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MAC cannon projectile speed?

OP A Fire Walk

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I was only able to found the 600,000 m/s number... But that is twice the light speed. Is that canon?
The speed of light is 299792458 m/s, not 600000 m/s. You are probably mixing up km/s and m/s, as the speed of light is around 300,000 km/s. As for the velocity of a MAC round, it varies by MAC, but the cannon mounted on a UNSC Frigate fires a 600-ton slug at 30 km/s (30,000 m/s), while the cannon on an Orbital Defense Platform fires a 3,000 ton slug at 4% the speed of light (~12,000 km/s).
Jebsquared wrote:
The speed of light is 299792458 m/s, not 600000 m/s. You are probably mixing up km/s and m/s, as the speed of light is around 300,000 km/s. As for the velocity of a MAC round, it varies by MAC, but the cannon mounted on a UNSC Frigate fires a 600-ton slug at 30 km/s (30,000 m/s), while the cannon on an Orbital Defense Platform fires a 3,000 ton slug at 4% the speed of light (~12,000 km/s).
That 4% is still contested to this day actually.
0
To know the Lore is to know Halo
"Dont be spoiled, dont start a fight. Always be careful, here at night. Because the Spartans might come, in suits that weigh half a ton. And they'll steal from you all you gots, just like they did from Colonel Watts."
Jebsquared wrote:
The speed of light is 299792458 m/s, not 600000 m/s. You are probably mixing up km/s and m/s, as the speed of light is around 300,000 km/s. As for the velocity of a MAC round, it varies by MAC, but the cannon mounted on a UNSC Frigate fires a 600-ton slug at 30 km/s (30,000 m/s), while the cannon on an Orbital Defense Platform fires a 3,000 ton slug at 4% the speed of light (~12,000 km/s).
That 4% is still contested to this day actually.
It is? I thought it was explicitly stated in one of the original trilogy books. Either Fall of Reach or First Strike.
Those figures for MAC velocity came from halopedia, and it's usually reliable. It's more reliable than the Halo fandom wiki, that's for sure.
Jebsquared wrote:
The speed of light is 299792458 m/s, not 600000 m/s. You are probably mixing up km/s and m/s, as the speed of light is around 300,000 km/s. As for the velocity of a MAC round, it varies by MAC, but the cannon mounted on a UNSC Frigate fires a 600-ton slug at 30 km/s (30,000 m/s), while the cannon on an Orbital Defense Platform fires a 3,000 ton slug at 4% the speed of light (~12,000 km/s).
That 4% is still contested to this day actually.
So is the 30 km/s. That figure came from a damaged, pre-war Frigate that was flying backwards at the time of the shot.
Jebsquared wrote:
The speed of light is 299792458 m/s, not 600000 m/s. You are probably mixing up km/s and m/s, as the speed of light is around 300,000 km/s. As for the velocity of a MAC round, it varies by MAC, but the cannon mounted on a UNSC Frigate fires a 600-ton slug at 30 km/s (30,000 m/s), while the cannon on an Orbital Defense Platform fires a 3,000 ton slug at 4% the speed of light (~12,000 km/s).
That 4% is still contested to this day actually.
So is the 30 km/s. That figure came from a damaged, pre-war Frigate that was flying backwards at the time of the shot.
The damaged aspect of the Frigate definitely could affect the velocity of the projectile. But when considering speeds so unimaginably fast like 30km/s, the fact that the Frigate was flying backwards probably has a negligible effect on the speed of the projectile.
UNSC orbital defense platforms, Punic-class supercarriers and the UNSC Infinity mount larger and more powerful versions of the standard Magnetic Accelerator Cannon, nicknamed the "Super" MAC or the "big stick". An orbital defense platform's cannon is 802.2 metres (2,632 ft) long,[2] with the platforms present in orbit of Reach, which were among the most powerful ever built,[6] being capable of firing a 3,000-ton ferric-tungsten rounds at .04c or 4% of the speed of light, impacting with a massive amount of kinetic energy.[4][note 3] Most UNSC and Covenant vessels are destroyed by this weapon, with shielded Covenant destroyers being shattered into "a million fragments" upon impact.[28]
https://www.halopedia.org/Magnetic_Accelerator_Cannon#.22Super.22_Magnetic_Accelerator_Cannon

And for fun, I looked up equations and someone had calculated the damage a Super MAC shot would do to a planet.

