I don't really think an aerosol mist of acid would be super effective flash frozen by vacuum. If you're going to eject an aerosol to attack solar panels you really don't have to do actual damage to them, though. If you can simply coat them with something that will absorb or reflect enough light they become useless. As for the practicality of a projectile weapon... You'll certainly still have drop due to gravity, you are essentially putting the projectile on a different orbit. There would be considerably less effective drop than on the surface of the Earth, though, making it more accurate. If we're talking about human fired small arms I would think that anything within a range that a human can practically engage would not be too far for them to aim the weapon at. (After all even on Earth Snipers take drop into account, along with windage and other factors.) If we're talking about vast distances then a human fired weapon would be hopelessly inaccurate, but a machine could fire it with incredible accuracy, not to mention full orbital precalculations of the projectile's path. In such a case your target's movement isn't really a factor so long as it is in a freefall orbit and not actively maneuvering. In fact if you fire the projectile retrograde with respect to your target's orbit then you gain that much more impact velocity. There should be no need what so ever for active guidance just to hit a satellite, though you may first need to achieve a decent firing solution via maneuvering your weapon. A neigh undetectable projectile shouldn’t be too difficult to construct, thus giving you a weapon with very nearly zero chance of being intercepted or impeded in any way against freefall targets. For human fired weapons recoil cannot be ignored, but it certainly would not prevent the use of the weapons. Certainly firing a handgun in a terrestrial pose would put you in a spin, but honestly all you have to do is align the velocity vector with your center of mass. If you’re thinking firing from the hip, (which would really make it hard to aim without a camera on the gun sight) then you’re still thinking terrestrially. Let’s take a page out of Ender’s Game, shall we? “Remember, the enemy’s gate is down.” Point the gun through your knees, back arched, and legs out. You should be able to get pretty close to proper alignment at least. Another option is strait overhead, which also gives you a very small angular profile from the point of view of your target if you keep your legs together. The recoil from individual shots would propel you a little, but nothing you shouldn’t be able to counter. Modern spacesuits I might note: are not build for such maneuvers and would likely need some modifications for visibility and flexibility. Something like a chain gun probably would require anchoring to the ship first. A counter recoil system would certainly be possible, but you will have to expend the same amount of force in the opposite direction. With a conventional bullet this would be equivalent to firing it in a simple tube barrel open at both ends resulting in really two projectiles the bullet and the casing. The bullet would also have half the velocity it would otherwise have gotten from the discharge. Though there’s certainly no need to actually eject the brass out the back of the gun at dangerous velocities you would have to provide an equivalent amount of thrust. A safer option would be to use a piston to spread the recoil over a longer period of time and use a lower amount of thrust to stabilize. I wouldn’t worry too much about casings outside the ship and if you’re firing inside then you’re already nuts unless you’re suited. If you’re really worried about it use a non-disintegrating belt or some sort of device to catch them instead of ejecting the casings. As for lubrication... There are many solid lubricant coatings being developed which essentially make greatly reduce surface friction. NASA also is developing and uses very thick lubricants with special properties, which don’t sublimate in vacuum. Graphite is not the only option. As for the laser defense... I imagine that you could not only “puff smoke” but you could probably develop an ablative covering which would react to the laser it-self to provide the same thing. The result could be both defense and detection mechanism. And although lasers are coherent and do not adhere to the inverse square law the light does spread out over great distances, which is a factor in their usefulness. If laser attacks are a particular threat you could also do something like active cooling for outer surfaces (probably reduce micrometeorite shielding effectiveness), thermally insulating the outer surfaces from vital parts (ceramics, vacuum spaces, ect...), and use reflective coatings. Then you have the active defenses like the particulate, maneuvering, and popping decoys. If you can determine with any accuracy the vector of the attack a counterattack could even be launched.

"Unless a set of microbolometers could be arranged to view the spacecraft skin and their output fed to a protection suite control system." Possibly, but you do need to cover a lot of angles, and we've forced an additional burden on the satellite designer. "I am thinking of the satellite effectivly poping smoke and displacing to a new firing position like a AFV would when faced with incoming ATGM. The solar panels on such a satellite would be moved clear of the particulate cloud by the change of orbit." That is the beauty of a laser type device. It works at light speed. You take your shot, and can see it hit or miss the target. If the target moves, you re-aim and fire within a second or two. A missile or bullet could take hours to get to a the target which gives a defender a chance to react, and if you miss you start the whole long time cycle again. "Granted some applications can't be spin stabilized, however for example two old quotes;" This is why I have been slow to get back to you, I have not had a chance to research this. I have my opinion but I want to be able to document what I say. So I'll be back later when I can.

