Basic Information
Name	Xi-28
Launch date:	26 March 2022
Rocket description	- 76.2 aluminum airframe - 4 fins, 2024 aluminum - 3D printed tangent-ogive PLA nosecone - 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. - SQ11 micro-camcorder, aft-facing
Liftoff mass	3.359 kg.
Stability Margin (minimum)	1.76
Flight objectives	- 1^st flight powered by APM-C.4 motor with KNPSB propellant.

Motor details
Motor name	APM-C.4
Propellant	Cast KN/KP/Sorbitol ratio 35/30/35
Grain mass	411 grams
Nominal impulse	593 N-sec.
Class	I

Additional information

- The APM-C.4 motor is a two segment BATES grain motor of 51mm diameter. This motor was static fired twice, with fully nomial performance, prior to this flight.

- The apogee-activated smoke charge for this flight utilizes a larger diameter canister for greater smoke output. Previously, the canister was made from ¾” EMT. The new canister is made from 1” EMT, which increases the smoke output by 60%.

Weather conditions
Temperature	-14°C (7°F)
Wind	NW 20-30 km/hr
Sky	Clear with bright sun
Other	-24°C windchill
Ceiling	unlimited

Launch Event Description

Following our checklist, we proceeded to set up the new launch rail system and the rocket. A single glitch was encounted while prepping the Launch Controller. A banana plug attached to the end of an ignition lead wire came off. It appeared to have failed as a result of a cold solder joint, undoubtedly made more brittle by the cold ambient temperature. This was soon repaired in an improvised fashion using tools and supplies in our Field Repair Kit.

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 on-board camera was then powered up followed by the electrically triggered lift-off activated smoke charge.

For videotaping the flight, I used my Sony HDR-CX240 Handycam fitted with scope tube.

After verifying the sky was clear, the countdown proceeded. At the zero mark, the ignition button was pressed, the igniter fired immediately. Smoke began to build up at the base of the launcher, and a second or two later, the rocket very rapidly accelerated off the pad, climbing straight and true. The motor burned for approximately one second, as expected. We lost sight of the rocket following burnout, not noting any smoke trail. I thought at the time that the lift-off activated smoke charge had failed to ignite, but we soon spotted the distinct white smoke trail forming as the rocket arced into the wind as it climbed toward apogee. A few seconds later the apogee smoke charge cloud appeared, followed by a ‘pop’ sound some seconds later.

A second smoke trail then appeared, as the apogee-activated charge began to burn. The rocket tumbled earthward, its descent path clearly seen by the trail of smoke and the sun glinting off the rocket. A little over a half-minute later, the parachute ejection pyro was seen to fire and nearly immediately the chute fully inflated. The rocket gently drifted downward, carried by the wind in a south-east direction. The smoke charge burned out shortly before the rocket touched down, estimated at 1500 feet away, over the crest of the nearby embankment.

We programmed the GPS coordinates of the touchdown site into the Garmin GPS unit. Indicated distance was 0.31 miles (0.5 km). We headed toward the touchdown site, and as we approached, I saw several trees in the viscinity, and crossed my fingers that the rocket missed them. Scanning the treetops as we got closer, I was disheartened as I spotted the parachute caught in branches near the top of a tree. I then noticed the rocket sections hanging below. Fortunately, the tree was not a particularly tall one, and the lowest section of the rocket was hanging about 15-20 feet (5-6 metres) above ground level. Luckily, we were able to borrow a long “painters pole”. Using the pole, I was just able to reach and snag the lower section of the rocket, and managed to tug sufficiently hard that the branches holding the rocket parts all snapped and released our captive rocket. Thanks to the cold, the branches were very brittle and snapped readily. The only damage to the recovered rocket was a cracked nosecone, which fracture when striking the frozen earth.

Flight Analysis
Event:	Time (sec)	feet	metres
Apogee*	13.4	3061	933
Separation*	14.4	3047	929
Chute deployment	52	576	176
Touchdown	83	-	-
Range	-	1783	544
Max. velocity	636 ft/sec.	194 m/sec.	mach 0.60
Descent rates:	ft./sec.	m/sec.
Free-fall	76	23.1
Parachute	18.8	5.7

* Corrected for non-standard base temperature.

Post-flight analysis and comments:

Post-flight examination of the rocket and data indicated that the operation of both the Raven and EggTimer was fully nominal. The BREO unit stopped recording at the 52 second mark, coinciding with chute deployment. Curiously, the same thing happened on Flight Xi-25 and Xi-27. The cause in this case was determined to be a broken wire leading to the battery. The Raven, EggTimer and BREO each gave apogee readings within 0.3%. The GPS based apogee reading obtained from the BRB unit was 3143 feet (958 m.).

Examination of the Raven flight computer data, and post-inspection of the rocket motor, indicated that the APM-C.4 motor had a fully nominal burn with the acceleration curve matching the static test thrust curve reasonably well.

Post-flight examination of the lift-off activated smoke tracker confirmed that the smoke grain had burned. However, based on the burn time obtained from the video footage (30 sec.), only one end of the grain ignited. This explains why the smoke trail during the initial part of the ascent was too faint to be readily observed. Both igniters were found to have fired. It is likely that the cold temperature of the smoke grain was responsible for this anomaly.

The on-board SQ11 micro-camera did not record any flight footage. The recording stopped shortly after the camera was installed in the rocket. This was no doubt due to the cold temperature and wind chill.

Raven data:

Barometric and axial acceleration curves Xi-28\Xi-28_basic.jpg

Axial acceleration curve Xi-28\Xi-28_accel.jpg

Eggtimer data:

Altitude versus flight time Xi-28\Xi-28_ET.jpg

BREO data:

Altitude versus flight time Xi-28\Xi-28_BREO.jpg

Miscellaneous photos:

APM-C.4 motor Xi-28\DSCF6804b.JPG

KNPSB propellant grains (prior to applying primer) Xi-28\DSCF6803a.JPG

Thrust/pressure curve for APM-C.4 Xi-28\C.4_static_test_results.jpg

Launch photos: