My question is, how can, say, a spacecraft have self repairing armor? It works using three layers: Delicate computers and people inside, armor repair system surrounding that, and then the armor itself. When the armor is damaged, the repair system excretes new armor. It sort of like when you get a scratch, you grow new skin cells.

My question is, what would the material be, and how would it repair itself? Remember, this is just supposed be a dumb material, not nanites or advanced AI.

  • The material should be able to absorb significant energy and projectile fire before any of the inside gets damaged.
    • This also means it shouldn't allow any type of dangerous radiation to go through it can cook the insides.
    • It doesn't need to be invincible. Once it gets damaged enough, the repair system will get damaged, life support is knocked out, and everyone inside gets blasted. No way to stop this.
  • It does not need to repaired fast, but it should be fairly simple and flexible
  • I'm looking for answers based on current materials we know.

I'm thinking something foam like would work, but I'm not sure.

How do you build self-repairing armor.

  • 3
    $\begingroup$ Are you sure you want it to be dumb material? The things which repair themselves (such as skin) are decidedly not dumb. It took millions of years to make it as smart as it is. At the very least, are you looking for a super-smart repair system that excretes "dumb" armor, like we make hair or nails? $\endgroup$ – Cort Ammon - Reinstate Monica Aug 11 '15 at 4:08
  • 1
    $\begingroup$ There are materials today that do this - usually some mechanism that releases liquid/goo when damaged that hardens one released. $\endgroup$ – NPSF3000 Aug 11 '15 at 4:37
  • 1
    $\begingroup$ I suggest a mechanism (of course, it doesn't exist as we know it) similar to coral. Where the micro-organisms on the outside are stressed until those further in are able to reconstruct the structure; and finally, the more sensitive fish or whoever, are on the inside. Obviously, this will require a lot more thought than just "coral," so no answer from me yet. $\endgroup$ – Mikey Aug 11 '15 at 5:01
  • 1
    $\begingroup$ en.wikipedia.org/wiki/Self-healing_material Google and Wikipedia to the rescue. $\endgroup$ – Hackworth Aug 11 '15 at 5:53
  • 1
    $\begingroup$ If it can repair itself, how can it be "dumb"? On the surface it sounds like nanotechnology (natural ("life") or engineered) yet you disallow that. $\endgroup$ – JDługosz Aug 11 '15 at 6:29


Dead simple to replace - just apply and let it freeze. You can even go grab more from a nearby asteroid or comet. It's reflective, which is useful against radiation and lasers. And when it gets evaporated it turns into steam, and that steam will - in turn - deflect and refract further. And it does a great job against radiation.

It's not as useful against projectiles, but it provides some protection, and you can make it a lot thicker. Volume isn't super important on a space ship, mass is, and ice is something like 5-6 times lighter than most metals.

  • $\begingroup$ How do you add ice from the inside? $\endgroup$ – PyRulez Aug 11 '15 at 19:26
  • $\begingroup$ @PyRulez: Probably the most consistent would be to have repair bots that scramble over the outside and apply more water/ice to damaged areas. You could apply from inside, but that would be tricky if the ice armor is damaged but not burned all the way through. $\endgroup$ – Dan Smolinske Aug 11 '15 at 19:29
  • $\begingroup$ Could have some type of "shedding". When the liquid water first freezes, it is attached to the middle layer by a solid mechanism (clasps, retractive hooks, etc), which the ship can "release" and then regrow a completely new ice shield. $\endgroup$ – DoubleDouble Aug 11 '15 at 19:39
  • $\begingroup$ What if you want to land, surely passing through a planets atmosphere will melt the ice. $\endgroup$ – Bellerophon Feb 6 '16 at 19:43
  • $\begingroup$ sure it will bellerophon, but in the meantime it's environmentally friendly ablative heat shielding. the steam won't stay steam for long, just setting course to drift slowly through the particulate cloud could recover a lot of the sublimated material. as to mass:volume ratios, going out of your way to pick up water to use as armor is going to offset almost any gain you might make by carrying less mass unless mass doesn't much matter in which case the whole line of questioning is moot. $\endgroup$ – Giu Piete Dec 4 '18 at 5:58

Ignoring a few issues with self-repairing armor in space like:

  1. Any entrance/exit/doorways
  2. windows/viewing opening
  3. Space being a vacuum
  4. The type/amount/duration of damage being inflicted

The simplest solution:

Slime sealant

Similar to what is used in tires to fix holes. When there are no holes it sits on the inside of the armor. When there is a hole the slime will get sucked out (by the vacuum of space) and harden (chemically?). This will only be a temporary solution though and won't last forever.


