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KKM and Plasma Weapons

Fritz88
I really don't know if the transfer of KE is going to work, though, if the rocks are stationary and the really large mass of the ship is what's moving.
I suspect it would work. I like the idea as it does add a bit of finese and manuever to encounters, and would be a good place to use that ships tactics skill.

meson gun mines! I gotta find that, just the name alone sounds scary.
 
Hey Fritz

Please don't take this post as criticism, it's just that I ran the math on "deep space minefields" a few years ago, and gave it up as completely impractical if the "mines" aren't (seriously) maneiver capable.

The problem with chemical reaction rockets is that they just don't have the endurance for space combat against nuclear powered vessels: The Saturn-V boosters come it at around a G-turn of thrust (yup, that's 1 G for 1/2 hour, with a fuel ratio exceeding 90% of the mass of the rocket!) so while chem burners can give you awesome accellerations that are really crappy for space ranges. Note that the missile propulsion postulated for FF&S are actually nuclear rockets ;)

However:
There is no difference at all between being hit with a fast moving rock, or running into a rock when you're stationary. That said, space is big: figure out the tonnage of rocks (or sand) needed to guarentee a hit on a 1 Kton vessel in a 1,000 Km circle (note that this is a plane, to get better odds (and not require your target to do *exactly* what you want you will need dispersal in a sphere). If you figure on needing a rock every 10 meters, that's a rock every 100 square meters (on a grid layout)

Area of your disk is a "mere" 3.1 *Trillion* sqaure meters, so you only need 31 Billion rocks.

A Brilliant lances hex is 30,000 KM in diameter, so to create this "terrain" you would probably need something the mass of a small planet to disperse, so I'd go with the "seeking rocks" idea.

Scott Martin
 
Scott, no problems with critiques here. :D I actually have run the numbers on saturating an area - Yowza! :eek: But, you don't have to do a sphere, just a disk - think of it as a net. Of course, you have to get your opponent to do exactly what you want him to do, and that is often problematic.

As far as the chemical rockets, my design doesn't really need anything that provides a lot of power - the ship has lent the missiles (rockets, really) most of their velocity before release. The idea is that you get that velocity way out-system, then let 'em fly. They gain extra velocity from the chem motors to gain separation (and some extra KE), then rely on good ol' Newton to hit the region of space at which you were aiming. It has very limited usefulness, but it could be a nice opener for an invasion fleet (if timed properly).

For my meson minefield, it uses a high-TL technique to cause ships not in the proper lane to precipitate out of jump into the minefield. So, you only need a 2-d layout, and you can somewhat predict the lines on which to lay these minefields based on jump routes (all but the one you want folks to use).
 
Hi Fritz

I'll have to post my "FTL Constraints" they make the kind of thing you are postulating a lot more practible. I think that there's already a thread going, but I have a lot on my plate at the moment...

My pocket empire of choice deals with KKM defence / hit and run raids from the jump points by parking a large number of (very large) solar arrays between the primary emergence points and the habitation nodes. The arrays and associatede industries are constantly critiqued for their "interference" with interstellar shipping (they require a few extra g-hours and an extra half day to avoid for merchant shipping) but they effectively interdict the "direct fire zone" for a high-velocity transition. It is no coincidence that the solar aarrays just happen to have a lot of inexpensive point defence cannon mounted, since the power is "free" (if diverted from their primary task of vaccum smelting)

I had originally considered an artificial "sand belt" but written it off as impractical (economically) but large solar arrays have an economic purpose and a reason to keep in one position relative to the jump emergence point. They are also low-materials high surface area constructs (*very8 2-D) so I have yet to come up with a better interdiction construct that isn't:
1) Obviously military
and / or
2) insanely expensive to maintain

Scott Martin
 
Originally posted by Scott Martin:

My pocket empire of choice deals with KKM defence / hit and run raids from the jump points by parking a large number of (very large) solar arrays between the primary emergence points and the habitation nodes. The arrays and associatede industries are constantly critiqued for their "interference" with interstellar shipping (they require a few extra g-hours and an extra half day to avoid for merchant shipping) but they effectively interdict the "direct fire zone" for a high-velocity transition.
This sounds an awful lot like an interstellar "Maginot Line".

Is the goal simply to "get in the way" of a high velocity intruder?

Why would such an intruder enter on the specific vector where you just so happen to have all of this industry set up? Why would the intruder not know about these facilities, and simply go around?

