Canonically, M-Drives don't work past 1000 diameters. (See T4 & FF&S2)
Marc seems to waffle a bit on this, but it's a reasonably good limiter to the destructiveness.
Crashing ships as weapons
- Thread starter Adam Dray
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Canonically, M-Drives don't work past 1000 diameters. (See T4 & FF&S2)
Marc seems to waffle a bit on this, but it's a reasonably good limiter to the destructiveness.
Found this online (Yahoo Answers) for 1G:
0.0c to 0.1c = 35.4 days
0.1c to 0.2c = 35.6
0.2c to 0.3c = 36.2
0.3c to 0.4c = 37.1
0.4c to 0.5c = 38.7
0.5c to 0.6c = 40.9
0.6c to 0.7c = 44.3
0.7c to 0.8c = 49.6
0.8c to 0.9c = 59.1
That's the number of days for each .1c segment, so the total is 377 days for the entire trip. It seems you could NOT reach 0.9c at 1G within solar distances (say, 50 AU (416 light minutes, just under 7 light hours), though Jupiter is only at average 5.2 AU (43.2 light minutes).
At 6G, you'd fare better, I think, but I too do not want to do the math.
I imagine that if you hard-vectored on an intercept course for a planet, people might be okay until you hit the midway point. If you didn't spin and max delta-v, that's when defense systems would realize your intention.
Also, any ship on a full intercept burn toward a planet would be detected very early (days? weeks?) and have interceptors launched, just in case.
kilemall
SOC-14 5K
I think he means zero vector to either initiate jump or coming out of jump, so someone could not do a .9c run then jump and come out 100D away at full speed.
Is there any guarantee the ship will actually be pointed right at the planet on exiting jump? If it isn't, 100D isn't much space to swerve at 0.9C.
More or less, but on ships (or space stations) and thought to intercept the incoming ship as far away as possible.
Not necessarily, unmoving rocks will also serve (if you can make the ship collide against them. It's the ship's speed that makes the impact at relativistic speed.
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Are we porting that retroactively into CT and the other versions? Might be a good idea.
0.1c, call it 30,000 kps, mass of a free trader at ... let's go with 2000 tons loaded. 9x1020 joules. Roughly a hundred times the energy that would be released by a catastrophic eruption of the Yosemite supervolcano, depending on the estimate used for that. This guy ...
http://www.madsci.org/posts/archives/mar2002/1015040902.Es.r.html
..figures about 9 gigajoules per cubic meter to vaporize crustal rock, with a rather wide margin of error because rock deeper down is under pressure and so forth. Convenient number for this purpose.
So, 1x1011 cubic meters of rock go poof. That's a cubic block a kilometer on either side and a hundred kilometers deep. Don't know how that casts as an impact crater, but it looks like the impactor hits the mantle, probably goes some way into it. Probably cracks it.
So, what do we have? Well, planetwide earthquakes of unimagined severity. An impact site that behaves rather like the detonation of a very big supervolcano, and an area the size of a continent devastated around it. A planet-ringing cloud of dust that blocks light and pretty much wipes out the planetary ecology. Debris thrown up and reentering on the other side of the planet as a shower of massive meteors. Basically a dinosaur-killer event that would flatten most structures planetwide, destroy agriculture, and trigger a little ice age. Those not killed immediately by the impact or the earthquakes and tsunamis would die from cold and hunger. You might save some with heroic effort, but this world is no longer part of the Imperial economy.
You don't really need to get too terribly close to C to destroy a world's population.
With a 1000 diameter limitation, you can still game it to accelerate as many times as you have jump fuel for 2000 diameters each pass.
Simply you start accelerating at the 1000 diameter (which is a radius, by the way) limit and you have 2000 diameters of distance to accelerate. By 1000 diameter limit, you clearly use the diameter of a star.
Once you've passed the limit, you jump.
Jump retains the vector, so you just jump back to beginning of the 2000 diameter run limit.
You do this several times. The final jump puts the ship on a course for the target, and it accelerates for the entire trip.
This is more exciting if you have a particularly large star within jump range of your target.
Sure, this'll take a few weeks to pull off, but, hey, you're either committed or you're not.
No time to do the math on how fast a 6G drive can get you going. Note you get less acceleration with each pass, since your speed is up and you're in the window of applicability for less time.
Simply you start accelerating at the 1000 diameter (which is a radius, by the way) limit and you have 2000 diameters of distance to accelerate. By 1000 diameter limit, you clearly use the diameter of a star.
Once you've passed the limit, you jump.
Jump retains the vector, so you just jump back to beginning of the 2000 diameter run limit.
You do this several times. The final jump puts the ship on a course for the target, and it accelerates for the entire trip.
