Terminal Velocity I
Terminal Velocity II's fin section during construction.

By Benjamin Wilkosz

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Disclaimer: all liability waved! The contents of this page is presented for informational purposes only. Do not try to recreate any experiments presented in this page. The NAVRO and the author of this article cannot assume responsibility for any use readers make of this information. In The Netherlands it is forbidden by law to own this type of propellant if you do not have an exemption of the "Wet Explosieven Civiel Gebruik" (WECG).

Based on its predecessor, the Terminal Velocity II was build to test the Avalon 8+ rocket motor in flight. After the failure of the Terminal Velocity I a new Avalon 8 with a higher Isp and impulse, the Avalon 8+, was designed and build. The glass fibre/carbon fibre fuselage of the TV II was very similar to that of the TV I. The electronics compartment contains only the most necessary electronics for its maiden flight: an R-DAS and two G-Switched TRAX-ART's. The two TRAX-ART's were used as a backup for the drogue chute, which should be deployed at apogee. This basic configuration was completed with a small transmitter to locate the TV II after landing. Once the TV II has completed its first flight successfully more onboard electronics, like a camera and GPS, are planned for future flights.

The flight of the TV II went according to plan. One small problem was the early deployment of the main chute. Since most of the flight happened above the clouds only the R-DAS could reveal a little more of the problem. Due to the strong wind on the launch day the tower was adjusted to a launch angle of 75 degrees. This resulted in an apogee speed of approximately 120 km/h. Since the nosecone was not equipped with electronics for this flight the planned locking system for the nosecone/main chute bay was not installed yet. Once the TV II appeared underneath the clouds after approximately 2.5 minutes of flight the whole configuration was hanging on the main chute. Since the ignition of the pyro-charge for the main chute could clearly be seen at the predefined altitude of 200m the early deployment could not be caused by a premature ignition. Thereby the abrupt deceleration of the drogue chute was considered to be the reason for the early deployment. However the R-DAS flight data revealed another story, see the altitude plot below. Only the drogue did unfold at apogee. The main chute was unfolded first 25 seconds later at an altitude of 1200 meter, still above or in the clouds. Because the black powder charge for the main chute was not equipped with a backup and the TRAX-ART cannot ignite anyway after more than 31 seconds into flight the only reason for the early deployment can be centrifugal force caused by the rotation of the fuselage during the decent on the drogue chute. Fortunately the TV II landed within visual range and was retrieved quickly. No major damage could be identified to the fuselage, motor, electronics or parachute system. The Avalon 8+ motor performed as planned, accelerating the TV II with 11 G to a top speed of 860km/h.

Next step is an expansion with an onboard video camera and the necessary locking system for the nosecone containing the camera. Parallel to this upgrade of the TV II a new Avalon with approximately 5700Ns impulse will be developed, the Avalon 9, which will be used for future flights of among others the TV II.

Benjamin Wilkosz

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