3 ms·
What do you mean? A butter stick sized piece of C4 is similarly stable but contains more stored energy.
by zmgsabst 4y ago
What do you mean?
A butter stick sized piece of C4 is similarly stable but contains more stored energy.
- rdl 4y agoI thought it was "via a cow", which is noisy and dangerous.
- dtgriscom 4y agoDoes the C4 have more energy, or just the ability to release it (a whole lot) more rapidly?
- HarryHirsch 4y agoThe latter. High explosives come with the oxidant built-in, and the reaction propagates faster than the speed of sound.
- causi 4y agoYou are completely wrong. 1 gram of C4 contains 1.59 kilocalories of energy. 1 gram of butter contains 7 kilocalories of energy.
- saalweachter 4y agoIt looks like C4 is 60% denser than butter, but that isn't enough to save the original claim on size, versus weight.
- dredmorbius 4y agoExplosives, much as other forms of energy storage, tend to have lower specific energy (energy per unit mass) than slower-burning fuels. 1 kg of TNT has roughly 4.6 MG. 1 kg of petroleum has roughly 45 MG, ten times as much. The difference is that the trinitrotoluene combusts rather more rapidly than the oil. But if, say, you simply want thermal energy and have a mass budget, you'll go with the oil. C4 has an energy density of about 5.1 MG/kg, slightly greater than TNT, but only 1/8th that of petroleum. <https://en.wikipedia.org/wiki/C-4_(explosive) https://en.wikipedia.org/wiki/C-4_(explosive)> <https://en.wikipedia.org/wiki/Energy_density https://en.wikipedia.org/wiki/Energy_density>
- HPsquared 4y agoThis is because for the butter, you're not counting the weight of all the oxygen that is needed for combustion. 1kg of butter requires several kg of oxygen (or if you're using air, even more weight if you count all the inert nitrogen)
- dredmorbius 4y agoThat's a valid point and does shift the balance somewhat, but not fully in favour of nitrogen-based explosives. From a practical perspective, at least within Earth's atmosphere, that oxygen is "free". There's not need to carry it with you, though some combustion applications may require feeding it at high rates (turbochargers, compressors, gas turbines, and the like). Most automobiles functions strictly under natural aspiration, and even industrial combustion typically utilises relatively low-power bellows or air introduction. Rockets, of course, carry their own oxidizer, so we can compare energy densities based on net yield. The Saturn S-IC (first stage of the Saturn V stack) is powered by the combustion of RP-1 (a highly-refined grade of kerosene) and LOX, liquid oxygen. The tank sizes were 730,000 L fuel, for which I'm assuming an average density of 0.9g/mL (0.81--1.02 given by Wikipedia), and 1,204,000 L oxidizer, at 1.41 g/mL. That works out to 657 tonnes of RP-1, 1,374 tonnes of LOX, or a total of 1,511 tonnes. The fuel alone is 43.5% of the total mass, which means total specific energy is reduced to 17.63 MJ/L, which is still about 3.5--4 times greater than TNT or C4, by comparison. There's one further question as to whether or not the rocket is tuned to run rich, stoichometric (balanced fuel and oxidizer), or lean. Most LOX rockets burn somewhat rich, based on recollection and Wikipedia, so the LOX quantity is slightly short of what might support complete combustion, though not enough to affect the overall outcome here. <https://en.wikipedia.org/wiki/S-IC https://en.wikipedia.org/wiki/S-IC> <https://en.wikipedia.org/wiki/RP-1 https://en.wikipedia.org/wiki/RP-1> <https://en.wikipedia.org/wiki/Liquid_oxygen https://en.wikipedia.org/wiki/Liquid_oxygen> <https://en.wikipedia.org/wiki/Rocket_propellant#Mixture_ratio https://en.wikipedia.org/wiki/Rocket_propellant#Mixture_rati...>
- zmgsabst 4y agoOkay — but that same table points out that common everyday plastics meet the criteria re: butter.