Traveller Missiles -- a Peeve

[manley_t]

The problem I have with Traveller Missiles

Each missile has a mass of 1/2 a ton, or 1,000kg and accelerates at 6G and carries a warhead that does 5D6 of starship damage.

Now, 6G comes out to be 58.8399m/(sec^2) (1 G = 9.80665)

Following F=ma we get (simply) that our high-tech 6G micro-maneuver drive can produce (f=newtons, m=kilograms and a=meters per sec^2)

f=ma
f=1000x58.8399
f=58839.9 Newton/kilogram

*ONLY* 58.9kN!

This is ridiculous IMO -- since the venerable Tech6 rocket, the RL-10***, that acted as booster in the Apollo Missions, has a thrust rating of 66.70kN and itself weighs in at 131 kg. This give a thrust rating a little better than our high tech engine, but basically the same.

Now, I know that the big difference is that the older rockets had a burn time based on their specific impulse -- and that their acceleration would increase over-time as their mass decreased until they reached burn-out at which point they would coast.

But while this old ancient TL6 rocket had a specific impulse (Isp) of just over 400sec we have even new rockets with superior Isp ratings. Not to mention nuclear or fusion rockets, which have Isp ratings that are incredible.

What's my point?

I think the 6G limit is just fine on ships that are operated by humans; using the accelerative forces and grav-plate tech limitations to explain away the barrier. But, in unmanned vehicles I find it too much a suspension of disbelief.

Why would I want to have missiles that are slow and clunky at TL 15 when I can have finely tuned Fusion-Plasma rockets with Isp ratings that are incredible and thrust ratings capable of reaching hundreds and thousands of Newton/kilograms.

I've made some arbitrary 'guesses' as to what I think the standard missiles component size breakdown is:

Engine
Avionics (including sensor package and guidance control)
fuel
warhead

In a 1,000kg missile I have the following breakdown:
Engine mass -- 50.00Kg
Avionics mass -- 100.00Kg
fuel mass -- 50.00Kg
warhead mass -- 800.00Kg

based on these percentages I came up with this warhead damage rating chart using just a % incraease or decrease in mass:
damage wearhead
13d6 2,000Kg
9d6 1,500Kg
8d6 1,200Kg
6d6 1,000Kg
6d6 900Kg
5d6 800Kg
4d6 700Kg
4d6 600Kg
3d6 500Kg
3d6 400Kg
1d6 200Kg
1d6 100Kg

and here's a comparison chart between the two (traveler missile and RL-10) -- {MMD stands for Micro Maneuver Drive}

........Trav Normal RL-10
mass 1,000.00Kg 1,000.00Kg
Eng Mass 50.00Kg 131.00Kg
Avionics 100.00Kg 100.00Kg
Fuel 50.00Kg 169.00Kg
Warhead 800.00Kg 600.00Kg
Dmg 5d6 5d6
Thrust 6.0G 6.0G

But, that's using a 1960 rocket!

My plan (when I'm at home and have time this holiday) is to use the vehicle creation rules to create missiles and come up with rule-book standard components for missiles. I'll use the gravatics propulsion and I think that I'll easily exceed 6m/sec^2

Also -- my thoughts are why stick with a single missile? Why not create Torpedoes? Have space-fighters with large torpedoes strapped to their hull and fired not too dissimilar to the way ww2 aircraft worked nor too dissimilar to the way today's aircraft work.

we'll see what I can generate using the rules and I'll post what I come up with



footnote---

***
RL-10
***
Designer: Pratt and Whitney. Used on stages: Nova A-3, Nova B-3, Saturn IV. Used on launch vehicles: Nova A, Nova B, Saturn B-1, Saturn C-2, Saturn C-3, Saturn I. Propellants: Lox/LH2 Thrust(vac): 6,804 kgf. Thrust(vac): 66.70 kN. Isp: 410 sec. Isp (sea level): 10 sec. Burn time: 482 sec. Mass Engine: 131 kg. Diameter: 0.9 m. Chambers: 1. Chamber Pressure: 24.00 bar. Area Ratio: 40.00. Thrust to Weight Ratio: 44.63. Country: USA. Status: Out of Production. First Flight: 1961. Last Flight: 1965. Flown: 60

 

[BigBadRon]

Just one comment on the math. 1/2 ton is 500kg, not 1000kg. Which makes the drives even more underpowered I guess.

