Author Topic: Two Stage Tether to Orbit Launch System  (Read 6629 times)

Offline RanulfC

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Re: Two Stage Tether to Orbit Launch System
« Reply #15 on: 10/31/2012 02:55 PM »
The FAA does not allow commercial use of UAVs at this time. They do allow experimental UAVs with a permit.
http://www.faa.gov/about/initiatives/uas/uas_faq/
Nice to know.
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I don't know the FAA rules for tethered aircraft. There are tethered aerostats deployed in the southern USA (http://en.wikipedia.org/wiki/Tethered_Aerostat_Radar_System).
Hmmm, it would probably be considered a similar type of "tethered airborne object" I suppose.
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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.

Not that much of a difference really for the low altitude tether though it is?
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There are a few potential applications that might attract some early R&D funding to develop electric air freight:

1) Military air freight using UAVs launched by tethers. Air transport would avoid the risks of ground convoys, and lower fuel costs with cheap electric propulsion. Jet fuel is a huge cost for the military.
We've a couple of thread in the "Advanced Concepts" section on Solar Power Satillites to replace "imported" fuels for Forward Operating Bases :)

I guess it could be used as a supplement to air-cargo shipments. This is the point where trials would really really help.

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2) Mining companies could use the system to transport ores from remote locations. Electric air transport could be cheaper than building roads or rail connections to the mine site.
I'd have to see some numbers for this one. The majority of "mining" companies are going to need roads/rails simply to get their equipment into place and they WANT an initial two-way capability.
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Space launch is a more speculative proposition. We have to prove the concept at lower speeds before trying to build a hypersonic tether.
Agreed overall, but I actually believe that the electric air launch is MORE "speculative" given the already in-place dynamics of the air transport business. The idea of carrying more payload at take off, or saving fuel is good but nothing I've seen yet makes a convincing case that airlines would be interested in the required changes needed to operations and aircraft design to make the system work. Space Launch has the "benifit" of not having as much 'sunken' costs into a pre-existing system. Specifically it allows more optimized "above-the-speed-of-sound" designs for upper stages without being to constrained by the need for a large, specially designed carryier aircraft. Along with this is the ability/benifit of NOT being restricted to a specific launch azmith as in most other launch assist concepts. Lastly the possible "through-put" or cargo on a daily basis is pretty fantastic.
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Note the dynamic pressure is relatively low for the higher segments of the wing tether. The maximum dynamic pressure would occur between 30,000-40,000 feet in altitude at subsonic velocity. The tow aircraft would be flying at these altitudes. The aerodynamic stress on the high altitude tether should be quite low.
My major "concern" was the shockwave impingment on the payload as the "shock-cone" narrowed down at higher speeds/altitudes. But again this is something that needs testing.

Thanks for your answers. Keep us updated :)

Randy

Offline johncarpinelli

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Re: Two Stage Tether to Orbit Launch System
« Reply #16 on: 11/02/2012 06:18 AM »
Randy,

Electric aviation is going to be more beneficial to humanity than space-launch in the coming decades. We have to deal with climate change and developing transport without oil. Space tourism is a nice-to-have industry. Not essential for life on Earth. To get really cheap space flights (e.g. $10 per kg), you have to amortize capital costs with aviation anyhow.

Here's a link to a spreadsheet with some basic economics for the electric air freight concept. You can adjust parameters like the glide ratio and the electric power cost to see the impact on the overall fuel cost per tonne-mile.

https://docs.google.com/spreadsheet/pub?key=0ArN3BBRS37YcdHVkTGN0dl81NWFFSDdWcDBaTDd0MlE&output=xls

There are a few different business models that might work. I personally like the concept of point-to-point air freight using drones. Matternet have a nice video of this vision.

http://matternet.us/our-vision/

Here are some other hypothetical revenue sources to get started.

- Tourist joy rides to the edge of space. We could tow tourists up to 100,000+ feet so they can enjoy the "overlook" effect with a dark sky above them.

- Pilot training. To reduce the fuel costs of pilot training, aircraft could be towed to altitude. This would be helpful for aircraft with high fuel consumption.

- NASA / ESA / JAXA. The Japanese space industry seems particularly interested in space elevators, so perhaps they could see this as a viable alternative.