Mechanical weapons, like rifles and missiles can take hours to reach their targets. Even if we think in terms of 10 or 15 minutes to hit which would be pretty close to the target, it gets complicated. Remember the bullet/missile will behave strangely. If you shoot behind you the bullet will drop rather quickly due to it's reduced velocity. If you shoot in your direction of travel you actually go up since your total speed is higher. The mechanics involved get pretty strange. That is why an active seeker is so useful - to compenesate for minor ballistic errors or even defensive maneuvers by the target satellite.

Not the best answer and source but this is worth reading. Please go the real site and look at the hyperlinks. ------------------------------------------------------------------------------- POLHODE AND HERPOLHODE CURVES By Miguel Lidón Plaza [email protected] INTRODUCTION The design of a space vehicle is a task that has multifarious and very complex activities. One of the most important aspects is the determination and control of its attitude or direction because together with the study of its orbit constitute the general movement of the space vehicle. Stability of the movement The fact that the space vehicle maintain a certain attitude is important, for example, in the need maintain a zero angle of attack during its impulse through the atmosphere or that acquires the necessary angle of attack (zero for ballistics income) prior to the entry in the atmosphere or the importance of the appropriate direction of the impulse for the modification of its orbit or its correct direction to send signs to The Earth or to point to stars. Usually, the space vehicle is inherently unstable and it is submitted to torques engendered by its interaction with the environment and by the movement within the vehicle. Though the forces associated with these torques are not normally sufficiently large to affect the orbit of a space vehicle, the torques can affect significantly the attitude of the space vehicle. The torques of the environment (external) on a planetocentric satellite can be originate from the solar radiation pressure, from magnetic and gravitational planetary fields, and free molecular forces (if the satellite is sufficiently close to a planetary atmosphere). Exist the possibility also of impacts produced by meteorites and particles of dust. The torques that originate of internal movements can be engendereds by displacement of the load and by the movements and actions of the occupants as well as by the ejection of propellants and other liquid. If a space vehicle in orbit is unstable, will degenerate if it is disturbed; if it is marginally stable (not damped), it will oscillate about a balance position; and if it is stable (with the external or internal damping), will return to the balance position after that the transient oscillation is extinguished. Although an unstable space vehicle will be unacceptable, a space vehicle marginally stable can be acceptable if the extent and the frequency of the oscillations are small; a dynamically stable space vehicle is the design goal. The stabilization techniques can be classified as passive or active. The active stabilization devices, such as thrusters, gyroscopes and reaction wheels, require an energy expense and increase in the weight of the space vehicle and they can be expensive; furthermore, energy supply is exhausted, the control of attitude of system fails, the space vehicle degenerates, and the mission will aborted. In addition to stabilization problem, there is an independent direction problem, generally a problem of active control, in which the space vehicle or a part of the equipment of the space vehicle must point to a specific direction. It is considered, for example, an exploration satellite of the Earth with cameras and infrared sensors that they should always point to the surface of the Earth. It can have also missions to investigate the Sun or other celestial bodies and navigation missions in which the antennae should maintain or acquire the required directions. Furthermore it is always the need of an appropriate direction before of the thrusting to put it in orbit. Although, generally, the applications of the space vehicles are satellites in geocentric orbits, this study can be extended to orbits on other planets or other bodies, such as moons and asteroids, and to interplanetary transfers. Disturbance torques of the space vehicle As has been mentioned, the operation of the space vehicle is submited to numerous disturbance forces that, if they do not act on the center of mass, produce a torque applied to the vehicle. The evaluation of these influences from the point of view of absolute magnitude and relative magnitude is an essential part of the task of the designer of the system of control and determination of attitude of the space vehicle. Below they will be listed the principal external sources of disturbance of a space vehicle: Aerodynamic torque Gravity-gradient torque Solar radiation pressure torque Magnetic torque Miscellaneous disturbance torques The internal torques are of greate importance in the control of attitude of the space vehicle, resulting from the exchange of momentum between internal mobile pieces. This not has any effect on the total momentum of the system, but it can influence and influences the sensors direction mounted in the vehicle and the circuits of control of attitude that they could be operating. Typical internal torques are: Antennae Solar panels Movements of ex

you could use spething like the o'dwyer VLE.. scaled up.. < metalstorm company makes it> no moving parts.

I'll be reading up on this, sounds like it is topical. Thanks very much for your pointer. My work is hectic so it will be slow. PS. I guess commenting on google earth images is about as popular as commenting on police shootings around here! I'll be toning down the detail in all my posts consequently, but any of you can reach me on directly on johnbutler_at_hotmail.com

Yimmy - tisk Newton would be ashamed of you.  The physics of action = opposite reaction applies to air rifles too.  The only systems that would not suffer recoil would be rocket propelled ammunition (e.g. Gyrojet pistol).