Author Topic: Two Stage Tether to Orbit Launch System  (Read 7655 times)

Offline johncarpinelli

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Two Stage Tether to Orbit Launch System
« on: 09/08/2012 04:13 PM »
A two stage orbital launch system is proposed.  The system can be constructed using commercially available tether materials.  The lower tether is propelled by electric tow aircraft powered by grid electricity. The end of the lower tether is travelling at 3 km/s with a
radius of 400km.  The upper stage is an orbiting electrodynamic tether powered by solar electricity.  The payload ascends the lower tether using hub mounted winches and then accelerates due to centripetal force.  The payload transfers to the upper tether using a grappling mechanism and then accelerates to orbital velocity using momentum transfer.

Launch costs around $10 per kg assuming primary revenue is from aviation.

Presentation from Space Elevator conference:

https://docs.google.com/presentation/pub?id=1vn5SkM6x6uZ4YMb3hNc_MmIvS6WOmXWLUsz2X8cPL6A&start=false&loop=false&delayms=3000#slide=id.p14

Paper:

http://electrictakeoff.com/wp-content/uploads/2012/08/Two-Stage-Tether-to-Orbit.pdf

Offline mboeller

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Re: Two Stage Tether to Orbit Launch System
« Reply #1 on: 09/09/2012 04:44 PM »
Hi;

what about environmental issues? The Space-Launch Tether travels at up to 3km/sec so the sonic boom could be very strong from the portion of the tether still traveling in the denser atmosphere, or?

Offline A_M_Swallow

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Re: Two Stage Tether to Orbit Launch System
« Reply #2 on: 09/09/2012 11:44 PM »
The fast moving parts of the tether are very high in the atmosphere, where there is little air, so the boom should be quiet.

Electric planes.  The propellers could be powered solely by electric motors.  During deployment the power could be supplied by electrical generators burning jet fuel.  Once deployed they can then switch to mails electrical power.

Offline mboeller

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Re: Two Stage Tether to Orbit Launch System
« Reply #3 on: 09/10/2012 10:34 AM »
When the tether reaches 3000 m/s at a distance of 400km from the base then the tether will reach supersonic speed within 40km of the base. Do you expect that the tether is above 25-30km height at this distance?

By the way, the TOW aircraft would travel at a speed of only 135 km/h at 10km height. I think this is not possible, it would stall. (5km/400km x 3000m/sec = 37,5 m/sec)

Offline alexterrell

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Re: Two Stage Tether to Orbit Launch System
« Reply #4 on: 09/10/2012 12:56 PM »
This is very interesting as the main cost is fast coast to coast traffic.

So, could someone build this for hypersonic travel only, and justify the cost on this basis? The presentation gives $500 million capital costs for hub (stage 1), which is trivial compared to the development of a hypersonic airliner, or even a Boeing 787 or Airbus A800.

However,
- This concept is still going to need a hypersonic plane - expensive even without hypersonic engines.
- What is the time frame to get to launch point and does that negate the benefits of the hypersonic launch?
- The big market could be US coast to coast and trans Atlantic, but for space operations an equatorial launch is best.
- Hypersonic launch operations will need at least two centres to throw payloads at each other.

So is this viable?

An alternative is to build it for space travel from the start, and use it to pre-launch rockets (upper stages) at 3km/s.

Offline Solman

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Re: Two Stage Tether to Orbit Launch System
« Reply #5 on: 09/11/2012 12:40 AM »
 Another alternative is to increase the length of the upper tether to raise its center of mass and lower its orbital velocity and at the same time increase its mass so that it could handle bigger payloads. I'm assuming the upper tether is the "hanging" type that trades altitude for momentum when a payload moving below orbital velocity is attached (because I couldn't open the files - computer issue). If it is, then with available materials perhaps it could reach a length such that its orbital velocity reached Concorde speeds. Perhaps it could travel in an elliptical orbit so that it could dip to an altitude low enough to snag a supersonic airliner or payload released from one and use its EM to make up for the drag before apogee.
 It could be lengthened over time with second stages being the initial first stages to deliver payloads to the ED tether to save some velocity and give existing launchers a higher payload.