- Parachuting / parasailing. A small scale system could tow parachutists to jumping altitude. Tourists are already towed by boats for parasailing rides. This could be a variant for tourists in scenic areas away from the sea (e.g. the Grand Canyon, Las Vegas etc.)

- Mining/Fishing/Timber/Agriculture. Bulk air transport for resources in remote locations using tether launched drones.

- Media. A reality TV series documenting the development of the system. Towed advertising banners could bring revenue.

It should not require billions of dollars to get most of these concepts to cash-flow positive operation.

John

Offline RanulfC

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Re: Two Stage Tether to Orbit Launch System
« Reply #17 on: 11/02/2012 07:20 PM »
Randy,

Electric aviation is going to be more beneficial to humanity than space-launch in the coming decades. We have to deal with climate change and developing transport without oil. Space tourism is a nice-to-have industry. Not essential for life on Earth. To get really cheap space flights (e.g. $10 per kg), you have to amortize capital costs with aviation anyhow.

Here's a link to a spreadsheet with some basic economics for the electric air freight concept. You can adjust parameters like the glide ratio and the electric power cost to see the impact on the overall fuel cost per tonne-mile.

https://docs.google.com/spreadsheet/pub?key=0ArN3BBRS37YcdHVkTGN0dl81NWFFSDdWcDBaTDd0MlE&output=xls

There are a few different business models that might work. I personally like the concept of point-to-point air freight using drones. Matternet have a nice video of this vision.

http://matternet.us/our-vision/

Here are some other hypothetical revenue sources to get started.

- Tourist joy rides to the edge of space. We could tow tourists up to 100,000+ feet so they can enjoy the "overlook" effect with a dark sky above them.

- Pilot training. To reduce the fuel costs of pilot training, aircraft could be towed to altitude. This would be helpful for aircraft with high fuel consumption.

- NASA / ESA / JAXA. The Japanese space industry seems particularly interested in space elevators, so perhaps they could see this as a viable alternative.

- Parachuting / parasailing. A small scale system could tow parachutists to jumping altitude. Tourists are already towed by boats for parasailing rides. This could be a variant for tourists in scenic areas away from the sea (e.g. the Grand Canyon, Las Vegas etc.)

- Mining/Fishing/Timber/Agriculture. Bulk air transport for resources in remote locations using tether launched drones.

- Media. A reality TV series documenting the development of the system. Towed advertising banners could bring revenue.

It should not require billions of dollars to get most of these concepts to cash-flow positive operation.

John
Going to take the weekend to review the pdf, (can't open it here) and the rest before I comment. Thanks.

Randy

Offline Solman

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Re: Two Stage Tether to Orbit Launch System
« Reply #18 on: 02/26/2013 07:37 PM »
 What if you had the winged hypersonic component of this system carry a chemical rocket powered upper stage?
 Less payload and adds cost of an upper stage, but no need to have the orbital tether component.

Offline RanulfC

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Re: Two Stage Tether to Orbit Launch System
« Reply #19 on: 02/27/2013 12:24 PM »
What if you had the winged hypersonic component of this system carry a chemical rocket powered upper stage?
 Less payload and adds cost of an upper stage, but no need to have the orbital tether component.
Initially you have to have a rocket component to help build up the tether, but your payload is going to be very, very low. With the tether your required delta-V is much less so more of your vehicle can be payload.

With matched timing you get a launch opportunity about every 90 minutes.

The orbital tether is an additive system like any other large transportation system.
(Pretty much the same for the ground based system.)

Any updates there johncarpinelli?

Randy

Offline johncarpinelli

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Re: Two Stage Tether to Orbit Launch System
« Reply #20 on: 02/27/2013 11:06 PM »
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.

Offline RanulfC

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Re: Two Stage Tether to Orbit Launch System
« Reply #21 on: 02/28/2013 04:14 PM »
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.
Might find some helpful stuff here:
http://forum.nasaspaceflight.com/index.php?topic=25095.0;all

(Jet Powered First Stage thread)

Once the lower-stage is up and running you could launch ramjet/rocket vehicles from the upper-tether.
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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.
Hmmm, hear of the "Princton Sail-Wing" at all?
http://www.dtic.mil/cgi-bin/GetTRDoc?AD=AD0275307
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19790015726_1979015726.pdf
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19690009905_1969009905.pdf
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19670021814_1967021814.pdf
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19740008656_1974008656.pdf

The idea is that a solid "leading-edge" shape wrapped with cloth or other flexable material and around a tension stiffened wire as a "trailing-edge" takes on various required "shapes" as in aerodynamically needed at various points from standing still to what-ever the design speed is.

