主题：【讨论】MD整出电磁炮了。谁给帮忙算算。 -- 小楼飘香的马甲

33000000x2/1700 /1700=22.8Kg。

不过这篇新闻里说，弹头重20磅（大约9Kg），飞行速度是7倍音速。算下来也是30MJ左右。

按这个新闻的说法，他们的设想是这个炮在击中目标的时候速度下降到5倍音速左右,那样的话最后的碰撞动能大概是13兆焦耳。

wikipedia上说

9 MJ is enough energy to deliver 2 kg of projectile at 3 km/s–at that velocity a rod of tungsten or another dense metal could easily penetrate a tank, and potentially pass through it.

2千克重的钨合金弹头在3000m/s的速度下就能洞穿坦克了。

做个比较：美国120mm尾翼稳定穿甲弹M829A2，炮口速度是1680m/s（5倍音速）,穿甲部分重4.74 kg,穿甲部分的炮口动能是6.7MJ。

（不过实际上火药推动的是弹托＋长杆穿甲弹身，这俩合起来重约8Kg，所以整个抛射物的动能大概是11MJ。）

说明一下,长杆穿甲弹的穿甲部分重量不大好查，上面给的这个数字来自于一个坦克论坛，那里有人引了这样一段话：“Hon. J. Kyl, US Senate, letter to Mr. Jack Cohen-Joppa, 14 July 2003. The letter from Senator Kyl states that the tank rounds shot by Army tanks were M289A1, which may be inaccurate given that M829A2 rounds are currently in the US arsenal. The M829A1 has a DU penetrator weight of 4.64 kg; the M829A2 has a penetrator weight of 4.74 kg. A.H. Passarella, Director, Freedom of Information and Security Review, Office of the Assistant Secretary of Defense, letter to Mr. Dan Fahey, “Technical Response to FOIA Case Number 97-F-1524, Question Eleven,” 11 February 1998.”

• 所以这个逻辑是