Wednesday, 17 December 2014

Force-Fields; Not Just Defence

   Force-fields - or shields, screens, deflectors, etc. - have been a recurrent trope in SF since the creation of the genre; scarcely has there been a mainstream novel or movie that does not feature them to some extent.  Like many other SF magitech devices force-fields often shape the story and 'Verse in which it is set; without planetary defence shields the Rebel Alliance on Hoth would have had little chance against the might of the empire.  Star Wars is not alone, the universe of Dune, Star Trek, and countless others use the technology in a unique way.  Usually the factors and applications considered revolve around the primary usage of forcefields in SF, defensive measures for military vessels.  In this article I will look at a few, most of which have admittedly little impact overall on the 'Verse in which they are used, but which help to anchor the story and the readers attention firmly in the future world.

   For the sake of simplicity the forcefields in this blogpost are assumed to have the following characteristics; can be projected in a variety of geometrical shapes, have mechanical strength, repel kinetic and radiant energy.  It is also assumed that either the forcefield is invisible when in matter-repelling mode, or it can be tuned to block or admit certain frequencies of light.
  • Airlocks:  this has been seen in both Star Trek and Star Wars, and might be one of the least stupid of the non-defensive ways that forcefields have been used.  The entrance to the hangar bay has physical doors, a forcefield that allows slow moving shuttles to push through is activated when required.  As air molecules move quite fast, they cannot penetrate the field, and so pressurisation is maintained.  However, everyone had better remain in p-suits; a blown fuse could otherwise result in the inconvenience of explosive decompression.  Note that a real world device called a Plasma Window can achieve much the same result. 
  • Landing Gear:  this example comes from the SF comedy Galaxina, and is employed by the spaceship Infinity to overcome the problems with landing on uneven ground.  Like the forcefield airlock this is well and goo, until the power fails and several hundred or thousand tonnes of spaceship crashes to the ground.  While it would be somewhat foolhardy to equip a normal spaceship with these, they could serve for special landings where the ground is unhardened, say for military or rescue missions, with the forcefield acting like a futuristic giant snowshoe.
  • Structural Reinforcement: the ships of Star Trek's Federation are much maligned among engineers and those of scientific bent for their structurally stupid design.  The narrow struts connecting the hulls and warp nacelles are under incredible stress in any manoeuvre, and to come with this the ship uses Structural Integrity Fields.  Again, good until the power goes out, which is probably when you don't want the ship snapping into three pieces. 
  • Emergency Containment:  although - yes, power again - physical barriers are probably preferable for containing anything from prisoners to poisonous gasses, forcefields might prove indispensable in an emergency.  If they can power up in instants they could seal off an area far sooner than ponderous blast or containment doors, felling to seal off of dangerous situation in moments. 
  • Life Support:  the vacuum of space makes simple jobs a nightmare, pushing the costs or orbital construction sky high.  If a starship under construction in orbit could be enclosed with a forcefield just strong enough to contain an atmosphere, matters would be much simpler.  Even though for safety p-suits would still be worn, the 'air' could equally easily be there to enable plasma cutting as breathing.  A forcefield on a pant could be used as an emergency shelter from natural attacks such as volcanos, tsunamis, and hurricanes.
  • Power & Drive Reactors: the lower limit to the size and weight of a nuclear fission power supply is the critical mass needed for a sustained reaction.  However, if the forcefield is a perfect neutron reflector it is easy to see how it could cause even a few grams of uranium or plutonium to fission.  The resulting plasma could be confined by the forcefield and piped through a magnetohydrodynamic generator, the whole package limited in size only by the forcefield generators.  Fusion could be treated in the same way, opening up the way to abundant clean energy.  The most obtuse of the implications that result from this is the development of torch drive spacecraft, which I will discuss in a future post.
  • Energy Storage: antimatter is often proposed as the ultimate starship fuel; a misleading statement.  Like the use of hydrogen as car fuel, antimatter acts only as an energy storage device, a battery.  Starships need astronomical amounts of energy, so antimatter is used as giving the ultimate power-to-weight.  Create a hollow container from a forcefield, fill it with a vapour that absorbs a frequency of light allowed to pass through the field.  Energy is added to the 'battery' with lasers, and thanks to the phenomenon of electron shells the light released by the vapour is unable to pass the field, most of it at a different than original frequency.  A device such as this could have no limit to the energy contained, making 'nuclear hand-grenades' look like damp firecrackers.
  • Directed Energy Weapons: as anyone familiar with the Kzinti Lesson knows, the exhaust plume of a starship or torch drive spaceship is as deadly a weapon as can be found.  The Fission Fragment Rocket, possible to build in the real world, has an exhaust velocity of a few % of c, making it a deadly beam weapon at close range.  By piping the plasma from a fusion reaction out through a forcefield nozzle a devastating weapon could be created; it disadvantage a fairly short range due to the dispersion of the beam.
  • Airships: if a forcefield has no mass in and of itself, it makes the perfect airship hull.  Possibilities include vacuum airships, high temperature thermal, airships that change shape to attain supersonic speed, etc.  Nor would an airship built in this way suffer from the fragility of conventional designs, making it much more practical than any physical airship. 
  • Re-entry Shielding: for a large or fast spaceship a re-entry shield is much to heavy, despite the advantage in fuel reduction that the Leonov demonstrated.  A forcefield, especially if already fitted for military defence, is a perfect substitute, and if power fails, your probably screwed anyway.  By allowing aerobraking the available delta Vee for a mission could be doubled, or the fuel load halved; a significant improvement.  Also, as it could be much larger than the actual ship, and of a more aerodynamic shape, g-load could be altered to be less taxing.
  • Cassions & Civil Engineering: a cassion is a temporary dry-dock of sorts, built to enable the construction of underwater structures.  A forcefield by its virtue of easy deployment - on/off switch - is ideal for rapid or emergency construction.  
  • Tools: this is seldom seen, the only example I have personally come across being in Asimov's extensive 'Verse, where forcefield tools are far more capable than mechanical counterparts.  The advantages of such theoretical tools are many, and are discussed on Atomic Rockets.

Update (14 JAN 2015)
   As can be seen in the comments for this post, reader Yoel pointed out a two applications I had completely overlooked, so I'm adding them in.
  • Ramscoop:  the greatest challenge of constructing a Bussard Ramjet, one of the most advanced and powerful starship designs, is the construction of a magnetic field capable of collecting the interstellar hydrogen needed by the design.  A forcefield could be just the solution, especially if it is massless and frictionless.
  • Solar Sail: the solar sail is an interesting design that cannot ever come to its full potential due to material constraints.  In essence the solar sail uses the momentum of reflected sunlight or solar wind, having theoretically infinite delta Vee.  However, the mass of the sail, combined with the inability of find a material that will withstand solar heat at the closer, and thus more effective, distances means it is not likely ever to be widely used.  A forcefield, however, might be massless and perfectly reflective, making it the ideal method of producing a solar sail, and thus providing a reliable method of interstellar transport.  In fact, this is such an effective interstellar design that I have decided to do a post on Interstellar Transport, featuring such a design and explaining its implications. 


  1. Hi Moran
    Good article, I have a few notes:
    1. Force field as air locks
    Even if your force field can be tuned to repel fast objects like air molecules (the average velocity of oxygen molecules at room temp is 470m/s) while allowing slow objects like astronauts & ships to enter, you need to remember that not ALL of the molecules moves at that average velocity and that some of those molecules will hit the shield at shallow angle meaning the perpendicular velocity (relative to shield) will be very small.
    The result will be small diffusion thru the air lock.
    2. Force field as funnel
    A ship can manipulate the field to form a funnel; the funnel can scoop the interplanetary/interstellar space for hydrogen atoms and funnel them to the reactor/engine.
    The funnel will feed a fusion reactor in the case of true Bussard Ramjet or in the case of Ram Augmented Interstellar Rocket (RAIR) will provide propellant for a rocket powered by fusion or fission reactor.
    3. Force field as solar/beam sail
    Solar/beam sail construct from very large, very thin & very light reflective sheet.
    If Force field could be manipulate to form reflective disk it could served as a Solar/beam sail.
    The field mass will be zero (?), infinity structural strength with no need of beam or string, easily deployed/folded etc.
    Unlike physical sail that sensitive to high solar radiation, the solar Force field ship can deployed her sail very close to the sun (0.05AU) and accelerate due to the high trust to high velocities.

