SpaceTether.com Moon1 - MVP Tether Architecture I am Vince Cate and I love space tethers. I have a website spacetethers.com but have only done one recent update spacetethers.com/moon-l5 and nothing else in the last 20 years or so. Below I have some notes on a design for a first tether project that keeps the initial costs as low as possible but gets some useful work done if the tether works. A Minimum Viable Product (MVP) that could actually make money and not just be a demo. I would like you to expand on these ideas and make an html document that I can put at http://spacetethers.com/moon1 Please use one or more of the following thruster in designing the system below: Turion TIE-20 GEN2 Thrust: 55 mN ISP: 4500 Power: 2000 watts Price: $150000 $/mN: 1899 Mass: 23 kg Tether Idea: I am thinking of a rotating tether, perhaps 50 km, that is sent from Earth to a lunar orbit with a number of payloads to deliver to the surface of the Moon. It will use its own high ISP thrusters and solar power to move from LEO to lunar orbit. I like the thruster specs at the end of this document. We might use more than one. We can start with small payloads, say 10 Kg each. So perhaps we send up the tether with 50 to 100 payloads and every few days it lowers another payload down. We want to end up using a high ISP thruster on the tether to create the momentum change needed for each payload drop. This will take less reaction mass than if chemical rockets were used. The tether rotates such that at "the tip" of the tether the rotational speed countered the tether's orbital speed at perigee. We might release 100 to 1000 meters above the Moon at essentially no velocity relative to the Moon. From this height it would be 18 m/s to 58 m/s speed when it gets to the surface. We expect maybe the first few would be at 1000 meters and then we work down to 100 meters. For simple and small payloads the payload might be some air bag or crush material so it could survive the impact when it hit the Moon. Regolith is often soft and so may aborb some energy as well, though might lose some payloads if we counted on that. We will have the bulk of the solar and thrusters at a movable module that usually sits at "the ballast end" of the tether. This changes the "total system momentum" of the orbiting system. So if 10 Kg and 1600 m/s then the system momentum change that we need for each payload is 16,000 Kg-m/s. Please estimate how long it takes to get that and the thrusters you think we should have (getting from LEO to moon in 6 months may drive the number of thrusters). The tip of the tether will have some fixed like release mechanism, positioning, communications, sensors, net, solar power, which collectively we will refer to as the "tip end assembly". The tether mass will be something like 10 times the combined mass of the tip end assembly and one payload mass. But because any mass at the tip results in 10 times that in the tether mass, we want a design that minimizes the mass of the tip end assembly. Without a thruster at "the tip" we will use "Gravity Gradient Pumping" as Tethers Unlimited, Forward, and Hoyt have discussed. This lets us get sort of transfer some of the orbital energy into rotational energy. This design keeps the tip end light so the tether is mostly just dealing with the payload at the tip end and not the weight of the thrusters and solar panels. The payload will be sent to the tip end. The movable module end can move along the tether pulling the tip closer while it is rotating away from the Moon and letting it out further so it has longer to fall toward the Moon. This will increase the rotational tip speed. With the right design this can get the tip speed up in a day or so. By having the ballast end move along the tether we can also get the phase of the rotation so the tether tip is down at perigee and release the payload. It will also let us drop tiny payloads in many different locations on the Moon. This system should be much less total mass than if chemical rockets were used to lower all the payloads to the Moon. So even the first mission can be cheaper than a chemical rocket alternative. And future missions could just bring more reaction mass and payloads and reuse the tether, thruster, solar panels from the first mission. Please give me your thoughts about how this might work, if it seems a good first use of a tether, what sorts of mass for all the parts. Some of the early payloads will go together to make a tiny robot backhoes. Also some will have solar panels to charge the backhoes. Some of the initial payloads can be pieces that the robot backhoes can put together to make some sort of catapult. The robot backhoes will fill up some bags with regolith so they have the right mass for a standard payload. The catapult will be able to toss a payload from the Moon's surface up 100+ meters to where the tether