Fast sketch of a two stage orbiter

[mlorrey]

no, not really. LEO is halfway to anywhere, but GEO is 3/4. A straight up and down pop-up is a far cry from LEO. Mach 6 straight up should get you to 300 mi altitude with a stationary apogee, and should be easily possible with todays supersonic aircraft technology. This makes LEO the hard way into space.<br /><br />Sure it would be nice to have the tether go to ground, but you have all that space junk in LEO, plus atmospheric issues, and actually, stopping 300 mi short does save about 20% on the mass of your tether, because the last 300 mi is the steepest part of the gravity well. <br /><br />This means that with a tether, a suborbital pop-up gets you to GEO, and you get a free ride from there to the Lunar L1 point, at which point you could ride a shorter tether from L1 to the lunar surface.

 

[larrison]

So at 300 miles you still need almost 22,000 miles of tether. If the tether anchor is lower it's going to be moving in relationship with the launched vehicle and it will have to dock with a moving object ( upwards to 17,500 mph)<br />Dont forget you also need a counter weight or docking will pull the whole system down.

 

[mlorrey]

Uh, no, no, and, uh, no.<br /><br />The launched vehicle will be launched straight UP, as in vertical, as in NOT horizontal, no lateral motion, a lack of downrange trajectory, i.e. it will dock by landing on a deck like that of a small aircraft carrier, or even a helideck, at zero velocity. The deck will be at the vehicles apogee, i.e. the peak, the ultimate altitude of its completely vertical trajectory. Now, is there any way you still believe that this completely suborbital vehicle will have ANY downrange velocity at all????<br /><br />Of course, a GEO tether will have a counterweight a few thousand miles out from 22300, from which it will launch payloads to a tether at EML-1....

 

[larrison]

Uh, no, no, and, un, no.<br /><br />I understood your concept of geosynchronous. I was trying to point out that IF (and I stress IF as in maybe as in an alternative) the length of the tether were shortened by lowering the anchor point the station would no longer be geosynchronous.<br />I also restate that this technology is in the science fiction stages at best. The longest carbon nanotube I've heard of has only been a centimeter long. Don't forget the logistics of getting something like that in orbit to begin with. I really believe that by the time it is possible to build such a machine other ways into space will have been developed.

 

[mlorrey]

Well, that is the point of balancing the system. It may move, but hardly by any significant amount, and so long as the system is sufficiently counterbalanced, it won't be an issue.<br /><br />As for "science fiction", I'd say its a science future: not fiction, but not yet established fact. One would not need carbon nanotubes to build tethers on the moon or on Mars.<br /><br />And, no, short of Star Trek teleportation, there is no form of surface to orbit travel which will be superior to tether transportation.

 

[larrison]

I think the opening of space travel due to a tether or space elevator would be enormous but I really don't feel it will be an actuality in the next few decades.

 

[mlorrey]

I believe we'll start seeing relatively small tethers being launched before 2020, with a lunar tether by 2030, and a geosynch tether by 2040.<br /><br />By that time, we'll likely have 3rd gen launchers that are fully RBCC SSTOs, but they will still be relatively expensive to ride and limited in payload capacity.<br /><br />The airline industry would not have reached its current state at Concorde prices and the degree of regulation that supersonic flight has. All rocket launcher passenger prices will always be relegated to prices in excess of 10xConcorde at a bare minimum. It will take tethers to truly open up space travel to the masses.

 

[scottb50]

I hate to break the group hug but tethers are way down the road, if at all, and will take rockets to put into place to begin with. <div class="Discussion_UserSignature"> </div>

 

[mlorrey]

Yes, they will, however, the scope of the project has been figured out: about $10-14 billion in launch costs, fiber, and constructing the geosynch assembler. Figure ten times as much if under government contract. <br /><br />The real kicker is once you have one put up, the second one is ten times cheaper.

