Limiting size of Jump capable ships

[Meanderer]

I am giving credit for some fixed position sensor arrays of far greater power than the sensors described in the MGT basic rulebook. But are they so exponentially better than ship mounted sensors?

Starship sensors are listed as having minimal effectiveness for visual or radar/lidar beyond long range (25,000 km). Thermal and EM sensors are not much use on an object with no emissions and which could be cooled to whatever temperature they want before launch.

Going with T5 rules it seems a ship wouldn't be able to detect the kinetic torpedo more than a light second out (300,000 km).

Being able to identify that an unknown squadron has jumped in and potentially launched something is not the same as getting precise enough data for a firing solution. The big sensor array could plot this and provide the firing time and solution to a regular vessel whose sensors aren't good enough but how much better are those sensors?

And of course the attackers may plan ahead. Full stealth? Or how about stealth torpedoes with reflective chaff launched in a cloud in the vicinity. The cloud would have the same velocity as the kinetic torpedoes.

Not saying that intercepts would be impossible, only saying that they don't appear certain. And a defense system against such an attack would have to depend on overkill. If you think that one in three tactical nukes should be able to make an intercept you launch ten at each incoming object.

And if strike vessels can jump in and do kinetic attacks with impunity (jumping out before they can be effectively engaged and destroyed) this will take its toll. They just need a few kinetic torpedoes to get through and all they are expending in ordnance is chunks of metal (no fancy electronics or drives) while the resources tied down and being expended to defend the planet are costing much more.

The energy needed to deflect them is obscene and may take considerable notice to achieve further out in the system. Closer detection is more likely and maybe at some point certain but the closer to target they are the more energy is needed to deflect them. And the deflection effort needs to be certain.

So we get back to my point of stationing a lot of defensive equipment and ships in a system in order to protect against an attack from a highly mobile strike force. The fleet intruders don't need to destroy enemy civilizations to be successful - they just need to have a credible capability of doing so to tie down a lot of enemy forces. And if the intent is to effectively destroy an enemy planet (planet is rendered uninhabitable, even temporarily with virtual elimination of the population and planetary infrastructure) then it wouldn't be a fleet intruder squadron but a plan to get an entire fleet in place with a large volley of kinetic weapons. If 5,000 km/s can be intercepted, how about 10,000 km/s or 15,000? How about the kinetic torpedoes trailing the fleet as it continues to accelerate and spread out to clear a path with conventional missiles. or more kinetic missiles that fragment into ball bearings 1 cubic centimeter in size each hitting with a force like a hundred tons of TNT and many of them heading at whatever sensor array is needed to intercept the main torpedoes.

If the intent is to destroy the reactionless gravity-based maneuver drive in Traveller provides a fantastic amount of power to work with. 3 days at 6G makes 15,000 km/s velocity. Fuel isn't a factor just time and planning enough room for acceleration. And an attacking force of sufficient magnitude can be anywhere while each important planet would need to be protected. A

I'm still seeing the advantage being with the attacker and the effective deterrence of such an attack is the ability to do the same in response. (so such attacks are not done on huge interstellar empires because you can't destroy enough in time to prevent similar weapons being unleashed in response.

 

[Infojunky]

Meanderer:
1) note that a combat round is 6 minutes in MGT
2) Bomb-pumped laser torpedoes are nasty, but should logically then be partially degradeable via sandcaster fire.
3) The major problem of the AHL cruiser is this: yes, you could jump out and perform a 'fast fly-by' of the system, but what are you intending to achieve? If your target is anything but 'static' - i.e. carpet-bombardment of the planet itself, the same targeting problems apply to you too.
4) Any counter-fire will have the same velocity advantage against the AHL - kinetic energy doesn't care if the additional impact is due to you closing on it at 5,000 km/s or the other way around; the mutual total closing velocity is all that matters.

I stand corrected on the combat round length. Too used to the old Classic traveler rules I guess.

Be careful there turn length and resultant engagement envelope changes from edition to edition and even within editions depending on your choice of rules sets...

Also note we are skirting on one of the traditional flame-war topics here, near-C missiles and/or impactors. One of the issues that makes it inflammatory is that there isn't an agreed upon operational reference to refer back to, so assumptions vary widely, as often the loudest parties is said discussions are conflicted of their perception of the parameters vis-a-vis they and their opponents are using.

 

[Meanderer]

Yeah, and the WMD/ WTD (Weapons of Total Destruction) debate tends to draw in the whole jump torpedo and robot ships in jump debate since a ship capable of jumping with extreme velocity and retaining that velocity (which is canon) might jump into a star system on collision course with the planet that is so fast it cannot be intercepted.

