Space Warfare XI: La Zona Fronteriza
The return of this ongoing series on space warfare is inspired by recent comments in the Running on Rails thread, and also on Part V of this series, regarding laser weapons. Commenters Byron and Turbo10k independently raised the question of the threshold between deep space and local space, in maritime analogy between 'blue water' and 'brown water.'
Thus the image of the Spanish landing on Terciera in the Azores in 1583, showing the advanced state of amphibious doctrine at that time. Though the remainder of this discussion considers mainly 'blue water' action, in deep space at a higher techlevel. And here is an arbitrary but always appropriate link to Atomic Rockets.
Suppose an expeditionary force is approaching from deep space. For our purpose it makes no matter whether the attackers are in transfer orbit from Mars, Europa, the rings of Saturn, or from a wormhole.
The defenders may choose to defend from low orbit, or even from the surface. I argued in the first of this series, Space Warfare I: The Gravity Well, that the disadvantage of 'low ground' may be countered, or more than countered, by the advantage of concealment ranging from submarines to missile-launching trucks. In particular, surface launched kinetics are convenient and deadly against ships in low orbit. For the wider defense of local space, kinetics launched from low orbit can take advantage of an efficient Oberth effect boot to kick them into the teeth of an incoming attacker.
A defense based on the ground, or orbital forces, can also dispense with costly deep space ships with their specialized propulsion and long duration life support. Ground troops need only plain old barracks, while orbital forces can obtain provisions and support from the civil orbital infrastructure.
On the other hand, a close in defense means fighting amid that same orbital infrastructure, implicitly leaving it vulnerable to the attacker. Urban warfare is hard and costly for an attacker, but it is also pretty damn hard and costly for the city. There is good reason to fight the wolf at the threshold and not by the hearth.
Fighting at the threshold instead of the hearth may make the battle less interesting, because if we are fighting away from the clutter we don't need to worry about hitting civilians, can pretty well distinguish good guys from bad guys, and therefore can give free play to automated systems firing at Stupendous Range.
This battle is likely to be boring, but shame on us for complaining. These people aren't fighting for our entertainment - well, on a meta level they are, but to them it is sheer bloody murder. (Even if the battle is robotic, fortunes in hardware are being thrown away.) The battle is also likely to be Lanchesterian, which is of more consequence.
What constitutes the threshold and not the hearth will be determined first and foremost by weapon ranges, as the range of smoothbores set the traditional three-mile limit.
Even under the modest, midfuture assumptions I typically use, these ranges qualify as Stupendous Range. Consider a 1 gigawatt UV laser, zapping at 100 nanometers through a 10 meter main mirror - a main armament worthy of a laser star, but nothing magical. It can concentrate its beam onto a 1 meter spot at 40,000 km range, and burn its way through Super Carbon Nano Stuff armor at about 1 centimeter per second, a meter in less than two minutes of steady zapping.
At 400,000 km - lunar distance - our battle star can burn through a millimeter in less than 15 seconds (spot size 10 meters), scorching surfaces and destroying any sensitive surface equipment, such as sensors.
Kinetics, if launched at more than escape velocity, have nominally unlimited range. Their practical range is determined by flight time and target performance. If the target can veer farther in the time before intercept than the kinetic's deflect motors can reach, then it is home free. Otherwise it is at risk of a hit and must engage the kinetic with point defenses.
Kinetic target seekers, we will assume, have chemfuel deflect motors, with high acceleration but limited delta v, perhaps 3 km/s. (This is distinct from the initial boot that sends the bus toward the target.) If the target is a deep space ship with a high ISP drive, its acceleration is limited to the milligee range. At 3.5 milligees the target can put on 3 km/s in about 87,500 seconds, just over a day.
So if flight time is more than a day the ship can 'outrun' the target seekers. Less than a day, and it will have to engage them. And at a closing rate of 10 km/s the target seekers' intercept envelope extends to 875,000 km - twice lunar distance.
