Friday, April 3, 2015

D Is for Deflectors

Ships in science fiction get shot at sometimes. I understand there are a couple of films based on that premise that did fairly well. Add in radiation, meteors, orbital debris and lousy piloting and you begin to wonder how starships get anywhere at all without being riddled with holes and without a whole lot of air left.

Ships in space can't hide. Ken Burnside spoiled that for everyone (sorry Romulans!) You can be seen by your body heat a hundred light seconds away (your body, not that tin can you're flying around). So basically ships in space have three responses to attack.

Dodge! This might be problematic if missiles are significantly faster or more maneuverable than you but sometimes it's all you have. Contrary to popular belief dodging can give some benefit against lasers. Even light speed weapons will have a finite time lag in space unless you are close enough to make harsh language viable. Furthermore a laser has to be held on its target long enough to do damage. If it washes over your ship at 500 meters per second that energy is being smeared over  half a kilometer. Just be aware eventually your luck is going to run out. Chanting about being a 'Leaf on the wind' only got the Serenity so far.

Countermeasures. You can kick out dust, aerosols, flares, chaff and what have you to kill or distract missiles and diffuse energy weapons. The downside is that some countermeasures have ammunition too and will eventually run out or your defense lasers will miss a projectile. Any countermeasures can be overwhelmed by sheer volume of fire.

Suck it up! Build your ship really tough. Armor it then reinforce its structure then armor it some more. Only SF weapons are pretty brutal and if you pile enough armor on your design you discover the fine line between a ship and a small moon.

Enter the deflector! The deflector is an energy field that blocks or absorbs damage to a ship which is another way of saying we don't know how to make it yet. Stopping solid projectiles is a matter of directing tractor fields to knock them off course. Yes a tractor beam can knock a missile off course. Your opponent is trying hard to aim a missile where you'll be. A tractor beam would pull said missile to where you are at that moment and hence off course. If your culture has artificial gravity then they ought to be able to build a tractor beam to defend their ships. If you don't have artificial gravity what kind of a space tyrant are you anyway?

I have no idea how a deflector would protect against lasers. If you used gravity to make a gravity lensing effect I guess you could make a beam spread out or bend it around your vessel but that sounds like a lot of power. In nature only galaxies or black holes bend light that much. If you can generate effects on that level you don't need lasers. Just cause tidal effects to rip your  target to pieces. If the other guy's ship implodes you're doing it right. As a personal note it'd take laser that makes the Deathstar's look like a glow in the dark cut out to make me gamble on sticking myself in an artificial black hole.

Most deflectors simply diffuse or absorb attacks with no black hole effects. It seems visible light goes through them with no problems too. It's an oddly specific level of radiation stopped. In The Mote in God's Eye, by Larry Niven and Jerry Pournelle, the defensive shield did stop all radiation and ships had to create holes in it for laser cannons and sensors to peek through. 

A variation on the deflector is a stasis field (also by Niven in his Known Space series. Within a stasis field time stands (almost) still and you are invulnerable. Presumably there's a timer outside the field. If you see a missile coming turn on the field till after the boom (and hope it doesn't hit the timer).

Your space opera deflector simply is turned on and makes your ship harder to hurt. The ship still looks the same so maybe the field only works one way. Of course that might mean it interferes with sensors on its own ship. Another factor people don't seem bothered by is how a shielded ship gets rid of waste heat. Do the shields themselves take the place of more primitive radiator fins? This would be a cool explanation why space opera vessels don't look like windmills. 

Some vessels may have more limited (read realistic) shields, for example a magnetic shield to protect against particle radiation. This might explain why ship hulls in Traveller are steel and so darned heavy. Steel is a good structural choice but it sucks at soaking up radiation.

As a final note a good dependable deflector can eliminate many structural elements lightening the weight of a ship at the cost of more energy usage. Who needs a shuttle bay door? Use a deflector. Ditto for airlocks (at least the outer door. Elevators can be simplified, just a tube with a deflector projector at the bottom.  Deflectors could even be used in life systems in place of airbags. Or you can opt for total comfort and have a deflector bed where the mattress is replaced by a deflector for comfort and protection from laser fire.