What is the working life time of a space craft?

[Icosahedron]

Anything designed to last for the ship's lifetime (say 80 yrs) is only about 2 to 3 times overdue and it has had very little wear for most of that time, so I'd say it should be fine.
Anything designed to be replaced during maintenance has missed 199 replacements, so it'll be pretty shoddy by now.
Depends on YTU shipbuilding practices - are they designed to last 40-60 years with nothing more than a few replacement filters, or do the drives need to be rebuilt every couple of years? Long life structures will have long life components, and vice versa.
LHyd might remain liquid in deep space, but how leak-proof are your tanks?
On a planet it will have vented away - through the obligatory safety vents.
I think it's unlikely you will have useable fuel aboard.
Bottom line is, how useable do you want the ship to be?

 

[tinker123]

Obviously the technology is completely different, but there are some present-day examples we could consider:
- a car engine can run for decades, with relatively few parts wearing out and needing replacement, but 6 months without use will mean a lot of care to get it going again: the battery dies, the oil all collects in the sump leaving the engine completely dry, the tyres are all flat (and probably worn out), the rubber hoses perish, and so on
- a computer can run for a long time, but any operating system will eventually hit a crash (although some do it sooner than others) and need a reboot; I assume the computer is left on, and not switched off. Hard disks run on bearings which wear out, as do the cooling fans (at which point the CPU burns out). Flash memory drifts away to nothing in a handful of years, and writable CDs are only expected to last for about 10 years.

Future tech will be different, but probably have similar characteristics. Long run-time assumes regular maintenance, long idle time can be more damaging than running. There will be some components with defined lifetimes that need regular replacement and when they wear out, the other systems become idle (through lack of power/lubrication/compressed gasses/whatever).

On the other hand, we have the canonical example of the Annic Nova, abandoned for a long time, and still ready to roll. So it's ultimately up to the story you want to tell, and either position can be argued convincingly.

 

[shadowdragon]

wet navy ships that are decommissioned but not scrapped will go into a "reserve" fleet of ships. There used to be a whole slew of ships moored in San Francisco Bay that were the American "Mothball" fleet- merchant and military ships in good enough condition to be kept but not actually needed. so they were "mothballed" for storage. this reduces the wear and tear that just sitting abandoned can cause. all liquids are drained from the engines, vital electronics sealed against the weather etc... Its a process that takes time and money to do but is worth it. recommendations for storing any vehicle for a long period advise setting it on blocks (if it has wheels), drain engines of all fluids, seal interior etc.... so why and how would a starship be mothballed?


as far as lifetime of a ship goes- any well built and well maintained craft will last nearly forever really. at certain points you may have to do some major repair/replacement of parts and after 150 years the likelihood of many parts being original is rather low for items that decompose readily, but metals and ceramics can last thousands of years- look at samurai swords that are in museums now. originally used in battle and passed down several generations then hidden then recovered, restored and put on display. few of the wood or silk parts may be original but the blade is and still sharp. they are 400+ years old. Ships from pre WWI are restored and still sail as museum ships. unless you feel only ships in original condition and with all all original parts will get financed from a bank IYTU then any ship regardless of age can be found, bought, and sold. Banks today routinely give loans for POS cars with 150,000 miles and crappy maintenance histories. at a higher interest rate but they still do it.

 

[Drakon]

The more I think about, the more I think it comes down to design and materials. One can design features into the ship such that its components are easily replaceable, with minimum equipment, tools or dismantling of the ship. Move a deckplate, hoist the pump up and out on the pre positioned track, and hoist in the new one. Rack mounted electronics. Replaceable rib structures and internal skelaton.

Materials that are more duriable, can stand stresses better, which contributes to longevity, will help alot. But everything wears out or breaks down eventually. If you can design the ship such that failed items can be easily replaced, it will last substantially longer.

 

[G. Fieendish]

Re:This Thread
I tend to agree with the last poster, in that good design is one of the key factors in determining the longevity of a item....
With regards to durability, you have to balance factors such as cost over relibility, i.e is it cheaper to have a part that is cheap & easily replaceable or dear, but extremely reliable....

 

[Drakon]

With regards to durability, you have to balance factors such as cost over relibility, i.e is it cheaper to have a part that is cheap & easily replaceable or dear, but extremely reliable....

Depends on the system, and he survivablity of the ship and crew to a loss or failure of that component. How does that line go? "Its a nothing part unless you need it, and ain't got it." The really important stuff, the stuff that will kill you, or strand you way too far from a safe landing, that gets the best material and design.

The less important stuff, like ventilation fans, you can go cheap. Not real cheep, but still.

 

[Icosahedron]

Ventilation fans going 'cheep cheep' would probably compromise crew sanity after a trip or two. Best to pay a bit more for decent ones. :smirk:

 

[jwcarroll60]

It would seem that, on the average, that starships, with the minimum required maintenance, last for over a century. One would hope they last longer than the mortgage period (30 years).

