From v04.n294 Sat Jan 10 09:15:22 1998 From: Stan Berry Date: Wed, 7 Jan 1998 16:56:37 -0500 Subject: Re: Explosions in Space/Vacuum Status: RO X-Status: At 3:51 PM -0500 1/7/98, oberdan@interactiva.it wrote: >Hello... I've a question for the gurus of Gurps and Physics... > >What are the effects of an explosion in deep space??? And if a nuclear >weapon is triggered??? >I thinks that the damage isn't reduced for the distance from the explosion >but perhaps it's reduced for the lack of an athmosphere... > >Thanks > >Max (oberdan@interactiva.it) I can't say much about conventional explosions, but I have done a lot of work on nuclear survivability. Copying a posting I made a few days ago on another thread --- Technical details on Nukes in space: Nukes in deep space behave quiet differently from nukes in sea level density atmosphere. In both cases, the prompt energy starts out as about 75% soft X-rays 24% kinetic energy (ionized bomb material moving very fast) ~1% hard radiation (neutrons, gammas, etc) for a typical nuclear weapon. (Weapon designers can change those percentages a bit.) In the atmosphere, the soft X-rays are absorbed into the air within a few yards, quickly forming a very hot ionized fireball that produces heat and adds to the blast. The shockwave propagates very nicely at about the speed of sound. The shockwave produces an overpressure that can crush or move or overturn objects. In deep space, there is no fireball. The X-rays travel an unlimited distance, just getting less intense as they spread out. (Remember that the area of a sphere is 4*pi*R^2.) When these soft X-rays hit a satellite or spaceship, they deposit in the very outermost layers in very short times, causing thermomechanical shock. The outer surface can melt or vaporize, and the whole structure could be damaged by warping or vibration. A weak fragile surface like a telescope might be damaged by 0.1 cal/cm^2, while a tough metal surface might withstand 10 cal/cm^2. Re-entry heat shields might withstand a little more energy. (These 0.1 to 10.0 cal/cm^2 environments don't really represent huge amounts of heat; the damage is done by the very steep thermal gradients induced by heating only the outermost layers in sub-microsecond time periods.) With a layer of shock isolated ablative armor, much higher X-ray fluences might be withstandable; at TL7, the weight of a satellite is so critical that things like that are unrealistic. The distance to a vulnerable range (in space) varies with yield: Yield 0.1 cal/cm^2 1.0 cal/cm^2 10.0 cal/cm^2 1 kt 7.7 km 2.4 km 0.7 km 10 kt 24 km 7.7 km 2.4 km 100 kt 77 km 24.4 km 7.7 km 1 Mt 244 km 77.4 km 24.4 km (Of course basing hardness on thermomechanical shock from X-rays assumes that the electronics have some degree of hardness to the hard radiation, but that is another matter.) So, a 700 meter miss distance from a small 1 kt weapon ought to do a LOT of damage to a solidly-built but unarmored spaceship. Conversely, a 700 meter miss from any sort of conventional warhead in space would PROBABLY do no damge. A few feet or yards of solid rock or metal have an amazing ability to resist a nuclear blast. Modern TL7 spaceships and satellites are thin-walled. My only explanation is that GURPS space ship-to-ship system assumes small nukes, and thick and solid spaceship armor. Stan Berry http://fly.HiWAAY.net/~srberry/