Offline Robotbeat

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Re: Two Stage Tether to Orbit Launch System
« Reply #6 on: 09/11/2012 10:16 PM »
Well, this concept seems unfeasible to me, but I'm really glad other concepts are being considered, here. Orbital tethers have a lot of potential (heh).
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Offline RanulfC

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Re: Two Stage Tether to Orbit Launch System
« Reply #7 on: 09/19/2012 06:21 PM »
It's definiatly an interesting concept. I have issues with a lot of the "assumptions" (especially aviation as a "driver" for the economics) but nothing seems to rear its head as a show-stopper.

I also like how it's pointed out that a lot of the "ground-work" can be laid out by non-professionals at a reasonable cost. (I could see a "proof-of-concept" type set up with a barely sub-supersonic end-tip being in the high end model aircraft range)

Another alternative is to increase the length of the upper tether to raise its center of mass and lower its orbital velocity and at the same time increase its mass so that it could handle bigger payloads. I'm assuming the upper tether is the "hanging" type that trades altitude for momentum when a payload moving below orbital velocity is attached (because I couldn't open the files - computer issue).

I know the feeling it took me this long to get BOTH files opened and readable in the same place :)

No actually the upper tether is a rotating one, with electrodynamic propulsion based on the HASTOL concept.

Randy

Offline Andrew_W

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Re: Two Stage Tether to Orbit Launch System
« Reply #8 on: 09/19/2012 07:31 PM »
I'm no expert, but I'm skeptical about the tether being stable and not flipping over and spiraling along its length as a ribbon will if it's held across the wind.
« Last Edit: 09/19/2012 07:32 PM by Andrew_W »
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Offline RanulfC

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Re: Two Stage Tether to Orbit Launch System
« Reply #9 on: 09/19/2012 09:04 PM »
I'm no expert, but I'm skeptical about the tether being stable and not flipping over and spiraling along its length as a ribbon will if it's held across the wind.
Used to have a "toy" way back when that consisted of a weighted string with an "aerodynamic" covering around it. The cover rotated freely around the string and made a variety of noises as you whirled it around. I suspecet something similar would apply. But then again that's what needs "testing" anyway :)

I'm suspecting that some sort of mass will be required during deployment.

Randy

Offline johncarpinelli

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Re: Two Stage Tether to Orbit Launch System
« Reply #10 on: 09/21/2012 05:58 PM »
Hi,

Thanks for the feedback. Some clarifications below:

Sonic Boom - This should be minimal due to the low wing loading of the inflatable wing. The sonic boom overpressure is proportional to the wing loading and the tether will have a wing loading similar to an airship. The tether should reach Mach 1 at an altitude around 30km.

Note that the wing tether lags behind the tow aircraft. This concept is illustrated in slide 10 of the presentation. This means that the wing tether can gain high altitudes before it crosses the sound barrier.

The velocity of the tow aircraft depends on the radius of flight. This would be optimized for energy efficiency. For an aviation system, the tow radius would be smaller. For space launch, the radius can be extended to increase the tip velocity. The radius could be varied during flight.

The economics would depend on aviation as it's a proven market. A pair of launch systems could deliver freight for prices comparable to rail with lower capital costs. Another startup called Matternet (http://matternet.us) is developing drone based air freight. This could be a scaled up version for moving commodities (e.g. agriculture, minerals etc).

Hypersonic point-to-point travel would be a cool. Flying coast-to-coast in an hour with electric propulsion would be an awesome way to travel. I agree that developing hypersonic space planes will not be cheap.

Tether stability would depend on ballast and the horizontal stabilizer. Inflatable wings are a proven technology. Goodyear developed an inflatable aircraft for the army (http://en.wikipedia.org/wiki/Goodyear_Inflatoplane) as an example. A university group flew an inflatable wing at 100,000 feet also.

