Sunday, 29 March 2015

The Future in Space: Escape Pods, Part I

A SF Staple

   For me, the introduction to escape pods came via Episode 1 of Star Wars, and the small capsule that R2-D2 and C3PO used to escape from the Tantive IV.  Then there were the triangular Sovereign class pods from Star Trek: First Contact, the spherical escape pod from Starship Troopers 3: Marauder, and the flying coffins from Prometheus(yes, I am going to wash my mouth out with soap after mentioning that abomination).  Escape pods are an established feature of SF spacecraft, and unlike many other features shown by hollywood as vital, they appear to be a logical addition to any ship.  In a more realistic SF 'Verse, however, it seems unlikely that a deep-space craft will be so equipped, for reasons that will be explored later.  The type of spacecraft, its mission, and the 'flavour' of the 'Verse all affect the utility of a escape pod, and while they may make sense in the context of Star Wars, they may not apply to many situations in a hard SF world.

Escape Pod: Definition

   Like many kinds of SF tech the escape pod is often confused with other vehicles, and/or misnamed. Quite often there are small spacecraft that serve the same role, such as the Narcissus shuttle from Alien, or the escape craft in which Ripley, Newt, and Hicks escape from the USCSS Nostromo in Alien3(more soap).  These two craft do not qualify as escape pods because they have an extended flight capability, enabling in them to make planetfall from beyond orbit, or reach a inhabited system from deal space.  As in the case of the Narcissus a 'lifeboat' the craft such as these may in fact be the auxiliary vessel carried as part of normal operation; this is seen in Star Trek(2009) when the USS Kelvin was evacuated with the shuttles.
   An escape pod can only be used to reach the surface of a planet from orbit, and possesses only enough DeltaV to deorbit, often combined with atmospheric braking.   If used in deep space the pod would simply float until help arrived, as it could if the planet was unsuitable for landing.  This is the type seen often in Star Wars, especially the animated Clone Wars, although those are far more sophisticated than might be the case.  Unlike a 'lifeboat' craft escape pods are often seems as disposable, having only enough power to make a safe landing and call for help.

Arguments For & Against

   Escaping from a dying spaceship just in time to see it exploded in a nuclear fireball moments before the escape pod begins to tear into the atmosphere of the inhabitable, uncharted planet...  This is kind of fiction that inspires the inclusion of escape pods in spacecraft designs.  Desirable as it might be, however, it is only a fiction.  Space is a relatively benign environment; a crippled spaceship will not sink, be torn apart, or explode as an aircraft, ship, or submarine might.  And don't forget, in space none can hear you scream, so you will be waiting a long time for help.

   Deep space is a different case to a planetary system or orbit itself, so I'll discuss it separately.  The most effective way of analysing an escape pod in deep space is to compare it to the lifeboats on a cruse ship.  I know, space isn't an ocean, but in this case it is a helpful analogy.  If a cruise ship sinks the lifeboats have on job - keep people alive until help arrives, which, given the number of ships in major shipping lanes, should not be too long.  It seems safe to assume that a space liner could use escape pods in the same way, but this fails under several criteria.  One, the spaceship cannot sink, so there is no danger to staying aboard a spaceship that has been disabled by a failure or meteor strike.  Note that NSWR spacecraft are an exception to this, as they can explode if the tanks fail; but even then it would be better to jettison the tanks themselves.  The ship will be compartmentalised, so even severe damage should leave heritable sections.  Two; the pods cannot carry sufficient life support, food, or power.  One a lifeboat in the pacific there is air, sun for solar power, posable fish, etc. to help you survive.  In space, any escape pod or 'lifeboat' needs to carry oxygen, filters to scrub CO2, water recycling, etc.  This might be doable for the short term, say a few days to a week, but on a Hohmann transfer that is going to do no more than prolong the agony.    And if the ships in the 'Verse are fast enough to rescue the survivors, then escape pods are not needed, they could just stay with the ship and its greater supply of food, power, oxygen, etc.   So it can be seen that escape pods are infeasible for deep space; dangers like fissioning fuel can be easily dumped, and the pods are going to have fewer resources.

