Relativistic Weapons

[StephenT]

though even after 40 AU of acceleration it'd still be going fast enough to cause some serious damage I think?

Still not sure why you need to use an asteroid, though...

Take a typical Type 'S' scout/courier flown by a paranoid psychopathic lunatic (ie, a player character). Jump into deep space (*koff*) using half the fuel in your tank. That gives you six weeks of 2G acceleration, by which time you'll have reached 71 million metres per second, or 23% of c.

A Type S has a mass of 685 tons according to TNE. Its kinetic energy will be 1.81E21 J, which is 432 Gigatons of TNT.

The good news is, it will take the ship 23 hours to cross the distance from the orbit of Pluto to the Sun, so you have a bit of time to intercept it...

Now replace the Type S with a Tigress-class dreadnought.

 

[far-trader]

And what of the probability of hitting a micrometeroid or dust spec while clipping along at a respectable fraction of C somewhere along that path? (Unless you're coming in from above or below the planetary disc).

Not to mention of course, you will be spotted long before that and putting a simple screen of particles in your path (with no chance of you avoiding them) will obliterate you long before you are close to the target. Unless the target has no space presence, in which case what's it's military value?

Not that the psycho will care, but the Navy will.

 

[EDG]

Still not sure why you need to use an asteroid, though...

You don't really need to - they just have more mass on them though, which makes for a bigger impact.

Take a typical Type 'S' scout/courier flown by a paranoid psychopathic lunatic (ie, a player character). Jump into deep space (*koff*) using half the fuel in your tank. That gives you six weeks of 2G acceleration, by which time you'll have reached 71 million metres per second, or 23% of c.

A Type S has a mass of 685 tons according to TNE. Its kinetic energy will be 1.81E21 J, which is 432 Gigatons of TNT.

This again illustrates the most ludicrous part of (non-TNE) Traveller - that manoeuvre drives basically have limitless fuel. And that power plants use their fuel at a constant (low) rate. It seems crazy to me to be able to accelerate constantly at six weeks at 2G without any handicap to the ship. Surely there's got to be practical limits (e.g. the thruster plates would burn out after a certain time of constant burning).

The good news is, it will take the ship 23 hours to cross the distance from the orbit of Pluto to the Sun, so you have a bit of time to intercept it...

With what?? You'd have to have amazingly good targeting computers to be able to fire a weapon far enough in advance and on the exact right trajectory to intercept it.

 

[Court Jester]

You'd have to have amazingly good targeting computers to be able to fire a weapon far enough in advance and on the exact right trajectory to intercept it.

Maybe we do?

 

[far-trader]

You'd have to have amazingly good targeting computers to be able to fire a weapon far enough in advance and on the exact right trajectory to intercept it.

Maybe we do?

I think we could just litter the space ahead of the attacker with rounds from the Sandcasters and let the attackers own speed do him in as he grinds through the sandstorm. There's no way he can maneuver around it. It might even make a pretty spectacular fireworks show if we use different metals in the sand mix for different pretty colours as they vaporize

 

[Infojunky]

You'd have to have amazingly good targeting computers to be able to fire a weapon far enough in advance and on the exact right trajectory to intercept it.

Maybe we do?

Not by the rules set out in the Core book.....

 

[captainjack23]

Still not sure why you need to use an asteroid, though...

You don't really need to - they just have more mass on them though, which makes for a bigger impact.

Take a typical Type 'S' scout/courier flown by a paranoid psychopathic lunatic (ie, a player character). Jump into deep space (*koff*) using half the fuel in your tank. That gives you six weeks of 2G acceleration, by which time you'll have reached 71 million metres per second, or 23% of c.

A Type S has a mass of 685 tons according to TNE. Its kinetic energy will be 1.81E21 J, which is 432 Gigatons of TNT.

This again illustrates the most ludicrous part of (non-TNE) Traveller - that manoeuvre drives basically have limitless fuel. And that power plants use their fuel at a constant (low) rate. It seems crazy to me to be able to accelerate constantly at six weeks at 2G without any handicap to the ship. Surely there's got to be practical limits (e.g. the thruster plates would burn out after a certain time of constant burning).

