Lunar Surface Operations and Adaptive Structures Technology

1. Lunar Surface Operations and Adaptive Structures Technology 5th International Congress of Mechatronics EngineeringAutomation and Technology 3 March 7-10, 2007 Dr. David C. Hyland Director of Space Science and Space Engineering Research Texas A&M University Royce E. Wisenbaker Chair of Engineering Professor of Aerospace Engineering, College of Engineering Professor of Physics, College of Science

2. NASA’s Exploration Program • Before the end of the next decade, NASA astronauts will again explore the surface of the moon. This time, we're going to stay, building outposts and paving the way for eventual journeys to Mars and beyond. • The centerpiece of this system is a new spacecraft designed to carry four astronauts to and from the moon, and support up to six crewmembers on future missions to Mars. The new ship can be reused up to 10 times. • Initial missions will last four to seven days. The new ship carries enough propellant to land anywhere on the moon's surface. • Once a lunar outpost is established, crews could remain on the lunar surface for up to six months.

3. A heavy-lift rocket blasts off, carrying a lunar lander and a "departure stage" needed to leave Earth's orbit (below left). The crew launches separately (below, center), then docks their capsule with the lander and departure stage and heads for the moon (below, right). Three days later, the crew goes into lunar orbit (below, left). The four astronauts climb into the lander, leaving the capsule to wait for them in orbit. After landing and exploring the surface for seven days, the crew blasts off in a portion of the lander (below, center), docks with the capsule and travels back to Earth. After a de-orbit burn, the service module is jettisoned, exposing the heat shield for the first time in the mission. The parachutes deploy, the heat shield is dropped and the capsule sets down on dry land (below, right).

5. All this and more must be accomplished by the sortie team! ESAS Report – A crowded schedule Section 4.3.7.2: … A notional schedule of scientific investigations conducted during a lunar sortie crew mission is: • Day 1: Collect contingency surface samples and deploy scientific packages and robotic systems; • Days 2 and 3: Conduct field science during surface traverses and correct problems with science packages or robotic systems; and • Day 4 and beyond: Conduct return visits to sites of particular interest or discoveries and correct problems with science packages or robotic systems. 70% of astronaut time on the ISS is devoted to house-keeping. One might expect a similar need for labor-saving automation in Lunar outpost construction and operations.

6. Follow the exciting adventures of Astronaut Norm Frobenius and his friends on Moon Base 7!!

7. Our Cast Norm Frobenius Simbul Christoffel Ricci Tensor Fresnel Van Cittert Colonel Fu Hsi Gordon Klebsch Mantissa Von Mises

8. When his alarm chimed, Norm Frobenius felt rested and refreshed. It was time to begin a new “day” of exploration on Moon Base 7. Norm got up, stretched and took a leisurely shower (Water takes sooo long to fall in 1/6 g!)… Norm was a geologist and an expert in “in-situ resource extraction”. Norm’s list of favored items included oxygen in the lunar regolith, water deposits near the poles, (to supply almost all the Base’s water and air requirements) and iron and magnesium deposits and a host of other minerals and metals that allowed the base to produce most of its replacement parts and new equipment.

9. … Because every major structural element of Moon Base 7 has embedded sensors and actuators – • All combined in a system identification system • A health-monitoring and fault-detection system that can sound the alarm in the case of emergency events Living quarters Workshops Living quarters Now why had Norm slept so soundly?

10. Vision-based nav & location Robotic Vehicles Emergency Warning and Response Systems Teleoperable Robotics Numerous Existing DCS Technologies Can be Adapted to Lunar Outpost Operations Autonomous Rendezvous & Docking

11. U of M leads the way into the 21st Century With the First Scientific Experiment Aboard the ISS!!

12. Recent MACE II Activity Aboard the ISS… • Hardware launched and stowed aboard the ISS in September 2000. Experiments performed from Winter ’01 through spring ’01 • U. of M. autonomous algorithms “worked like a dream” – i.e. system learned, on-line, to design its own control law and to recover from hardware anomalies. Behavior replicated predictions. • Results are the first space flight demonstration of autonomous, self-reliant spacecraft control.

