Basic Information
Name	Xi-32
Launch date:	3 December 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 - 42 inch ellipsoidal "Fruity Chutes" parachute - 18 inch square drogue parachute
Payload	- Raven3 altimeter (primary role) - BREO-N flight computer 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. - SJ100 on-board video camera, aft-facing
Liftoff mass	3.240 kg.
Stability Margin (minimum)	2.50
Flight objectives	- Flight test of APM-E.14 motor with AXP-AP4.7 propellant. - Trial of drogue chute deployed at apogee to stabilize rocket during descent to improve on-board camera footage.

Motor details
Motor name	APM-E.14 (38mm)
Propellant	AXP-AP4.7 (Ammonium Perchlorate 65.8% /Epoxy (New Classic) 24%/Aluminum 10% /Lampblack 0.2%)
Grain mass	353 grams
Estimated Impulse	690 N-sec. (est.)
Class	J

Additional information

- The AXP-AP4.7 propellant was successfully static fired in a BEM prior to this flight.

- A square drogue chute fabricated of ripstop nylon was packed and stowed in the mid-fuselage, released as rocket separates at apogee. The chute was protected from ejection charge heat with a fibreglass fabric blanket.

Weather conditions
Temperature	-16 °C (3°F)
Wind	WSW 10-15 km/hr (ground level)
Sky	Clear, bright sun
Other	-Scattered cirrus clouds - wind chill -22/-24°C.
Ceiling	unlimited

Launch Event Description

To help prevent the flight computers from getting overly cold, a pair of chemical hand warmers were taped to the outside of the AvBay prior to heading to the launch site. The same was done to the outside of the nosecone, which houses the BRB unit (these hand warmers are removed prior to placing the rocket on the launch rail).

Following our checklist, we proceeded to set up the launch rail system and the rocket. The cold weather slowed setup. Fortunately, no glitches were encountered. Once the launcher was set up, the BRB transmitter and receiver were activated and verified that a good GPS signal was obtained. The BREO units and Raven unit were activated and verified to be functioning nominally. The lift-off activated smoke charge was powered-up then armed. Finally, the on-board camera was powered-up and set to record mode.

For filming the flight, I used my Sony HDR-CX240 Handycam fitted with scope tube, as usual. The camera had been housed inside an insulated box heated with a pair of chemical hand warmers. It was taken out of the box just prior to filming the flight.

For this flight, which was expected to achieve a fairly high altitude, I decided to once again use my pair of wearable binoculars.

We headed to where the Launch Box was located (270 feet south of the pad). When we got there, we realized that the launch pad was oriented such that the launch rail blocked the view of the rocket. Although this was a rather minor concern, I made a mental note to ensure that we take care in the future to orient the pad suitably.

After verifying the sky was clear, the countdown proceeded. At the zero mark, the ignition button was pressed. However, no sign of igniter firing. After waiting two minutes, I approached the rocket, disarmed the Launch Controller and proceeded to do a continuity check of the igniter (positive) then removed and reconnected plugs and igniter clips. I also switched over to the AUX relay of the Launch Controller, as no obvious fault could be found with the igniter setup. We decided to try again rather than change the igniter.

This time the igniter fired. After a second or two, the rocket very rapidly accelerated off the pad, veering slightly to the left (into the wind) after departing the launch rail. I soon lost sight of the climbing rocket, due to the rapid climb rate and limited field of view of the wearable binoculars. I immediately removed them and scanned the sky. After perhaps 10 seconds, I spotted the Legendary smoke trail. Shortly after, smoke clouds appeared as the apogee pyros fired. It was easy to follow the rocket’s descent progress thanks to the smoke trail, illuminated by the bright sun, and made distinct by the blue sky. After an additional 10 seconds of descent, the smoke charge burnt out. However, the descent of the tumbling rocket was visually observable by the bright flashes of the sun glinting off the rocket’s chrome bands. It was apparent, by the tumbling action of the rocket, that the drogue chute had not unfurled. The rocket continued its tumbling descent beyond the point in time at which the main chute should have deployed. It did not, and the rocket struck the ground some 500 feet downwind of the launch site.

We programmed the GPS coordinates of the touchdown site into the hand-held Garmin GPS unit. Indicated distance was 473 feet (144 m.). We then looked at our map of the launch site area that was overlaid with a latitude/longitude grid. We pinpointed the touchdown site as being near the edge of a wooded area. We headed out on foot to recover the rocket. Fortunately the snow cover was not very deep (perhaps 10 inches) and we made good progress. We soon spotted the downed rocket, lying at the very edge of the treed region, as expected. The rocket appeared to be in good condition with no apparent damage with all parts accounted for. We then noticed that the AvBay was still joined to the forward fuselage. The main chute remained within the rocket. I then carefully removed the AvBay hatch and de-powered the flight computers, as it was possible the main chute pyros were still live.

The on-board camera, which was still recording, was turned off.

We realized then that it was perhaps fortuitous that the main chute had not deployed, as the rocket would then have drifted further and have landed in the treed zone and, quite possibly, got caught in a tree.

