I have a friend with a PhD in electrical engineering who tried to use a femptocell provided by his cellular carrier on his home network. He was only able to get it to work erratically, in spite of a long time on the phone with the carrier's tech support and a lot of knowledge of networking.
Quote from: a_langwich on 11/21/2013 06:25 amMaybe they exhausted all the possibilities within reach? Or maybe they realized they weren't going to get anywhere near their cost target for the vehicle? Or, maybe they realized the market demand was not enough to support not just their pricing but any reasonable price, at the present. Bottom line, you can't say it works at this price, when something clearly did NOT work.And you can't sit back and speculate about the viability of someone else's business case without having taken the time to actually run one to ground. That is my issue with Jim's off the cuff and frankly ill-informed comment. I performed due diligence for my client for two years, building the business case, surveying the market to understand size, value, timing, risks, legal and policy requirements and hurdles, etc. All these factors go into the business case assessment. That is weighed against the financial goals of the client, their risk posture, their business climate, their shareholder's expectations, etc. For my client, the business case was attractive.
Maybe they exhausted all the possibilities within reach? Or maybe they realized they weren't going to get anywhere near their cost target for the vehicle? Or, maybe they realized the market demand was not enough to support not just their pricing but any reasonable price, at the present. Bottom line, you can't say it works at this price, when something clearly did NOT work.
It was not the financial side of the equation, but the complete lack of coherent US policy regarding operations within space and the regulatory risks that would flow from that led to the decision not to execute the business plan.
What regulatory risks were you/client worried about? For MDA, they are servicing satellites which their customer owns, so no questions about ownership there. Debris liberated during servicing causing a problem? This shouldn't be a large factor for GEO, right? Explosions or some other accident causing some risk to other satellites? All of the risks to MDA with respect to the Intelsat satellites could be handled inside the terms of the contract, right? Or did the business case require Russian or Chinese launches, or offshore tax havens, which might fall afoul of ITAR?
Quote from: robertross on 10/19/2013 11:30 pmThat would be cool to see.Here are a few resources that have been approved for public release:http://ssco.gsfc.nasa.gov/workshop_2012/Barnhart_final_presentation_2012_workshop.pdf...~Jon
That would be cool to see.
Quote from: Solman on 10/22/2013 12:40 am At the bottom of page 2 of the "Economics of Repurposing in situ retired spacecraft components" paper assembly in space to build very large apertures for RF and optical systems is mentioned. This relates to something I had been wondering about lately. Taken to the extreme, might three huge antennas with appropriate electronics, built in GEO, be able to replace cell phone towers by allowing 2 way comm with existing cellphones directly? That would be what - a trillion dollar business? CELLULAR: Xerox Parc put it best in the late 80s and early 90s bandwidth / the population of earth = bits/sec per personThere are some 7 billion people on this world so that Tesla style solution doesn't work. with your 3 antennas canted to service 3 spherical triangles from on high and maybe covering 1/3 of the earth the best you get is: 1 cell size of 3 (antennas or sectors) * 3 sats to cover the earth *bandwidth/7 billion peopleYou want lots of cells...
At the bottom of page 2 of the "Economics of Repurposing in situ retired spacecraft components" paper assembly in space to build very large apertures for RF and optical systems is mentioned. This relates to something I had been wondering about lately. Taken to the extreme, might three huge antennas with appropriate electronics, built in GEO, be able to replace cell phone towers by allowing 2 way comm with existing cellphones directly? That would be what - a trillion dollar business?
Thanks for that response and sorry I didn't see it sooner. My understanding of this subject is quite limited so I hope you'll indulge me but I had in mind many cells, not just three. A huge antenna would be able to transmit and receive using spot beams that cover an area little bigger than the area a cell tower covers might it? If so, wouldn't the bandwidth issue be no different from what current cell phones have?
Quote from: Solman on 12/11/2013 08:23 pmThanks for that response and sorry I didn't see it sooner. My understanding of this subject is quite limited so I hope you'll indulge me but I had in mind many cells, not just three. A huge antenna would be able to transmit and receive using spot beams that cover an area little bigger than the area a cell tower covers might it? If so, wouldn't the bandwidth issue be no different from what current cell phones have? So you are going to put almost over 2 million transmitters and receivers on the antenna to create all the necessary spot beams?
As I understand it the signal latency means about 500 milliseconds for interactive communication so the idea is probably not viable for that, but it does have the advantage of complete coverage including for ships and planes.While bad for gaming, text, voice and web surfing might be enough to make it worthwhile.
Quote from: Solman on 12/14/2013 12:14 amAs I understand it the signal latency means about 500 milliseconds for interactive communication so the idea is probably not viable for that, but it does have the advantage of complete coverage including for ships and planes.While bad for gaming, text, voice and web surfing might be enough to make it worthwhile.The wording of your last sentence makes it unclear which of gaming, text, voice, and web surfing you think it would be bad for and which you think it might work for.It's definitely too much latency to replace local cells for voice calls. That much latency is very noticeable. That's one of the reasons Iridium and its competitors use LEO satellites.