These are nominal figures, and highly sensitive to input assumptions, but they give us a sense of the scale of things. Given no ambiguities about who the players are, a range of 100,000 km is knife fighting distance in space. Relatively unsophisticated kinetics can reach out and touch you at distances approaching a million kilometers, and plausible midfuture lasers can scorch you at a similar distance.
You can defend a zone this large from low orbit, but your orbital infrastructure is vulnerable to an attacker at a similar distance. Thus the frontier zone, on order of a million km, within which your close-in defenses are effective, but beyond which you must mount any forward defense.
For the attacker it is the same picture, viewed from the other side. Within the defender's frontier zone you are exposed to direct attack by home defenses; beyond it you can only be engaged by 'forward' defense forces.
And for some acts of war - notably deep space blockade - you as attacker need never enter the defender's frontier zone. You need only engage departing ships after they leave the defended zone, or arriving ships before they enter it. Which could involve some interesting deep space chases, especially if the requirement is to board targets, not simply blast them.
A deep space blockade is in some ways easier to sustain than a traditional sea blockade. No storms will drive you off station, and while on station you consume only stationkeeping propellant.
The blockade constellation might be headed by a base station, a jumbo tender with most of the support functions, kept well back, and supporting half a dozen 'cruiser' laser stars fitted to carry boarding crews, gunships, etc.
In response to this threat, a defender who does not wish to pay for a full deep space force might build 'monitor' laser stars, not configured for true deep space missions but with sufficient delta v to force a blockader to engage or fall back onto an escape abort orbit that lifts the blockade.
Now for a little opera. The Hegemony need not rule planets, nor even dominate their local space; it is enough to blockade them. You can be independent, but you will be isolated. When people can't get their Rigelian green fuming brandy, governments tend to bend. The Hegemony's loose grip can be broken only by someone willing to build deep space forces and force it to actively defend multiple blockades ....
Related posts: Here's the Space Warfare series, plus some closely related ones. Note that my views are also a moving target - the form of killer bus I proposed in Part VII turned out to be hugely inefficient given even present-day guidance technology.
I: The Gravity Well
II: Stealth Reconsidered
III: 'Warships' in Space
IV: Mobility
V: Laser Weapons
VI: Kinetics, Part 1
VII: Kinetics, Part 2 - The Killer Bus
VIII: Orbital Combat
IX: Could Everything We Know Be Wrong?
X: Moving Targets
Also ...
Battle of the Spherical War Cows: Purple v Green
Further Battles of the Spherical War Cows
And last but not least
Space Fighters, Not
Space Fighters, Reconsidered?
234 comments:
«Oldest ‹Older 201 – 234 of 234Another cost of travel time is the low productivity of the vehicle.
Consider my rule of thumb, that a spaceship costs about as much per ton as a jetliner. But the jetliner can make a transcontinental round trip daily, while the spaceship makes perhaps one round trip per year.
Thus, space freight will (simplistically!) cost 365x as much as airfreight. For passengers more like 1000x, because you can't live in an airline seat for several months.
So. Fast space travel is expensive because it uses beaucoup energy. Slow space travel is expensive because your ships can only deliver a few cargo loads in their service lifetime, and those few loads have to pay for them.
Cyclers improve on the slow freight situation IF you can piggyback a slow production process onto the shipment.
Citizen Joe:
"Helium would also need to be held in cryo (dewars) which takes energy to maintain the cold temperatures."
In space? As long as you keep the cargo hold well-insulated from the reactor/engines, and equip those with a good radiator, you'll barely feel any heat.
Or you could just transport the helium as a gas. Requires more structural mass to contain it, and leaks out more, but the technology is simpler and it won't explode if it overheats.
"Tritium, which is much easier to make than He3,"
Not if you're mining the helium-3 directly as helium from Luna or the gas giants.
Tritium is no easier to make in space than it is here on Earth. Why bother shipping it all the way from there?
Oh, and don't forget that your ships are now carrying radioactive material. Don't let 'em crash!
"has a half life of 12 years."
Which is an excellent reason to ship it quickly!
Or better yet, not ship it, and instead ship the non-radioactive materials that can be bred into tritium locally.
