Soyuz rocket intermittent contrail

Trailspotter

Senior Member.
While watching the BBC live broadcast of the first UK astronaut heading for the International Space Station this morning (11 AM GMT),


I noted a contrail that started forming behind the Soyuz rocket at about one minute after the lift-off and stopped about ten second later:
Screen Shot 2015-12-15 at 12.06.41.png
Screen Shot 2015-12-15 at 12.07.54.png

This suggests that rocket engines also require favourable temperature and relative humidity conditions for contrail formation. The sky above the Baikonur Cosmodrome was clear at the time, but a 100% RH was forecasted at 250hPa:
Screen Shot 2015-12-15 at 12.39.29.png

Presumably, the contrail was formed at the time when the rocket travelled through this humid (and cold) layer. The rocket's altitude at these times must be known exactly, but I haven't found these data yet to verify this suggestion.

Update:
A simulated Soyuz TMA Launch Multi-view with MFD & PAO commentary (Orbiter 2010) video suggests the altitudes of 11.36 km and 16.29 km for the flight times 60 sec and 70 sec, respectively. These roughly correspond to the lower and upper boundaries of tropopause, in which the ambient air is the coolest and its temperature remains fairly constant in this altitude range.

Curiously, the above simulation shows a contrail forming at 55 second mark, suggesting that this may be a recurrent feature. Indeed, watching the multitude of youtube videos of previous launches of the same (Soyuz-FG) rocket confirmed that an intermittent contrail commonly occurs between the 60 sec and 70 sec marks, but the times of its appearance and duration vary. The contrail in the beginning of this post appears to be the earliest and the longest amongst those I've checked so far.

This observation suggests that the ambient air lowest temperature in tropopause alone may be sufficient for the formation of this contrail, and that higher ambient humidity may increase the altitude range for its formation.

However, there is one additional factor that may be even more important for the contrail formation in that particular time interval. At 70 sec mark, the Soyuz rocket passes through the maximum dynamic pressure (the point at which the airframe undergoes maximum mechanical stress). It is the most likely that the rocket engines are programmed to reduce the thrust shortly before reaching this point. This would result in slightly cooler exhaust and therefore more favourable conditions for its water vapour condensation upon mixing with ambient air.

 
Last edited:

Trailblazer

Moderator
Staff member
Funny you posted this - I noticed exactly the same thing! I was also wondering what altitude this corresponded to.
 

Trailspotter

Senior Member.
60 seconds corresponds to about 10km or so. Hard to read but that looks about right.
Thank you for the info. Yes, this was my estimate from visuals and simple math. The ascent to 10 km in 60 seconds would produce the g-force of ~1.5 g that looks about right. But I thought about availability of the actual telemetry data.
 
Last edited:

Mick West

Administrator
Staff member
Soyuz rockets are liquid fueled, and burn liquid oxygen and the hydrocarbon mixture RP-1 (similar to Kerosene, or jet fuel). So the rocket exhaust is very similar to jet engine exhaust, except there's a lot more of it. The contrail however is sometimes described as a "smoke" trail, when it's actually a contrail.

Here's an older (Nov 7, 2013) two minute exposure photo of a Soyuz launch. The bright line is just from the long exposure, but then you can see the contrail starting higher up. It's blown away from the actual path of the rocket.

Source: http://www.nasa.gov/content/arcing-towards-orbit
 

Trailspotter

Senior Member.
Soyuz rockets are liquid fueled, and burn liquid oxygen and the hydrocarbon mixture RP-1 (similar to Kerosene, or jet fuel). So the rocket exhaust is very similar to jet engine exhaust, except there's a lot more of it. The contrail however is sometimes described as a "smoke" trail, when it's actually a contrail.

Here's an older (Nov 7, 2013) two minute exposure photo of a Soyuz launch. The bright line is just from the long exposure, but then you can see the contrail starting higher up. It's blown away from the actual path of the rocket.

