I'm hoping someone has a better idea than me, regarding the title - [URL="http://en.wikipedia.org/wiki/Minuteman_III#Minuteman-III_.28LGM-30G.29"]according to wikipedia, [/URL] an LGM-30 Minuteman ICBM can travel at 15,000 Mph, or Mach 23. I'm struggling to understand this given the apparent propensity of the SR-71 Blackbird's airframe to expand when it goes at mach 3, such that they have to design the fuel tank to be leaky on the ground, and continuously top it up, so it contracts at speed and becomes fuel-tight (or so I've read).
Another example, bits of the NASA X-43 [URL="http://en.wikipedia.org/wiki/NASA_X-43"]apparently[/URL] melt when it travels at like mach 10.
So obviously it spends time in space, where the compressive heating isn't a problem, but surely it has to reenter the atmosphere presently at mach 23 and experience a whole lot of heating? I'd have thought designing nuclear warheads is hard enough without having to take heating of at least several hundred Kelvin into account.
Also, bonus points: I got onto this topic after seeing this picture of "aluminium plates struck by a tiny object at 16500fps" in a comment on Chris Hadfield's facebook, about micrometeorite shielding on the ISS. That speed seems appropriate for a meteorite impact, but I'm fairly sure these particular plates weren't on the ISS themselves, being fairly substaintial pieces of metal from the look of it - so I can't think of anything else that travels at 16500fps, or ~mach 15. That's somewhat faster than a railgun or any bullet?
[t]https://scontent-b-lhr.xx.fbcdn.net/hphotos-ash3/t1.0-9/q80/s720x720/10178105_775012509199508_3987670365752137196_n.jpg[/t]
[editline]6th May 2014[/editline]
Actually it just occurs to me that I had a lecture on how they study materials under extremely high pressures, and one of the methods they use are essentially [URL="https://www.llnl.gov/str/Holmes.html"]guns that fire small projectiles[/URL] at about mach 24. So that answers that question - it's still a cool picture though.
You need to consider that the nosecone of an ICBM is made of a type of ablative coating, not unlike that of a manned space capsule. In a MIRV, they add that same coating to each individual warhead. And it's not like the X-43 either, which is going Mach 7-10 at relatively low altitudes, so the heating is gonna be far worse. Heating of the nuclear warheads isn't that much of an issue as long as the implosion charges aren't damaged.
To the second part of your post, Light gas guns can get up to blisteringly fast velocities. Just wait until they start using voitenko compressors, then you're talking about a much larger projectile traveling at 220,000fps(67Km/s), which is enough energy to initiate a nuclear fusion reaction. Imagine a gun that shoots a projectile so fast it fuses the fucking atoms in the target. You can get a similar effect with an explosively pumped flux compression generator, which is similar to the voitenko compressor, but amplifies electricity rather than shockwaves.
[QUOTE]heating of at least several hundred Kelvin [/QUOTE]
"Several hundred" kelvin is fuckin' cold, man. Water freezes at 273 degrees K.
[B]Heating[/B] of several hundred kelvin however could mean going from 273K to 473K, or 0C to 200C, I don't mean the actual temperature :v:
[QUOTE=zombini;44743083]You need to consider that the nosecone of an ICBM is made of a type of ablative coating, not unlike that of a manned space capsule. In a MIRV, they add that same coating to each individual warhead. And it's not like the X-43 either, which is going Mach 7-10 at relatively low altitudes, so the heating is gonna be far worse. Heating of the nuclear warheads isn't that much of an issue as long as the implosion charges aren't damaged.[/QUOTE]
I'm not sure why it didn't occur to me that space capsules do this semi-regularly - and I suppose it's not like they need to maintain a good flying surface and attitude controls and stuff either. Still, I guess it's testament to the engineering involved in ICBMs, shame there's not much peaceful use of multiple-reentry warhead delivery platforms!
[QUOTE=zombini;44743083]To the second part of your post, Light gas guns can get up to blisteringly fast velocities. Just wait until they start using voitenko compressors, then you're talking about a much larger projectile traveling at 220,000fps(67Km/s), which is enough energy to initiate a nuclear fusion reaction. Imagine a gun that shoots a projectile so fast it fuses the fucking atoms in the target. You can get a similar effect with an explosively pumped flux compression generator, which is similar to the voitenko compressor, but amplifies electricity rather than shockwaves.[/QUOTE]
Yikes. I knew gas guns were scary but that is somewhat terrifying. Also there's enough jargon there that I feel I should eat something before going down that rabbit hole...
