Flight day 5 - stability investigation
21.11.2009 (11:30 - 13:00)
Weather conditions: partly sunny, 13°C, light winds
During the last launches we observed the tendency of
Ia to fly in a slight arc. Always in the same direction. We
blamed slight instability for this behaviour and scheduled two launches
for investigating it.
#1: This was the reference launch with Antares
Ia, 1000 ml
of water and a pressure of 9 bar.
At 8 bar the nozzle sprang a leak so we launched ad hoc. Unfortunately
the camera did not work and we didn't get any footage of that launch.
The flight was similar to the ones last week: a slight arc to the west.
The flight duration was 26.5 seconds. Antares Ia touched the
ground approx 25 meters west of the launcher. Recorded
altitude was 86.6 meters.
Altimeter data of launch #1. Servo activity can be
easily detected by a dip in the recorded on board voltage.
#2: In order to make Antares more stable we
added much bigger fins. Still 1000 ml of water and a pressure
of 9 bar were used.
Just before launch we noticed that the trigger mechanism didn't work. A
little steel ring was broken. We decided to fix the
problem without de-pressurizing the rocket. This was only possible
because we didn't have to touch pressurized parts.
Antares Ib was aligned to the east but went to the west when
was released from the launcher. The flight was pretty high
this time. Ejection of the parachute was clearly visible but it failed
deploy. The flight time was approx.10 seconds. Antares Ib crashed into
ground 25 meters west of the launcher. Recorded altitude was
Altimeter data of launch #2. It is not totally
clear why recording stopped before the impact. Probably the write cycle
of the last values could not be completed before the voltage broke down.
Antares Ib after
crashdown. The parachute had been ejected but failed to open. During
descent it was visible as a small yellow ball flying alongside with the
The parachute failed to open because one
cord looped around the others when packing the parachute.
section had been completely destroyed. There was no chance for the thin
plastic to withstand an impact with a speed of more than 30 m/s.
and altimeter survived....
Since there were shorts on the PCB of the
deployment timer the servo was still running when the recovery
crew arrived at the
survived with minor damage. Some components were bent some lines on
the PCB were broken. The reed switch was broken too (front corner on
The direction Anteres is flying to is very reproducible (4 launches in
Very big fins do not change this tendency which might indicate that it
is not a stability issue.
The simulated height was again lower than the actual height. This is
most likely due to the poor calibration of the pressure gauge.
Further investigate the root cause of the not optimal
trajectory of Antares
Calibrate the pressure gauge