For some good general notes on making a fusion powered spacecraft, you might want to read Application of Recommended Design Practices for Conceptual Nuclear Fusion Space Propulsion Systems.
There are also some nice examples on the Realistic Designs page. For less scientifically accurate spacecraft design the Constant Variantions blog has a nice article on historical trends in science fiction spacecraft design. Like any other living system, the internal operations of a spacecraft can be analyzed with Living Systems Theoryrocket boys and lesson plans, to discover sources of interesting plot complications.
The improvised space warcraft are the type that seems to hold the most story potential. These would, as mentioned, likely be built by colonies that are in conflict. As they do not have to operate in an atmosphere, and are built by relatively poor colonies, they are likely to be rather crude. The basic components required are structure, propulsion, weapons, life support, power, sensors, control, and communicationsand each will be briefly discussed in turn. There are two methods of assembling an improvised warcraft, either adapting an existing vessel, or constructing a new one from parts.
The use of an existing vessel removes the need for some, though not all, of the various components. The structure will obviously be preserved, and propulsion and life support are almost certain to remain unchanged as well. Weapons would obviously be added, along with their associated control equipment. Existing power supplies might or might not be sufficient, depending on the weapons fit chosen. Sensors and communications are gray areas, depending on the tasks required of the vessel, and the existing fits in these areas.
Structure is one of the easiest components to create. So long as the builder does not mind the craft being somewhat heavy, slapping a few beams together should be sufficient. Existing structures, such as cargo containers, could easily be modified, or simple new ones fabricated. In any case, this is not likely to be a driving factor in construction or conversion of vessels. Any group incapable of creating basic structure is also rocket boys and lesson plans certainly incapable of surviving if it were to win a rebellion.
Propulsion for improvised craft is likely to be chemfuel due to the fact that it is by far the simplest to implement, and has sufficient delta-V for any operations that do not involve transiting deep space.
It is entirely possible that a colony will have standard chemfuel engines used in various places, and one of them, with appropriate fuel tanks, would be fitted to the vessel. Nuclear propulsion rocket boys and lesson plans much more expensive, and might well involve detailed engineering to avoid killing the crew. The performance sample annual learning plans for teachers over chemfuel for nuclear-thermal is probably not significant enough to justify the problems involved, and nuclear-electric is only practical for vessels intended for deep space use.
Weapons are a tricky issue. These are likely to be improvised as well, and would fall into the same categories already discussed. Improvised lasers are highly unlikely, rocket boys and lesson plans. Industrial lasers lack the optics trains required for weapon use, while any optical trains available probably from astronomical or other scientific sources are unlikely to be able to handle the high powers output by the lasers.
With some time, an appropriate optical train could be designed and mated to an industrial laser, and it is even possible that colonies could design and test such things in case of war. Kinetic projectors are in largely the same boat. While small mass drivers could be adapted to such a task, it is difficult to see a role for such devices on a vitamins and health needs. There is also the issue of targeting, which, while not insoluble, requires good pointing accuracy and possibly the creation of guided projectiles, which have even less peacetime use then the launchers themselves.
This leaves three options, missiles, lancers, and unguided kinetics. Unguided kinetics can be as simple as junk thrown out of the airlock, but they are of very limited effectiveness, as shown in Section 8, rocket boys and lesson plans.
Missiles and lancer projectiles face many of the same issues, and the only practical difference is the motor, which should be relatively easy to improvise.
A missile or lancer will require sensors, thrusters, and guidance logic of its own. As this force is presumably facing another more or less improvised one, complicated guidance logic is probably unnecessary, and proportional navigation is quite easy to implement. Vitamin e and foods sensor might well be adapted from another role, which means that the likely problem is rocket boys and lesson plans the thrusters.
These must be well-balanced and integrated with the guidance logic. Depending upon the materials available, this could range from very easy if there are large numbers of small, self-propelled objects that can be used as warheads lying around to extremely difficult if the entire system must be designed from scratch. Small thrusters themselves are an unknown. There are some systems that might use small thrusters, such as thruster packs for spacewalkers, in which case the actual integration is all that is required.
However, the number available might well be strictly limited, forcing the builder to start from scratch. Note that this is not as easy as it seems. While a primitive kinetic could probably be built with the simplest of systems, it would be inefficient, of dubious reliability, and probably quite large.
In the end, this is an area in which the specific situation plays a very large role, leaving us unable to anticipate exactly what might occur. Life support should be straightforward to build into a vessel. Any space colony will undoubtedly have small, portable habs that can be used for surface expeditions or what have you.
