Basic Information
Name	Xi-30
Launch date:	13 August 2022
Rocket description	- 3”/ 76.2 aluminum airframe (0.035”/0.89mm) - 4 fins, 2024 aluminum (0.065”/1.65mm) - 3D printed tangent-ogive PLA nosecone - 3D printed PLA boattail fairing/motor retainer - 40 inch ellipsoidal "Fruity Chutes" parachute
Payload	- Raven3 altimeter (primary role) - Eggtimer Classic altimeter for backup apogee separation and backup main deploy - BREO-N flight computer (2^nd backup, apogee only) - BRB900 GPS transmitter - Liftoff-activated and apogee-activated smoke trackers with Legendary formulation.
Liftoff mass	3.170kg.
Stability Margin (minimum)	2.45
Flight objectives	- Flight test of APM-E.6 motor with AXP-AP4.1 propellant.

Motor details
Motor name	APM-E.6
Propellant	AXP-AP4.1 (Ammonium Perchlorate 67.8% /Epoxy (New Classic) 25% /Aluminum (atomized) 7% /Lampblack 0.2%)
Grain mass	364 grams
Delivered Impulse	689 N-sec. (per static firing APM-E.6-ST3)
Class	J (38mm)

Additional information

- The APM-E.6 motor had been successfully static fired three times prior to this flight. Simulation indicated that this motor will loft Xi to over 4500 feet (1370 m.) apogee.

Weather conditions
Temperature	26 °C (79°F)
Wind	SW 17-27 km/hr
Sky	Clear with bright sun
Other	Scattered clouds
Ceiling	unlimited

Launch Event Description

Following our checklist, we proceeded to set up the launch rail system and the rocket. No glitches were encountered. The BRB transmitter and receiver were activated and verified that a good GPS signal was obtained. The BREO, EggTimer and Raven units were activated and verified to be functioning nominally. The lift-off activated smoke charge was then armed.

For closeup videotaping the liftoff, I set up my TCL mobile phone on a tripod located about 50 feet from the pad. For filming the flight, I used my Sony HDR-CX240 Handycam fitted with scope tube, as usual. For this flight, which was expected to achieve a particularly high altitude, I decided to try out my pair of wearable binoculars. I bought these some years ago, but hesitated to try them for a rocket launch as they seemed kind of rinkydink. I practiced wearing them, as the field of vision is quite narrow, and I wanted to be confident that I could follow the rocket in flight and concurrently guide the camera scope tube. The magnification is advertised as 4:1, or 400%.

After verifying the sky was clear, the countdown proceeded. At the zero mark, the ignition button was pressed, and the igniter fired. The rocket immediately accelerated off the pad, climbing straight vertical initially, then veering about 10 degrees into the wind. The motor, emitting a brilliant yellow flame, burned for approximately two seconds. After burnout, a faint smoke trail marked the ascent path of the rocket. The trail grew more distinct as the rocket gradually slowed as it climbed higher. I was able to follow the ascent very well through the binoculars I was wearing. After about 15 seconds, a streak of smoke appeared, signaling firing of the apogee separation charge. A second or so later, a second streak of smoke appeared as the backup pyros fired. All this time, the white trail from the liftoff-activated smoke charge, illuminated by the bright sun, was highly visible against the deep blue sky. A second smoke trail from the apogee-triggered smoke charge was then seen to appear, briefly creating a pair of trails, as the first smoke charge was soon depleted. We continued to watch the rocket descend with the aid of the smoke trail and the occasional glinting as the sun reflected off the rockets chrome bands. After nearly a minute of descent time, the main parachute pyro was seen to fire and the chute was deployed. The backup pyro then fired. The rocket continued to fall quite rapidly, as the parachute failed to fully blossom. The rocket then landed about 300 feet away from where we were standing in a field of tall alfalfa and grass.

We programmed the GPS coordinates of the touchdown site into the Garmin GPS unit. Indicated distance was 275 feet (84 m.). We headed toward the touchdown site and soon spotted the tethers atop some tall alfalfa. The rocket appeared to be in good overall condition, thanks to the cushioning of the alfalfa, with the exception of a broken fin and broken boattail. The parachute was still largely folded up. It readily unfurled as I lifted it up, and it was clear there were no snags. The Raven unit beeped out a peak apogee of 4774 feet.

Flight Analysis
Event:	Time (sec)	feet	metres
Apogee*	16.8	4866	1483
Separation*	17.6	4861	1481
Chute deployment	69	665	203
Touchdown	79	-	-
Range	-	481	147
Max. velocity	760 ft/sec.	232 m/sec.	mach 0.68
Descent rates:	ft./sec.	m/sec.
Free-fall	80	24
Parachute	61	19

* Corrected for non-standard base temperature.

Post-flight analysis and comments:

Post-flight examination of the flight data indicated that the operation of the Raven, EggTimer and BREO was fully nominal for each. The reported apogee for the three units was within 0.5%. The GPS based apogee reading obtained from the BRB unit was 4715 feet (1437 m.), which is 3% lower than the corrected barometric altitudes.

Examination of the Raven flight computer acceleration data indicated the APM-E.6 motor had a nominal burn that closely matched the static thrust curve.

Both smoke charges performed nominally. The lift-off activated charge burned for 23 seconds and the apogee-triggered charge burned for 39 seconds. The smoke trails were of immense aid in tracking the flight. Tracking would have been even more enhanced had the second charge burned for a longer time. The smoke canister may be lengthened for future higher-altitude flights.

The wearable binoculars performed surprisingly well. I was able to follow the rocket throughout its entire flight. Better quality wearable binoculars are available and worth considering for future flights.

As a result of the hard landing, two fins were loosened and the boattail fractured. No other damage occurred.

It is not known why the parachute failed to fully unfurl. The last time that this occurred was the flight of Xi-8. Starting with Xi-9, the chute folding method was revised. The following 20 flights experienced nominal unfurling and subsequent blossoming of the parachute. Examination of the parachute at the landing site revealed no tangling of the shroud lines or any other aberration. The chute simply failed to unfold, seeming unable to “catch sufficient air” while falling. Clearly, this anomaly will require further investigation.

The rocket flew to a higher altitude than initial simulations indicated. On previous Xi flights, I used a drag coefficient of 0.50 which correlated well with actual altitude achieved. For Xi-30, the predicted apogee was in the neighbourhood of 4400 feet. As the actual apogee was 4866 feet, I re-ran the simulation using a drag coefficient of 0.40, which resulted in a closer estimation of the peak altitude (4775 feet). Why a lower drag coefficient for this flight? The explanation might be lower base drag due to a combination of boattail and (relatively) long burn time. Considering that base drag accounts for around 20% of total drag, the effect of the boattail and long burn results in essentially zero base drag during the motor burn, and reduced drag due to the boattail during the coast phase. Future flights fitted with a boattail should help answer this question.

SOAR flight simulation:

Results file Xi-30\SOAR400.txt

Raven data:

Barometric and axial acceleration curves Xi-30\Xi-30_raven-basic.jpg

Axial acceleration curve Xi-30\Xi-30_raven-accel.jpg

Eggtimer data:

Altitude versus flight time Xi-30\Xi-30_ET.jpg

BREO data:

Altitude versus flight time Xi-30\Xi-30_BREO.jpg

Launch photos:

Launch prepping Xi-30\2022-08-16_08-23-40.jpg

Author with wearable binoculars Xi-30\IMG_20220813_155702_7CS.jpg