 

[tjoneslo]

Interesting. Except the missiles are 50kg, not 500kg or 1000kg. And it can accelerate at 6G for 2 hours.

Special Supplement 3: Missiles in Traveller published in JTAS 21 was a design system for CT missiles. This system gives a standard warhead weighs 10kg, control systems weigh 5kg (Controller, radio reciever, command detonator), leaving 35kg for the missile motor. Using a discretionary burn missile with a 6G motor takes 16 kg, leaving 19kg of fuel.

http://www.strout.net/info/science/delta-v/intro.html

According to this calculator, in order to achive the 423,000 m/s delta-v, the engine has to have an ISP of 885,000. Which is a fair chunk more efficient than any of the rockets on this list:
http://www.wikipedia.org/wiki/Spacecraft_propulsion

 

[manley_t]

memory told me missiles were 1/2ton for some reason -- coulnd't find it in teh book though; but in some other stuff yep, they're 0.05 tons > 50kg. -- *doh*

course this makes the engine even worse; it's thrust turns out to be 300 Newtons, which, with all due respect, has nothing on modern rockets (RL-10 from example is 6670 Newtons).

I'm afraid I've no knowledge of the design-set you speak of; I only have the books I've read to work from; and for T20 have been working exclusively from the player's handbook.

T20 HB page 178 says that once launched a missile will only move for 6 rounds. And, according to Page 176, each tactial plot round is 1 minute -- which means that the standard missile has an Isp of 360 -- which is waaaay worse than the 420 that our discontinued RL-10 rocket has.

Of course, the RL-10 is now not far from 3 times the size of the standard Traveller missile But that was way back in 1960....

I still plan on working up the missile using the vehicle design rules. Since we don't have any rules in the T20 handbook (that I can see) telling what size the warhead is I'll build it per rules and have whatever is left over as the standard 5d6 warhead.

 

[manley_t]

Hmmm...interesting

First run creating a missile as a vehicle comes out to:

standard missile
70vl chassis
1 gravitic thruster: -4vl Cr46,000 -1EP
1 std batteries: -1vl Cr0.25
long range radar: -20vl MCr1 -1EP
Warhead would be what is left over, which is 45vl.

Some interesting specifics on this.
The cost is Cr1,046,093 (as opposed to the book, which shows Cr5,000 per missile)
Thrust comes out to 1111kph, which is 30.8G.

The battery stores 1EP-hour -- but the power requirements of the missile (since it only lives for 6 minutes) are 0.2EP -- thust plenty of power for both the engine and the radar.

This design even has 0.9vl left over (technician finger-space)...

Of course, this gives you 31G for a duration of 6 minutes (course the battery provides enough life for 1/2 an hour for both systems).

Also this 50kg missile breaks down:
2.9kg for the Gravatic thruster
.07kg for the battery
14kg for the radar
32kg for the warhead

Oh, found the darn chart showing missiles size and cost....don't know how I missed the darn thing....

comments?

 

[DaveShayne]

Originally posted by Big Tim:
Of course, this gives you 31G for a duration of 6 minutes (course the battery provides enough life for 1/2 an hour for both systems).

You are of course free to do whatever you want in YTU but for my money misiles pushing more than 6 Gs just isn't Traveller.

 

[Falkayn]

Perhaps this is too obvious ... but how about "the vehicle/starship design rules aren't made to design missiles"?

Missiles must have a MUCH greater thrust than 6G because they can cross phenomenal distances between starships in one turn of game time.

 

[Ellros]

Also this 50kg missile breaks down:
2.9kg for the Gravatic thruster
.07kg for the battery
14kg for the radar
32kg for the warhead

Based on the explosives chart for amount of explosive required to breach a Starship hull, 32kg would cause a nice bang. Chart says 8kg are required just to penetrate.

 

[shield]

Missiles being 1/2tn displacement comes from the TNE rules.

As for missile speed, yes they should be able to overtake ships (which will be making 6G). The Annic Nova adventure had missiles/drones that could make 12G (from memory) so that sort of makes it canon.

There have been quite a lot of posts on the TNE mailing list about missile speeds. Using the TNE Heplar engine, it is possible to get a missile that makes about 48G, for several hours and does not really need a warhead, the damn thing is going so fast that the missile casing/engine itself does the damage by pure kinetic energy.

