%PDF-1.1 % 8 0 obj << /Length 9 0 R >> stream BT 1.0074 0 0 1.0074 72 698.16 Tm 0 0 1 rg /F0 10 Tf 0.0019 Tc 0.1167 Tw (\(INCOMPLETE--Scanned Text, missing figures\)) Tj 107.2007 -107.2007 TD 0 0 0 rg /F1 10 Tf -0.0243 Tc 0.1428 Tw (A MOBILITY CONCEPT FOR MARTIAN EXPLORATION) Tj 30.4927 -13.3405 TD 0.0272 Tc 0.0916 Tw (Nicholas C. ) Tj 50.2652 0 TD -0.0013 Tc 0 Tw (Costes) Tj ET BT 0.9998 0 0 0.9998 288.24 582.72 Tm /F1 6 Tf 0.1208 Tc (1) Tj ET BT 1.0074 0 0 1.0074 291.36 576.72 Tm /F1 10 Tf 0.0197 Tc 0.0991 Tw (, F. ASCE and Stein ) Tj 84.5695 0 TD 0.0154 Tc 0 Tw (Sture) Tj ET BT 0.9998 0 0 0.9998 397.92 582.72 Tm /F1 6 Tf 0.1208 Tc (2) Tj ET BT 1.0074 0 0 1.0074 72 548.88 Tm /F1 10 Tf -0.0121 Tc (ABSTRACT) Tj 0 -27.1575 TD 0.0301 Tc 0.0888 Tw (Soil mechanics and geological investigations on Mars or the Moon are described herein, using a novel mobility) Tj 0 -11.9112 TD 0.0227 Tc 0.0961 Tw (system, designated as the "Elastic Loop Mobility System \(ELMS\)". ELMS was developed as a spin) Tj 401.8837 0 TD 0.0186 Tc 0.1002 Tw (-off of the U.S.) Tj -401.8837 -11.9112 TD 0.02 Tc 0.0988 Tw (Lunar Roving Vehicle \(LRV\) which operated on the Moon during the Apollo 15, 16, and 17 Missions.) Tj 0 -23.8224 TD 0.021 Tc 0.0978 Tw (Extensive testing of the ELMS, both on soft soil and on rigid obstacles, has shown that the ELMS outperforms by) Tj 0 -11.9112 TD 0.0284 Tc 0.0905 Tw (far both the LRV and the two unmanned, self) Tj 183.4324 0 TD 0.0259 Tc 0.093 Tw (-propelled Soviet rovers, ) Tj 102.6745 0 TD 0.0249 Tc 0.0939 Tw (Lunokhod 1 and 2, which landed on the) Tj -286.1069 -11.9112 TD 0.0187 Tc 0.1001 Tw (Moon in the western part of Mare ) Tj 138.8845 0 TD 0.0404 Tc 0.0786 Tw (Imbrium, aboard the spacecraft ) Tj 129.1173 0 TD 0.0292 Tc 0.0897 Tw (Luna 17 and 21. In this paper, examples of soil) Tj -268.0019 -11.9112 TD 0.0388 Tc 0.0802 Tw (mechanics and geological investigations that can be conducted either by an unmanned, self) Tj 368.7705 0 TD 0.0224 Tc 0.0965 Tw (-propelled ELMS) Tj -368.7705 -11.9112 TD 0.0342 Tc 0.0848 Tw (rover, or by an ELMS attached to a Martian ) Tj 180.0972 0 TD 0.0334 Tc 0.0855 Tw (Lander are discussed, along with the associated instrumentation.) Tj -180.0972 -23.3459 TD 0.0295 Tc 0.0894 Tw (Through such investigations, ascertaining the existence of some primitive forms of past or present life on Martian) Tj 0 -11.9112 TD 0.0369 Tc 0.082 Tw (or Lunar geological formations may become possible, in addition to obtaining numerous data on the mechanical) Tj T* 0.0275 Tc 0.0913 Tw (and physicochemical properties of Martian or Lunar soils along long traverses.) Tj 0 -24.7753 TD -0.0263 Tc 0 Tw (INTRODUCTION) Tj 0 -23.8224 TD -0.0118 Tc 0.1304 Tw (As a spin) Tj 37.4011 0 TD 0.0267 Tc 0.0922 Tw (-off of the Lunar Roving Vehicle \(LRV\), which operated very) Tj 250.8497 0 TD 