   Near space has the same limitations as deep space, but orbit does allow the use of escape pods.  Over a habitable planet all the pods have to do is land, something that can be accomplished with far less weight than survival for a few weeks in deeps space.  For this task a escape pod might be a one man device scarcely larger than a phone booth; the drop pods used by the ODST in Halo would be quite similar to what would be needed.  Or it could be larger, carrying several people and enough supplies to last them for weeks or months, along with communications equipment.  If the planet is hostile - incompatible atmosphere - then there is no point landing, and it is better to stay in orbit where the arguments against escape pods in deep space apply.

   It seems that pods are of the most use when in the vicinity of a planet, which means that Star Trek and Star Wars got something right at least.  It also makes them unlikely to be found on spacecraft that spend a long time in transit between destinations, due to the weight penalty.  The place they are most lily to be found is on a space station.  Stations likely carry far more people aboard than can be evacuated by shuttle alone, have less of a weight limit, and are normally close to planets.  Which brings up another constraint; the planet must be habitable, or at the very least, non-hostile.  And these may be few and far between in the real world.

   The above points can be extrapolated to indicate the type of 'Verse in which escape pods are going to be a commonplace, and where they will be used.  Space stations over habitable planets will be the main use, followed by ships that have large crew/passenger numbers and which regularly pass habitable planets.  Note that within a solar system this is unlikely, so you are looking at starships.  Given the difficulty of interstellar flight, and the time spent in deep space away from any planet, means that only FTL starship really befit from escape pods.  This is the case in Star Wars, where hyperspace is used to jump from one habitable planet to another.  Usually the starships are close enough to a habitable planet that escape pods are a perfect safety measure.  FTL comms also make them more practical, as it allows for a much higher probability of rescue, especially if the starship went down outside normal travel routes.

   So you end up with a moderately hard 'Verse.  One in which the technology and setting are generally crammed with realistic science, but in which there is FTL travel and communication, a unlikely number of human habitable planets, and starship design that goes in for catastrophic failure(or space battles in orbit, although it is unlikely anyone would survive from the loosing ship,  no matter what escape methods they had planned).

 Note from Author: to anyone who has been waiting on a new post, sorry for the delays.  Blogger decided to eat all the draft posts I had half finished, for some as-yet unidentified reason.  Anyway, I should be back on track and posting once a week again now.  Upcoming posts will include a look at tactical manoeuvring in a space battle, hydroponics and aquaponics, arcologies, and residential space satations, so stay tuned.

Friday, 13 March 2015

Free Blenderings: Bussard Ramship Mesh


   So this is a ramship I whipped up last night 'cause I was bored.  It took about three hours...don't know if that's bad or good.

   It is pretty much complete, but with no secondary details.  I may finish it, but I seem to let Blender 3D models go unfinished most of the time, perhaps because I can't render them.

   One of the blogposts I'm working on at the moment is a close look at the 'railroad' model of beam-riders, and the starship will probably look similar to the model, so keep a lookout.

The inspiration.  Image from Atomic Rockets.


Friday, 6 March 2015

Fight Or Flight: the Kzinti Lesson & Combat Spacecraft

The Kzinti Lesson

Postulated by the SF author Larry Niven the Kzinti Lesson states simply that 'A reaction drive's efficiency as a weapon is in direct proportion to its efficiency as a drive.'  Or as TV Tropes calls it, the weaponised exhaust.  Would you want to be standing behind an Orion drive spacecraft when it started a burn?  How about a mass drive system, or a Beam Core Antimatter Drive with a exhaust of pure gamma rays?  And photon drives have 300MW of power per newton of thrust.  Given the energies involved with fast interplanetary flight, or even slow interstellar, the most powerful weapon a future space warcraft may have at its command is the main drive unit.