13. Frequency Domain Expert: Open- versus Closed-Loop Results

14. Shear stress sensor T F x Propagating crack ys F xs Axial stress sensor NN/GA Approach – Train a neural net to sound the alarm before failure, use a genetic algorithm to select the best sensor locations • A thin beam flexure (L=10, T = 1) is subjected to a lateral end force. • F(t) is discrete-time, low-pass filtered noise (with filter time constant = 10) • An end shear load sensor measures F and an axial stress sensor is mounted at {xs, ys} within the beam. (In effect, we measure s/F) • Given time history data on s/F, devise a NN/GA algorithm that will give warning before flexure failure L Very thin plastic deformation zone

15.   Cantilevered Flexure: Failure Warning System Training s(k)/F(k)  In biological systems, if a “wrong” answer is lethal, backpropagation of error to adjust neural weights cannot operate because just after the wrong response the organism ceases to function. In such cases, the neural weights are adapted via genetic mechanisms. = 0, if no alarm = 1, warning of imminent failure Backpropagate error to adjust weights The “right” answer For design simulations, we supply the output error signal and pretend the weights can be adjusted and the adapted system “transferred” to a still active individual. Hence, for each fixed sensor location we train the n-n to recognize s/F time histories warning of imminent failure

16. ys 1 4 0.75 3 0.50 2 0.25 1 xs ysbin 0 1 2 3 4 5 6 7 8 9 xsbin 1 2 3 4 5 6 7 8 9 10 Cantilevered Flexure Example: Set of Sensor Locations considered in GA Application

17. Population distribution at start of second generation Population distribution at start of fifth generation Population distribution at start of sixth generation Population distribution at start of third generation Population distribution at start of fourth generation 4 4 4 4 4 3 3 3 3 3 y coordinate of stress sensor y coordinate of stress sensor y coordinate of stress sensor y coordinate of stress sensor y coordinate of stress sensor 2 2 2 10 2 2 10 10 9 9 9 10 8 1 8 8 1 1 7 9 7 7 6 8 1 1 6 6 5 7 0 5 5 4 0 0 6 3 4 4 5 5 5 10 0 0 3 3 2 4 x coordinate of stress sensor 10 20 1 2 2 2 10 3 5 x coordinate of stress sensor x coordinate of stress sensor 1 1 population 15 30 4 2 population population x coordinate of stress sensor x coordinate of stress sensor 1 6 10 population population Initial population distribution: Each one of the sensor location bins is occupied by two individual systems Population after fourth generation: Population in the (1,1) bin now becomes dominant. Probability of mating and progeny in the alternate locations declines rapidly. Population after third generation: Descendents of the clump near (4,2) are heavily attrited by poor damage warning performance. (1,1) starts to “takeoff” due to mating within location. Population after fifth generation: Distribution is entirely dominated by the (1,1) design. This is known a priori to be the most effective sensor location. Population after first generation: Most individuals in the (1,1) and (1,2) survive but not those in less favorable locations. Mating occurs across distant locations & the progeny account for the clump around (4,2) Population after second generation: Distribution drifts steadily to the left. Individuals in (1,1) survive at over 90% rate while survival elsewhere is less than 20%. More mating occurs within the (1,1) location. Population Evolution via GA - Start & First Generation

18. When Norm got to the base galley, he joined five of the six other crew members for breakfast. While exchanging pleasantries, he mused that seeing and working with most of the rest of the crew would be impossible in the old days, before the era of Distributed Cooperative Systems (DCS). Before DCS, half the crew would have had to be awake and on duty at all times because humans had to do all the house keeping chores, maintenance chores and emergency response actions. Norm had read that in the old International Space Station crew spent 70% of their time just maintaining the system, with almost no time for scientific or exploration activity. But nowadays, most of the crew could maximize their collaborations by working and sleeping on the same schedule – with just one crew member taking “night watch” to serve as monitor and backup for the Base’s DCS. This was possible because the base was a kind of artificial organism, with a rudimentary intelligence, that lived in symbiosis with the humans it nourished and guarded. Living quarters Workshops Living quarters

19. Surface Concept - Does not accommodate long-term need for radiation shielding

20. Continuous sunlight Moon Base 7Location: South Lunar Pole Communications & observatories Solar arrays line both inner and outer surfaces of the rim wall Crater rim wall At least 3 m of rock Living quarters O2 production plant Surface transport garage Workshops Water ice deposits Living quarters The base in which they worked was mostly contained within tunnels and cellars bored into the side of a crater ring-wall. This provided enough lunar rock over their heads to stop most of the cosmic radiation – otherwise half their DNA would be destroyed within a year. The main facilities were connected by several surface access corridors that ran to a variety of storage and staging facilities located on the surface.

