Basic Information

Name

Xi-22

Launch date:

20 February 2021

Rocket description

- 76.2/63.5mm aluminum airframe

- 4 fins, 2024 aluminum

- 3D printed conical PLA nosecone

- 3 ft. 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

- Apogee-activated smoke tracker with Legendary and Red Dragon II formulation

- Lift-off activated smoke tracker with Legendary formulation

- SQ11 micro-camcorder, aft-facing

Liftoff mass

2.860 kg.

Stability Margin (minimum)

2.78

Flight objectives

-Repeat flight test of new APM-D.1 motor powered by AP composite propellant

-Test new hi-resolution micro-camcorder

-Test effectiveness of lift-off activated smoke tracker to aid tracking during ascent

Motor details

Motor name

APM-D.1

Propellant

APX-N1.0

Grain mass

251 grams

Nominal impulse

493 N-sec.

Class

I

Additional information

-APM-D.1 is a 38mm experimental motor powered by 4 BATES segments of APX-N1.0 (AP/HTPB) propellant. For this flight, a full propellant load is used. Additionally, a new igniter retention system is being tested. The aim of the igniter retention system is to retain the igniter within the motor after it fires to facilitate propellant ignition. Previously, the igniter was ejected from the motor upon firing, which resulted in delayed ignition of the motor.

-In an effort to aid tracking of the rocket following burnout, a new lift-off activated smoke tracker is being tested. A Smoke Canister, with Legendary formulation, is mounted horizontally in the aft body section. The single canister (fabricated of 1 inch steel EMT), with an internal diameter of 27mm, is ignited at both ends of the smoke grain to ensure copious smoke discharge. The smoke charge is electrically initiated by a pair of igniters with KC/xylitol/charcoal pyrolant. A nine volt lithium cell in series with a g-switch (triggered by 6G acceleration) supplies power to the igniters.

-A new SQ11 micro-camcorder is mounted in the aft body section. A 45 degree first-surface mirror allows filming of the flight in an aft-facing direction. A 3D printed combined fairing & mount secures the camera to the rocket.

-BREO flight computer replaced with a new unit due to anomalous operation on previous flights.

Weather conditions

Temperature

-7°C  (19°F)

Wind

S 25-35 km/hr

Sky

Sunny with clear sky

Other

-16°C wind chill

Ceiling

30k ft.

Launch Event Description

Due to the cold weather conditions, in particular the brisk wind, chemical hand-warmer pads were used to keep the AvBay and BRB unit from getting overly chilled. Approximately two hours prior to planned launch, the pads were activated and a pair was taped to opposing sides of the AvBay compartment. Same was done to the nosecone, which houses the BRB transmitter. To help retain the warmth generated by the pads, terry cloth was then wrapped around the pads. The SQ11 micro-camcorder was transported in a small box together with a hand-warmer pad. The BRB receiver unit was enclosed in a thermally insulated 3D printed housing.

As is usual for a winter launch, we used our sled to haul the supplies to the launch site. Following our checklist, we proceeded to set up the rocket. Setup went well, although it took longer than usual due to the difficulties of performing tasks with a freezing wind (most tasks had to be performed wearing gloves, as bare hands rapidly numb and become useless). The first step was to remove the hand-warmer pads from the rocket. The BRB transmitter and receiver were then activated and verified that a good GPS signal was obtained. The BREO was activated and verified to be functioning, followed by the EggTimer unit and Raven. Raven beeped out codes indicating nine volts battery power and three active pyros. The SQ11 camcorder was then unpacked, powered up and installed in the rocket. The lift-off activated smoke charge was then powered up.

For videotaping the flight, I used the hand-held Sony camcorder fitted with scope tube.

After verifying the sky was clear, the countdown proceeded. At the zero mark, the Fusion igniter fired but was seen to be ejected out the nozzle. Despite this, a second or so later, a small flame appeared at the base of the motor. Shortly after, the rocket leapt off the pad and rapidly accelerated skyward trailing a bright yellow flame. As the rocket ascended, the rocket began to weathercock, as expected due to the strong wind. Burn time of the motor was nearly two seconds. Following burnout, a thin trail of smoke clearly marked the path of the rocket as it climbed toward apogee. The bright sun illuminated both the smoke trail and the rocket. After reaching apogee, at which point the rocket had gained significant horizontal velocity due to weathercocking, the primary and backup apogee charges were seen to fire, leaving streaked smoke clouds in the wake. The rocket, now separated into two sections and spewing two trails of smoke, tumbled earthward for nearly half a minute at which point the parachute pyro charge was seen to fire. Immediately the parachute fully blossomed, and the rocket gently drifted with the wind and touched down less than 20 seconds later not too far from the launch pad.

Due to the close proximity of the landing site, we decided it was unnecessary to use the GPS system to locate the downed rocket (the cold weather also played a role in this decision). Arriving at the touchdown site, all the rocket components were seen to be present. The rocket appeared to be in pristine condition. Raven beeped out an apogee of 2265 feet. A quick check indicated that all five pyro charges had fired.

Flight Analysis

Event:

Time (sec)

feet*

metres*

Apogee

12.1

2106

642

Separation

12.6

2100

640

Main deployment

39

306

93

Touchdown

54

-

-

Range

-

221

67

Descent rates:

ft./sec.

m/sec.

Free-fall

80.3

24.5

Main parachute

20.3

6.2

Post-flight analysis and comments:

Post-flight examination of the rocket and data indicated that the operation of the Raven, EggTimer and BREO was fully nominal. The Raven, EggTimer and BREO each gave apogee readings within 9 feet. The BRB GPS data indicated an apogee of  2149 feet, which is within 2% of the base temperature corrected Raven apogee of 2106 feet.

Upon review of the flight data, it was determined that the parachute was deployed by the backup pyro, not the primary. The primary pyro (activated by the Raven) did fire, however, not enough pressure was developed in the cavity to shear the six nylon screws retaining the AvBay to the forward body. This was undoubtedly a result of the cold temperature of the rocket. The larger backup charge was successful (thanks in part to the warmed up cavity from combustion of the primary pyro charge). For future cold-weather flights, a larger quantity of Crimson Powder will be used for the primary charge.

The APM-D.1 rocket motor appeared to perform as expected. The shape of the acceleration curve matched the pressure-thrust curve from the static tests. Tear-down of the motor showed it to be in pristine shape. The casing thermal liner and all casting tubes were essentially intact. The aluminum nozzle, used also for the four static tests, was in pristine condition. The graphite throat insert suffered no erosion.

Apogee for this flight was significantly less than predicted. However, this was clearly a result of the significant weathercocking that occurred due to the strong wind.

The lift-off activated smoke charge functioned as designed, and was of great aid in tracking the rocket during ascent. The burn time of the charge was greater than nominal due to the cold temperature of the smoke grain. The bright sun and clear blue sky played a pivotal role in outlining the smoke trail. It will be interesting to see how effective the smoke trail is under a cloudy (grey sky) condition.

The apogee-activated smoke charge ignited and fully burnt up the Legendary primary grain. However, the sequential Red Dragon II grain did not ignite following burnout of the primary grain. This is likely the result of two factors: (1) the cold temperature, and (2), the planar interface between the two grains. For the next flight, the planar interface will be modified to either a conical interface, or a “touch hole” will be made in the Red Dragon II grain at the interface.

The SQ11 micro-camcorder stopped recording shortly after rocket was placed on the launch pad. This was most likely due to the cold temperature which shut down the electronics.