Basic Information

Name

Z-31

Launch date:

7 June, 2017

Rocket description

- 63.5mm aluminum airframe

- 4 fins, birch plywood, reduced span

- birch elliptical nosecone

- 3 ft. ellipsoidal parachute

- ultra-low-power pyros

Payload

- Raven altimeter

- BRB900 GPS transmitter

- Smoke charge (activated by Raven at 2900 ft. level)

- Apogee Backup Timer

- SJ1000-SC Video camera

Liftoff mass

2.587 kg.

Stability Margin (initial)

0.96

Flight objectives

Test new smoke charge

Motor details

Motor name

Impulser-X

Propellant

KNDX

Grain mass

383 grams

Nominal impulse

451 N-sec

Class

I

Additional information

-Previously, smoke charge was cast grain of KN-Sorbitol (59/41 ratio, fired by a Spitfire II igniter). This was found to be fairly hygroscopic, compromising grain ignition. For Z-31, smoke charge is cast KN-Xylitol (66/34 ratio). This was found to be non-hygroscopic. 66/34 ratio was chosen to obtain desired burn rate of 2mm/second. New igniter pyrolant is powdered mixture of potassium chlorate/xylitol (75/25 ratio).

Weather conditions

Temperature

23°C

Wind

N 20-25 km/hr

Sky

Mainly clear; scattered clouds

Other

RH 50%

Ceiling

unlimited

Launch Event Description

Setup of the rocket proceeded smoothly with no glitches. Raven checkout beeped eight times for voltage and gave 4 positive indications for the 4 pyros. Backup timer was then tested and confirmed to be operating nominally. For videotaping the flight, I used the hand-held camcorder (with scope tube).

After verifying the sky was clear, the countdown proceeded. Immediately after ignition switch was closed, motor ignited and rocket accelerated rapidly off the pad. Rocket veered somewhat from vertical, slanting with the wind. The motor burned for approximately 1.5 seconds. Rocket disappeared from sight soon after burnout. Around 15 seconds after burnout we spotted the smoke clouds from the apogee charges and heard the ‘pop’ of the pyro firing shortly afterward. A distinctive smoke trail was seen as the rocket made a tumbling descent. Owing to the smoke trail and sun glinting off the rocket’s chrome bands as it tumbled, the descent was easy to follow. The smoke charge burned for nearly half a minute. After that, the rocket could not be seen due to the downrange distance. No sign of chute deployment was apparent.

After we’d presumed rocket had landed, we programmed the BRB GPS coordinates of the landing site into the Garmin hand-held GPS unit. The distance was indicated as 0.41 miles (0.66km) downwind. When we arrived at the landing site, the rocket appeared to be in good condition with the exception of one loosened fin. The nosecone was still in place. It was noted that all three apogee deployment pyros had fired. Raven beeped out an apogee of 3696 feet (1125 m.), which closely matched the simulation prediction.

Flight Analysis

Event:

Time (sec)

feet

metres

Apogee

15.0

3672

1119

Separation

16.1

3660

1115

Main deployment

-

-

-

Touchdown

71*

-

-

Range

-

2136

651

Descent rates:

ft./sec.

m/sec.

Free-fall

75.2

22.9

Main parachute

-

-

Post-flight analysis and comments:

A good video of the entire flight was taken with the hand-held camera. A tripod mounted camera, aiming upward and situated a short distance from the pad, nicely captured lift-off from a different perspective. The on-board video footage was excellent. It was noted that the rocket exhibited minimal roll (spin) during ascent.

Post-flight examination confirmed that the rocket suffered no significant damage.

The reason for the chute failing to deploy was due to the Raven shutting down anomalously at the 22 second mark of the flight. This anomaly was very similar to that which occurred on the previous Zeta flight. Physical examination of the Raven found nothing unusual. The Raven data indicated a sharp rise in circuit board temperature beginning at the 17 second mark. This suggests one of the board components may be faulty.

The new xylitol smoke charge (and new igniter) performed very well.