This is more exciting if you have a particularly large star within jump range of your target.
Sure, this'll take a few weeks to pull off, but, hey, you're either committed or you're not.
No time to do the math on how fast a 6G drive can get you going. Note you get less acceleration with each pass, since your speed is up and you're in the window of applicability for less time.
pendragonman
Absent Friends Margrave
Then there is a bit from the railgun thread that is relevant-ish. If the railgun round would become a plasma ball at around 0.5C, why, how would a ship survive at greater than that without more magic to defend it?
Condottiere
SOC-14 5K
We'll probably have to apply some form pseudo physics for an early warning system.
You have to take it as a given that high population high technology worlds have safeguards against this event.
You have to take it as a given that high population high technology worlds have safeguards against this event.
How do we stop it? A dedicated terrorist is going to move elsewhere and then jump to target. Might miss - most likely he'll miss, there's a lot of uncertainty in jump time, he might not come in pointed perfectly at his target, and he's got maybe 30 seconds or less to correct course. He can take more time, settle for a slower speed and less damage - 0.01 c still gives it as much punch as a supervolcano, maybe not enough to kill everyone, but enough to make a wreck of the agricultural sector, devastate the planetary economy. Still very likely to miss.
Now imagine the reaction of the population at a free trader flying by at 30,000 or even 3000 kps in a near miss. Fail once. Fail twice. Fail a hundred times - but everyone knows if they keep trying, they'll eventually get lucky, and all it takes to keep trying is an effective piracy campaign to keep grabbing ships to use. The terrorists don't need to hit to create terror.
1000 diameters is about 10 million klicks for an earthlike world. If you're assuming the local sun exerts the same influence, it doesn't change much: could be a hundred million clicks for a smallish star, a billion and more for a more sunlike star. Leaves you coasting for much of the trip to the gas giant in a lot of systems - and in serious trouble if some suicidal pilot decides he just wants to deep space the ship and die out there with everyone else aboard. Pray that your drive doesn't fail on the outbound leg - or that you can get it fixed or get a rescue out before you leave the 1000 diameter mark, or you'll be coasting till your now-cometary orbit brings you around and back into the system. Or maybe forever, if you've hit the system's escape velocity.
Still, it's plenty of room for a run-up if you choose an isolated system. A hundred million clicks gives you about 40 hours at 1G before you run out of the grav field, somewhat less since you're not wanting to get too close, but larger stars give you more room. 40 hours gets you up to 1400 kps, close to 0.005 c, not a planet-killer but enough to wreck civilizations. Bigger stars give you more running room.
Ultimately the only way to prevent disaster is to create a physics in the game that makes it impossible. Maybe there's a top speed for jump initiation: something in the interaction of regular space and jump space prevents the formation of a jump field when your velocity relative to the most dominant local gravity source exceeds a certainly value.
Now imagine the reaction of the population at a free trader flying by at 30,000 or even 3000 kps in a near miss. Fail once. Fail twice. Fail a hundred times - but everyone knows if they keep trying, they'll eventually get lucky, and all it takes to keep trying is an effective piracy campaign to keep grabbing ships to use. The terrorists don't need to hit to create terror.
1000 diameters is about 10 million klicks for an earthlike world. If you're assuming the local sun exerts the same influence, it doesn't change much: could be a hundred million clicks for a smallish star, a billion and more for a more sunlike star. Leaves you coasting for much of the trip to the gas giant in a lot of systems - and in serious trouble if some suicidal pilot decides he just wants to deep space the ship and die out there with everyone else aboard. Pray that your drive doesn't fail on the outbound leg - or that you can get it fixed or get a rescue out before you leave the 1000 diameter mark, or you'll be coasting till your now-cometary orbit brings you around and back into the system. Or maybe forever, if you've hit the system's escape velocity.
Still, it's plenty of room for a run-up if you choose an isolated system. A hundred million clicks gives you about 40 hours at 1G before you run out of the grav field, somewhat less since you're not wanting to get too close, but larger stars give you more room. 40 hours gets you up to 1400 kps, close to 0.005 c, not a planet-killer but enough to wreck civilizations. Bigger stars give you more running room.
Ultimately the only way to prevent disaster is to create a physics in the game that makes it impossible. Maybe there's a top speed for jump initiation: something in the interaction of regular space and jump space prevents the formation of a jump field when your velocity relative to the most dominant local gravity source exceeds a certainly value.
kilemall
SOC-14 5K
Actually, it's worse for the kamikaze starship pilot if he's getting relativistic- remember, if he is experiencing time dilation, he has less 'time' to react, and certainly it should be worse to try and shoot down incoming missiles.