The last part is solved by varying the time of emergence from jump (typically +/- 1 hour but adding a wider time range prevents such a jump). The margin of +/- 15 hours really puts a stop to surprise fly by kinetic attacks. If you arrive too early or late by a margin of 45 minutes, the planet could be 50,000 km away from where you planned it to be when you emerged. You could fly by without actually being able to attack.

Unfortunately, one key point of Traveller canon makes kinetic attacks an inevitability. Free inertia. In physics, every action is supposed to have an equal and opposite reaction. To accelerate at 10 m/s/s you need to send a reaction mass out the "back" of your ship at sufficient velocity to match the force. In hard science fiction you typically end up with a fusion drive sending fused hydrogen out the back of a ship at extreme velocity (such that the drive itself could be used as a short range weapon) to generate the force to accelerate the ship forward. But Traveller presents us with a drive that only requires a relatively modest amount of electricity to generate large amounts of thrust.

And the retention of inertia (instead of using a Star Wars style of dogfighting in space) keeps it really interesting tactically. I am fascinated by engagements between fleets where velocity/vector differential is so great that they can only take snapshots at each other as they pass within weapons range and where the need to decelerate to change vector keeps a pursuer from re-engaging. Situations where a tramp freighter can outrun a patrol ship.

But the free inertia can be abused (or do we say used when it is such a key part of canon).

But we live in that world already to some point. Nuclear terror. We got used to a world with major powers armed with WMDs facing off against each other and survived it because neither side was suicidal. You can't launch an attack without the other side retaliating.

I think you would naturally get into a situation where each side of a conflict rationally sees the use of such attacks as a line that should not be crossed because you don't want to inspire/provoke the other side into doing similar attacks against you. The Zhodani don't want Imperial fleet intruders mass murdering their citizens. They want to maintain a comfortable buffer zone betweent he Imperium and their fully integrated populations, not get into a total war of attrition. By never threatening the Imperium with anything near the total force it can muster they never provoke the Imperium into turning its full attention against the Consulate. It keeps the conflicts small where some worlds may change hands but the very existence of neither government is ever threatened. (From the Imperium side, putting mega fleets into the Spinward Marches under some Admeral's command runs the risk of creating another barracks emperor). Tactical nukes may be used, but never anything on a strategic scale. Don't want the conflict to get out of hand. (not saying there aren't civilian casualties but never anything either side really has to take notice of.

I think it also works with smaller empires and governments. Pocket-empire A may think it can end its problems with Single-system-government B because B can be taken out with one massive kinetic assault on its one star system. True. But after doing this A may find that the one thing that pocket-empires C, D and E can agree on is that A is too much of a threat to be allowed to exist.

It's kind of the nature of technology that the ability to destroy eventually outstrips the ability to defend. Strategic missile defense remains a dream at our current level of technology. The biggest deterrent to anyone using weapons of mass destruction on their neighbors is that you may potentially draw in other nations that want to punish you for it (hopefully) or destroy you for it (oops). There's always someone bigger or entities that will band together because of what you did. So governments or corporations just won't go there.

That leaves terrorist attacks. This was in one of the old Amber Zone adventures (A Dagger at Efate) where a captured Mercenary Cruiser was put on automated control to jump in and try to collide with the planet to destroy the Imperial Marines base (if I recall). It's effectiveness was limited by the lack of certainty where/when the ship would emerge from jump which required it to jump further away from the planet and calculate an attack vector which it then had to accelerate on. Made for a decent adventure where the ships at Efate would be on the wrong vector to intercept and only the player's vessel approaching the system had the ability to catch up and match course (board and use the ship's engines to alter its course to miss the planet).

This threat can be massive because it doesn't take any special technology to run this. (make a big spear of crystaliron (TL 10 I think) and accellerate it long enough with a starship and you have a dangerous weapon).

Limitations include

- not much call for telephone poles made of crystaliron. companies that work this material may want to know what it is for before making it and may tip off the authorities. Just taking a starship or piece of junk makes for an object that is larger and therefore easier to detect.
- terrorists may not have access to full military grade ships (so they accelerate their weapon at maybe 3G maximum) and their ships will have less stealth capabilities to hide or screen their kinetic weapon
- smaller scale attack: a single weapon or just a few offers greater potential to intercept than a volley of 20 or 40 (or 100) kinetic weapons.
- Osama bin Laden factor, or how badly do you want that massively powerful government to want you dead?

