Newtonian Aurora

[Mel Vixen]

Uh, gravity tolerance is the same as g-force.  Gravity is acceleration.  

A species that is adapted to life on a large earth-like world with 7g gravity can build ships that go at 7g accelerations without meeting any biological limit.  
No species would have any trouble on a ship accelerating at less than it's homeworld gravity.  

It's the question of how much *higher* than homeworld gravity can a species survive that can have variance.  
Although it is obvious that higher-G races would cope better with higher accelerations.  I dunno, guess it might be proportional?  1G races might have an average tolerance maximum of say 1.6Gs for long periods and 10G races might have an average tolerance max of 16Gs for long periods.  

But a worlds gravity does necesserely mean that a species is able to survive its own homeworlds gravity respective a certain acceleration. Take a whale, out of the water most bigger whales crush themselves say if they are stranded. Then there are trees, most wouldnt withstand a accelartion of 1G in any direction except "down".

What i try to say is that we shouldnt think that a planets g-force determines strictly what kind accelerations a Alien species can withstand altough it might be a factor. I mean there could be even 0G species especially if a world has a thick supportive medium like water or Atmospheres with high pressures.

@byron: Wouldnt the mouse survive because its acceleration plus its weight wouldnt create a impact-force that is big enough to harm it? The terminal velocity of the mouse wouldnt exceed its actual acceleration tolerance.

[UnLimiTeD]

At these velocities the projectile will very violently explode, I think that it will have a decent spread rate. It can also be handwaved as not only the area of the ship that is physically touched by the projectile, but also that is destroyed by the shockwave of the armor being pushed out away from the projectile to make room for it.

However, at this speed, say, an impact speed of "just" 1000 km/s, the projectile would also take just one tenth of a millisecond to pass the entire ship.

As far as i know, and I openly admit that I really don't, the detonation velocity of a strong nuke is at best half that.
So, if you hit the target with a metal ball large enough to penetrate both sides of armor if it would not disintegrate, the lowest speed that still achieves that would have the most devastating effects, destroying the ship.
Go too fast, and the shell exits the other way before expanding enough.

For example, if we calculate shell expansion at 750 km/s in an airlike atmosphere, which I think is pretty generous, then if the impact speed is above 2000 km/s, the effect would diminish.

Interesting, more power might not always be better.
As for the G question, that would mainly mean that if a whale was to jump into space, it would require a heavier ship to contain water, and have a lower max acceleration?
Isn't that also a question of size, as with the mouse?
Currently Aurora only models beings of roughly humanoid shape....

Also, it should be mentioned that the ideal gravity for a being isn't necessarily the one you get on your homeplanet.
Humans would probably function better at 0.95 g.
The problem so many people get back problems while aging is that our spinal column, more precisely our intervertebral discs, aren't made for this kind of strain, especially not over the life span we experience.

However, one could use a very slow acceleration during cruise as means of artificial gravity.^^

[jseah]

Whales and aquatic life would of course require their supportive mediums.  In their natural environment, it should be obvious that life would survive at accelerations equal or below its homeworld gravity.

[Yonder]

So, if you hit the target with a metal ball large enough to penetrate both sides of armor if it would not disintegrate, the lowest speed that still achieves that would have the most devastating effects, destroying the ship.
Go too fast, and the shell exits the other way before expanding enough.

My method actually does capture that affect.

[UnLimiTeD]

However, in that case we need to calculate the energy that the shell actually has at those levels, instead of just assuming everything it touches is destroyed.
Also, taking this reaction to shields would result in smaller rounds "harmlessly" exploding on the armor even though half their energy might actually penetrate.

[procyon]

However, at this speed, say, an impact speed of "just" 1000 km/s, the projectile would also take just one tenth of a millisecond to pass the entire ship.

As far as i know, and I openly admit that I really don't, the detonation velocity of a strong nuke is at best half that.
So, if you hit the target with a metal ball large enough to penetrate both sides of armor if it would not disintegrate, the lowest speed that still achieves that would have the most devastating effects, destroying the ship.
Go too fast, and the shell exits the other way before expanding enough.

For example, if we calculate shell expansion at 750 km/s in an airlike atmosphere, which I think is pretty generous, then if the impact speed is above 2000 km/s, the effect would diminish.

Interesting, more power might not always be better.

I doubt we would actually see any projectile survive.  In fact, I would tend to design the projectiles just so they didn't.  No one designs bullets/shells/etc to pass through the target and waste the energy.

Copper works just fine punching through several inches of armor on the M1 when used in an IED.  The detonation of the 'bomb' turns it into a molten fragment/EFP that simply cuts/burns its way through the armor.  Once inside the tank the (now even hotter after punching through the armor at a few km/s) penetrator and armor both violently expand and essentially sets the atmosphere in the vehicle on fire.  Its not pretty - but unfortunately very effective.  This happens at about 3km/s.

We are talking about things moving (on the slow end) in the tens of km/s.  Remember when Steve gave his little equation on rail guns that said energy of the projectile is proportional to the square of the velocity...
Even at 10km/s, perhaps three time what the IEDs in the Middle East manage - we have nine time the energy.  And I have been to sites and seen where those chucks of copper have cut through over 4 inches of the most advanced armor we can field today.

At 100km/s - we are talking about 900 times the energy.  If three km/s liquified copper, 100 will turn it and the armor to vapor.

These projectiles - as they strike the vessel - just created an amount of energy that rivals a small nuke.  The projectile didn't survive.  Neither did the armor it hit (assuming penetration).  Both have now been heated to temps that I am sure (haven't done the math, but don't think it is really necessary on this one) turned them into a gaseous state.  If the structure/atmosphere in the vessel is at all reactive/combustible - it just became a bomb along with the violently expanding material of the penetrator and armor.  The shock wave of the expansion should tear apart the inside of the structure - just like a bomb.  And if it turns into a gas - the rate of expansion won't make much difference on penetration.  It won't go out the other side (ok, some will as it tears the ship apart), it will impart this energy to the structures/air around it.  Kind of like shooting a milk jug with a fragmenting bullet from a rifle.  The bullet doesn't just pass through - the milk jug explodes from the shockwave.  It is called hydrostatic shock.  With the energies we are assuming the remains of the projectile and armor will do just fine to carry the shockwave - with any air in the ship adding insult to injury.

Any ship expecting combat should be evacutating all the atmosphere early to limit this.  It would lessen the medium for the shock wave.  Probably wouldn't save the ship - the energy it will be absorbing is just going to be too much.  But might help.  Maybe.

And as for the 'impact' spreading on armor - maybe if the armor stopped it.  Everything I have ever seen looks like a hole cut right through.

And on the thought of skipping armor on designs, I agree.  Every bit of weight is that much less acceleration/delta-v I will have.  Even today - mobility is survivability.  The best advice I ever got was,
"Best way to survive, just don't get shot."  Easy to say - hard to do - but it works.  I see being unpredictable to be the best defense.  Don't be where the enemy thinks you will end up.  Don't group ships together.  Don't have them going the same directions.  Change course often.  And try to line up your ordinance so it surrounds the enemy and closes on them before they can do the same to you.  If you keep your ships together, they will be able to bracket all of them at once.  Force them to expend ordinance and fuel hunting each one.

And those life pods, if it looks bad you probably want to eject before the enemy ordinance gets to you.  If the other guy misses they can always pick up your ship when they pick up you.  If they hit, sending your life pod out into the nuclear blast probably didn't help you much....

[procyon]

And on the thought of shields, I still don't know what would happen to a projectile.  Thinking out loud here.

If there was a gap of perhaps half a meter give or take, it might make a difference.  Not really sure.

The slug may vaporize before impact if the shield can impart enough energy to the slug.  In that case it might act as a whipple shield and help to disipate the blast.  But a whipple shield works on the principle of dispersing the energy of a small projectile and distributing it over a larger area that can survive that level of energy.  That won't likely apply.  If you have really thick armor and the slug didn't have huge amounts of energy - maybe you could survive.  But the ship is still going to have to absorb an amount of energy that will likely be enormous.  Too much most likely.

Maybe you could spread it out over a wider patch of the surface, but I am just afraid that the level of energy involved is still going to tear the target apart.  It just won't matter if the slug turns into a vapor or not.  Even if it is a gas - the energy has to go somewhere.  Air is a gas, and does a fine job transmitting energy from explosions to the target.  If the slug becomes a gas, it will just become the atmosphere transmitting the shockwave to the ship.  If the shockwave contains too much energy, the structure it strikes will still suffer the effects.

No, I just don't see the shield saving the ship unless it can really soak a lot of the energy.  May change how the ship was destroyed, but that is all.

But I really have no idea how the 'shields' work, so this is all open to wide interpretation.

[UnLimiTeD]

Well, there is a section in Steves thread showing the mechanics, even though assuming much slower impact speeds.
Appearently, the Shields radius is 10% larger than the ships, so size could actually protect you, as with a ship 100m in diameter, you shields will bring 10m distance between you and the slug.
As for armor;
You'll want some, or the enemy will just flay you to death with heavy pulse lasers.
Or fire a few shrapnel warheads, at a fleet speed difference of 500 kps, having a few hundred cubic meters filled with 50 gram metal pellets could prove devastating to unarmored targets, and as a screen might actually disintegrate the shells fired at you.
So maybe, combat including projectile weapons would start by "deploying your armor" in the form of more projectiles.
And what will happen to the particle beams we have in Aurora?
Are they essentially projectiles with limit range, but undeflectable?^^

Crap, there's so many potential possibilities.

edit, fixed a typo

[PTTG]

Good point; armor won't protect you from big things, but it will prevent an Ewok victory. (Sticks and rocks beating lasers and force fields.)

[Yonder]

Yeah, if your armor doesn't have the ability to block the spread out energy, then Whipple shielding (physical or otherwise) will just hurt you more, spreading out the path of destruction that a projectile weaves through your ship.

If the projectile has the energy to pierce through your ship, then you want it to do so while leaving the smallest possible hole.

[UnLimiTeD]

It will explode inside the ship, that's the entire point.

[Yonder]

It will explode inside the ship, that's the entire point.

I'm assuming that was directed at me?

Yeah, but the explosive cloud doesn't magically fix itself to the position of the ship. The explosive cloud will continue to move through the ship at tens of kilometers a second, passing through the other side, and taking all of that extra kinetic energy with it.

The same thing will happen with a whipple shield, but the projectile will start exploding 10 meters (or whatever the specific number is) outside the ship, so when it impacts the ship proper it will be traveling through a (slightly) larger cross-section of the ship, and as it passes through and out of the ship it will continue to affect a (slightly) larger cross section of the ship.

[UnLimiTeD]

What we have to keep in mind is that the shield also takes a bit energy off, but while it's currently a fixed amount, I'd advocate it to be a smaller fixed amount of point strength, and a small %, so it's the same effect when the projectile is exactly point strength.
Because, if the projectile disintegrates, it will expand, and thats not only sideways.
A small part will go faster, but a more noticeable part will go slower ("backwards" doesn't really fit if it's still going at speeds in the 100's of kps), and with 10m difference, if expect it to expand 1/3 of the projectile speed for now, that'd be an area of nearly 7 squares that the shell is spread over, with probably a fourth of it's kinetic energy already scattered away.
Nonetheless, I agree it would obliterate the ship it hits, the Energy is just too high.
Then, we must model several other things:
1. The integrity of the slug dictates the maximum acceleration it can take, go to fast, it'll break in the launcher, limiting range.
2. The expansion speed of the projectile doesn't scale with the impact speed, but is influenced by it, and by the object it hits.
--> This might create the odd situation where moving so fast you'd be oblitered can be counted by moving faster, as the projectile would then detonate behind the ship.
If your Impact speed is 5000kps, and the ship is not heavily armored, but contains internal bulkheads, the shockwave would be small compared to the actual projectiles energy.

Main question: If attacked by kinetic energy projectiles, should we have shields on or off? Does it depend on the speed (I think so)?
Ultimately, deploying a pebble screen seems like the best option to me.

[bean]

Copper works just fine punching through several inches of armor on the M1 when used in an IED.  The detonation of the 'bomb' turns it into a molten fragment/EFP that simply cuts/burns its way through the armor.  Once inside the tank the (now even hotter after punching through the armor at a few km/s) penetrator and armor both violently expand and essentially sets the atmosphere in the vehicle on fire.  Its not pretty - but unfortunately very effective.  This happens at about 3km/s.

We are talking about things moving (on the slow end) in the tens of km/s.  Remember when Steve gave his little equation on rail guns that said energy of the projectile is proportional to the square of the velocity...
Even at 10km/s, perhaps three time what the IEDs in the Middle East manage - we have nine time the energy.  And I have been to sites and seen where those chucks of copper have cut through over 4 inches of the most advanced armor we can field today.

At 100km/s - we are talking about 900 times the energy.  If three km/s liquified copper, 100 will turn it and the armor to vapor.

This is not right at all.  First, IEDs are generally not shaped charges.  They're bombs.  An RPG-7 can't penetrate the frontal armor on an M1, and it's going to have a much better warhead.  Second, the speed of a shaped charge jet tip is on the order of 7 to 14 km/s, not 3 km/s. 
And just so we're clear, energy is always proportional to the square of velocity.

[Yonder]

Nonetheless, I agree it would obliterate the ship it hits, the Energy is just too high.

We can't just say that it will obliterate a ship it hits, because many hits won't do that, depending on relative velocities we could have slugs 'gently' tapping ships at a few handfuls of km/s. We need to do our best to come up with a damage model that will handle this scaling up.

I also argue that once we start implementing this damage model we may very well find that ships don't get obliterated for really fast slugs, because so much of the kinetic energy will escape out the back. I'm not saying that it will be pleasant for the ship, after all there will be a small hole at the front, a medium hole on the inside, and a large hole on the opposite end of the armor, but if it's a large ship it may just be crippled, not killed.