At the end of September I saw something unusual in our early evening sky. Out of the north I saw an object that looked like a satellite trajectory but had an apparent thrust plume trailing behind it. My heart started racing a bit because we don’t have thrust plumes appear in our sky. The closest launch facilities I know of are an ocean away.
An astrophysicist from ANU in Canberra explained in the above news story that the sighting coincided with a rocket launch in China. All the news agencies relied on that assessment, given that the source is a credible professional from a reputable institution.
My problem is that we are so many thousands of miles down range from the launch site in China. Why the thrust plume? Would it not be at orbit altitude by the time it reached this far down range in Sydney? Not only orbit altitude I would think, but wouldn’t it have enough time (and need) to achieve stable low earth orbit velocity by the time it travelled this far?
Why all the thrust fury this far down range. Can the plume serve as a kind of finger print indicating the altitude is much lower in the atmosphere than low earth orbit? Or perhaps it’s launch site is much closer to Sydney?
Well it’s definitely not a UFO as you can see the rocket in the photo as it detaches from multiple stages. As the rocket climbs, it becomes more visible within an extended radius. How far away exactly was the launch site?
I measured it with google earth to be about 8,600km (5,300miles). At that distance I guesstimated an object with a running start already at low earth orbit speed would reach here in about 12 minutes.
Thanks for that link. I didn’t see launch dates in the article. But that launch site mentioned is far to the SW. I was lucky enough to view the vehicle from horizon to horizon. It appeared out of the north and disappeared into the SE - flying in a south easterly direction.
I heard communist china were doing some stuff with that, but hypersonic shockwaves tend to be either be non existent (to high up) or a bright orange/red if it’s lower down.
I wondered about that possibility. If caused by some kind of compression shock, it wouldn’t be in the vacuum of space. Alternatively if it is still the result of thrust, could it really be seen in the vacuum of space? I have a hard time finding an answer to that question. Watching SpaceX on board cameras, the thrust seems to become quite hard to see at higher altitudes.
According to later reports it seems the (supposed) vehicle suffered a malfunction. It seems to be stuck in a GTO, so in a highly elliptical orbit with the minimum at low earth orbit altitudes and the high just short of GSO altitude. This is assuming the match up in time of the launch reasonably assures it’s the same vehicle.
Assuming it is the same vehicle, it seems that any burn over Sydney would likely be to raise the apogee as a GTO manoeuvre. But wouldn’t this likely be at high enough altitude (leo) that the atmosphere is near vacuum, making the plume mostly invisible?
I was able to find some info on research done on thrust plumes in a vacuum. Like you say they still exist in a vacuum. But I found it very difficult to find information on how visible or invisible the plume would be in a vacuum vs in the atmosphere. Do you have any thoughts on how to find out about the visibility of the plume? I ran out of ideas, but it still bugs me.
Idk any ways to hard measure it but I found this old photo of a shuttle, it shows that plumes most certainly still exist in a vacuum, the reason the Falcon 9 plume fades is because it’s mostly caused by the carbon reacting with atmospheric oxygen (lighting also has a very significant role) China use mostly hypergolic fuels, so I imagine it’s a different process.
Thanks. That’s the best image yet showing visible plumes in a vacuum. Looks like reaction control thrusters. Hypergolic fuels are more visible than liquid hydrogen? The lunar module lift off photos I think also used hypergolic fuels but for some reason look invisible, perhaps different chemistry or maybe lighting as you said?
As far as space shuttle ascent, solid rocket boosters are of course very opaque. But the liquid hydrogen burn of the main engines is pretty clear from most images.
I was surprised to read the Chinese Long March 3B seems to use hypergolic fuels for all stages except the 3rd stage which is liquid hydrogen. That might add to the confusion if the 3rd stage was responsible for the gto burn.
