Second Flight of Stiga
On January 28, 2012 Armadillo Aerospace launched the rocket Stiga at Spaceport America for a second time. After a 169.5 second ascent, it reached an apogee of between 90 and 95 km above sea level, returning views stretching into Colorado. On the way back down the recovery system failed, and the rocket was destroyed by impact with the ground.
Setup and Launch
Stiga was mostly the same as what flew in December; all of the primary structure like tanks and plumbing were in good shape. The recovery and pressurization body tubes were replaced, and the attachment of the pressurization section was beefed up with two rows of screws. The fin can and boat tail were replaced. The engine had a new nozzle extension welded on, to get more performance over the full burn. The IMU that flew on the first flight had to be sent in for a checkup, but the computer and other sensors were the same.
The rocket, team, and crane truck were on-site on Friday morning to do the post-transport checkout and any last minute modifications. Aside from securing a few cables, there wasn't much to do on the rocket. The launch stand was reinstalled on the pad, and cables were laid out for launch control.
Saturday morning we headed to the spaceport just before dawn. The first task of the day was Purdue mounting their 12lb payload on the rocket. They were again attempting an experiment with the interaction of different fluids in microgravity. I expect it worked quite well until it was flattened.
We moved the rocket out to the pad, then did helium pressurization almost nominally, aside from a leak on the ground support equipment side due to a misalignment in the new fin can. After helium load we found that the GPS was not acquiring a signal and that the Wamore parachute flyback system (AGU) wasn't sending telemetry.
We took the rocket down and pulled apart the payload section, as both RF coax cables run through that section, and it was possible that they were connected backwards. That turned out not to be the case, so the AGU cable was continuity tested end-to-end, yielding a 90 degree connector whose pin was missing.
The GPS was just being finicky, it didn't have anything physically wrong with it. It remains an item that has been less reliable at the spaceport than at home base; for the next rocket we will be switching back to an independent GPS unit rather than the current integrated IMU/GPS.
The rocket was put back together, cameras were installed, the rocket was installed on the launch stand, and propellent loading was commenced and completed normally.
Pad ops completed and crew retreated, at about 11:15AM Neil called out a countdown, and Stiga launched on the first try.
Once the rocket had flown out of sight I drove the four wheeler from the launch pad to launch control, this is what the area looked like while the rocket was in flight. The group near the middle of the image are Professor Steven Collicott and his students from Purdue, standing with the fellow in the salmon shirt, who is our insurance agent.
Launch control itself was inside the trailer, with Wamore on the left and Russ and Phil on the right.
Telemetry was lost above 19.4km, which was unsurprising as the telemetry had not worked at full range during an aircraft-based test. Due to the loss of data numbers are based on models and are approximate, but engine run time and apogee time were acquired from surviving onboard video. Maximum ascent velocity was about 1140 m/s, mach 3.8, at burnout altitude of 28.5km.
Around apogee the video gives an excellent view of the Rio Grande valley extending north past snow-capped mountains, as well as showing a couple of lava fields and the green Elephant Butte reservoir near Truth or Consequences. A dark green streak near the horizon is a river valley that includes Pueblo, Colorado.
The video and subsequent hardware analysis showed that when a coiled rope extended and created a jerk load, the ballute broke a strap that was meant to retain it until the main was released.
After the ballute left the vehicle, the rocket fell nose-down the rest of the way. The main parachute also departed with haste as the rocket entered the thicker atmosphere. Once the rocket gets below the clouds it provides a good view of the spaceport runway and the gravel mine southwest of the vertical launch area.
Telemetry was regained briefly on the way down as the rocket came back within range. It sent some information on event timings, but unfortunately does not send a latched apogee altitude. Apogee was estimated from the position and velocity curve of the last data received, about 10 seconds before the end of the burn, plus main engine cut-off time and apogee time from the onboard video. The best match to the data is at 94.5km above sea level.
From launch control we heard a sonic boom, shorter than the last flight's, followed by the noise of a rapidly falling rocket. The rocket was spotted, and some of us watched as Stiga impacted the ground at 205 meters per second roughly 750 meters from the launch site. This represented kinetic energy of around 5 megajoules. Everything on the rocket was destroyed, except the fins and engine, which were last to hit the ground and were quite overbuilt.
The cloud of smoke is a lithium battery that had been in the engine bay giving up the ghost.
All debris was in close proximity to the rocket. There was no significant propellant onboard, so there was no explosion. Because it was the last tank to hit and because it had about 100psi of gas in it, the LOX tank tube was reasonably intact, though most of the engine bay ended up inside it. The roughly 15 feet of rocket above the intertank bulkhead, including the fuel tank, composite pressurization tank, computer, payload, four HD cameras, and recovery flyback system were compressed into about two feet.
Most of the crew then undertook a shovel recovery of the rocket, though we'd unfortunately forgotten to actually pack a shovel. Some of the rocket was pulled out with the crane truck, then James excavated the remainder by hand.
Six HD cameras left the ground, one memory card survived the landing. Future rockets will feature at least one physically hardened camera and a tough black box recorder of some sort to ensure that flight data can be recovered.
Lee and I went off to recover the ballute and nose cone, whose tracking transmitter worked quite well. It landed about nine miles east of the launch site, and we would have probably never found it if not for the tracker. At apogee the tracker was being received by base stations in central Utah, Arizona, and Texas, so it had more than enough power for its purpose.
The nose paint was blistered this time due to much higher peak speeds. The nose is still in good shape, though, as is the ballute. The ballute will possibly be re-used on the next rocket.
Next up for Armadillo is a larger diameter tube rocket, meant to carry significant payload to 125km.
(Update by Ben Brockert; feel free to email for higher resolution images.)