[CRS-4] NASA Thermal Infrared Cameras Capture SpaceX Falcon 9 First Stage Re-entry
Why Space Exploration Stack Exchange recommends it
Space Stack Exchange answerers link it as direct visual evidence of how hot the Falcon 9 first stage gets during re-entry, and as an example of what the thermal data does and does not tell you.
Recommended by 0 people across 0 different months, 2016 to 2024.
What it is
A 2m38s NASA video showing mid-wave infrared camera footage of a SpaceX Falcon 9 first stage during re-entry and flyback after the CRS-4 launch on September 21, 2014. It is uploaded by Matthew Travis with NASA credited as the source, and the imagery shows the stage heating up during descent.
What people said
Cites Hobbes · 2016-02 · Space Exploration Stack Exchange · on “How does the Falcon 9 first stage avoid burning up on re-entry?”
Here's an image of the bottom of the stage before launch. [LINK] As you can see, the entire bottom is covered in white panels. I suspect those panels are a heat shield. This SpaceX press release [LINK] on the introduction of the Falcon 9 v1.1 refers to a heat shield. The reference is a bit oblique, but I think this refers to the first stage. Here's the same area after a successful landing: [LINK] The panels are now charred black, but are still intact. Here's an infrared video [this video] that shows the rocket gets pretty hot - at one point it glows red-hot, and that's before the engines are started for the reentry burn.
Cites user12102 · 2016-02 · Space Exploration Stack Exchange · on “How does the Falcon 9 first stage avoid burning up on re-entry?”
@Puffin in this screen shot [LINK] of the beginning of this video [this video] it's stated "*color scale: MWIR sensor counts*". Counts refers to ADC counts ( search here [LINK] for the word "count") or read the answers to this question [LINK] . Converting a MWIR signal to absolute temperature reliably would be more than a little tricky.
Cites Christopher James Huff · 2020-05 · Space Exploration Stack Exchange · on “Why isn't the Falcon 9 first stage severely damaged by the blast of the second stage following separation?”
They do not complete the flip before igniting the second stage: The first stage actually goes through worse during its reentry burn: For that matter, the Falcon Heavy side boosters have it worse after separation, since they have 9 engines pointed at them that are already running when they separate: The air's thin up there, so the exhaust spreads out and isn't terribly effective at heating solid objects up quickly. They're just built to handle the brief heating...notably, they had to change the grid fins from aluminum to titanium because the aluminum ones had bits melt out of them on some reentries.
Cites Jörg W Mittag · 2024-02 · Space Exploration Stack Exchange · on “Why does the Falcon 9 first stage perform a burn at 60 km altitude?”
WARNING : I will use a lot of simplifications, metaphors, and analogies. If you are a physicist, rocket scientist, or aerodynamicist, please skip this answer :-D This is called supersonic retropropulsion , which roughly means " firing your rocket backwards [LINK] into a gas stream while flying at supersonic speed [LINK] ". While firing a rocket backwards obviously slows it down, this is not the only, and maybe not even the primary , reason for doing a supersonic retropropulsive burn. When flying supersonic through the atmosphere, the gas in front of the vehicle "cannot get out of the way" fast enough. That is essentially what "supersonic" means: one way to think about the speed of sound [LIN