But what about those Hubble Space Telescope images showing a full palette of Celestial Scarlets, Gaseous Greens, and Big Bang Blues? Those pictures that revolutionized the public’s perception of astronomy. Those pictures that ruined any astronomical observation that couldn’t give them a full-color “Hubble experience.” Are the Hubble Space Telescope images faked?
No. Not exactly. Not faked. But they are enhanced.
Using color as a means of embedding some form of information onto an image is a relatively old practice, dating back at least to the earliest colored maps of Earth or fathom charts of the ocean. Since every element has a characteristic glow when ionized—ionized oxygen atoms glow emerald green, ionized helium glows yellow, ionized calcium glows dark violet—Hubble scientists use actual data and actual colors to present images that the human eye cannot see on its own.
Human eyes are practically blind to colors at very low light levels. The next time you see a bunch of amateur astronomers setting up camp, ask one of them to show you the Eagle Nebula (seen most easily in Northern Hemisphere spring). Because your eyes won’t be able to see colors, even with the darkest skies and the largest amateur telescope, you’ll be lucky to see something like a gray splotch of light, in the vague outline of an eagle in flight.
If you take a long-duration color photograph of the Eagle Nebula, either on film or electronically, the long exposure will help you to artificially collect more light and make the image brighter. Your resulting image might show something like a pink splotch of light, in the vague outline of an eagle in flight.
Then, of course, there’s the iconic HST image of the Eagle Nebula, the one known as the “Pillars of Creation.” The colors are not fake. Parts of the nebula with more ionized oxygen are colored green, as they “should” be. Other ionized gases are colored in their appropriate hues. By this method, HST scientists can subtract the “background noise” of the red hydrogen glow, and focus on the parts of the image that really show something interesting.
Before you start yelling that this is fraud, remember that any image you see through a telescope, like anything you see in a microscope or a spectroscope, anything from your child’s ultrasound to your father’s MRI, are all images that cannot be seen with the unaided naked eye. When your doctor adjusts the contrast on your ultrasound to show the outline of the fetus in more detail or more clearly, is the resulting image a fraud? Of course not. Hubble images use a similar technique to differentiate different types of material in a star cloud using intense versions of the real color that that particular material emits.
So what were Apollo and Starbuck flying through, and would it really look like that?
A nebula is essentially just a cloud of gas and cosmic dust in space. Sometimes, as in the (fictional) Ionian Nebula, the gas and dust were violently ejected by a dying star. In other nebulae, as we saw in chapter 16, the gas and dust are in the process of gathering together to create a new star, with some scraps of leftover dust gathering together under their own gravity to became the planets. Sometimes a nebula is both. As Carl Sagan and Moby made very clear, we are all made of the same material as the stars.
When the gas given off by a supernova collides with other gas within the star’s planetary system (or even interstellar gas), the shock heats the gas to nearly 10,000,000 degrees, causing the nebula to glow. Red. Vivid red. Rose red. The 656.281-nanometer red of hydrogen alpha. Sure, there might be some other colors, but the predominant color would be red. So why were Starbuck and Apollo flying through pastel-colored veils of gas?
The simple answer is because they’re on a TV show and that’s what we were expecting. Had Starbuck and Apollo been flying through ghostly gray clouds of gas (as it most likely would have seemed to their naked eyes), or through uniformly red clouds of gas (as is more “accurate”), our attention would have been unnecessarily drawn away from their conversation, or the wonder of Starbuck’s return. Instead, millions of viewers would have been wondering, “Why are the clouds only gray (or red)?” Thanks to the Hubble, everyone “knows” that interstellar clouds come in more colors than a box of 64 crayons, and, like a newbie at a telescope, we would have been jarred if the visuals had not matched our expectations.
This is where Moore’s Law is at its finest. The point of Battlestar Galactica is to tell a story, not to present a scientific documentary. If it works better, in terms of interest and excitement, to have Starbuck emerge from the colorful clouds of a giant nebula in space, that’s what they going to do. It’s time to evoke the First Law of The Science of Battlestar Galactica: “It’s just a show, I should really just relax.”
