Making EM Guns Viable in Space Combat (3e)
 

I have a quick question for you guys, I've been working on a few settings with EM guns being a shorter-ranged weapon for spaceships (including a 'Transhuman Space/Traveller' style setting), and there is one problem: EM guns, well, suck for void combat. The general consensus I've seen is basically EM guns aren't good enough, particularly in the range and speed department.

Before I go into an ad-hoc rule to improve EM guns, I first want to clear up any preconceptions:

First, how fast are EM guns in general? I've seen some 2km/s velocities here and there, but nothing concrete.

Second, I keep hearing that all kinetic weapons have some self-guidance capability in space. Is this true from a game standpoint?

Third, other than a void/near-nonexistent atmosphere range modifier of 5, there are no other modifiers for kinetic guns.

If I'm missing something, then please correct me.

Now for an ad-hoc solution that one of the guys who worked on GURPS Vehicle Builder gave me:

So, the basic idea is that instead of electromag being just 4, it's (TL-4), showing improvements to various systems allowing for faster projectiles for the same mass.

Am I on the right track, or are there other ways to make kinetics work in space?

Re: Making EM Guns Viable in Space Combat (3e)
 

2 km/second is a speed for guns used in atmosphere where ammo terminal ballistic characteristics are important. If you go radically faster your projectiles start burning up like meteors as they fly through atmosphere and then exploding like meteors when they hit.

Early railgun research did produce higher velocities but it used experimental rigs that had to be re-built after every firing and that's where they also discovered that they had limitations on useful projectiles.

Velocities higher than 2km/second can probably be produced (by unknown future tech) for combat in vacuum where it's okay if the projectile explodes on impact making shallow craters.

2. is a rule in Gurps Spaceships and is part of its' efforts to make projectile guns more useful.

I would say that the "best" way to make EM guns more useful is to use the ^ rules of the setting to play around with engagement distances. For example you have a setting where ships "pop" out of FTL at specific Jump points and almost all fights occur at such places at very short ranges by space standards.

If you have a hard science setting based on our solar system the the defenders of Earth will see when the enemy fleet leaves Mars and will plan their intercept at the maximum practical distance. It won't matter what EM guns "could" do. Lasers (and maybe missiles) will have finished the combat before EM guns come into even extended ranges.

Re: Making EM Guns Viable in Space Combat (3e)
 

Keep hearing where? In GURPS 4e Spaceships? GURPS 3e Vehicles does not make that assumption IIRC. Other speculations about combat above the atmosphere might or might not assume that.

Real artillery has the limit that the faster the accelleration, the harder it is to put anything inside the shell such as a bursting charge (for combat in the atmosphere) or terminal guidance (for combat at orbital velocities where any mass explodes on contact). But railgun projectiles experience such intense electromagnetic fields that terminal guidance might not be practical.

Fred is correct that outside an atmosphere, projectile velocities are not limited by air resistance and desire to keep the projectile from melting or exploding in transit.

Re: Making EM Guns Viable in Space Combat (3e)
 

From my research, unless you're talking about things like Mass Effect's 'grain of sand' projectiles, you need to hit velocities up to 15km/s before the atmosphere causes problems. Though, thanks for the 'more than 2km/s units were tried, but they were completely useless after every firing' bit.
For one, it depends on the setting.

For example, one setting -the lovechild between the Sci-Fi Annos and Transhuman Space- only has HePlaR rockets and would have space EM guns with velocities of 10-15km/s, given that ships can't achieve more than 5Gs of acceleration and a general tech level of TL10 with things like TL11 computers and biotech. Most combat takes place in the orbitals of a planet or asteroid.

Another setting -which is a lovechild between Transhuman Space and Traveller- has a general space EM gun velocity of 100km/s or 200km/s being the norm. Quite a few ships use a combination of HePlaR and inertialess drives (in the case of the equivalent of the Third Imperium, their warships have both, so when they get into combat, they can rocket around without paying through the nose in energy requirements) for STL movement. However, the upper limit of this is planned to be around 12Gs.

Re: Making EM Guns Viable in Space Combat (3e)
 

A guided missile which impacts (or bursts just before impact into a claymore-mine style spread of projectiles) is a kinetic energy weapon too.

Re: Making EM Guns Viable in Space Combat (3e)
 

No. My example about the invasion fleet launching from Mars and being met halfway to Earth was from a big battle I did during the Spaceships playtest with _much_ more restricted tech than you describe but its that approaching through normal space giving days of warning that means battles will be fought at long ranges..

Attackers seeking to capture orbital structures won't begin with long range bombardment but defenders will seek to destroy the attackers as far from the orbitals as possible.

Oh and in either3e or 4e if you're seeking to achieve the performance you spoke of for your HePLar rockets you need to use generic Total Conversion thrusters. No species of realistic nuclear rocket will do.

Re: Making EM Guns Viable in Space Combat (3e)
 

In a setting that doesn't have particularly potent energy weapons, kinetics do rule, it's just that 'kinetics' means 'guided missiles'.

Re: Making EM Guns Viable in Space Combat (3e)
 

I still consider them missiles, just with a KE warhead instead.
So you're telling me to just give up on KEW cannon entirely?
Also, if I did the work right, you can get HePLar rockets to work like that. Though the last prototype I did had the dV being only about 20Mm/s^2 (which is beyond any conceivable traditional rocket) for what amounts to be a patrol cutter. You might not be a giant pile of guns, but it works.

Re: Making EM Guns Viable in Space Combat (3e)
 

Cannons have been pretty much obsolete in aerospace combat since TL 7, and the space combat environment is even more hostile to their use than the air combat environment.

Re: Making EM Guns Viable in Space Combat (3e)
 

More like TL8. There were lots of kills with cannons in the 60s and 70s, even from forces with AAMs, and that's only considering air-air combat.