Basically with these things, if you penertrated the anti missile fire, the missile would turn just about anyship into a fireball. And at these sort of speeds, it was difficult for commercial ships with basic sensors and standard laser turrets to stop them. It sparked a burst of specialised very high ROF anti-missile laser batteries.

 

[graden1]

Originally posted by Big Tim:
T20 HB page 178 says that once launched a missile will only move for 6 rounds. And, according to Page 176, each tactial plot round is 1 minute -- which means that the standard missile has an Isp of 360 -- which is waaaay worse than the 420 that our discontinued RL-10 rocket has.

I think that's supposed to be 6 strategic rounds, which are twenty minutes each, which is (guess what!) 2 hours. This isn't a serious problem; I think that raises the ISP to 7200. That might be too high for a chemical rocket engine; I'll have to check the math later.

My own peeve is that the advanced space combat rules state these missiles accelerate at only 6g, which seems rather feeble to me, even for Traveller.

Thanx heaps,

DGv2.0

 

[Murph]

Uncle Bob and I once calulated that the average Traveller turret missile was equal to a TOW or Hellfire missile, not a Standard or one of the big Russian jobs. Small anti-tank missile equivalents.

 

[tjoneslo]

Of course I come out with different answers than you do....

Originally posted by Big Tim:
Hmmm...interesting

First run creating a missile as a vehicle comes out to:

{Sniped designs}

Thrust comes out to 1111kph, which is 30.8G.

How did you calculate this?

According to my calculations (and rule readings), the standard acceleration of a vehicle is 1/10 of the top speed in kph/min and maximum acceleration is standard x agility. 1 kph/min translates (if my math is correct) to 1/216 m/s^2. (Yes the accelerations of T20 vehicles are pathetic). So in order to get a 6G craft, you need an agility 4 craft with a top speed of 31,752kph. Or 21,168kph for an agility 6 craft (using a jet engine to mimic a rocket engine). Neither engine will fit into any vehicle.

 

[Uncle Bob]

*sigh*

OK, let us assume 460 sec (1990s H2-O2) rockets, with 90% fuel. (10% for warhead, guidance, structure) That gives a maximum delta-V of 10.4 KPS.
That would be about 1000 seconds at 1G, but less than three minutes at 6 G (50% fuel will only last 319 seconds at 1 G or less than a minute at 6 G).

Chemical rockets cannot be used for star-ship combat. The (conceptual, TL 9?) "nuclear salt" water rocket (plutonium pu239 salts dissolved in water) has an exhaust velocity of 66,000 m/s, so a 50% fuel load could maintain 1G fr 77 minutes or 6 G for less than 13 minutes. That still isn't good enough for Traveller combat.
So real-world rockets, even advanced designs, are not a good model

My own pet peeve is the way Traveller ignores the KE of missiles. A 50 Kg missile accellerating at 4 G for twenty minutes has 55 Gigajoules of kinetic energy. That is the same as twelve metric tons of TNT (9 tons of semtex ar C4). That kinda makes a 20 Kg chemical warhead insignificant.

 

[apoc527]

GURPS Traveller took care of the KE of missiles. They hurt...really, really bad.

I'll have to look at the accelerations for my GURPS Trav missiles. I have a feeling they are higher than 6 G, but I'll have to look. Of course, I come from the David Weber tech school, so any missile accelerating at less than 90,000 G's is wussy.

 

[manley_t]

My point really wasn't the specific impulse capability of modern rockets and how they could compete with the micro-maneuver drives on traveller missiles -- just the thrust capabilities don't match. And even that was to make an example of how I think (and it seems many agree) that the 6G limitation of traveller missiles are inadequate.

There are so many different design rules scattered about the different Traveller game versions that it would be nice to have the Traveller game modularized somewhat.

What I mean by that is to have a set of design rules that are Canon and replace all others. These can exist regardless of what rule-system players use as I don't really see any connection to how characters are generated and controlled and how starships are disigned and operated.

When FF&S came out I thought that might be this end-all be-all design system. But even it had some issues and ended up being scrapped as newer game versions re-invted the wheel so to speak.

I guess this is my "what I want in T5" speech....

oh well, IMTU I'm donig what I want...always have, always will.

Personally, I don't like the 'magical' floating space-ship. I don't mind the gravatic thruster plate concept...but I still think it's a thrust mechanicsm and not a 'gravity bubble' thing ala star trek.

