Basic Information
Name	Xi-37
Launch date:	27 January 2024
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
Payload	- Raven4 altimeter (primary role) - Raven3 altimeter for backup apogee separation and backup main deploy - BREO-N flight computer (2nd backup, apogee only) - BRB900 GPS transmitter - Liftoff-activated and apogee-activated smoke trackers with Legendary formulation. - SJCAM C100 on-board video camera, aft-facing
Liftoff mass	3.343 kg.
Stability Margin (minimum)	1.79
Flight objectives	-Test flight of Xi rocket with rebuilt aft section. To accommodate larger diameter motors for future flights, the aft section was fabricated of 3” (76mm) diameter tubing (was 2.5” or 63.5mm diameter) and was made slightly longer. -Aft smoke canister was lengthened to span 3” aft body. -Fins made slightly larger to offset C.G. which lies further aft due to larger aft body section.

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	351 grams
Estimated Impulse	685 N-sec. (est.)
Class	J

Additional information

- Aft section of rocket was completely rebuilt (damaged in prior flight). Aft section now same diameter as forward portion of rocket. A new lift-off activated smoke charge canister made longer to span wider aft body. The aft-body coupler and the motor thrust fitting were 3D printed of PLA plastic. The thrust fitting was proof-loaded prior to installation in the rocket.

Weather conditions
Temperature	-6 °C (21°F)
Wind	NW 5 km/hr (ground level)
Sky	Clear, bright sun
Other	R.H. 86%
Ceiling	unlimited

Launch Event Description

The weather conditions for this launch were “ideal”. Clear blue sky, bright sun, light wind and unseasonably mild temperature. The comfortable conditions facilitated setup of the rocket and launch support paraphernalia. Following our checklist, we proceeded to set up the launch rail assembly and the rocket. 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 unit and Raven units were activated and verified to be functioning nominally. The lift-off activated smoke charge was powered-up and 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.

We headed to where the Launch Box was located, 275 feet south of the pad. To be able to follow the flight in a more effective and stable manner, I layed down with my back on the ground, sitting upright initially to follow ascent off the launchpad. After verifying the sky was clear, the countdown proceeded. At the zero mark, the ignition button was pressed. The igniter fired and approximately one second later the rocket soared skyward, accelerating quickly, climbing largely vertical with a slight tilt to our right. I was able to visually follow the rocket during its powered ascent, which was an estimated two seconds. I lost sight of it after burnout. After perhaps 10 seconds, I spotted the Legendary smoke trail. Shortly after, smoke clouds appeared as the apogee pyros fired and some seconds later I heard the faint ‘pop’ sounds of the pyros, delayed by the distance. It was easy to follow the rocket’s descent progress thanks to the smoke trail, which became twin trails once the apogee-activated smoke charge began to burn. The bright sun and the blue sky made the trails very distinctive, despite the high altitude. As the rocket tumbled downward, its path seemed to twist and turn a lot, clearly the winds aloft were rather chaotic. After tumbling downward for nearly a minute, the parachute pyro charge was seen to fire, and the parachute immediately blossomed. The rocket gently descended, drifting with the light breeze, and after a short while, just prior to landing, disappeared beyond the berm situated to our right. Distance was estimated at 700-800 feet from where we were standing.

We programmed the GPS coordinates of the touchdown site into the hand-held Garmin GPS unit. Indicated distance was 0.15 miles. 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 not far from where we’d parked the car. We packed up and headed back to the car. We drove to a location near the indicated touchdown site. After a short walk, we spotted the rocket. The rocket appeared to be in good condition with all parts accounted for.

Flight Analysis
Event:	Time (sec)	feet	metres
Apogee*	15.5	3970	1210
Separation*	16.4	3960	1207
Chute deployment	61	566	173
Touchdown	86	-	-
Range	-	797	243
Max. velocity	718 ft/sec.	219 m/sec.	mach 0.70
Descent rates:	ft./sec.	m/sec.
Free-fall	82	25
Parachute	17.9	5.5

* Corrected for non-standard base temperature using BRB GPS altitude data.

Post-flight analysis and comments:

Post-flight examination of the flight data indicated that the operation of the two Raven units was fully nominal, with a reported apogee of 4073 feet and 4077 feet (not corrected for base temperature). The BREO unit initially worked nominally, however, stopped recording data during descent, 28 seconds after liftoff. This was expected, due to the sub-zero temperature and the BREO’s known intolerance to cold temperature. It nevertheless performed its role of firing a backup apogee charge. The reported apogees for the three units were within 1%.

Operation of the BRB (GPS) unit was fully nominal. GPS-based apogee reported by the BRB was 1208 metres (3963 m.) The GPS altitude versus Raven4 altitude were plotted on a graph and found to corelate closely using a correction factor of 0.975. This factor differs somewhat from that obtained using Altimeter Correction to Account for Launch Site Temperature webpage. The correction factor using that method is 0.927. The difference in correction factor is not overly surprising, as the air temperature profile with respect to altitude may have been unusual on this day. It was noticed that the wind direction seemed to change sharply at apogee, and the winds along the descent path seemed chaotic, as was observed by the sharply twising smoke trail.

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

The SJ100 on-board video camera provided good footage of the liftoff and initial ascent. The camera lens quickly got obscured by soot that was deposited as a result of leakage of the lift-off activated smoke charge. The leakage appeared to be a result of a snap-ring (which retains an end cap) that was not installed correctly.

Misc photos:

E.14 motor Xi-37\DSCF7414.JPG

Motor thrust disc (3D printed PLA) Xi-37\DSCF7407.JPG

Coupler (3D printed PLA) Xi-37\DSCF7400.JPG

New Smoke Module (lift-off activated) Xi-37\DSCF7417.JPG

Xi-37\DSCF7418.JPG

Xi-37\DSCF7419.JPG

Smoke Canister (apogee activated) Xi-37\DSCF7421.JPG

New fins Xi-37\DSCF7402.JPG

Xi-37\DSCF7406.JPG

Fixture to locate fins for bonding to body Xi-37\DSCF7409.JPG

Fins “tacked” in place on aft body Xi-37\DSCF7411.JPG