Flight Analysis
Event:	Time (sec)	feet	metres
Apogee*	15.1	3806	1160
Separation*	16.2	3793	1156
Chute deployment ^▪	61	670	204
Touchdown	69	-	-
Range	-	484	148
Max. velocity	731 ft/sec.	223 m/sec.	mach 0.70
Descent rates:	ft./sec.	m/sec.
Free-fall	81	24.7
Parachute	17.6	5.4

* Corrected for non-standard base temperature.

^▪Main pyro fired but chute did not deploy

Post-flight analysis and comments:

Post-flight examination of the flight data indicated that the operation of the Raven was fully nominal, with a reported apogee of 4306 feet. Both BREO units initially worked nominally, however, both stopped recording data shortly after apogee. The BREO-1 unit stopped recording after 34 seconds and the BREO-2 unit stopped recording after 20 seconds of flight. The reported apogee for the two units was within 1% of the Raven value. Both BREO units fired their apogee pyros. The BREO-2 unit did not fire its main (chute) pyro. It is suspected that the cold temperature at the time of launch (-16°C.) caused the two BREO units to shut down. The BREO has not (yet) been tested for cold temperature operation, unlike the Raven. The Raven had been tested, some years ago, for operation following a 12 hour cold-soaking at -25°C. (-13°F.). Operation following the cold-soak was nominal. For future flights in cold weather, an electric heater system is being considered to protect the BREOs from the extreme cold.

Operation of the BRB (GPS) unit was fully nominal. There was no data drop-out over the entire flight duration, unlike the previous flight which suffered a 14 second data drop-out during ascent. GPS-based apogee reported by the BRB was 3734 ft. (1138 m.) which is within 1.9% of the Raven apogee, corrected for base temperature. The GPS altitude corelated closely to barometric altitude, corrected for base temperature, that was recorded by the Raven, with the exception of the ascent portion of the flight, where GPS altitude reporting lagged.

The reason why deployment of the parachute did not occur was apparent once we opened up the parachute section of the rocket. The parachute piston was discovered to be broken into many pieces, have catastrophically failed when the Raven main pyro fired. This 3D printed piston, made of PLA plastic, was first flown on Flight Xi-13. As such, this piston served the following 20 flights without incident. Why did it fail this time? Four reasons are put forth:

1) the type of fragmentation suggested brittle failure, undoubtedly due to the cold temperature affect on the PLA plastic.

2) examination of the fractured parts revealed the piston model was incorrectly sliced. It should have been printed solid (100% infill density) but in fact, the fill density was a lot less, perhaps 50%. This would have weakened the part relative to the expected strength.

3) the nylon screws, of which there are six #6-32 screws joining the forward body to the avbay, have a greater shear strength at low temperature. This would have required a higher pressure (generated by the main pyro charge) to shear the screws. This higher pressure would have increased structural loading on the piston.

4) although the piston is visually examined after each flight, it is possible that an undetected fatigue crack existed.

For the next flight, a more robust 3D printed piston will be fabricated, ensuring a solid infill when sliced. A sample piston will be structurally tested to failure. In addition, the flight piston will be proof-load tested to ensure structural integrity at design pressure, with a suitable margin.

Damage to the rocket as a result of the free-fall landing was minor. The snow and frozen vegetation absorbed much of the impact energy. One fin was loosened and a small dent in the forward body section resulted. Fortunately, the expensive main parachute was not damaged by the heat blast resulting from the fractured piston.

Examination of the Raven flight computer acceleration data indicated the APM-E.14 motor had a nominal burn that closely matched the design data.

Once again, the SJ100 on-board video camera worked very well, providing good quality footage of the entire flight. The camera was not adversely affected in any way by the cold ambient temperature.

The drogue chute, which was intended to stabilize the rocket during descent following apogee, did not unfurl. In the video footage, the drogue chute could be seen in its folded state. This is most likely due to the cold, which stiffens the fabric, combined with the fabric being too heavy (70 gsm). For the next flight, a new drogue chute will be fabricated of much lighter ripstop nylon (40 gsm).

The aft (lift-off activated) smoke grain ignited and burned. Both igniters fired immediately as the rocket accelerated along the launch rail (this was captured on the video). The charge burned for 34 seconds, indicating that ignition successfully occurred at both ends of the smoke grain. The smoke trail was very effective in visually tracking the rocket. The apogee-activated smoke grain did not ignite. Examination revealed the the igniter burnt, but not the smoke grain. A small flaw in the hot-glue seal of the igniter capsule apparently allowed the ignition powder (a mixture of KC, xylitol and charcoal) to leak out during handling.

The hand-held Sony videocamera functioned well over the full duration of the flight. Clearly the insulated and heated stowage box served its purpose well.

Misc photos:

Drogue chute Xi-32\DSCF6958.JPG

AXP-AP4.7 propellant segments Xi-32\AP4.7-grains.JPG

Broken chute piston (left); intact piston (right) Xi-32\DSCF6962a.jpg

Raven data:

Barometric and axial acceleration curves Xi-32\Xi-32_Raven_ basic.jpg

Axial acceleration curve Xi-32\Xi-32_Raven_ accel.jpg

BRB:

Flight path over terrain Xi-32\Xi-32_BRB_marked.jpg

BREO data:

Altitude versus flight time for both BREO units Xi-32\Xi-32_BREOs.jpg

Launch photos: