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[Tack]

I feel like mercury phosphate could contribute slightly to the "powder-mad veteran" bit.

[Strife26]

So, I've seen lots of people here say KKV could outperform antimatter as far as the amount of energy delivered goes. How does that make sense? Antimatter warhead impacting would (assuming 100 % anihilation) produce 2mc² worth of energy, where m is the antimatter mass. By definition, a KKV going at c will have a kinetic energy of mc²/2, where m is the kkv mass.

Probably a combination of talking out of their ass and the assumption that a KKV can deliver lots more mass than antimatter because the antimatter warhead needs some kind of containment system.

[Culise]

Plus the difficulty of near-instantaneous 100% annihilation.  You can't just lob a block of antimatter at something and expect it all to detonate right on the spot; the second it comes into contact with matter, the points of contact will mutually annihilate first, creating a tremendous force pushing the block back off said matter.  An antimatter warhead may well end up being half-matter and half-antimatter rather than using the target as a matter source (capped at 1mc² worth of energy), just so that you can arrange the matter and antimatter inside the warhead to ensure a significant amount of the destruction occurs right when and where you want it, and that is unlikely to include containment or structural systems.  You also have to include the fact that an M-AM blast will include a lot of neutrinos, which will do sweet-fanny-adams to anything in this realm; it wasn't quite as big of an issue in the hypothetical pure-AM warhead (unless said ship outmasses your warhead), but it is once you start working with more practical M-AM warheads.  I've found estimates of anywhere from the 100% optimum to as low as 44% of the energy being effective at destroying your target, with a WAG estimate of around 70%-85% being the norm.

That said, the approximation of kinetic energy you used also only operates in classical domains.  Relativistic effects do interesting things to extremely fast KKVs (hereafter referred to as RKVs), and you have to use a more general equation:

KE = mc² - m₀c²

where m₀ is the rest mass and m is the relativistic "mass."  In particular, a very special point apparently exists when you're traveling at 86.6% of the speed of light where the amount of kinetic energy is equivalent to the rest mass: in other words, your RKV now contains the equivalent "boom" of a pure-antimatter weapon of the exact same mass.  If you keep going, the rest is essentially gravy. 

That's not to say RKVs are all gravy, though; overpenetration is the obvious issue.  While a pure-AM reaction will try to push away from the target, an RKV has enough velocity that it's going to try to go right on through it and out the other side.  That's obviously not entertaining for anything on or near the direct line of motion, but most of the rest of the ship will likely survive such an event just fine unless something really important and explosive (say, an M-AM power reactor) gets hit.  So, the big answer is: it depends.  How effective of an AM-burst can you engineer?  How well can you design your RKV shell to handle overpenetration?  Moreover, for practical use, is it cheaper for you to create that much energy (plus waste due to inefficiencies in the firing mechanism) to fire a relativistic shell every time you fire a weapon or is it cheaper to mass-produce antimatter and store it until used? 

[Helgoland]

You could store the energy for the KKVs in the form of antimatter

[Culise]

You could store the energy for the KKVs in the form of antimatter

Yes, you certainly could.  It's much easier to create an efficient M-AM reaction when you don't have to accomplish your mixing on extremely short timescales.  The question then becomes if the inefficiencies in getting that power into moving your RKV warhead outweigh the inefficiencies of using said antimatter as a weapon directly. 

[Amperzand]

If the accelerator can get the projectile above .866c without using too much antimatter to do so, I guess.

Incidentally, it's worth noting how chemical bonds behave at high velocity: Above 10km/s, solid matter behaves as a liquid, for purposes of impact physics. Above 100km/s, matter behaves as a gas, for purposes of impact physics. At high relativistic speeds, matter basically behaves like the compressed globs of energy it is, and will go all over the place with considerable eagerness.

It is worth noting that while overpenetration is a thing, it's less of an issue when your projectile hits hard enough to force nuclear reactions in the target. At those energies, even if the expanding cloud of very, very hot subatomic ash that was originally your impactor and everything in its path does make its way out the other side of the target, the radiation and secondary blast effects will cause widespread damage to any vessel of reasonable size and internal structural characteristics.

Additionally, dumbfire kinetics can be considered largely useless against spacecraft at long range (>1 light second), unless the impactor is moving at very nearly c, and even then guidance is advisable. Most kinetic weapons should be missiles with the armor protecting them against enemy point defense constituting their "warhead", potentially given an initial burst of acceleration using a coilgun or something.

(Yes, guidance electronics can survive coilgun launch, they're developing them today, let alone in the far future.)

[Tack]

I was wondering what kind of gyros a walker would need in order to self-adjust it's stance?

Old school I had the image of a bow-legged bot with a big ball filled with fluid and sensors swinging undermeath it. I just realized that idea was pretty obscene so wanna find something else.

[Rolepgeek]

Rotation wheels and internal gyros always help.

[Amperzand]

Gyrosabilization wheels help, but they don't really apply that much force, AFAIK.

[GiglameshDespair]

I was wondering what kind of gyros a walker would need in order to self-adjust it's stance?

Old school I had the image of a bow-legged bot with a big ball filled with fluid and sensors swinging undermeath it. I just realized that idea was pretty obscene so wanna find something else.

"Remember, lads - to kill a mech, aim for the balls!"

[Fniff]

Hello folks, in a thing I'm working on, the ozone layer is mostly gone.
Since most objects in space are invisible thanks to the ozone layer, would they become visible if ozone was depleted? And what objects would be visible to the naked eye? Would the night sky be visibly brighter?

[Amperzand]

The ozone later doesn't do much to visible light afaik, mostly the higher wavelengths. If you could see into UV there'd probably be a neat view.

[Fniff]

Aw, shame. Would have been a neat moment. Thanks anyway!

[tonnot98]

Can we make a theoretical weapon?

Like, can we kill someone with a theory? A legitimate infohazard?

[wierd]

Economic theories have killed lots of people.