# If a spacecraft's double hull filled with water is hit by a micrometeorite, could the water freezing or surface tension stop the leak?

I'm thinking about the possibilities of water storage also serving radiation shielding for long space journeys (months to years). Assume within the solar system but outside of upper earth orbit. Consider a spacecraft with two outer hulls, with a water layer between them, partitioned into sections. Similar to double hulled oil tanker ships:

If a low pressure, thin-walled (aluminum or steel?) tank of water surrounding the hull of a spacecraft is hit by a micrometeorite, could the water freezing seal the hole? Or would the thermal transfer in near vacuum be too slow?

If the water tank pressure is low enough, would surface tension slow the water escaping enough to aid the freezing? Before the water becomes a bubble outside of the ship, or spreading all over the exterior.

Because of all this contact with the ship, hopefully I'm not wrong in assuming the water would be liquid phase in the tank.

The tank breach-hole would be fairly small but not insignificant to water. The most common micrometeorites near Earth mostly measure no more than a millimeter across and weigh less than a gram (or 0.04 inches and 0.04 ounces).

• Note that a millimeter-scale micrometeorite may make a centimeter-scale hole when it impacts at multiple km/s relative velocity. Apr 17, 2023 at 21:18
• Would water be able to freeze? My impression was that if you introduced liquid water to vacuum it would boil first at any reasonable temperature. Apr 17, 2023 at 22:22
• It is unlikely that in the spacecraft design you have suggested, they will try to keep water in a liquid state. And ice between walls will not escape. In case of a hole caused by micrometeorite - some simple mechanism for re-heating and re-freesing can close the hole. Apr 17, 2023 at 22:42
• @RussellBorogove On a thin aluminum plate, a millimeter-class meteoroid will make a hole maybe 3 mm across. The larger the diameter of the particle relative to the plate, the smaller the ratio of the hole diameter to the particle diameter. A bigger concern would be that a water-filled hull would provide a medium to transfer the shock wave of impact to the rear wall and create quite a bit more damage than having nothing at all in there. If you go down that road, you would almost certainly want a whipple bumper out front so your water hull is the rear wall of the shielding system. Apr 18, 2023 at 16:00
• @Cadence The water won't be able to do anything but boil and freeze. Below 611.7 Pa, pure water can only exist as a solid or gas. Apr 18, 2023 at 16:38

When you introduce a bunch of water into space, it’s going to boil first then those small vapor particles will freeze into tiny ice crystals. This is because your only method of heat transfer in space is radiation, which is quite slow compared to conduction or convection.

So the question is going to be whether these tiny ice crystals will stick together enough to close up the hole, but I wouldn’t expect that since the boiling water will keep creating new tiny ice crystals that will push the others out of the hole.

Here’s a good article on what happens to water in a vacuum with some videos linked: https://medium.com/starts-with-a-bang/does-water-freeze-or-boil-in-space-7889856d7f36