   Of course, the drive plume of most spacecraft is not well collimated, and so it would be a short ranged weapon at best.  With a plasma exhaust, however, it might make an effective 'soft-kill' weapon.  The direct effects of the particles, along with secondary radiation, could damage or destroy sensors, weapons, and any other equipment mounted on the exterior of the craft and making a boarding action feasible.  Most photon drives, mass drives, and a few others have collimated exhausts, and are in essence gigantic DEW weapons.

   The connection between weapons and drives is much more closely intertwined however.  In Footfall, one of the greatest SF invasion stories ever written, the battleship Michael uses an Orion pulse drive.  It carries a secondary armament of battleship gun turrets, but the primary weapons are the so called 'spurt bombs'.  These are nuclear pumped lasers, primed by the same detonations that accelerate the spacecraft.

   This got me thinking.  Of all the different spacecraft drive systems so far invented or imagined, which lend themselves most readily to a particular weapons system?   An externally powered craft like the Michael has to generate power if lasers and EM guns are used, so unpowered weapons like Bomb Pumped Lasers become ideal, as well as dovetailing nicely with the existing logistical needs.

   The other kind of nuclear pulse propulsion, that of Inertial Confinement Fusion has a battery of powerful lasers as part of the drive system.  Surely a spacecraft could be designed with the lasers deep within the hull, routing beams either to the weapons or drive as needed.  This also introduces and interesting tactical element when a spacecraft's commander must decide between firing his laser cannon, or accelerating.  Electron beams and particle beams can also be used in the same way, although with greater difficulty re-routing the beams.

   In the designs for the ~250 km long Bond/Martin worldship design the drive is a scaled up Deadelus style pulse system.  But each 'pellet' weighs in at several tonnes of deuterium/hydrogen ice, and is ignited by a kinetic slug accelerated to a blistering 1,000 km/s, or 0.33% of the speed of light.  At that speed one kilogram has 5*10E11 Joules of energy, about the same as three ATBIP bombs, basically scaled up MOABs.  To put it into perspective the Project Thor Rods from God kinetic impactors have ~5*10E10 J.  Nothing could survive a hit from something of that calibre.  It might be hard to aim a many hundreds of kilometres long spinal mount, but nothing would need a second shot.  Given, accelerating it to that speed is a massive challenge.  It might end up being a beam powered spacecraft in its own right.  Do the math on the impactors acceleration, its a little scary.

   On a smaller scale this means that many if not all spacecraft have at least a short ranged weapons system, which is good for the plot.  On the other hand it reduces the number of people who are actually allowed to have a spaceship, which is a bad thing from a SF authors point of view.  On a large scale it means that habitats with the ability to move under power through a solar system could easily wipe out every other habitat, making for a very balkanised setting.  And if your 'Verse contains forcefields which allow fusion drives with star-core conditions...  Best to keep an eye on the brake lights of that tramp freighter up ahead.

Thursday, 5 March 2015

SF Soldiers: Child Armies

Child Soldiers in SF

   Child soldiers are a trope of SF that occurs relatively really, and is handled seriously even less often.  More common are situations like that of the Hunger Games, or Lord of the Flies, in which children are shown combating one another, but are not actually soldiers.  There are some works that show children conscripted into armed forces, but most often it is only the protagonists, and for reason of their special abilities or a necessity imposed by the situation.  For example, the children in the Ender's Game universe are recruited young in order that they can be trained more fully to command in space than a adult or teen could be.  Battle School was not intended as a recruit camp, it was a device for finding the best possible commanders.  That Ender, Bean, Petra, and the others were so young at the time was a product of chance.  The IDF would doubtless preferred them to have been older at the time of the battle.  This being the case Ender's Game is not focused on the idea of child soldiers; they are not intended ever to actually engage in direct combat.
   A few works are more focused on the theme; The War against the Chtorr, Century Rain, and others.  The most common reason behind the use of child soldiers seems either to be the flexibility of a young mind, or because numbers are crucial in a battle for survival.