0.0213 Tc 0.0975 Tw ( successfully on me lunar surface during) Tj -288.2509 -11.9112 TD 0.0129 Tc 0.1059 Tw (the Apollo 15, 16, and 17 Missions \() Tj 147.6988 0 TD -0.0013 Tc 0.12 Tw (Costes ) Tj 29.3015 0 TD /F2 10 Tf 0.0589 Tc 0.0602 Tw (et al) Tj 17.8668 0 TD /F1 10 Tf 0.0357 Tc 0.0832 Tw (., 1972\), a novel mobility system designated as the "Elastic Loop) Tj -194.8671 -11.9112 TD 0.0266 Tc 0.0922 Tw (Mobility System \(ELMS\)" was developed at Marshall Space Flight Center with the cooperation of the then) Tj 0 -11.9112 TD 0.0316 Tc 0.0873 Tw (Lockheed Missiles and Space Company, Huntsville, Alabama, and the U.S. Army Waterways Experiment Station) Tj T* 0.0335 Tc 0 Tw (\(WES\),) Tj 30.4927 0 TD 0.0195 Tc 0.0993 Tw (Vicksburg, Mississippi. The ELMS has been assessed under a variety of testing modes and terrain) Tj -30.4927 -11.9112 TD 0.0353 Tc 0.0836 Tw (conditions and its performance has indicated that in a low gravity environment it exceeds by far the performance) Tj 0 -11.9112 TD 0.0414 Tc 0.0775 Tw (capabilities of either the manned LRV or the unmanned, remotely controlled, self) Tj 330.1783 0 TD 0.0356 Tc 0.0833 Tw (-propelled vehicles ) Tj 79.805 0 TD 0.008 Tc 0.1107 Tw (Lunokhod 1) Tj -409.9833 -11.9112 TD 0.0286 Tc 0.0903 Tw (and 2 which landed on the Moon aboard the then Soviet Spacecraft ) Tj 274.1957 0 TD 0.0201 Tc 0.0987 Tw (Luna 17 and 21 \() Tj 69.0849 0 TD 0.0185 Tc 0.1003 Tw (Vinogradov, 1971\).) Tj -343.2806 -21.2019 TD 0.0182 Tc 0.1006 Tw (For these reasons, at the request of the then Director of NASA ) Tj 254.4231 0 TD 0.0369 Tc 0.0821 Tw (Langley Research Center \() Tj 108.1536 0 TD 0.0328 Tc 0.0861 Tw (Cortright, 1974\), the) Tj -362.5768 -11.9112 TD 0.0201 Tc 0.0987 Tw (ELMS became the candidate mobility system for a "1975" and a "1979" "Mobile Viking Mission" to Mars. Phase) Tj 0 -11.9112 TD 0.0329 Tc 0.086 Tw (1 studies showed that such a mobility system, which would have been attached to the main spacecraft, could) Tj T* 0.0272 Tc 0.0916 Tw (sustain a free) Tj 53.3621 0 TD 0.0336 Tc 0.0854 Tw (-fall landing on Mars and enable the spacecraft to traverse a distance of about 500 kilometers) Tj -53.3621 -11.9112 TD 0.0239 Tc 0.0949 Tw (\(Jackson, 1976\) on the Martian surface, for a period of two years, without refurbishment of its consumables. These) Tj 0 -11.9112 TD 0.0329 Tc 0.086 Tw (missions, however, did not materialize because of budgetary constraints.) Tj 0 -22.8695 TD 0.032 Tc 0.0869 Tw (With the renewed interest in Martian and Lunar Exploration, this paper will address ELMS performance) Tj 0 -11.9112 TD 0.0305 Tc 0.0884 Tw (characteristics and issues related to its design. However, the main emphasis of the paper will be put on soil) Tj T* 0.0309 Tc 0.088 Tw (mechanics tests and geological investigations that can be performed on Mars with the ELMS, drawing