Starship hulls, an idea or two

[DAgent]

So, we probably all now that certain real life spacecraft have an external hull and a separate internal hull, with the idea being that if the outer hull gets damaged no one gets sucked/blown (anyone know what the correct term should really be?) out into space.
And we probably all know there's a risk of hull breaches from things as simple as stellar dust when traveling at high speeds.
What I am wondering though is what kind of risk would a ship be if it's hull was incredibly thick, and what other kinds of issues would this bring?

For example, would a half meter thick hull made of the strongest, non brittle metal we know in real life, make any difference against the risk of hull breaches? Be it from weapons (either real life or fictional) stellar dust, micro asteroids and general collisions?
Would it increase the ships mass so much that the engines would need to work harder to accelerate or slow down? What other kind of issues might such a hull pose, either in terms of benefits or drawbacks?
Would an even thicker hull, say four meters just for the sheer hell of it, get any more benefits from it, or suffer even greater drawbacks?

 

[Swank]

It would take incredible amounts of fuel to move and build it.

Radiation and impact resistance would be better.

 

[bretbernhoft]

I agree with @Swank that the resources required to move and build such a vessel would be astronomical. How would that be accounted for, OP?

 

[Yozh]

For the concerns raised by Swank and bretbernhoft, seems like it would make a difference whether this ship was built on a planet surface and needed to break free from gravity, vs a ship built in space. In any case, a thick hull would take a larger amount of materials, so it would probably only make sense with a a cheap and plentiful material. Basically a floating stone fortress.

 

[Astro Pen]

I'd concentrate on making it as narrow and long as possible. (Low frontal area). Then the gauge of the front section can be relatively thick without impacting the overall mass as much.

 

[Venusian Broon]

So, we probably all now that certain real life spacecraft have an external hull and a separate internal hull, with the idea being that if the outer hull gets damaged no one gets sucked/blown (anyone know what the correct term should really be?) out into space.
And we probably all know there's a risk of hull breaches from things as simple as stellar dust when traveling at high speeds.
What I am wondering though is what kind of risk would a ship be if it's hull was incredibly thick, and what other kinds of issues would this bring?

For example, would a half meter thick hull made of the strongest, non brittle metal we know in real life, make any difference against the risk of hull breaches? Be it from weapons (either real life or fictional) stellar dust, micro asteroids and general collisions?
Would it increase the ships mass so much that the engines would need to work harder to accelerate or slow down? What other kind of issues might such a hull pose, either in terms of benefits or drawbacks?
Would an even thicker hull, say four meters just for the sheer hell of it, get any more benefits from it, or suffer even greater drawbacks?

I would use the solution that Alastair Reynolds uses for his lighthuggers - namely putting a shield of ice at front. The reason for using ice/water as a major part of your hull is pretty easy to see.

First water is one of most plentiful compounds in the universe - you are probably going to find it everywhere you go.

Second is that it is not as dense as the metals you will be probably using, so you can save weight or have a much thicker slab as protection - especially at the front where micro asteroids and all sorts will be impacting your ship when you are at speed. (When you reach your destination just find a water source and re-grow your nose again, so...)

Third - relatively easy to mould or put in place. You could freeze it as AR does on the forward cone, or have water tanks around the crew compartments.

Fourth - water is a great thing to have a lot of. We need it to survive, but it can also be split into oxygen and hydrogen, both of which have great uses aboard a spacecraft!

Fifth - water/ice is actually better at protecting you from cosmic rays than any metal. You have to have a very thick slab of metal to get a good level of protection.


The biggest drawback of any of our current ideas about spacecraft is basically weight. To build a spacecraft that can sustain even a small number of humans requires a great deal of life support and protective shielding. This isn't too bad if you are only planning to go between the Earth and Moon, and perhaps Mars. But we are so far away from a good interstellar engine that could even push a small unmanned probe to the nearest star, that such craft remain firmly in the realm of SF.

