The Gelation of Sols: Applied Microgravity Research (GOSAMR) payload is a middeck materials processing experiment that will investigate the influence of microgravity on the processing of gelled sols--dispersions of solid particles in a liquid often referred to as colloids--which are used in the production of advanced ceramics materials. Stoke's law predicts that there will be more settling of the denser and larger-sized particulates in Earth's gravity as compared to the differentiation that should occur in a microgravity environment.

The GOSAMR experiment will attempt to form precursors for advanced ceramic materials by using chemical gelation (disrupting the stability of a sol and forming a semi-solid gel). These precursor gels will be returned to 3M Science Research Laboratories, dried, and fired to temperatures ranging from 900 to 2,900 degrees F to complete the fabrication of the ceramic composites. These composites will then be evaluated to determine if processing in space resulted in better structural uniformity and superior physical properties.

On STS-93, 50-100 samples (5 cc each) will be generated by varying the particle sizes and loadings, the length of gelation times, and the sol sizes. The chemical components will consist of either colloidal silica sols doped with diamond particles or colloidal alumina sols doped with zirconia particulates. Both sols will also be mixed with a gelling agent of aqueous ammonium acetate.

About a month before launch, the GOSAMR payload is prepacked into a middeck stowage locker and surrounded with half an inch of isolator material. The experiment contains an internal battery source and uses no power from the shuttle orbiter. The payload is designed to operate at ambient cabin temperature and pressure to ensure scientific success of the experiment, maintaining temperatures above 40 degrees F and below 120 degrees F at all times.

The GOSAMR container consists of a back cover, five identical and independent apparatus modules holding ten mixing systems, and a front cover. The modules and covers comprise a common sealed apparatus container that provides an outermost level of chemical containment. The front cover contains two ambient temperature-logging devices, two purge ports for venting and backfilling the container with inert gas, and the electrical feedthrough between the sealed apparatus and the control housing. The control housing at the front of the payload contains power switches for payload activation, indicator lights for payload status, and a test connector used during ground-based checkout. Once the payload is installed in the locker, the control housing will be the only portion of the payload accessible to the flight crew.

Each of GOSAMR's five modules has two mixing systems with eight double syringes (5 cc each) containing one of the two chemical components. Prior to on-orbit activation, the two components will be kept isolated from each other by a seal between the syringe couplers. The coupled syringes in each assembly will contain a gelling agent (either aqueous ammonium acetate or nitric acid) in one syringe and one of the two chemical components in the other.

Once on orbit, a crew member will sequentially activate the five power switches on the control housing. When the payload is activated, a pilot light for each module will be illuminated, indicating that mixing has begun and that the syringe-to-syringe seal has been broken. The sample mixing process for each system will last about 10 to 20 seconds; and once the mixing cycle is complete, an internal limit switch will automatically stop each mixing system.

The flight crew will monitor the experiment status by observing the control-housing indicator lights, which will be illuminated during the motor-driven mixing of each system. The pilot lights will be extinguished once the mixing is complete, and a crew member will deactivate each module. The payload will require no further crew interaction. However, physical changes in the samples will continue passively and unattended for a minimum of 24 hours in the microgravity environment. Total crew interaction will be less than 1 hour, and only during this period will the locker door be open.

After landing, the payload will be removed from the orbiter during normal destowage operations and resumed to 3M within 24 hours where postflight processing and analyses will be conducted on space- and ground-processed samples to ascertain the differences in physical structure and properties.