Relativistic Weapons

[aspqrz]

Actually ISTR that White Dwarf (?) or someone did a crossover adventure based on CoC and Traveller way back ... maybe even in the 3LBB days (which it would have to have been for WD to have been involved, if they were )

Are you thinking of The Last Log: A Call of Cthulhu Scenario set on a Distant Planet Far in the Future by Jon Sutherland, SDteve Williams and Tim Hall in White Dwarf #56? /quote]

Quite possibly. It was, as they say, "Long, long ago, in a Galaxy far, far away" :wink:

Not surprising my memory is like swiss cheese at this late date :lol:

Or, possibly, it's a Hiver plot on behalf of Shub-Internet? :shock:

(Thanks for jogging the rusty memories)

Phil

 

[Twi'lekk_Den-keeper]

I HAVE THE ANSWER!!! You people are working so hard to achieve "realism" (horribly overrated) that you've skipped a very important part of your argument. The Jump Torps/Planet destroying ships and astroids aren't as simple as you make them out to be. We are all spoiled by the intense NASA calculations that land us where we want to be on marz and the moon. Planets don't sit around- Theyre shooting around at thousands of miles per hour!!!! How the heck are you going to hit one of those suckers from 4ly away, not mentioning any longer distances. It would be like trying to shoot a ant in boston with a lazer in being- only a ton harder and without any (visible) obstacles!!!!

The only other thing that irks me is the melee combat with marines argument. AND, AGAIN, I HAVE THE ANSWER!!! I have sat thinking of what the traveller universe is missing, what possibilities have been over looked, and my roving eyes were caught by DUNE!!! :wink:
"Personal shields," remember? They would make a nice vibroblade quite usefull... And for those of you who don't want to massively change your traveller universes: Suck it up.

 

[EDG]

I HAVE THE ANSWER!!! You people are working so hard to achieve "realism" (horribly overrated) that you've skipped a very important part of your argument. The Jump Torps/Planet destroying ships and astroids aren't as simple as you make them out to be. We are all spoiled by the intense NASA calculations that land us where we want to be on marz and the moon. Planets don't sit around- Theyre shooting around at thousands of miles per hour!!!! How the heck are you going to hit one of those suckers from 4ly away, not mentioning any longer distances. It would be like trying to shoot a ant in boston with a lazer in being- only a ton harder and without any (visible) obstacles!!!!

Not that I'm arguing that J-torps make viable weapons, but there are these things called ephemerides... (which, if you don't know, are basically tables telling you exactly where a planet will be at a given time. They're relatively easy to compile, since planets tend to move in reasonably fixed orbits so their motions are quite predictable (OK, so they'll vary a bit over time given the influences of other planets, but in the short torm they're predictable). The ephemerides (tracked forward by a week of subjective time) for the target system can potentially be programmed into the J-Torp's avionics and away it goes. Of course you can only really do that if you know anything about the target system in the first place...

The point being, it's actually pretty easy to aim something at a planet, because they're pretty predictable.

 

[zozotroll]

And sort of big.

EDG, how much signature does a planet put out at 100D? If it is industrealized, it should have a huge bunch of emmisions. Currently we have no trouble at all building misles that can home in on them. What I dont know is how fast those signals degrade.

 

[EDG]

EDG, how much signature does a planet put out at 100D? If it is industrealized, it should have a huge bunch of emmisions. Currently we have no trouble at all building misles that can home in on them. What I dont know is how fast those signals degrade.

At 100D from the planet? If it's technologically advanced and using radio then it'd be putting out all sorts of signals that can be potentially detectable (if you're looking on the right radio frequencies). But it depends on the strength of the signals, the planet's ionosphere, any solar flares going on at the time, etc...

That said it all depends on what you're looking with.

 

[Jeff Hopper]

Here's a question, has anyone ever figured out exactly what would happen if a say a 200 ton ship travelling at Near-C actually did hit a world?

I know it would be catastrophic, but what would that catastrophy look like?

 

[EDG]

Well, assuming the ship has a mass of 200 metric tons (200,000 kg), and is moving at say 0.5c (150,000,000 m/s) then the total energy released is the kinetic energy that it has at impact (1/2 mv²).