Source: http://www.nasa.gov/content/arcing-towards-orbit
This is a great photo, but I do not think that the trail starting higher up is a condensation trail. At the two minute mark (near the buster separation time) the rocket's altitude is 28 miles. It could be some stratospheric phenomenon. In the OP video, a similar (?) trail is formed near the end of the first stage (from 2:10). it corresponds to the two minutes of flight. A video of this flight Soyuz FG - TMA-11M launch - November 7, 2013 shows a similar contrail that started and stopped at about the same times as the OP one. It occurred soon after the rocket passed the highest point of its apparent trajectory, as in the photo. Perhaps, the two-minute exposure of this photo started about 40 seconds before the liftoff.
 
Last edited:

Arbitrary

New Member
You're thinking of the trail seen around booster separation - looks faintly grey below?



I'm not sure what it is, but I might have an idea based on other videos I've watched of launches. For example, from SpaceX's CRS-6 video:



Since this offers two views alongside each other, I'd guess it is the blacker material visible on the onboard video, in which case it might be unburnt fuel used as coolant around the nozzle. Admittedly I'm not an expert but it seems plausible. Possibly like the dark gas below the nozzle before the bright part, taken from the on the pad video of Apollo 11:



In which case it's turbine exhaust in the case of Apollo and possibly the Falcon 9, though I think the Soyuz doesn't use a fuel rich mix of LOX/RP-1 in it's pumps.
 

Arbitrary

New Member
The fact that a rocket burns through a lot more fuel - and therefore produces more water vapour - than an aeroplane probably helps too.
 

Trailspotter

Senior Member.
It may simply be the temperature. Contrail formation does not require ambient humidity.
Yes, the temperature is probably a more important factor here than humidity. However, there is a probable third factor of even greater importance, the temporary reduction of the engine thrust. See the OP update for the explanation.
PS I've also corrected my reply to @Mick West (#6)
 
Last edited:

Tumeni

New Member
Six videos at least, on YouTube, showing a partial contrail from a recent SpaceX rocket.

"SpaceX Falcon 9 CRS-12 Launch from 30000 feet on Delta flight 1420!!!"
Source: https://www.youtube.com/watch?v=b-OfW3KED-k


Seems obvious to me the rocket is passing through the atmospheric layer usually occupied by cruising airliners, and the exhaust is producing the same type of vapour trail (contrail) that an aircraft might do, if it were passing through the same area

So, matching the height of the SpaceX rocket to the typical airliner cruising height ....
 
Last edited by a moderator:
Thread starter Related Articles Forum Replies Date
FlightMuj ISS and Soyuz Antennas. Rotation Speed and Earth Movement Flat Earth 9
Mick West Michael "Mad Mike" Hughes Dies in Rocket Malfunction Flat Earth 2
Mick West Explained: "Beam of Light" in To The Stars Academy header images UFOs, Aliens, Monsters, and the Paranormal 0
Mick West "UFO" Crash in Russia Near World Cup Match - Rocket Part UFOs, Aliens, Monsters, and the Paranormal 4
JFDee Falcon Heavy First Launch - Vertical Rocket Contrail Images and Videos: Contrails, Skies, and Aviation 3
StarGazer Claim: First Image of Space Taken from V-2 Rocket Proves the Earth is Flat Flat Earth 17
StarGazer Measuring Horizon Drop And Earth's Equatorial Bulge From Rocket Launches Flat Earth 2
Mick West Rocket Contrail, South of Monterey, California [ Trident II Test] Skydentify - What is that Thing in the Sky? 4
Mick West Explained: Chinese UFO Crashes in Fiery Crater - Space Junk, Part of Rocket Motor UFOs, Aliens, Monsters, and the Paranormal 28
Jimmyd What is this? A rocket over a civilian airport? Skydentify - What is that Thing in the Sky? 19
Mick West Debunked: 'UFO Trailing Blue Smoke' over airport [Atlas V Rocket Launch] Skydentify - What is that Thing in the Sky? 13
Georgie G Debunked: SpaceX Rocket Crash Landing Anomalies General Discussion 21
MikeC Solved: Tube in MH 17 wreckage?? [9m111 anti-tank rocket from old Il-76 footage] Flight MH17 22
ufoofinterest Ufo over Ibiza: meteor, missile, rocket or simply contrails? [Contrail. Maybe Flight VY2425] Skydentify - What is that Thing in the Sky? 17
Pete Tar Probably not Ison... (rocket launch remnant) Skydentify - What is that Thing in the Sky? 2

Election 2020

Related Articles

Top