Failure of the Ball-Lock Mechanism on the NanoRacks CubeSat Deployer  Michael Lewis* and Conor Brown ** Abstract  The NanoRacks CubeSat Deployer (NRCSD) is a system that is used to deploy small-form-factor satellites  off of the International Space Station. Deployment occurs by commanding the activation of each of eight  deployers that comprise the system. On early iterations of the NRCSD, commanding initiated the release  of a ball-lock mechanism, which in turn released the doors and allowed deployment of the satellites. Multiple  failures were experienced on the Orb-1 and Orb-2 NRCSD missions. Failures on the Orb-1 mission were  attributed to an electronics/avionics issue and were overcome without loss of mission. Failures on the  Orb-2 mission were of a different nature; two deployers never deployed, even after multiple command  attempts. Two deployers had an inadvertent deployment after previously being commanded.   Post-mission analysis included a Fault Tree Analysis of the NRCSD system as well as all individual  components and mechanisms, including the ball-lock mechanism that is used to release the doors and  deploy the satellites. The mechanisms were assessed by NASA’s Mechanical Systems Working Group,  NASA’s Payload Safety Review Panel, JAXA engineering, and NanoRacks engineering. The conclusions  of the Fault Tree Analysis and assessment showed that the cause of failure was excessive loading of the  ball-lock mechanism; screws that were intended to preload the system were excessively torqued, which  caused the ball-lock mechanism to seize. An operational procedure was implemented to remove the  preload screws on-orbit. Once the screws were removed, all subsequent activations of the ball-lock  mechanism were successful.  Introduction  The NanoRacks CubeSat Deployer (NRCSD) is a mechanism that is used to deploy small-form-factor  satellites off of the International Space Station (ISS). The system consists of individual deployers that are  bolted together in groups of four to form a ‘quad pack’. A mission can consist of up to two quad packs (eight  total deployers) mounted to the Multi-Purpose External Platform (MPEP), which is in turn mounted to the  Japanese Experiment Module (JEM) airlock slide table (Figure 1). The Launch Command Multiplexer (LCM)  and all associated cabling is also mounted to the MPEP, and the entire assembly is covered by Multi-Layer  Insulation blanketing. The MPEP is transferred outside of the ISS by the JEM airlock, and then grappled by  the JEM Remote Manipulator System (RMS); the JEM RMS then maneuvers the MPEP and NRCSD into  the deploy position. Commanding is done from the ground, coordinated by the Payload Operations  Integration Center at Marshall Space Flight Center and the Flight Operations Team at NanoRacks, and is  executed by Japanese flight controllers at the JAXA agency’s facility in Tsukuba, Japan.  The NRCSD was developed in response to a high customer demand for satellite deployment. The ISS has  had the capability to deploy CubeSats since 2012, when the Japanese Small Satellite Orbital Deployer  (JSSOD) was first used. The first deployments, which included a satellite flown by NanoRacks, served as  a pathfinder and revealed the commercial demand for ISS satellite deployment. The JSSOD, which is still  in operation to date, has been a reliable deployment mechanism, but is restricted by the limited capacity of  6U of satellites (by comparison the NRCSD has a capacity of 48U).  *NanoRacks, LLC, Webster, TX Proceedings of the 44th Aerospace Mechanisms Symposium, NASA Glenn Research Center, May 16-18, 2018 NASA/CP—2018-219887 351