ship's lasers

[Scott Martin]

Well the TNE assumption is that (Grav Focused) lasers are 20% effective, and that the energy is delivered to a 1 cm&sup2 area in "Effective range". I could do the "10 shots/turn" conversion and get the correct number of MJ from that, or we could just go with "Holy crap, 50 MJ/second delivered to a square centimeter area!"

that's going to cause a lot more grief than to "warm up a broad area of a ship's hull"

It also makes me wonder if insanely low density armour would be the way to go: 20m of foamed aluminum would probably be more effective at absorbing a high energy laser than a few cm of hardened steel, both due to diffraction caused by the ejecta plume and the minimal radiative transfer across the material. A "Powder Snow" comet would have similar effects, but with WAY higher beam energy losses due to phase transfers.

One of the things that I find somewhat ironic is that the killer high energy weapons (KKM's, X-Ray Lasers etc) will probably have relatively minor effects on merchant shipping, especially "empty" merchant shipping. An X-Ray laser will have very little interaction with a minimum-thickness hull and "air" or "LHyd" (or even something low-density like grain: popcorn anyone?) while a KKM will probably punch a neat entry hole, a neat exit hole and continue on its way. Heavy armour in both of these cases will probably give effects similar to those in Napoleonic era men of war, with hull splinters causing horrific secondary damage. Heck, even a PAW would probably punch right through a civvie hull with very minor secondary radiation effects.

Of course all bets are off if the beam / projectile path goes through something "sturdy" like the main reactor, but in those cases a warship also tends to be a lot more "dense" than a merchant, with more "sturdy" things in the way...

Scott Martin

 

[TheEngineer]

Well, you've not only got to hit, you've got to hit, where it hurts

Considering the data Anthony supplied (thanks !) the x-rays seem to be quite soft anyway, just 12 keV (factor 200-300 in lead), thus only surface active in massiv objects.
Regarding the KKM impact I found a pretty picture:
Micrometeorite Impact
Just lets think a little bigger....)

Regards,

Mert

 

[Pickles]

Originally posted by TheEngineer:
Regarding the KKM impact I found a pretty picture:
Micrometeorite Impact

Nice ... so, layered armour would be the way to go, even with lasers if they only cause surface damage. Same effectiveness as thick foamed alloy, but probably easier to repair.

Ok, [/OT], I'll let you guys get back to lasers, I'm taking notes ...

 

[TheEngineer]

Besides, thick foamed aluminium would make a pretty show if exposed to laser fire and enough oxygen...
Hmm, or think of a hit reentry

 

[Ptah]

Originally posted by Scott Martin:

It also makes me wonder if insanely low density armour would be the way to go: 20m of foamed aluminum would probably be more effective at absorbing a high energy laser than a few cm of hardened steel, both due to diffraction caused by the ejecta plume and the minimal radiative transfer across the material. A "Powder Snow" comet would have similar effects, but with WAY higher beam energy losses due to phase transfers.

Scott Martin

A good idea. Foamed aluminum may also be a renewable armor, e.g., applied through fixtures on the hull (foam guns) and/or outlets so it can be pumped out. May be able to use tricks like charging the hull to get it to spread out and stick on the hull.

The ejected material may also serve as chaff. I'd imagine the aluminum powder to have a huge radar cross-section. Maybe not a great thing in space-combat but a good thing for those drop pods (ala Starship Troopers the book).

Scott, do you really mean 20 meters?

 

[Scott Martin]

Yup, I was talking *meters* of armour. Obviously for unstreamlined craft only, but the actual density of this type of armour is ridiculously low. You can also play "shell games" making your opponents guess where your *real* center of mass is: a heavy weapon won't kick off secondary fragments (material density is too low) so if it doesn't hit your main hull it should pass right through.

Specific Gravity (Density of) a near-vaccum foam could probably be pushed below 0.05 with current technology (~100 parts low pressure gas for each part aluminum) so that "20 meters" of armour would only mass the same as 12.5 cm of steel. Gravitic tech would let you be very specific about the matrix formed, so I would expect the density to go down, possibly by an order of magnitude, while the structural (ablative?) strength stayed in a similar range. A lot of the effectiveness of this type of armour on lasers would be taking advantage of the "plume" concentrated on the incoming beam to disrupt the (local) focus of the beam. This doesn't work within centemeters of the diffraction point, but I think that it would be effective at spreading the beam focus over tens of meters of distance. The laser would chew a "cone" through the armour, probably based on amount of diffraction (again based on wavelength) so this type of armour would go "out of vogue" with X-Ray lasers unless some hideously dense material was used (foamed superdense?)

Since Jump is based on volume, not mass, this would be a trick for system defence craft only.

Of course "foaming gear" would allow you to carry a 50T small craft and "bulk it up" enough to be jump-capable (using CT rules) Give the modular cutter a "jump" module: +20 T of fuel, 2T small stateroom, 3T J-Drive, 1 T foaming gear. Instant J-2 conversion for getting help when you suffer a jump malfunction.

Foamed metallic armours would sort of redefine "ablative" though...

Scott Martin

 

[Anthony]

Depending on beam dwell time, foamed aluminum might be useful or it might be totally worthless. If lasers cause secondary blast effect, foamed aluminum would absorb them. However, if lasers actually use a pulse chain to drill through armor, foamed aluminum is compressible and can be pushed out of the way by vapor pressure, which would make it very poor armor.