Washing Clothes on the Moon

The lunar settlement will be fundamentally different from the space stations because it must be a sustainable habitat in which consumables must be very limited.  One of the new modules that NASA will be using is a fully functional washer.  Until this point, NASA has never implemented a washing system of any kind for their astronauts.  Currently, when an astronaut’s clothes are deemed too smelly and/or dirty, they are used as gym clothes.  After a use in the gym, the clothes are placed on a shuttle back to earth where they are washed.  This method will not be feasible of dealing with soiled clothes in a lunar settlement, where duration of stay will be longer and transits back and forth will be less frequent.  NASA has decided that it will be cheaper to have a washing machine in the lunar settlement rather than ship dirty laundry back to earth.

 (Photo from: Wendorf, J. H. (1972). U.S. Patent No. 3805563. Washington, DC: U.S. Patent and Trademark Office. &   Roaf, S. D. (1995). U.S. Patent No. 5457969. Washington, DC: U.S. Patent and Trademark Office.)


Team NKD has decided to use several different design methodologies taught at UT to analyze how standard washers work in order to fully understand the type of project we're taking on. These methodologies include using a Black Box Model, Function Structure, Activity Diagram, and a Force Flow Diagram. A Black Box Model is isolates the types of materials going in and out of a machine. It is used to isolate different groups of materials that must be included in a redesign, along with isolate materials that aren't so important. A Function Structure traces all of the forces, electrical signals, and materials that travel through an object, in this case, a washing machine. This differs from the black box because it is a a full map of what is included in a washing machine and how parts interact with each other. An Activity Diagram maps out the activities performed to run the machine. Finally, the Force Flow Diagram maps out the force flow on different mechanical and electrical members in the machine. This is done to reevaluate over constrained parts, and to combined parts.

Black Box Model

The black box model  was used to define the type of materials that need to enter and leave a washing machine.  While our ultimate design may not use buzzers or sensors to tell if the tasks are completed, it’s important to recognize the need for some sort of signal.  Also, no matter the washer’s design, it will need to accept the same inputs and produce the same outputs.

Function Structure and Force Flow Diagram

Using the black box model, the team mapped the energy, material, and signal flow through the washer in a function structure diagram.  Certain relationships were discovered when this was completed. For example, the isolation of three main functions of the washer: clean, rinse, and dry.  All materials traveling through the system must be placed in the basket (‘store’ as seen on the function structure), then mixed and separated.  This process is repeated several times before the dirt and bacteria have been separated from the clothes.  Finally, the clothes are spun dry and removed from the system, with some water remaining. 

Activity Diagram

  An activity diagram outlined the actions a user would perform when using a typical horizontal-axis washer.  By laying out the steps used in washing clothes, the team was able to understand the different actions that will be required to operate a washing machine.  The team used this information when going through the concept generation phase.

Force Flow Diagram

The force flow diagram showed us how important the basket and casing are to the washing system and also helped the NKD Design Team to understand how a horizontal-axis washer works.  This diagram also helped the team identify the different types of systems that must be involved in the washer and how the systems are currently integrated.