21. “Top of the morning to you, Norm!” said Ricci. “Good morning! How are you, Rick?” “So did you sleep OK last night?” asked Ricci. “Slept like a top – I feel clear-headed and alert - I can’t wait to get out to Monterrey Crater” Norm enthused. “But why do you ask? We usually sleep OK.” Ricci paused nonchalantly and then:

22. “It’s nothing terribly important – it’s just that when I checked the DCS morning activity report, I found that the DCS and Fresnel Van Cittert took care of quite a few little emergencies last sleep period ; Looks like old Fresnel gave the DCS a real workout- or maybe vice versa” zzzz… Living quarters “So, what happened?” asked Norm. “Well it seems a meterorite punched a hole through an external access corridor, then smashed a power converter, shorting out power to Number 4 air recycling oxigenator. The sudden drop in air pressure caused a few other complications as well.” Workshops Living quarters

23. Then the DCS controller detected all the problems, formulated an immediate action plan and submitted the plan to Fresnel. As soon as Fresnel gave his provisional OK, the DCS implemented the plan – The internal air lock to the access corridor was sealed, DCS robot work crews immediately did a permanent repair, and number 4 oxigenator was put on auxiliary power, while a spare power converter unit was brought in from storage. As we sit here, almost all the repairs are already done.” “So how did old Fresnel cope with all that?” asked Norm, beginning to look concerned. “Well, actually, he didn’t. What happened is that the self-healing structure of the access tube automatically closed the puncture – Thus making a temporary repair.

24. Construction of Self Healing Space Systems • Provide continuous healing over lifetime • Integrate the material surface without any ridges • 100 % recovery of mechanical strength A self-healing material is composed of 3 parts • Composite material – it is an epoxy polymer composite that is made up from carbon, glass or Kevlar and a resin. This material can be used for building the spacecraft. • Healing agent- the healing agent is a fluid called, dicyclopentadiene or DCPD. The fluid is in the form of encapsulated tiny bubbles that are spread throughout the composite material. • Catalyst – the function of the catalyst called grubb's catalyst is to enable the healing agent to heal the composite material. Catalyst and healing agent are separated until they are required to seal a crack.

25. The Self-Healing Process S.R. White, N.R. Sottos, P.H. Geubelle, J.S. Moore, M.R. Kessler, S.R. Sriram, E.N. Brown, S. Viswanathan: "Autonomic healing of polymer composites", Nature. 409, 794-797 (2001).

26. Alternate Approach: Capillary Action • Ian Bond, University of Bristol, UK • Scott White, University of Illinois Urbana-Champaign • Bond and his colleague developed a system analogous to the human system, but replacing blood with resin and veins with tiny glass tubes, to fill in cracks or small holes in satellite “skin” as part of a European Space Agency (ESA) program

27. The adhesive resin flows through a 40-micron wide space inside the glass fibers. • Other fibers filled with hardening agent are intermixed among their resin-full counterparts to cure and close a crack or hole. • The method successfully sealed breaches in material across a wide range of temperatures, from -148 degrees to 212 degrees Fahrenheit (-100 degrees to 100 degrees Celsius), in a vacuum chamber. It also sealed cracks within about 90 minutes.