Rick:
"So. Fast space travel is expensive because it uses beaucoup energy. Slow space travel is expensive because your ships can only deliver a few cargo loads in their service lifetime, and those few loads have to pay for them."
The question is, how do the one-time costs of a spaceship compare to the per-trip costs of a spaceship?
If one-time costs are low compared to per-trip costs - either because spaceships are cheap to make or because they last a long time before needing to be decommissioned (which they well might, if they spend most of their time idling with no moving parts) - then it's more efficient to build a bunch of ships and send them on slow trips.
If one-time costs are high compared to per-trip costs, then you need to make good use of the spaceships you have, by making sure they finish their mission quickly to start on a new one.
If building ships is the main bottleneck, for any given ship, the amount of profit it makes can be estimated as being proportional to the amount of cargo it carries divided by the amount of time it takes to carry it. (Shorter trip times let you start on the next trip faster, thus carrying more cargo total over the course of multiple trips.) Since multiplying a ship's mass by 1000 only slows it down by a factor of 10... But then again, multiplying your shipping costs by 100 (assuming energy fuel is the main problem) will speed you up by a factor of 10. So you can increase your profit-to-cost efficiency by a factor of 10 without changing transit time, simply by shipping more stuff at once!? Except, of course, that the amount of cargo you can carry is limited by how big your ship is, and if ships are expensive, then really big ships will be really expensive.
If launching ships is the main bottleneck, then having ships arrive quickly is much less useful in terms of letting you start a new trip sooner, since launching the same ship again would cost only a little less than launching a brand new ship. My first instinct is that then you might as well have your spaceships go as slow as possible, so you'll earn more money in total. However, while technically true, for sufficiently valuable cargo it may be the case that the savings you make in this manner are neglible compared to factors not included in the model, such as that the earlier you get your money, the faster you can start investing it into making more profit.
Ugh. I've never been good with money.
"Cyclers improve on the slow freight situation IF you can piggyback a slow production process onto the shipment."
It still strikes me as much more efficient to put your slow production process at source or destination planet, where you have the resources for a good industrial complex, and don't need to accelerate said industrial complex to interplanetary speeds. Also, by performing your processing at the source planet, you can just ship refined products and dump the waste without having to accelerate it (since accelerating large masses of waste would be seriously expensive).
Yes, finishing production first before you ship things does take a little more time, but it's also much easier and cheaper. Possibly cheap enough that you can now afford to send the product on a steeper orbit.
I said:
"So you can increase your profit-to-cost efficiency by a factor of 10 without changing transit time, simply by shipping more stuff at once!?"
Nope. The increase of profits with faster trips was due to starting another trip faster - which will have its own energy costs. Factor in the additional energy costs of performing more trips when they're individually shorter, and now energy costs increase with the cube of travel speed.
You can prove pretty much anything with numbers as long as they're the wrong numbers :)
If building ships is the main bottleneck- You don't build ships. You keep the expensive parts as little in number and in as much use as possible, while the inexpensive parts are sacrificed in long trips. This goes back to the cargo net and tug shipping-if the tug costs a lot, then you keep it for reuse, while the inexpensive, low-mass net is sent away for a half-decade-long trip.
"So. Fast space travel is expensive because it uses beaucoup energy. Slow space travel is expensive because your ships can only deliver a few cargo loads in their service lifetime, and those few loads have to pay for them."
Interesting point, but over-simplistic. Fast space travel costs lots of energy, but you can tweak 'energy' costs in your setting to allow you to gain enough profit to cover said costs quickly, over multiple, fast trips. 'Energy' costs include anything from propellant, fuel, drive costs and wear and tear of all previous components together.
Slow travel, on the other hand, is more impractical than suggested. Basic human instincts asks the accountant for several low profits than a few big ones, as it gives the investors the impressions that their business is 'working' and that they have more control over it. The only possibility would be either:
-Humongous payloads
-Low rate of consumption/very high cost
Humongous payloads will take the form of Hohmann barges, using minimal ship/cargo ratios, or the 'net'. Difficult to achieve without a mature industrial base or easily exploitable resource in space, both of which are separate and cumulative difficulties, that add to shipping...
