Design Wrap-up

At the onset of this design project, there were many possible design methods of deploying the 1 km2 solar array. The project began by brainstorming and developing several different ideas. Each member of the design team focused on a specific method of deploying the array. After developing each design method, the design group implemented a set of criteria to determine the feasibility of each design. The criteria consisted of material selection, configuration, analysis, and verification testing. By evaluating the criteria for each design consideration, the group concluded the inflatable design would best meet the criteria that was established.

The inflatable design met almost all the criteria that the group incorporated. As was mentioned earlier, the inflatable needed the fewest amount of launches. The number of launches required was one of the major criteria. The minimum number of launches keeps the cost of the structure a minimum.

The inflatable design also offered a sufficient amount of structural support. Finite element analysis was performed on the structure to determine the maximum stresses acting on the elements of the structure. The support of the inflatable varies with the pressure of the air inside the inflatable structures.

The inflatable design would also require no assembly or construction in space. Due to the inaccessibility of the solar power satellite in a GEO, minimal assembly is a major concern.

The reliability of the inflatable design would depend on the strength of the material used for the inflatable structures. A puncture in one of the inflatable tubes could prove to be disastrous. However, choosing a Kevlar structure should resist punctures by airborne debris.

Finally, the criteria of maintenance was considered. Only a minimum amount of maintenance must be provided for the inflatable structures. This maintenance would include sealing leaks and replenishing gases that might be leak through the material over time. This maintenance could be accomplished by initially attaching extra gas canisters to the structure which could be automatically dispersed when needed.

Overall, the inflatable design was considered to be the most feasible method of deploying a one km2 solar array in a geosychronous Earth orbit.

Future Work

The design group has many factors to considered and expanded upon in the future. These future considerations include the usage of foams or chemicals and possible shield aspects of silicon aerogel.

One important consideration is the possibility of utilizing sealing foams and/or chemicals which react to the design material. These foams or chemicals would replace the gas used to deploy the structure. By replacing the gases, the structure will be more rigid and less vulnerable to punctures. A foam could be used to deploy the structure. This foam would be very expandable so it could be put in a one central location and expand throughout the entire structure. The foam would then harden and make the inflatable a more rigid structure. Another thought has been to line the inflatable structures with some type of chemical that would react with the gas when the structure was being inflated. This reaction would cause the material to harden giving the same effect as the proposed foam.

Another future concept which shall be considered is the possible uses of silicon aerogel. Silicon aerogel is a wispy matrix of silicon. It consists of 1% silicon and 99% air. Aerogel is developed by slowly drying silicon gel with alcohol until only the framework of the silicon is remaining. Due to its extremely low density, aerogels are very lightweight. Aerogels are highly compactable and are powerful insulators.

Figure 10: Aerogel as Insulator

A future design adaptation is the use of an aerogel as an insulator. Figure shows a flower unaffected by a flame a quarter of an inch away. Thus, the silicon aerogel could be used to insulate important electrical and mechanical components from the harsh temperature variations of space.

Another design concept for the aerogel is as a shield to prevent against micrometeroid collisions which could puncture the structure. The aerogel could be placed around the inflatable tubes to prevent micrometeroids from puncturing the structure. Current space designs incorporate aerogels in this fashion. A spacecraft scheduled for launch in February 1999 uses silicon aerogel to catch micron sized particles traveling at 20 to 30 times the speed of bullets. The Stardust spacecraft will fly into the Comet Wild-2. Aerogel will then collect comet dust in its matrix and return it to Earth for analyzation.12

Group dynamics and division of labor

When the design group began this project, the members knew there was an endless amount of information for to obtain. Many resources were utilized to obtained as much information as possible so the group would not end up reinventing the wheel. First, the group broke up the collection of information into parts. Roger and Lindsay began collecting information in the library and looking through government documents while Joseph and Eric gathered information from the Internet.

After the group had gathered a substantial amount of information, the group then divided up the project into researching different designs. For instance, Eric investigated the centripetal design, Joseph looked into the Shape Memory Alloys, Lindsay researched the inflatable design, and Roger experimented with the expandable truss design.

Once the inflatable design was chosen, the group broke the design up further. Eric found gases that would be possible to use in the space environment, Joseph devised a backbone design for the array, Lindsay investigated possibility of micrometeorite impact, while Roger located materials to fabricate the structure. The model inflatable structure was then constructed by all the team members.