It will need funding to have professionals work on the concept. In the meantime, amateurs can build prototypes using model aircraft and prove some of the concepts at low velocities. It might be possible for amateurs to break the sound barrier with electric aircraft which would be a historic milestone.

John







Offline RanulfC

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Re: Two Stage Tether to Orbit Launch System
« Reply #11 on: 10/11/2012 03:56 PM »
Hi,

Thanks for the feedback.
You're quite welcome. Hope to hear more as you move forward :)

Quote
Some clarifications below:
Good 'cause I've got some questions as well :)

Lets start off with a rather "simple" one: The "assumed" positioning of the system is a land based flight facility near the equator. I've another "possible" location: How about an "ocean" based system? Using a "Pneumatically Stabilized Platform" System and a variable ballest system as a "hold-down" this would avoid many of the possible "conflict" issues with normal air traffic as well as simplifying some of the deployment issues. (Just a suggestion :o)
http://en.wikipedia.org/wiki/Pneumatic_stabilized_platform
http://tmp2.wikia.com/wiki/Pneumatically_Stabilized_Platforms_-_PSP
http://tmp2.wikia.com/wiki/Aquarian_SE_Downstation


Quote
Sonic Boom - This should be minimal due to the low wing loading of the inflatable wing. The sonic boom overpressure is proportional to the wing loading and the tether will have a wing loading similar to an airship. The tether should reach Mach 1 at an altitude around 30km.
30km is a bit over 98,000ft, and from what I understand sonic booms over 100,000ft most times don't reach the ground.

While the wing loading per segment is pretty low I'm wondering about the fact it's going to be a rather "two-dimensional" and very long supersonic footprint. That's going to make for some interesting aerodynamics and heating issues along the length :)

Quote
The velocity of the tow aircraft depends on the radius of flight. This would be optimized for energy efficiency. For an aviation system, the tow radius would be smaller. For space launch, the radius can be extended to increase the tip velocity. The radius could be varied during flight.
One thing I was struck by when I read up on the concept was that there seemt o be some "advantages" to the "variable" supersonic airflow along the upper tether. I recall some work done on supersonic ramjets using something similar to the "Busseman-Biplane" effect (IIRC the Napier in-wing ramjet for a proposed supersonic recon-bomber) as a rather simple but efficient engine. The problem was the "fixed" intake meant it was much LESS efficent at any speed above or below its "nominal" design speed.

Which seems to me would be much LESS of an issue for auxilary/momentum make up propulsion for the wing-tether segment of the concept. As an "added" bonus if electricity is supplied to upper tether segments the "heat-added" for the ramjets can be supplied by heating elements instead of having to have "fuel" for the ramjets.
Thoughts?

Quote
The economics would depend on aviation as it's a proven market. A pair of launch systems could deliver freight for prices comparable to rail with lower capital costs. Another startup called Matternet (http://matternet.us) is developing drone based air freight. This could be a scaled up version for moving commodities (e.g. agriculture, minerals etc).
IMHO I'm "iffy" on the idea of the economics being "dependent" on aviation as a market because I don't see this as actually offering enough incentive to the aviation industry to make the changes needed to embrace the concept. We're talking a lot of design changes to the basic aircraft frame along with new power plants and flying methods. I hope I'm wrong here but I suppose we'll have to "see" when something gets "flying" as it were.

Quote
Hypersonic point-to-point travel would be a cool. Flying coast-to-coast in an hour with electric propulsion would be an awesome way to travel. I agree that developing hypersonic space planes will not be cheap.
While the "time" factor would be a savings I agree I'm not so sure that hypersonic travel is all that "useful" for anything less than INTER-continential distances. Given the costs of designing and building a hypersonic aircraft and then building one capable of using the proposed concept...