In the Real World

   In the Medieval period - and earlier/in other places - boys were made pages at about seven, becoming squires at around 12, and fighting in battle by mid-teens.  This was a function not only of the training needed to be effective in medieval combat, but also of the reduced life expectancy; you grew up fast or died, even in other lifestyles.
   In ancient Sparta training began at seven, again a result of the political situation in Sparta, where the helots outnumber them at all times.
   More recently children have been used in various small wars and conflicts, most often in Africa; a quick google search shows that a horrific number are still forcefully recruited, brainwashed, and used against all and any opponents.  Many of the terrorist organisations extant today continue with this tactic.  On the other hand, many modern militaries allow recruits to join as young as 16, but do everything possible to keep them off the front lines until they are older, or place them in non-combat roles.  And of course, in rebellions and uprising there are always teens and young children to be found, most notably in Europe during WW2, but also in other times and places.  Even in armies which do not employ children or teens as soldiers they may serve as support personnel, cooking and maintaining equipment, although this seems to be uncommon.


   As depraved as the action itself might be, there are several highly logical reasons that child soldiers are used.  The impressionability of a child's mind enables them to be easily brainwashed - perhaps with the aid of drugs - making them suitable for terrorist acts, either covertly or in smash 'n burn raids.  The fact that it is a innocent and harmless child attacking them makes the physiological trauma of those attack much deeper, especially in the case of soldiers forced to gun them down.  And how do you decide to shoot the child running towed you in a city your unit is patrolling?  Are they looking for protection or to kill?  Quite apart from the trauma caused to those whom the child soldiers fight, they themselves may never recover, even if they live.  The child mind is so impressionable that any conditioning it receives can be irreversible, making them loyal and obedient even to the most evil and gruesome commands.  For these reasons the use of child soldiers is seen as one of the most evil of war crimes, something often reflected in SF where the creators of a child soldier program are attacked after the enemy had been defeated, like Graff in Ender's Game.

   In SF the main reason for the use of child soldiers as a regular fighting force seems to be in a war against an alien race.  In such situation the speed with which troops can be put on the battlefield is imperative, and so using children or teens is an advantage.  They can also be more easily condition, medically and physiologically to cope with the stresses of such a war.  the HALO franchise is one of few that depicts a program using children for this reason.  The SPARTAN-IIIs were composed of young orphans turned into disposable super soldiers that could be expended against the Covenant.  As fatality rates for their missions were often 100% mental conditioning would be central to getting them to fight their hardest, and preventing them from cracking u when they survived with most of their friends dead.  This seems to be the most mainstream look at the use of children as a frontline army, and even then they are not the primary fighting force.

   Apart from the mental aspects children could also be selected because they cold be bred more quickly.  Although it is hard to imagine a situation in which anyone would be desperate enough to breed humans for war, it could arise in an alien invasion.  In a SF 'Verse this would explore the absolute hopelessness of a war against a superior enemy, as well as examining highly complexed moral and ethical issues.
   For a war in space children are small and lighter.  A battalion of child soldiers with weapons and supplies will weigh less and take up less space than a adult force, making them more operationally flexible.  Also, less material is used in making their weapons and equipment, vital if resources are running low.  For example, if powered armour is used it could contain large amounts of rare earth metals, which are called rare for a reason.  Thus the smaller the amount used per soldier the better.  A smaller soldier can also hide better, access smaller spaces, and is harder to hit in combat.

Building a SF 'Verse

   But why would you write about this?  One reason that the theme of a child army is so little seen as opposed to a single child hero is that it is a very terrible thing, one which none is comfortable even thinking about, especially as it is going on in the world today.  It is not something that should be included in a SF 'Verse for 'shits 'n giggles', it should have a purpose.  Outside of the main story arch it can denote a truly evil faction in a war, or one that is terrible desperate to win.  Within the main story it can be used to explore the these of identity; do we have to loose our humanity to defeat the aliens kind of scenario.  However it is used, its inclusion in a SF 'Verse will have great impact, and could make an apocalyptic story far darker than the usual run of the mill.  The most interesting focus would be not the child soldiers, but the adults who created them struggling to accept what they have done.