 

[Swank]

My initial answer was about hulls on ships using known science. F=MA, where increases in mass require a proportionate increase in force for the same acceleration. But this isn't the science section of the forum. So what about speculative SF spaceships?

The first thing you have to decide is what you're armoring against, and whether you have options other than armor. A spaceship has a perfect field of view around it, so if you are primarily concerned about high speed matter, you might consider an active defense that destroys incoming micrometeorites or diverts them. Lasers, rail guns, radar are all light compared to armor.

But if you're concerned about munitions, then you have to assume your system could be overwhelmed and you might want something dumber. However, you still have options like the reactive (explosive) armor used on tanks to lower their weight. Or you might be able to deploy rapidly spinning shells around your ship that would deflect incoming projectiles and then be repaired.

If radiation is the problem, you want to use substances high in hydrogen - like water or hydrocarbons (plastic). Water and other fluids could be rapidly moved to problem areas - picture the space between the inner and outer hull being variable, like a ball rattling around inside another ball. The ultimate fuel/shielding material would probably be metallic hydrogen.

Magnetic shielding is also a possibility, with strong field either diverting or channeling both radiation and particles from certain vectors. A ramjet takes advantage of this by funneling the bad stuff in front of the ship into the engine and leaving a ring of crew area around the engine that is relatively unmolested. Even if this isn't your primary drive, it might still be worth the expense to have a scoop out front.

You can also build your ship for survivability, with fairly thin self-healing hulls that allow micro-impacts to go right through with a minimum amount of damage, and a relatively small core of important systems having the only heavy armor. This would be something of a statistics based approach - how likely and how often do you expect impacts.

Then we have forcefields (whatever those are). In the various Treks and Wars, force fields are effective but can be overwhelmed. They can be independent of the ships inertia or transmit impact inertia to the structure. In the famous Macross (Robotech) anime, they can't build a full force field, so they have three tiny ones that they move around the hull to intercept missiles.


That's all assuming that you have a delta v limit associated with your drive system. But if your drive uses some speculative principle, maybe mass isn't an issue. Maybe you can just hollow out an asteroid and power it up. But for the sake of some sort of limits, you might consider that such a drive can only move a certain volume, or has a slow response, or something else that feels like a compromise.

 

[Swank]

Another very speculative type of shielding would be having a double hull with super heated plasma magnetically suspended inside. Micrometeorites would rapidly burn in the high temps; the plasma acting like an atmosphere on steroids.

 

[Wayne Mack]

I would wonder about how to manufacture a solid, half meter thick hull. How would it be possible to join two thick blocks and not have a fairly fragile joint? How would one weld together two half meter surfaces? Another possibility would be to build the half meter thickness by overlaying multiple thinner sheets. In this case, I would be concerned with different rates of thermal expansion between the layers, which could cause layers to buckle and perhaps fracture. I'm not sure that the added thicknesses of metal would provide any structural advantage over alternate fillings such as foam or sprayed insulation.

The thing that has bothered me the most on spaceship construction is the inclusion of viewports. Clear materials would seem to be more fragile than the hull material being discussed. And how does one establish a seal between the hull and viewport that wouldn't be in danger of degradation over years, decades, or perhaps centuries? Does someone don a spacesuit and go out and caulk the windows every couple of years?

 

[Swank]

I would wonder about how to manufacture a solid, half meter thick hull. How would it be possible to join two thick blocks and not have a fairly fragile joint? How would one weld together two half meter surfaces? Another possibility would be to build the half meter thickness by overlaying multiple thinner sheets. In this case, I would be concerned with different rates of thermal expansion between the layers, which could cause layers to buckle and perhaps fracture. I'm not sure that the added thicknesses of metal would provide any structural advantage over alternate fillings such as foam or sprayed insulation.

The thing that has bothered me the most on spaceship construction is the inclusion of viewports. Clear materials would seem to be more fragile than the hull material being discussed. And how does one establish a seal between the hull and viewport that wouldn't be in danger of degradation over years, decades, or perhaps centuries? Does someone don a spacesuit and go out and caulk the windows every couple of years?