Mounting one of those would be relatively simple, and the actual mechanisms for short-term life support are fairly rudimentary, easing implementation if for some reason a hab had to be constructed from scratch. Power is a rather tricky proposition. Unless a nuclear propulsion system is used, power is likely to be at a premium. Most non-nuclear power studies assume that solar panels will be used, but these have significant drawbacks for space warfare.
Radiators, discussed in Section 7, are both somewhat less vulnerable to damage, and can be kept edge-on to the enemy. A clever opponent could manage to create a dilemma between getting power and preserving the panels from damage, rocket boys and lesson plans. Alternatives include fuel cells and batteries. Fuel cells are the current solution for short-duration spacecraft, due to their possessing higher specific energy than batteries.
The problem is that fuel cells are somewhat involved to manufacture and are not likely to be common on space colonies, rocket boys and lesson plans, unless the colony is far enough from the Sun that solar panels are not effective. Batteries are somewhat more likely to exist, but are heavy for their power output.
The only bright side is that a truly improvised spacecraft is unlikely to need much in the way of power, particularly when compared to a nuclear-electric laserstar. Sensors are probably the biggest unknown. A proper space warcraft needs some form of active sensor to localize the enemy, although it is possible that a simple passive sensor would be adequate for simple missiles. The sensors might or might not be readily available. Sensor suites for existing spacecraft are the most likely source, although cobbling sensor suites together from other uses might be possible.
Control is mostly a matter of systems integration. Depending rocket boys and lesson plans the nature of the systems involved, control setup could range from simple running of cables and plugging together a few modules, to having to write all of the code to make everything talk, rocket boys and lesson plans, or simply doing without an integrated control system.
While it is certain that some systems will have to talk sensors and weapons spring to mind a large portion of the integration could be skipped, with a resulting loss of efficiency due to the crew having to move rocket boys and lesson plans. Communications is fairly simple, as one thing people in space will have to do is talk. This should ensure the availability of communications modules, which can be attached to the vessel. The most likely cause of problems is lack of strong encryption and particularly electronic warfare capability in such modules.
Depending upon the capability of the opposition, this may or may not be a serious hindrance. The encryption capabilities should be a reasonably simple fix, rocket boys and lesson plans, involving mostly software updates.
The EW work will be harder, as there are likely to be physical changes required to ensure freedom from interference by enemy radio transmissions. This is not likely to be a problem if the communications module is radio-based.
This is the living breathing core of all rocket design. This is the secret that makes rocket design possible. Now it is time to see the practical application of the key to rocketry.
Everything about fundamental spacecraft design revolves around the Tsiolkovsky rocket equation. The point is you want as high a delta-V as you can possibly get. The higher the delta-V, the more types of missions the spacecraft will be rocket boys and lesson plans to perform. If the delta-V is too low the spacecraft will not be able to perform any useful missions at all. Looking at the equation, the two obvious ways of increasing the delta-V is to increase the exhaust velocity or increase the mass ratio.
Turns out there are two more sneaky ways of dealing with the problem which we will get to in a moment. Historically, the first approach has been increasing the exhaust velocity by inventing more and more powerful rocket engines, rocket boys and lesson plans. Unfortunately for the anti-nuclear people, chemical propulsion exhaust velocity has pretty much hit the theoretical maximum. The only way to increase exhaust velocity is by using rockets powered by nuclear energy or by power sources even more frightful and ecologically unsound.
This is the source of the rule below Every Gram Counts. Everything that is not propellant, in other words. All of it will have to be trimmed. To reduce dry mass: Other tricks include using Beamed Power so that the spacecraft does not carry the mass of an on-board power plant, and avoiding rocket boys and lesson plans mass of a habitat module by hitching a ride on an Aldrin Cycler.
Finally the effective mass ratio can be increased by multi-staging but that should be reserved for when you are really desperate. The third approach is trying to reduce the delta-V required by the mission. Use Hohmann minimum energy orbits. If the destination planet has an atmosphere, use aerobraking instead of delta-V.
Get more delta-V for free by exploiting the Oberth Effectthat is, do your burns while very close to a planet. NASA uses all of these techniques heavily.
If your technology is high enough, use space tetherslaunch catapultsand MagBeams. The fourth and most extreme approach is to cheat the equation itself, to make the entire equation not relevant to the spacecraft, rocket boys and lesson plans. The equation assumes that the spacecraft is carrying all the propellant needed for the mission, this can be bent several ways. Use Sail Propulsion which does not use propellant at all.