IntroductionThis web page presents details of Flight SD-2, the second flight of the SkyDart rocket. The SkyDart is a small, simple to construct, and inexpensive sounding rocket that is powered by the A-100M solid rocket motor. The primary purpose of the second flight of the SkyDart rocket was for testing a redesigned Delay Ejection Device (DED), following failure of the original design that was used for SD-1.
Ignition of the pyrogen charge was accomplished using a modified "straw" igniter. This consisted of a Xmas bulb with the filament (bridgewire) coated with GP/neoprene, installed into a length of plastic soda straw. The bottom end was sealed with "hot glue", and the top end left open. Installed in the motor, the igniter butts up against the Pyrogen-DED. A layer of aluminum tape was wrapped around the upper portion of the straw to help ensure the flame would be directed out the top end, directly aimed at the pyrogen charge.|
Launch ReportSunday, December 5, 2004
Wet weather resulted in postponement of the launch for a week. Brisk winds had been forecast for launch day, so additional ballast was used to reduce the peak altitude and downrange drift. However, when we arrived at the launch site, the winds (which had been lighter than expected) diminished to near zero. Although consideration had been given to removing some ballast, this was decided against. The sky was a mixture of cloud and clear blue patches, with a bright sun. The temperature was -1oC (30oF.). All in all, the launch conditions were excellent.
The tripod launch pad was set up first, as usual. The launch rail was adjusted to a vertical orientation. The rocket was then slid into position onto the lower launch rail, then the upper rail was inserted into the lower one. The tripod mounted videocamera was set up about 30 feet (9 m.) from the pad to capture liftoff from up close. The motor ignition system was then set up and tested to ensure that it was functioning properly. Finally, after taking some preflight video footage, the igniter was inserted into the rocket motor, and connected to the ignition box. This accomplished, the observers then headed to safe viewing locations. The ignition system was then armed.
Author installing the upper launch rail just prior to the second flight of SkyDart rocket .
As operator of the videocamera, I positioned myself with the sun at my back, so that the sunlight would illuminate the rocket most effectively. Rob once again had the honourable task of announcing the countdown and pressing the "launch" button.
After the "all ready & all clear" signals were announced, the countdown proceeded...5-4-3-2-1-Ignition!
Nearly immediately, a cloud of smoke was witnessed at the base of the rocket, then a half second later, SkyDart cleared the launch rail and Flight SD-2 was officially underway.The acceleration was very rapid, although less so than for the maiden flight, which employed the faster burning KNDX propellant. The rocket climbed in a very straight and stable manner. Despite the high rate of speed, I did have some success following the rocket during ascent with the videocamera, repeatedly losing, then regaining contact in the viewfinder.
Apogee occurred after about 8 seconds, estimated by Rob to be about 800 feet (250 m.). As the rocket pitched over, a cloud of smoke suddenly appeared as the ejection charge fired. The parachute immediately blossomed. Less than a second later, we heard the delayed "pop" sound from the charge. The rocket drifted downward in a straight and stable manner, and at a rather quick descent rate, as expected owing to the mass of the ballast. Touchdown occurred less than 35 feet (10 m.) from the launch pad. Inspection of the rocket at the landing site indicated that it was in perfect condition and with no apparent damage.
Recovered SkyDart rocket
Flight SD-2 launch photos:
1 SkyDart sitting on launch pad mere seconds from liftoff.
3 Liftoff of SkyDart Flight SD-2.
4 SkyDart coasts skyward following motor burnout.
5 Smoke cloud signalling successful firing of ejection charge, separating rocket into two sections.
6 SkyDart descending under the safety of a fully inflated parachute.
7 Zoomed view of rocket & parachute
8 SkyDart descends into remnants of smoke cloud just above the launch site.
Post-flight AnalysisPost-flight inspection of the rocket and motor showed that all components were in nearly perfect condition, and that the P-DED functioned as designed. The only damage was partial melting of the P-DED body. This was pretty much expected, having been made from aluminum (to ease prototype fabrication). Future units will likely be fabricated from mild steel to eliminate any heat-related damage, although as a "one-shot" device, aluminum proved to be a viable material.
From inspection of the video footage & soundtrack, the following times were excerpted:
The actual duration of the DED delay may be calculated from the above data:
Delay time = 0.4 + 8.7 - 810/1100 = 8.4 seconds (which takes into account sonic lapse time)
Descent rate of the rocket was also calculated from the above data, and determined to be 42 feet/sec. (12.8 m/sec.). This is consistent with the expected descent rate of 43 feet/sec. (13.1 m/sec.) based on the rocket's mass and the parachute's aerodynamic properties.
The reflective mylar strips that were released during parachute deployment did not prove to be of much value as a visual aid. Rob reported noticing the "twinkling" effect, but was quite faint and intermittent. It is possible that more reflective "pieces" are needed to provide a pronounced visual effect. For the next flight, the mylar will be cut into much smaller pieces, perhaps 1 inch square, and a far greater quantity will be used.
Overall, Flight SD-2 was an outright success. The Pyrogen-DED and parachute deployment system proved to work exactly as designed. However, more such flights will be required to assess the reliability of the overall system.
The photo below shows a recently fabricated Pyrogen-DED made from steel. This unit will be used on future SkyDart flights. This lengthened unit allows for delays up to 12 seconds.