Aside from using nanotechnology to grow the halves together, you could simple run current through the halves in space and they will perfectly spot fusion weld together - like how Schwinn used to make bicycles. Welding in space works well because there is no atmosphere to pollute the welds and little heat loss.

However, space is a perfect place to cast metals - so I would simply cast the whole thing in one go. You could even cast it around critical components as long as they don't touch in the process.


I imagine that directed sunlight, light gas pressure and centrifugal separation could make huge castings from asteroid ore relatively painless.

 

[DAgent]

I agree with @Swank that the resources required to move and build such a vessel would be astronomical. How would that be accounted for, OP?

That's what I'm trying to figure out.

 

[DAgent]

For the concerns raised by Swank and bretbernhoft, seems like it would make a difference whether this ship was built on a planet surface and needed to break free from gravity, vs a ship built in space. In any case, a thick hull would take a larger amount of materials, so it would probably only make sense with a a cheap and plentiful material. Basically a floating stone fortress.

I don't think I've seen anyone have a spaceship made out of stone, except maybe Krull. But that was really more of a mountain.

 

[DAgent]

I'd concentrate on making it as narrow and long as possible. (Low frontal area). Then the gauge of the front section can be relatively thick without impacting the overall mass as much.

I've actually been working on a similar idea for a ship, long and narrow and thick at the front, for a very different reason.

 

[DAgent]

I would use the solution that Alastair Reynolds uses for his lighthuggers - namely putting a shield of ice at front. The reason for using ice/water as a major part of your hull is pretty easy to see.

First water is one of most plentiful compounds in the universe - you are probably going to find it everywhere you go.

Second is that it is not as dense as the metals you will be probably using, so you can save weight or have a much thicker slab as protection - especially at the front where micro asteroids and all sorts will be impacting your ship when you are at speed. (When you reach your destination just find a water source and re-grow your nose again, so...)

Third - relatively easy to mould or put in place. You could freeze it as AR does on the forward cone, or have water tanks around the crew compartments.

Fourth - water is a great thing to have a lot of. We need it to survive, but it can also be split into oxygen and hydrogen, both of which have great uses aboard a spacecraft!

Fifth - water/ice is actually better at protecting you from cosmic rays than any metal. You have to have a very thick slab of metal to get a good level of protection.


The biggest drawback of any of our current ideas about spacecraft is basically weight. To build a spacecraft that can sustain even a small number of humans requires a great deal of life support and protective shielding. This isn't too bad if you are only planning to go between the Earth and Moon, and perhaps Mars. But we are so far away from a good interstellar engine that could even push a small unmanned probe to the nearest star, that such craft remain firmly in the realm of SF.

I never would of thought of icing up the hull at all, but I do see where your coming from there, and I do like the image it gives me of an icicle like spaceship. But I'm more thinking along the lines of general overall purpose, something that could protect from attacks as well as radiation and so on. I can't see it provide much attack against energy weapons, unless it's exceptionally thick.

I'm also thinking it might not last long on a ship meant to study gas giants or solar activity, but could the same premise be used to ice up the space between an inner and outer hull to have a similar effect?

 

[DAgent]

My initial answer was about hulls on ships using known science. F=MA, where increases in mass require a proportionate increase in force for the same acceleration. But this isn't the science section of the forum. So what about speculative SF spaceships?

The first thing you have to decide is what you're armoring against, and whether you have options other than armor. A spaceship has a perfect field of view around it, so if you are primarily concerned about high speed matter, you might consider an active defense that destroys incoming micrometeorites or diverts them. Lasers, rail guns, radar are all light compared to armor.

But if you're concerned about munitions, then you have to assume your system could be overwhelmed and you might want something dumber. However, you still have options like the reactive (explosive) armor used on tanks to lower their weight. Or you might be able to deploy rapidly spinning shells around your ship that would deflect incoming projectiles and then be repaired.