Quote
Tether stability would depend on ballast and the horizontal stabilizer. Inflatable wings are a proven technology. Goodyear developed an inflatable aircraft for the army (http://en.wikipedia.org/wiki/Goodyear_Inflatoplane) as an example. A university group flew an inflatable wing at 100,000 feet also.
Do you happen to have a link to the information on the University group and thier inflatable wing? (Curious)

As I recall Goodyear even had proposals for "inflatable" space craft including a "Shuttle" type vehicle it would be interesting to see what research as done on heating and reentry stress' for such vehicles.

Quote
It will need funding to have professionals work on the concept. In the meantime, amateurs can build prototypes using model aircraft and prove some of the concepts at low velocities. It might be possible for amateurs to break the sound barrier with electric aircraft which would be a historic milestone.
I was actually thinking an electric control-line model would be an excellent "tow-plane" substitute and testing deployment methods for the towed-tether. Of course I'm also "thinking" that finding a place to do the testing might prove a bit of an issue even given a seriously scaled down version of the system :)

Thanks again for replying.

Randy

Offline johncarpinelli

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Re: Two Stage Tether to Orbit Launch System
« Reply #12 on: 10/11/2012 10:06 PM »
Hi Randy, Thanks for rekindling the discussion. My comments are below:

Quote
Lets start off with a rather "simple" one: The "assumed" positioning of the system is a land based flight facility near the equator. I've another "possible" location: How about an "ocean" based system? Using a "Pneumatically Stabilized Platform" System and a variable ballest system as a "hold-down" this would avoid many of the possible "conflict" issues with normal air traffic as well as simplifying some of the deployment issues. (Just a suggestion :o)
http://en.wikipedia.org/wiki/Pneumatic_stabilized_platform
http://tmp2.wikia.com/wiki/Pneumatically_Stabilized_Platforms_-_PSP
http://tmp2.wikia.com/wiki/Aquarian_SE_Downstation

Agree that an ocean based system would avoid issues with air-space. There's no technical reason the launch hub could not be deployed at sea. We only need a few hundred tons of ballast, so the platforms you suggest would work. To avoid toppling the floating vessel, you could deploy two tethers operating at a 180 degree offset. The tension of the two tethers would balance the lateral forces on the hub.

At sea, you will have higher costs for electric power and it would be more difficult to provide aviation services without a nearby airport. You could build the system on a remote island with an air-strip perhaps. Another possibility is for the navy to operate the launch hub from an aircraft carrier. The navy could offset costs for jet fuel with nuclear electricity generated onboard.

Quote
30km is a bit over 98,000ft, and from what I understand sonic booms over 100,000ft most times don't reach the ground.

While the wing loading per segment is pretty low I'm wondering about the fact it's going to be a rather "two-dimensional" and very long supersonic footprint. That's going to make for some interesting aerodynamics and heating issues along the length :)

I don't know how to model the sonic boom. An ocean based system would mitigate any noise issues, but I doubt the supersonic tether will be audible from the ground anyhow. The aerodynamics and heating are very difficult to model. Some physical prototypes are needed to prove the design. A computer model would have to consider aero-elasticity effects and flutter also. My personal preference is to build small scale prototypes to prove the concept.

Incidentally, if you want to break the sound barrier with a tether, it's not difficult. Just buy yourself a stockwhip. http://en.wikipedia.org/wiki/Stockwhip

Quote
One thing I was struck by when I read up on the concept was that there seem to be some "advantages" to the "variable" supersonic airflow along the upper tether. I recall some work done on supersonic ramjets using something similar to the "Busseman-Biplane" effect (IIRC the Napier in-wing ramjet for a proposed supersonic recon-bomber) as a rather simple but efficient engine. The problem was the "fixed" intake meant it was much LESS efficent at any speed above or below its "nominal" design speed.