28. Self-Healing materials – Additional References 1. S. Govindarajan, B. Mishra, D. L. Olson, J. J. Moore, J. Disam, "Synthesis of Molybdenum Disilicide on Molybdenum Substrates," Surf. Coat. Tech.76-77, 7-13 (1995). 2. S. R. White, N. R. Sottos, P. H. Geubelle, J. S. Moore, Mr. R. Kessler, S. R. Sriram, E. N. Brown, S. Viswanathan, "Autonomic Healing of Polymer Composites," Nature409, 794-797 (2001). 3. X. Chen, M. A. Dam, K. Ono, A. Mal, H. Shen, S. R. Nutt, K. Sheran, F. Wudl, "A Thermally Re-mendable Cross-Linked Polymeric Material," Science295, 1698-1702 (2002). 4. M. Trau, D. A. Saville, and I. A. Aksay, "Assembly of Colloidal Crystals at Electrode Interfaces," Langmuir13 [24] 6375-81 (1997). 5. P. Sakar, X. Huang, O. Prakash, and P. Nicholson, "Electrophoretic Deposition to Synthesize Advanced Ceramic/Ceramic Laminar Composites," in Advances in Ceramic-Matrix Composites N. P. Bansal, ed. (American Ceramic Society:Westerville, Ohio, 1993) p. 39. 6. W.B. Spillman Jr., J.S. Sirkis, P.T.Gardiner, "The Field Of Smart Structures As Seen By Those Working In It: Survey Results", SPIE, 2444, (1995) 18-277. J. Hodgkinson, "What Are Smart Materials Anyway?", Materials World. (August 1993) 4498. C. Dry, C. Warner, "Biomimetic Bone-Like Polymer Cementitious Composite", SPIE, 3040, (1997) 251-256.9. B. Files, G.B. Olson, "Terminator 3: Biomimetic Self-Healing Alloy Composite", Proc. Second International Conference on Shape Memory Superelastic Technologies: Engineering and Biomedical Applications, Pacific Grove, CA, (1997)10. M. McCallum, A, McGeorge, A. Witney, "Terminator 3+: The Biomimetic Smart Steel", (1995)11. J. S. Paine, C. A. Rogers, "Shape Memory Alloys for Damage Resistant Composite Structures", SPIE 2427 Active Materials and Smart Structures, (1995), 358-37012. Y. Furuya, A. Sasaki, M. Taya, "Enhanced Mechanical Properties of TiNi Shape Memory Fiber/Al matrix Composite", Materials Transactions, JIM, 34, No. 3 (1993), 24-22713. M. Taya, Y. Furuya, Y. Yamada, R. Watanabe, S. Shibata, T. Mori, "Strengthening Mechanisms of TiNi Shape Memory Fiber/Al Matrix Composites", SPIE, 1916, (1993), 373-38314. Y. Yamada, M. Taya, R. Watanabe, "Strengthening of Metal Matrix Composite by Shape Memory Effect", Materials Transactions, JIM, 34, No. 3 (1993), 254-26015. B. Files, "Design of a Biomimetic Self-healing Superalloy Composite", Northwestern University Dissertation Thesis, (1997)16. C. Forbell, M. Barney, C. Scharff, W. Lai, "Tin Based Self-healing Alloy", Engineering Design and Communication Class Report (1997)17. B. Sundman, B. Jansson, J.O. Anderson, "The Thermo-Calc Databank System", CALPHAD 9 (1985) 15318. E. Tao, M. Price, J. Asahara, K. Benes, T. Key, "Terminator III", Engineering Design and Communication Class Report (1998).19. H.C. Cao, B.J. Dalgleish. H.E. Deve, C. Elliott, A.G. Evans, R. Mehrabian, G. R. Odette, "A Test Procedure for Characterizing the Toughening of Brittle Intermetallics by Ductile Reinforcements," Acta Metallica, 37, no 11, 2969-1977.

29. Substrate Resin Coagulant Pressurized, Self-Healing Fabric Concept

30. Meteorites Atmosphere Water Oxygen “Gosh”, said Norm, “It makes you wonder how people ever thought they could do without a DCS.” “Well”, said Ricci, “It’s history. When you live on Earth, you can take a lot of things for granted. Chances are, while you’re asleep, you won’t be hit by a meteor, you won’t be thrust into vacuum and you won’t run out of oxygen. But out here, you have to guard against all that by yourself. The early explorers tried to do it without DCS and adaptive structures but found they had to spend all their time doing housekeeping things just to stay alive – no time left for much else.” Ultraviolet Radiation Cosmic Radiation

31. “We learned that, in space, a Man/Machine Symbiosis is needed to provide a safe, stable environment. Adaptive Structures “ To make life bearable for crew, allow reasonable time beyond survival duties for exploration and get collaborative synergy from crew able to share the same awake periods, we developed Distributed Cooperative Systems – A symbiosis of autonomous machines and structures and the human astronauts it sustains and protects” Radiation Shielding Reparable High E/ Service robots Atmosphere containment Comm. & Teleoperation facilities Fault recovery & emergency response Situational awareness Oxygen mining Water supply and reclamation Autonomous to Teleoperable robots Air filtration, CO/CO2 scrubbing, Oxygenation Self-healing Deployable Health monitoring

32. Nerissa Titania Hera Gloria Phaedria Celeste Norm wished Ricci a good day and headed out of the galley to his geology work station. With a territory the size of western Europe to explore, Norm could not do everything himself. He relied on a squad of robotic geology rovers that were, in essence part of the Base DCS, and that he could monitor and command from the Base. Once important deposits were identified, he would travel out to them himself to verify the discovery and superintend DCS work crews.