The second methods are interchangeable, but have the same effect; the consumer will not care if they come once every six years. He3 is an example of both. Very little is used for lots of power, AND it could be expensive.
Economics of your setting are extremely dependent on historical, cultural and technological factors. We needed to define setting to space war, at least roughly, but for economics, which is much more sensitive, it is even more important to do so.
Another point, not on economics.
Its about the fission fragment rocket. From a rough read on the wiki article, with "specific impulses of greater than 100,000 possible using existing materials".
That seems awfully high.
Knowing that nearly all drives trade isp for thrust, I guess this one has pathetic thrust, ie ion-engine thrust, limited to deep space use. If we pump the reaction chamber with hydrogen, as in typical NERVA drive, what happens? Some thrust I guess, and we have a very good VASMIR equivalent. But since it has only been briefly mentioned, I'm sure to be making a massive error somewhere.
Yes, fission-fragment rockets have pathetic thrust. From the numbers I've been able to find, they have thrust comparable to fission-electric, but much better exhaust velocity - at the cost of spewing radioactive exhaust and using technology that, while on the drawing board, still needs to be developed. I expect this would mean that you have effectively infinite delta-vee, but still take a long time to get anywhere due to your low acceleration.
See here for some numbers.
If you could somehow design a fission-fragment rocket to trade your excessively high exhaust velocity for thrust (as has been suggested for some fusion rockets) without losing its high power density, it could be a very useful propulsion mechanism. A quick calculation on the numbers listed on the page I linked suggests they're expecting a power density of 10 MW/ton. I think that's per ton of reactor rather than per ton of ship, but I can't be sure.
I have seen proposals for a nuclear reactor that uses fission fragments to make electricity, which would theoretically have better efficiency than the thermal-electric ones we're using now. If anyone can get it to work.
Turbo10K said...
"Another point, not on economics.
Its about the fission fragment rocket. From a rough read on the wiki article, with "specific impulses of greater than 100,000 possible using existing materials".
That seems awfully high."
An externally initiated solid fission rocket would have an output of around 1 kilowatt-day per cubic millimeter...a cubic meter "motor" would mass about ten tons and produce about 1 GW for 1000 days. The neutron beam generator would likely mass about 40 tons, and the generator would mass another 40 tons. Now all you need to do is figure out how much that all that costs to build...
Ferrell
P.S.,
If you dump a propellent into the output of the above discribed fission rocket, it will boost thrust, exactly like the afterburner on a fighter jet.
Ferrell
Milo, I now see where we differed. Your argument makes much more sense now that I see your assumptions. I, of course, assumed that cargo was fairly valuable relative to shipping costs. Still, in some ways, we're both right. The steepness of the orbit is determined by the value of the cargo. We just used different starting values.
On the rest, energy costs seem like something that will be a real game-changer for any setting. If they're high, then stuff goes slowly, and ships are expensive. If they're low, then stuff goes fast, and ships are cheap. Still, it might be that manufactured goods sink in price relative to food. It's far easier to turn energy into a computer than a burger. Just a thought.
On an unrelated note, I've given more thought to chases in space. It turns out, it's best for the pursuee to launch kinetics when the pursuer is farthest behind. This gives maximum overtake time, and thus maximum lethality when it hits. And the fact that the pursuee will have significant velocity over the pursuer makes dramatic chases all a matter of timing. Still, there is the problem of stopping at the end.
Actually, dumping remass into the exhaust isn't quite like an afterburner, tempting though the comparison may be. An afterburner adds extra fuel, which, burning at the back, adds thrust, but not as much as it would have if the same amount were used in the normal engine. A mass-enhancement system only adds remass, which doesn't increase system energy. It cuts velocity and adds thrust.
Byron:
"It's far easier to turn energy into a computer than a burger."
