There is also the point that on Earth the torpedo is a comparatively short-range weapon, fired from concealment or under conditions where the torpedo-carrier approaches so rapidly it cannot be stopped--by a submarine under-water, by surface ships at night or from behind smoke-screens, by torpedo-planes that attack at ten times the speed of the target-ship. None of these conditions can be realized in space-warfare. Even if the space-ship were painted black and operating in a planetary shadow (as in some stories) radar would pick it up at a distance at least equaling that from the Earth to the Moon. And even black coloring would make the space-ship visible as it occluded the practically continuous blanket of stars visible in open space. You can't make a smoke-screen in space--you can make it, but it wouldn't hang and wouldn't be any use against radar if it did. Comparative speeds that would permit the torpedo-plane type of attack are simply unattainable. Finally naval experience shows that fire is always opened at the greatest possible range where there is any chance of doing damage--and that range is usually maintained in the hope of avoiding hits. Only when one party has been so badly pounded that defeat seems inevitable is there an effort to close the range for torpedo or gunfire. In space-war, given high visibility and the fact that there will be neither gravity nor air resistance to slow up shells, fire will be opened at extremely long ranges--hundreds of miles. At this distance, a rocket-torpedo, clearly indicating its presence by its trail of fire, will be quite easy to intercept--by shooting smaller rockets or shells with proximity fuses at it. The time it will take the torpedo to cover the distance is the major factor. And running in to launch a torpedo from close range will be very difficult because of the low speed differential between the two parties and again because of the distance. So it is probable that most space-actions will be fought out with guns. I said guns. But a very different type of gun from those most of us are familiar with, because this is another point where Earth-thinking must give way to space-thinking. When the breech-block of a gun aboard one of our cruisers is swung open to receive a new shell there is a brief moment when the gun forms an open connecting tube from the inside of the turret to the outside air. * * * * * This will never do aboard a space-ship--there is no air outside and the air from all over the vessel would rush in a tornado to escape into outer space. There will have to be some device for loading the gun in a vacuum or, since this might give trouble in case of a breakdown or a misfire, more likely an automatic tompion to close the mouth of the gun until there is another charge in the breech. This would have the advantage that the rush of air into the gun, evacuated by the previous firing, would automatically clean it of residual explosion products.