But I like grittiness in my space-gaming, where players have to worry about silly things like gravity, radiation and air. To me that is what space-gaming should be about. Not the space-opera star trek stuff...unless that's what we're playing. Then space travel is just the mechanism to get the story forward instead of being part of the story.

Of course, this is related to how I like to run my post holocaust games...where survival *is* the game and things like clean food and water are as big a deal as how many bullets you have.....

I've been called the rated X graphic novel kind of GM before. Where realism is part of what makes the game fun.

Heck, I even have a modified house-rules version of traveller that uses the Phoenix Command Combat System. Space combat in that game was bascially "he who sees the target first wins".

Which, lets face it, is what space combat will really be like.

or at least that's what I think....

 

[julianlove]

There is definately a need for a missile design system of some sort. After all, do we really think that 20,000 dTon cruisers costing MCr10,000 or more are going to be throwing 50kg missiles costing Cr5,000 at each other? No, I don't think so either.

I rather liked the missiles in TNE/FFS - they were large (7,000kg and 0.5 dTons)and expensive (Mcr1 or so) because they were nuclear detonation lasers. Quite rightly, in my opinion, the designers believed that an impact missile of any sort, explosive or KE, was unfeasible beacause any laser capable of hitting a maneuvering starship at 300,000km could easily blow a missle out of the sky at 300km. So det nukes were the only missiles that made sense...they inflicted damage while still being 30,000km away, before a point defence laser had a near certain shot.

I also rather like the game balance implications of this. Missiles that are large and expensive mean that not every Tom, Dick and Harry is going to mount a triple missile rack on his Free Trader and be able to blow a Patrol Cruiser out of the sky. By all means use 50kg missiles for attacking lightly armed merchants, but warships are going to pack a real punch.

Missiles: large and expensive please!

 

[sinbadsam]

Well the missile debate has been done elsewhere... but the high points are....Point Defense Lasers are optimized for antimissile defense. That means that are designed to take out missiles not warships.

PD lasers can and will be saturated by incoming missiles/targets. If all of the incoming missiles are Nuke Dets then the PD Laser can be specifically designed for that fact. But if the incoming missiles are a mix of Nuke Dets Lasers, KKM, and Nuke Bursts the PD laser will have a harder time deciding which has to be engaged first. That delay in deciding which has to engaged first can/will be lethal.

You might check out my signature the Bubba and Little Bubba were missile submunitions carriers. The amount of Nukes and KKM carried were staggering. They were both armored to large degree.

FYI I was Surface Missile Firecontrolman in the USN. I worked on<G> the NATO SeaSparrow, Harpoon, CIWS, MK 86 GFCS, Whirly One and Slick 32 Electronic Warfare Systems, TAS Radar System, and Certified Sonar Dome Diver.

 

[Liam Devlin]

The mixed warhead selection stupefied my PC's in my test run war between Solee and the "Reformed Coalition"..
for while they had AI-Virus manning their MFD's, and co-ordinating anti missile fire, I had my Soleeans utilize the mixed loads (as they had mixed TL stuff, they had to) of missiles. KKM's, proximity nukes, and recovered Nuke det lasers-overwhelmed their MFD's decison making.
(being a lower tech Soleean Navy than some give credit for IMTU, they opted for the bay missile offense, as a more cost effective long range weapon than expensive N-PAWs or relic meson guns).

Needless to say, The RC learned a real painful & expensive lesson in that battle.(pyrrhic mean anything ?Uh huh!)

 

[Anthony]

The only real way to handle the KE of missiles, while leaving canon missiles coherent, is to assume that there's something weird about traveller manuever drives, such that missiles don't really have all that much KE. This is a little tricky to do; basically, it means that the traveller manuever drive is actually mostly a form of sublight warp drive (possibly a relative of the alcubierre warp drive, possibly more like 2300AD stutterwarp, possibly something else), not an actual form of acceleration. You need some ability to accelerate in order to match speeds for docking purposes, but the requirements are fairly modest. This is also a solution for the near-C rock problem, not to mention various forms of perpetual motion machine that are viable with the standard rules.

Coming up with specific rules for how the manuever drive actually works, that aren't easily abused, requires more text than reasonly fits on this board. The issue was hashed over a while back on the TML.

 

[Bruce]

What if the missles are actually bomb pumped laser heads like out of honor harrington? The actual ballistic part does not strike the ship.
Well at least not often.
The missles reach a range, detonate and slice through the ship with the laser.

That might make it make more sense.

Bruce
The Man Behind the Curtain