heavily) Tj T* 0.027 Tc 0.0919 Tw (upon the current experience from the Microgravity Experiment, "Mechanics of Granular Materials \(MGM\)", now) Tj T* 0.0107 Tc 0.108 Tw (in progress.) Tj ET BT 72 74.4 TD /F3 10.08 Tf 0 Tc 0.0363 Tw ( ) Tj 79.2 0 TD ( ) Tj ET 72 76.56 144 0.48 re f BT 72 66.96 TD /F3 6.48 Tf 0.0002 Tc 0 Tw (1) Tj 3.36 -4.56 TD /F3 10.08 Tf -0.0046 Tc 0.0408 Tw ( Senior Research Scientist, NASA/George C. Marshall Space Flight Center, Huntsville, Alabama 35812) Tj -3.36 -7.44 TD /F3 6.48 Tf 0.0002 Tc 0 Tw (2) Tj 3.36 -4.56 TD /F3 10.08 Tf -0.0038 Tc 0.0401 Tw ( Professor and Chair, Department of Civil, Environmental, and Architectural Engineering, University of) Tj -3.36 -12 TD 0.0307 Tc 0.0055 Tw ( Colorado, Boulder, Colorado, 80309-0428) Tj ET endstream endobj 9 0 obj 6658 endobj 4 0 obj << /Type /Page /Parent 5 0 R /Resources << /Font << /F0 6 0 R /F1 7 0 R /F2 10 0 R /F3 11 0 R >> /ProcSet 2 0 R >> /Contents 8 0 R >> endobj 14 0 obj << /Length 15 0 R >> stream BT 1.0074 0 0 1.0074 72 698.64 Tm 0 0 0 rg /F1 10 Tf -0.0267 Tc 0.1451 Tw (MAJOR DESIGN FEATURES OF THE ELMS) Tj 0 -27.1575 TD 0.0271 Tc 0.0918 Tw (About 64 years ago, an English inventor, J. K. Kitchen \(Kitchen, 1933\) proposed a continuous track, made of a) Tj 0 -11.9112 TD 0.038 Tc 0.081 Tw (highly elastic metallic material which would stiffen along the straight sections due to a pre) Tj 367.103 0 TD 0.0196 Tc 0.0993 Tw (-formed transverse) Tj -367.103 -11.9112 TD 0.0263 Tc 0.0925 Tw (curvature, as shown in Fig.1. This continuous and endless track eliminates several sources for friction and) Tj 0 -11.9112 TD 0.0391 Tc 0.0798 Tw (mechanical complexity, because no bogie wheels or track links are required. The tight fit between the rollers and) Tj T* 0.0248 Tc 0.0941 Tw (the track poses a high risk for jamming and internal losses caused by the continuous crushing of foreign particles) Tj T* 0.033 Tc 0.0859 Tw (trapped between track and rollers. Attempts by ) Tj 192.2467 0 TD 0.0349 Tc 0.084 Tw (Bendix to apply a continuous track concept to a small unmanned) Tj -192.2467 -11.9112 TD 0.0132 Tc 0.1056 Tw (Surveyor Lunar Roving Vehicle \(SLRV\) were not successful \(Moore ) Tj 281.1042 0 TD /F2 10 Tf 0.0788 Tc 0.0404 Tw (et al., ) Tj 25.7282 0 TD /F1 10 Tf 0.0196 Tc 0 Tw (1970\).) Tj -306.8324 -21.2019 TD 0.0383 Tc 0.0806 Tw (In the ELMS concept, the elastic loop performs a dual function, namely:) Tj 0 -26.2046 TD 0.0304 Tc 0.0884 Tw (\(1\) It distributes the load over a large footprint, without bogie wheels, and) Tj 0 -11.9112 TD 0.0097 Tc 0.109 Tw (\(2\) It provides spring suspension, through the 180) Tj 200.8227 0 TD 0.0149 Tc 0.1039 Tw (-degree bends of each loop as suspension springs \(Figs. 2, 3, 4,) Tj -200.8227 -11.9112 TD 0.0336 Tc 0.0853 Tw (and 5\).) 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