CT, if I recall, not only had fairly large fuel requirements for the M drive/powerplant, but also had a limit of about 80 hours thrust....I think.

The good news is, it will take the ship 23 hours to cross the distance from the orbit of Pluto to the Sun, so you have a bit of time to intercept it...

With what?? You'd have to have amazingly good targeting computers to be able to fire a weapon far enough in advance and on the exact right trajectory to intercept it.

The issue isn't the targeting, that's easy enough now -with 23 hours and a TL or three, no prob....and I suspect any planet has some kind of interception system online at all times - the issue is what to intercept it with, and to what end.

Even at .25c, it's going to be really, really hard to deflect it, let alone stop it. The same mass/velocity moment which is hitting the planet is also present as inertia, after all. Even if you manage to vaporize it, it is still moving at .25c and would likely condense enough to just be a shotgun blast hitting the planet rather than a discreet object - and easily as dangerous- same mass, just spread out - same velocity, so even if only 10% of the original mass impacts the planet....poof. That V squared is a killer.....

 

[Court Jester]

You'd have to have amazingly good targeting computers to be able to fire a weapon far enough in advance and on the exact right trajectory to intercept it.

Maybe we do?

Not by the rules set out in the Core book.....

Pffft...

Why should I let something like that stop me... 8)

 

[far-trader]

...
CT, if I recall, not only had fairly large fuel requirements for the M drive/powerplant, but also had a limit of about 80 hours thrust....I think.

Yes to your recall of huge fuel requirements but I don't recall a limit. Unless one stretched the defined life support endurance as a limit, or interpreted the 4 weeks routine maneuver to be a maximum limit including half acceleration and half deceleration (so just 2 weeks at full Gs ). If you twig on where you might recall this from do post. (Could it have been the 1st printing of the LBBs?)

The only other possible interpretive limit I can think of is an implied one of one billion km from the typical travel times table in The Traveller Book, but I'm sure that's not the intent (though the 6g billion km trip is close to your 80 hours, it lists 2.9 days, half accelerating and half decelerating.

I've always been more inclined to go with the drive efficiency dropping off over distance, good for 100% to 100d but less the further out you get from a large gravity source.

 

[EDG]

CT, if I recall, not only had fairly large fuel requirements for the M drive/powerplant, but also had a limit of about 80 hours thrust....I think.

Not that I could find anywhere... source?

The issue isn't the targeting, that's easy enough now -with 23 hours and a TL or three, no prob....and I suspect any planet has some kind of interception system online at all times - the issue is what to intercept it with, and to what end.

Well I think you'd really just have to put something in the way (like a sandcaster field). Though that's another thing - if the rock is going that fast then it will be hitting interplanetary dust grains and slowly eroding away too.

But I'm just thinking that by the time you've locked on it, and then registered enough to fire on it... the rock's gone out of range. It's covering 150,000 km every second, and those combat rounds in space are six minutes long apiece (presumably because you can't lock on and fire that instantaneously). In a single space combat round the 0.5c rock has travelled 0.36 AU from where it was at the start of the round!

 

[captainjack23]

The main cause of the near-c pebble issue is one of those ill defined things: is the M drive a true reaction drive, a reactionless drive, and inertialess drive or a pseudovelocity drive.....

One could argue that since kinetic planetbusters aren't in common use, that the Mdrive must somehow operate without effecting inertia....pretty handwavy, I agree, but we have even odder things in traveller that seem okay.


I would have to guess that the whole way drive is modeled in traveller has more to do with wanting to avoid fuel calcs and all the consequenses of reaction drives used as weapons ...HEPLAR may look nice and hyper believable, but is equally capable of devastating whole planets, fleets etc. Plus IIRC it's moment of acceleration as prtesented in the rules was equally unbelievable for the real rocket science engineers.


I'm of the opinion that perhaps not defining this too closely is the best approach, as it allows a vast range of types of play (SFopera <-> HardSF) to be handled by the same rules...with those wanting more detail (or complex justification, really) able to add it on without breaking the frame, as it were.

