Whether exhaust from a solid rocket engine, or something released by spaceships in flight (like aerobatic smoke in the atmosphere), could extended trails behind a ship be created that would not dissipate in the vacuum of space?

Could a trail be formed that a person close enough to see the ship with the naked eye would be able to see the trail?


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    $\begingroup$ The only thing I can think of would be re-ionization of the ion exhaust of an ion engine with free electrons from the solar wind. But since the ion trail is released at relativistic speeds, and the desnsity of free electrons is very low, you might not be able to see it except with powerful sensors. $\endgroup$ – Klaus Æ. Mogensen May 14 '19 at 13:52
  • $\begingroup$ Mandatory Robotech/Macross gif... But this is possible only under the rule of cool $\endgroup$ – McTroopers May 14 '19 at 15:57
  • $\begingroup$ could you add some info on the proximity to a star or similar light source, the relative velocity of trailer and observer, the distance of observer to trail and the length/time of the trail? $\endgroup$ – bukwyrm May 16 '19 at 15:01
  • $\begingroup$ @bukwyrm At Earth-Moon L1 or L2. Ships about the size of the space shuttle, or maybe smaller, performing maneuvers close enough to a space station for observers on the station to see. I don't have an idea of length/time of the trail. $\endgroup$ – Bob516 May 16 '19 at 15:24

Using fumed silica. It is stable in vacuum, after crystallizing it won't spread out and it requires little source material to create large volume agglomerates.

  • $\begingroup$ Never heard of it. That is fascinating. Would there be any way colors could be added to it, in a stable form? $\endgroup$ – Bob516 May 14 '19 at 14:23
  • $\begingroup$ Sure, for example enamel coating on cooking gear contains silica glass as main ingredient, with full range of colors using various minerals. $\endgroup$ – Juraj May 14 '19 at 14:48
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    $\begingroup$ Conservation of momentum will cause the particulates in the plume to continue moving along their original trajectory when emitted by the "smoke generator." (SG) If the SG is the craft's engines, then the motion will be in the opposite direction of motion and at a much higher velocity than the crafts. And if the SG is a smoke bomb then its velocity will also be opposite the direction of motion, but at a lower velocity. In either case, the plume is likely to smear in strange ways before it diffuses. $\endgroup$ – EDL May 14 '19 at 16:01
  • $\begingroup$ @EDL That's good, that way it will look different from air shows, and creative choreographs will find new and interesting ways to use it. $\endgroup$ – Eth May 14 '19 at 16:12
  • $\begingroup$ @EDL could be the smoke generator is separate from the main engines and creates smoke that is frame-matched with the spectators. Having the smoke plume-ting at very high speed into the atmosphere wouldn't leave as much of a show. $\endgroup$ – John Dvorak May 14 '19 at 16:23


comet lovejoy http://spaceflight.nasa.gov/gallery/images/station/crew-30/html/iss030e015472.html

Depicted: comet Lovejoy shakes its tail as seen from Earth orbit.

If a comet can leave a sweet trail so can you. Especially since the comet is just shedding stuff but you are actively blasting stuff out your rear.

side note: I wonder why in this image the atmosphere has those colors in that order?

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    $\begingroup$ for those interested I asked the atmospheric colors question on the space exploration stack: space.stackexchange.com/questions/36141/… $\endgroup$ – Willk May 14 '19 at 21:32
  • $\begingroup$ The material the comet is shedding is already quite cold though, no? Exhaust makes me think we are talking about a potentially heated gas, which should dissipate essentially instantly in a vacuum. Also, comets are quite large (Haley's Comet's nucleus is 15 × 8 × 8 km) which I would imagine makes for a more visible tail. I'm speculating, though - IANAAP (I Am Not An Astrophysicist). $\endgroup$ – Alexander Nied May 15 '19 at 3:46
  • $\begingroup$ This is spectacular! Our of curiosity, is there any way to relate the volume of material ejected by the comet to engine exhaust? I'd be fascinated to know what it would take to duplicate this. $\endgroup$ – JBH May 16 '19 at 3:04
  • $\begingroup$ @JBH - I wonder what use of maneuvering thrusters in space produces as regards visible exhaust? Most rocket fuels make some water, which might condense. I will google around... $\endgroup$ – Willk May 16 '19 at 11:11

You can't see this spaceship, but you can for sure see its trails!

