 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
| HomeDiscussion GroupsSpace ScienceAstronomyAmateur AstronomySpace FlightSpace StationShuttleSpace HistorySpace PolicySETI SpaceKB.com Contact UsLink To UsSearch & Site Map |
Space Forum / Space Flight / February 2006Sling launch from lunar surface
Proposed system to launch raw materials from the lunar surface to escape velocity: At the top of a 160 meter tall tower is a platform rotating at 100 rpm. Attached to the platform are two 160 meter tethers, also spinning, with the acceleration at the tips of the tethers = 1790 gees. One kg payloads of raw material slide 'down' each essentially-horizontal tether and are released at lunar escape velocity. Assuming a launch rate of about 1kg/second (3.6 ton/hr), the power consumption is less than 3MW. No super-conducting, complex, reusable 'buckets' required, as would be for a linear magnetic mass driver. The biggest concern would be wear on the tethers. Perhaps this could be handled by having an aluminum hollow cylinder bushing at the core of each payload and current running down the cable so magnetic levitation would keep the payload from contacting the tether. Perhaps the tower could be eliminated if each tether has a maglev 'car' at the tip, riding on a 1 km circumference passive aluminum track. The 'cars' and track would support the tethers during down time. wbogen@visteon.com wrote in news:1138288465.715089.213180 @g14g2000cwa.googlegroups.com: What are the tethers made of that they can instantly impart several km/sec of velocity to that mass? Something's got to give. --Damon In sci.space.tech Damon Hill <damon1six1@comcast.not.retro.com> wrote: > wbogen@visteon.com wrote in news:1138288465.715089.213180 > @g14g2000cwa.googlegroups.com: > > What are the tethers made of that they can instantly impart > several km/sec of velocity to that mass? Something's got > to give. The payload slides down the tether, and gradually accellerate. Good idea. But why not reel the tether out while accelerating? You have a tower with a tether drum on top. While at rest, the tether is mostly reeled in and the payload can be attached to the tip. During acceleration, you reel out the tether. That reduces g-loads on the payload and you do not have anything sliding along the tether. Since a rotating tether in a vacuum is a very efficient energy storage device, you could take as long as you want to spin up the tether, depending on available power. You could even use it as a battery in the night. If the tower is high enough (approx. 1km) you can reduce tip acceleration to a survivable level to launch soft payloads such as humans. It certainly makes much more sense than an electromagnetic accelerator. You have energy storage built in and you have the potential to launch soft payloads. > Proposed system to launch raw materials from the lunar surface to > escape velocity: I do know that the space settlement researchers talked about a "rotary pellet launcher" for the moon before they later hit on the idea of the mass-driver. I would assume they dumped it for the mass-driver for one advantage or another. But I suppose it could be that what you're proposing might be significantly different from their rotary pellet launcher concept.  SignatureRegards, Mike Combs ---------------------------------------------------------------------- By all that you hold dear on this good Earth I bid you stand, Men of the West! Aragorn No difference. This is the old rotary pellet launcher. The problems are friction, too much of, and accuracy, not enough, by a lot. With a 160m high tower, able to support latera; forces, such a launcher would mass more than a linear accelerator (also about 160m long). If the tether could be played out and reeled in, then the tower could perhaps be only 10m high, and this does become a possibility. However, I think there will be accuracy problems - hitting a catcher in space would require the release to be perfectly timed - I suspect nano second level precision. So this would require launching cargoes with their own guidance and propulsion. This puts up the minimum weight into the multi kilo level. Next, do the two tethers release their payloads at same time? In which case they'll go on different orbits - one may be optimised, but you can't do both. Then you have to manage how the raw materials "slide" down the tether. The tether will bemd, and the materials will have both tangential and radial velocity. This is all possible, though you might as well go for a simple mass driver. > With a 160m high tower, able to support latera; forces, such a launcher > would mass more than a linear accelerator (also about 160m long). > > If the tether could be played out and reeled in, then the tower could > perhaps be only 10m high, and this does become a possibility. Another possibilty is to have sloping, rotating 160m-long arms to support the tethers up to maybe 3 RPM. At that point, the tethers will rise from the supports to a more horizontal position and continue speeding up to 100 RPM. I prefer the maglev 'car' at the ends of the tethers, riding on a track. The major point of using this system versus an electromagnetic mass driver is avoiding complex and expensive buckets. > However, I think there will be accuracy problems - hitting a catcher in > space would require the release to be perfectly timed - I suspect nano > second level