The hull, barring major catastrophe, should last well over a century and still be viable. Internal systems, maybe a couple of decades, then requiring major repair/upgrade/replacement.

 

[aramis]

It's a 40 year mortage, at least in CT, MT, and TNE....

 

[Drakon]

The hull, barring major catastrophe, should last well over a century and still be viable. Internal systems, maybe a couple of decades, then requiring major repair/upgrade/replacement.

And making even hull elements replaceable, the ribs, skeleton and plating or skin, that makes a ship even more survivable. This would, I think, be doable using boths or some other kind of "primitive" fasteners. Keeping it air tight would be an engineering challenge, but possibly not too tough.

Of course, if, over the course of its life, it has its internals replaced, and upgraded, as well as its bones and skin, it could be practically immortal. The things that would kill such a ship would be more stupid things that pilots do, or economics, rather than mechanical faults or design faillure. It wouldn't die or wear out, but have to be killed.

 

[Drakon]

Some design elements that might lead to practical immortality for star ships:

1) Use anything that helps to quality repairs with the fewest number of simple tools. The less resources you require for maintenence, the more likely it will get done.

2) Make *all* components replaceable and accesible. This aids upgrades, as well as replacements. The easier it is just to replace the air scrubber or the J Drive, the less likely one will run around with a bad one.

3) No components or systems that requires actions or consumable resources (except the crew) to keep it from damaging something, should be used. You should be able to just turn off the power, and park the ship somewhere for a few years, and with minimal effort and resources, have a perfectly fine spacecraft. Fusion plants have an advantage over nuke plants.

4) Keep the design simple. keep systems simple. Less thing there are, the less that can break down.

5) While keeping the systems and component few, bring spares. Redundant systems help keep her running, and make failure of one a far less problem.

Thats all I can think of at this time.

 

[JAFARR]

I see 5 possibilities; 1 - Mothballed in space as in the Arrival Vengeance module. Assume in some area of space free of external dammage causing space debris; 2 - A smaller ship mothballed on the planet/moon's surface maybe in some hanger type area; 3 - abondoned and adrift in space; 4 - abandoned on a planet/moon; or 5 - crashed on some asteroid (crashing on a larger body would do enough damage as to assure that it is not usable ever.

1 & 2 would have the longest life expectancy, but might require more work to make ready for use. I remember back in the 70's or 80's someone discovered a whole warehouse full of brand new motocycles made just before WWII. All they needed to make them road ready was new tires, fresh oil and fuel. A tire dealer told me that new tires would last 8 to 10 years in storage before dry rot made them un-useable. So maybe 200 years with some de-mothballing taking 2 weeks to a month with the proper personal.

The other cases maybe a max of 50 years depending on other conditions with even more work to get them spaceworthy.

 

[Drakon]

I see 5 possibilities; 1 - Mothballed in space as in the Arrival Vengeance module. Assume in some area of space free of external dammage causing space debris; 2 - A smaller ship mothballed on the planet/moon's surface maybe in some hanger type area; 3 - abondoned and adrift in space; 4 - abandoned on a planet/moon; or 5 - crashed on some asteroid (crashing on a larger body would do enough damage as to assure that it is not usable ever.

1 & 2 would have the longest life expectancy, but might require more work to make ready for use. ... So maybe 200 years with some de-mothballing taking 2 weeks to a month with the proper personal.

The other cases maybe a max of 50 years depending on other conditions with even more work to get them spaceworthy.

Except for 5), I think that the rest can be engineered out. 5) is going to largely a product of chance and bad piloting, i.e. humans.

Another factor is economics. If the mode of travel is not, nor can be made, economical in the current business climate, whatever that climate might be during its lifetime, then it won't have a lifetime. There has to be cargo to be moved, or people, or safaries, or what have you. The good thing about ships is the fact they are mobile, so they can find better economic conditions.

 

[Icosahedron]

Some design elements that might lead to practical immortality for star ships:

1) Use anything that helps to quality repairs with the fewest number of simple tools. The less resources you require for maintenence, the more likely it will get done.

2) Make *all* components replaceable and accesible. This aids upgrades, as well as replacements. The easier it is just to replace the air scrubber or the J Drive, the less likely one will run around with a bad one.

3) No components or systems that requires actions or consumable resources (except the crew) to keep it from damaging something, should be used. You should be able to just turn off the power, and park the ship somewhere for a few years, and with minimal effort and resources, have a perfectly fine spacecraft. Fusion plants have an advantage over nuke plants.

4) Keep the design simple. keep systems simple. Less thing there are, the less that can break down.

5) While keeping the systems and component few, bring spares. Redundant systems help keep her running, and make failure of one a far less problem.