Not sure how you'd make the "leading" edge flexible yet able to support the "wing" but you might look into an inflatable tubular structure.

What kind of "kite" technology were you looking at by the way?

Randy

Offline Joel

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Re: Two Stage Tether to Orbit Launch System
« Reply #22 on: 05/25/2013 10:34 AM »
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.


Google has now gone from being an investor to acquiring Makani. It might lead to significantly accelerated research.
http://news.cnet.com/8301-1023_3-57585834-93/google-x-acquires-kite-power-startup-makani/

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/
"Success is stumbling from failure to failure with no loss of enthusiasm." - Winston Churchill

Offline Joel

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Re: Two Stage Tether to Orbit Launch System
« Reply #23 on: 05/25/2013 11:50 AM »
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.

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.
"Success is stumbling from failure to failure with no loss of enthusiasm." - Winston Churchill

Offline johncarpinelli

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Re: Two Stage Tether to Orbit Launch System
« Reply #24 on: 05/26/2013 06:48 AM »
That is good news about Makani being acquired. Google has much greater resources and will hopefully scale up the technology. I would love to see them deploy the system commercially.

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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/

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?

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1. Using solar power is a complete non-starter. Wind power at these altitudes is extremely abundant and very consistent.

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.

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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.

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/

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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 disagree. The tether will be a light-weight inflatable wing that flies above conventional airspace (e.g. at 30 km). If the system fails, the tether will slow as it descends into the thicker atmosphere at low altitudes. It will flutter harmlessly to the ground and should cause minimal damage.

Offline Joel

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Re: Two Stage Tether to Orbit Launch System
« Reply #25 on: 05/26/2013 09:46 AM »
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?
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.

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.

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.

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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.

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.

The physics has a lot of similarity. Tethered flight is a tricky thing.

CyPhy Works is a new startup using tethered drones that looks promising.

http://cyphyworks.com/robots/

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/


The tether will be a light-weight inflatable wing that flies above conventional airspace (e.g. at 30 km).

Rigid airfoils are superior to inflatable wings when it comes to supporting forces.
"Success is stumbling from failure to failure with no loss of enthusiasm." - Winston Churchill

Offline johncarpinelli

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Re: Two Stage Tether to Orbit Launch System
« Reply #26 on: 05/26/2013 06:54 PM »
The tether from hub to tow aircraft would support both tension and electricity. I understand how you could pump the aircraft higher by increasing tension on the tether. To keep the aircraft circling the hub, you would need to have a tow vehicle on the ground moving in a circle.

One option would be to use a car or truck to drive in a circle on a flat plain like a salt lake. We discussed that concept earlier in the thread.

Another option would be to use a boat to tow the tether in a circle. This is similar to para-gliders being towed by boats at tourist beaches.

Towing the tether from a ground vehicle would be a cheap way to test tether designs, but it would complicate the process of attaching a payload to the tether. The payload would have to be on the ground vehicle prior to startup of the system.

http://www.ampyxpower.com/ looks very promising. I hope they succeed.

Offline cordwainer

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Re: Two Stage Tether to Orbit Launch System
« Reply #27 on: 05/29/2013 08:21 PM »
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.

Offline Joel

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Re: Two Stage Tether to Orbit Launch System
« Reply #28 on: 05/29/2013 10:06 PM »
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.

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...
"Success is stumbling from failure to failure with no loss of enthusiasm." - Winston Churchill

Offline RanulfC

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Re: Two Stage Tether to Orbit Launch System
« Reply #29 on: 05/30/2013 07:05 PM »
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.