CHAPTER 20
Water
Think back to the second episode of the first season. Commander Adama had spent the previous few minutes explaining to President Roslin that Galactica’s water recycling system is close to 100 percent efficient. He adds that since about one-third of the other ships in the Fleet were not built for long-term voyages, Galactica has to supply water-recycling services for them. As the president watches, Galactica begins the process of swapping dirty water for clean water with the Virgon Express. Then it happens. There’s a dull explosion that causes the ship to rock. The lights start to flash in the CIC, and Lieutenant Gaeta yells, “Decompression alarm!” An outside view shows geysers of water erupting from holes in Galactica’s hull, boiling away to ice in the vacuum of space.
Later, at a briefing for Roslin and Adama, Gaeta reports that they’ve lost about 10 million “JPs” of water, about 60 percent of the ship’s holdings. Baltar reports that the Fleet’s population of 45,265 needs about 2.5 million “JPs” of water per week. As for replenishing that supply, Colonel Tigh reports that there are five planetary systems within the Fleet’s practical jump radius, but he doesn’t hold out much hope: “Most planets are just hunks of rock or balls of gas. The Galaxy’s a pretty barren and desolate place when you get right down to it.” (Remember the Second Law of the Science of Battlestar Galactica? “Space is mostly empty. That’s why it’s called ‘space.’”) And it soon looks as if the Colonial civilization will not end with the bang of Cylon nukes going off, but with the whimpering croak of a parched throat.
There’s a lot going on in the first few minutes of this episode. First, what is “JP”? If we assume that Baltar is telling the truth,cl each Colonial needs about (2,500,000/45,265) = 55.23 JPs of water per week. If we assume that a Colonial week is the same as ours, that works out to 7.89 JPs of water a day; call it 8 JPs. NASA reports that astronauts on the International Space Station [ISS] are using about 12 liters of water per day. If we assume that an on-the-run civilian Fleet will use water as carefully as our astronauts, then 8 JPs is equivalent to 12 liters, and therefore each JP is about 1.5 liters. If that is the case, then Galactica holds nearly 16,666,667 JPs, or 25,000,000 liters of water, the equivalent of 10 Olympic-sized swimming pools. To refill 60 percent of that would require a ball of water 30 meters in diameter—the equivalent of about 7.5 million two-liter soda bottles.
Although Colonel Tigh was right about the composition of most planets, his statement was also misleading. There is more water in space than most people imagine, even if that water may be all but impossible to extract or utilize.
Water is actually one of the more abundant compounds in space—it’s not everywhere, but not rare, either. In March 1969, when Dr. A. G. W. Cameron of Yeshiva University reported in the journal Science the presence of microwave emissions from excited water vapor in space, the nascent field of astrobiology probably gained its strongest foothold to respectability. Before that time, mainstream scientists thought outer space was dry—and why would anyone look for life in a waterless environment?
Brendan “Hot Dog” Costanza.
Felix Gaeta.
This argument shows how chauvinistic we are toward water. Water is so closely associated with life here on Earth that for centuries we naturally assumed that life couldn’t exist without it. Finding water in molecular clouds in deep space meant that life stood a
chance of being nearly anywhere in the universe. Although it is theoretically possible for alien life forms to use fluids other than water, none of those fluids match the utility and ubiquity of H2O itself.
Why? What’s so special about water?
We’ve already defined life as a self-sustaining chemical system. Such a system needs a medium in which to sustain itself. It helps if that medium is a liquid, since liquids can easily transport substances like food and wastes. It helps if the medium remains liquid over a fairly large temperature range.1 It also helps if that medium can dissolve a great many different chemicals, so that a living organism can make the greatest possible use of its available resources. For life on Earth, water meets all these requirements. Of course, it’s a bit of a chicken-and-egg cycle: we happened to evolve in a star system in which water was abundant, so naturally we use water as our liquid medium.