So that's 2.21e21 Joules. One megaton of TNT is 4.184e15 J, so we're looking at an explosion with an equivalent of about 500,000 Megatons of TNT (!!).

 

[far-trader]

Or pick your scenario and plug the info in here:

http://www.lpl.arizona.edu/impacteffects/

 

[rust]

Thank you very much for this link !

I have just calculated the impact of a minor moon on my setting's main
world, an event I had put into the timeline, and it turned out that I will
have to increase the size of the seafloor crater quite a bit, although the
impact would have done surprisingly few damage to the planet other-
wise.

 

[far-trader]

You're welcome rust.

But apparently it won't answer Jeff's question after all It won't do huge velocities. It's only designed for natural impact velocities of solar system objects I guess.

 

[lastbesthope]

@rust

It's not just the direct impact is the issue, earthquakes, tsunamis and dust kick up would be damaging medium to long term.

@far-trader, I plugged in well in excess of 0.9c and it gave me answers.

LBH

 

[far-trader]

@far-trader, I plugged in well in excess of 0.9c and it gave me answers.

LBH

Ah, I see now, I goofed on the decimals Thanks for the help LBH.

 

[far-trader]

Interesting. Not nearly as devastating as I'd thought, if I'm putting the right numbers in now and the program can make decent predictions based on such extremes. Pretty much a Tunguska event for any of the smaller starships* travelling at 0.5C with the atmosphere preventing much direct damage.

Either the whole C-rocks thing is after all a moot point (too little damage for the investment, at least for a world with a standard atmo) or we're gonna have to use a bigger ship

* I plugged in the 30m diameter Merc Cruiser with various densities.

 

[rust]

It's not just the direct impact is the issue, earthquakes, tsunamis and dust kick up would be damaging medium to long term.

Yep, I know, but the impact happened long ago, the crater (now of the
right size) is the only major trace left of the impact.

 

[lastbesthope]

Sorry rust, I missed the part where you said it was a historical event in your timeline.

LBH

 

[rust]

Sorry rust ...

No problem, I should have been a bit clearer about the timeframe.

 

[EDG]

@far-trader, I plugged in well in excess of 0.9c and it gave me answers.

They're almost certanly not the right answers though. far-trader was right in his first assessment - these calculators aren't designed for such ridiculous velocities as a sizeable fraction of the speed of light, because that's well beyond the bounds of any research on the subject (no impactor will ever be travelling that fast).

You can expect reasonably accurate answers for a few tens of km/s, but not beyond that because there's all sorts of other effects that aren't being considered for things travelling faster (like the fact that the body is going so fast that it doesn't even have a chance to register that there's an atmosphere to break up in before it slams into the ground. And I'm sure that there's all sorts of horrible effects caused by suddenly stopping a mass going at relativistic speed - even at half the speed of light that's fast enough for the object to travel through the entire planet in less than a tenth of a second!).

EDIT: To clarify, at the very least you'll get the entire kinetic energy of the impactor converted to heat (so that's 500 gigatons of TNT equivalent for our 200 ton ship travelling at 0.5c. Though I guess the mass of the impactor would be increased by relativistic effects too...). But everything else - the shockwave, size and depth of the impact crater, etc - would be way off the scale. We're probably talking about something that will melt the entire crust of the planet and destroy all life on it though.

 

[Twi'lekk_Den-keeper]

I've put in my impact velocity severeral times, and the web site wont accept it. What "decimals" are being goofed up? (what number should I put in for 1c?)

 

[EDG]

I've put in my impact velocity severeral times, and the web site wont accept it. What "decimals" are being goofed up? (what number should I put in for 1c?)

299,000 km/s is close enough for lightspeed.

 

[far-trader]

I've put in my impact velocity severeral times, and the web site wont accept it. What "decimals" are being goofed up? (what number should I put in for 1c?)

Well the "decimals" I was messing up was putting in m/s instead of the km/s they wanted (huge difference). And no, the site won't accept 300,000km/s either. I guess whoever wrote it put in a lightspeed limit It will do sub-C though. I used .9 = 270,000km/s

But as EDG notes the results are suspect.