Which seems to me would be much LESS of an issue for auxilary/momentum make up propulsion for the wing-tether segment of the concept. As an "added" bonus if electricity is supplied to upper tether segments the "heat-added" for the ramjets can be supplied by heating elements instead of having to have "fuel" for the ramjets.
Thoughts?
Are you proposing to extend the propulsion along the length of the wing tether? Transmitting electric power for ramjets would require heavy conductors embedded into the wing tether. I think the additional mass from the conductors would outweigh the benefits of deploying propulsion further along the tether. During deployment of the tether, each segment of the wing would need to operate at a gradually increasing velocity. It may be necessary to change the geometry of the tether as it climbs in altitude and increases velocity.

Quote
IMHO I'm "iffy" on the idea of the economics being "dependent" on aviation as a market because I don't see this as actually offering enough incentive to the aviation industry to make the changes needed to embrace the concept. We're talking a lot of design changes to the basic aircraft frame along with new power plants and flying methods. I hope I'm wrong here but I suppose we'll have to "see" when something gets "flying" as it were.
If a government agency is willing to fund the system for space launch only, it would be fantastic. However, the launch rate is limited by the time required to re-boost the orbiting tether. The wing tether would be idle for most of the time. Aviation is one alternative revenue source.

A very small scale system could be funded by aerial advertising. Companies already pay high rates for blimp advertising. If the FAA would allow tethered advertising, you could make money towing advertising banners on the tether at altitudes below 300 feet. Outdoor advertising is a $30 billion business in the USA.

Quote
While the "time" factor would be a savings I agree I'm not so sure that hypersonic travel is all that "useful" for anything less than INTER-continential distances. Given the costs of designing and building a hypersonic aircraft and then building one capable of using the proposed concept...
Agree that hypersonic travel is a long-shot. Let's park this idea for the long-term future. Richard Branson has expressed interest in point-to-point suborbital travel, so maybe there will be private funding for hypersonic vehicles after the tether is flying.
Quote
Do you happen to have a link to the information on the University group and thier inflatable wing? (Curious)
Here's a link to a report from the University of Kentucky:
https://imageserv5.team-logic.com/mediaLibrary/93/A_High-Altitude_Test_of_Inflatable_Wings_for_Low-Density_Flight_Applications.pdf

The project web-site is below. There were a few papers published from this research. They were researching the potential for aircraft flying on Mars with inflatable wings.
http://www.engr.uky.edu/bigblue/

Quote
As I recall Goodyear even had proposals for "inflatable" space craft including a "Shuttle" type vehicle it would be interesting to see what research as done on heating and reentry stress' for such vehicles.
Inflatable re-entry shields have been demonstrated by ESA and NASA.  For example, see the links below:
http://www.spaceflight.esa.int/irdt/factsheet.pdf
http://www.nasa.gov/home/hqnews/2012/jul/HQ_12-250_IRVE-3_Launch.html

Quote
I was actually thinking an electric control-line model would be an excellent "tow-plane" substitute and testing deployment methods for the towed-tether. Of course I'm also "thinking" that finding a place to do the testing might prove a bit of an issue even given a seriously scaled down version of the system :)
Agree that control-line models would be a small-scale method to demonstrate the system. However, you are limited by the strength of the human operator at the center of the control line. I don't like standing in the middle of my experiments as it makes me nervous! My prototype has an anchor winch mounted on a wooden turntable. It's very crude, but allows some basic testing and I can operate via remote control from a safe distance.

Another possibility is to test with a car or pickup truck. The vehicle would drive in a tight circle on a flat open surface. A passenger would deploy the inflatable wing from a winch. One possible test location is the Black Rock Desert on the playa. The air space is reserved for hobby rockets, so flying tethers might be allowed also. I am thinking about taking a road-trip there to test it out. Need to investigate the required permits first.

Example video of someone driving on the playa at 100 mph. Not sure if this is allowed.




I am going to give a ten minute talk on the Space Show this Tuesday (Oct 16th) at 1930 PST. Call-in if you'd like to join the discussion.