There are plenty of ways in which plentiful energy would make agriculture easier: climate control for greenhouses, manufacturing of artificial fertilizers, removing the salt from seawater to make it drinkable, etc. And of course, transporting the food once you're done growing it. Actual cooking also uses a variety of energy-intensive processes.
Granted, it's still true that not all products are going to change price at the exact same rate. I wouldn't dare predict which would benefit most from reduced energy costs, but - if you want space trade - you have to justify why energy cost reductions have had a bigger impact on the cost of space travel than on the cost of manufacturing the stuff they're carrying.
"when the pursuer is farthest behind"
Remember that farthest behind depends on both your relative positions and your relative velocities.
In fact, I thought of an interesting situation: consider a "pursuee" that is actually currently behind the "pursuer", but is moving so much faster that the "pursuer" can't accelerate enough to catch up with its velocity! The "pursuer" gets one chance to shoot at the "pursuee" as it passes by, but if it fails to score a kill, it loses. This would actually be a quite good time for both sides to use kinetics.
"Still, there is the problem of stopping at the end."
Remember what I said about "ring-outs". If you've pushed the pursuee to the point that it can't stop at its destination, then you've effectively won the chase even though your quarry is still alive.
This can be convenient for authors if you find you need a way to have the heroes lose a particular encounter without killing them.
"Actually, dumping remass into the exhaust isn't quite like an afterburner, tempting though the comparison may be."
The mechanism is different, but "increase thrust at the expense of reduced delta-vee" for spacecraft is conceptually pretty similar to "increase thrust at the expense of reduced range" for airplanes. The most important difference is that airplanes with afterburners typically only use them in emergencies, since air friction means brief higher thrust has little effect on your long-term speed. By contrast, spacecraft will often find their "afterburners" help them complete interplanetary cruises faster.
Your scenario is more of an interception then a pursuit. My concepts were worked out for an (ultimately short-circuited) RPG adventure in which the heroes rescue a spy, and then have to outrun a ship trying to stop them from getting away. Their ship leaves first, but is of lower acceleration, and delta-V is pretty much irrelevant. In that case, my statement stands. On the flip side, it's best for the pursuer to use kinetics as late as possible.
And while energy makes agriculture easier, I can't simply use it to grow food faster, or to do much to increase the yield.
"Your scenario is more of an interception then a pursuit."
A pursuit is simply an interception where both sides started near the same point.
"And while energy makes agriculture easier, I can't simply use it to grow food faster, or to do much to increase the yield."
You can use energetic irrigation/fertilization infrastructure to make arable land from previously impractical plots, thus increasing yield. You can also reduce the amount of crops that are lost to drought, pests, disease, etc. And you can use automization to increase the amount of crops you can sow and care for with a given amount of work.
Granted there's not much you can do to actually make plants grow faster. More sunlight on a plant just causes it to get scorched, not grow faster. However this is throughput vs latency again.
Wow - Blogger actually split this thread!
Long mission spaceships won't really be free of moving parts (and thus wear and tear). Human carrying ships have a complex life support system with constant activity. The drive engine, which may operate for much of the trip, is designed for maximum power density, meaning intense heat loads and other effects.
Ship structures may last for generations, but onboard systems will require maintenance and servicing between missions, and in some cases during missions.
"Long mission spaceships won't really be free of moving parts (and thus wear and tear). Human carrying ships have a complex life support system with constant activity. The drive engine, which may operate for much of the trip, is designed for maximum power density, meaning intense heat loads and other effects."
I was talking about unmanned cargo ships, and I was specifically discussing how they're costing you little while they're coasting with the engines turned off. So neither of these applies. Regardless of whether they use Hohmann trajectories or steeper ones, I expect unmanned cargo ships to be built with a simple and robust design. At least as much so as the satellites of today, which operate without being serviced for years, doing far more actual work than these cargo transports would for much of their trip.
For manned spaceships, of course, you have a strong incentive to make the trip as fast as possible.
Need for servicing during missions can happen to anyone in a freak emergency, but it's most likely to be a concern for military ships, which by their nature have a heightened chance of encountering freak emergencies. Such as someone shooting at you.