No terrorist attack, even on the Imperial Capital, will destroy the Imperium (just maybe change who is in charge). And everyone will want to know who did it. Terrorist groups usual want to claim responsibility to show they are active and powerful. Why do something that changes very little that you can't ever take responsibility for? Still some madman may do such an attack but this makes it a rare occurrence with maybe only localized effect. And of course it would be easier to jump in way out in the Efate system and accelerate on an attack vector than trying this at the Imperial Capital (where any ship approaching the planet may need to be escorted/boarded by naval personnel and maybe a navy pilot is required to do the landing).

 

[Meanderer]

Also note we are skirting on one of the traditional flame-war topics here, near-C missiles and/or impactors. One of the issues that makes it inflammatory is that there isn't an agreed upon operational reference to refer back to, so assumptions vary widely, as often the loudest parties is said discussions are conflicted of their perception of the parameters vis-a-vis they and their opponents are using.

Yeah. I think we are both in agreement that the fairly stable state of political events depicted in Third Imperium materials is the correct state of affairs - and so there are reasons why the various entities are not throwing objects at each other with extreme velocities (though we may disagree as to what the exact reasons are).

The problem is that while the math is quite straight forward as to the energies involved we have a combat system that is just not geared to handle such things. It presumes ships encountering each other without that much velocity difference such that you could put them on a big hex map and handle the battle using a combination of core rules and the Mayday board game rules. So we get a great big grey area as to what happens. But it is possible with a bit of research to apply physics and information about Space to the situation.

Like constant acceleration up to near c. I don't think you have to get to the point of recalculating the mass of the ship based on relativity (or the impact of increased mass on a hull structure that isn't increasing in strength). This is because space is not truly empty and the effect of this will accumulate. I think the cumulative impact of collisions with atoms will prevent a ship from accelerating up to the point (about 90,000 km/s) where it becomes worthwhile recalculating mass. There are a lot of different estimates of the composition of Space but a common estimate is 1 atom per cubic centimeter. This could be almost any type of atom but hydrogen and helium will be the most common by far.

A useful statistic to point out when players insist they can accelerate constantly for many days.

1 atom of hydrogen is 1.67 x 10^-27 kg. A really small number but there are things we can do with that number.

For example, a ship's boat from Traders and Gunbots (Classic Traveller LBB) is shown on the deck plans to be 4.5 m wide. Assuming a cylindrical shape that's about 16 square meters front profile (160,000 square cm). So a velocity of 50,000 km/s means an impact energy of 3340 joules if all you are hitting is hydrogen atoms. Big deal. That's less than a gram of TNT. Except that this is the sum of many collisions over the course of just one second. Nothing penetrating the hull but there would be a heat transfer to the ship for this collision since the full energy would have gone into the hull. And this is happening every second. 3 kg of TNT per hour. 10 tons of TNT per day. Again it is spread out over time but this seems like heat that isn't going anywhere because all the particles being touched by the hull are imparting heat not absorbing it. At what point does the hull start to melt? And that number is assuming all collisions are with hydrogen atoms. The heat should be greater because some hits are helium or even heavier atoms. And this is not only cumulative but is increasing as velocity increases. At 10,000 km/s the impact is just 82 kg per day. Now what does that mean in the rules since the rules don't give us details on what TNT does. The Explosives in the core rulebook don't describe size but if we call the plastic explosive the equivalent of c4 and say it is the quantity involved is the equivalent size of a stick of TNT (200 grams) then at 10,000 km/s it is like 1,240 dice damage per day (accumulating with the damage increasing daily over 8 days to about 155 thousand dice at 50,000 km/s). You can do that for a while with really good hull armor and maybe some extra heat sinks on board, but eventually that heat is going to get transferred into the electronics and habitation sections and the engines. Obviously acceleration would have to cease long before velocity gets to 90,000 km/s.

And if players don't take a hint about the increasing hull temperature, with sensors starting to malfunction, then a good referee will start to announce "I need to roll to see if you hit a piece of sand. [rolling]. Okay, your hull is still holding".

Sometimes it doesn't matter if you are the windshield or the bug.

I think there are reasons that the Ancients' near-c chunks of rock were accelerated through teleportation portals, the first few passes through the acceleration chamber would already have picked up or cleared all the atoms and dust present so this wouldn't be a factor. But try doing the acceleration in empty space and you find out it isn't as empty as you think.