I don't necessarily understand jump space, but does the exiting real space vector of the ship have anything to do with where a ship can emerge from jumpspace? I understand that the ship maintains that vector when they leave space, but that doesn't explain why the navigator can not place the jump space exit point at someplace appropriate to the actual vector.

Finally, with regards to KKMs, isn't the energy transferred related to the mass of the target at impact? Simple example being a bullet and a piece of paper. I've yet to see a bullet light a paper target on fire simply by passing through it, and I don't think that the bullet is much harmed by the paper either.

So, having a high mass, high velocity projectile impacting with a (typically) light weight solar array, would it have that much affect? I don't expect to see spontaneous nuclear scale detonations happen all over the solar arrays as the projectiles exit jump space and start hitting the array.
 
Hi Whartung

At the relatively "low" velocities of a bullet, no you don't see a lot of effects. At orbital velocities (hundereds of kilometers per second) then a grain of sand is a significant threat (more energy than a typical high caliber anti-tank penetrator) I'm pretty sure that if your bullet was travelling at 100 kps the interaction would be a bit more lively. (no, not nuclear, but the thermal effects would be significant) Alternately (a slightly different tack) how would your bullet interact with a tungsten filament? (this would have similar working properties to the bracing used on a large orbital solar collector)

The "Manginot Line" is ONLY effective in a universe (MTU is very carefully modeled this way) where
1) the points of exit from Jumpspace are both very constrained and predictable
2) there is a hard velocity limit on transit exit
3) there are no reactionless thrusters.

The first two constraints (plus a conveniently placed object) stop tactics of jumping in with a high velocity bearing on the most important population concentrations, launching ordinance and immediately jumping back out. It does not stop anyone from launching ordinance on a different bearing and doing exactly the same thing, but this means that there is more time to do something about it, and that the ordinance needs to expend significant fuel reserves to change its bearing back to threaten those facilities.

Note that I would not expect the projectiles to be destroyed by impacting the array, but I would expect either a mission kill (loss of maneuvering) or a degradation in perfornmance, both of which are "desireable" from a defensive point of view. You also know that you are under attack, and the rough vector of attack, two useful pieces of information in system defence.

Again, if you are using reactionless thrusters then this is pointless, since the "munitions" have infinite delta-V...

There is always a way around even the most thoughtfully laid defenses, but this kind of thing at least forces your attackers to be a bit creative...

Scott Martin
 
Originally posted by Scott Martin:
Hi Whartung

At the relatively "low" velocities of a bullet, no you don't see a lot of effects. At orbital velocities (hundereds of kilometers per second) then a grain of sand is a significant threat (more energy than a typical high caliber anti-tank penetrator) I'm pretty sure that if your bullet was travelling at 100 kps the interaction would be a bit more lively. (no, not nuclear, but the thermal effects would be significant) Alternately (a slightly different tack) how would your bullet interact with a tungsten filament? (this would have similar working properties to the bracing used on a large orbital solar collector)
It just seems to me that while the energy contained in the grain of sand may be substantial at high velocity, the target needs to be able to absorb that energy for it to be of any use.

Back to the bullet analogies, modern bullet design is focused on expanding the bullet shape from it classical pointy shape into something much more blunt, and also larger in diameter in order to transfer that energy into the target rather than "merely" punch a hole.

I can't even guess what a grain of sand would do to a piece of paper at high velocity. Would it just spontaneously alight on impact? Would there be a bright flash on impact? How much of the sand grain would be consumed?

And rather than having an expensive facility there "in the way" why not have a cloud of sand/pebbles/ball bearings, etc. there instead? Must be a lot cheaper to deploy, cheaper to repair, and, if you're not going TOO fast, it's even safe to fly through for your merchants.
 
I wanted to post something here but you guys got this one going in all kinds of directions. LOL but it does make a good point for space combat in its various forms. I cant think straight to add my two cents yet!

I'm not going to touch this one...


Take Care and Merry Christmas and Happy New Years Folks!


Keep it Metal!
 
Hi Again Whartung

I hadn't thought of modeling this type of collision as "rock versus paper"

This might belong in the new topic, but it is pretty directly related to how to defend abgainst KKM's so I'll park it here.

The grain of sand would probably punch a nice clean hole through the piece of paper and heat up a chunk.

