# What is the mysterious cube shaped object observed in the Falcon 9 launch? [duplicate]

For today's(November 15 2018) Falcon 9 launch, at around T+ 06:04 into the mission, we can see a cube shaped object flying near to Falcon 9 first stage. This happens just before the first stage reentry.

What this object? The object seems to be in very stable flight.

• Good question! Possibly the fairing. – Russell Borogove Nov 15 '18 at 21:09
• I doubt it is fairing, the fairing is separated few seconds after first stage separation and it can't be flying in opposite direction – Jithin Jose Nov 15 '18 at 21:15
• May be the shape of the object is a cube, but it may be something very different too. Many more pixels would be necessary to see what it might be. – Uwe Nov 15 '18 at 21:16
• @JithinJose The fairing is flying in the same direction, but as it and the first stage begin to hit atmosphere, the fairing decelerates much more rapidly (because it has a lower ratio of mass to cross section), so the first stage could overtake it. – Russell Borogove Nov 15 '18 at 21:18
• Is there anything else than a fairing that is separated during a successful launch from such a rocket? Something as large as a fairing, no small debris like explosive bolts. – Uwe Nov 15 '18 at 21:41

It's ice. Why? Occam's Razor. At the altitudes the Falcon 9 first stage peaks within there's very little else you would see - there's too much atmosphere to orbit so debris drop rapidly. There's too little atmosphere for any known fauna, and the only man made vehicles that can operate there are things like a launch vehicle - they won't turn up unexpectedly.

Any objects that separated at other times from the vehicle - fairings, for instance - differ too wildly in drag coefficient to remain in proximity with the first stage for more than a few minutes.

The only remaining source of physical objects in the stage's vicinity becomes the stage itself. Since it landed OK and there were no signs of trouble, we can guess it isn't a part of the vehicle. Since the vehicle stores and pumps and vents large quantities of liquid oxygen, we know for certain it will have many deposits of ice, both water ice collecting on outer surfaces as well as solid oxygen forming at vents as decompression rapidly chills the vent output.

The cameras are located near the top of the booster. There is ~40 meters of vehicle below the cameras, lots of room to shed ice out of sight of the camera. As the vehicle falls towards Earth these pieces of ice break free and tumble outward. Their large, thin shape lets them catch the air and slow more rapidly and they come into sight of the camera as they move outward and upward. Tumbling can present many cross sections to the camera, producing unusual shapes.

To the comments doubting the existence of ice at apoapsis - the vehicle clearly remains partly covered in ice throughout the entire mission, as the LOX tankage remains clean of soot after the mission. If all the ice shook free by apoapsis, the retrograde propulsion at the reentry burn as well as the brief exposure to stage two thrust post-staging would deposit kerosene soot on the stage, to be revealed after the ice melts at landing. This image in the hangar indicates the LOX tank remains clean even after presumably melting/drying on land and being transferred to the hangar.

• This was my thought process exactly, but I don't feel we can say anything definitively without better quality footage... – Jack Nov 15 '18 at 22:22
• If you're suggesting it's ice that came from the first stage, I don't see how it got so far ahead of the stage and then fell back past it. If you're suggesting ice from the second stage, the fairing would be at least as plausible. – Russell Borogove Nov 15 '18 at 22:36
• @RussellBorogove I believe the suggestion is the ice broke away from the base of the first stage and drifted back past the camera - I think it appears from behind the stage body rather than coming into view from a distance – Jack Nov 15 '18 at 22:41
• Exactly what Jack said. I'm suggesting ice left the rocket somewhere below the camera and became visible as it drifted outwards and the stage fell past it. – Saiboogu Nov 15 '18 at 22:46
• @Uwe I’d expect any ice chunk that big to have fallen off very early in flight due to vibration. – Russell Borogove Nov 16 '18 at 1:17