Kinetic energy is related to mass and energy by:
E=1/2mv^2
This means that the energy increases quadratically with velocity. A 600,000 kilogram projectile moving at 30,000 m/s would have a kinetic energy of 2.7e14 joules, which according to wikipedia would be equivalent to a 64.5 kiloton TNT explosion, or about 4 times the energy of the nuclear weapon that razed Hiroshima.
The second projectile has a very high velocity, approximately 4% of the speed of light. Whilst pretty fast, this is actually not fast enough for relativity to have a substantial impact on the kinetic energy. Thus, solving naively, we obtain an energy of 2.16e20 joules, which is slightly over 1000 times the yield of the Tsar Bomba. The majority of this energy would be released at ground level, as opposed to the Tsar's airburst.
https://scifi.stackexchange.com/questions/24553/in-the-halo-universe-what-would-be-the-effect-of-a-mac-round-hitting-a-planet

If a Super MAC shot was fired at Washington D.C. in the US, the kinetic energy would destroy 1/3 of the continental United States. The entire East Coast would be gone with about half of the Midwest, and all of Ontario, Canada would be gone too. Also, the energy required to fire only TWO of these Super MAC shots is the equivalent of Earth's entire energy consumption in 2008.

(None of this info is my own I merely researched and put the info here)
Jebsquared wrote:
The speed of light is 299792458 m/s, not 600000 m/s. You are probably mixing up km/s and m/s, as the speed of light is around 300,000 km/s. As for the velocity of a MAC round, it varies by MAC, but the cannon mounted on a UNSC Frigate fires a 600-ton slug at 30 km/s (30,000 m/s), while the cannon on an Orbital Defense Platform fires a 3,000 ton slug at 4% the speed of light (~12,000 km/s).
That 4% is still contested to this day actually.
It is? I thought it was explicitly stated in one of the original trilogy books. Either Fall of Reach or First Strike.
It is stated "point four tenths the speed of light" in the novel, which is interpreted by the first edition Halo Encyclopedia as "0.4c", and the second edition of the Halo Encyclopedia as "nearly half the speed of light".
So the evidence suggests that "point four tenths the speed of light" is intended to mean 40% the speed of light, though worded awkwardly.
That said the literal meaning of "point four tenths" is "(0.4)/10" = 4% the speed of light.
JNDreher wrote:
Jebsquared wrote:
The speed of light is 299792458 m/s, not 600000 m/s. You are probably mixing up km/s and m/s, as the speed of light is around 300,000 km/s. As for the velocity of a MAC round, it varies by MAC, but the cannon mounted on a UNSC Frigate fires a 600-ton slug at 30 km/s (30,000 m/s), while the cannon on an Orbital Defense Platform fires a 3,000 ton slug at 4% the speed of light (~12,000 km/s).
That 4% is still contested to this day actually.
It is? I thought it was explicitly stated in one of the original trilogy books. Either Fall of Reach or First Strike.
It is stated "point four tenths the speed of light" in the novel, which is interpreted by the first edition Halo Encyclopedia as "0.4c", and the second edition of the Halo Encyclopedia as "nearly half the speed of light".
So the evidence suggests that "point four tenths the speed of light" is intended to mean 40% the speed of light, though worded awkwardly.
That said the literal meaning of "point four tenths" is "(0.4)/10" = 4% the speed of light.
I believe that the figures given in the Halo Encyclopedia were in error, as the speed mentioned in the Definitive Edition of The Fall of Reach is the same as the original
Jebsquared wrote:
JNDreher wrote:
Jebsquared wrote:
The speed of light is 299792458 m/s, not 600000 m/s. You are probably mixing up km/s and m/s, as the speed of light is around 300,000 km/s. As for the velocity of a MAC round, it varies by MAC, but the cannon mounted on a UNSC Frigate fires a 600-ton slug at 30 km/s (30,000 m/s), while the cannon on an Orbital Defense Platform fires a 3,000 ton slug at 4% the speed of light (~12,000 km/s).
That 4% is still contested to this day actually.
It is? I thought it was explicitly stated in one of the original trilogy books. Either Fall of Reach or First Strike.
It is stated "point four tenths the speed of light" in the novel, which is interpreted by the first edition Halo Encyclopedia as "0.4c", and the second edition of the Halo Encyclopedia as "nearly half the speed of light".
So the evidence suggests that "point four tenths the speed of light" is intended to mean 40% the speed of light, though worded awkwardly.
That said the literal meaning of "point four tenths" is "(0.4)/10" = 4% the speed of light.
I believe that the figures given in the Halo Encyclopedia were in error, as the speed mentioned in the Definitive Edition of The Fall of Reach is the same as the original
Exactly why I noted it was contested XD.
I don't think even 343 officially knows and they probably wont put it down permanently just so they have more wiggle room.
0
To know the Lore is to know Halo
"Dont be spoiled, dont start a fight. Always be careful, here at night. Because the Spartans might come, in suits that weigh half a ton. And they'll steal from you all you gots, just like they did from Colonel Watts."
Jebsquared wrote:
The speed of light is 299792458 m/s, not 600000 m/s. You are probably mixing up km/s and m/s, as the speed of light is around 300,000 km/s. As for the velocity of a MAC round, it varies by MAC, but the cannon mounted on a UNSC Frigate fires a 600-ton slug at 30 km/s (30,000 m/s), while the cannon on an Orbital Defense Platform fires a 3,000 ton slug at 4% the speed of light (~12,000 km/s).
That 4% is still contested to this day actually.
So is the 30 km/s. That figure came from a damaged, pre-war Frigate that was flying backwards at the time of the shot.
The damaged aspect of the Frigate definitely could affect the velocity of the projectile. But when considering speeds so unimaginably fast like 30km/s, the fact that the Frigate was flying backwards probably has a negligible effect on the speed of the projectile.
During a Warfleet livestream it was stated that UNSC ships can travel from Earth to Pluto in 72 hours. The closest Earth and Pluto can be to each other is 4,280,000,000km. There are 259,200 seconds in 72 hours. If we divide 4,280,000,000 by 259,200, we get 16,512. That's how fast UNSC ships can conservatively fly on average, 16,512km/s. Even if we assume the Commonwealth was travelling at only 1% of that speed, it still drastically increases the 30km/s figure.