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...
"Soft" airfoils have been extensivly tested before. One example I pointed out before was the "Princton Sailwing" design:
http://www.dtic.mil/cgi-bin/GetTRDoc?AD=AD0275307

(Note: I had originally included several NTRS links on studies done by NASA on the Sailwing. However it now seems that none of them are working and that the data has been removed from NTRS at this time. They are included here again JUST in case they should begin working again as some point:
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19790015726_1979015726.pdf
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19690009905_1969009905.pdf
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19670021814_1967021814.pdf
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19740008656_1974008656.pdf
End Note)

Several other inflatable or soft airfoils have been suggested in past posts also. My suspicion at this point is the "ribbon" would be some sort of hybrid with the power supply cables and supports making up the main "hard" sections with inflated or air supported sections of very light weight materials in between making up the majority of the surface.

Some other points:
1. Using solar power is a complete non-starter. Wind power at these altitudes is extremely abundant and very consistent.
The concept is a tether-and-tow-aircraft/motors flying a powered circle and 'towing' an extended tether/mass that is a larger circle whose tip speed enters the hypersonic speed range. You can't really "extract" wind energy under those conditions.

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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.
Not AWE compatible due to the required powered nature of the concept. AWE requires tapping a "drag" factor of an airfoil or airfoils interaction with upper atmospheric winds. This concept uses the "lift" of an aerodynamic tether to offset the mass of the tether and allow a "payload" to advance up the tether while gaining energy from the rotational motion of the system. Since this motion has to be provided by the system this requires a powered segment to move the system in a circular motion.

While some AWE work is relevent this is a very different system and concept from most AWE systems and there is very limited crossover due to those system requirement differences.

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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've suggested that option for very different reasons but in general since the system is "powered" at all times and the tethers are going to have to be aerodynamic as well as stong and light there are many more options for safely lowering, landing, or crashing the system if needed.

For example the powered tow-plane will have an emergency on-board power source in case of a power failure or break in the power tether which will allow it to continue flying as required long enough to retract and store the upper tether and reel-in and land with the lower tether segment if needed.

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.
The concept uses a tether in tension (IIRC from the cited paper someting like several hundred TONS of tension in fact) AND transmitting electricty to a powered "tow" vehicle (aircraft) that is then used to "drag" another aerodynamic tether in an even larger circle to build up and store potential energy to be transfered to a payload moved along the tether by a transfer vehicle.

At some pre-determine point along the upper atmospheric tether the payload is released in a subsonic, supersonic, or hypersonic glide/trajectory having used no on-board power.

Since the system requires input power at a steady rate and must not only support that propulsion system but a "towed" upper atmosphere tether simple "drag" aerodynamic flight is not sufficent to power the system and active input is needed.

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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.

Not compatabile with the system being discussed which requires an ACTIVE propulsion source to provide steady thrust to power the system dynamics. Kites would not work.

The physics has a lot of similarity. Tethered flight is a tricky thing.
In general yes, in specifics not so much as the MAJORITY of the work (especially AWE) is based on totally different flight physics as well as propulsion and system management. Since this system is powered in a manner similar to the cited system and avoids as much as possible "interaction" with upper atmospheric winds some tether dynamics can be applied to lower power/energy portions of the system, but that's about all.

On the other hand considering the requirements for meeting the aerodynamic, weight and strength goals of this system, AWE sytems will greatly benifit from research and testing of this system.

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/
Actually the "cables" are extremly light weight designs for the power they carry which I believe was the point :)

The PARC quad-copter isn't really applicable to this system either I'd say. It wouldn't work well for the forward speed and towing needs. Something more like the EASY ring-wing drone would be more applicable I think in that once airborne and on-station the entire thrust of the vehicle can then be devoted to towing duty unlike the quad-copter design.
http://cyphyworks.com/robots/ease/

Rigid airfoils are superior to inflatable wings when it comes to supporting forces.
Normally but they have a mass penalty as well as an inflexability that preclude their consideration for this purpose.

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.
Is there such a thing as a "high-speed-aerostat"? LTA flight is pretty limited as to speed obtainable without serious power and/or constant transition shapes.

There are a couple of other concepts out there using very-high-speed cable systems as well as magnetically accellerated/controlled enclosed "pellet" systems for launch assist/launch purposes. Scaling them down to "demonstration" or "research" sizes is a bit of an issue though :)

As we've discussed previously here the inital testing and vetting of the concept can be done at a fairly low "garage/hobby" level really. So it should be pretty cost effective to test and refine.

Randy

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