 

[scottb50]

Sort of like a bean stalk. Plant the magic bean..<br /><br />In theory, with the right materials, an elevator could be ideal, but there is no way it can be built without heavy lift capability. Lets sit around another ten or fifteen years to perfect the technology of elevators then frantically figure out how to put the into Space to begin with. <div class="Discussion_UserSignature"> </div>

 

[mlorrey]

Actually, not true. You don't need heavy lift capability, you do need the ability to launch a steady supply of buckythread spools to an orbiting loom, which can be launched either in one piece or in pieces and assembled in LEO, then moved to GEO by ion drive. A loom-in-space would be of immense value, capable of building not only multiple geosynch tethers, but a lunar tether, a martian tether, and a venusian tether. It is the one key piece of industrial equipment that must be built in orbit.

 

[nacnud]

A Luna or Venusian elevator would be interesting seening as the rotaion of those bodies takes a month and a year respectively.

 

[mlorrey]

Actual, nacnud, a lunar tether is pretty easy, you can build as many as you want, to four possible distinations, to each lagrange point. The easiest is EML-1, of course. Run a counterweight several thousand miles toward earth, to catch vessels outbound from GEO tether counterweights, and run it through the lagrange point and down to the lunar surface. Tide keeps it in place, and the 1/6th gravity of the moon means you could build the lunar tether out of kevlar, no need for exotic buckytubes.<br /><br />A venusian tether would end just above the atmosphere, moving along at a stately 900-950 mph or so, unless you wanted to give it orbital inclination to cover more of the planet, reach the northern continent.<br /><br />The low end station would be a large platform for suborbital rocketplanes to land on like an aircraft carrier. With less than 1000 mph of downrange delta-v necessary, and an altitude just above the atmospheric boundary, any vehicles visiting the surface would need minimal delta-v to return to the down-side station, thus they could land and take-off on their own fuel reserves without needing a fuel source on planet... Given the massive atmospherice pressures, though, it will be interesting developing rocket engines for that application...<br /><br />The tether would extend outward to what would be an Earth-normal 24 orbital period, where an space station would be located, then another length outward to a counterweight to catch interplanetary missions.<br />

 

[josh_simonson]

A vertical orbiting tether, centered at 5000km altitude, would have a lower end velocity of less than mach 10. This would require a hypersonic interceptor, as well as a climber, but the cable is only 1/7 as long and under less strain than a full elevator since the bottom only experiences 0.81G. You also only need to climb 1/7 as high, in lower gravity, to get to full orbit, easing requirements for power beaming. It still crosses the van allen belts, as a full elevator would, but only the first half, at which point you detatch, coast out and circularize your orbit above the radiation belts.<br /><br />A shorter elevator like this may also allow a climber to be replaced with a counterweight that reels in the tether after capture, allowing one to build a big honking thing with onboard nuclear power. The tether would also be safely rolled up when not in use.<br /><br />Such a semi-elevator eliminates the hardest part of the launch vehicle (mach 10-25) and also eases the most difficult aspects of the elevator by an order of magnitude. Depending on the relative cost of each component, tether length can be traded off for interceptor speed until a balance is reached.

 

[gunsandrockets]

"The original F-106 drop tanks were hypersonic rated, and were planned to be kept for the F-106X mach 5 interceptor that competed against the YF-12 in the early 60's ADC competition."<br /><br />Mach 5? The F-106X?<br /><br />http://www.globalsecurity.org/military/systems/aircraft/f-106a.htm<br /><br />"Some ten years later a third configuration, the so called F-106X, recieved considerable attention. The F-106X was a basic F-106 that would feature a new radome and a larger radar antenna. It would also recieve, among other things, a modified fire control system (providing "look down" capability) and a new air to air missile providing "shoot down" capability."<br /><br />The YF-12 competitor? The F-111!<br /><br />http://www.globalsecurity.org/military/systems/aircraft/f-12.htm<br /><br />

 

[mlorrey]

