Short-course on the Space Elevator
I'm sitting in the airport; typing this on my phone. On my way to Budapest, to teach the world's first class on the Space Elevator. Check out Copernicus.Exosphe.re for details. (The Kickstarter interface is being finicky with posting that as a link. It is one. Copy/paste it.)
I'm teaching 15 hours on the Lunar Elevator. I'll be there for two weeks. (It's a the week course.) I'm very excited. This is the big PowerPoint I've been mentioning over the past month.
I'll continue posting updates from there.
(And no, before my critics can have a chance to attack me over this, I'm not spending KS funds for this trip.)
Take care, mjl
Unexpected Field Trip
Today was a little unusual. Unexpectedly, I didn’t spend a lot of time in the office. Instead, I got to go on a field trip! I was lucky enough to spend about 4 hours with the team developing this: Impact BioEnergy’s Horse (http://impactbioenergy.com/horse-ad25/ ).
It’s a pretty amazing machine. You feed it household food waste, grass clippings and leaves, and it turns that into useful products: electricity, gas, and nutrients for farming. It’s not quite as cool as Mr Fusion from “Back to the Future 2”, but is pretty dang cool!
I hope it’s obvious why I’m interested in this stuff… closed-loop ecosystems are vital for space. Ya, I know that is decades away for an application like this. But still, it’s a step closer. Everyone knows that astronauts drink their own recycled urine. (It’s at least as pure as the water that comes out of a typical urban water utility, and your own kitchen sink – and in some cases, its maybe a lot better!)
But if we’re really going to space, to stay, as a species… if we’re really going to Mars, or to develop free-floating space stations (like our proposed PicoGravity Lab at the Earth-Moon Lagrange Point), or if we’re going to establish permanent settlements on the Moon – then we need to figure out how to feed ourselves. We need to figure out how to recycle every step in the food processing cycle. We need to optimize plant growth, harvest, and re-use of those materials. Impact BioEnergy is just one piece of a grand and complicated puzzle. I was proud that they solicited my advice and opinions. I hope I was helpful. I’ll go back in a few weeks to check in on some other developments. Hopefully, I’ll have more to report.
Take care, mjl
I had a busy, but, ultimately disappointing day.
I spent most of the day working on that lengthy powerpoint I’ve been talking about for the past several weeks. I need to have it finished by Thursday, and I’ve got a ways to go – it’s 15 hours of classroom time! I’m enjoying the process of creating it. So far as I know, this is the world’s first dedicated course on Space Elevators. I am very excited about crafting this module on the Lunar Space Elevator.
Naturally, I’ll share the document when I’m done. There’s talk about maybe turning this into a video lecture series. If that happens, I’ll let you know. (I have no control over that.)
But the part that was disappointing is different. Remember two weeks ago, I talked about Professor Lynette? I had asked her to lead a big project… Well she talked it over with her husband, and decided that she had to decline. She’ll still be on the Technical Advisory Council, but she simply can’t tackle/run the project I was hoping for. She asked me for a smaller task, one that is time-delimited so that it ended by October. She needs to be able to focus on her students. So, I’ll do that; I’ll develop a project for her unique skills.
But that still leave a big hole in my plans. I need to find a replacement for her, so that my larger plans continue on schedule.
So, that was my day. I’ll work on responding to more comments, and work on another post regarding the robot. Take care, mjl
President, LiftPort Group
Hello, I hope your Sunday afternoon is treating you well. I had many questions throughout the past couple days regarding the robot design. I answered most of them in the comments section of KS, and on the individual photographs on G+. But there were three that I felt deserved special attention. PAUL: “… Could you talk a bit about the rationale behind your design? What made you chose that particular number of wheels? What made you chose that particular offset? What prevents it from sliding off? How are you controlling the motors? Are you using any rotary encoders or pressure sensors for getting some feedback in regards to string tension/slippage?”
Paul - Sure, happy to.
First, it’s a long, thin design because of our earliest experience – dating back to 2002 and working with something as simplistic as Lego. We learned that we have better balance and that we didn’t need “control” because gravity would do a lot of our work for us. From there, we established a couple aspects: top/bottom/front/back and how we place various components (like heavy batteries) determine how the thing moves. Also, we discovered early on, that we have a built-in moment arm – the longer we made the ‘bot. That helped with guiding the string to the right spot.