 

[Meanderer]

the dice of explosive damage is on a personal combat basis, not space combat, but 4,300 points of damage from anti-personnel weapons seems like a lot for a ship's bulkheads to absorb. I'll leave it to any other interested party to equate this damage to a space combat scale. Since it is over multiple square meters of hull impacted I will repeat that this isn't penetrating the hull, just energy heating the hull (and slowing down the ship ever so slightly).

But a big point here is that the amount of damage increases with surface area. Having a greater surface area on the front of the ship means hitting more atoms per second.

I'm thinking civilian ships won't want to go over 10,000 km per day (or even 5,000 km/day) as this may (or will) damage sensors. Military vessels will have their sensor equipment more hardened and protected so maybe they can go this fast but not for several days at a time.

I'm thinking of stories of ships that misjump into deep space and use their maneuver drives to get the ship on a vector to the nearest star system. So we have ships that accelerate till they run out of fuel and then coast on hoping to be detected. Of course these are ships that aren't expected to operate again. Maybe they accelerate as much as they dare and all low berths are put into use to maybe save the crew. They would use their maneuvering thrusters to turn the ship so that the low berths are as far back as possible, and hope that while the sensors and hull melt away maybe that part of the ship can survive perhaps with a computer backup to record what happened.

At 15,000 km/s a lost ship will take about 65 years to travel one parsec. This is a long time to hope for rescue but may be too fast to prevent melting along the way. Some judgment required. But the crew of these ships won't want to send it too fast if electronics won't be working when the ship gets to the nearest star system. I think they would want the ship going slow enough that it could be intercepted and boarded.

 

[Meanderer]

Of course anyone is free to apply different assumptions in their campaigns. The grey area in applying the hard physics to the game rules, and deciding on whether anyone's own Traveller universe has the same physics as our own, leave a lot of room.

So anyone who wants limits on how fast a ship can go can draw on what I wrote or make some limitation on gravitic maneuver drives so that they, similar to the effect of velocity on mass (Relativity), just stop being as effective the faster you get. So you can get 6G acceleration from a stationary position but sometime around x velocity you only get 5G at full power, then 4, etc. until you hit some maximum velocity from which you can gradually slow down but can't exceed without some other source of thrust (like a rocket). The Maneuver drive is largely fantasy anyway, so why not. An interesting thing about a maximum speed rule like the one I proposed is that ships doing high velocity attack runs may be reduced to 1G or less maneuver and will have much less ability to evade defensive fire. This can force fleet battles to be lower velocity affairs as each force tries to keep initial velocity down so they can have maximum maneuverability.

So of course there is no right answer. Not trying to provoke a flame war. I just like crunching the numbers and exploring the implications. Kind of why I am on a sci-fi game forum.

The great thing about implications is that there is a gap between what is possible and what will happen that depends largely on the human factor.

If you have a universe where kinetic WMDs are possible, you could end up in a universe gone mad with massive destruction unleashed on the innocent. Or, you could have an established history something like this: The Fourth Frontier War ended shortly after an overzealous Imperial admiral launched a kinetic strike at the Zhodani Industrial world of Gesentown. Launching staggered waves of kinetic missiles the planet was hit through much of its rotation killing the vast majority of its population. Public shock at the staggering loss of civilian life and fear of retaliation prompted the Imperium to propose peace after the victory at the Battle of Two Suns, holding off on a planned offensive to recapture the lost worlds in the Jewell Sector as it appeared more urgent to keep the conflict from escalating. The Admiral responsible was court-martialed and publicly executed. Reparations were paid to the Zhodani Consulate to assist in the reconstruction of Gesentown and compensate for the loss of life. This second option, while never quoted in any official material because I just made it up, is not inconsistent with the current borders and supports the continued Zhodani mistrust of Imperials and desire to secure their borders. Meanwhile the Imperium remains nervous that hostilities may resume. Depends on what sort of universe the GM/Referee wants to run and what sort of universes we want to speculate about.

It really is just a game and so long as players are having fun interesting adventures what else really matters. Just as pretty much every sci-fi author fudges the science in order to make a good story.

 

[sideranautae]

Of course anyone is free to apply different assumptions in their campaigns. The grey area in applying the hard physics to the game rules, and deciding on whether anyone's own Traveller universe has the same physics as our own, leave a lot of room.

So anyone who wants limits on how fast a ship can go can draw on what I wrote or make some limitation on gravitic maneuver drives

I use a grav well creation approach to my grav drives. I put a limit of ~6,000 km/sec as the fabric of space resists being distorted at higher speed.

