge of a
proton is not enough.

Consider, for example, that both neutrons and antineutrons are neutral. Antiparticles have
all the opposite “quantum numbers” (labels describing their properties) of their matter
partners. Since the quarks that make up protons possess many labels other than electric
charge, one would have to have many other “quantum reversal devices” to complete the
transition from matter to antimatter.

In any case, we are told in the technical manual that, except for emergency antimatter
production aboard starships, all Starfleet antimatter is produced at Starfleet fueling
facilities. Here antiprotons and antineutrons are combined to form the nuclei of
anti-heavy hydrogen. What is particularly amusing is that the Starfleet engineers then add
antielectrons (positrons) to these electrically charged nuclei to make neutral
anti-heavy-hydrogen atomsprobably because neutral antiatoms sound easier to handle than
electrically charged anti-nuclei to the Star Trek writers. (In fact no antiatoms have yet
been created in the laboratoryalthough recent reports out of Harvard suggest that we are
on the threshold of producing an antihydrogen atom in this decade.) Unfortunately, this
raises severe containment problems, since magnetic fields, which are absolutely essential
for handling substantial amounts of antimatter without catastrophe, work
only
for electrically charged objects! Ah well, back to the drawing board. .. .

The total antimatter fuel capacity of a starship is approximately 3000 cubic meters,
stored in various storage pods (on Deck 42 in the
Enterprise-D).
This is claimed to be sufficient for a 3-year mission. Just for fun, let's estimate how
much energy one could get out of this much antimatter if it were stored as
anti-heavy-hydrogen nuclei. I will assume that the nuclei are transported as a rarefied
plasma, which would probably be easier to contain magnetically than a liquid or solid. In
this case, 3000 cubic meters could correspond to about 5 million grams of material. If 1
gram per second were consumed in annihilation reactions, this would produce a power
equivalent to the total power expended on a daily basis by the human race at the present
time. As I indicated earlier in discussing warp drive, one must be prepared to produce at
least this much power aboard a starship. One could continue using the fuel at this rate
for 5 million seconds, or about 2 months. Assuming that a starship utilizes the
matter-antimatter drive for 5 percent of the time during its missions, one might then get
the required 3 years' running time out of this amount of material. Also of some relevance
to the amount of antimatter required for energy production is another fact (one that the
Star Trek writers have chosen to forget from time to time): matter- antimatter
annihilation is an all-or-nothing proposition. It is not continuously tunable. As you
change the ratio of matter to antimatter in the warp drive, you will not change the
absolute power-generation rate. The relative power versus fuel used will decrease only if
some fuel is wastedthat is, if some particles of matter fail to find antimatter to
annihilate with, or if they merely collide without annihilating. In a number of episodes
(“The Naked Time,” “Galaxy's Child,” “Skin of Evil”) the matter-antimatter ratio is
varied, and in the Star Trek technical manual this ratio is said to vary continuously from
25:1 to 1:1 as a function of warp speed, with the 1:1 ratio being used at warp 8 or
higher. For speeds higher than warp 8, the amount of reactants is increased, with the
ratio remaining unchanged. Changing the amount of reactants and not the ratio should be
the proper procedure throughout, as even Starfleet cadets should know. Wesley Crusher made
this clear when he pointed out, in the episode “Coming of Age,” that the Starfleet exam
question on matter-antimatter ratios was a trick question and that there was only one
possible rationamely, 1:1.

Finally, the Star Trek writers added one more crucial component to the matter-antimatter
drive. I refer to the famous dilithium crystals (coincidentally invented by the Star Trek
writers long before the Fer-milab engineers decided upon a lithium target in their
Antiproton Source). It would be unthinkable not to mention them, since they are a
centerpiece of the warp drive and as such figure prominently in the economics of the
Federation and in various plot developments. (For example, without the economic importance
of dilithium, the
Enterprise
would never have been sent to the Halkan system to secure its mining rights, and we would
never have been treated to the “mirror universe,” in which the Federation is an evil
empire!)

What do these remarkable figments of the Star Trek writers' imaginations do? These
crystals (known also by their longer formula
26
dilithium 21 diallosilicate 1:9:1 heptoferranide) can regulate the matter-antimatter
annihilation rate, because they are claimed to be the only form of matter known which is
“porous” to antimatter.

I liberally interpret this as follows: Crystals are atoms regularly arrayed in a lattice;
I assume therefore that the antihydrogen atoms are threaded through the lattices of the
dilithium crystals and therefore remain a fixed distance both from atoms of normal matter
and one another. In this way, dilithium could regulate the antimatter density, and thus
the matter-antimatter reaction rate.

The reason I am bothering to invent this hypothetical explanation of the utility of a
hypothetical material is that

once again, I claim, the Star Trek writers were ahead of their time. A similar argument,
at least in spirit, was proposed many years after Star Trek introduced dilithium-mediated
matter-antimatter annihilation, in order to justify an equally exotic process: cold
fusion. During the cold-fusion heyday, which lasted about 6 months, it was claimed that by
putting various elements together chemically one could somehow induce the nuclei of the
atoms to react much more quickly than they might otherwise and thus produce the same
fusion reactions at room temperature that the Sun requires great densities and
temperatures in excess of a million degrees to generate.

One of the many implausibilities of the cold-fusion arguments which made physicists
suspicious is that chemical reactions and atomic binding take place on scales of the order
of the atomic size, which is a factor of 10,000 larger than the size of the nuclei of
atoms. It is difficult to believe that reactions taking place on scales so much larger
than nuclear dimensions could affect nuclear reaction rates. Nevertheless, until it was
realized that the announced results were irreproducible by other groups, a great many
people spent a great deal of time trying to figure out how such a miracle might be
possible.