[QUOTE=zombini;44743083]You need to consider that the nosecone of an ICBM is made of a type of ablative coating, not unlike that of a manned space capsule. In a MIRV, they add that same coating to each individual warhead. And it's not like the X-43 either, which is going Mach 7-10 at relatively low altitudes, so the heating is gonna be far worse. Heating of the nuclear warheads isn't that much of an issue as long as the implosion charges aren't damaged.
[B]To the second part of your post, Light gas guns can get up to blisteringly fast velocities. Just wait until they start using voitenko compressors, then you're talking about a much larger projectile traveling at 220,000fps(67Km/s), which is enough energy to initiate a nuclear fusion reaction. Imagine a gun that shoots a projectile so fast it fuses the fucking atoms in the target. You can get a similar effect with an explosively pumped flux compression generator, which is similar to the voitenko compressor, but amplifies electricity rather than shockwaves.[/B][/QUOTE]
I know this is all real science talk but it sounds so much like something from Stargate or Star Trek. I mean "pumped flux compression generator" and "voitenko compressor", come on.
They can go at Mach 23 because they are big rockets, and have a lot of fuel.
[img]http://minotb52ufo.com/images/images/MMflightillustration.png[/img]
[editline]7th May 2014[/editline]
Heating isn't much of a problem with today's coating technology.
[QUOTE=Trekintosh;44743832]I know this is all real science talk but it sounds so much like something from Stargate or Star Trek. I mean "pumped flux compression generator" and "voitenko compressor", come on.[/QUOTE]
Gonna give you a little info on those two, a voitenko compressor is just a fancy pants name for what is an expendable light gas gun using HE instead of a gunpowder charge. The idea was thought up when a guy was thinking about a new type of shaped charge.
The EPFCG(short for Explosively Pumped Flux Compression Generator) uses a tube of explosives wrapped in wire, upon detonation a huge capacitor is discharged at the same time. This amplifies the electrical discharge to many times that of a lighting bolt and generates a sizeable EMP. You could channel that energy through the rails of a railgun for a one time shot at a super high velocity.
Both the EPFCG and the Voitenko compressor are thought to be capable of initiating fusion, and these technologies could be used to make a pure fusion weapon, like in MGS2 and Arsenal Gear.
As you can see, i'm very interested in weapon systems like that.
[QUOTE=Capnscarlet;44743786]shame there's not much peaceful use of multiple-reentry warhead delivery platforms![/QUOTE]
Well, the Orbital Sciences Corp. Minotaur rocket is basically just a refurbished Peacekeeper.
[IMG]http://i.imgur.com/tGZl7NK.jpg[/IMG]
[IMG]http://i.imgur.com/XEI4ymb.jpg[/IMG]
And the stuff Russians launch regularly are basically just ICBM's too. Just replace the nuke with people or satellites.
[QUOTE=zombini;44750485]Gonna give you a little info on those two, a voitenko compressor is just a fancy pants name for what is an expendable light gas gun using HE instead of a gunpowder charge. The idea was thought up when a guy was thinking about a new type of shaped charge.
The EPFCG(short for Explosively Pumped Flux Compression Generator) uses a tube of explosives wrapped in wire, upon detonation a huge capacitor is discharged at the same time. This amplifies the electrical discharge to many times that of a lighting bolt and generates a sizeable EMP. You could channel that energy through the rails of a railgun for a one time shot at a super high velocity.
Both the EPFCG and the Voitenko compressor are thought to be capable of initiating fusion, and these technologies could be used to make a pure fusion weapon, like in MGS2 and Arsenal Gear.
As you can see, i'm very interested in weapon systems like that.[/QUOTE]
Does the wire-wrapped explosives cause an initial thrust to start acceleration into the rails or what?
[QUOTE=LoneWolf_Recon;44751711]Does the wire-wrapped explosives cause an initial thrust to start acceleration into the rails or what?[/QUOTE]
I'm no expert, but i'm pretty sure it's from the electrical discharge from the capacitor gaining energy from the compression of the wires. That spikes the output to an enormous level and could possibly be a source of electrical power for the railguns. Unfortunately they are explosives, and usually destroy themselves, so it's good for one shot.
Actually i checked it out and i was wrong, the EPFCG generates an incredibly powerful magnetic field, so it can be used directly to launch ferric(iron based) projectiles at extremely high velocities. Also got some numbers on just how intense these things are. There's a model of these that have been tested and have reached 200-300 million amps of current and generated a 200 Tesla+ magnetic field. They can also be chained together to make an even more powerful electric pulse. They're effectively a man-portable non-nuclear EMP bomb that makes lightning strikes look weak.
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