The propellent is contained within the can so I don't know if the lack of gravity would have that much effect. Or would it?
What about temperature? Could the can be wrapped in an insulator to make sure the paint doesn't freeze?
Would there need to be a funnel or cone leading from the top of the can to the surface being painted that contained a more normal environment?
Future tech can be used to make this viable. I'm just having trouble figuring out how the paint would actually act in open space.
Your thoughts are appreciated.
The composition of the paint will be a problem. Most paints dry by evaporation. that does not work well without gravity if I understand right. It will diffuse out of the paint but will linger as a cloud around the ship.
One idea is to use a hot melt system where a sheet is laid over the panel or panels, and then a heat source is applied to the sheet, melting it to the surface.
Aother method would be applying sheets that are the paint. They "glue" on as the surface coating.
Something that could be done is to apply a skin, a baggy, over the surface, gluing it along the edges. The area is then "flooded" with color under pressure, whther filling it full of liquid or filling it with a gas or spray. It is kept on until the surface coating density is achieved, then the rest of the material is drawn out. Pressure might be applied at one end and a vaccume is applied at the other and it draws out the remains so the skin can be removed.
Don't forget the possiblitiy that a panal might be removed, painted inside, then reapplied. there might be replacement panels so they simply are swapped at the moment so the interior of the ship is not exposed for very long.
Ah, I just thought of something as I was about to sign out. One can use rollers or sponges to paint the surface. The paint does not transfer without physical contact. Usually thick paint does not splatter and physical application is necessary, so one can avoid the worst of flying splatters.
Of course, you asked about spray painting.
Applying a pressurized spray booth on the surface of the ship and the operator sprays the suface with a good filtering system to remove excess paint spray might work.
Of course, if you want the literal spray painting the ship, the electrostatic method of painting would work best.
If anything here comes close to sounding plausible, great. If they do not come close, I am sure we can come up with some other suggestions.
Issues:
Powder coat paints are actually dry powder enamels applied by electrostatic deposition. But they need controlled, relatively high heat curing in order to set in place. Most plausible painting method in a vacuum.
Three practical reasons for painting, preservation of a substrate, labeling, art or vandalism. Painting a vessel's surface that is exposed to vacuum seems highly impractical and unnecessary. Quick, convenient, and easy labeling of small or large areas in a vacuum would be practically impossible by most conventional painting methods. For art or vandalism? Seems to me that would be equally if not more impractical.
I can imagine one scenario where future tech might solve most of the issues. Ultraviolet light protection coated nano-miniature paint balls shot onto a surface that burst on contact with a substrate and cure instantly in vacuum due to ultraviolet light exposure.
[This message has been edited by extrinsic (edited November 02, 2009).]
I will have to come up with some gadget that addresses all of these issues.
Thank you very much for your insights.
Electrostatic painting can work quite well for many substances. One thought I had is that photocopier ink is made up of the ink itself, a magnetic material that is attracted by electrostatic charges, and a plastic that is melted so the ink is bonded to the surface.
If the spray painting is done in several stages, they could spray the "paint" onto the surface. then pass over it with a heater to melt it to the surface.
Another method is to use an epoxy like material where it is combined in the nozzle when it is sprayed and the chemical reaction happens moments later, usually once it was attracted to the ship surface.
If it is a chemical process that requires the surface of the ship (the old finish as a possibility) to act like a catalyst to cause the reaction to set up. The setup finish would work great as the electrostatic spray causes the finish to attach to the surface of the ship and only that which makes contact freezes into the paint. The rest floats away harmlessly, or to slowly drift onto another part of the ship.
If this is a ship yard, one could have an entire system to clear the space of the paint dust, dragging meshes or plates through the area to gather up the dust.
The painters might need to torch the surface. The ship plating would have to be able to take great heat so applying heat to the paint to weld it to the surface should not be a problem.
Of course, welding the paint (metal compounds) would be a way to go where the paint becomes part of the substructure, building up another layer of protection. Again, electrostatic attraction would work.
Open space would give the same quality as painting a car outside. Dust, moisture, gas all effecting quality. You could have lots of fun with ionization and static charge issues in open space.
Inside a space dock or a space vehicle the environment can be controlled, temperature, static charge, solar winds not blowing micro particles of paint over things.
Take the item inside to paint, you get air quality issues for the vehicle. The attempt to buff out a scratch on your starship could killing off the entire crew.
If it is on a spinning space station, or if you have some form of artificial gravity, the pressurized spinning bay would be like painting in gravity.
One would simply filter the fumes out of the air. Of course, most everybody would be in space suits anyway, but we are used to working in a pressurized gravity environment so painting in dry dock would be a solution.
When done, pump the air out of the bay and let the ship out, clean and painted under exact controlled conditions.