The number of wheels has been a kind of random. We’ve used a little as 4 and as many as 10. That’s one of the things that has frustrated our efforts. There is a delicate balance between the friction (based on the number of wheels) and that mass of the equipment (batteries, motors, communications, etc.,) needed to climb. We have not found that balance yet.
The offset is based on the maximizing amount of time that the ribbon is in touch with the wheels (and, conversely, minimizing the distance between wheels). As it is, it’s only got significant traction on 1/3 of a wheels’ surface, at any given rotation.
The Ribbon rides in a U groove that holds it in position on the outside of the wheel. Tension itself keeps the ‘bot on the Ribbon. We do things called “hang” tests, where we ensure that there is enough friction to that ‘bot can simply hang on the string, in mid-air, without assistance. That determines how many wheels we have/need. We’ve got a brain and comms to the ground, and we are able to control speed and direction of the motors through that. We do not have ongoing strain gauges running to notify us of changes in tension. This ‘bot needs to work through a variety of tautness of the string – from just a few pounds to more than 1000. (In the real world, the wind can pick up or drop off quickly, and that changes the tension of the string constantly.)
UNCLEVER TITLE: “… it's making me think that the tether would weave in between them and thus the elevator would hold tight onto the the tether as a result of the tether's own tension... Maybe I have the wrong impression, but wouldn't the tension be too high for that to be a practical design? Or wait, duh. Lunar Space Elevator, not Earth Space Elevator. So I guess in that case the tension might be much more manageable. I don't know.”
Unclever – See my explanation above, for part of that answer.
Yes, you’re right, we will have substantially less tension on the Lunar System – eventually. But we are a long long long ways from building that system. For the time being, we are stuck here in a 1G gravity well, so we need to make it work here. ;-) Some people think we are trying to leap from the 1 mile high system we built several years ago, and leap directly to a Lunar Elevator in one jump. That’s kinda insane. Nope, we’ve got a complete roadmap laid out – this test, then some record-breaking cubesat designs, then a couple LEO/MEO experiments, two tests we’d like to fly on the International Space Station, and then a big one around the Moon. Then, about 8-10 years from now, we MIGHT have the first stages of a Lunar Elevator. But we have to test everything (at this stage) in 1G.
I’m not trying to build the Lunar Elevator yet. I’m only trying to satisfy the requirements I set for myself for the Kickstarter. 2km would be pretty simple. The thing that has made it so challenging is the 7km stretch goal… (I really wish I’d never posted that damn stretch goal!)
ADAM: “… I really don't see any reasons for using a string instead of a ribbon. Could you please outline the pros and cons of each?”
Adam – We have a philosophy on our team called “No cheater solutions”. Meaning that there are lots and lots and lots of way of building this robot. However, if the long-term goal is to build a bot that teaches us something useful about building a Lunar Elevator, then that limits our options. For example, it would be effortless to put enough string on a single spool, and place a motor on the spool, and then climb. However, that solution won’t work on the long-term Lunar Elevator because it damages the string. And because the string we are talking about is a 250,000km long, billion dollar asset, we’re not going to build anything that damages it. Therefore, we don’t use solutions for this KS robot, which we can’t use in space.
That’s a long-winded necessary preamble. You see, it’s that philosophy that guides our design choices. And with that in mind, let’s move on to answer your question. The Earth Elevator was designed to be a wide, flat ribbon. (Lots of reasons for that. Read our MANY publications on the topic.) However, there are design constraints of the Lunar Space Elevator Infrastructure that preclude this. Namely cost, mass, and whichever initial rocket we use. So, we simply don’t have room/money/lift to build a Lunar Ribbon… so we default to a string. And, back to our earlier ideals, we threw out all (some) of what we’d learned building robots that can climb a ribbon, and have to start over and learn how to build robots to climb string (within the self-imposed and self-limiting constraints mentioned above).
So it’s not a question of pros and cons of ribbon versus string; we like the ribbon very much and would choose it if it were an option. It’s not. We have to design for a string.
Take care, mjl
(There is a summer block party that has reserved the street for 2 blocks north and south of my apartment. It feels like they are throwing a rave in my living room! The bass is shaking my monitor… I hope everyone is having a good Saturday.)
My update is pretty simple today.
I just finished 2.5 hours, responding to every comment on every daily update, and on every image I posted earlier this week on G+.
