Cameras Monitor Rocket Launch
Brent D. Johnson
On Nov. 20, Boeing launched its Delta IV Medium+ (4,2) rocket, which included one of the more significant advances in launch vehicle propulsion system design since the Apollo missions. To monitor the performance of this new technology, the company installed extensive telemetry, including two camera systems from Ecliptic Enterprises Corp.
The RocketCam from Ecliptic Enterprises, which uses a Sony XC-999 sensor, captured this picture of the end-bell nozzle of the second-stage engine from the Delta IV rocket. Courtesy of Boeing.
In traditional Atlas and Titan rockets and in the space shuttle, cryogenic liquid hydrogen and helium run through the end-bell nozzles of the larger rocket engines before being routed to the ignition chamber. This keeps the end bells from melting upon exposure to the hot exhaust gases. However, the Delta IV's endbell nozzle contains new materials that don't require active cooling.
Using Sony's XC-999 sensor, one of Ecliptic's RocketCams was positioned next to the second-stage engine to offer a view of the nozzle throughout the flight, including its complex mechanical extension after first-stage separation. The RocketCam showed the end bell glowing bright red and captured some insulating blankets that puffed out like an inflated balloon -- something that had not been recorded by other kinds of telemetry.
A second RocketCam using the same sensor was mounted on the exterior of the rocket in an aerodynamic fairing that was pointed aftward, capturing first-stage engine ignition at launch, liftoff and ascent, aided by two powerful solid-rocket boosters on each side of the first stage.
Temperature was an issue for the outside-mounted camera because it goes through a phase called maximum dynamic pressure, when the rocket is traveling at a relatively high speed through a relatively dense atmosphere. This occurs about one minute after launch. For tens of seconds, intense friction with the air causes a temperature spike, raising the fairing temperature to hundreds of degrees. Yet, the outboard camera was insulated so that, throughout the live broadcast of the launch, the images it captured remained sharp and steady and gave an impressive view of the solid-rocket boosters and of the first stage cutting away.
The cameras are cabled to a transmitter, which is routed to a pair of antennae on the rocket's skin. Both the Atlas V and Delta IV use NTSC video with onboard digitization; previous launchers have used direct analog. In either implementation, the RocketCam signals are inserted into a transmitter operating in the S-band, which is downlinked to the ground and captured at multiple ground stations, which broadcast the signals live and also record them on Betacam SP tape for analysis.
All future RocketCam applications will use the latest XC-555 sensor from Sony, which is two-thirds the length of the XC-999, measuring 22 x 22 x 75 mm, and weighs 60 g. "We have condensed a lot of parts into a [digital signal processing] chip, which makes it shorter and lighter, and yet we haven't given up any key features or performance," said John Kaloukian of Sony. In fact, the XC-555 has a more sensitive CCD, providing 768 x 494 pixels with a horizontal resolution of 470 lines and 48-dB signal-to-noise ratio.
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