After an exchange of emails with Kurt, I am considering a possible change to maintenance but I want to run it by the list first to get some feedback.
Kurt made the point that its not very realistic that spares cannot be exchanged between classes, as in reality spare parts are designed for systems that may be common to different classes. Interchangeable spare parts would also allow stockpiles of spare parts to be built up instead of only being created by a minor or major overhaul.
However, there are some problems with allowing spares to be exchanged under the current rules. In reality, the spare parts required to keep a 5000 ton warship running would cost more than the spare parts for a 5000 ton freighter. The current method simulates this because the overhaul of the more expensive warship costs more than the freighter overhaul. If spare parts were interchangeable, then all spare parts would have an equal cost. At the moment spare part use is based on the size of a ship. Originally I was going to use cost but Michael Sandy pointed out a problem with that in a now-lost post and I changed to size-based. With a cost-based model, higher tech ships would cost more so the same size ship would use more spare parts and therefore need more space devoted to engineering just to keep the same level of maintenance. Of course this is all based on the current model of a set number of parts per engineering section.
So working on the assumption that interchangeable parts would be a more realistic situation and that spare part stockpiles could be built up rather than being created by an overhaul, that eventually brought me to the following ideas.
The current engineering section would be replaced by a new tech line of Engineering Spaces (or whatever name I end up with), each of which would affect the chance of failure, rather than just carrying spare parts. Higher tech engineering sections would reduce the chance of a failure, which would be based on time since overhaul and cost of the ship (not size). There could also be different types of engineering spaces based on size, cost and effectiveness. So one option may be a large, cheap version and a small, expensive version that both have the same effect for the current tech level. This would allow me to display the current failure chance on the ship display. Multiple versions would have a cumulative effect. So (making up numbers), if one engineering system had a 5% annual chance of failure per 100 BP of cost and you had two of them, that would reduce it to 2.5%. That might get complex with different types of systems on the same ship so maybe a better idea is to have a user-designed engineering system based on size, effectiveness, etc. and you add just one to a ship.
Spares would be replaced by Maintenance Supplies, which would be built by maintenance facilities using the same on/off option as fuel refineries. Maintenance Supplies could be stockpiled and collected in the same way as fuel and would be interchangeable between ships. They would be carried by engineering spaces and total supplies carried would be one of the parameters for the engineering section. They would be tracked by cost, so a ship might be carrying 100 BP worth of maintenance supplies. When a system fails, the program would decide on a specific system, rather than a general failure, and maintenance supplies would be used up equivalent to the 25% of the of that system. So if a 40 BP engine failed, then 10 BP of maintenance supplies would be used up to fix it. This maintenance cost means that a warship will likely use up maintenance supplies faster than a non-combatant.
I would also adjust damage control so a ship would use up these maintenance supplies to make repairs to its own systems, although at the standard repair cost of 50%, rather than maintenance cost of 25%. I would introduce greater variety of damage control systems and have a limit on the absolute cost of any system that would be repaired by a specific damage control system. So a warship with a normal damage control system might be able to fix a engine but maybe not the jump drive. This would then allow repair ships with extensive damage control systems capable of repairing large systems plus a lot of maintenance supplies.
These changes would also remove the need for a minor overhaul although the major overhaul would function exactly as it does now.
I may also extend the concept of engineering spaces affecting chance of failure to the point where a system removed any chance of failure, although this would be very large (perhaps 25% of the hull size) and therefore suitable for bases only.
Comments and suggestions welcome.
Steve