 

[Meanderer]

Do you have the effectiveness of the drive go down as well? Is it smooth sailing up to that point, or does it take progressively more energy the higher the velocity.

I thought of this type of limit just today while typing that message and really like the implications. You can get high speeds when they are needed for the story but you get reasons why captains will want to avoid maximum speed if a fight is expected. I guess I was thinking of how the light speed barrier works, where it isn't so much a limit where you just can't speed up any more but the effect of progressively increasing mass such that your thrust to weight ratio starts approaching zero.

It seemed like a cool way to limit kinetic attacks if the attackers get more vulnerable at higher speeds and taking longer to get up to those higher speeds. But a lot of extra math to do in the game.

Cool to see someone else had already thought along similar lines.

 

[sideranautae]

Do you have the effectiveness of the drive go down as well? Is it smooth sailing up to that point, or does it take progressively more energy the higher the velocity.

I thought of this type of limit just today while typing that message and really like the implications. You can get high speeds when they are needed for the story but you get reasons why captains will want to avoid maximum speed if a fight is expected. I guess I was thinking of how the light speed barrier works, where it isn't so much a limit where you just can't speed up any more but the effect of progressively increasing mass such that your thrust to weight ratio starts approaching zero.

It seemed like a cool way to limit kinetic attacks if the attackers get more vulnerable at higher speeds and taking longer to get up to those higher speeds. But a lot of extra math to do in the game.

Cool to see someone else had already thought along similar lines.

I haven't but it would be a good idea to have it stress the M-drive as it gets at ~5000 km/sec. Maybe require Engineer checks (a la Scotty saying, "I kinna keep this speed up much loonger Captain. The gravitic oscillations are gunna to tear the ship apart!") 8)

 

[Meanderer]

Ah yes, great idea. I figured on having the drive get less efficient/effective as speed increases so at one point your 6G engine pushing at full power is only getting you 2G of acceleration. Maybe pushing it past its safety limits might get you an emergency acceleration of 3G, and maybe even running it at full power past a certain speed puts strain on the engines.

Gotta have something for the ship's engineer to complain about. :wink:

It means you may get some madman taking his ship(s) up to 5,000 km/s for some murderous attack run but it is something that sensible captains and admirals avoid.

And the players might need to push their engines and make some skill checks for the purposes of an adventure but you've got some leverage to discourage them if they are doing it on their own and are getting out of hand.

 

[sideranautae]

Ah yes, great idea. I figured on having the drive get less efficient/effective as speed increases so at one point your 6G engine pushing at full power is only getting you 2G of acceleration. Maybe pushing it past its safety limits might get you an emergency acceleration of 3G, and maybe even running it at full power past a certain speed puts strain on the engines.

Gotta have something for the ship's engineer to complain about. :wink:

It means you may get some madman taking his ship(s) up to 5,000 km/s for some murderous attack run but it is something that sensible captains and admirals avoid.

And the players might need to push their engines and make some skill checks for the purposes of an adventure but you've got some leverage to discourage them if they are doing it on their own and are getting out of hand.

Yes, a check to get the drive to take added/needed power increase without damaging the drive. I set the upper limit at 2% of c. Maybe the 1st check being at 1% c as a first hurdle. Add some tension in those cases when you are running far & fast.

 

[Meanderer]

And if we are treating this as a sort of resistance of the "gravitational field" to manipulation by the maneuver drive, is this just a drive matter or does the "gravitational drag" that is being pushed against also affect the hull.

Maybe a ship needs to have extra structural strength to take such speeds safely and taking your merchant ship up to too high a speed means running around with repair foam to plug all the hull breaches. And dealing with the effects of sudden pressure differentials.

(Ever informed players about ship's toilets backflowing and erupting like volcanos? With bodily waste being filtered to recycle all water, what gets thrown back up is particularly foul. The science and engineering on this is probably way off, but plumbing sure can become a priority once players have to start making DEX rolls to avoid touching anything).

 

[sideranautae]

And if we are treating this as a sort of resistance of the "gravitational field" to manipulation by the maneuver drive, is this just a drive matter or does the "gravitational drag" that is being pushed against also affect the hull.

That could be possible given a high G drive. Let's say you have 2-3 Gs acting right next to the hull is a very rapid on/off/reverse pulse. I could see it stressing internal supports. I would say it could be the result of the engineer failing to adjust the drive output correctly when running up against the limit.