Thanks for all the great, engaging, and interested comments on the photos! Paul, Unclever and Adam asked specific questions about some of the design decisions we made. I’ll tackle those in the morning. I’ve got a bunch of other images for the 3rd stage of our effort – which I’ll again post to G+. I’ll tackle those once I’ve responded to these questions.
Take care, mjl
Thanks for all your comments regarding the photos I posted two days ago. I received some very nice personal messages, and your comments were helpful. The most common theme was that most people didn’t know what they were looking at… so for each of the 26 images, I’ve gone in and written a paragraph or two of explanation. Some of my comments are funny; a few are cynical and frustrated – because, writing about these images now, I have the advantage of hindsight. I know now what I didn’t know then.
Again, the link is: https://plus.google.com/+MichaelLaine/posts/2jPy3Cgtrso
About 600 people viewed ALL of those images. I’m grateful. Thank you!
Finally, my friend asked me “Why did you wait so long? Why didn’t you post these two years ago, when they were current?” I responded with: “At the time, I didn’t think this stuff was important. I was focused on getting the thing built, and showing the final product. Now, long after it’s too little, too late, I wish I’d posted this stuff. I have LOTS of this stuff.” I can get into more details about this stage, or other aspects of our development of the Lunar Elevator, or, depending on your response, I can switch gears to the 2nd stage of developing the ‘bot. Let me know what you want.
Take care, mjl
Another quiet day
Today was a pretty mundane day. Rather than focus on Kickstarter and the Space Elevator, I chose to focus on other projects.
The only two Space Elevator aspects of the day fall into the category of “I don’t want to talk about someday-maybe aspects”. I’ve said many times that I only want to post updates on things that I’m sure I can deliver on. The calls I made today were longshots; no need to talk about them.
As for the third robot update, I’ll postpone that. Several folks asked for more information on what happened during this first round, what do the images I posted mean? So I’ll tackle some explanatory text first.
Take care, mjl
Photos of the initial robot
I posted about 25 pictures and a write-up over on my G+ Page:
Robot post 1 of 3
Hi!There are really three stages of this robot experiment:
I’ll outline each of these. The first today, then the other two tomorrow and the next day.
First, we’ll start with the origin of this 19th robot. David and I looked at our legacy of the 18 prior ‘bots and thought we could build on that. However, we decided on a significant modification – switching from a Ribbon, to a Line.
Why? Because the Elevator we need for Earth will be wide and flat. The seven years, from 2001-2007 of prior effort was focused on the Earth Elevator, so naturally we tried working with a Ribbon analogy. During those first 18 robots, we worked with many Ribbon types (plastic, fiberglass, nylon, carbon composite, even surveyor’s tape) and widths (2-9 cm). Each had their own advantages and disadvantages. And each robot had to be modified for each Ribbon – attachment mechanisms, tensions, coefficient of friction for each gripping surface. We had to take into account the way that the motors were mounted, how they would be powered (for how long and at what speeds could we run the motors), and we spent a lot of time trying various gripping configurations. For each test, we’d actually be running 3-6 different individual experiments.
So this new set of experiments – paid for by our Kickstarter backers – was pretty different. We switched to a completely different lifting mechanism because the medium we were climbing (a rope, not a ribbon) changed form factor. We did this for the same reason we used to work toward the Earth Elevator; now we were working toward the Lunar Space Elevator Infrastructure. We know (think!) that the LSIE will require a very thin initial thread. Its form factor is more like a string than a Ribbon. David and I started re-designing based on this plan.
We assumed that we’d be able to take many of the lessons learned from the first ‘bots, and apply them across the board to this new design. We were right about certain aspects – modularity, weight distribution, placement and layout of the various components, guide systems, coding and (limited) artificial intelligence, telemetry and communications, etc. So we sketched out a basic design – the spine would be long and thin, while the gripping surface would be wide and round.
In hind-sight, it’s pretty easy to see where some of the mistakes occurred… but I’ll leave off and describe them in some detail over the next two updates. There’s a lot to tell, so if you’d like specific information please let me know.
Take care, mjl
A little overwhelmed
Unfortunately, real life preempted Space Elevator work today. I couldn’t do the work I’d hoped to accomplish this evening. I postponed both meetings, and delayed the write-up on the robotics.
Tomorrow looks calm, so I’ll try to catch up.
Take care, mjl