FOIA: Design of Equipment for Lunar Dust Removal

LUNAR_DUST_REMOVAL.pdf
Design of Equipment for Lunar Dust Removal
The report "Design of Equipment for Lunar Dust Removal" considers five designs for lunar dust removal equipment. The Apollo missions demonstrated the need for dust removal in the lunar environment.
Document date: 1991-05-01
Department: Mechanical Engineering Dept., University of Texas
Author: Lacy Belden, Kevin Cowan, Hank Kleespies, Ryan Ratliff, Oniell Shah, Keven Shelburne
Document type: report
pages: 92


Archivist's Notes: Fair quality document. Many hand written pages of calculations.

ABSTRACT
NASA has a long range goal of constructing a fully equipped, manned lunar base on the near side of the moon by the year 2015.
During the Apollo missions, lunar dust coated and fouled equipment surfaces and
mechanisms exposed to the lunar environment.
In addition, the atmosphere and internal surfaces of the lunar excursion module were contaminated by lunar dust which was brought in on articles passed through the airlock.
Consequently, the need exists for a device or appliance to remove lunar dust from equipment and finished surfaces. Five concepts were investigated to determine their effectiveness in removing lunar dust from surfaces of material objects used outside of the proposed lunar habitat. Additionally, several concepts were investigated for preventing the accumulation of lunar dust on mechanisms and finished surfaces.
The character of the dust and the lunar environment present unique challenges for the removal of contamination from exposed surfaces. In addition to a study of lunar dust adhesion properties, the project examines the use of various energy domains for removing the dust from exposed
surfaces. Also, prevention alternatives are examined for systems exposed to lunar dust.
A concept utilizing a pressurized gas is presented for dust removal outside of an atmospherically controlled environment. The concept consists of a small astronaut/robotic compatible device which removes dust from contaminated surfaces by a small burst of gas.

INTRODUCTION
The National Aeronautics and Space Administration conducted several exploratory missions to the moon during the period from 1969 through 1973. These missions, known as the Apollo program, resulted in the accumulation of an enormous amount of data pertaining to the
composition and geology of Earth's only natural satellite. During the course of these information gathering missions, the astronauts observed that the layer of dust covering the surface of the moon exhibited a high affinity for material objects.
Items such as the space suits, hand tools, optical equipment and mechanical equipment with moving parts were representative of the objects the lunar dust adhered to quite readily.
This layer of material, known as the lunar regolith, produced numerous unforeseen problems during the Apollo missions. Most notably, the dust impaired the proper operation of seals and lubricants used on various mechanisms and also accumulated heavily on exposed optical surfaces. In addition, the atmosphere and internal surfaces of the lunar excursion module were contaminated by lunar dust which was brought in on articles passed through the airlock.

1.1 Project Requirements:
Three main requirements governed this project:
1. Characterize the use of various energy domains for achieving the aforementioned goals in a one-sixth gravity, zero atmosphere environment.
2. Design a device or system which will be capable of removing lunar dust from optical surfaces without altering the surface finish.
3. Propose methods of preventing lunar dust from accumulating on finished surfaces.

1,2 Design Specifications:
A detailed list of the design specifications for this project is given in Appendix 1. The following section on the lunar environment details some of the important aspects pertaining to this project.

1,3 Lunar Environment:
The lunar environment will present unique circumstances and constraints that the final design solution must satisfy to achieve its intended function.
The primary objective of the project is to design a device for removing lunar dust from optical surfaces in the harsh lunar environment.
Therefore, it will be necessary to ascertain the characteristics with which the device must contend. The following information provides a description of the lunar environmental aspects which must be considered for designing dust removal equipment.

1.3.1 Temperature:
The temperature on the lunar surface varies over a wide range of values.
Daytime temperatures, which occur when the sun's rays are directly incident on the lunar surface, approach 384 K (232 °F) in the equatorial regions of the moon. Lunar night temperatures are as low as 102 K (-276°F). Temperature extremes on the order of 44 K (- 380 ° F ) are possible in the permanently shadowed areas near the lunar poles [41]. Problems commonly associated with high temperatures of the lunar day include severe outgassing of materials and lubricants and large strains due to thermal gradients which exist between sunlit and shaded sides of equipment [41]. Outgassing occurs when the temperature of a material object is high enough to produce evaporation of some of the molecules. This promotes rapid degradation of the material characteristics.

1.3.2 Vacuum:
Since the moon is absent of any significant atmosphere, pressure generally ranges from 10 -6 to 10 "10 Pascals, which is a near perfect vacuum [41]. The main problems associated with the lunar vacuum are similar to those previously mentioned with high temperatures, namely outgassing. Outgassing occurs because of either extremely high temperatures or very low pressures. Vacuum conditions destroy surface films which are normally present on physical objects in a terrestrial environment [41]. Surface films on material objects are due to gases, vapors and oxides present in the Earth's atmosphere. Since the moon is void of an atmosphere these surface films do not exist.

