INTERSTELLAR - A Series of Science Fiction Adventure Stories - 2 - Cascade

Interstellar Series

---

Boats can push water through their propellers. Airplanes can push air through their propellers or turbines. Rockets, on the other hand, have none of these options. Every ounce of thrust their engines produce has to come through the expenditure of onboard propellant — in other words, they accelerate forward by throwing material backward. Boats and airplanes also accelerate forward by throwing material backward, but they get this material from the environment around them. Rockets have to carry all this "reaction mass" on board. This severely limits the efficiency of a rocket engine when compared with a fluid-breathing or surface-friction engine, even moreso than the need to carry their own oxygen to combust with their fuel.

Even worse, it means that at the start of your flight, you have to produce that much more thrust just to push all your unburned fuel along with you, so each kilogram of fuel you add provides progressively less and less total acceleration. This cascade effect can add up very quickly.

The equation for how much total acceleration your rocket can undergo before it runs out of fuel — the total "delta-v budget" of your rocket — was derived by Tsielkovsky over a century ago:. The v e for, say, the Space Shuttle's main engines is about meters per second. The shuttle's weight with fuel must be over seven times as high as its weight without fuel! Discarding its spent solid rocket boosters in mid-flight a trick similar to staging can help a little, but not much. With such a stultifying mass ratio just to get into Earth orbit, you can see why flying to other planets in a matter of days — or worse, flying to another star within a human lifetime — just isn't practical for modern chemically-propelled rockets.

How impractical is it? Well, let's take the example of the trip to Saturn discussed above, where our space cadets undergo a continuous 1 g acceleration to the half way point, and a continuous 1 g deceleration for the rest of the trip. In other words, your space ship must carry 3. To put that into perspective, the estimated mass of the entire observable universe excluding exotic forms of mass such as dark matter is only some 10 53 kilograms. A space ship with a very modest kg empty mass would have to carry 3 x 10 observable universes' worth of fuel.

Most hard SF authors will solve this problem by using more exotic forms of rocket propulsion which have much much higher exhaust velocities, or which can derive their propellant from someplace other than the rocket's fuel tanks. Nuclear fission NERVA engines Ion engines, such as those on the Dawn and Deep Space One spacecraft The Orion Drive Controlled nuclear fusion engines Ground-based laser pushers Ramscoops With the exception of ion engines, all of these are mere drawing-board designs at present, and all of them have practical problems.

NERVA engines don't have that much better an exhaust velocity than chemical engines, and require shielding to protect the crew and the ship's more delicate electronics from their radioactivity. Orion's nuclear putt-putt motor requires an enormous pusher plate that dramatically increases the dead weight the spacecraft has to carry.

Controlled nuclear fusion has never been accomplished, at least not in a way that produces more energy than it consumes. Ramscoops rely not only on the controlled nuclear fusion of light hydrogen which is even trickier than the controlled nuclear fusion of heavy hydrogen , but also on the ability to collect the extremely rarefied interstellar gas without inducing significant drag, which might not even be possible.

But even if controlled nuclear fusion does become a reality allowing what Robert A.

Heinlein called a torch , that still won't eliminate the need for big rockets if you want to get anywhere in a reasonable amount of time. So the space ship's fuelled weight will need to be 3. This means it's still going to have to carry 2. You're still stuck with a big rocket. And when you get to Saturn, you'll be out of fuel. You'll need to completely refill your fuel tanks if you want to make the return trip to Earth. Forget about the notion of a "ship" patrolling the "seas of interplanetary space" for months on end, hopping from planet to planet without refuelling.

We humans evolved on, and so far all grew up on, Earth. We instinctively expect the air to be breatheable, the temperature to be liveable, the gravity to be 9. The sad fact is, though, that no other planet we've detected thus far is even remotely habitable by human standards. The bigger ones are Jupiter-like balls of gas, while the smaller ones are almost universally airless. The few worlds we've found that do have both an atmosphere and a solid surface have been blanketed in gases that no human can breathe, at pressures anywhere from near-vacuum to 90 times Earth's sea level.

While it's theoretically possible that a planet out there might harbor life as we know it, it would have to fit a long, narrow list of parameters, and even then, the kind of life that might have actually evolved there will most likely be very different from the multicellular-eukaryote-rich biome inhabiting Mother Terra. In order for a planet to be able to support life as we know it on its surface at all , it will have to lie in a very narrow range of distances from its parent star.

Adrian Holland

Too close, and any water would evaporate. Too far, and any water would freeze.

