Since Space is No Place to Change a Fuse, Reliability is a Must

Posted on Feb 16, 2017

SCHURTER showcases its new High-Current Space Fuse (HCSF) for space applications requiring fuse performance at higher rated currents. The HCSF is rated from 5 to 15A @ 125VDC, with a high breaking capacity of 1,000A. The new fuse is a logical extension to the original space fuse type, MGA-S, which provides lower current ratings up to 3.5A @ 125VDC. Both fuses are the result of successful development collaboration between the European Space Agency (ESA) and SCHURTER.

In general, fuses serve as overcurrent protectors in electrical circuits. In the event of fault (such as short-circuit), the function of the fuse is to ensure that a device apparatus or circuit is disconnected from the power supply in a reliable and controlled manner.

The fuse technology used widely today is not able to fulfill the requirements for long-term reliability in space satellites often with a lifetime of 20 to 30 years. This is mainly due to thermal cycles, which produce what is known as the aging phenomenon.

The difference between a fuse for space and a standard-use fuse lies in the differences in construction and testing: in the case of a fuse for space, every single component is extensively tested by means of a burn-in procedure to qualify its correct function.

Components that are used in space must possess the following properties:

  • Hermetically tight and robust construction such that with a disconnection no arc or gases can escape
  • Consistent minimum and maximum pre-arcing times with overcurrents independent from the mode of operation (e.g. in a vacuum)
  • Exacting precision of overcurrent disconnection at rated voltage
  • Stable de-rating curve of the component at higher ambient temperatures
  • High durability against mechanical vibration and shock

In 2004, SCHURTER cooperated with the European Space Agency to manufacture a fuse suitable for space applications. The subsequent research and development was realized in 2008 with the MGA-S being the first ESA-qualified fuse. The MGA-S has had a remarkable life in space projects since then, and continues to be widely used in space applications rated 0.14 to 3.5A @ 125VDC. Demand for higher current ratings brought about the second phase of cooperation between SCHURTER and the ESA in 2010, in which a solution for the protection of rated currents up to 15A was to be developed; this resulted in the HCSF up to 15A @ 125VDC.

Fuses in space applications are largely being used to protect redundant systems against short-circuits, or they can be used individually to switch off and allow backup systems to take over functions. Communication systems are specifically switched on and off, for example to send data packets at specific times. Each of these switching actions typically causes high pulse loads when connected, which have to be handled by the fuses without tripping and without affecting the long-term disconnect behavior of the fuse. The HCSF fuse is the highest-performing compact SMD solution, ideally suited for protection of power system architectures for satellites that operate up to 125VDC. With the MGA-S and now the high-current HCSF, these architectures can be completely protected.

Visit SCHURTER Inc. at Space Tech Expo 2017 in booth 4012

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