If radiation is the problem, you want to use substances high in hydrogen - like water or hydrocarbons (plastic). Water and other fluids could be rapidly moved to problem areas - picture the space between the inner and outer hull being variable, like a ball rattling around inside another ball. The ultimate fuel/shielding material would probably be metallic hydrogen.

Magnetic shielding is also a possibility, with strong field either diverting or channeling both radiation and particles from certain vectors. A ramjet takes advantage of this by funneling the bad stuff in front of the ship into the engine and leaving a ring of crew area around the engine that is relatively unmolested. Even if this isn't your primary drive, it might still be worth the expense to have a scoop out front.

You can also build your ship for survivability, with fairly thin self-healing hulls that allow micro-impacts to go right through with a minimum amount of damage, and a relatively small core of important systems having the only heavy armor. This would be something of a statistics based approach - how likely and how often do you expect impacts.

Then we have forcefields (whatever those are). In the various Treks and Wars, force fields are effective but can be overwhelmed. They can be independent of the ships inertia or transmit impact inertia to the structure. In the famous Macross (Robotech) anime, they can't build a full force field, so they have three tiny ones that they move around the hull to intercept missiles.


That's all assuming that you have a delta v limit associated with your drive system. But if your drive uses some speculative principle, maybe mass isn't an issue. Maybe you can just hollow out an asteroid and power it up. But for the sake of some sort of limits, you might consider that such a drive can only move a certain volume, or has a slow response, or something else that feels like a compromise.

That's a lot of food for thought, and all of it was delicious!

I suppose if you have the Trek/Wars forcefields/deflectors/shields or even a Robotech version that could serve as an earlier prototype of that, it would make things very easy as that would mean the shields would do the majority of the work, so long as you've got the power. But if that fails and the hull is relatively weak, which certainly seems the case in a lot of Trek/Wars ships, then you're in trouble. Enter the USS Defiant with the ablative armour.

So it might be a case of having some sort of alloy called "Madeupium" that is thinner and stronger then most regular materials and can do whatever it's determined to need to do to keep the ship and crew safe, but that does feel a bit predictable in a way.

 

[DAgent]

Another very speculative type of shielding would be having a double hull with super heated plasma magnetically suspended inside. Micrometeorites would rapidly burn in the high temps; the plasma acting like an atmosphere on steroids.

Could that have a drawback if the outer hull was penetrated by any weapons like lasers or plasma or other energy based weapons?

 

[DAgent]

I would wonder about how to manufacture a solid, half meter thick hull. How would it be possible to join two thick blocks and not have a fairly fragile joint? How would one weld together two half meter surfaces? Another possibility would be to build the half meter thickness by overlaying multiple thinner sheets. In this case, I would be concerned with different rates of thermal expansion between the layers, which could cause layers to buckle and perhaps fracture. I'm not sure that the added thicknesses of metal would provide any structural advantage over alternate fillings such as foam or sprayed insulation.

The thing that has bothered me the most on spaceship construction is the inclusion of viewports. Clear materials would seem to be more fragile than the hull material being discussed. And how does one establish a seal between the hull and viewport that wouldn't be in danger of degradation over years, decades, or perhaps centuries? Does someone don a spacesuit and go out and caulk the windows every couple of years?

I'd assume if they went with the overlaid method, it would make it easier to replace damaged sections or even perform maintenance.

As for viewports, I think it depends on which method the writers come up with. Trek apparently uses transparent aluminium but they never go into detail about how it's installed and the actual windows on the Enterprise D don't really show off many clues there either. And those things look about 2 meters long in some cases!

I'm not sure if transparent metals are a thing in real life though.

 

[Venusian Broon]

I never would of thought of icing up the hull at all, but I do see where your coming from there, and I do like the image it gives me of an icicle like spaceship. But I'm more thinking along the lines of general overall purpose, something that could protect from attacks as well as radiation and so on. I can't see it provide much attack against energy weapons, unless it's exceptionally thick.

I'm also thinking it might not last long on a ship meant to study gas giants or solar activity, but could the same premise be used to ice up the space between an inner and outer hull to have a similar effect?

