Test and evaluation of bubble memories

Since January, 1977, a test and evaluation program has been conducted at the Jet Propulsion Laboratory to determine the potential usefulness of bubble memories for spacecraft and commercial applications. The memories evaluated were commercially available units which are similar to a NASA-developed memory cell. It is planned to also test other memories as they become available from manufacturers. Objectives of the test program were to determine: (1) Long-term stability of memory performance. (2) Margins of power supply voltages and bias field. (3) Data pattern sensitivity. (4) Memory performance over specified temperature range. (5) Memory performance in vacuum. The memory was found to operate reliably over long periods of time. No aging or wear-out was detected during one year of operation. Margins of power supply voltages and bias field were acceptable, but quite narrow at the low end of the temperature range. In addition, the error rate was found to be strongly data-pattern sensitive. The error rate of one memory improved considerably if it was operated continuously for long periods of time. The other memory did not show this characteristic. With the evaluated memories comparing favorably with other mass memories, such as tape recorders, bubble memories are now considered viable candidates for future spacecraft applications.