In August 2004, Jackson and Tull was
tasked to design and build a protoflight Cryocooler Electronics (CCE) box for
the Alaska Cryocooler System (ACS) under the Raytheon Contract. The CCE effort
includes the design of the CCE box to drive a two-stage Reverse Turbo-Brayton
(RTB) Cryocooler being designed and developed by Creare. J&T will deliver
two sets of protoflight electronics to be used to test the engineering model (EM)
and flight model (FM) cryocoolers.
The design of the Cryocooler Electronics and cryocooler is strongly based
upon the NICMOS Cryocooler developed by J&T and Creare that is currently flying
on the Hubble Space Telescope (HST). The J&T design electronics will consist
of three rotating field inverters with duty cycle control voltage regulation.
One inverter will supply power to the compressor motor. The other two will absorb
power from the two turbo-alternators and regulate their speed. J&T will also
design a digital system controller that will interface to the electronics control,
and set the frequency and amplitude of the AC voltage waveforms for the three
inverters to achieve commanded speeds and power levels, and temperature control.
Control algorithms are expected to closely resemble those used in the NICMOS Electronics
Support Module (ESM) for the NICMOS cryocooler. J&T will also design and build
the signal conditioning electronics for telemetry used by the system controller,
and the D/A and A/D converters that support the system controller.
The overall development effort is expected to take almost 2 years with final
integration and test of the Cryocooler electronics box with the cryocooler being
conducted at Creare located in New Hampshire. The CCE was originally scoped as
a brassboard development effort and has growth to be protoflight development effort.
The purpose for this change in scope was for J&T to develop a design that
is as close to a flight design as possible to mitigate any potential risk with
the flight delivery schedule.
To date, J&T has completed a preliminary design and just recently conducted
an Advance Design Review that was held at the Raytheon facility in El Segundo,
California. J&T will conduct the Preliminary Design Review in Spring 2005
and deliver the first of two CCE boxes for integration and test in September 2005.