Chapter 17: Airlock Restored

Liquid water — and life as we know it requires liquid water — can only exist if the planet lies within that narrow zone where it's receiving just the right amount of energy from its star for the surface temperature to allow it. This is called the star's "comfort zone," or " Goldilocks Zone " as in: All we can say for sure is that, for a star as bright and hot as the sun, Venus is too close, Earth is clearly within the Goldilocks zone, and Mars is probably close to the tail end of it.

How far away from the star the Goldilocks zone is depends on the star's energy output. A very dim red dwarf star, like Wolf , would require a planet to be only about 1. A bright and powerful star like Sirius A, on the other hand, would require a planet to be 5 A. Interestingly, both of those distances have potentially disastrous consequences.

If a planet is only 0. The strength of tidal forces varies directly with the larger object's i. The tidal forces on a planet only 0. This all but guarantees that the planet will be locked in synchronous rotation with its star — that is, its rotational period must match its orbital period, so the same side is always facing the star. One side of such a planet would be in perpetual daylight, while the other would be in perpetual night. The climate on such a world would be much different than the climate on Earth. Dim stars also have the disadvantage that their Goldilocks Zones are going to be narrower.

There is disagreement as to exactly how wide the Goldilocks Zone around the sun is — different models compute widths anywhere from 0. The narrower the Goldilocks Zone, the less a chance that a planet would happen to have formed within it. Worse, many red dwarf stars — Wolf included — are flare stars , which emit semi-regular bursts of X-rays every bit as powerful as those emitted from a flare taking place on the sun.

And X-rays can scatter e. Regular flare outbursts so close by probably means that any life would have to be buried underground.

A planet orbiting Sirius A at 5 A. Sirius is a binary system.

Sirius B a white dwarf makes one complete orbit around Sirius A every half century, and at one point in this orbit the two stars come within 8 A. As any budding astrophysicist will tell you, the three-body problem is a chaotic one for which there is no solution. The farthest a stable planetary orbit can be from Sirius A is, therefore, only 2 A. Therefore, no planet can exist in the habitable, liquid water zone around Sirius A. A planet could theoretically orbit both Sirius A and Sirius B as a pair, but then its minimum orbital distance has to be at least four times the greatest separation distance between the two stars in their orbit of each other.

Sirius B's orbit is rather eccentric, and at one point in its orbit it's over 30 A. A planet orbiting both Sirius A and B would therefore need to be at least A. Even if a planet happens to lie within the Goldilocks Zone, that's no guarantee that it can harbor surface life — let alone that life will actually arise there on its own, or that said life will have had sufficient time to evolve to the point where space-faring beings can emerge.

The atmospheric pressure must be high enough for liquid water to exist, and that can't happen unless the planet has sufficiently strong surface gravity to keep its atmosphere from escaping into space. The formula for determining the surface gravity of a planet is as follows:. The result will be in meters per second squared. Plugging those into the formula above, we get:. One factor that contibutes to Mars's thin atmosphere is this low surface gravity. Without a magnetic field to protect it, the solar wind will very slowly strip away the lighter particles of an inner planet's atmosphere.

Mars may have had a reasonably thick nitrogen atmosphere like Earth a few billion years ago. Note, though, that what qualifies as a "lighter particle" subject to solar wind erosion also depends on the planet's surface gravity.

Despite being farther from the sun than the Earth, and thus receiving less heat that could potentially boil its atmosphere away into space, Mars still has less of an atmosphere than the Earth does. A resonably strong surface gravity may be required for a planet to retain a thick atmosphere.

There are exceptions in our own solar system, of course: But you need at least some gravity, and possibly quite a lot of gravity, to retain an atmosphere within the Goldilocks Zone. Another factor that can mean no life-bearing planets are possible in a given star system is the lack of heavy elements. The Milky Way galaxy is over ten billion years old.

When it first formed, it consisted almost entirely of hydrogen and helium; almost no heavier elements like carbon and the other elements necessary for organic life existed. Several generations of stars have been born and died since then, and some of the more spectacular star deaths have peppered the interstellar medium with heavy elements synthesized by those stars' death throes. The sun, for instance, is a third-generation star — the cloud of gas and dust out of which it formed contained material expelled by a supernova which, in turn, had formed out of an earlier cloud that contained material from an even earlier supernova.

This is why there was enough carbon, oxygen, silicon, iron, etc. Astrophysicists refer to all elements heavier than helium as "metals" even if the element in question is oxygen or neon , and sometimes call a star system's heavy element abundance its "metallicity. By contrast, Barnard's Star a red dwarf approximately 6 light-years from the sun formed in the Milky Way's first wave of star formation. It has almost no heavy elements. If the star itself is metal-poor, that means the cloud out of which it formed was also metal-poor, and therefore any planets that would have formed out of that cloud would be metal-poor as well.

