Quote from: RanulfC on 12/07/2011 02:12 pmBut to your "basic" question of the concepts technical feasiblity; of course it's "feasible" and could "technically" be done. I've actually seen this same idea several times before though your suggestion of counter-weights and launching from the mid-point of the teather is an interesting variant that mitagates some of the difficulties with earlier suggestions, so further work is certainly useful.First, let me apologize for my Randy rant. That is not the way I would like this topic to go.
But to your "basic" question of the concepts technical feasiblity; of course it's "feasible" and could "technically" be done. I've actually seen this same idea several times before though your suggestion of counter-weights and launching from the mid-point of the teather is an interesting variant that mitagates some of the difficulties with earlier suggestions, so further work is certainly useful.
However, to so cavalierly dismiss my concept as an interesting variant on an earlier idea is condescending. The fact that the second stage launch vehicle is launched from the middle of the ribbon, the fact that the overcarriage remains on the ribbon providing a retarding force, and the fact that the counterweights absorb the shock and dampen the oscillations make this concept possible.
In my concept, launch is possible again after eight hours. But is it technically feasible? That is what I hope to answer with intense technical debates on this forum and through my web site at www.fisherspacesystems.com.
I am an engineer working on the electric takeoff project. The payload is an aircraft with wings. The payload should generate lift as it releases from the harness and transitions to the climb on the ribbon. At the transition point, it will be travelling as fast as the tow aircraft (e.g. Mach 0.4). Our initial goal is point-to-point transport so the glide ratio for the payload should be high.It's not an easy system to model. Let's continue the discussion and hopefully collaborate on some of the technical work.
Coincidentally, I published a short piece on inflatable space towers a few days ago on our site (http://electrictakeoff.com/blog). Would it be possible to build a space tower using a pyramid of inflatable spheres strapped together? Would that reduce the strength requirements for the construction material?
Quote from: Jerry Fisher on 12/13/2011 08:11 pm I could go on about space colonization but I'm getting writers cramp. Google it yourself and you will find that you are in the minority concerning your comment on technical and commercial viability. There is a great many opportunities in space. Getting there is the problem and that is why I'm working on the Space Track Launch System.No, not true. A. You can always get more hits on pros for subject vs consb. Science fantasy even gets more hits that all of yours combined.1. Terrestrial solar power will always be cheaper and more viable than SBSP. There will never be an economic justification for SBSP. There is enough barren land on the earth.This is the majority opinion.2. helium-3 is still useless on earth. They are no closer to fusion with it now as they were 30 years ago3. mining asteroids for terrestrial use is not viable either. Getting the material to the surface is where is fails. Mining asteroids is for ISRU and building hardware not intended to go back to the earth's surface.
I could go on about space colonization but I'm getting writers cramp. Google it yourself and you will find that you are in the minority concerning your comment on technical and commercial viability. There is a great many opportunities in space. Getting there is the problem and that is why I'm working on the Space Track Launch System.
No, not true. A. You can always get more hits on pros for subject vs consb. Science fantasy even gets more hits that all of yours combined.1. Terrestrial solar power will always be cheaper and more viable than SBSP. There will never be an economic justification for SBSP. There is enough barren land on the earth.This is the majority opinion.2. helium-3 is still useless on earth. They are no closer to fusion with it now as they were 30 years ago3. mining asteroids for terrestrial use is not viable either. Getting the material to the surface is where is fails. Mining asteroids is for ISRU and building hardware not intended to go back to the earth's surface.
Finally, "my" particular and often semi-obsesive (being nice about it )"peeve" as an ex-Air Force maintainer is operations and maintenance of the concept. Now I'm NOT going to ask for an in-depth study and planning of how someone would change a light-bulb on the tip of the teather while it's rotating or anything like that. At this stage overall functionality and technical feasability are of course more important. However consider this your "warning" of sorts that "I might actually come back at some later point and actually ask for some more details
So if you are a skeptical space enthusiast then think realistically about your future options for visiting space. If you want to see the curvature of the Earth first hand and experience a weightless re-entry back to Earth, your best hope is a space tower.
I think of myself as an optimistic space enthusiast. I prefer to think of the glass as 1% full as opposed to 99% empty. There are over 300 million people in the US today. Lets say 1% are wealthy Americans. That is 3 million people. Lets say that 1% of those are extreme adventurers and would pay for a trip into space. That is 30,000 people.
Quote from: Jim on 12/19/2011 02:32 amBoth assumptions are too high. People who want to and can afford are less than 5000. Maybe. Maybe not. I haven't done a detailed cost analysis. If I don't achieve at least an order of magnitude reduction in launch cost at the start, then I can't justify even building the Space Track Launch System. If I do achieve an order of magnitude or better, than I would expect the 5000 number to go up. By the way, I showed you my assumptions. I'd like to see yours. Where did you get that number and what is it based on? Surely, it is not a WAG.Jerry
Both assumptions are too high. People who want to and can afford are less than 5000.
The system consist of counterweights attached to ribbons which are attached to a rotating truss mounted on a tall tower...
The "when it is 2 magnitudes taller than anything ever built?" isn't relevant, like all the creative alternative ideas it comes down to: Is it possible, what's the cost, and who's going to foot the bill?
What aerospace company wants to operate out of the north pole?
The material of choice is a carbon nanotube material with a working tensile strength of 25 GPa....
