The video of NASA testing its Space Launch System in the desert about month ago made for some pretty spectacular viewing. Ironically, however, using the world's most powerful rocket to light up six tons of propellant a second was always going to leave something in the dark, with cameras picking up the blast detail as nothing but a white, hot mess. As it turns out, NASA's B camera was a pretty capable piece of gear, with the agency taking the opportunity to test out an advanced high dynamic-range camera and capture the massive rocket plume in unprecedented detail.
If you've ever sat with your camera indoors and aimed it towards the window you'll know the difficulty in trying to balance the contrasting light. Radiant sunshine doesn't frame well with shade or poorly lit rooms, which is why photographers and cinematographers love to shoot in the golden hour, the period close to sunrise or sunset when the sun's glow is softened to make for more evenly lit shots.
Even the scientists working on humanity's most complex aerospace projects aren't immune to this problem, which is why when you see the video of the Space Launch System test no real detail can be seen in the rocket's ultra-bright plume.
High dynamic range (HDR) imaging is a technology designed to overcome this problem. Some versions, such as Magic Lantern's custom firmware mod for Canon's DSLRs, shoot two different ISO values in quick succession, but more common are the type that capture frames at different exposures and then morph them together to present a shot with a nicely balanced light.
This is the functionality you'll find in the iPhone and new cameras like the Ricoh's Theta S, but capturing the fieriest of rocket blasts is going to take something more sophisticated than these compact shooters can handle. Enter NASA's High Dynamic Range Stereo X (HiDyRS-X), a state-of-the-art video camera built specifically to capture the blinding glow of the biggest rocket blasts we've ever seen.
The HiDyRS-X works by capturing multiple, slow-motion video exposures at the same time and then mixing them together. This is a different to how things have worked previously, with NASA looking to avoid using multiple cameras or the same camera at different intervals to gain the multiple exposures needed for a high dynamic range video. It says it was able to achieve this by controlling camera exposure at the chip/pixel level and then integrating it into the camera.
The team had put the HiDyRS-X through its paces a couple of times before on smaller rocket blasts, but the SLS demonstration would be its biggest test yet, with the booster plume brightness several orders of magnitude brighter. There were a few hiccups, with the camera's automatic timer failing as the rocket lit up and the resulting ground shaking knocking its power cable loose, but the team was able to capture a snippet of the test, which can be seen in surreal, slow motion below, in contrast with the standard video we have seen previously.
Why do we want to film rocket plumes anyway? Well, aside from looking completely badass, these captures give NASA scientists an entirely new perspective on these rocket tests. The images are another observational tool and can help them glean critical data that would never be available with a standard camera, and is something they hope can be applied to not just propulsion systems, but launch facilities and planetary rovers as well.
"I was amazed to see the ground support mirror bracket tumbling and the vortices shedding in the plume," says Howard Conyers, a structural dynamist at NASA's Stennis Space Center. Speeding up the video also provided some interesting insights. "I was able to clearly see the exhaust plume, nozzle and the nozzle fabric go through its gimbaling patterns, which is an expected condition, but usually unobservable in slow motion or normal playback rates."
NASA is currently working on a second prototype of the HiDyRS-X camera with more advanced HDR capabilities. The June 28 demonstration of the SLS test was the last full-scale test for the booster before uncrewed test flights kick off in 2018.
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