Norway spiral

[The Norway spiral]

That's not a timelapse - that's a defective Russian missile with uncontrolled roll, venting gases that are being caught by the sun.

These trails are above the atmosphere, which is why they last so long: they do not dissipate in the wind, but rather just continue on in the same direction they were expelled, with nothing to stop them.

Trails in space will last a LOT longer than in the atmosphere.


As long as the exhaust from the rocket engine can create crystals in the cold of space, those crystals, before sublimating, will scatter light and become visible to a sufficiently close observer.

One could add on purpose some substance in the plume so that it could vaporize and create suitable crystals.

Anyway, as you see also in the image you attached to your question, the trail won't be permanent: it would sooner or later diffuse and disappear.

  • $\begingroup$ Yes, I should have made that clear that I know a trail would diffuse. I was just hoping it would not diffuse so quickly it could not be seen as a trail. $\endgroup$ – Bob516 May 14 '19 at 15:43

One of my favorite movie quotes comes from The Hunt for Red October.

"Can you launch an ICBM horizontally?"

"Sure, why would you want to?"

You didn't tell us anything about your motor, but let's assume a reaction engine of some sort mixing oxygen with fuel to get a resounding Bang! I kinda suspect it needs to be non-nuclear as a nuclear engine would have the tendency to, well, atomize anything you might use to create your smoke trail.

Therefore, it's a trivial matter to introduce an additive to color the smoke. Technically, any additive used today could be used with your rocket so long as enough of it is used. Rockets tend to have really, really, really big engines.[Citation Needed]

But there are some problems...

  • In an atmosphere, there's something to kinda hold all the smoke together. The exhaust pressure dissipates and eventually equals the atmospheric pressure, after which the smoke moves with the wind. In space, this doesn't happen. The velocity of the exhaust (inevitably greater than the velocity of the rocket) forces the smoke to keep on truckin', and that usually in a lot of directions. I therefore expect the cloud to dissipate very quickly, necessitating an unholy amount of additive.

  • Unless you have spectators with really powerful flashlights (obligatory XKCD), the smoke could only practically be seen from the sun-side.1 So I question what the purpose of this exercise is? As smoke moves off the spherical plane defined by sunlight, it's efficiency drops. In other words, it has much less effect than it would inside an atmosphere.

  • In the words of Douglas Adams, "Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space." The distance between spectators and jet planes is trivially insignificant compared to space, so unless you're doing this for someone outside a space station in a very slow-moving rocket... yeah, another frame challenge.

So, I believe it can be done (emitting smoke in space), even using the same materials used by Jet Planes today. But I question whether or not it would be worth it.

1Light scattered through the smoke might allow it to be seen somewhat from the "dark" side, but considering you're looking into the unfiltered glare of a star, it might still be hard to see.


This is what a daytime rocket launch looks like from orbit:

a thin wiggly line of smoke rises up from the earth into space

Any time that a big rocket engine is firing, while the rocket is not in the shadow of the planet, there will be a visible trail.

(Low power thrusters like ion engines or cold gas thrusters will be less obvious. And many real life spacecraft coast for long periods of time with their engines off after they reach orbit or escape velocity)

  • $\begingroup$ I didn't know the trail would not diffuse quickly. Thanks. Where is this photograph from? $\endgroup$ – Bob516 May 15 '19 at 1:44
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    $\begingroup$ The photograph was taken from the ISS, late last year, during a Soyuz launch. I think within the first few minutes of the launch. $\endgroup$ – Robyn May 15 '19 at 1:49
  • $\begingroup$ It is an amazing photograph. $\endgroup$ – Bob516 May 15 '19 at 1:54
  • $\begingroup$ Super cool image! Why isn't it a straight line, given there isn't any wind to disturb it. Is this from thrust vectoring? $\endgroup$ – Dewi Morgan May 17 '19 at 15:17

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