CT Beltstrike EXPLICITLY gives us particle shielding fields as part of M-Drives.
Here is where fuel needs take effect. How many jumps you may do? what about PP fuel?
And I don't believe you can refuel in the meanwhile...
Timerover51
SOC-14 5K
A few thoughts here.
First, the Traveller dTon is a measurement of volume, not of mass. A 1000 dTon ship may easily mass more than 1000 metric tons, probably more like between 2000 to 3000 metric tons, unless it is armored, in which case it is going be weight quite a bit more. That is the mass that needs to be accelerated.
Second, if you are using fusion reaction drives, you are running into problems with the rocket equation, Final Velocity = Exhaust Velocity times (initial mass divided by final mass) to the Base E. https://spaceflightsystems.grc.nasa.gov/education/rocket/rktpow.html
Assuming the ratio of your initial mass to final mass is 9 or there about, you will get a final velocity of about 2 times the exhaust velocity, which if I remember correctly from Maxwell Hunter's Thrust into Space, will be somewhere between 3.1 and 4 Million Feet per Second, or somewhere in the vicinity of 1500 miles per second. That is well short of 0.9 C, not even 1 per cent of C.
Third, if you assume a reactionless maneuver drive run from your power plant, then you are looking at how do you handle all of the heat that the power plant is going to generate. You also have the problem of carrying enough fuel to achieve a decent percentage of the speed of light. Complete fusion of 57 grams of Deuterium will give you about 3 kiloton equivalents of energy. Fifty-seven kilograms of Deuterium will give you 3 Megaton equivalents of energy. Fifty-seven Metric Tons of Deuterium will give you 3 Gigaton equivalents of energy. That does assume that your power plant and maneuver drive is 100% efficient at using the fusion energy. If it is only 99% efficient, then you have around 30 Megatons of energy to deal with and get rid off, from your ship's power plant and maneuver drive. For comparison, that is twice the energy of the largest US nuclear test, the Castle Bravo shot of 15 Megatons.
The idea of throwing rocks as nuclear weapon equivalents is featured in Heinlein's The Moon is a Harsh Mistress, but I think that his 100 ton rocks were only about the equivalent of 10 kilotons or so. I am relying on my memory for that, so I could be off, but the rocks were relying on Earth's gravity well to supply a large portion of the velocity, not the rock thrower.
Note, the following is the energy equivalent of 1 Kiloton of TNT. It is taken from The Effects of Nuclear Weapons-1977 Edition. You can download it at archive.org to check my figures.
Complete fission of 0.057 kg (57 grams or 2 ounces) fissionable material
Fission of 1.45 x 10 to the 25 nuclei
10 to the 12 calories
2.6 x 10 to the 25 million electron volts
4.48 x 10 to the 19 ergs (4.18 x 10 to the 12 joules)
1.16 x 10 to the 6 kilowatt-hours
3.97 x 10 to the 9 British thermal units
Since a Kiloton is equal to 1.16 Million Kilowatt-hours, a Gigaton is going to be the equivalent of 1.16 Trillion Kilowatt-hours. For those used to metric units, a British Thermal Unit is the amount of energy needed to raise the temperature of 1 pound of water 1 degree Fahrenheit. One kiloton of energy will raise the temperature of 3.97 Billion Pounds of Water by 1 degree Fahrenheit. A Megaton will raise the temperature of that much water by One Thousand Degrees Fahrenheit. That is the heat load you have to deal with.
First, the Traveller dTon is a measurement of volume, not of mass. A 1000 dTon ship may easily mass more than 1000 metric tons, probably more like between 2000 to 3000 metric tons, unless it is armored, in which case it is going be weight quite a bit more. That is the mass that needs to be accelerated.
Second, if you are using fusion reaction drives, you are running into problems with the rocket equation, Final Velocity = Exhaust Velocity times (initial mass divided by final mass) to the Base E. https://spaceflightsystems.grc.nasa.gov/education/rocket/rktpow.html
Assuming the ratio of your initial mass to final mass is 9 or there about, you will get a final velocity of about 2 times the exhaust velocity, which if I remember correctly from Maxwell Hunter's Thrust into Space, will be somewhere between 3.1 and 4 Million Feet per Second, or somewhere in the vicinity of 1500 miles per second. That is well short of 0.9 C, not even 1 per cent of C.