For unmanned ships, you would probably deal with malfunctions either by just writing the ship off as a loss, or by letting it coast until it's close to its destination, at which point you can send out a tugboat to meet it, then push it to somewhere that it's more convenient to try to make repairs (like a space station if you have those).
Passenger ships would probably have a technician on board just to make the passengers more comfortable, even though he'll rarely have much work to do.
Fair points. Slow cargo transports could be much like river tugs, small core spacecraft handling much larger cargo pods.
Robotic craft for bulk cargo will be written off if they have serious malfunctions (as already happens with space launches).
But I think that life support for human carrying ships will turn out to require substantial maintenance during missions. The drive engine and other systems, not so much; liners might just have a tech or two onboard, as you suggested.
"Robotic craft for bulk cargo will be written off if they have serious malfunctions (as already happens with space launches)."
Yes, but a multi-kiloton interplanetary hauler (and its cargo) may be worth more than a present-day satellite, and a spacefaring civilization should already have the infrastructure in place to more easily and cheaply access and repair spacecraft. They might still write some ships off if it's not economical to save them, but it wouldn't be like today where you more or less have to write satellites off no matter how many millions of dollars you're losing, because the capacity to fix them simply doesn't exist.
"But I think that life support for human carrying ships will turn out to require substantial maintenance during missions."
Well, maybe if you're counting the cooks as part of the life support staff :)
I don't think that keeping the air pressurized, at the correct temperature, with the correct oxygen ratios, and such would be an issue in a properly-functioning spaceship. Those seem to be within the capabilities of computer control systems.
They'll still have a life support engineer anyway, though, for the reason I already outlined. And of course, they'll do thorough checkups between trips.
Technically even a navigator is dispensable for liners expecting uneventful voyages, but passengers are definitely not going to like that idea.
But you should hedge your bets anyway. It's far better to have a tech on board and not really need him than to need him and not have him. I would think that anything with very high performance would need a mechanic on board. We don't really do that now, but that's because the ships get serviced after every mission. The ISS doesn't, but they have people to repair it.
Part of what will drive space colonization will be a fundamental shift in the psychology of designers of spacecraft. Currently, everything that goes up, with the exception of the shuttles, is going up once, and that's it. It has to work that time, and when it's done, it's useless. When people stop thinking of spacecraft as disposable, which the shuttle sort of is, considering it's servicing requirements, and start thinking of them more like ships or aircraft, we'll start to see more activity in space. That was one of the oddest things about spacecraft design documents when I was doing my project. SMAD spent a lot of time talking about how it was necessary to failure-proof everything. I didn't have to worry as much, because the crew could fix things. When we get there, it will be a huge reduction in costs. Also, they won't have to be designed for each mission.
Seems like there are four routes:
1. Design a failproof vehicle that will last the duration of the flight.
2. Design a self repairing vehicle.
3. Design a vehicle with life support for a crew of technicians to fix any problems in flight.
4. Design a super fast vehicle with repair crews but just store supplies.
The cyclers I keep suggesting follow model 3. We can get to the moon and back. But the long trip through interplanetary space is harmful to human life. So the trick I use is: Fly to the moon (the cycler) then move the moon to the destination, then fly to the destination. That is also the model for cruise ships. You drive on in Miami, party for a couple weeks, then drive off in San Francisco. Model 4 would be: Rent a car (taxi) to get to the airport. Fly 4 hours. Rent a car at the other airport. One big difference is that in model 3, you get to take YOUR car while in model 4 you have to use A car.
"1. Design a failproof vehicle that will last the duration of the flight.
2. Design a self repairing vehicle.
3. Design a vehicle with life support for a crew of technicians to fix any problems in flight.
4. Design a super fast vehicle with repair crews but just store supplies."
In other words, make sure your vehicule doesn't need repairs (1, 4) or repair it when in use (2,3).
Except that 'self-repairing vehicule' and 'a crew of technicians' is pretty much the same, just different reapir methods. Repairs, just liek any other operation, can probably be fully automatic, and programmed for most errors.