30km/s also isn't very fast in terms of space combat and in comparison to the rest of Halo. If we accept 4% the speed of light for the SMAC's, that's 12,000km/s, 400 times faster than 30km/s. And that's not even getting into the inconsistent mess that is Covenant weapons speed...
Let's not forget the incredibly slow MAC round from Infinity that you guide into the Forerunner structure at the end of Reclaimer in Halo 4. Inconsistent speeds be inconsistent.
Even if we assume the Commonwealth was travelling at only 1% of that speed, it still drastically increases the 30km/s figure.
It might be worth pointing out at this point that the muzzle velocity is the speed of the projectile relative to the ship. The 30 km/s means that the distance between the projectile and the ship is growing by 30 kilometers every second. How fast the ship is moving relative to some arbitrary observer is irrelevant.
tsassi wrote:
Even if we assume the Commonwealth was travelling at only 1% of that speed, it still drastically increases the 30km/s figure.
It might be worth pointing out at this point that the muzzle velocity is the speed of the projectile relative to the ship. The 30 km/s means that the distance between the projectile and the ship is growing by 30 kilometers every second. How fast the ship is moving relative to some arbitrary observer is irrelevant.
What you don't understand is that the scene in question involves the Frigate flying backwards as it fires, not forwards. It's chapter 12 of the Fall of Reach by the way.

"The distant rumbling of the Commonwealth's main engines dimmed and stopped and she turned about. Her inertia kept the ship speeding toward the testing facility-now flying backwards."

"The MAC bolt launched through space-a red hot metal slug moving at thirty thousand meters per second."
What you don't understand is that the scene in question involves the Frigate flying backwards as it fires, not forwards. It's chapter 12 of the Fall of Reach by the way.

"The distant rumbling of the Commonwealth's main engines dimmed and stopped and she turned about. Her inertia kept the ship speeding toward the testing facility-now flying backwards."

"The MAC bolt launched through space-a red hot metal slug moving at thirty thousand meters per second."
Doesn't matter if it's moving forward or backwards. The natural reference frame of a projectile is the rest frame of the weapon that fired it. The muzzle velocity is the rate at which the distance between the weapon and the projectile grows. The motion of the frigate relative to the testing facility is irrelevant.
tsassi wrote:
What you don't understand is that the scene in question involves the Frigate flying backwards as it fires, not forwards. It's chapter 12 of the Fall of Reach by the way.

"The distant rumbling of the Commonwealth's main engines dimmed and stopped and she turned about. Her inertia kept the ship speeding toward the testing facility-now flying backwards."

"The MAC bolt launched through space-a red hot metal slug moving at thirty thousand meters per second."
Doesn't matter if it's moving forward or backwards. The natural reference frame of a projectile is the rest frame of the weapon that fired it. The muzzle velocity is the rate at which the distance between the weapon and the projectile grows. The motion of the frigate relative to the testing facility is irrelevant.
Where are you getting this from? If I was to fire a nerf gun, and then throw the nerf gun faster than the nerf itself, the nerf isn't now travelling in the negative meters per second just because it's moving away from the muzzle at that speed. And a quick google search says nothing about that.

"Muzzle velocity is the speed of a projectile at the moment it leaves the end of a firearm (i.e. the muzzle}."

The quote in the book also makes no mention of this.

"The MAC bolt launched through space-a red hot metal slug moving at thirty thousand meters per second."

Notice how it says moving at 30km/s, not moving away at 30km/s.
Where are you getting this from? If I was to fire a nerf gun, and then throw the nerf gun faster than the nerf itself, the nerf isn't now travelling in the negative meters per second just because it's moving away from the muzzle at that speed. And a quick google search says nothing about that.
Let me be clearer: the muzzle velocity is the rate at which the distance between the weapon and the projectile grows at the moment the projectile exists the barrel. Is that good for you? Of course, since in the story neither the frigate nor the projectile is accelerating after they have separated, both are moving at constant velocity, so this is the same thing.