Slow Interstellar Travel: The Enzmann Starship

The Slowship

   Generally speaking there are two approaches to manned interstellar flight.  One uses high technology to build a small(realativly) starship that can achieve a high fraction of the speed of light, making the journey in a few decades or less.  This has the disadvantage of relatively small payloads, making colonisation difficult without a fleet of ships.  The second alternative is to use a ship that travels at only a few percent of the speed of light or less, making the voyage in possibly hundreds of years.  These are the slowships.  Most commonly they are seen as worldships, each one capable of supporting thousands of people for hundreds of years.  This approach has the advantage that the ship is elf is a colony, making the initial settlement no different than the voyage that came before.  However, the ships are truly huge, and may be beyond the ability even of a united star system to construct.  One of these ships, and perhaps the most interesting for a author of hard SF, is the Enzmann Starship.


   The Enzmann starship is simple in concept.  A cluster of thermonuclear pulse engines, a habitat section holding ~200 people, a massive ball of frozen deuterium, and a cruising velocity of up to 0.3 c.  Conceived in 1964 by Dr. Robert Enzmann there have been several variants in which the size, number of drive units, and method of storing the fuel were explored.  Detailed information on the Enzmann is hard to find, however, so I am unable to venture into a discussion of the differences between the variants.

   The most iconic feature of the starship is the several millions tonnes of deuterium propellant stored as a gigantic sphere on the nose of the craft.  Originally this was to have been unconfined, the deuterium 'ice' supporting its own weight.  However, this was shown to be unfeasible and later designs used a seamless metal shell.  This was created by inflating a thin plastic balloon, on which metal plasma is deposited to form a flawless sphere.  I have no idea if this is really feasible, but it could be perfect for manufacturing habitats, starship hulls, planetary domes on airless worlds, and giant reflectors for photon starships.  It might also prove to be a viable technique for working with refractory metals, extremely difficult in the normal way of things.

   Annoyingly, the exact engines use are never discussed in any of the literature I managed to find.  That they are nuclear pulse units is always stated, but this is never clarified.  The deuterium fuel suggests that a arrangement similar to the Daedalus starship is intended, but with multiple smaller units, although a reason for this is not given, perhaps for redundancy.  Note that deuterium requires an external ignition system, unlike an Orion drive, which cannot be used in a cluster of engines - I think, again this was something I was unable to find a definitive answer on.  They could also be internal pulses, like the drive used in the Helios designs exempt that this has a Isp far to low for a serious interstellar starship other than, perhaps, a multigenerational starship.  The more modern development of the magnetic inertial confinement drive might fit the bill perfectly, although requiring a change of propellant.  Thinking about the number of engines used it occurred to me that as the starship is likely to be turned into a habitat when it arrives at the destination system, the drives could be stripped off and fitted to smaller vessels composed of other pieces of its structure, allowing the more rapid expansion of the colony.

   In some sources a cruising velocity of 0.3 c is stated.  This may well be attainable with a Daedalus style drive with high Isp, but seems unlikely for a thermonuclear pulse like Orion.  An interstellar Orion starship is often given a cruising velocity of 3% c, although it could be made slightly higher if the fuel fraction is increased considerably.  Magnetic/inertial confinement fusion, steady state or otherwise, could well provide the necessary performance.  The daedalus starship does not have a capacity large enough for a multi-generation voyage, which would be required with a 0.03 c cruise, but could carry sufficient range of ages to make a 0.3 c voyage possible.

   The final plausibility of the Enzmann starship is debatable, and depends on many assumptions about technology and construction that are answerable only through practical groundwork.  Such a large vessel would also require a very robust economy to produce.  However it basic configuration - multiple engines, large spin habitats, and a single huge fuel tank - have several advantages.  In a follow up post I will look at the what these advantages are, and the way they could be applied to a SF 'Verse to create a setting for interstellar colonisation.