Tuesday, February 2, 2016

Traveller Missile Addendum

I forgot to mention this.

Disclaimer: At this point I have fully embraced my heresy and now cherry pick willy-nilly from both 1e and 2e Mongoose Traveller. I denounce myself.  
My use of Traveller setting and dress falls under
fair use guidelines for both Mongoose and Far Future Enterprises.
Missile Speed
As I said last week, missiles in Traveller are slow -- probably too slow to make them effective in combat.  (Well, maybe not; perhaps you have different space combat scenarios then I do. All of mine have started at Very Long or Distant range, and it takes for-freaking-ever for missiles to reach their targets.)

To that end, I have been experimenting with increasing missile speeds. I am sure this will come as a source of consternation to at least one of my players, who said "Missiles are not beams." And this is true. But consider this post about AMRAAM G-load from F-16.net, a forum filled with war otaku if I've ever seen one:
AMRAAM like any missile will likely be able to achieve maximum G forces when their rocket motor is still burning but are able to achieve quite high G forces mid-flight. For example VT-1 missile in Crotale NG SAM system can go up to 50 Gs but can still go 35 Gs 8 km away from launcher several seconds after the rocket motor has burned out. Speed then is something like 750 m/s when top speed is 1250 m/s. I think AMRAAM will be similar and can do max G turns when rocket motor is still burning or just burned out. 
There are no citations, so I can't check the claims being made (and believe me, I've been looking for sources of hard data on missile G load, but they're passionate and I generally trust war nerds to get their data right), but they're saying that modern (TL 7) missiles can pull G loads between 30 and 50 G's, albeit briefly and usually at launch.

If that's possible at TL 7, then it sounds plausible to me that TL 12 (average Traveller tech level) missiles ought to be much faster, and Imperial maximum TL 15 missiles faster still. As tech level advances, both upper speed and duration of G-burn increase. 

So here's something one of my fellow Evil Traveller GMs came up with: the top speed of any missile is twice its tech level.  This means that TL 7 missiles have a max thrust of 14 G's... which actually fits as another of the Evil GM Cadre gave me these numbers:
The WPU-8/B engine of the AIM-120A-1 has 2,128 kg of thrust for 10 seconds then 182 for another 110 seconds. That's 14 G's. And that 14G is the average over the entire burn, it's slower at the beginning and faster at booster burnout because it's getting lighter from fuel consumption.
 Of course, the drawback to having really fast missiles is that you can't use the missile flight time chart in the core rules; you need to track its position like a craft and subtracting its thrust from that of a fleeing target in order to find relative velocity. (Not that it matters to me, I've been doing it this way for years now.)

To that  end, I present you with this very nifty spreadsheet that my friend The_Jack made. Just input the missile's thrust and endurance (and if it's launching from a craft, how fast that craft was going and for how long) and it will do the rest.

Since speed is dependent upon Tech Level, and TL is variable, we need a formula. For simplicity's sake, let's just use the base cost of the missiles as printed in the book as the baseline and then multiply them by tech level as well.
  • Basic (ballistic guidance) missiles (which are  cost 15,000 x TL 7 = 105,000 Cr for 14G or 225,000 Cr. for 30G. 
  • TL 12 Smart (internal guidance) missiles (which is what most PCs will get) cost 30,000 x 12 = 360K for a pack of 12 at 24G's. 
  • Nukes cost 45,000 x 7 = 315,000 Cr for a dozen, which is still pretty cheap. TL 15 cost 675K for 12. If anything, I think I'm undercharging for these. 
  • Missiles which are neither smart nor basic default to external guidance. See last week's post for more explanation on this. 
  • Long Range missiles... kind of cease to be relevant at this point. 
You get the idea. Yes, they're much more expensive than the 1e versions (but actually get surprisingly close to 2e prices), but they're also much faster, which means they are less likely to be shot down, and that makes them far more effective. 

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