tip can catch it. If we get payloads going both ways then we have a real "momentum exchange tether" and we won't need much thrusting or tether pumping. To "catch" we can have a net with some size holes, say 5 cm. The payload will have a number of things that could squeeze through 5 cm holes but would then hook so as not to pull back. So the payload could be caught in this net. The tether would have the net out some width, say 10 meters diameter and moving at some speed, say 30 meters/second relative to the surface of the Moon at Perigee, so it sort of sweeps out an area but at a gentle speed. If the payload gets in that area at the right time it can be caught. We have some devices so that we can know where the net is exactly as it passes near the Moon. So maybe there are reflectors on the net and on the Moon perhaps a lidar sensor. We will be able to gradually practice getting closer and closer to the Moon's surface before doing any catch. We can also do many practice catapult launches and see where they go exactly. The robot backhoe can go get the bags so they can be used again and again. So we can test both where the payload will fly and where the net will pass as many times as it takes to get things adjusted right before actually even attempting a real catch. We can also practice the timing without doing actual catches, just testing that we can tell the right time to do the catapult. This incremental testing gives us a good chance of it actually working when the parts look ready. The catch is the hardest part. This is what we want to work toward. But if the first mission was able to get payloads to the Moon it would be a huge success even if it did not get the catch and lifting from the Moon to work. The mobile module will be able to pull the whole tether through to the "tip end" can be worked on to attach payloads, net, or remove a payload from the net. There will be some sort of robot to do things. Can also inspect the tether as it passes over it. If the tether is getting worn we could have a way to change the tether. Please sketch out a design listing how many watts of solar and how many thrusters Try to design it so that it can get from LEO to the Moon in less than 8 months with its own thrusters so we can iterate at a reasonable rate. Make a table with mass estimates for the parts and their costs. Calculate the launch costs if when we launch Falcon-9 is down to $1000/Kg to LEO or if when we launch Starship is $200/Kg to LEO. Calculate the $/Kg for delivery to the moon this setup might breakeven (just direct costs of mission not development costs). We would also want to have some of the initial payloads be tinny satellites that we can toss from Lunar orbit to L5. By adjusting the mobil mass and tether pumping we can adjust the tip speed so that it is correct for a toss to L5. These payloads will have to have some small thrusters to do course correction and so make it to L5. This is sort of a demo/test for future plans of a tether moving cargos between L5 and the Moon's surface. We could even try one of these coming back and doing a "catch" but that would be much harder than one from the Moon's surface. We would only try this after all the payloads had been delivered to the surface and any surface pickups were working. The tether orbit is an ellipse fixed relative to the stars. The moon is rotating slowly, so the perigee of the tether orbit will be in different places each time. If the moon is rotating once in about 28 days and we want to have the backhoe/solar/catapult be near the point, how fast does it have to move? We will do this so that the backhoe is always in the sun. This way it always has power and does not freeze in the lunar night. The tether will have to rotate the ellipse of its orbit slowly so that once a year it has done a rotation. Eventually we will want to bring water up from the Moon to fill up the thrusters. Some universities, companies, or people will be willing to take a chance on the initial experiments and pay to have one of the initial payloads. We might do crowd funding where $50,000 gets you 1 Kg and $400,000 gets 10 Kg. If we had 20 customers at $400,000 each that would be $8 mil which could be a big help in covering the development and mission costs. It is an interesting enough project that crowd funding could work well, might raise far more than the goal. We can easily scale this up to larger payload sizes once this one works reliably. References and further reading https://grokipedia.com/page/sun-synchronous-traversal https://x.com/i/grok/share/QuGxmEgHXVr501seGMVCFdJgi Tether Rendezvous Timing Tables https://grokipedia.com/page/Momentum_exchange_tether https://grokipedia.com/page/Space_tether https://www.desertworkspropulsion.com/tie TIE-20 Gen 2 Thruster http://spacetethers.com/moon-l5/ Moon-L5 Tether System: Revolutionizing Space Economics