Wikipedia:Reference desk/Archives/Science/2013 December 30

= December 30 =

Electro Magnetic Pulse missile
In a dogfight, the air-to-air missile from one plane needs to make actual contact with the other plane and explode to take out the target. This, of course, requires a level of accuracy in the shot. Having the missile explode close to the target limits the damage and it is possible for the target to survive and continue to engage. My query is about EMPs. I have read through several articles here and am not sure that I am totally understanding the concept. Do we have the technology to fire an EMP missile at a target, have it "explode" nearby (as opposed to a direct hit) thus disabling the target? If so, would the pilots still be able to eject or is that function also electronically controlled? 173.35.158.194 (talk) 01:37, 30 December 2013 (UTC)
 * One of the biggest secrets during WWII was the proximity fuse -- used for AAA rounds, (not for air-to-air, as far as I know). As the name implies, it explodes as it gets near its target, hopefully striking target with a fatal dose of shrapnel. I'm not sure what you mean by an EMP missle (unless you're thinking about a small nuclear device) -- EMP could theoretically be used in more of a directed energy beam-type weapon(or defensively, as part of ECM). ~E:71.20.250.51 (talk) 02:01, 30 December 2013 (UTC)
 * After re-reading the question... would a pilot be able to eject from an aircraft with disabled electronics? I haven't entirely read our article ejection seat, but at least the early ones were mechanically fired by pulling a lever releasing a compressed air canister; later versions had small rockets.  Somebody here probably knows if currently there is any electronic component that is required -- but I doubt it (and even if so, there's probably a mechanical override). ~E:71.20.250.51 (talk) 02:16, 30 December 2013 (UTC)


 * UPDATE: I guess there is an EMP missle: (Oct. 24, 2012) "Boeing's new missile takes down electronics without touching them", NBC News-Technology ~:71.20.250.51 (talk) 02:27, 30 December 2013 (UTC)
 * I suspect ejector seats don't rely on electronics, but don't have a good reference. However this raises a few interesting points. A device which purposefully defeated an ejector seat, even though it already destroyed the plane would I suspect, be frowned upon, if not be outright banned by treaty. If such a device did however come into widespread use, I further conjecture that ejector seats would be modified accordingly, it's called an arms race. Vespine (talk) 03:52, 30 December 2013 (UTC)
 * The US has been investing in EMP hardening, mostly relating to communications; and military specs and NASA specs for electronics are more rigorous than civ specs. Although the results from the Boeing test missile are classified, it is certain that the test included targets with various levels of hardening. ~E:71.20.250.51 (talk) 04:28, 30 December 2013 (UTC)
 * Someone on Linkedin claims: "We have tried EMP explosions here in India as well and they were not found to be effective against EMP hardened aircrafts." Although the thread was about detecting stealth aircraft by using EMP, I assume this comment refers to disabling them. source  Ssscienccce  (talk) 14:01, 30 December 2013 (UTC)
 * Our air-to-air missile section discusses several popular alternatives to having the missile itself have to hit the target (and then explode there). DMacks (talk) 07:10, 30 December 2013 (UTC)

I guess my thinking in my original post was that IF an EMP could knock out the power of the target aircraft then there is the possibility of retrieving more tech from the remains as compared to the virtual total destruction of a direct explosive hit. Also, if the pilots could then eject they would survive and could be captured as prisoners. 173.35.158.194 (talk) 18:41, 30 December 2013 (UTC)
 * An air to air missile is not designed to totally destroy an aircraft mid flight, it only needs to cause just enough damage to make the plane uncontrollable, some damage to the engines or control surfaces is usually more then enough, the crash at the end is what destroys the aircraft. Vespine (talk) 00:05, 31 December 2013 (UTC)
 * I'd never heard of Continuous-rod_warhead but just read about it now as a result of this discussion. The ingenuity displayed by our species' desire to kill each other never ceases to amaze me. Vespine (talk) 00:15, 31 December 2013 (UTC)

CO2 Freezing?
At what temperature would carbon dioxide freeze? --173.77.159.60 (talk) 17:52, 30 December 2013 (UTC)


 * According to Carbon_dioxide, 'At 1 atmosphere (near mean sea level pressure), the gas deposits [i.e. changes from gas to solid] directly to a solid at temperatures below −78.5 °C'. AndrewWTaylor (talk) 18:00, 30 December 2013 (UTC)


 * So in other words, the package dry ice is in is always under -78.5 °C? 173.77.159.60 (talk) 18:22, 30 December 2013 (UTC)


 * The ice itself is always at or under -78.5C. What is packaged with it could theoretically be slightly warmer. When I send packages in dry ice, I always have it surrounded by dry ice on all sides so that hypothetically it is also always under -78.5C Someguy1221 (talk) 18:25, 30 December 2013 (UTC)


 * Only if it's been in there long enough for the temperature to equalize between the dry ice and contents. StuRat (talk) 18:57, 30 December 2013 (UTC)