A detailed cost analysis has not been done. The first task is to determine if the STLS is technically feasible.
I have looked into ... transferring momentum to the launch vehicle. Launching from the tower and attaching to a tether in LEO will greatly reduce the deltaV required from the launch vehicle. It turns out that the payload capability is about doubled.
The point ... would probably be better stated as asking: Given the mega-structure of the tower and tethers, the infrastructure, and all the associated overall costs involved how does your concept help get from where we are not to where your concept becomes "cost-effective" in terms of launch capacity and price per-pound-to-orbit?
I've seen the government uhhhh.... taxpayer get screwed so many times on cost plus fixed fee contracts it ain't funny...
However, I don't have $25 million for a few days on the ISS.
Otherwise, I don't have the time or the patience to listen to age old arguments about cost. We will get to that point if the concept is feasible and we have a better handle on the technology.
The fact tentative suggestion that the second stage launch vehicle is launched from the middle of the ribbon, the fact tentative suggestion that the overcarriage remains on the ribbon providing a retarding force, and the fact tentative suggestion that the counterweights absorb the shock and dampen the oscillations make this concept theoretically possible.
Webster's dictionary defines paradigm as a philosophical or theoretical framework of any kind. Your comment is definitely not theoretical so it must be philosophical in nature. So let's talk philosophically.
Lets take space based solar power satellites for example. Goggle space based solar power. You will get approximately 217 thousand hits.
Further, compressive and torsional loads at the foundation are equally as important, tho not nearly as glamorous, and have not been considered sufficiently.
You have not demonstrated anything on your website about feasibility, although you have demonstrated some 3D CAD skills which are greater than mine.
Regarding the chicken and egg aspects of the problem you have set for yourself, when you suggest six tons a day each day of the year, it is evidence that you have not considered DDT&E, of which time is of crucial importance.
In addition, this thread is an informal peer review, FWIW.
Quote from: johncarpinelli on 12/19/2011 10:34 pmWe taxpayers have spent sixty years and hundreds of billions trying to "finesse chemical rocketry". As a result, we can now purchase $35m tickets to orbit on a foreign rocket. It is not an ideal situation. Which is true about the poor, ever suffering taxpayer, but false about the conclusion you draw. True, in general, that the current status of our HSF program is the result of chemistry, but it is the result caused by political chemistry, not the chemistry of the rocket equation.
We taxpayers have spent sixty years and hundreds of billions trying to "finesse chemical rocketry". As a result, we can now purchase $35m tickets to orbit on a foreign rocket. It is not an ideal situation.
To lower launch costs, we need a system that amortizes its cost over many journeys and can generate revenue from both aviation and space transport. Suitable technologies include laser launch, tether launch and space towers
Quote from: Jim on 12/21/2011 09:35 pmIf launch costs are to be lowered, it is not going to be with a system that requires 100's of billions of infrastructure. Electric takeoff is just another unworkable scheme promoted by the fringe.As with current launch systems like NASA and the Space Shuttle infrastructure.I'm on the fringe and proud of it. At least I'm trying to do something about the high cost of spaceflight.Jerry
If launch costs are to be lowered, it is not going to be with a system that requires 100's of billions of infrastructure. Electric takeoff is just another unworkable scheme promoted by the fringe.
Sorry folks. It seems I've let a few chemical propellant advocates (I'll call them CPAs from now on) hijack my topic. Correct me if I'm wrong but, I believe this is NASA's forum on advance concepts. It appears the CPA's idea of advances in propulsion is a .01% increase in chemical propellant efficiency (I believe someone used the term finesse). So, lets get back on topic.
The Space Track Launch System (STLS) is a two stage system. The first stage is a tall tower 100-150 km high.
The second stage is a liquid fueled launch vehicle (LV) designed to launch form the STLS. The launch vehicle attaches to a generic overcarriage.
The overcarriage is itself a reentry vehicle.
The counterweight is designed to deploy a thin layer of ribbon approximately 400 km long. During deployment, the motor produces approximately 60 kW of power which is dissipated through nichrome wires at the base of the counterweight.
Power is delivered to the counterweights by ground based high powered solid state lasers. Solar panels made of Aluminum Gallium Arsenide photovoltaic cells receive the energy from the lasers.
The tower is from 100-150 km high and supports an estimated 3,100 tons of passenger elevators, cargo elevators, research station, rotating truss and ribbons.
Joseph A. Carroll (Carroll, J.A.,1986). Carroll suggested that a rotating sling on the surface of an airless body such as the moon might accelerate 10-20 kg payloads to orbital velocity.
Finally, the overcarriage returns to the launch site, making the STLS a completely reusable launch system.
For an 80 ton launch vehicle under a 6g load, each ejector segment supports a load of 2.4 x 106 N. The ejector segment is made of 60% Carbon Fiber and 40% Epoxy. This gives an ultimate strength, σu, equal to 1.47 x 109 N/m2 and the modulus of elasticity, E, equal to 1.38 x 1011 N/m2.
The air bearing must produce a total lifting force of 1.5 x 106 N.
The fuselage for the overcarriage is of a conventional aircraft design.
It is assumed that the hydraulic system can use the same nitrogen gas that is used for the air bearings.
A base load of 8.0 x 107 N over an area of 12.6 m2 results in a load per unit area of 6.4 x 106 N/m2 or about 921 psi.