Analysis and studies have indicated that the planned International Space Station acceleration environment will not provide the low levels of acceleration that are specified to support certain microgravity experiment activities. These vibrations are caused by major component mechanical disturbers such as the solar and thermal radiator rotary joint mechanisms and control moment gyros, crew motion, and man/science equipment such as pumps and fans.

To meet the microgravity requirements, an active rack isolation design approach was developed which incorporates the Boeing Active Rack Isolation System (ARIS). A developmental version of the ARIS was flown on STS-79 to verify and quantify the performance of the system. The primary objective of flight testing was to collect response data, which showed ARIS functionality and characterizes ARIS performance. In order to measure the performance, the testing had to be conducted in a free-floating, microgravity environment.

The ARIS attenuates vibratory disturbances at selected user payload locations in support of the United States On-orbit Segment (USOS) requirements for microgravity environment. The ARIS is installed within an ISPR and its associated location within the SPACEHAB Double Module. Attenuation was achieved by imparting a reactive force between the ISPR and Double Module in response to sensed vibratory accelerations, thereby reducing disturbances to user payloads within the ISPR.

In addition to attenuation, the ARIS measures vibratory disturbances within the ISPR. The ARIS also receives vibratory disturbance measurements from off-board accelerometers attached to the SPACEHAB Double Module.

During the mission, the Space Shuttle Atlantis docked with the Russian Space Station Mir. This structural configuration is closer to the ISS configuration than the Shuttle alone and, consequently, provided an opportunity to measure isolation from low frequency structural vibrations. For comparison and ARIS system characterization, testing was conducted both prior to Mir docking and while docked.

The ETTF examines the influence of microgravity on the liquid phase sintering of metallic systems, which form either ideal solutions or alloy phases. Samples are loaded into ampoules which are installed in the furnace by the astronauts once in space. After a mission, the samples processed in the furnace during exposure to the microgravity environment of space are compared with samples produced on earth. The ETTF was one of a series of commercial microgravity science experiments flown on SPACEHAB Module missions under the Commercial Middeck Augmentation Module (CMAM) contract between NASA and SPACEHAB, Inc.

The ETTF was unpowered during launch and landing. The furnace was filled with argon at ambient pressure for launch. Once in space, the astronauts configure the furnace for operation. A serial converter unit (SCU) is connected to the front panel prior to activation. Activation requires an astronaut to switch power on from the EPSU, power up the computer and verify the furnace status. Given nominal status, the Translation Lock Assembly, which fixes the furnace in position during launch and landing, is removed and the first ampoule installed. The ETTF is vented to space and monitored to verify vacuum. A processing run is then initiated. During the run, periodic status checks by the astronauts and continuous checks by the ground crew are performed.

Four processing runs are performed: one prior to the Shuttle docking with Mir, two while docked, and one after the Shuttle separates from Mir. When a processing run is completed, an astronaut configures the furnace, either for the next run or for landing, as required. Following a given processing run, the furnace is pressurized to cabin ambient, the processed sample ampoule removed and stowed, a fresh sample ampoule installed and vacuum established in the furnace. If a delay greater than 60 minutes is scheduled between runs, the furnace is powered down.

A typical processing run requires approximately 45 minutes for activation, 18 hours run time, and 45 minutes for deactivation. Normally, after the furnace is activated by the crew, it is monitored from the ground and control adjustments will be sent from earth via the SCU. As a contingency backup, a PGSC can be connected to the front panel assembly to enable command inputs by the crew. The software for PGSC operation is contained on a single diskette which is stowed in the SPACEHAB Double Module and loaded by the crew, as required.

ETTF capabilities are distinguished by the extremely high operating temperature, multiple sample growth options, accuracy of temperature control, selectable translation rates, and efficient use of power, mass, and volume in the space flight environment.