Engineers generally don't have much to do except when prepping for jump. This should give them some excitement at other times. :twisted:

 

[phavoc]

Traveller drives have always been about continuous acceleration, turnover, then continuous deceleration until you reach a zero-zero velocity (or something a great deal smaller) in relation to your target. A ship heading, say from Terra to Pluto would accelerate halfway and then decelerate. You can't do that today because we can't keep the engines powered (cept for some of the new ion engines). Traveller grav drives make it entirely possible to zip around the solar system and reach your targets in a reasonable amount of time. Think of in-system travel being like how people travelled by liners and fast ships in the 1900s. Then Europe to the US was about a week on a fast liner, a couple of weeks on slower or cargo ships. A higher-G liner would be the equivalent of the fast liner, and a free trader would be like the cargo ship. It'll get you there, just not as fast.

Destruction wise, it's always been easier to destroy than create. MAD worked in our crazy nuclear-armed world because even by "winning" you would lose. And no enemy can ensure they would wipe out their opponents in one strike. So what you'd have is an escalating war where habitable planets would slowly die and a no-man's land would be created between the warring opponents. And, like you said, it's nearly impossible to constantly protect a planet from attacks where the enemy just wants to destroy the biosphere. Instead of kinetic energy weapons you could introduce biological weapons, easily delivered in stealth capsules travelling at only a few hundred Kph. You don't need speed to destroy a biosphere.

Plus, if you detected an inbound ship or object zipping in, at that kind of speed it can't maneuver very well if it intends to hit its target. All you would need to do is put a few hundred dense objects, say the size of cannonballs, in its path and let physics take care of the rest. As long as yo shredded the object the remaining pieces have the potential to burn up or deflect off the atmosphere.

While total destruction is entirely possible in a variety of scenario's it's really a zero-sum game as long as your opponent has the same things to lose.

 

[Meanderer]

That could be possible given a high G drive. Let's say you have 2-3 Gs acting right next to the hull is a very rapid on/off/reverse pulse. I could see it stressing internal supports. I would say it could be the result of the engineer failing to adjust the drive output correctly when running up against the limit.

This would mean not all 6G vessels perform alike. A destroyer would be built to take a lot of punishment and could probably handle this more than someone's racing yacht.

But I'm thinking this could happen even on 1G vessels that aren't designed for extreme performance. A tramp freighter might be rated to not ever go over 500 km/s.

The issue would be acceleration, right? Once you gently get up to a speed you can coast at it for a while, but a tramp freighter nursed up to 1,000 km/s may be stuck where it can't do any radical maneuvers without risking structural damage. Only acceleration and deceleration down its current vector can be safely done. This creates another factor in ship movement other than the overall strength of the maneuver drive. You can have a heavily reinforced ship's launch that can maneuver safely at a full 1G in any direction and a tramp freighter that turns like an oil tanker.

 

[Meanderer]

Destruction wise, it's always been easier to destroy than create. MAD worked in our crazy nuclear-armed world because even by "winning" you would lose. And no enemy can ensure they would wipe out their opponents in one strike. So what you'd have is an escalating war where habitable planets would slowly die and a no-man's land would be created between the warring opponents. And, like you said, it's nearly impossible to constantly protect a planet from attacks where the enemy just wants to destroy the biosphere. Instead of kinetic energy weapons you could introduce biological weapons, easily delivered in stealth capsules travelling at only a few hundred Kph. You don't need speed to destroy a biosphere.
.....

While total destruction is entirely possible in a variety of scenario's it's really a zero-sum game as long as your opponent has the same things to lose.

Agreed. There are many ways to destroy and the biggest danger is that you will provoke others to do the same to you (not necessarily the people you attacked but even a neighbor that would prefer to strike first rather than wait for you to do the same to them). A few posts ago I drafted a paragraph about an alternate history of the Fourth Frontier War in which a rogue Imperial Admiral unleashed such an attack on a highly populated world and the Imperium ended up sueing for peace and paying compensation (not out of compassion but out of fear of the situation getting out of control and to try to reassure the Zhodani that this wasn't going to happen again.

Massive destruction available in a high-tech society should tend to limit the frequency of war as war becomes too messy and too hard to control once it gets started. The political leadership may not want to fully trust it to the admiralty and/or the admiralty may caution the political leadership of how messy a war can become. I'm reminded of the motto of the U.S. Air Force (or particularly their nuclear armed strategic bomber command): "Peace is our Profession". The military may be more focussed on maintaining a credible and dangerous show of force so the other side doesn't dare try anything - rather than actually getting into a war. (An explanation as to why generations go by between major frontier wars).