There might be some Jupiter-like balls of hydrogen or helium orbiting Barnard's Star, but there isn't going to be anything with a solid surface. So, to sum up, the requirements for a habitable Earth-like planet are: The planet must lie within the Goldilocks Zone for its star. The star cannot be too dim, since this will mean its Goldilocks Zone will be too narrow, any planet in the zone will be in synchronous rotation with the star, and the Goldilocks Zone will lie within the Danger Zone for stellar flares.

If a binary star system, the companion star cannot come closer to the primary than 4 times the Goldilocks Zone distance. The star system cannot be metal-poor, or if its metallicity isn't known so old that it would have formed when the galactic medium was still metal-poor. The planet cannot be too small or light, as this will prevent it from retaining an atmosphere. Note that if you're willing to accept non Earth-like planets, many more possibilities open up. For example, Europa, one of Jupiter's moons, is thought to contain liquid water despite being nowhere near the Goldilocks zone. A thick or rapidly rotating atmosphere like Venus's can distribute heat evenly around the planet, thus solving the problem with tidal locking mentioned above.

Similar authors to follow

However, these all lead to new problems and obviously won't resemble Earth. For that matter, even liquid water might not be necessary. There are theories that life might be possible with alternate biochemistries based on liquid ammonia, methane, or even interstellar gases. Since all we have to go on is observations of Earth, there's no way to tell for sure if this is actually possible.

But the less Earthlike you get, the more problems you have with an actual story involving anything other than Starfish Aliens. A hypothetical ammonia based organism, for instance, would constantly argue over the thermostat with Earthlings given that ammonia boils at F. If you want anything more interesting than bacteria to have evolved, another problem arises.

The star must have been shining at roughly the same energy output for at least a couple billion years, in order to give time for complex life to have evolved. This last requirement is a real buzzkill, as it eliminates damn near every bright star you can see in Earth's night sky. Big, bright stars like Sirius A only live for a few hundred million years before they run out of gas. The candle that burns twice as bright lasts half as long , after all. However to have the best run for your money you must use a low-mass star, and the Universe is still too young to have seen those stars going red giant.

See the Useful Notes article on Local Stars if you want to pick a home for your theoretical planet from among our stellar neighbors. See the Useful Notes article on Planets if you want to put even more realism into the worlds you create. Two separate "So You Want To" articles now exist to deal with the realism aspects of creating your own aliens. Of particular import to any story involving space travel is the "Believable space-faring aliens" section of the first article.

Mar 19, Adrian Holland rated a book it was amazing. Jan 29, Cascade by Adrian Holland Goodreads Author. Quotes by Adrian Holland. Also great for classic film fans! Search for a book to add a reference. We take abuse seriously in our discussion boards. Only flag comments that clearly need our attention. As a general rule we do not censor any content on the site.

The only content we will consider removing is spam, slanderous attacks on other members, or extremely offensive content eg.

Interstellar

We will not remove any content for bad language alone, or being critical of a particular book. Just a moment while we sign you in to your Goodreads account. Rate this book Clear rating 1 of 5 stars 2 of 5 stars 3 of 5 stars 4 of 5 stars 5 of 5 stars. She nodded, then turned and walked back to the gardens, whispering before she left.

You've always been able to do it before. I then left Ruth and the other gardeners, their gazes following me as I departed. And as I met up with Segni, his eye had wondered to the basket I carried as we walked. Reaching a hand over, he rooted through the arrangement of food until he found the three strawberries at the center and tucked them into his shirt pocket.

Where to find Adrian Holland online

And his hand returned to the basket, removing a green bean, then a tomato, and other produce until only two of everything remained. Nean dragged his knife along the wall, leaving a long scratch behind him as metal grated against metal, absentmindedly flicking the edge from time to time to scatter ice on the ground.

Then, minutes later, we arrived at the door, and placing my hand against it I could feel it humming, vibrating from something behind it. I will present the gift and accept theirs in return. Other porters, force the door shut if we have issues and after we escape, and hold it there. Now, how much longer do we have to wait? I'll be retiring to sleep, as there just so happened to be an interruption last night that cost me several hours, as you know. We'll give it fifteen more minutes, and if nothing happens, then-".

With a crack the ice along the seam split, shattering onto the floor and scattering down the hall as the door opened, propelled forward with such force that it slammed against the wall.

• Teaching Yoga: Essential Foundations and Techniques
• The Dove in the Eagles Nest
• The Nonprofit Development Companion: A Workbook for Fundraising Success (The AFP/Wiley Fund Developm
• Assessment in Action in the Primary School (Primary Directions Series)
• Schwarzes Gold: Roman (German Edition)
• Craft Capitalism: Craftsworkers and Early Industrialization in Hamilton, Ontario (Canadian Social Hi