"Well, maybe if you're counting the cooks as part of the life support staff :)"
I wonder how you can cook in micro-gee...some much stuff we eat relies on convection and such, all wierd stuff will happen in space.
"Robotic craft for bulk cargo will be written off if they have serious malfunctions (as already happens with space launches)."
Not really. If the ship malfunctions after launch, it will continue coming towards you, at interplanetary speeds. Today, we just write them off because:
a-A repair mission costs ten times or more the cost of that mission
b-The rocket will break up, explode in flight (preprogrammed self-destrcution) or fall back down in a few. An interplanetary bulk cargo ship will:
a-Drift towards you at initial velocities
b-Cause lots of trouble because of a
Whatever happens, you will have to deal with that craft, even if it won't strictly be repairs. You might divert it with an intercept mission, but I believe adding repair equipment onto the intercept mission won't cost a lot more and will get you back an operational ship.
-will continue later-
"When people stop thinking of spacecraft as disposable, which the shuttle sort of is, considering it's servicing requirements, and start thinking of them more like ships or aircraft, we'll start to see more activity in space."
Does a Boeing 747 have a mechanic and an ample supply of replacement parts onboard? What about an oil tanker?
I see them as being serviced, if at all possible, between missions, not during them. If you can at all help it, repairs should be conducted in a properly equipped spaceyard. Spaceships will be designed with multiple redundancy so if some something breaks, they can still make it to a spaceyard for repairs.
Putting a technician onboard was easy in the days of sailing ships, when mending your engine could be done with needle and thread. The more complicated the technology, the more advanced infrastructure is necessary to fix it properly, infrastructure that is hard to carry with you.
"SMAD spent a lot of time talking about how it was necessary to failure-proof everything. I didn't have to worry as much, because the crew could fix things."
I'm sorry, but I don't want my life support's integrity to be reliant on "oh well, we can fix it when it breaks". I don't want my ability to not get stranded in space be dependant on the engineer's ability to quickly jury-rig a new fusion reactor from pocket lint and duct tape when the old one breaks.
Milo:
SMAD was mostly about unmanned satellites. Even then, when we speak of life support breaking, I'm thinking of, say, a filter needing to be replaced, not a wholesale meltdown. Think of the ship like a computer. Current systems require that nothing goes wrong. I'm picturing that if it crashes or, say, a setting gets messed up, the humans on board can fix it. That doesn't mean they can deal with the hard drive completely dying. That's a completely different set of issues.
Plus, we apparently differ in how we think about spacecraft. You think in airplane terms, while I think in terms of naval vessels. In some ways, the naval model is better. Spacecraft won't crash if the engine breaks (at least not most of the time) and they're usually out for weeks or more. I'm just pointing out that a large part of the reason spacecraft are so expensive is the amount of failure-tolerance built in to deal with stuff a human could do if on-site. Even on your 747, what happens if an engine dies? The crew can try to restart it and if that doesn't work, glide to a crash-landing. Modern spacecraft are doing their best to make sure the engine doesn't fail, and all the other parts, too. I'm probably not making much sense right now, but I may try again later.
I'll give you that once you have crew on board anyway, it's good for one of them to know how to do maintainance, just in case - not because it's something that will come up often, but because losing even one human-carrying ship once in a long while is undesirable risk. This doesn't equate Rick's "substantial maintenance during missions", though. It seems to me that if you have the technology to build all the complex components of life support that can't be allowed to fail, you should also have the technology to build the simpler components to be robust enough to not need constant babysitting.
I think I understand what you are trying to say - that as damage and failures come in degrees, so does the corresponding repair work. An engine fire can be handled and damage minimized nearly automatically in a modern jet, I believe that automation in space craft would lead to most problems being dealt with efficiently. For harder repairs, ie software crashes, damage to areas inaccessible to repair bots (bulkheads, ventilation conduits, other places robots have difficulty accessing) we could have technicians with welding equipment and such. I do however see them staying inside the ship, and commanding a multi-purpose repair bot (Waldo with arms and directional jets) much like surgeons do today; with a screen and joystick...