I wasn't really really thinking about actual combat. SF or otherwise, I was rather thinking about the problem of the high-energy radiation and stuff that will hit the ship whilst travelling (if one could actually power such a craft fast enough. ) Thus a possible solution for interstellar craft, within the realm of possibility.

As for other craft. sure they'd be designed differently. Do you need interstellar craft to go right next to a star? Perhaps have a large interstellar 'carrier' craft which hold a range of other craft inside? Like solar sails, space-to-ground transports, interplanetary exploration craft to check out those pesky gas giants or get close to stars?

With regards to combat well it depends what you've cooked up. If lasers in space were prevalent then you'd just mirror the outside of your craft and a lot of that energy just gets reflected away. But perhaps your idea of 'energy weapons' is different? (Don't say 'plasma' they'd be the easiest thing in the world to defend against - I'd expect magnetic and electric fields to be an integral part of future spacecraft 'force field' design in real life )

Anyway, I'd always have a high-velocity guided artificial mini-asteroid as a weapon. A good 1000 ton piece of shaped metal, say. Probably doesn't need to travel too fast to really mess up any spacecraft, no matter how thick the hull is. Not a lot you can do if you get hit by one.

The main issue I have with metal hulls is how do you go about trying to repair it? Sure there are metallic asteroids and planets out there, but then you'd have to become a refinery and a ship yard at the same time. I don't buy it. At least in the near future!

However, if you are 1000 years in the future with a waaay more advance tech that can solve such things...why worry about hull issues? The thing you should have as given is a powerful engine that can actually move a huge hunk of metal through space. Even Alastair Reynolds glosses over how his engines work for his lighthuggers

 

[DAgent]

I wasn't really really thinking about actual combat. SF or otherwise, I was rather thinking about the problem of the high-energy radiation and stuff that will hit the ship whilst travelling (if one could actually power such a craft fast enough. ) Thus a possible solution for interstellar craft, within the realm of possibility.

As for other craft. sure they'd be designed differently. Do you need interstellar craft to go right next to a star? Perhaps have a large interstellar 'carrier' craft which hold a range of other craft inside? Like solar sails, space-to-ground transports, interplanetary exploration craft to check out those pesky gas giants or get close to stars?

With regards to combat well it depends what you've cooked up. If lasers in space were prevalent then you'd just mirror the outside of your craft and a lot of that energy just gets reflected away. But perhaps your idea of 'energy weapons' is different? (Don't say 'plasma' they'd be the easiest thing in the world to defend against - I'd expect magnetic and electric fields to be an integral part of future spacecraft 'force field' design in real life )

Anyway, I'd always have a high-velocity guided artificial mini-asteroid as a weapon. A good 1000 ton piece of shaped metal, say. Probably doesn't need to travel too fast to really mess up any spacecraft, no matter how thick the hull is. Not a lot you can do if you get hit by one.

The main issue I have with metal hulls is how do you go about trying to repair it? Sure there are metallic asteroids and planets out there, but then you'd have to become a refinery and a ship yard at the same time. I don't buy it. At least in the near future!

However, if you are 1000 years in the future with a waaay more advance tech that can solve such things...why worry about hull issues? The thing you should have as given is a powerful engine that can actually move a huge hunk of metal through space. Even Alastair Reynolds glosses over how his engines work for his lighthuggers

Yeah, I'm suddenly seeing the captain asking the chief engineer a couple of questions about repairs to the engines, and the chief asking "Do you really want to know?" and the captains eyes crossing over after a couple of minutes of technobable!

 

[Swank]

Could that have a drawback if the outer hull was penetrated by any weapons like lasers or plasma or other energy based weapons?

Maybe. But if the plasma is being contained primarily by magnets it might not be a big deal.

I don't think lasers are a particular threat in space due to the distances and time lag with aiming. And they are fairly easy to reflect or ablate. Spray a mist of water into space and you are surrounded by reflective ice crystals.