Using depleted uranium weapons in medieval battle [closed]

The Vikings have journeyed far and wide, and they have discovered the secret to producing vast quantities of depleted uranium and also how to forge weapons with it.

Will the Vikings dethrone Genghis Khan as the world's most powerful conqueror or will their legacy be only one tiny pebble in the never-ending river of time?

• This question no longer meets WB.SE guidelines. It's too broad and too opinion-based. How could anyone realistically determine if the advent of a single technology - if that were even possible (it takes a lot of tech to get to depleted uranium, they're not Ghengis-Khan-era Vikings anymore) - would affect thousands of years of world history. VTC. – JBH May 12 '20 at 17:44

Depleted uranium has a few features that make it useful for modern projectile weapons:

• It's one of the densest substances known. For high-speed impacts, one of the key parameters for penetration depth is the ratio of the projectile's density to the target's density.
• It's self-sharpening. As a DU projectile penetrates a target, it tends to fracture in a way that maintains the shape of the projectile.
• It's flammable. Uranium dust tends to spontaneously ignite, and after shooting an armored vehicle, there's plenty of dust flying around.
• If you've got a nuclear weapons program, it's dirt-cheap. DU is a waste byproduct of uranium enrichment, so if you're willing to spend the money to build nuclear weapons, you get a large supply of depleted uranium essentially for free.

DU is used for armor because of the density and cost factors mentioned above.

Now, let's look at it in the context of medieval combat.

Swords, arrows, and other weapons are moving at slow-enough speeds that the strength of the material matters. Uranium isn't very good for that: it has a tensile strength of around 500 MPa and a yield strength of 170 MPa; for comparison, basic carbon steel is around 900 MPa/500 MPa, good spring steel is 1400 MPa/1000 MPa, and even bronze is better at around 700 MPa/650 MPa.

The self-sharpening ability is nice, but your arrows and swords probably aren't hitting metal often enough for it to matter.

Density? You can get some seriously effective maces that way, by concentrating a huge weight into a small area. For weapons such as swords, where strength comes as much from the shape as from the material, a denser material simply means a heavier weapon, causing the user to tire faster.

If your Vikings decide to concentrate on depleted-uranium weapons, they'll probably be remembered as suicidally-aggressive warriors who tire easily and whose weapons shatter with a good blow.

• Wait, wouldn't DU armor give soldiers cancer! – PyRulez Aug 12 '15 at 2:38
• @PyRulez, it takes a long time to develop cancer -- most Viking-era soldiers won't live long enough, even if they aren't killed in battle. – Mark Aug 12 '15 at 3:02
• I meant modern soldiers. Why would they do that? – PyRulez Aug 12 '15 at 3:06
• @PyRulez - Why in the world would DU armor give the wearer cancer? You are aware, I hope, the DU is what's left when the good stuff (U235) has been extracted (US DOD material is ~0.3% U235). A really small amount of research will let you know that the half-life of U238 is about 4.5 billion years, or just about the current age of the solar system, while U235 is about 700 million. As a matter of fact, DU is sometimes used as radiation shielding. So, why would it give the wearer cancer? – WhatRoughBeast Aug 12 '15 at 3:14
• @PyRulez, in addition, uranium decays primarily via alpha emission, and the anti-spall lining of a tank is adequate shielding against it -- as is your clothing, a few inches of air, the outer layer of your skin, or just about anything else. – Mark Aug 12 '15 at 4:23

Uranium is a very dense metal, so a sword, axe head or even spear tips and arrows would be mush heavier than standard steel models. The weapons would be very unwieldy and tiring even to carry into battle, much less use in a physically demanding bout of hand to hand combat.

If any enemy were to discover the massive weight of the weapons, their best course of action would be to feign running away and encourage the Vikings to chase them, then turn and cut down the exhausted Vikings as they tried to catch their breaths.

Perhaps the only possible advantage is the weapon would cleave through most shields and armour with a single stroke, assuming anyone is unfortunate enough to be standing in front of a well rested Viking right at the start of a battle.

Even the pyrophoric effects of DU (it self ignites at a high enough temperature in an oxygen atmosphere) only come into play when the piece of DU passes through a piece of metal at supersonic speeds and the frictional energy heats the metal to the point of ignition.

The Great Khan will have a mild chuckle as his mounted warriors ride around the exhausted band of Vikings toiling on the road to Kiev and supposed safety with the rest of the Rus....

• Perhaps the only possible advantage is the weapon would cleave through most shields and armour with a single stroke. Hmm. I wonder if you put a DU edge on a sword, would it have the same effect, but without the weight of a solid DU sword? – AndyD273 Aug 13 '15 at 13:56
• The "power" of the DU weapon would be its mass. Steel is far harder and sharper when used for sword blades and axe heads, so you would want the opposite: a core of DU with edges of steel. – Thucydides Aug 14 '15 at 1:38
• Ah, I thought it might have to do with the self sharpening thing. – AndyD273 Aug 15 '15 at 20:45
• "Self sharpening" happens when a DU dart is passing through metal armour at supersonic speeds, which is vastly beyond what a human swordsman is going to achieve with a swing. – Thucydides Aug 16 '15 at 3:57

No

Replace "actinium" with "depleted uranium." The only use of depleted uranium would be to throw it at your enemies.

• Nope. Actinum has a half-life of 21 years. U-238 has a half-life of 4,468,000,000 years. Your comment about "throwing it at your enemies" might make sense as U is very dense, but in context it sounds like you're afraid of its radiation, which you have tragically overblown. It's about as radioactive as a banana and harder to acquire. – Nick T Nov 11 '16 at 16:56