precision. So this would require launching cargoes with > their own guidance and propulsion. This puts up the minimum weight into > the multi kilo level. I think the tether could be made to vary the friction on the payload to help time the release and, as I think electromagnetic mass driver proponents have suggested, lasers beyond the release point could zap the payload and tweak the trajectory. > Next, do the two tethers release their payloads at same time? In which > case they'll go on different orbits - one may be optimised, but you > can't do both. No, the tethers don't release simultaneously; we could have an off-center mass oscillating near the center of the platform, acting as a counterbalance to the payloads being released every 1/2-revolution. > Then you have to manage how the raw materials "slide" down the tether. > The tether will bemd, and the materials will have both tangential and > radial velocity. I'm not sure how much the tether will bend; the maglev 'car' at the end may mass a lot more than a payload and keep the tether taut. I'm planning on giving the payloads both a radial and tangential velocity (roughly equal); if we slowly 'lowered' the payload to the tether end and then released it with only a radial velocity, we'd need a 226m long tether. > This is all possible, though you might as well go for a simple mass > driver. Again, it's the superconducting 'buckets' that make a 'simple' mass driver not so simple. > , as I think electromagnetic mass driver > proponents have suggested, lasers beyond the release point could zap > the payload and tweak the trajectory. I think you mean electron beams. > Again, it's the superconducting 'buckets' that make a 'simple' mass > driver not so simple. I've been wondering recently if Halbach Arrays of permanent magnets might could replace the superconducting coils of a mass-driver bucket. I do know they can be arrayed in toroidal shapes. SignatureRegards, Mike Combs ---------------------------------------------------------------------- By all that you hold dear on this good Earth I bid you stand, Men of the West! Aragorn > > , as I think electromagnetic mass driver > > proponents have suggested, lasers beyond the release point could zap [quoted text clipped - 8 lines] > could replace the superconducting coils of a mass-driver bucket. I do know > they can be arrayed in toroidal shapes. Here's a partially-baked idea for a mass driver that has: 1) no contact, and so no friction, between payload and driver; 2) no need for high-tech containers (ex; with super-conducting coils); 3) no need to separate payload from container or recycle the containers. Look at the simple toys that use an electromagnet above an iron-bearing toy (ex; a small globe) to lift it upwards. As the toy approaches the magnet it blocks a light beam which causes the magnet to reduce the upward force. Result: the toy hovers beneath the magnet. Voila, poor-man's levitation. Now imagine 1kg payloads of regolith/ore/whatever placed in cheap standard steel cans. The cans are pushed beneath a long (160m or so) rotating (100 RPM) arm covered with electromagnets and optical sensors. Each can is pulled toward a magnet on the arm but the sensor keeps it from quite reaching the magnet. Centrifugal force (yes, I know, a useful illusion) pushes the can down the arm to the next magnet that tugs on it, accelerating it to the speed of that segment of the arm. Information on the mass and magnetic qualities of each can are sent to the next magnet down the arm to set the initial force of that electromagnet. The magnets would have to strongest at the tip of the arm where the can would have to be pulled 'up' at 1790 gees while the first magnet would only pull at 1/6 gee. Each can picks up both radial and tangential velocities and leaves the arm at lunar escape velocity. Obviously the tricky part is making the magnet control response fast enough. This isn't terribly different from the rotary pellet launcher originally proposed. Dr. Valentine has already confirmed that there were valid reasons for dropping it in favor of the later mass-driver proposal. SignatureRegards, Mike Combs ---------------------------------------------------------------------- By all that you hold dear on this good Earth I bid you stand, Men of the West! Aragorn > I've been wondering recently if Halbach Arrays of permanent magnets might > could replace the superconducting coils of a mass-driver bucket. I do know > they can be arrayed in toroidal shapes. Dr. Valentine, did you have any opinion on the above? I was hoping to hear your comments. SignatureRegards, Mike Combs ---------------------------------------------------------------------- By all that you hold dear on this good Earth I bid you stand, Men of the West! Aragorn > Proposed system to launch raw materials from the lunar surface to > escape velocity: > > At the top of a 160 meter tall tower is a platform rotating at 100 rpm. > Attached to the platform are two 160 meter tethers, also spinning, > with the acceleration at the tips of the tethers = 1790 gees. One kg hmmmmm, I wonder, is there any reason why the tether cannot be horizontal? maybe not perfectly horizontal but a possible conical setup? would use a shorter tower, or a hill of correct size. |
Reply to this Message |
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2009 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.