Thats all I can think of at this time.

Ah, music to my ears!

You're so darn right! Take my car as a present day example - you have to remove half the heating ducts from the radiator in order to change the headlamp bulb. Then the road safety people wonder why so many vehicles drive round with half their lights out! They need to talk to the designers, not the drivers. :nonono:
Maybe in the future, part of the type approval process will involve a man with two spanners and a screwdriver stripping the vehicle down to nothing and reassembling it. (Some hope!)

Unfortunately this sort of thinking, though helpful for the customer and the environment, doesn't sell new parts or ships - a major economic factor leading to short lifetimes.

 

[Drakon]

Unfortunately this sort of thinking, though helpful for the customer and the environment, doesn't sell new parts or ships - a major economic factor leading to short lifetimes.

Not so sure. Dead ships don't need replacement parts, only working ones. And knowing that the outfit who designed this ship had a lot of them still in service, sounds like a good selling point. When a ship dies, it will usually do it at the most inopportune time. Who wants to deal with the hassel, (let alone the potentially life threatening situation)?

Ship captains are going to want rugid, long life ships.

And then there is the improved resale value from selling off your long life ship. The rest of the market is full of ships that are close to making their last jumps.

 

[Ishmael]

that makes me think that perhaps a certain percentage of waste-space could give a positive dm to repair something, seeing as more waste-space means everything is easier to access. Unless the access is from outisde the ship ( like aircraft engines ).

I like to use variable effect rules from DSP's Starship book and roll for the craft's designer as to things like that for each new design. Every form of a Type'S', for example, will get its own quirks that way, if you see my drift...and each variant will get its own reputation.

 

[Icosahedron]

What the customers want and what the manufacturers are prepared to sell them are not necessarily the same thing (despite all the customer-first bull...)

Customers want machines and components that will last forever; manufacturers want to sell replacement parts or, better still, replacement vehicles, as often as possible.

Who is it that gets what they want in the real world??

If nobody else sells long-lived items, and the customer can be duped into buying your rot instead of your rival's, that's all that matters. The manufacturers couldn't care less about repair hassle; yes, that model had some problems, that's why we phased it out - try our latest model...
Nor do they care about resale; the cost of providing 20 year old spares is probably greater than the income generated - let the poor people eat our new cake.

 

[Icosahedron]

I like the waste space repair DM, Ishmael, I might just borrow that.

 

[Captain Midnight]

Never lose sight of the fact that manufacturers are in business to make a profit. They may put some restrictions on what they'll do to make more money (selling products they know to be unsafe, for example), but if they don't make money, they go out of business. There are always different valuations placed on different factors, too; some buyers may prefer low initial cost, and accept a lower resale value, while other buyers may be more interested in minimal maintenance costs, and be prepared to pay a slightly higher price on the front end. Yet another purchaser may want something more comfortable, and be willing to spend a little more for it, while another purchaser may be looking to spend as little as possible, and willing to accept some rather spartan accommodations in return.

If a ship is easier to maintain than another one, that is a factor that adds to the ship's value. If it provides extra value at the same price, then unless there is some other factor at work, it will capture a greater market share; if instead the extra value means that the ship has a higher price, its market share probably won't increase too much.

Manufacturers will be trying to balance the "profit per unit" and the "number of units sold" amounts to maximize total profit. Different manufacturers will have different strategies for doing so, and different abilities to produce efficiently. They have different abilities, motives, and resources, just like buyers do. The balances that each one brings to the transaction are what make markets complicated.

 

[Drakon]

Customers want machines and components that will last forever; manufacturers want to sell replacement parts or, better still, replacement vehicles, as often as possible.

Who is it that gets what they want in the real world??

If nobody else sells long-lived items, and the customer can be duped into buying your rot instead of your rival's, that's all that matters. The manufacturers couldn't care less about repair hassle; yes, that model had some problems, that's why we phased it out - try our latest model...
Nor do they care about resale; the cost of providing 20 year old spares is probably greater than the income generated - let the poor people eat our new cake.

I am not convinced. Yes, manufacturer want to get the most for the least work, just like everyone else. But when a starship dies, it can quite often kill or injure its crew too.

When a car dies, you can shove it over to the side of the road, and call a tow truck. For aircraft, its a bit more risky. You have to get down on the ground, and not die in the off field landing. We're talking space craft, where component failure can very easily kill your customer base. The last thing a starship manufacturer wants, is to get a reputation as a maker of death traps.

As for replacement parts for 20 (or 200) year old ships, I think this is where starting out with an upgradeable ship helps. Start with a base hull, and if you build it such that everything is replaceable, then every part is upgradeable as well. Its not a part for a 200 year old ship. Its a part for a 5 year old engine, or its 3 year old computer.