33. Nerissa Titania Hera Gloria Phaedria Celeste Monterrey Crater is 50 kilometers northwest of the base, reached just before the precipitous San Pedro Escarpment. Orbital spectroscopic surveys had hinted that the ten-kilometer wide crater floor could contain rich deposits of useful minerals. Over a week ago, Norm’s crew of robotic geologists had been transported to the site and had been carrying out semi-autonomous geological surveys for the last two days. Norm’s role in this case was to serve as the human supervisor of the robotic work gang.

34. The team of robot geologists had been working on their own, continuously, for the past two days. So Norm’s first task was to read their activity and status reports, query each robot, if need be, for more detailed information, and then decide to update or re-direct his high-level commands. He saw that robots Phaedria, Gloria and Celeste had completed one half of a spiral circuit of the crater floor while Nerissa and Titania had finished examining the east interior face of the ring-wall and were presently moving on to the northeast face. Hera, the “Queen” was stationed halfway between both groups, monitoring their operations. … Norm noticed from Titania’s instruments that she appeared to be approaching a series of interesting striations in the cliff face toward which she had been heading. Norm looked closely at the spectrometer readings as Titania approached closer and closer to the rock wall. Suddenly Norm saw clear indications of Aluminum Oxides!

35. When important observations like this occurred, the human supervisor would over-ride the robot’s autonomy and run it in telerobotic mode. Thus the presence of an experienced human geologist could be achieved remotely whenever opportunity knocked. Thus operating Titania, Norm approached the cliff face. A long stripe of darker material appeared across the rock face only one and a half meters above the floor. Here was a massive seam of Aluminum Oxide. Further up the cliff, Norm could see a whole succession of stripes. His instruments showed Boron Silicate and more Aluminum Oxides! Norm told Hera to concentrate the gang at his location and to comprehensively map the location and extent of these valuable deposits. He added that he would be at the site in person, with additional mining equipment within three hours and that they should keep at their survey until his arrival. Norm then unstrapped himself from the harness, restored autonomy to Titania and raced down the corridor to one of the external access tubes.

36. Curley Larry Norm takes a rocket pallet loaded with two Mark IV Miners out to Juang crater

37. Curley Larry Norm told Larry and Curly to unload themselves from the pallet, then hopped over to where “the six sisters” were exploring the cliff face deposits. Norm then began a “Follow Me” session in which he showed the robots, step-by-step, what to do. When the entire sequence of actions needed to locate the select ore, extract it and load it for transport was acted through, the robot gang and the DCS overseer learned the routine from Norm’s example and devised generalizations needed to carry out the task despite untoward circumstances. After three hours of work, Norm stepped back a pace and ordered the robot work gang to correctly repeat the sequence he had taught them by example. He looked on in satisfaction as Phaedria and Celeste located the richest deposits, Larry drilled and pounded to extract the ore from the encompassing rock, and Curley collected the precious ore and shoveled it into the cargo containers.

38. Larry But as Larry was drilling, a shard of ore hit Norm’s suit, cut a slit in the material and sliced a feed line supplying his suit oxigenator. The first inkling he had that there was something wrong was a message on his visor display: RETURN TO THE PALLET CAB IMMEDIATELY! YOUR SUIT OXIGENATOR HAS MALFUNCTIONED. RETURN TO THE PALLET CAB IMMEDIATELY! Norm raced to the cab, sealed the cab door and laid down unconscious.

39. Only five minutes later, although it seemed forever, Norm took a deep breath and sat up to find that his suit helmet had become detached from its collar and that the pallet cabin had become, miraculously, fully pressurized. As he was to find out somewhat later, the self-healing material of his suit had prevented depressurization. Also, the Base DCS had taken note of his trip plans to coordinate all its resources for his safe return. The system had monitored his trip progress, and his vital signs as measured by the suit instrumentation. When sensors had discovered his severed oxigenator line, the system had not only flashed the warning on his visor screen but had formulated and carried into effect the plan for his recovery. Before he even reached the pallet, the DCS had begun pressurizing the cabin.

