Do We Really Need Paint To Cover Vehicles?

[Spacescifi]

Paint seems like a cheap alternative to 'fixing' vehicle damage.

Have a scratch? Paint it over. No one is the wiser. Metal look all rusted? Paint it!

 

So what alternatives do we have for paint? Even if it is not cheaper in cost I want to know?

 

Bonus Question: Painted OR unpainted spacecraft?

I think unpainted wins generally assuming modern technology is used. Lighter in weight and paint would probably ablate during reentry anyway on an SSTO. There goes the nice paint job.

What say you to all this?

Edited December 28, 2019 by Spacescifi

[kerbiloid]

A proper lighting makes your craft look fine even without painting.

Spoiler

 

Quote

Painted OR unpainted spacecraft?

Painted metallic to look unpainted.

P.S.
If get a contract with Coca-Cola, one question less.

Edited December 28, 2019 by kerbiloid

[AngrybobH]

4 hours ago, Spacescifi said:

Metal look all rusted? Paint it!

You don't paint rust. You remove rust then paint it to keep it from corroding, which is the point of paint to begin with. Turns out you can also make paint in just about any color you want so your protective coating becomes a fun way personalize your whatever it is you are painting.

4 hours ago, Spacescifi said:

So what alternatives do we have for paint?

Paint is a fairly broad term and anything you apply via brushing, spraying, dipping, and possibly electroplating you could call paint. This would cover plasti-dip, rhino lining, galvanizing, anodizing, and on and on. There are only a couple of paint alternatives I can think of, keep your device/machine/spacecraft away from things that will damage it, or make it out of a material that doesn't become damaged in its' operating and/or storage environment.

5 hours ago, Spacescifi said:

Bonus Question: Painted OR unpainted spacecraft?

Depends on the material it is made of and its' environment, see above.

[Barzon]

11 hours ago, kerbiloid said:

A proper lighting makes your craft look fine even without painting.

  Hide contents

 

The blue is paint.

[kerbiloid]

1 minute ago, Barzon said:

The blue is paint.

It works even without the blue. Even with stone walls.

[DDE]

16 hours ago, Spacescifi said:

I think unpainted wins generally assuming modern technology is used. Lighter in weight and paint would probably ablate during reentry anyway on an SSTO. There goes the nice paint job.

Paint protects against corrosion, works as camouflage, and somewhat helps with thermal control. When these factors aren't involved, you don't see much paint:

Or, a closer example, the External Tank used to be painted:

[benzman]

All spacecraft should be totally unpainted. Flakes of paint travelling at orbital speeds can be as dangerous as bullets.

 

[kerbiloid]

At least Soviet/Russian ones are usually coated in shaped insulation blankets, so they are painted in heraldic colors.

(Usually, green.)

Spoiler

 

Edited December 28, 2019 by kerbiloid

[Guest]

That Soyuz in the picture is black.  They used to be a rather obnoxious shade of green, though. This isn't really paint, though. Thermal blankets can be colored however you want without sacrificing mass.

Paint is useful for when your LV spends a lot of time exposed to the atmosphere. Most of them do, sitting on the launchpad or in storage. Of course, if you already have something covering the rocket, like insulation, you don't need an extra layer of paint. In the old days, it was also useful for tracking the rocket's rotation (hence why all those black and white patterns on most US rockets and some Soviet ones).

[Incarnation of Chaos]

Iv'e always wondered about using small-ish sacrificial anodes for corrosion resistance on vehicles like Cars,Buses,Trains and Planes; they're rather common on ships so iv'e always wondered especially why on planes they aren't used (The mass of paint can easily affect performance!). Though i figure it has something to do with air being a crap conductor, but you could always just run current thru the hull to form the circuit.

But for an SSTO specifically even if you did decide to go with anodes there's another reason you'd likely want paint; anything that has a reasonable chance of SSTO'ng from earth is using Hydrogen/Oxygen fuel. Keeping that from boiling off is not going to happen on the thin mass margins you'd have, so the best alternative would be a nice coat of white paint. As a bonus; one of the more common pigments for white is Titanium Dioxide which is incredibly heat resistant. So you'd still need a TPS of some sort, but a properly applied paintjob wouldn't likely wear too much from reentry.

[Guest]

Actually, LH2 requires actual insulation, which pretty much frees you from having to use paint for anything. LOX, meanwhile, makes its own insulation. Water vapor condenses on the tank, and ice is a surprisingly good insulator (you can grab an iced-over LN2 line with your hand, and why igloos work so well). Atlas rockets have kept LOX in aluminum balloons for a long time.

[Incarnation of Chaos]

11 hours ago, Dragon01 said:

Actually, LH2 requires actual insulation, which pretty much frees you from having to use paint for anything. LOX, meanwhile, makes its own insulation. Water vapor condenses on the tank, and ice is a surprisingly good insulator (you can grab an iced-over LN2 line with your hand, and why igloos work so well). Atlas rockets have kept LOX in aluminum balloons for a long time.

Well i wasn't thinking the tanks wouldn't be insulated; rather the white paint would increase the effectiveness of the insulation that's there. And tbh it's really only a factor for the LH2, as you point out LOX isn't as hard to deal with.

[kerbiloid]

1 hour ago, Incarnation of Chaos said:

the white paint would increase the effectiveness of the insulation that's there.

