Even for hypersonics, the efficiency of chemicals at storing energy and then releasing it is hard to beat. 1 kg of TNT produces 4.2MJ; to get the same energy in 1kg of projectile you’d need to travel at ~6500 miles per hour. (About mach 9 at sea level.)
The role of hypersonics is in application:
- sudden attacks, to prevent response
- low altitude, high velocity attacks, to defeat intercept
- penetration, coupled with a chemical warhead, to hit hardened targets
Source:
It seems like around Mach 10-20 is where the tradeoff could become non-obvious, depending on how much you value weighing less?
Moreover, it would be hard to avoid being partially vaporized before reaching the target. So hitting something at Mach 10-20 seems much more difficult than filling the missile with explosives and detonating it.
Weapons based on kinetic energy alone seem practical only against satellites or against targets that fly in the upper atmosphere.
> The U.S. Air Force said on Monday it had conducted a successful test of a hypersonic weapon, which flew at five times the speed of sound.
But to your question:
> around Mach 10-20 is where the tradeoff could become non-obvious, depending on how much you value weighing less?
The same logic holds at mach 5-8 (ie current hypersonics), which is why they’re being developed:
You want a weapon that can surprise, evade, or penetrate better — even if that’s less destructive overall.
For ground based targets that's probably fine (in fact for slow-moving, armored targets kinetic-energy penetrators are already a thing). For anti-aircraft fire the goal is to get "close enough" that the explosives will damage it.
Yes. For lightly armoured targets, their own velocity might do it. See https://en.wikipedia.org/wiki/Brilliant_Pebbles#Brilliant_Pe...
And if you want to go further, de-orbiting tungsten rods make the explosives redundant. https://en.wikipedia.org/wiki/Kinetic_bombardment
Over-hyped I think. Sure the kinetic energy is incredible, but what of the terminal ballistics? I think these would have substantial over-penetration against anything except deep bunkers; most of that kinetic energy would be spent driving that rod through bedrock, like an APFSDS dart shot into tank armor. Good for punching holes in things.
But I wouldn't discount to the ability of weapons designers to figure out the frangibility and deliver the bulk of the energy to a tuneable depth.
But to answer your question, I believe the energy released by a kinetic impactor quadruples every time you increment a Mach number. So a kinetic impact at Mach 4 is 16x more energetic than a mach 2 impact.
I think it must have come from hearing things like "They don't do that any more" and not recognising "any" and "more" as separate words, but rather as a concept that just means "now", such that "They do that anymore" is equally valid.
I picked it up from Pennsylvania unintentionally. Not a huge fan of it tbh.
Is there a speed threshold where the kinetic energy is enough to justify not doing that?