1.3.3 Gravity:
Gravity varies in magnitude over the entire surface of the moon.


1.3.4 Micrometeorites:
Micrometeorites are high velocity, low mass, microscopic cosmic particles which collide with material objects present in the lunar environment.

1.3.5 Lunar Regolith:
The surface of the moon is covered with a layer of meteorite generated debris known as lunar regolith. The regolith consists of a mixture of poorly sorted fragmental debris that ranges in size from very small particles to large rocks 0.8 meters in diameter.

1.3.6 Summary:
The lunar environment presents many challenges and obstacles which must be addressed in designing equipment for lunar dust removal. Device configuration, sealing mechanisms, and material selection are all of great importance to the durability and effectiveness of the equipment. Attention to detail must not be sacrificed for the sake of simplicity in the final analysis. A feasible working solution which satisfies the aforementioned constraints is presented later in this report

2,0 LUNAR DUST CHARACTERISTICS
The characterization of the lunar dust is the first step in the search for the solution to the dust adhesion problem. The energy required to break the adhesive bond of the dust to various surfaces is dependent on the dust properties as well as those of the surfaces to which the dust adheres.

3,0 ALTERNATIVE DESIGNS

3,1 Prevention
All support equipment for moon base which has the possibility of being exposed to the lunar environment, directly or indirectly, must consider the existence of the lunar dust in its design. Although removal may not be required in some cases, the cleaning task will play a major role
in the allocation of crew time and equipment maintenance if prevention measures are not taken.

3.1.2 Prevention Alternatives
Prevention alternatives exist in both hardware and operation design for all systems exposed to the lunar dust. Areas of particular interest are:
• Large surface areas (solar arrays, thermal radiators)
• Optical Equipment (windows, lenses, mirrors)
• Extravehicular Mobility Unit (spacesuit, portable life support)
• Mechanical Systems (lunar rovers, robotics)
• Interfaces (tools, connectors)

3.1.2.1 Large Surface Areas
Large areas such as solar arrays and thermal radiators present a
large and possibly critical problem for lunar dust removal.


3.1.2.2 Optical Surfaces
Surfaces such as mirrors, windows, and lenses pose a unique
problem for lunar dust removal due to the delicate surface finish which
must be preserved.

3.1.2.3 Extravehicular Mobility Unit (EMU)
The EMU consists of the spacesuit, portable life support system, and
any associated support equipment. Primarily, the cleaning difficulty of the
EMU is determined by the contamination requirements of the lunar habitat.
This results from the need for the astronaut and any associated equipment
to pass through the airlock.

3.1.2.4 Mechanical Systems
A variety of mechanical systems will be exposed to the lunar dust
environment. Equipment such as manned and autonomous lunar rovers
and robotic systems will present the difficulty of keeping lunar dust from
abrading critical moving parts. Fortunately, mechanical systems have been
tested in previous lunar experience; for instance, the Apollo lunar rover.

3.1.2.5 Interfaces
A primary source of mechanical interfaces is derived from the
maintenance of systems outside the lunar habitat.

3.1.3 Prevention of Dust Accumulation on Lenses
In this section, a concept for preventing dust accumulation on the
surface of lenses is explored. The concept is based on the lens cleaning
problem associated with cameras and vision systems. Two of the ideas
from the previous section discussing the prevention of dust on lenses are
used; the automated iris and sacrificial surfaces.

3.1.3.1 Operation
The system is proposed to operate either autonomously, by
crewmember at a control station, or by an astronaut conducting an EVA.

3.1.3.2 Autonomous Contamination Detection
Contamination detection for lenses and optical surfaces is an area of
intensive study for missions such as the Hubble Space Telescope and Space
Station.

3.1.3.3 Maintenance
System maintenance is performed by direct removal and replacement
of the dust prevention cartridge.

3.1.4 Prevention Summary
In many cases, lunar operations may require the use of
contamination prevention; however, the use of contamination prevention
on optical lenses has some distinct disadvantages. Primarily these are,
added weight and system complexity, as well as a probable reduction in
optical properties.

3,2 Removal
3.2.1 Electrostatic Solutions
3.2.1.1 Transportation of Dust by Electrostatics

The following has been taken from pdf. page 24 - 27 .... please read the complete pages if interested in this topic ... no conspiracy though


There are many theories that explain the transportation of dust
particles, but the transportation or erosion of dust by electrostatics seems to explain it best and satisfies all conditions. Erosion is assumed to be carried out in two step liberation of the particle in the transportation phase and actual transportation of the particles by the transportation mechanism.
Initially, the particles are not readily moved but when the particles
are disturbed then they can be easily transported by the transportation
mechanism. Only a small amount of particles are put in the transportation
phase to be carried away; this mechanism of carrying only few dust
particles is best explained by the electrostatic theory.

