Launch to excellence


First flight test of DART vehicle

Posted: Sep 23, 2014
T-Minus DART test vehicle 01 in the launch tower
DART in launcher

On friday, September 19th, the T-Minus DART TV01 test vehicle was launched successfully at a military shooting range in the Netherlands.

The three objectives of this flight test were:

  • To demonstrate the capabilities for fitting small-scale electronic systems in the dart payload;
  • To test separation of booster and dart upon booster burnout;
  • To verify aerodynamic properties (mainly drag coefficient) of the vehicle-combination, the DART itself and the spent booster casing.
  • The test vehicle consisted of an aerodynamically representative airframe, equipped with a reduced-size rocket motor to limit the altitude, due to the launch field limitations.

    The dart payload was equipped with a data acquisition system with lateral acceleration and ambient pressure sensors, a GPS receiver, to increase the change of retrieving the DART after launch and a computer to control the flight events. The data of the sensors was stored on-board. The sensors and data acquisition system were housed in a separate payload capsule, which was ejected from the dart at apogee by means of a pyrotechnic charge. With data from these sensors, the flight path can be reconstructed and the aerodynamic properties of the vehicle derived. A small parachute was fitted in the dart as well, to slow the vehicle down and to reduce the loads on the electronic system on impact.

    T-Minus DART test vehicle 01 during its flight
    DART during flight

    The preparations for the launch went quite well, indicating that the system itself is easy to use. After the moment of ignition, the motor had a rapid thrust-up, as expected. During the motor burn, it was observed that the rocket oscillated somewhat around its trajectory, possibly because the booster section experienced some aero-elasticity. Separation between the booster and dart at motor burnout was observed. The booster had a stable re-entry all the way to the ground and impacted a little uprange of the predicted impact point, possibly because of energy bleedoff from the wobble during the ascent phase. The payload ejection trigger at apogee could be confirmed by audible reports. Because of the cloud cover, the dart could not be tracked visually. Unfortunately, no GPS data was received during the descent, the most likely reason for this is a lack of mobile phone coverage in the impact area (the GPS data were to be transmitted via the mobile phone network). The impact point was predicted by means of a numerical simulation, and a search party was organized to look for the dart around the predicted impact point. It was recovered, with a deployed parachute and flight train, in good shape. Both the primary and secondary deployment squibs were fired, which confirms that the flight computer functioned nominally

    Post flight analysis of the Dart showed that the mechanical structure is mostly intact. The only significant damage is a dent in the payload canister hull, possibly from impact with another part of the flight train during parachute deployment. All electronic systems were found to be in working order, and data was recovered from both the GPS tracker and the pressure and acceleration sensor package. The tracker had acquired a GPS fix, and the last location corresponded exactly with the point of impact. This means that indeed the most likely failure mode is impact in an area with poor cell phone coverage.

    In the coming weeks, we will analyze the flight in more detail, and hopefully find the reason for the wobble during the ascent. With the lessons learned during this test, we will further improve the design of the DART. In the next period, the focus will be mainly on development of the motor.
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