With a smart system, and an armor system made of up equally sized segmented parts, when the exterior receives damage then said segment(s) could be discarded and replaced by new piece(s) until the new pieces run out (from storage/armor repair layer). You would need an additional minor armor/layer of protection to protect against radiation.

  • $\begingroup$ (chemically?) freezing is a reaction that can cause compounded reactions. $\endgroup$ – Giu Piete Dec 4 '18 at 5:46

The actual material is dumb. The repair system is a little smart

bone is a composite of protein and dead mineral. Cells cruise along and re-pave the minerals like road maintenance: one kind chews up the old surface and anothe type paves down a new layer.

nails and beaks keratin is extruded to protect our finger tips and a bird's beak. It slowly renews.

shells and tests Same idea. Material is laid down by living cells.

Look over examples from nature and find something that can be domesticated by individual creatures that are rather flat but covered with protective plates. They can be trained to grow in specific shapes like bonsai, to form a section of armor. After use, the sections are stored in an aquarium.


In spaceships, every gram counts!

Putting this another way, no ship - not even a space ship dedicated to combat - could afford to carry mass whose only purpose was as armor against other weapons.

However, a clever spacecraft designer could indeed layer a ship in such a way to protect the most valuable parts of the ship (like the crew) with less valuable parts of the ship.

Some items on any atomic power space craft that it would have to carry and could provide protection against weapons fire are:

As Dan pointed out, ice / water could fill 4 of those 5 roles (propellant, water storage, shadow shield, & storm shelter).


Is just what it says. This is the mass ejected to generate thrust. Depending upon the type of engine use, you may also need a power plant and fuel for that plant or not. Propellant is likely to take 50% or more of the mass of your ship.

Water storage

Water is a terribly useful resource in space, it can be:

  1. Purified and drunk
  2. Split and breathed
  3. Split and used as rocket fuel & propellant
  4. Refined as used as your fusion plant fuel
  5. Put in your storm shelter / shadow shield to protect against harmful radiation, especially neutron (reactor) and proton (solar wind) radiation.
  6. Found anywhere in the solar system outside of the Frost Line
  7. Used as hydroponic tankage to grow food

So the reality is during combat the crew would evacuate as much as the ship as they could (to preserve atmosphere), move to the "storm shelter" as the best protected portion of the ship, and conduct combat operations from there. The designers might wrap part of the storm shelter with the ship's structure as added protection.

As depperm pointed out such tankage would include automatic sealants even if it wasn't a combat ship since without it a single micrometeor could drain your whole ship of propellant - which wouldn't be very good.

In the case of a combat ship, using ice instead of water provides several benefits. 1. a holed tank doesn't drain all your propellant 2. it has greater heat absorbing capacity 3. it is far more reflective and can better reflect laser light



Millions and millions of nanites (microscopic robots) are on board that serve as they ship's cleaning and maintenance crew. They are capable of crawling all over the ship, inside and out. They are programmed to clean, repair wires and simple circuits, even repair microscopic scratches in the hull.

Naturally they are programmed to leave people and cargo alone.

  • 2
    $\begingroup$ That was my first inclination, however, the OP said no nanites specifically. $\endgroup$ – bowlturner Aug 12 '15 at 17:12

To build on some of the ideas mentioned by others, a process that simulates life could work.

The idea I have, instead of armor replaced only when the armor is damaged, but a constant repair, growth of new armor. If the armor was made up of many small overlapping "scales" made up of a polymer, keratin, CaCO4 or some super material, the sub-armor repair mechanisms grow these scales slowly over time. As these plates grow big, beginning to stick out beyond the armor limits, it becomes brittle by various mechanisms, such as gamma embrittlement, micro-meteors or a programmed age, they begin to erode or chip away to maintain a proper size. If one plate it totally blown off, very little of the substructure would be exposed as the armor is overlapped like scales.

So over time, the armor grows and replaces itself by itself, with little to no external input. Just need to provide a constant supply of raw material to replace itself. Now after combat, you may need to go and hid for a little while as this armor will take time to regrow.


You can make the armor modular, and have a facility in the spaceship make the modules. Whenever the armor gets damaged, the armor repair layer orders new modules and installs them. This can work down to the molecular level with nano machines using a system like this.


A living ship.

We have a few sci-fi examples of this. Two that immediately come to mind are Farscape's ship (And her child), where the ship is a living creature that is naturally born, then enslaved. And Stargate Atlantis Wraith ships, which are organic ships that grow based on how much power they have.

So if you go the first way, you get to have some in built ethical problems for your characters to wrangle with. The second gives you the ability to not only grow armor, but grow components, weapons, etc. as needed.

An obvious third choice in the Tardis, but I don't suggest going with that one. It gets too confusing, then your fans pick your story apart.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.