If the velocity is high enough then the grain of sand may melt or vaporize. You are transferrig a lot of kinetic energy from the sand grain to the bit of paper "punched" out of the sheet of paper to accellerate it, and a teeney bit to punch it out of the sheet. If the collision is "prefectly elastic" then no heat is transferred, but I can't think of any perfectly elastic collision at orbital velocoties.

If enough thermal energy is transferred then any "delicate" systems on a KKM (control, power, sensors or propulsion) are susceptable to damage. If the KKM carries submunitions with a bursting charge, then this collision is probably sufficiently energetic to blow the bursting charge. If any of the above are true, then it becomes trivial to intercept or destroy the munition before it strikes its target (or in the case of a maneuvering target, to just get out of the way)

I'll run the numbers on a projectiles at various speeds (say 1 to 1,000 kps) hitting 1 mg of material for comparison, with a range of kinetic transfer efficiencies: you can judge for yourself the effects on the target based on the thermal transfer.

If the "paper" is made of something tough (tungsten filament was my previous example) then a chunk of the energy may instead be used to cause physical deformation to ("cut" or "punch") the high velocity projectile. At orbital velocities even if the target material is insanely tough or thick it is unlikely to not be deformed (AKA "have a hole punched through it")

More later when I run the math...

Scott Martin
 
Scott, what about the idea of jumping in at an a tangent to the target (coming in from above, at an angle, not aimed at the target - if you are aimed directly at the target (and its near a massive body), you won't be able to jump directly out). You don't change the vector of the launching ship, but you launch the KKMs tangentially to the ship using a rotating mechanism (the launcher spins around the axis of the ship perpendicular to the vector of travel). How much of the ship's velocity would be imparted? If you get a substantial amount of the ship's velocity with a few degrees of vector change, you can jump out in a straight line, while retaining your missile velocity for a kinetic kill.
 
Hey Fritz

The velocities that we are talking about for KKMs are pretty mind-boggling: for your ship (or spinner) to have enough angular velocity to significantly affect the vector of a "spun" missile, it would likely be putting out enough angular momentum to turn the occupants into jello, or requiring massive sttructural bracing: you're looking at needing 13,000 m/s of angular velocity for a 1 hex/turn change in velocity. That's an insane number of G's even in a "tight" arc.

You could probably build a launch "spinner" but it would cost a whole lot more (and require a huge amount more mass / volume) than just doubling the fuel tankage of your missile(s).

"Jumping" to engage a target pretty much eliminates the possibility that the target is mobile, so this is really only applicable for engaging fixed defences.

Scott Martin
 
Just looking at a few numbers (and my limited recall of trig), you would get 99+% of your velocity imparted with a 2 degree separation angle. And, you would have to launch your rocks at 1/4 AU from the target (assuming Earth, and you are shooting at something at the top of the 100d limit, while planning on skimming the bottom 100d limit).

What am I missing?

The ship design would have several Gs of rotation. (And, the ships personnel live in the non-rotating spindle at the middle.) It would seem that all I have to do is get them going at a slight tangent.... The idea is a long duration ship does the accelerating (slowly so as to not alarm any sensors) at an oblique angle to the ecliptic from WAY out there. There is a tanker at the origination point (most likely deep space) and one at the destination. As soon as the missiles are away, the ship jumps out (skimming just outside the 100d limits).
 
Hey Fritz

Maybe your comment has confused me: are you trying to impart velocity from the base velocity of the ship, or from the ships rotational velocity?

If you are trying to impart velocity from the ship, then just jump in with a bearing directly towards your target (since you somehow know where it is a week in advance) drop the KKM's and jump back out.

If you are trying to get the energy from rotational velocity then you are trying to get all of your velocity released in a very short time frame: in this case, by having a spinning object be released.

Centripetal accelleration is (Vt^2)/r or (w^2)r (Vt being tangential velocity, w being angular velocity)

Assuming that you have a diameter of 100m (a pretty big ship) then the centripital accelleration being experienced by your "spinner" to get 1 hex/turn velocity (16 2/3 km/second, fairly low...) will be (16,667 m/s* 16,667m/s)/100m or 2.7 million m/sec^2 (aka around 300,000 G's)

To get the same velocity a KKM needs 1 G for a half hour. (this would be where I notice that BL scales are shot, since 1 G (9.81 m/sec/sec) for a half hour is 17,658 m/sec, while 30,000 km/half hour is 16,667 m/second. actual KKM impact energy just went up by over 10%...)