    Keep up the good work!


  2. Thanks for the comment. I had completely overlooked the use in a bustard ramjet or solar sail, so I'll have to edit them in. Thanks again!


  3. What about particle beam weapons or mass drivers? If the force field could be manipulated to accelerate objects then it could be used for propulsion or weapons.

    1. Possible, yes. It falls more under the heading of tractor beams and the like than a force field, although the two technologies do overlap in use. I plan to do a post on tractor beams at some point.

  4. An interesting blog entry Moran, it really gives an interesting insight to one of many, many, many technologies science fiction as we know it has taken advantage of.

    The Landing Gear idea does sound interesting, but as you've noted, it does have limited application and heavily reliant on the flow of electricity to keep it active. I'm thinking that a compentent spacecraft designer would have failsafes in either emergency capacitors or secondary generators to at the very least make the sudden loss of the onboard power plant not be so sudden. Perhaps slowing the decend to something more manageable and produce less damage from impact.

    Yeah, pretty much ripped TNG's Structural Integrity Fields a new one, but it's not one without merit. Granted, it would probably work best with maneuvers that would strain the fuselage of the spacecraft structure and flex it outside the whole "reaction of the rocket engine", though I think this would be more reactive than constantly on. Rather, it only activates when strategically placed load sensors or whatever detects stress to which triggers the activation of said structural integrity field. Heck, it might even be used in high thrust maneuvers where the native engineering and conventional materials alone would not be able to prevent the ship from crushing into itself during such burns. Something that I imagine would be a must when said spacecrafts are designed to be light for deltaV conservation.

    Emergency Containment would probably work best as a rapid denial barrier that activates the moment that something bad is detected, or manually activated depending on the novel situation at hand, and deactivateds as soon as a more physical seal is made. If it's best used to do something quick, make it quick rather than linger longer than neccessary.

    A pressurized atmosphere in a dry-cage does have its advantages for cage workers, especially when they don't need to wear bulky space suits and spend time breating a different atmosperhic mix for several hours. However, it would probably be better to just have such an atmosphere containment field be more localized, modular even so that there wouldn't need to be so much space to be pressurized with air. Said air doesn't even have to be breathable, just to keep a comfortable atmospheric pressure while said worker is in an oxygen mask equivalent. The atmospheric containment fields could even be added together to increase the required work area. Though, like the Landing Gear application, it would be best to have failsafes to at least allow enough time for the worker to don proper space protection before said atmospheric containmet field suffered full failure. As for the idea of the forcefield being used as an emergency shelter, well like the Emergency Containment idea, it would probably be best if it had a physical back up door that the force field protected long enough to have it close.

    1. Accursed thing was too long.....

      A Reactor Contaiment Field, especially in the field of thermonuclear fusion, does sound like a great idea and reminds me of another franchise that utilizes the same general idea. Though I can only assume that same said reaction cannot be used to power the force field, at least not fully, thus requiring separate power generators.

      Somehow I find it dubious that a force field could be used to store energy, when it needs electricity to keep it up. But what do I know about physics?

      As for a barrel for a fusion drive-based DEW, as novel as the idea sounds I can't fathom how it could be used outside close-quarter emergency weapon situations.

      However, use as a re-entry shield is just as useful an application for force fields. Though a separate power generation system would be suggested that would supply said electrical needs long enough to get through the atmosphere, that and physical backup just in case things DO go wrong. Or better yet, the force field actualy compliments the physical reentry shield.

      Still, the alternate usage for force fields as opposed to what is seen in visual media does spark creative speculation for one's own setting. Thanks for the inspiration!

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  6. The though of force fields used as landing gear reminds me of a thought I had about tractor beams. Point a tractor beam at the ground make flying craft like helicopters that rise and fly with the energy efficiency of cranes and lifts. Point a long range tractor beam at a planet of star and you can use the entire solar system as reaction mass. Almost as good as a reactionless motor without violating the conservation of momentum.