It was exactly the galactic ubiquity of water that fueled one of the greatest complaints about this episode on BSG Internet fan boards: “Why didn’t they just find a comet? They’d be done with all their water problems for the foreseeable future!” That may be true in theory, but in reality, our understanding of comets has come a long way since the American astronomer Fred Whipple called them “dirty snowballs.”
Although there may be trillions of comets in the outer reaches of a planetary system, they are spaced widely and difficult to find and usually keep their water well hidden. The space probe Deep Space 1, in its 2001 encounter with Comet Borrelly, found nothing but a hot and dry surface without any obvious traces of ice. Deep Impact, a ballistic probe that smashed into Comet Tempel 1 in 2005, found the same thing on the outside—dry dust—with water existing only deep inside the comet. This dusty coating means that comets are dark objects when seen against a black backdrop of space. They’re difficult to spot.
Further, if Galactica could somehow snare a comet, mining that water would require drilling. Galactica probably has access to drilling equipment,2 but why go through all the trouble if you don’t have to? When you’re looking for easy water, comets might not be the way to go.
Well, then, where else can we look for water in a planetary system? When we look at the major bodies of our solar system, we find that Mercury,cm Earth, Luna,cn Mars,co Phobos,cp Deimos,cq Ceres,cr Jupiter,cs Europa,ct Ganymede,cu Callisto,cv Saturn,cw Saturn’s rings,cx Enceladus,cy Tethys,cz Dione,da Rhea,db Uranus,dc Neptune,dd and Tritonde all have water, water vapor, or water ice in quantities that would allow everyone in the entire Colonial Fleet to take giant Japanese group baths in tyllium-powered hot tubs.
The water is usually on the surface in the form of ice, and therefore is relatively easy to access. If our solar system turns out to be average, then the Colonial Fleet should have no problem finding water in just about any other planetary system, on the surface of some icy moon.
Which is exactly where they find it.
PART FOUR
BATTLESTAR TECH
CHAPTER 21
The Rocket’s Blue Glare: Sublight Propulsion
It most likely happened when some unknown-to-history Chinese philosopher improperly filled a bamboo tube with sulfur, charcoal, and dried pig urine crystals. Previous philosophers had found that this mixture of materials burned fiercely. When confined in a tube or jar, it exploded. Our unknown philosopher was probably doing just that—building a firecracker to make a huge bang in the hopes of scaring away evil spirits before a feast or other ceremony. It’s not hard to imagine that that day, somewhere in the Celestial Kingdom, the bamboo tube caught fire on only one end. Instead of exploding, the burning material released rapidly expanding hot gases that sent the tube zooming in the other direction. The first rocket was born.
In a land beset by near-perpetual warfare, the idea of a self-propelled burning projectile must have seemed like the ultimate wonder weapon. The first rocket attack in recorded history took place in the year 1232 CE when Chinese defenders repelled Mongol raiders at the battle of Kai-Feng-Fu. The Mongols were fast learners. Nine years later, when the Mongols were invading Europe, they used rockets of their own in the siege of Budapest. In 1258, the Arab world was introduced to rockets when the Mongols attacked Baghdad. The Arabs quickly added the rocket to their arsenal, and used them against King Louis IX’s French army during the Seventh Crusade in 1268.
In 1650, the first European book on artillery was printed, and nearly 150 years later the Sultan of Mysore in India used iron rockets against the British East India Company troops. The British military engineer William Congreve reverse-engineered these rockets and made them part of the British arsenal by 1803. And the Congreve rocket had something new—a long stick coming out of the end to provide some measure of stability in flight. df Without the stabilization that the stick provided, a rocket was apt to land literally anywhere, even on one’s own territory. By 1812, the British were so enamored of this weapon that the ferocity of their missile attack on Fort McHenry in Baltimore harbor led Francis Scott Key to write a poem expressing his pride at how the flag of the United States stood up to the rockets’ red glare.