 

[captainjack23]

CT, if I recall, not only had fairly large fuel requirements for the M drive/powerplant, but also had a limit of about 80 hours thrust....I think.

Not that I could find anywhere... source?

CT book 2 -combat rules. LBB version -also in ship construction. Do you even own them ?

The issue isn't the targeting, that's easy enough now -with 23 hours and a TL or three, no prob....and I suspect any planet has some kind of interception system online at all times - the issue is what to intercept it with, and to what end.

Well I think you'd really just have to put something in the way (like a sandcaster field). Though that's another thing - if the rock is going that fast then it will be hitting interplanetary dust grains and slowly eroding away too.

But I'm just thinking that by the time you've locked on it, and then registered enough to fire on it... the rock's gone out of range. It's covering 150,000 km every second, and those combat rounds in space are six minutes long apiece (presumably because you can't lock on and fire that instantaneously). In a single space combat round the 0.5c rock has travelled 0.36 AU from where it was at the start of the round!

Its called a course projection....something moving that fast with that much vector and no changes is easily projected...one simply needs to have an intercept plotted far enough ahead to be in its way. It's how we catch a ball, after all.

Regardless, the point still stands -what are you going to intercept it with that will do a damn bit of good ? Those 432 GT of kinetic impact energy are exactly what you are having to deal with; any amount of sand or cosmic debris will absorb some of the energy, true, but in utterly trival amounts - and it's not like it just goes away - it's an energy transfer, so some remnanant (probably as protons ) will continue on from the particles. So, even putting an asteroid in the way of a 50T pinnace isn't going to work. It's going to vaporize the asteroid and the impactor, possibly slow it down by, lets say half ? Which leaves the impact energy of the vapor (actually vapor as a euphemism for soft gamma rays, I think -) as a a mere 100GT ; and even if 90% is deflected as a result, 10 GT of impact energy ? Is that still a lot ? is 1 GT ?

Look up the blast stats for the Soviet "Tsar Bomba" test during the cold war - particularly as centered over London -engulfing most of the home counties. And that was a .05 GT blast. So, yes. Even 1 GT is a lot. It's probably a major extinction event.

About the only thing that would work is deflection - and THAT is where the time to target becomes crucial - and only then for lesser problems, such as the Alvarez impactor moving at merely orbital speeds.

At these levels ? The numbers are as hard to understand as the volume of a parsec.


edited to correct maths...which are hard...

 

[Infojunky]

Maybe we do?

Not by the rules set out in the Core book.....

Pffft...

Why should I let something like that stop me... 8)

Good....

 

[captainjack23]

Not by the rules set out in the Core book.....

Pffft...

Why should I let something like that stop me... 8)

Good....

Best !

 

[EDG]

CT book 2 -combat rules. LBB version -also in ship construction. Do you even own them ?

I do - I just ignore book 2. (this is one reason I make grognards come out in hives, because I reject books 1-3 in favour of later books that replace them). I checked High Guard but didn't find anything about M-drive fuel use (but I might have missed it there)

Its called a course projection....something moving that fast with that much vector and no changes is easily projected...one simply needs to have an intercept plotted far enough ahead to be in its way. It's how we catch a ball, after all.

Sure, but you're trying to plot the course of something Very Small from Very Far Away moving VERY Fast. Plus you have light-speed lag - at 0.5c, by the time you see the object, it isn't remotely where it was. Getting your weapon (or whatever) to hit it exactly when you've probably got a large margin of error as to where you think it might be when it gets within a few AU of you might be tricky (not impossible, but I think it'd be harder than just plotting out the orbit of a normal asteroid).

At these levels ? The numbers are as hard to understand as the volume of a parsec.

Pretty much! (though I think they're not so much "hard to understand" as "hard to visualise")

 

[captainjack23]

CT book 2 -combat rules. LBB version -also in ship construction. Do you even own them ?

I do - I just ignore book 2. (this is one reason I make grognards come out in hives, because I reject books 1-3 in favour of later books that replace them). I checked High Guard but didn't find anything about M-drive fuel use (but I might have missed it there)

Ah. That must make being a Canonista rather interesting, over and above all the hives you get to see....I guess.

