Basic Information
Name	Xi-42
Launch date:	22 March 2025
Rocket description	- 3”/ 76.2 aluminum airframe (0.035”/0.89mm) - 4 fins, 2024 aluminum (0.065”/1.65mm) - 3D printed PLA tangent-ogive nosecone - 3D printed PLA boattail fairing/motor retainer - 3D printed PLA aft-mid body coupler - 3D printed PLA aft smoke system support - 3D printed PLA NFB - 42 inch ellipsoidal "Fruity Chutes" parachute
Payload	- Blue Raven flight computer (primary role) - Blue Raven flight computer for backup apogee separation – EggTimer Quark altimeter as 2nd apogee backup and backup main deploy - BRB900 GPS transmitter - Liftoff-activated and apogee-activated smoke trackers with Legendary formulation. - Pair of Pyro Separation Device (PRD) to release chute tethers post-landing - Two BREO flight computers (passive payload)
Liftoff mass	3.329 kg.
Stability Margin (minimum)	2.03
Flight objectives	- Achieve higher altitude flight using APM-J.3 motor. - Test of PRD/timer units - Fly BREO units as a passive payload

Motor details
Motor name	APM-J.3 (44.5mm)
Propellant	AXP-AP7.2 (Ammonium Perchlorate 68% /Epoxy (West System) 23.7%/Aluminum 8% /Lampblack 0.3%)
Grain mass	462 grams
Delivered Impulse	985 N-sec. (static test measurement)
Class	mid J

Additional information

- The purpose of the PRD (Pyrotechnic Release Device) is to release the parachute from the rocket after a preselected time delay following launch. This is intended to mitigate the consequence of the rocket getting snagged in a tree (as happened on Flight Xi-39). There are two PRDs, one in the nosecone and one mounted on the AvBay forward cap, as the parachute tethers are linked to both. PRDs are each triggered by a dedicated timer which is activated during the pre-launch setup of the rocket. For this flight, the nosecone timer was set to 40 minutes and the AvBay timer set to 30 minutes. The timers were custom-designed, built and kindly provided to me by Dyanko Chernov. Pyro charge for the PRD units consist of 50 mg. of Crimson Powder. The PRD was ground tested four times prior to this flight, firing successfully each time, including after a 1 hour soak at -18°C.

- Two BREO flight computers are being flown as a ‘passive payload’. The purpose of flying the units is to verify their operation, as it is planned to use these two BREO units for the recovery control system for a future rocket. The BREOs are connected to conventional pyro units (for apogee and main deployment) which are inert (have igniter elements but no pyro charge).

Weather conditions
Temperature	-8°C (18°F)
Wind	SSE 10-15 km/hr (ground level)
Sky	Thin overcast
Other	-
Ceiling	10k ft.

Launch Event Description

Although it was not a particularly cold day, as a precaution, the AvBay and Nosecone were each wrapped with a pair of chemical hand-warmers and insulation blanket, which was removed just prior to loading the rocket onto the launch rail.

Setup of the launch pad and rocket, using our checklist, went smoothly. No glitches were encountered. The BRB transmitter was activated, then the Nosecone PRD timer was activated. Both Ravens were then activated and both experienced a nominal startup. The Quark was powered up and confirmed ‘ready for launch’. The AvBay PRD timer was then activated. The liftoff-activated Smoke Charge system was armed, and finally the BREOs were powered up.

As usual, for filming the flight, I used my Sony HDR-CX240 Handycam fitted with scope tube. It was kept in an insulated box until just prior to launch.

We headed to where the Launch Firing Box was located, 275 feet south of the pad. After verifying the sky was clear, the countdown proceeded. At the zero mark, the ignition button was pressed. Immediately, the motor thrusted and the rocket soared skyward with a loud roar and bright flame, accelerating at a particularly quick pace thanks to the powerful APM-J.3 motor. The motor burned for an estimated two seconds. We lost sight of the rocket after burnout. Although the rocket was equipped with smoke charges, we did not have expectation of seeing any smoke trails, due to the grey sky. After a period of around 25 seconds, we heard a faint ‘pop’ sound of the apogee pyro. No smoke cloud could be spotted. Although we scanned the sky, we could not locate the descending rocket, and after a minute had passed, we heard a faint ‘pop’ of the chute pyro. Again, no luck in spotting the descending rocket and after waiting a minute or so, we assumed the rocket had by then landed.

We programmed the GPS coordinates received from the BRB transmitter into the hand-held Garmin GPS unit. Indicated distance was 0.46 mile (740 m.) and indicated touchdown location was similar to the previous flight, and not down-wind as expected. We consulted our printed map overlaid with latitude/longitude coordinates and noted that the touchdown site appeared to be in a clear field (away from trees, thankfully) and that the better option would be to pack up our gear and drive there, as the landing site was not that far from a sideroad.

We parked the car and headed toward the touchdown site, about 300 feet away. I soon spotted the orange and white parachute in the distance. As we approached, we could see that all the rocket components were present and in great shape, clearly a nominal descent. The Quark was beeping out the recorded apogee of 6878 feet. I then opened the Featherweight app, and the primary Raven unit gave an indicated apogee of 6922 feet. I was eager to check to see if the two PRDs had fired. Indeed, both had fired, releasing the parachute tethers as designed, expectedly after the 30 and 40 minute delay periods from activation.

Flight Analysis
Event:	Time (sec)	feet	metres
Apogee*	20.0	6387	1947
Chute deployment	96.8	695	212
Touchdown	137	-	-
Range	-	2500	762
Max. velocity	915 fps	279 m/sec.	mach 0.85
Descent rates:	ft./sec.	m/sec.
Free-fall	73	22
Parachute	16.7	5.1

* Corrected for non-standard base temperature of -8°C.

Post-flight analysis and comments:

In just about every respect, this was a fully nominal flight. Both Blue Ravens performed well, reporting apogee of 6922 and 6965 feet. The Eggtimer Quark performed nominally with a reported apogee of 6878 feet (reported altitudes not corrected for base temperature). Operation of the BRB (GPS) unit was fully nominal. GPS-based apogee was 6640 feet (2024m.). All reported apogees were within 5%. Maximum reported acceleration of the rocket during motor burn was 19G’s.

Examination of the Raven axial acceleration data indicated that the APM-J.3 motor had a fully nominal burn that matched static test results. Burn time was 1.75 seconds.

Both PRD/timer units functioned as expected, releasing the parachute tethers following touchdown.

Both BREO units functioned nominally. Reported (non-corrected) apogees were 6989 ft. (2130m.) and 6982 ft. (2128m.). All four pyros fired as expected.

Both smoke charges ignited and burned. The only glitch was that one of the two igniters for the liftoff activated charge did not fire. As such, the grain burned from one end only

Examination of the rocket components verified all were in pristine condition.

Misc photos:

APCP propellant grains for APM-J.3 motor Xi-42\DSCF7803.JPG

APM-J.3 nozzle Xi-42\DSCF7807.JPG

APM-J.3 motor Xi-42\DSCF7810.JPG

Static firing of APM-J.3 motor (Feb.22, 2025) Xi-42\2025-04-02_15-34-54.jpg

Static test thrust & pressure curve Xi-42\APM-J.3-static-results.jpg

PRD timer units Xi-42\DSCF7822.JPG

Nosecone PRD unit & pwr. switch Xi-42\DSCF7818.JPG

Xi-42\DSCF7826.JPG

Nosecone PRD and timer Xi-42\DSCF7816.JPG

AvBay PRD unit Xi-42\DSCF7823.JPG