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VB6 Aurora > Newtonian Aurora
Impact Physics
Steve Walmsley:
I haven't rally given much thought to the projectile shape. I assumed something like those fired by the US Navy Railgun, or a modern day APDS round
Steve
Mel Vixen:
Well one can make some assumptions right? You [edit: i mean byron] say at high enough velocities our projectile turns to plasma, wouldnt that have a initial damage-profile compare-able to a very intense laserpulse due to the energy imparted on projectile and targed? Iirc some kind of Shockwave traveling through the matter or something?
fcharton:
If the projectile turns to plasma, then you could consider that most of its kinetic energy is turned into heat and consider most/all damage results from two causes : electromagnetic shock and heatwave.
I'm not sure how one would calculate the electromagnetic shock, but we discussed the heat aspect with Yonder in the NA thread. Assuming a specific heat for the projectile and a speed will provide an impact temperature. Heat transfer equations would then define an expanding sphere of decreasing temperature, which, if you cut it to some "tolerable level" would sort of define the radius of the "hole" the projectile would melt in the ship.
This said, I wonder whether the "turn into plasma over 30 km/s" rule applies in space. Air friction, and pressure, play a considerable role in heating fast moving objects. Would the same happen in space?
Francois
bean:
--- Quote from: fcharton on January 27, 2012, 12:12:56 PM ---If the projectile turns to plasma, then you could consider that most of its kinetic energy is turned into heat and consider most/all damage results from two causes : electromagnetic shock and heatwave.
I'm not sure how one would calculate the electromagnetic shock, but we discussed the heat aspect with Yonder in the NA thread. Assuming a specific heat for the projectile and a speed will provide an impact temperature. Heat transfer equations would then define an expanding sphere of decreasing temperature, which, if you cut it to some "tolerable level" would sort of define the radius of the "hole" the projectile would melt in the ship.
--- End quote ---
Yes and no. The projectile is likely to turn into plasma on the whipple shield, which would reduce damage because the plasma would spread out before it hit the main armor. I think that the remaining momentum of the plasma and fragments would do the most damage, not heat transfer. Also, specific heat is not constant for a situation like this.
--- Quote ---This said, I wonder whether the "turn into plasma over 30 km/s" rule applies in space. Air friction, and pressure, play a considerable role in heating fast moving objects. Would the same happen in space?
Francois
--- End quote ---
Absolutely. The plasma is not due to atmospheric heating. It's what happens when something is under pressure in the gigapascal-terapascal range that then gets released.
--- Quote from: Heph on January 27, 2012, 11:46:39 AM ---Well one can make some assumptions right? You [edit: i mean byron] say at high enough velocities our projectile turns to plasma, wouldnt that have a initial damage-profile compare-able to a very intense laserpulse due to the energy imparted on projectile and targed? Iirc some kind of Shockwave traveling through the matter or something?
--- End quote ---
Maybe. The problem is that the plasma is produced at the whipple shield, then expands to hit the hull itself. So it's less like a laser pulse, and more like a conventional explosion.
--- Quote from: Steve Walmsley on January 27, 2012, 11:17:28 AM ---I haven't rally given much thought to the projectile shape. I assumed something like those fired by the US Navy Railgun, or a modern day APDS round
Steve
--- End quote ---
That would be a long rod. As an addendum, the projectile virtually has to be guided. If it doesn't hit straight on, then it loses most of its penetration.
fcharton:
Hi Byron
--- Quote from: byron on January 27, 2012, 01:21:06 PM ---The projectile is likely to turn into plasma on the whipple shield, which would reduce damage because the plasma would spread out before it hit the main armor. I think that the remaining momentum of the plasma and fragments would do the most damage, not heat transfer. Also, specific heat is not constant for a situation like this.
--- End quote ---
How would the whipple shield work, then? I mean, for what I understand, modern day shields work for very light objects, with speeds in the tens of km per second. We're talking here of something weighing about a kilogram, colliding at a speed ranging from 100 to 1000 km/s.
At 100km/s, energy is 5 GJ, at 100, 500 GJ. Which means even if one percent of energy turns into heat, we get temperatures around a hundred of thousand kelvins, probably even millions for the faster projectiles... Wouldn't the whipple shield need to be very far from the ship to protect it from this kind of thermal shock?
I was asking that because it seems to me that over a certain energy, radiation output dominates (because its strength increases as a large power of the temperature, fourth if memory serves, and because it moves at lightspeed).
I might also be totally wrong (this wouldn't be the first time).
Francois
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