Well actually yes. The idea already requires a two mile diameter antenna after all. Given its scale it would seem that there would be room for millions of transceivers at the focal area particularly if the order for them lead to development of an a system optimized for the purpose. The payoff is potentially vast and it sure could lead to an increase in the number of launches. As I understand it the signal latency means about 500 milliseconds for interactive communication so the idea is probably not viable for that, but it does have the advantage of complete coverage including for ships and planes.While bad for gaming, text, voice and web surfing might be enough to make it worthwhile.
Quote from: Solman on 12/14/2013 12:14 amWell actually yes. The idea already requires a two mile diameter antenna after all. Given its scale it would seem that there would be room for millions of transceivers at the focal area particularly if the order for them lead to development of an a system optimized for the purpose. The payoff is potentially vast and it sure could lead to an increase in the number of launches. As I understand it the signal latency means about 500 milliseconds for interactive communication so the idea is probably not viable for that, but it does have the advantage of complete coverage including for ships and planes.While bad for gaming, text, voice and web surfing might be enough to make it worthwhile. Think about it, hard for once.there is no payoff, it is nonviable
Obviously the 2 million transmitters and receivers are going to have considerable mass and for the idea to be viable, serious effort would have to be made to reduce that, if indeed physics allows improvement to the needed extent.
Hey guys, could we take hypothetical discussions of some 2million transmitter GEO satellites somewhere else? There has been almost nothing on this thread about the actual DARPA Phoenix program for some time now.~Jon
Even as DARPA and U.S. military officials contemplate the future direction of the Phoenix program, DARPA officials see a role for satlets.“As part of the risk reduction activities going forward for the Phoenix project through 2015, DARPA is planning on a flight experiment to validate the satlet concept in low Earth orbit,” said David Barnhart, DARPA’s Phoenix program manager. “This experiment would allow the concept of cellularized, pre-aggregated satlets to go through a series of tests to validate attitude control, power control, processing system and telemetry system handoff and thermal management on orbit.”
Description: To date, servicing operations have never been conducted on spacecraft beyond low earth orbit (LEO). A large number of national security and commercial space systems operate at geosynchronous earth orbit (GEO) altitudes, furthermore, many end-of-life or failed spacecraft drift without control through portions of the GEO belt, creating a growing hazard to operational spacecraft. Technologies for servicing of spacecraft with the expectation that such servicing would involve a mix of highly autonomous and remotely (i.e., ground-based) teleoperated robotic systems have been previously pursued. The Phoenix servicing program will build upon these legacy technologies, tackling the more complex GEO environment and expanding beyond pure traditional servicing functions. The program seeks to validate robotics operations in GEO suitable for a variety of potential servicing tasks with a Servicer/Tender, in full collaboration and cooperation with existing satellite owners. The program will examine utilization of ride-along capability to GEO supporting upgrading, repairing, assembling, and reconfiguring satellites. The program will include an early LEO flight experiment focused on satlets, as a path of risk reduction for modular assembly on orbit. Key challenges include robotic tool/end effector requirements, efficient orbital maneuvering of a servicing vehicle, robotic arm systems, and integration and efficient and low cost transportation of robotic tools. The anticipated transition partners are the Air Force and commercial spacecraft servicing providers
FY 2013 Accomplishments: - Completed preliminary design of robotic servicing payload architecture and systems for Phoenix vehicle. - Developed payload orbital delivery systems (PODS) designs for commercial satellite ride-along as well as first working prototype for dispensement. - Initiated flight scale build of first satlets and demonstrated aggregation of performance functions in a ground testbed. - Initiated development and build of robotic servicing components including tools and toolbelt systems and selected a complete complement of tools for Phoenix. - Initiated six degree of freedom testbed on ground; began virtual system testing with the primary and secondary robotic arms. - Initiated telepresence simulation and began test qualification and training standards for Phoenix robotic operations. - Built first prototype of sensor suite for guidance and control on servicer and evaluated it with actual flight software algorithms.FY 2014 Plans: - Complete critical design of robotic servicing system including primary and secondary robotic arms and toolbelt. - Deliver prototypes of various servicing tasks to robotic testbed for validation and integration with tools. - Complete mission validation testing inside a six degree of freedom testbed. - Complete critical design of tele-operations system. - Conduct pre-ship review for early LEO satlet experiment equipment and deliver to launch integrator.FY 2015 Plans: - Launch early LEO satlet experiment and conduct experiment operations. - Complete delta critical design of satlets per lessons learned from LEO experiment. - Complete delta critical design of PODs. - Validate specific servicing mission types that maximize commercial and DoD operations. - Validate primary and secondary robotic hardware and software.