In any case, it's in Book 2; something like the "M drive has sufficient fuel for 288 accelerations" Referring to 1000sec turns.

Its called a course projection....something moving that fast with that much vector and no changes is easily projected...one simply needs to have an intercept plotted far enough ahead to be in its way. It's how we catch a ball, after all.

Sure, but you're trying to plot the course of something Very Small from Very Far Away moving VERY Fast. Plus you have light-speed lag - at 0.5c, by the time you see the object, it isn't remotely where it was. Getting your weapon (or whatever) to hit it exactly when you've probably got a large margin of error as to where you think it might be when it gets within a few AU of you might be tricky (not impossible, but I think it'd be harder than just plotting out the orbit of a normal asteroid).

C lag matters not a whit for this; the time lag is the same for any object at the same distance, regardless of speed - for the observer. The trick is how long it takes for it to get to where its light went, as it were.

Granted you have to spot it in the first place.

Given that, you plot the course from two or three points. It's an utterly straight line at those speeds. Draw the line forward to the target - then back to the earliest intercept possible. Put whatever you want to use to stop it there.

The biggest problem is parallax - if it's coming right at you, you'll have a bit of a problem making the plot -but I assume that we have some other spotting platform in the hypothetical system one could hand off to.


Not, as I'm sure you agree, that it matters at all........

At these levels ? The numbers are as hard to understand as the volume of a parsec.

Pretty much! (though I think they're not so much "hard to understand" as "hard to visualise")

I dunno....the visual is easy:

"Make big boomy flash, planet go bye bye. "
8)

 

[far-trader]

...
In any case, it's in Book 2; something like the "M drive has sufficient fuel for 288 accelerations" Referring to 1000sec turns.

I think you missed my question back a page. Can you tell me is that the 1st printing (1977) version? And what page it's on if you can. Thanks.

 

[captainjack23]

If you twig on where you might recall this from do post. (Could it have been the 1st printing of the LBBs?)

Sorry, yes I did miss it.

Hmmm. Okay, here: LBB2, pg 6 possibly 1st print ? It's the one I've had since 1977 I'm pretty sure.

- it notes a minimum of 288 accelerations can be made on a full tank in miniatures combat - (I didn't remember the word minimum if that matters) - and combat turns are IIRC 10 min..... so 6/hour = 48 hours, actually.
I note also that the M drive in small craft uses 1 ton of fuel = 1 g acceleration for 1000 minutes. ( I forgot that, glad you had me look up the pg number )...so 20dt = 1g constant for 20,000 minutes or....300 hours ? okay, about two weeks for a 90 ton shuttle -and presumably similar for a type s (100T)

- It also may be in the big black book edition -I'm not sure, and I seem to recall that they actually reduced detail in lots of cases for the reprint.

Hope that helps.

 

[far-trader]

... Hope that helps.

Very much, thanks. And very interesting. Pretty sure that is 1st printing rules, and dropped in 2nd printing (for good or ill). I don't recall anything like it in The Traveller Book (and I've read it several times over the many years) so it looks like it wasn't brought back for it either.

 

[EDG]

Hmmm. Okay, here: LBB2, pg 6 possibly 1st print ? It's the one I've had since 1977 I'm pretty sure.

- it notes a minimum of 288 accelerations can be made on a full tank in miniatures combat - (I didn't remember the word minimum if that matters) - and combat turns are IIRC 10 min..... so 6/hour = 48 hours, actually.
I note also that the M drive in small craft uses 1 ton of fuel = 1 g acceleration for 1000 minutes. ( I forgot that, glad you had me look up the pg number )...so 20dt = 1g constant for 20,000 minutes or....300 hours ? okay, about two weeks for a 90 ton shuttle -and presumably similar for a type s (100T)

That's not mentioned at all in the 1981 edition that I have (at least, not on page 6). So I guess it got dropped between editions?

(now, which is proper canon, the rule that came first but got dropped later, or the rule that came later but stayed in? . Semi-serious question, because a lot of the canonistas treat "first publication" as higher priority... but the changes quietly made between CT printings screws that all up).