Basic Information
Name	Xi-35
Launch date:	3 June 2023
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	- 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. - SJCAM C100 on-board video camera, aft-facing
Liftoff mass	3.388 kg.
Stability Margin (minimum)	2.31
Flight objectives	- First flight test of APM-J.2 motor with AXP-AP7.2 propellant.

Motor details
Motor name	APM-J.2 (45mm)
Propellant	AXP-AP7.2 (Ammonium Perchlorate 68% /Epoxy (West System) 23.7%/Aluminum 8% /Lampblack 0.3%)
Grain mass	411 grams
Estimated Impulse	842 N-sec. (est.)
Class	J

Additional information

- The APM-J.2 motor is identical to the APM-J.1 motor successfully static fired twice, except containing 6% greater propellant load (max Kn maintained by larger throat). Aluminum nozzle shell with graphite throat. Aluminum 45mm casing with epoxy-impregnated poster board thermal liner. Propellant vacuum treated and cured under pressure to achieve density of >99% theoretical.

- Several new and replacement parts were 3-D printed (PLA plastic): Replacement nosecone, replacement parachute piston, new BRB cradle and centering ring, new boattail and new on-board camera mount. The nosecone and boattail were both sanded to a fine surface finish and painted.

Weather conditions
Temperature	34°C (93°F)
Wind	S 10 km/hr (ground level)
Sky	Crystal clear, bright sun, some clouds
Other	-
Ceiling	unlimited

Launch Event Description

Prior to beginning our trek to the launch site, the aft section of the rocket was wrapped with a double layer of aluminum foil to reduce solar heating of the motor while sitting on the pad. This was deemed necessary due to the high ambient temperature at launch time.

Once we arrived at the site (a 10 minute walk), we followed our checklist to set up the launch system and prep the rocket. Once the launcher was set up, the BRB transmitter and receiver were activated and verified that a good GPS signal was obtained. The lift-off activated smoke charge was powered-up then armed. The on-board camera was powered-up and set to record mode. The BREO units and Raven unit were activated and verified to be functioning nominally. The access hatch was then closed. The aluminum foil was then stripped off the rocket.

For filming the flight, I used my Sony HDR-CX240 Handycam fitted with scope tube. Once again, I wore wearable binoculars to help visually follow the rocket in flight.

We headed to where the Launch Controller 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. The igniter fired and approximately two seconds later, the rocket roared skyward, accelerating very quickly, climbing straight vertical. I lost sight of the rocket due to its rapid climb rate. I quickly removed the binoculars in order to restore field of vision, and scanned the sky for sign of the rocket. After perhaps 10 seconds, I spotted smoke clouds from the apogee pyro charges. A thin smoke trail then began to form as the apogee-triggered smoke charge began to burn. As such, I was able to follow the rocket’s descent until the charge burned out after about a half minute. I then briefly lost sight of the descending rocket. I heard a pop sound and spotted the rocket descending under a fully inflated parachute, no more than a few hundred feet distant from where we were standing. The rocket gently descended, drifting directly overhead, over the launch pad, and touched down about a hundred feet downwind of the pad.

We then programmed the transmitted GPS coordinates into the hand-held Garmin unit.

The indicated distance to touchdown site was 500 feet, however, in the opposite direction to where the rocket actually landed. We double-checked and verified we’d entered the correct coordinates. We quickly concluded that the BRB transmitter must have lost power, possibly due to the shock loading of parachute deployment. As such, the transmitted GPS coordinates would have been the last location prior to power loss. We reverted to using the back-up Landing Locator (which we always use for redundancy). I headed toward the touchdown site, guided over FRS radio by my brother who manned the Landing Locator. Although the rocket did not drift far, the foliage at the site is tall and spotting the downed rocket can be a bit of a challenge. However, I soon spotted the parachute directly ahead of me. The rocket appeared to be in great shape. Raven beeped out an apogee of 4738 feet (1444m.).

Flight Analysis
Event:	Time (sec)	feet	metres
Apogee*	16.4	5034	1534
Separation*	17.3	5023	1531
Chute deployment	72.6	676	206
Touchdown	110	-	-
Range	-	103	32
Max. velocity	896 ft/sec.	273 m/sec.	mach 0.82
Descent rates:	ft./sec.	m/sec.
Free-fall	74.2	22.6
Parachute	14.7	4.5

* 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 was fully nominal, with a reported apogee of 4716 feet (5034 feet, corrected for base temperature of 34°C.). Both BREO units function nominally. Reported apogee was 1447 m. (4747 ft) and 1451 m. (4760 ft.), respectively for BREO-1 and BREO-2. It was discovered that a surface-mounted capacitor had broken off the BREO-2 unit, likely due to a cold solder joint. It is unknown at what point in time this occurred.

The BRB (GPS) transmitter had shut down at some point in the flight, possibly at chute deployment, based on the last transmitted GPS coordinates received. The downloaded data from the unit was completely lacking of any GPS coordinates. Somehow this data got erased. When prepping the BRB transmitter prior to the flight, there was an intermittent issue with the power connection. I had thought the problem was with the battery connector, consequently, I replaced the connector. Examination of the unit after the flight indicated the problem was still present, the source of which could not be definitively isolated. I performed a “backyard test” of the BRB unit and it functioned nominally, storing GPS data as expected. I contacted Greg Clark of BigRedBee.com and asked if he might know what could have caused the data glitch (if the unit simply lost power the data should have remained stored). He was unsure but suggested there could be a latent bug in the firmware. As the GPS transmitter is a “flight critical” component of the rocket, for the next flight the BRB transmitter will be replaced with a new unit that I’d procured last summer.

Examination of the Raven flight computer acceleration data indicated that the APM-J.2 motor had a nominal burn that matched the test data.

Both the lift-off activated and apogee activated smoke grains burned nominally. The post-apogee smoke trail was a great aid in visual sighting the rocket, which would not have been visible otherwise due to the altitude.

Once again, the SJCAM C100 on-board video camera worked well, providing good quality footage of the entire flight.

J.2 Motor and propellant:

Xi-35\DSCF7154.jpg

Xi-35\DSCF7136.jpg

Xi-35\DSCF7139.jpg

3-D Printed parts:

Nosecone before & after sanding/painting Xi-35\DSCF7151.jpg

Nosecone and BRB cradle/centering ring Xi-35\DSCF7143.jpg

BRB cradle with BRB in place Xi-35\DSCF7146.jpg

Boattail before & after sanding/painting Xi-35\DSCF7149.jpg

Boattail installed on rocket Xi-35\DSCF7152.jpg

Xi-35\DSCF7157.jpg