Offline RanulfC

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Re: Two Stage Tether to Orbit Launch System
« Reply #13 on: 10/16/2012 06:49 PM »
Hi Randy, Thanks for rekindling the discussion.
My comments are below:
No problem! It's an interesting concept :)

Quote
Agree that an ocean based system would avoid issues with air-space. There's no technical reason the launch hub could not be deployed at sea. We only need a few hundred tons of ballast, so the platforms you suggest would work. To avoid toppling the floating vessel, you could deploy two tethers operating at a 180 degree offset. The tension of the two tethers would balance the lateral forces on the hub.
I'm thinking it might also allow more than one "flight" operation at one time?
Quote
At sea, you will have higher costs for electric power and it would be more difficult to provide aviation services without a nearby airport. You could build the system on a remote island with an air-strip perhaps. Another possibility is for the navy to operate the launch hub from an aircraft carrier. The navy could offset costs for jet fuel with nuclear electricity generated onboard.
Well "one" idea I'd had was combining the system with an ocean platform that utilized OTEC (Ocean Thermal Energy Conversion) as a power system (you can find some information within the last two links I provided or here: http://www.otecnews.org/, or http://www.otecnews.org/portal/otec-articles/ocean-thermal-energy-conversion-otec-by-l-a-vega-ph-d/ ) this would help with the power genration and the fact that the tether system could "toss" various products to market helps a lot :)

As for providing aviation services, it could still provide those using seaplane based "aircraft" if need be in some ways that might actually be more "acceptable" especially for a demonstrator or test bed system.

The Navy is probably out though as I suspect the "system" would have issues if the "hub" had to do some radical manuvering which the Navy has a tendency to want to do. (Something about being a "moving" target I gather ;) )

Quote
I don't know how to model the sonic boom. An ocean based system would mitigate any noise issues, but I doubt the supersonic tether will be audible from the ground anyhow. The aerodynamics and heating are very difficult to model. Some physical prototypes are needed to prove the design. A computer model would have to consider aero-elasticity effects and flutter also. My personal preference is to build small scale prototypes to prove the concept.
Agreed actually :) I don't think either the sonic boom or heating will be all that much of an issue given the right design. However "I" certainly don't know how to model it so real-world testing the only way I see it being done and the fact that it CAN be done on a "small" scale helps a lot :)

Quote
Incidentally, if you want to break the sound barrier with a tether, it's not difficult. Just buy yourself a stockwhip. http://en.wikipedia.org/wiki/Stockwhip
LoL, well that's true... However it's only the "tip" and momentary at that, but it's a good point.

Quote
Quote
One thing I was struck by when I read up on the concept was that there seem to be some "advantages" to the "variable" supersonic airflow along the upper tether. I recall some work done on supersonic ramjets using something similar to the "Busseman-Biplane" effect (IIRC the Napier in-wing ramjet for a proposed supersonic recon-bomber) as a rather simple but efficient engine. The problem was the "fixed" intake meant it was much LESS efficent at any speed above or below its "nominal" design speed.

Which seems to me would be much LESS of an issue for auxilary/momentum make up propulsion for the wing-tether segment of the concept. As an "added" bonus if electricity is supplied to upper tether segments the "heat-added" for the ramjets can be supplied by heating elements instead of having to have "fuel" for the ramjets.
Thoughts?
Are you proposing to extend the propulsion along the length of the wing tether? Transmitting electric power for ramjets would require heavy conductors embedded into the wing tether. I think the additional mass from the conductors would outweigh the benefits of deploying propulsion further along the tether. During deployment of the tether, each segment of the wing would need to operate at a gradually increasing velocity. It may be necessary to change the geometry of the tether as it climbs in altitude and increases velocity.
It's possible that auxiliary or added propulsion might be needed so it was simply a thought. I highly suspect that the entire wing tether will have differing geometry but again that's something that will have to be looked into.

Quote
Quote
IMHO I'm "iffy" on the idea of the economics being "dependent" on aviation as a market because I don't see this as actually offering enough incentive to the aviation industry to make the changes needed to embrace the concept. We're talking a lot of design changes to the basic aircraft frame along with new power plants and flying methods. I hope I'm wrong here but I suppose we'll have to "see" when something gets "flying" as it were.
If a government agency is willing to fund the system for space launch only, it would be fantastic. However, the launch rate is limited by the time required to re-boost the orbiting tether. The wing tether would be idle for most of the time. Aviation is one alternative revenue source.
Well the "answer" is probably closer to "yes-and-no" than anything simple :)
(It seems that way anyway :) )

As a "space-launch" system even if only as an "assist" system even without the orbital tether at first the launch rate is going to be limited by how long it takes the upper wing-tether to get back up to "speed" between launches. I fully understand that the idea is to keep the system from being "idle" for any length of time but I haven't seen any detailed work on the modifications that would have to be made to a "standard" aircraft to be able to use the system for aviation.

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A very small scale system could be funded by aerial advertising. Companies already pay high rates for blimp advertising. If the FAA would allow tethered advertising, you could make money towing advertising banners on the tether at altitudes below 300 feet. Outdoor advertising is a $30 billion business in the USA.

Well and good but does the FAA NOT allow such a system at the present? And if they do, why? I can easily see "reasons" of public safety and "annoyence" that might crop up from such use, though how "serious" they would be remains something that needs to be looked into. (At 300ft and below what is your "horizon" visual distance? How large does the banner have to be? How much "market" is going to be within easy "visual" distance of the banner? etc)

Quote
Quote
As I recall Goodyear even had proposals for "inflatable" space craft including a "Shuttle" type vehicle it would be interesting to see what research as done on heating and reentry stress' for such vehicles.
Inflatable re-entry shields have been demonstrated by ESA and NASA.  For example, see the links below:
http://www.spaceflight.esa.int/irdt/factsheet.pdf
http://www.nasa.gov/home/hqnews/2012/jul/HQ_12-250_IRVE-3_Launch.html
But those aren't "tethers" and there are some fundemental differences in the way they are designed to work and what we're talking about :)

I'm suspecting that while the majority of the wing tether would be light-weight material its probable that the leading edge will have to be something else.

Quote
Quote
I was actually thinking an electric control-line model would be an excellent "tow-plane" substitute and testing deployment methods for the towed-tether. Of course I'm also "thinking" that finding a place to do the testing might prove a bit of an issue even given a seriously scaled down version of the system :)
Agree that control-line models would be a small-scale method to demonstrate the system. However, you are limited by the strength of the human operator at the center of the control line. I don't like standing in the middle of my experiments as it makes me nervous! My prototype has an anchor winch mounted on a wooden turntable. It's very crude, but allows some basic testing and I can operate via remote control from a safe distance.
Actually I wasn't meaning a human-hub control line model but more of a general version thereof :)

Replace the "human" with a hub and remote, (which could be wired or wireless in this case) controls and power the model through the tether. I would probably avoid using a "manned" vehicle as long as possible for various safety and practical reasons. (Having someone "drive" in a circle is harder than it sounds, and the only "practical" way it could be done for testing is on something like a "banked" track :))

I think the Black Rock idea is a good one to consider, then again I'm "kicking" myself because there is another place this could be tried about an hour from me: The Bonnivile Salt Flats...

Again though I'd be "warry" of trying to get this done "manually" due to the difficulties involved. Actually an "idea" for a ground based deployment test is a banked "track" of some type and a "slot-car" type flat-topped deployment platform...

Hmmm, ok that gives me some ideas to think on :)
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I am going to give a ten minute talk on the Space Show this Tuesday (Oct 16th) at 1930 PST. Call-in if you'd like to join the discussion.
Cool! I will try and be home to listen and/or call in if I can.

Randy

Offline johncarpinelli

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Re: Two Stage Tether to Orbit Launch System
« Reply #14 on: 10/25/2012 06:51 AM »
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/

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).

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.


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.

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.

Space launch is a more speculative proposition. We have to prove the concept at lower speeds before trying to build a hypersonic tether.

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.

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

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