Many actions are considered responsible for the transportation of
material from the lunar surface such as thermal variations,radiation
pressure, forces arising from traces of gas and cycles of evaporation and
condensation; but all these are considered inferior and unimportant when
electrostatic phenomena is explained.
The transported dust is small in size because of degradation by
meteoritic impact. The dust is also characterised by low thermal
conductivity and low volumetric specific heat.
Light, X-ray radiations and particle bombardment from the sun all
cause emission of secondary electrons on the surface.
The emitted electrons form a thin layer near the lunar surface and are referred to as a plasma sheath. This sheath is carded away to the dark side of moon by solar wind thus forming a potential difference on the lunar surface between the sunlit and dark side.
There are two reasons for differential charging of the dust particles.
First, size variations within the particles result in varying charges in the
dust due to emission of electrons from the outermost orbit. This sets up
strong electric fields and causes dust movement. When bombarded with
electrons of sufficient energy in the form of radiation, solar radiation, the
outermost orbit of an atom in an insulator can be removed, thus making the atom positively charged. When many atoms give out electrons from the outermost orbit the body overall becomes positively charged.
Similarly when different particles on the lunar surface, in the same vicinity, emit varying numbers of electrons, the particles have different charges. A typical value of the energy to remove electron from the outermost orbit is about 300V. This is one of the reasons for differential charging. This electron emission sets up differential charges on the individual dust particles.

[edit on 16-12-2007 by frozen_snowman]

3.2.1.2 Force Analysis of Dust Particles
Lunar soil emits photoelectrons when the soil is exposed to solar
radiation. The dust particles will be levitated only when the electrostatic
force exceeds the gravitational force of attraction between lunar dust and
soil.

3.2.1.3 Lunar Magnetism
Strong magnetic fields are uncommon on the moon. The magnetic
field strength on the moon is very low, but samples were found which
show that some remnant magnetism does exist.

3.2.1.4 Conclusions and Further Studies
From the analysis, it can be concluded that an electrostatic device is
not feasible with the data that is available.

3.2.2.1 Foams and Gels
The first idea considered here is the use of a chemical foaming
solution to lift dust particles from an optical surface. Once the dust is
suspended in the foaming solution, it could be removed by blowing the
foam from the surface.

3.2.2.2 Liquid Solutions
Two basic ideas for the removal of lunar dust were developed in the
liquid domain. The first was a liquid rinse. A liquid would be sprayed
over the surface to be cleaned, thus breaking the dust adhesion forces

3.2.2.3 Gas Solutions
Considering the problems involved with a liquid alternative, some
gas solutions were considered. The cleaning method consists of blowing a
compressed gas over the optical surface. This is similar to the liquid rinse
in that the thrust of the gas will overcome the adhesive forces of the dust
on the optical surface.

3,3 Alternative Design Conclusions
From the inspected alternatives, a fluid solution was chosen for
detailed investigation. Although prevention must be an integral part of the
design of lunar equipment, it does not remove the requirement for a lunar
dust removal system. Further, mechanical cleaning alternatives such as the
dust brush are inadequate due to the probable damage of the optical surface
during cleaning. Electrostatics appear to be feasible yet are not practical
due to the large amount of power required, large system mass, and possible
safety problems.

PDF pages 32 to 52 encompasses the Design Solutions, Material, Operation and so on ….

We find the OVERALL CONCLUSIONS AND RECOMMENDATIONS on pdf. page 52:

This device was designed to clean delicate optical surfaces.
However, upon design completion, it appears that the gas apparatus can be used to clean other objects.
The gas cleaning device also has other possible uses.
Since carbon dioxide is an inert gas and the device operates at a relatively low thrust, it could be used as a fire extinguisher. Another possibility involves the storage tank. It could be disconnected from the handle and used to transport gases from the lunar habitat to remote sites.
Also, two analyses concerning the tank need to be considered: fatigue
and thermal. When the tank is in the lunar habitat, it is at approximately
atmospheric pressure. As it is brought into the lunar environment, the low
pressure induces a stress in the tank. Over time, this cyclic stress might
cause fatigue damage to the tank. Additionally, there are stresses in the
tank due to adverse thermal effects.
A final consideration is the build-up of a gas atmosphere on the
moon (suggested earlier). The gas cleaning device disperse only small
amounts of gas during each use. Considering the size of the moon in
relation to this, it does not appear to present a problem. However, this
concept should be remembered when designing anything for use on the
lunar surface.
A possible disadvantage of the device lies in the incident - refraction
angles discussed earlier.
Another disadvantage of the device is related to dust suspension. The
gas lifts the dust from optical surfaces and suspends it in the lunar
environment. Some of this spaceborne dust could land on the cleaned
surface. This problem will be more severe on horizontally mounted
surfaces than on vertical surfaces. A possible solution to this problem
would be to attach a flexible extension to the nozzle end. This extension
would fit around the surface to be cleaned; thus channeling the gas - dust
mixture away from the cleaned surface.

- The (happy) end-