I cannot imagine building a ship hull designed to take 300,000 G's of loading, and this would also make it impossible to turn (the mother of all gyroscopes) The alternative would be to put more fuel on your KKM. (or perhaps we are having an even more basic disconnect: my "rocks" have engines and steering, so I don't need to accellerate them)

The "Ultimate" KKM would be a really big pile of fuel on a small platform fired a loooooong way out (perhaps even another star system) this gets around any FTL restrictions (IYTU) and is one of the scenarios planned for my players once I kick off my new campaign.

Scott Martin
 
A Collision Modeling update for Whartung

The two extremes for energy transfer alternatives look like they will be an almost "elastic" collision (drilling a sand-grained hole through whatever it hits: this is as close to the "elastic" end of the collision as you can get) to a completely "inelastic" collision where the sand grain "sticks" to the target, momentum is conserved and the remaining energy is converted to heat or structural deformation.

An example for a 1 mg grain striking a 1 metric ton target at 30 kilometers per second. (I'm putting final mass at 1,000 kg, instead of 1,000.001 kg since I'm using WAY less than 7 significant figures for this)

resultant velocity: 0.03 m/sec
resultant energy: 0.9 J (negligible)
remaining energy: 900 kJ

Specific heat of water is 1, specific heat of steel is in the 0.11-0.12 range so assuming no deformation the target is heated by about 8,000 degrees K Since Iron melts at 1188K and boils at 3134K, a perfectly inelastic collision would be expected to convert a 1T slug of iron into expanding hot gas. If your "magic armour material" has a specific heat equal to that of water you are "only" heating it 900 degrees, so if it starts at an average temp of 0 C (Ice) this is still enough energy to heat it to steel melting temperature (NB most steels will melt below Iron melting temp, due to eutectic effects).

I think that a collision at these velocities with *anything* would result in munitions mission kill.

I also suspect that you would have trouble finding any remnants of the sand grain


Scott Martin
 
Scott,
The reason for the tangential firing is so that your ship can jump without further maneuvering - it will miss the 100D line around whatever body your targets orbit (or are on). The ship comes in off the elliptic, accelerates stealthily to an outrageous speed, then changes the vector for the missiles by turning them slightly (the ship is coming in like a rolling pin to dough, not pointy end first) and giving them a little extra kick.

</font>
  • Assumptions:</font>
  • N-space velocity must be in the same direction as your jump</font>
  • Any jump through a 100D limit will precipitate you from J-space (or a misjump)</font>
  • Lower the accel, the harder it is to spot</font>
  • Further out means harder to spot accel</font>
  • Velocity is not a trait that makes you easier to spot</font>
I see what you are saying, though: to impart the velocity you are talking about, I would need an unreasonable amount of spinning (I don't mind the gyro effect - no real manuever going on here). Do I need to impart that velosity, though, as I am not creating a very large tangent?
 
Fritz:
You need to hold together against that stress... the ship would likely disintegrate from the centrifugal forces well before you reached the useful tangential speed.
 
Hey Fritz

Why not just point your ship directly at the target, launch at say 110 D and then jump before hitting the 100D limit?

You can't do this IMTU, but it's a lot more straightforward.

The calculation of centripital accelleration above was the amount of spin your ship would need to give a 1 G-Turn "nudge" to your missile (fired off the "rolling pin") so if your ship is doing the spinning you're a thin jello paste (300K gravities at the hull of your ship) assuming that the ship can actually take that. Since the best (read "scariest") centrifuge that I have worked with went to a mere 10,000 G's and was made of a fancy titanium alloy, I can't see anything made of anything that we would call "matter" surviving this.

Sometimes the simple solutions are best...

Scott Martin
 
Originally posted by Scott Martin:
Why not just point your ship directly at the target, launch at say 110 D and then jump before hitting the 100D limit?
Mainly because you would (IMTU) pop right back out of jump at the 100D limit when you encountered it. (I assume you mean by going directly at the target....)

I can see your point about the G's required. (Though my crew would have been stationed in the non-rotating spindle.)

Back to the drawing board... :rolleyes: :(
 
That's still fine: you'd pop back in *a week later*

The target should have suffered a bad case of the "booms". You can then pass on through to the other end of the 100D limit, and jump "home"

Just make sure that you have a decent fuel reserve ;)

Worst case you pop back in and the target is still there, at which point you hope you have a *lot* of velocity to clear through before they get their weapons cycled up. You can still punch the J-Drive within 100D, if it's a choice between guarenteed dead or misjump / maybe dead.

Scott Martin
 
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