Nonetheless, the motion of the frigate is irrelevant, because the muzzle velocity is measured in the rest frame of the frigate. That is, the muzzle velocity is the speed someone standing at the bridge of the frigate, pointing a hypothetical radar gun at the projectile would measure.

"Muzzle velocity is the speed of a projectile at the moment it leaves the end of a firearm (i.e. the muzzle}."

The quote in the book also makes no mention of this.

"The MAC bolt launched through space-a red hot metal slug moving at thirty thousand meters per second."

Notice how it says moving at 30km/s, not moving away at 30km/s.
But moving at 30 km/s relative to what? The Covenant ship? The testing facility? Chi Ceti 4?

Sure, it's true that Nylund doesn't explicitly mention a frame in which the speed is measured. But since he doesn't, the only natural frame in this is the rest frame of the frigate. Nobody would express the speed of a bullet as relative to a passing high speed train. Why would Nylund?
tsassi wrote:
Where are you getting this from? If I was to fire a nerf gun, and then throw the nerf gun faster than the nerf itself, the nerf isn't now travelling in the negative meters per second just because it's moving away from the muzzle at that speed. And a quick google search says nothing about that.
Let me be clearer: the muzzle velocity is the rate at which the distance between the weapon and the projectile grows at the moment the projectile exists the barrel. Is that good for you? Of course, since in the story neither the frigate nor the projectile is accelerating after they have separated, both are moving at constant velocity, so this is the same thing.

Nonetheless, the motion of the frigate is irrelevant, because the muzzle velocity is measured in the rest frame of the frigate. That is, the muzzle velocity is the speed someone standing at the bridge of the frigate, pointing a hypothetical radar gun at the projectile would measure.
Oh okay, sorry. I think I was still caught off guard by your first comment.
Quote:
The 30 km/s means that the distance between the projectile and the ship is growing by 30 kilometers every second.
I thought you were arguing that the MAC was only moving 30km/s away from the ship despite the fact said ship was moving at potentially thousands of kilometers per second in the opposite direction.
tsassi wrote:
But moving at 30 km/s relative to what? The Covenant ship? The testing facility? Chi Ceti 4?

Sure, it's true that Nylund doesn't explicitly mention a frame in which the speed is measured. But since he doesn't, the only natural frame in this is the rest frame of the frigate. Nobody would express the speed of a bullet as relative to a passing high speed train. Why would Nylund?
Relative to the location of the original firing point is fine. And to continue with your train analogy, my original point was that if you were to fire a damaged M1911 (muzzle velocity about 250m/s) off the back of the worlds fastest train (top speed of about 100m/s) you shouldn't then take that as the one objective example and try to claim every single gun on the planet can only fire bullets at 150m/s.

What part about that do you take issue with?
Relative to the location of the original firing point is fine.
This doesn't answer my question. "The original firing point" is uniquely defined only at the time of firing. After that it's ambiguous and depends on your choice of coordinates.

See, there's this concept of a coordinate system where you define an origin, a base point, and then at any point in time you tell where an object is by how far and in what direction it is from the origin. You can have different coordinate systems, these coordinate systems move relative to each other, and "speed" is only defined with respect to a given coordinate system.

Consider this: there is a train moving past a station. In the train there is a bottle on a table. There is a man sitting in the train. The origin of his coordinate system is where he sits. In his coordinate system, the bottle is stationary, it is not moving relative to him, the direction and distance of the bottle to him is always the same, it has zero speed. There is another man on the station. He also has his own coordinate system, where his position is the origin. Because the train is moving relative to him, and the bottle is in the train, it is moving relative to him, the distance between him and the bottle is growing, its speed is greater than zero. These two men observe a different speed for the bottle, because they are measuring the speed in different coordinate systems.

Crucially, one has to understand that there is no absolute universal coordinate system. No coordinate system is better, or more correct than another. The speeds measured by the two men are both correct. There is no such thing as the "true" speed of the bottle.

Normally, on Earth when we say something is moving, we really mean that it is moving relative to the ground. So if I say "the train was going 50 m/s", everybody understands that it was going 50 m/s relative to the ground, because that's a convention we've implicitly agreed upon. Our coordinate systems in which we measure the speeds of things on the ground are all stationary relative to each other. However, this convention hardly makes sense when we are hundreds of light years away from Earth in the middle of space, because we can't even see the ground on Earth. So, the question "moving relative to what?" becomes relevant. And the "what" has to be a concrete object. You can't say, "oh, relative to this point" because that "point" depends on your chosen coordinate system, so it's circular reasoning.

And so we get back to my question: moving at 30 km/s relative to what object in the scene?
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