Welcome to the Sunday Paper Club. Every Sunday, this blog will offer an analysis of a paper on space habitation and other related topics. These are my opinions on a weekly scientific paper; basically, I read the paper and write down my thoughts while I read it. They are subject to my perspectives and believes. I am open to debate, so if any reader believes I have misinterpreted something in a paper, please point it out. I'm only a student and I'm still learning how to read these papers and interpret them. All quotes and ideas are from the paper, unless otherwise noted.
This week we are reviewing the paper Engineering, Design and Construction of Lunar Bases. I am using a new format based on the Lifehacker article Back to School: Keep an Academic Reading Journal.
Article Information
Title: Engineering, Design and Construction of Lunar Bases
Author(s): Haym Benaroya, Leonhard Bernold and Koon Meng Chua
Date: April 2002
Journal: Journal of Aerospace Engineering
Volume: 15
Issue: 2
Pages: 33-45
Article Overview
Building on the moon is harder than it looks. Traditional construction methods fail to be useful on the harsh surface. The moon’s soil clings to everything and binds moving parts (not even WD-40 can fix that). The temperature variances weaken structures. This paper is an index and summary of the top papers in lunar construction.
Key/Interesting Quotes
“On the lunar surface, numerous constraints,different from those for terrestrial structures, must be satisfied by all designs.” Page 1
“A post-Apollo evaluation of the need for a lunar base has been made (Lowman 1985) with the following reasons given for such a base: Advancing lunar science and astronomy; Stimulus to space technology and test bed for technologies required to place humans on Mars and beyond; Utilization of lunar resources; Establishment of U.S. presence; Stimulation of interest of young Americans in science and engineering; and Beginning of long-range program to ensure survival of species.” Page 1
“Scientific advantages of a polar location for a lunar base (Burke 1985) are that half the sky is continuously visible for astronomy from each pole and that cryogenic instruments can readily be operated there due to the fact that there are shaded regions in perpetual darkness.” Page 2
“Relationships between severe lunar temperature cycles and structural and material fatigue, a problem for exposed structures [need to be studied]” Page 2
“Factors of safety, originally developed to account for uncertainties in the Earth design and construction process, undoubtedly need adjustment for the lunar environment, either up or down, depending on one’s perspective and tolerance for risk [need to be studied]” Page 2
“Buckling, stiffening, and bracing requirements for lunar structures, which will be internally pressurized [need to be studied” Page 2
“…it appears that concurrent engineering will be a byword for lunar structural analysis, design, and erection. Concurrent engineering simultaneously considers system design, manufacturing, and construction, moving major items in the cycle to as early a stage as possible in order to anticipate potential problems. Here, another dimension is added to this definition. Given the extreme nature of the environment contemplated for the structure, concurrency must imply flexibility of design and construction.” Page 2
“…mass rather than weight-based criteria should be the approach of lunar structural engineers.” Page 2
“Newer work and development of nonlinear stress-strain models to describe the mechanics of the lunar regolith can be found in Johnson et al. (1995) and Johnson and Chua (1993)” Page 3
“In the likely situation that a layer of regolith (lunar soil) is placed atop the structure for shielding, the added weight would partially (in the range of 10–20%) balance the forces on the structure caused by internal pressurization” Page 3
“…during the times of low solar activity, the annual dose-equivalent for humans on the exposed lunar surface may be about 30 rem…” Page 3
“…the dose equivalent over an 11 year solar cycle is about 1,000 rem…” Page 3
“…It appears that at least 2.5 m of regolith cover would be required to keep the annual dose of radiation at 5 rem, which is the allowable level for radiation workers…” Page 3
“Construction in a vacuum has several problems. One would be the possibility of outgassing of oil, vapors, and lubricants from pneumatic systems.” Page 3
“The lunar surface has a layer of fine particles that are easily disturbed and placed into suspension. These particles cling to all surfaces” Page 3
“a device that is simple and conventional looking and has no moving parts is preferred [to those which are complex and have many moving parts in space]” Page 4
“Inflatable structural concepts for a lunar base are proposed (Broad 1989) as a means to simplify and speed up the process while lessening the costs.” Page 4-5
“A concept proposed by King et al. (1989) would use the liquid oxygen tank portions of the Space Shuttle external tank assembly for a basic lunar habitat…this idea, if proven economically feasible, may provide the most politically palatable path to the lunar surface, with the added advantage that many of the necessary technologies already exist and only need resurrection” (Page 5)
“Horiguchi et al. (1998) study simulated lunar cement.” Page 5
“In order to avoid the difficulties of mixing concrete on the lunar surface due to lack of water, Gracia and Casanova (1998)have suggested examining use of sulfur concrete because sulfur is readily available on the Moon.” Page 5
“Construction of a lunar base will at least partially rest on the capabilities of the Army Corps of Engineers.” Page 6
“‘In all human societies, the quality of life depends first on the physical infrastructure that provides the basic necessities such as shelter, water, waste disposal, and transportation,’ wrote Grigg (1988) Today, and especially for the lunar base, we have to add communication and power as part of the physical infrastructure.” Page 7
“…the regolith reaches the relative density of 90–100% below 30 cm.” Page 7
“Although the ejection of regolith would not be acceptable on the lunar surface, since the resulting dust would travel far, research showed that explosives buried deep enough would not create craters but loosen the soil very effectively.” Page 7
“Bernold (1994) showed that the compaction of lunar soil necessary for creating a stable road base would create unique problems. Preliminary research data indicated that the normal size distribution of soil particles would make it impossible to achieve needed density and strength using common methods of static or vibratory compaction.” Page 8
‘‘Lunar tramway systems can take advantage of the reduced gravity, which permits building wider spans and/or using smaller cable diameter for lifting and transporting heavy loads.” Page 8
“One of the main problems in robotic control of equipment is the time that signals need to travel through vacuum, atmosphere, or fiber-optic or other communication lines.” Page 9
Personal Response to the Paper
The idea that regolith has a density of 90%-100% below 30cm (about 11.8 inches) stunned me. A lot of the moon base ideas assume that we can build underground, I don’t think we can get through bedrock. On Earth, we blast, but this paper proves that is impractical because the debris produced would orbit the plant, at a low altitude, making the process dangerous. The paper mentions using a wire to loosen the soil, but it is still a difficult process.
It was strange though, I felt encouraged by readying this article despite its presentation of countless problems. It seems that every problem was addressed and those which still need work are neatly listed in an appendix at the back of the paper. This paper provides humanity with a checklist of topics that need to be covered before we can begin lunar settlement. Maybe I feel good about reading this article because it seems a massive task is broken down now.
Questions Raised by the Paper
What was the process that made the moon’s soil so dense?
The wire on a tramway placed on the moon could produce electricity because of the radiation, could this be a danger to occupants?
The article mentioned most excavation tools wouldn’t work in reduced gravity, I understand most of them, but why wouldn’t a backhoe work?
Assuming we could mix concrete on the moon, what happens to concrete that is outgassed?
What does the Army Corps of Engineers have to do with the moon base and can we use their budget in building it since the article states they will lead the effort?