Not necessary. In infrared both can look black.

The Shuttle's one was dark orange.

Edited December 30, 2019 by kerbiloid

[Incarnation of Chaos]

11 hours ago, kerbiloid said:

Not necessary. In infrared both can look black.

The Shuttle's one was dark orange.

But the sun doesn't just emit Infrared, and absorbing those other wavelengths will contribute to heating. Also on the shuttle the ET was painted white until they realized it didn't contribute much but extra mass; since the shuttle was burning the fuel the entire way up and boiloff was negligable. For an SSTO this would be different; unless it's strictly a LEO craft that never fuels while in orbit.

It would come down however, to the specific craft. Something that's just taking passengers from the ground to a large station wouldn't likely see any benefits from it; while something that has to drift to Mars/Outer Planets and be able to perform a insertion burn would be a different case.

[kerbiloid]

3 hours ago, Incarnation of Chaos said:

But the sun doesn't just emit Infrared, and absorbing those other wavelengths will contribute to heating. Also on the shuttle the ET was painted white until they realized it didn't contribute much but extra mass; since the shuttle was burning the fuel the entire way up and boiloff was negligable. For an SSTO this would be different; unless it's strictly a LEO craft that never fuels while in orbit.

There were black Gemini, white Gemini, white-and-black Gemini, metallic Apollo, green Soyuz, white Soyuz, gray Soyuz, green TKS, green Salyut, idk-how-to-describe Skylab, white Dragon, black-and-white Space Shuttle, white (then white-and-brown) Mir, white ISS, etc.

As Gemini, Soyuz, and (TKS / Salyut / Mir / Mir-derived ISS modules) are absolutely same ships but everyone in various colors, so, I guess, the painting doesn't bring much to the heat balance.

Also, afaik, in IR they still look black.

Edited December 31, 2019 by kerbiloid

[Incarnation of Chaos]

3 minutes ago, kerbiloid said:

There were black Gemini, white Gemini, white-and-black Gemini, metallic Apollo, green Soyuz, white Soyuz, gray Soyuz, green TKS, green Salyut, idk-how-to-describe Skylab, white Dragon, black-and-white Space Shuttle, white (then white-and-brown) Mir, white ISS, etc.

So, I guess, the painting doesn't bring much to the heat balance.

Also, afaik, in IR they still look black.

Tbh now you got me wondering if there's any academic studies on this; it would be nice to have some hard numbers on this. 

[kerbiloid]

Just now, Incarnation of Chaos said:

Tbh now you got me wondering if there's any academic studies on this; it would be nice to have some hard numbers on this. 

I also got wondered, so had asked here in the random questions thread, but looks like nobody knows.

(updated the list)

[Incarnation of Chaos]

1 minute ago, kerbiloid said:

I also got wondered, so had asked here in the random questions thread, but looks like nobody knows.

(updated the list)

I'll poke around some of my own resources; see if I can find anything. No promises though.

[Nuke]

i know that burt rutan of scaled composites prefers white which supposedly improves the life of composite structures (presumably through reduced heating). you see it on most of their planes/space craft. not sure what interview i heard that but its probably on the intertubes somewhere.

Edited December 31, 2019 by Nuke

[linuxgurugamer]

1 hour ago, Nuke said:

i know that burt rutan of scaled composites prefers white which supposedly improves the life of composite structures (presumably through reduced heating). you see it on most of their planes/space craft. not sure what interview i heard that but its probably on the intertubes somewhere.

Also protects against ultraviolet radiation

[mikegarrison]

On 12/29/2019 at 4:40 PM, Dragon01 said:

Actually, LH2 requires actual insulation, which pretty much frees you from having to use paint for anything. LOX, meanwhile, makes its own insulation. Water vapor condenses on the tank, and ice is a surprisingly good insulator (you can grab an iced-over LN2 line with your hand, and why igloos work so well). Atlas rockets have kept LOX in aluminum balloons for a long time.

Igloos are not made of ice. Igloos are made of snow. Air is a very good insulator as long as it is not convecting, and snow is mostly air.

[Guest]

What do you think snow is made of?  Air certainly helps, but it wouldn't work at all if frozen H2O was any good at conducting heat. Snow is also used because it has the advantage of being fairly easy to come by and to shape, as opposed to solid ice.

[mikegarrison]

1 hour ago, Dragon01 said:

What do you think snow is made of?  Air certainly helps, but it wouldn't work at all if frozen H2O was any good at conducting heat. Snow is also used because it has the advantage of being fairly easy to come by and to shape, as opposed to solid ice.

It's the air in the snow that provides the insulation. The ice structure provides the strength and traps the air, preventing it from convecting. It's the same reason fiberglass blankets, foam, and many other insulative materials are insulative.

 

[Guest]

Which doesn't change the fact ice, itself, is a good insulator. Solid ice has thermal conductivity on order of rock (slightly higher than of limestone), which is a pretty good at keeping heat out. Yeah, air pockets make for a much better (and easier to handle) insulator, but to give them sole credit for snow's insulating properties is a mistake. It's not the case with igloos specifically, but people have made livable buildings out of solid ice. This applies to other insulating materials as well, fiberglass wouldn't be nearly as great an insulator if glass itself wasn't already a really good one.

[kerbiloid]

The snow is ice foam, not solid ice.