Systems engineering studies of lunar base construction

Many ingenious concepts have been proposed for lunar base construction, but few systematic studies exist which relate time-consistent lunar base construction technologies and the choice of lunar base approach with the long-term SEI objectives - i.e., lunar indigenous base construction and Mars Exploration equipment development. To fill this gap, CSC has taken a two-pronged approach. First, the Center undertook basic geotechnical investigations of lunar soil, fabrication of a scale prototype of a lunar construction crane, a multi-robot construction team laboratory experiment, and a preliminary design of lunar base structures. Second, during Jun. and Jul. 1991 two lunar base construction systems engineering studies were accomplished - a 'near term lunar base' study, and a 'far-term lunar base' study. The goals of these studies were to define the major lunar base construction research problems in consistent technology/construction frameworks, and to define design requirements for construction equipment such as a lunar crane and a regolith mover. The 'near-term lunar base' study examined three different construction concepts for a lunar base comprised of pre-fabricated, pre-tested, Space Station Freedom-type modules, which would be covered with regolith shielding. Concept A used a lunar crane for unloading and transportation; concept B, a winch and cart; and concept C, a walker to move the modules from the landing site to the base site and assemble them. To evaluate the merits of each approach, calculations were made of mass efficiency measure, source mass, reliability, far-term base mass, Mars base mass, and base assembly time. The model thus established was also used to define the requirements for crane speed and regolith mover m(sup 3)/sec rates. A major problem addressed is how to 'mine' the regolith and stack it over the habitats as shielding. To identify when the cost of using indigenous lunar materials to construct the base exceeds the cost of development and delivery of the equipment for processing lunar materials, a study of construction of a candidate sintered regolith 'far term lunar base' was undertaken. A technique was devised for casting slabs of sintered (basaltic) regolith and assembling these into a hemispherical (or geodesic) dome. The major problem occurs with the inner liner. At 14.7 psi and 20 percent oxygen internal atmosphere, the entire structure is in tension, even with the regolith load. Also, another study has indicated that at 14.7 psi major resupply of air will be needed because of leakage, and astronauts may have to engage in extensive pre-breathing and post-breathing for extravehicular activity (EVA) tasks, thus detracting from useful mission work time. An alternative is to operate part of the base at, say, 5 psi and 70 percent oxygen, or to equip the astronauts with hard suits at 8.3 psi or greater. All of these choices directly influence base design and construction techniques

Mixing in supersonic flow

Method for determining turbulent transport coefficient in supersonic flo

Optimal Alphabetic Ternary Trees

We give a new algorithm to construct optimal alphabetic ternary trees, where every internal node has at most three children. This algorithm generalizes the classic Hu-Tucker algorithm, though the overall computational complexity has yet to be determined

Optimality in multiple comparison procedures

When many (m) null hypotheses are tested with a single dataset, the control of the number of false rejections is often the principal consideration. Two popular controlling rates are the probability of making at least one false discovery (FWER) and the expected fraction of false discoveries among all rejections (FDR). Scaled multiple comparison error rates form a new family that bridges the gap between these two extremes. For example, the Scaled Expected Value (SEV) limits the number of false positives relative to an arbitrary increasing function of the number of rejections, that is, E(FP/s(R)). We discuss the problem of how to choose in practice which procedure to use, with elements of an optimality theory, by considering the number of false rejections FP separately from the number of correct rejections TP. Using this framework we will show how to choose an element in the new family mentioned above.Comment: arXiv admin note: text overlap with arXiv:1112.451

Coupled Chemistry-Emission Model for Atomic Oxygen Green and Red-doublet Emissions in Comet C/1996 B2 Hyakutake

The green (5577 \AA) and red-doublet (6300, 6364 \AA) lines are prompt emissions of metastable oxygen atoms in the $^1$S and $^1$D states, respectively, that have been observed in several comets. The value of intensity ratio of green to red-doublet (G/R ratio) of 0.1 has been used as a benchmark to identify the parent molecule of oxygen lines as H$_2$O. A coupled chemistry-emission model is developed to study the production and loss mechanisms of O($^1$S) and O($^1$D) atoms and the generation of red and green lines in the coma of C/1996 B2 Hyakutake. The G/R ratio depends not only on photochemistry, but also on the projected area observed for cometary coma, which is a function of the dimension of the slit used and geocentric distance of the comet. Calculations show that the contribution of photodissociation of H$_2$O to the green (red) line emission is 30 to 70% (60 to 90%), while CO$_2$ and CO are the next potential sources contributing 25 to 50% ($<$5%). The ratio of the photo-production rate of O($^1$S) to O($^1$D) would be around 0.03 ($\pm$ 0.01) if H$_2$O is the main source of oxygen lines, whereas it is $\sim$0.6 if the parent is CO$_2$. Our calculations suggest that the yield of O($^1$S) production in the photodissociation of H$_2$O cannot be larger than 1%. The model calculated radial brightness profiles of the red and green lines and G/R ratios are in good agreement with the observations made on comet Hyakutake in March 1996

A survey of robust statistics

We argue that robust statistics has multiple goals, which are not always aligned. Robust thinking grew out of data analysis and the realisation that empirical evidence is at times supported merely by one or a few observations. The paper examines the outgrowth from this criticism of the statistical method over the last few decade

Auf die Schiffe!

I argue that metaphors of water and fluidity are essential to both the content and form of Nietzsche’s work. In regards to the content, many important ideas such as a healthy response to the death of God and a philosophy of the future are, at their core, characterized by embracing fluidity. As for the form, just as Zarathustra tells us his teachings have become a river, Nietzsche’s work uses metaphor, aphorism, and poetic language to embody the qualities of dancing water. Consequently, it defies rigid interpretations that would turn it into a system and avoids falling prey to its own critique of calcification and ideology. As for questions of interpretation, the integrity of Nietzsche’s work is best preserved by affirming its fluid nature. Reading him is most authentically and best approached as one would engage with any other river, by swimming or navigating a craft down it and being carried towards the sea; a method carried out by engaging poetically with the metaphors that abound in the texts. In contrast, a flawed approach is to corral the river such that the water becomes still, or to freeze it into ice. These methods (which seek to arrive at a stable, permanent understanding) render analysis possible via the rational mind but turn the work into a pale simulacrum of itself

Least-absolute-deviations fits for generalized linear models

SUMMARY The fitting by quasi-likelihoods is based on Euclidean distance and thereby related to the least-squares norm. This paper examines the consequences of replacing the L2-norm by the L1-norm in the derivation of quasi-likelihoods. Since the least-absolute-deviations centre of a distribution is its median rather than its mean, the natural models for the L1-fitting involve medians. However, even if we model the mean response rather than the median response, an L1-type criterion is applicable and leads to alternatives for maximum likelihood fit