"The Secretary of Defense's decision on 23 November 1967 to discontinue F-12 development and to select the F-106 as the future interceptor to complement a new airborne warning and control system (AWACS) altered ADC planning. The SLIM program was put aside in favor of a more costly one-nearly $1 billion-for the so called (but as it turned out, never to be) F 106X. <br /><br />As part of the Korean buildup stemming from the Pueblo crisis, a series of F-106 deployments to Korea began. The first F-106s deployed from McChord AFB and conducted in flight refueling en route the first such refueling of F-106s. <br /><br />When it appeared in late 1968 that the F-106X would not materialize, ADC renewed its efforts to modernize the entire F-106 weapon system which, it believed, had become one of the Air Force's most competent fighters. "<br /><br />The F-111 was an absolute POS that McNamara tried to ram down the throat of the USAF. It never became an ADC aircraft, it was only used by TAC. Before the F-111, the F-106X was proposed, and beat the F-12 in a paper competition:<br /><br />http://www.f-106deltadart.com/history.htm<br />"The F-106X (Model 8-28/8-29) was a 1956 design study for a Delta Dart follow-on. This study envisaged an interceptor with a canard layout that was powered by a JT4B-22 turbojet fed by rectangular air intakes. It was envisaged as an alternative to the Lockheed YF-12 (later SR-71), and was to have had a fire control system with "look-down, shoot-down" capability fed by a 40-inch radar dish. The F-106X was extremely advanced for its time with Mach 5 performance envisaged.<br /><br />The project was later re-designated F-106C/D, with "C" being the single-seat version, the "D" being the two-seat version. At one time the Air Force had considered acquiring 350 of these advanced interceptors, but the F-106C/D project was cancelled on 23 September 1958.<br /><br />Following the cancellation of the Mod

 

[larrison]

Excitment is what it's all about. Yes I know its a radical design. I'm trying to build a 1/12 scale model to test. I know It won't be the same as a half or even 1/3 scale but it will let me prove the concept works.<br /><br /><br />Oh, and if anyone knows where I can get eight jet engines with a four inch fan please let me know.

 

[grooble]

http://www.swbturbines.com/ They might have what you need.

 

[vt_hokie]

<i>The original F-106 drop tanks were hypersonic rated, and were planned to be kept for the F-106X mach 5 interceptor that competed against the YF-12 in the early 60's ADC competition.</i><br /><br />Interesting! I'd never heard of that before.

 

[mlorrey]

Yes, what is truly interesting is that the "Six X" beat the YF-12, yet you hear way more about the 12 than the Six X. A little googling about the other century series aircraft is eye opening, you get the idea that, other than the 106, and maybe the 104, the other century planes that actually went into production were substandard compared to the models that didn't, from the Mach3 XF-103 Thunderwarrior to the Mach 4 XF-108 Rapier, these were great aircraft that never flew, while the F-102, F-105, F-111, and F-110 (F-4 Phantom) were substandard planes that only went into production because they had the right contractors and political connections at the time of their development.

 

[vt_hokie]

<i>...and F-110 (F-4 Phantom) </i><br /><br />The F-4 was originally known as the F-110? <br /><br />I recently came across a drawing of a proposed variable geometry wing version of the Phantom!

 

[mlorrey]

Yes, it was the F-110 Specter. It is interesting how older planes are often proposed in upgraded forms to fly instead of newer designs. For instance, the F-4 was proposed with bigger wings and new engines as an alternative to the F-15, while the 105 was replaced by the F-4, though an improved Thud was proposed instead. In the case of the 106, it was an improvement on the 102 that was selected rather than the 103 and the 107 was abandoned in favor of upgrading the 106. <br /><br />The 109 would have been a bomber interceptor and escort for the B-70, replacing the 106. It looked like a cross between the 70 and a Mig-25, and was likely the true competition against the Six X, albeit the 109 would have had greater range to operate as a bomber escort while the Six X would have remained a shorter range defense interceptor of similar performance.