Although the day started with difficulties, it ended with a successful 1000 foot space ele
Although the day started with difficulties, it ended with a successful 1000 foot space elevator test climb to a tethered 10-foot diameter balloon - LiftPort's first really significant climb. This was supposed to be a 1 mile climb test, but the FAA-required aviation orange paint - applied at 50 foot intervals to the ribbon - contained acetone, which weakened the ribbon. The first two attempts of the day resulted in ribbon breaks due to this acetone-induced degradation. (Lesson here: test what you will use!)
With the ribbon in a weakened state, three (or even two) balloons created more lift than the ribbon could handle without breaking. Therefore, only a single balloon was used for a 1000' target altitude. We made the run back into town - about 12 miles away - and bought all the string we could find so we'd have enough for a safety line to a balloon at 1000'.
One balloon (instead of 3) means only 1/3 the buoyancy, so there was just enough margin (due to weight of lifter robot, ribbon, safety line, wind, etc.) to climb 1000', causing the robotic lifter - nicknamed Sword of Damocles (see http://en.wikipedia.org/wiki/Sword_of_damocles ) - to actually climb horizontally for about 150 feet. Nevertheless, the test was considered a success!
Consider this: our test system climbed 1000' for this test. The tallest building in the world - the CN Tower in Canada (http://www.cntower.ca ) - is 1815 feet tall. The elevators on those buildings are not continuous. You need to stop & change elevators at certain floors. So, there is justification to say that this test system was the tallest elevator in the world at that time. At 2,063 feet, the KVLY-TV mast antenna near Fargo, North Dakota (http://www.kvlytv11.com/info/info_tower.html ), is the tallest supported structure in the world and our system was about half as high as that. A couple months later we put up a system that was about a mile high (5300') with a lifter that climbed 1500'.
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Added: 1 year ago
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On a snowy, gusty fall day on the Massachusetts Institute of Technology (MIT) campus in Ca
On a snowy, gusty fall day on the Massachusetts Institute of Technology (MIT) campus in Cambridge, MA, little "Squeak" climbs just over 300 feet on a ribbon suspended from the roof of a tall building while several hundred observers watch both from the ground and from the windows of a nearby building. The climb text coincided with a Students for the Exploration of Space (SEDS - http://www.seds.org ) conference being held at MIT (http://www.mit.edu ).
MIT security required that the lifter robot have a safety line attached in case it fell. Unfortunately, the wind caused the safety line and ribbon to entangle with the robot, which came to a stop before reaching the top. However, within moments, "Squeak" broke the safety line and kept climbing - much to the relief of the LiftPort team - and completed the climb successfully.
This was the first and only public demo of the system and it was the last climb up a building. At this point we had learned everything we could from climbing the side of a building. We had to climb higher - i.e., use balloons.
While at MIT, we also forged couple of interesting relationships: the MIT carbon nanotube lab & a budding relationship with the Air Force.
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Added: 1 year ago
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This video shows a demonstration of our third lifter robot, which was built with LEGOs for
This video shows a demonstration of our third lifter robot, which was built with LEGOs for the Robotic Society of America annual event using the original NASA Institute for Advanced Concepts (NIAC) (http://www.niac.usra.edu/ ) design. A photo of it even appeared in Wired Magazine (http://www.wired.com/ ). This was during our "really broke" days when we were just getting started - around April 2003. We learned a few key things from building this simple robot.
We often get laughed at for using LEGOs for our lifter robots, but we did it for important reasons. Nobody has ever built a space elevator before. It was simpler, cheaper and faster for us to use a pre-defined system - i.e., LEGOs - than to design something totally from scratch. For this lifter, we spent a couple weekends monkeying around with stuff until we came up with the design you see in the video.
We found that it wasn't enough to build robot to climb a string. The first thing you need to do is find a string the robot can actually climb! We tried different tapes, ribbons, cloth, silk, nylon, etc. Nothing was working the way we wanted it to. Some of the materials were too slick, which made it difficult for the lifter's wheels to grab. The winning ribbon material is actually standard fiberglass drywall tape. It turns out that this ribbon is very strong under tension.
Michael and his friend Dave actually tested the materials' strengths - including that of the drywall tape - by sitting foot-to-foot on the floor with the ribbon wrapped behind their backs and pushing off against each other to apply tension. Since they both weigh 200+ lbs and are fairly strong, this was quite a stress on the ribbon materials. Also, while doing this testing, we had to wrap the end of the ribbon around screwdrivers in order to apply the tension evenly across the width of the ribbon. Otherwise there was too much localized stress and the ribbon would break.
While building and testing this lifter, we learned that some of the fundamental concepts from the original NIAC proposal had some flaws in them. The lifter design had only 2 wheels pushing against each other to grip the ribbon, which meant friction only at one small point on the ribbon. So we needed a better drive system. We also discovered the importance of a guide system at the top of the lifter to hold it in place. The center of mass kept shifting around because of this somewhat "blocky" design.
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Added: 1 year ago
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The robot lifter here was probably the fourth lifter robot we built. We designed it as an
The robot lifter here was probably the fourth lifter robot we built. We designed it as an example for one of the annual Robotic Society of America (http://www.robots.org/ ) competitions, but we didn't actually enter the competition since we were a sponsor.
In this demo, we use a different type of ribbon (surveyor's tape) and only climbed about 7 feet, though at a much faster climb speed than previous versions. This design (approximately 11 in. x 4-5 in. x 2 in.) was not as "blocky" as the previous design and thus did not suffer the same awkward center of mass changes as before. We also made some improvements to the guide system.
Although it was built with a LEGO body, this is the first time we designed our own robot "brains" (both the hardware and the code) instead of using the LEGO Mindstorms system (http://mindstorms.lego.com/ ). This is also one of the first designs to start having truly robotic features such as sensors to detect when the lifter is at the top or bottom of the ribbon. In the video you can see an example of this when the top sensor contacts the top "touch plate" (there is also a "touch plate" at the bottom).
The lifter had a braking/locking mechanism. If power was cut while climbing, the robot would stop. However, we have not used the braking system since then.
Finally, this was the first lifter to have a passenger: a LEGO figure named "A. B. Clark".
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Added: 1 year ago
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This is a 'backyard' test of balloons and bots, before we started climbing very high.
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Added: 1 year ago
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