40. With a sigh of relief, Norm decided to wrap up operations in the crater. He commanded Phaedria and Celeste to stay with the two miners and Gloria, Titania and Hera to continue their survey of the rest of the rim-wall. Finally, he commanded Nerissa to follow his trajectory back to the base, laying tiny transponders along the path in order to guide the robotic cargo-haulers in their round-trip to collect and deliver the ore.

41. Without further incident, he piloted the pallet back to base, landed and entered the hanger to find that it too was pressurized and filled with the other six crew members of the Base. As Norm stepped out of the cab, he saw not only the two crew he had spoken to that morning but all five other crew members of Base. Most ominously of all, the Base Director, Colonel Fu Hsi was on hand, looking every bit prepared to give a long-winded speech!

42. “Welcome back my boy. The DCS main controller alerted us to your suit failure and although the reaction was quick, we were nevertheless quite concerned for your safe return. What’s more, I would like to congratulate you on your accomplishment today. The reports that have come in show that the ore deposits you discovered are even richer than you imagined. With this discovery, once our robot processors refine the ore, this Base will become self-sufficient in structural metals. You’ve earned “shore leave” for the next week.”

43. Now I can visit Mantissa Von Mises! With formalities done, Norm and the group started their walk back through the access corridor to return to the main base chambers. At the prospect of shore leave, Norm was looking forward to spending time with Mantissa Von Mises. Mantissa was also a geologist and she and Norm had met while they were on a large-scale topographic survey.

44. “Well done, Norm!” said Ricci as he clapped Norm on the back, interrupting his reverie. “Thanks Ricci, but it’s thanks to Adaptive Structures technology and the DCS that I’m still here.” “All the same”, replied Ricci, “Once the next consignment of solar arrays arrives to power the LCRP (large-component rapid prototyping machine), and your ore gets refined to aluminum, we can start expanding the base, and bring some families out here! “ A central element of the human habitation of the solar system was the integrated collection of technologies that permit small human groups to produce all or most of their consumables (air, water, food), generate power and replenish their tools; all with the maximum use of local resources. And a central element of this “habitation technology” was the ability to fabricate tools and all manner of devices, on the spot, using in-situ materials. Delivery of enough solar array to power the LCRP (already on base), coupled with Norm’s geologic discovery would allow the base to expand quite quickly.

45. Simbul Christoffel had been walking just behind Norm and Ricci and had been overhearing their conversation. “Sorry my friends, but I must say, I’ve heard disturbing news concerning the solar photovoltaic consignment. This morning, I was watching Earth News and they said the Alderberan heavy launch vehicle had serious technical problems and was grounded pending a full evaluation…” As Norm stumbled into the Base Recreation Room and despite his shore leave, Mantissa and all else, he felt his expectations sorely deflated…

46. Norman! Why are you looking so glum?, said Colonel Fu Hsi. Norman explained his conversation with Simbul Christofel. “It seems our hopes for the future are dashed!” “Nonsense, my boy!” You must not underestimate the versatility of multi-functional materials! We have abundant supplies of self-healing cave sealant and although we had intended to use the material for structural purposes, it is also equipped with photovoltaic film. When I heard about the Aldeberan, I ordered the cave sealant to be deployed as a solar array fully capable of powering the LCRB. Thanks to multi-functional materials and your ore discoveries, our plans for base expansion can go full speed ahead!”

47. Technologies for Human Habitation of the Solar System • Self-Healing Materials and Structures: • In industrial-scale work, wear and tear is unavoidable. • In the unforgiving Lunar environment, instant repair is vital. • Multi-functional Materials and Structures: • Replacements and supplies will be infrequent and not reliable. • The suitability of materials for multiples uses provides system reliability through functional redundancy. • Distributed Cooperative Systems • Human labor is in extremely short supply. • A symbiosis of automated systems, robots, smart materials with human astronauts is essential to crew productivity and safety. • Sustained Habitation Technology: • A solar system society will not subsist by exchanges of matter but by exchanges of knowledge and ideas. • We need a moveable package of technologies that allows a small human group to generate most consumables, extract and use in situ resources, and repair and even improve their own tools.

48. Fin Muchas gracias!