Until the twentieth century, rockets used solid propellant, usually a form of black powder or gunpowder. Solid propellants are the simplest form of rocketry, and they offer great reliability with very little velocity control. Solid rockets can’t easily be throttled in real time the way a jet engine can: they either go, they don’t go, or they explode.
But a solid rocket can’t burn just any fuel. Ideally, the fuel must also carry its own form of oxygen. Gunpowder, a mixture of sulfur, charcoal, and potassium nitrate, gets its oxygen from the nitrate. The space shuttles’ Solid Rocket Boosters (SRBs) use aluminum and butadiene as their fuel and ammonium perchlorate as their oxygen source, a combination called ammonium perchlorate composite propellant, or APCP. As the fuel burns, the oxygen is chemically released from its source material. This feeds oxygen to the burning fuel, which helps the fuel to burn better, which releases more oxygen, which burns more fuel, and so on. While substances like wood or coal burn very well, they don’t have their own oxygen sources, and without that you’re not going to find wood- or coal-powered spaceships outside of mad steampunk fiction.
Kara "Starbuck" Thrace.
Starbuck and President Laura Roslin.
Even though gunpowder works as a better rocket fuel than coal, it certainly isn’t the best fuel. It was this quest for more energetic fuels that led to the second great development of rocket power: the liquid-fueled rocket in the early twentieth century. The development of liquid rockets coincided more or less with the availability of refined petroleum, since almost any liquefied petroleum product gives a greater yield of kilocalories per gram when burned compared to gunpowder. Because of this, liquid-fueled rockets were developed nearly simultaneously in Germany, the Soviet Union, and the United States by scientist-engineers who for the most part were unaware of one another’s technical work.
As with any spacecraft, Galactica is dependent upon a source of fuel, and one basic fact of rockets has always remained constant—they use expanding gases escaping in one direction to provide thrust in the other direction in a direct application of Newton’s Third Law. If you shoot a gun, you experience an excellent example of this law: the bullet or shot propelled from the barrel causes the gun to recoil. It kicks in the opposite direction. Were you standing on a skateboard when you fired the gun, you would roll in the opposite direction—the gun would provide thrust. In the case of a spacecraft, replace “shot from a gun barrel” with “hot gasses from a nozzle,” and you have the basic concept of a rocket.
Two metrics can be used to gauge the performance of a propulsion system: thrust and specific impulse. Thrust is an instantaneous measurement of how much force is being generated by the propulsion method. More thrust means higher acceleration. High thrust is necessary, among other things, to propel a spacecraft off a planet and into space. Scientists and engineers also measure the sum total amount of rocket propulsion available in a given amount of mass of a fuel
source, its efficiency, by using a value known as specific impulse (SI or Isp). Note that there is no time dependence implied in the definition of SI. SI is the measure of the maximum total change in momentum that a propulsion system, or propellant, will yield per kilogram of fuel. This can occur over a very short or very long period of time.
With that understanding, let’s take a look at some of the various propellants Galactica and her Vipers could potentially use, keeping in mind their missions. If Galactica is the Colonial equivalent of an aircraft carrier, then it likely has to get on station in a relative hurry. We know from the Miniseries that her FTL engines have not been used in over 20 years, so that implies that Galactica’s sublight engines allow her to get up to a reasonably high speed—enough to traverse the interplanetary distances within the Twelve Colonies in a reasonable amount of time. This would argue in favor of a propulsion system that can generate a high thrust. Vipers, on the other hand, have to intercept inbound threats in a hurry, another argument for high thrust (assuming Vipers and Galactica use the same kind of fuel). In both cases, the ability to stay on station for a long period is a benefit, which means that the propulsion system should be one with a high efficiency, or high SI, as well.
In the table on page 202 we compare the specific impulse and thrust of one type of solid propellant with several liquid propellants. Thrust in particular can be affected by many factors beyond the chemical properties of the propellant (including flow rates and the geometry of the rocket nozzle and combustion chamber), so the thrust values given should be viewed as an “all things being equal” comparison.
Galactica’s sub-light propulsion system.
The Science of Battlestar Galactica Page 16