Plus, if you detected an inbound ship or object zipping in, at that kind of speed it can't maneuver very well if it intends to hit its target. All you would need to do is put a few hundred dense objects, say the size of cannonballs, in its path and let physics take care of the rest. As long as yo shredded the object the remaining pieces have the potential to burn up or deflect off the atmosphere.

I did some calculations on this that would work out with 10kg cannon balls travelling at 500 km/s (not just strewn in the path) against a 50 ton kinetic torpedo. Unfortunately while an impact may cause the torpedo to crack or break into pieces those pieces will retain much of their kinetic energy and vector. Essentially, in this case, the interception needs to be more than 4 million km out or it won't be enough to cause the torpedo to miss the planet (assuming the torpedo is aimed at the planet's core.

At 5,000 km/s not much is deflecting and there is not enough atmosphere to slow down the object. It's kind of the problem of intercepting asteroids. You can't just destroy the asteroid you need to change its course to make it miss. A 50 ton rock or fifty tons of gravel may not make that much difference. They both put the same amount of energy into whatever they hit. I've mentioned effects similar to "nuclear winter" but I understand that an ocean hit may be worse with massive tsunamis and so much water thrown up into the atmosphere that you get a big global warming impact (I think there is a term Nuclear Summer for this).

The maneuvering point you make is really key though. They aren't just aiming at the planet and accelerating; the attacking ship is aiming at where the planet will be when it's planned course intersects that orbit. (Earth orbits at 30 km/s. The attackers will need to plan the interception time down to the minute. If you can cause the ship to stop accellerating early it's course will be all wrong for an interception. Strew that gravel in the path of the ship that hasn't reached its attack vector such that you knock out its engines (and pretty much everything else if it is going super fast) and you have pre-empted the strike.

Kinetic attacks will require a lot of room to pick up speed on a fairly precise course. Denying the ships trying to deliver the kinetic attack the time and room to achieve their attack vector is the best defense (if you have a ship in the right position to do this). The problem is that space is really big so it may be a matter of luck that there are ships that can intercept in time. It may take thousands of ships to mount a complete defense with just a few of them available to intercept the attacking force. (it takes the attackers days to accellerate in but can also take days for defenders to accellerate out to intercept; and the further out you station the ships the larger the circumference of the orbit they are defending).

Which brings us back to the Mutually Assured Destruction defense. The odd test of a kinetic torpedo on some gas giant moon reserved for weapons testing goes a long way to show an enemy that while they may get into a key system and catch the defenders with their pants down, it is not something they really want to do.

 

[Infojunky]

The issue would be acceleration, right? Once you gently get up to a speed you can coast at it for a while, but a tramp freighter nursed up to 1,000 km/s may be stuck where it can't do any radical maneuvers without risking structural damage. Only acceleration and deceleration down its current vector can be safely done. This creates another factor in ship movement other than the overall strength of the maneuver drive. You can have a heavily reinforced ship's launch that can maneuver safely at a full 1G in any direction and a tramp freighter that turns like an oil tanker.

I really want to to reconsider this, there is basicly only one force that can act on said Tramp, and that is the force of it's drive. "Radical" maneuvers all turn into sitting on its drive.

Repeat after me, "out of Atmo 1g is 1g".

 

[sideranautae]

But I'm thinking this could happen even on 1G vessels that aren't designed for extreme performance. A tramp freighter might be rated to not ever go over 500 km/s.

Probably the build would depend on need. So a tramp would be spec'd for what it might need. Distant GG to main world. You'd have to figure the top speed based on that.

Only acceleration and deceleration down its current vector can be safely done. This creates another factor in ship movement other than the overall strength of the maneuver drive. You can have a heavily reinforced ship's launch that can maneuver safely at a full 1G in any direction and a tramp freighter that turns like an oil tanker.

The way I envision Grav drives working probably not. (YMMV) Maneuver with that type of Grav drive is done in free fall whether it is 1 or 6 G. There is no feeling of acceleration.

 

[sideranautae]

I did some calculations on this that would work out with 10kg cannon balls travelling at 500 km/s (not just strewn in the path) against a 50 ton kinetic torpedo. Unfortunately while an impact may cause the torpedo to crack or break into pieces those pieces will retain much of their kinetic energy and vector.

That is why you have to vaporize it. Simple enough to do at a distance given Trav weapons. Trivial in fact. Nukes and/or lasers will do it nicely.

 

[Meanderer]

Well... vaporizing it, as in heating it enough to melt and then boil it, doesn't change the fact that this vaporized metal still exists, consisting of a very high number of atoms travelling towards your planet at a very extreme velocity.