With modular ships however, the best redundancy would probably be just disposing of damaged parts, as to reduce total weight and increase chances and speed of return-to-base. One example is having to deciding to dump the reactor and switch to emergency one, or attempt to repair it.
"Technically even a navigator is dispensable for liners expecting uneventful voyages, but passengers are definitely not going to like that idea."
Things will change when people have self-driving cars and robot air transports...We won't have a navigator perhaps, but we will have a commander/pilot that takes trajectorial decisions, even if it is more like a modern 747 (or 380) taking a several month trip on autopilot. In other words, you point and it does. You just twiddle thumbs until completion.
I agree with Milo in that life-support will be the last-to-fail equipment in the ship, as human carrying ships are valuable, and during a war, they constitute the only decision making force. Repair efforts and survival will all revolve around this complex but extremely robust and redundant base to work upon or from...
"Things will change when people have self-driving cars and robot air transports...We won't have a navigator perhaps, but we will have a commander/pilot that takes trajectorial decisions,"
Yes, of course, but this can be done by ground control. Passenger liners don't generally expect to run into anything that would require quick thinking. A chartered liner should already know what route it's planning to take before it even lifts off.
If you want an example of human repair work, look at Skylab, and the assembly work on ISS. (OK, that's not a repair, but it's close enough.) Humans have gone outside and fixed things that machines either broke or were deemed too expensive to do. An unmanned satellite has to do it all automatically. I'm just suggesting that costs could fall a lot if we were able to remove the extensive quality-checking on things like that. It's far easier to have a human reboot the computer if it glitches than to build two redundant computers and test them to the utmost. The above is in case of non-instantaneously-critical systems, of course.
Yeah, I agree. I'm just saying that the most defining systems on a ship - life support, engines - are instantaneously critical. On a passenger liner, the less critical systems would probably be little different from the stuff found in a planetside hotel, aside from that zero gravity thing.
Of course part of the problem is that Rick said he thinks ships will need constant maintainance, but didn't elaborate what kind of maintainance he envisions...
I think life support will require ongoing maintenance. But your earlier question about whether that included the cook is to the point. A lot of trouble can start in the galley, like a good grease fire. And there's plumbing that can clog, etc.
If you have long term, closed cycle life support, you have some form of farming/gardening going on, with a lot of complex and varied activity cycles that probably need some maintenance.
Drive engines and the like are a different matter - there probably isn't much maintainable/repairable by an onboard toolkit. They'll be serviced between missions, with building cage facilities available.
So now I'm driven to ask - how do you put out a fire in zero gravity? You can't just pour a bucket of water on it. Then again, zero gravity may actually make fires less hazardous because they end up choking themselves. Just turn off the ventilation system for a while.
Farming obviously needs farmers, unless your closed life support is based on a (laughably absurd) self-supporting ecosystem with the passengers harvesting it as hunting-gatherers. But I don't think liners will have closed life support systems. Sailing ships didn't. Closed ecosystems are for true habitats, aboard colonies and/or space stations. Those would obviously have technicians - and for that matter, those would also be where ships dock for repairs.
Fire suppression all really depends on the individual spacecraft. A small lunar shuttle or a modest space station definitely wouldn't use carbon dioxide or halon suppression systems because of the nasty undesired consequences they would both result in. I guess you're then just left with a liquid-foam option, fired from some kind of jet nozzle. But that has the chance of damaging on-board equipment.
If you've got a Goliath sized spacecraft like the International Space Station then you could get away with using a regular fire extinguisher.
Life support aboard nuclear submarines would be relevant, with the proviso that in an emergency subs are normally just a few minutes from Earth surface environment. Spaceships have to make do with what they've got till they get where they're going.
Oh and something else. This a good time to bring up compartementalization in spacewarships, as it can save a lot of stuff (including people) if anything happens...
Ships would start looking like the setting of HyperCube or something.
Hypercube:
http://en.wikipedia.org/wiki/Cube_film_series
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