Good idea about using chemical rockets for the upper stage. The atmospheric lower stage is the first part of the project. Once it's in operation, you should have significantly cheaper launch with chemical rockets. You could use that capability to build up the orbital stage.
Latest updates:-Submitted the design in a proposal to NIAC NNH13ZUA001N this month.-Working on a prototype wing tether constructed with sheets of polyethylene, balsa wood and packing tape. All suggestions and feedback are appreciated. Building a stable wing tether is harder than it sounds. There are some similarities with kite-building, but I've not seen a kite design that meets our specific requirement.
Makani Power has demonstrated tethered flight with their 8m 58kg prototype flying wing. Their drone flies in a vertical circle to capture wind power, whereas our design needs a horizontal circle.
All suggestions and feedback are appreciated. Building a stable wing tether is harder than it sounds. There are some similarities with kite-building, but I've not seen a kite design that meets our specific requirement.
Note that you don't need to have any electric propellers. An alternative approach is to use the "inverse pumping mode" to keep the airfoil afloat using a linear generator on the ground. If you are interested in the trajectory optimization and control of tethered airfoils, my research group has open-source software for this:http://homes.esat.kuleuven.be/~highwind/
1. Using solar power is a complete non-starter. Wind power at these altitudes is extremely abundant and very consistent.
3. What you are proposing has a lot of similarity with airborne wind energy (AWE), and research in this field goes back 30 years. You really should try to leverage that.
5. You need to put ground station off-shore and have restricted airspace. These stuff are potentially very dangerous so you don't want to put them anywhere near populated areas.
I don't understand how this would help the electric takeoff proposal. We need thrust at high altitude to tow the tether. I don't think it could be provided from the ground. Can you elaborate?
The solar panels are deployed on the ground and electricity is transmitted along the tether to the tow aircraft. Electricity gives you flexibility in combining wind, solar, hydro and other energy sources. This would be useful for remote locations (e.g. Australian outback) to provide clean air transport. A major goal of the technology is to move aviation away from fossil fuels.
Quote3. What you are proposing has a lot of similarity with airborne wind energy (AWE), and research in this field goes back 30 years. You really should try to leverage that.I have not seen much research on tethered electric tow aircraft for point-to-point transportation. Nate Saint was using circular flights in the 1950's to exchange packages with the ground. I do not know of any commercial use of tethered electric aviation for transport.
CyPhy Works is a new startup using tethered drones that looks promising.http://cyphyworks.com/robots/
The tether will be a light-weight inflatable wing that flies above conventional airspace (e.g. at 30 km).
Doesn't seem feasible without the use of a high-speed aerostat or rigid airfoil. A Lofstrom Loop seems more likely given current tech, even if it might be more expensive.
Quote from: cordwainer on 05/29/2013 08:21 pmDoesn't seem feasible without the use of a high-speed aerostat or rigid airfoil. A Lofstrom Loop seems more likely given current tech, even if it might be more expensive.Makani was working on soft kites for several years, before they realised that rigid airfoils is the only reasonable way forward... But of course, if they crash, they can easily kill someone on the ground...
Some other points: 1. Using solar power is a complete non-starter. Wind power at these altitudes is extremely abundant and very consistent.
2. Flying these giant circles that you are proposing will suffer from too much tether drag. Consider having the cable split up into two airfoils higher up (a.k.a. "dancing kites"). This will limit the amount of tether exposed to fast crosswind.3. What you are proposing has a lot of similarity with airborne wind energy (AWE), and research in this field goes back 30 years. You really should try to leverage that.4. AWE is feasible up to very high altitudes since the weight of the cable is small compared to the amount of lift generated. Joby Energy (www.jobyenergy.com), whose airborne wind energy department has now merged with Makani, wanted to put tethered airfoils in the jet stream (~10 km). You can probably go significantly higher than that.
Maybe I didn't understand the idea fully. So the cable that goes from the electric aircraft to the ground is not able to support any tention, only transmit electricity? An alternative is to have a cable that can support tention, but not necessarily electricity and then "pump" the aircraft to higher altitudes. It's the inverse of the pumping cycle for AWE http://homes.esat.kuleuven.be/~highwind/?p=36.
Or, you can use a cable that can transmit tension, flying it like a kite, in which case you hardly need any power at all.
The physics has a lot of similarity. Tethered flight is a tricky thing.
From what I can see, that is just a quadcopter with a power cable. I'd rather have a look at Makani or the other companies in AWE, such as http://www.ampyxpower.com/
Rigid airfoils are superior to inflatable wings when it comes to supporting forces.
Aerodynamic lift like a kite or a paraglider. The wing can fly higher than the tow vehicle. Consider a paraglider towed by a boat for an example. http://www.towmeup.com/