WORLD WIDE WEB -- Recently, there have been reports of hybrid rocket recovery failures using a accelerometer based system. Hybrid motors can produce significant vibration during operation. It is theorized that the dynamic accelerations associated with these vibrations can be integrated by the accelerometer based recovery system.

The magnitude of this condition can vary depending on the type of motor, vehicle mass and design as well as the flight profile. If this is in fact the case, an accelerometer-based device may not compute an apogee solution at the correct time. This could cause a late or no deploy situation.

Until recently this condition has only been reported with one particular brand of recovery system that is manufactured in Europe. The Hypertek M has been flown successfully on a domestic accelerometer system known as the Altacc without problems. Altaccs are routinely flown with J through L motors as well and Cesaroni Technology has not received any reports of recovery problems.

On June 24th, a Hypertek M powered rocket was flow with redundant Altacc systems and both systems failed to fire deployment charges. The systems were verified to be armed prior to launch. These units were also flown successfully in a different rocket with an Aerotech M1419 two days prior. It is important to point that the failed installation included an unusually long wiring harness on the remote arming boards. DaveyFire M28F fuse heads* were used in the recovery charges. These fuse heads have an all fire current of 1.0 amp @ 10ms vs. 0.4 amps @ 10ms for the type B fuse head**.

Since all power and arm/fire current is fed through the harness, contact switches and connectors, it is suspected that the firing output was de-rated to a level less than what would be required to fire a type F fuse head(s). When using any electric match, it is very important to fully understand their electrical characteristics before using them with your recovery and/or on-board ignition systems. In other words the redundant failure may not be an integration error, but may be traced to system installation.

Cesaroni Technology is working with the manufacturers of these devices to identify and resolve these issues. blacksky is replicating the extended harness/28F configuration for bench testing. CTI will be installing an Altacc on our dynamic shaker table and exposing it to various hybrid motor signatures for analysis. CTI has also initiated discussions with AED in this regard.

In the interim we recommend that any large hybrid powered rockets that are using accelerometer based electronics incorporate a backup device such as a timer, barometer or magnetometer etc. If there are any questions regarding backup implementation, please contact blacksky or Cesaroni Technology for details.

* Daveyfire M28F fuseheads are also marketed as HiRMI Mini and Standard electric matches by blacksky Corporation.
** Daveyfire M28B fuseheads are also marketed as HIRMI Sensitive electric matches by blacksky Corporation.