Third, if you assume a reactionless maneuver drive run from your power plant, then you are looking at how do you handle all of the heat that the power plant is going to generate. You also have the problem of carrying enough fuel to achieve a decent percentage of the speed of light. Complete fusion of 57 grams of Deuterium will give you about 3 kiloton equivalents of energy. Fifty-seven kilograms of Deuterium will give you 3 Megaton equivalents of energy. Fifty-seven Metric Tons of Deuterium will give you 3 Gigaton equivalents of energy. That does assume that your power plant and maneuver drive is 100% efficient at using the fusion energy. If it is only 99% efficient, then you have around 30 Megatons of energy to deal with and get rid off, from your ship's power plant and maneuver drive. For comparison, that is twice the energy of the largest US nuclear test, the Castle Bravo shot of 15 Megatons.
The idea of throwing rocks as nuclear weapon equivalents is featured in Heinlein's The Moon is a Harsh Mistress, but I think that his 100 ton rocks were only about the equivalent of 10 kilotons or so. I am relying on my memory for that, so I could be off, but the rocks were relying on Earth's gravity well to supply a large portion of the velocity, not the rock thrower.
Note, the following is the energy equivalent of 1 Kiloton of TNT. It is taken from The Effects of Nuclear Weapons-1977 Edition. You can download it at archive.org to check my figures.
Complete fission of 0.057 kg (57 grams or 2 ounces) fissionable material
Fission of 1.45 x 10 to the 25 nuclei
10 to the 12 calories
2.6 x 10 to the 25 million electron volts
4.48 x 10 to the 19 ergs (4.18 x 10 to the 12 joules)
1.16 x 10 to the 6 kilowatt-hours
3.97 x 10 to the 9 British thermal units
Since a Kiloton is equal to 1.16 Million Kilowatt-hours, a Gigaton is going to be the equivalent of 1.16 Trillion Kilowatt-hours. For those used to metric units, a British Thermal Unit is the amount of energy needed to raise the temperature of 1 pound of water 1 degree Fahrenheit. One kiloton of energy will raise the temperature of 3.97 Billion Pounds of Water by 1 degree Fahrenheit. A Megaton will raise the temperature of that much water by One Thousand Degrees Fahrenheit. That is the heat load you have to deal with.
I thought there was a comment on ship's jumping with zero-vector as well, as a safety measure (to eliminate the chance of plowing into a ship upon exiting jump). Not likely in most systems, but a few have enough traffic where this could be a concern.
Of course, I don't think any version of Traveller had rules for ships colliding (by accident or intent). Which it what I thought this thread was going to be about when I saw the subject.
Of course, I don't think any version of Traveller had rules for ships colliding (by accident or intent). Which it what I thought this thread was going to be about when I saw the subject.
What I'm hearing is a lot of conjecture about how planets COULD defend themselves, but nothing about how in decades of Traveller gaming, it's been "solved" in a canonical way. It's apparently one of those things we all just overlook, like the existence of jump drives and reactionless drives.
For the ATU setting I'm working on, jump isn't a thing and I'm fairly comfortable with some crazier solutions like Star Wars: Rogue One's planet shield, at least as something that could be brought up for a specific threat.
For the ATU setting I'm working on, jump isn't a thing and I'm fairly comfortable with some crazier solutions like Star Wars: Rogue One's planet shield, at least as something that could be brought up for a specific threat.
In fact, it has appeard in Traveller quite soon. IIRC in the Secret of the Anciens it was explained how Yaskoidray achieved it, and it was not through accelerating maneuer drives, that would probably need more time than they can afford.
It is also probable that, as you close C speed, MD lose efficiency, something that would be irrelevant for the speeds usually ships reach, but important if you try it.
in any case, I guess (and just that, my guess) the main defenses would be political consequences and forbiding too high speed closely (in astronomical scale) to inhabited planets, as I already said.
As I already said, IYTU sundiving makes things easier for the defender, as the spacelanes are more limited (basically, straight lines from sungates to planets and among planets themselves), so easier to monitor and control, and any ship straying from them should better have a good reason for it. Personally, I don't see this is a true thread there, but, again, it's YTU and YMMV...
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Correct, they were tossed towards Earth using an accelerator, metal bands on grain shipment containers then the rocks. The computers on board put them in orbit around Earth, then dropped them into the ocean for the grain pick up. The rocks were tossed onto tops of mountains. Later on, they ran out of controllers and just tossed rocks, which came in on a ballistic course.
When the rocks hit the muntain tops the flash could be seen from the Earth's moon.
Thats the way I remember it, but its been over 30 years since I read the story.
Really, as you get close to c, all drives lose efficiency -- or, rather, it takes more energy to increase velocity by a fixed amount because your relativistic mass has increased.
I think even IMTU there are lots of reasons for ships to head far out to the gas planets: gas mining, asteroid mining, and so on. A normal Brachistochrone trajectory from a gas giant to the home planet is largely indistinguishable from an attack until the flip-and-brake point midway.