So you have a 5,000km/second obscenely hot wind.

Still hits the atmosphere with an awful lot of energy.

When thinking of items burning up (exploding, actually) within the atmosphere or deflecting off, we are typically thinking of meteoroids entering the atmosphere at typically 20 km/second - ranging in size from small grains to around 1 meter wide. They enter the atmosphere at such velocity (even 20 km/s is damn fast - more than 60 times the speed of sound). The air in front of them is pushed and compressed to a very high pressure, and the object moves faster than air can flow in behind (near vacuum) so you end up with a huge pressure differential that can tear the object apart.

You can look up some of these significant yet slow moving objects:

http://en.wikipedia.org/wiki/Chelyabinsk_meteor a meteor that caused numerous injuries including eye damage and "sunburn", and

http://en.wikipedia.org/wiki/Tunguska_event in Siberia that caused detectible changes in atmospheric pressure over England, an earthquake shockwave of around 5 on the Richter scale, one that caused massive destruction over a large area (leveled over 2 thousand square km of forest) - believed to be an asteroid with a kinetic energy of around 10-15 megatons.

Both of these are examples of objects that are considered to have "burnt up" in the atmosphere as there was no point of impact on the Earth's surface. The energy still has to go somewhere.

To stop a kinetic weapon requires as much energy that the kinetic weapon carries directed on an opposite vector. Theoretically, a 10 kg object could be accelerated to have as much kinetic energy as a 50 tonne kinetic weapon travelling at 5,000 km/s. Thanks to Albert Einstein we can even calculate how fast the 10 kg object would have to be to match this energy. Just 85% of the speed of light.

Obviously it is not necessary to actually stop the kinetic weapon. Just deflecting it enough so that it misses is enough. Put a large enough object in its path and this can be assured. Better yet, have that object collide with a vector of its own. A 10 kg cannonball with a velocity of 500 km/s has an energy of 2.5 x 10^13 Joules. A 25 billion ton rock moving at 1 m/s has the same kinetic energy. This is enough to alter the course of the kinetic torpedo by a vector of 50 m/s. This is significant because if you do this more than 4 million km away it may miss the planet. To close and you will only change where it hits. Rather than match kinetic energy against the object where it got a head start with an insane amount (1.25 x 10^18 Joules), I'm thinking that the intercepts would be done with nuclear weapons. Kind of a lopsided expense of resources as the attacker is losing a 50 tonne chunk of metal while the defender would be expending multiple nuclear missiles per kinetic object it wants to intercept. (Coming in at 5,000 km/s you won't get multiple shots as it crosses weapons range - so multiple missile would be used to ensure that at least one will hit).

The biggest problem with trying to intercept a kinetic weapon, as opposed to a device such as a nuclear warhead is there is nothing in the kinetic weapon that needs to be functioning on impact. Shatter a nuclear warhead and you have a quantity of radioactive material raining down but nothing that will detonate it.

Shatter and/or melt a kinetic torpedo and it can still be coming on with pretty much the same energy. Hits the atmposphere and causes a huge shockwave, pushes through to the survace and causes earthquakes, or ocean (boiling a large amount of water and causing an earthquake whether it hits the ocean floor or not).

The kinetic energy of the 50 tonne weapon I described is enough to take 3.7 billion tonnes of water from 20 degrees celsius to boiling. Obviously the weapon won't do all that as some of its energy will go into the atmospheric shockwave, tsunami and be absorbed by the planetary crust (earthquake).

Maybe a few more nuclear missiles to make absolutely sure that thing misses.

(kind of imagining the impact of the kinetic torpedo on that 25 billion tonne chunk of rock. Depleted uranium anti-tank shells would have nothing on that torpedo. It may be a molten shaft of metal when it comes out the other side. Pretty sure it would, but energy would be lost pushing that big rock up to some speed to. Energy enough to push a 25 billion tonne rock from zero to 7 km/second instantaneously would seem enough energy to shatter the big rock. To be fair though the big rock would seem big enough that how it shattered might also affect the new speed and course of the kinetic kill object. But that's theoretical. It isn't practical to put such huge rocks in the path of anything.

The physics of the 50 tonne kinetic weapon I described is staggering. Not quite as staggering as the asteroid that hit Chicxulub, it's not going to wipe out most life on the planet (or at least not on its own) but the dinosaur killer was estimated at 10km in diameter. Imagine 0.3% of the energy of the dinosaur killer packed into a 3 cubic meter package.