SPACE

[Darkflame]

It saves you money because you dont have to carry the fuel to get to space. Same as a space elevator, solar-sails and most other "future space designs".
The goal is to separate the power from what your accelerating.

And yes, its big - but still absolutely tiny compared to a space elevator. Its comparatively easy. A space elevator demands not just a insanely long cable, but a insanely wide one as well to support its own weight. Your not just talking about developing a (theoretical material) nano-tube based rope, your talking about manufacturing, and putting into orbit a huge nano-tube ribbon. I believe I read the width has to be 100 of meters wide at least for that to work.

By comparison launch loops, problems are not "this material hasn't been invented yet" and more instead questions of precision (ie, hocking up aircraft already going at supersonic speeds). Imho, thats seems a lot less of a challenge


As for moving the 'counter balance' in and out - that can be done with solar power over a arbitrarily big timescale. Sure, you want the thing re-usable in a decent period, but your not racing physics at that point. The "reset" can be comparatively slow compared to the "launch". The important bit is to avoid the need to launch propellant all the time. Yes, you'd still need to get the counterweight up there (and moving a existing asteroid might be the way to do it), but its a once-only deal that.


Again, not easy by any stretch of the imagination, but I do think its within the range of human achievement with more or less today's tech.

[pogo]

But you need to expend fuel getting the tether into space initially. Lots and lots of fuel. Then every time you use it you need to boost it yet again to restore energy lost/given up when it helps something else get into orbit. There really is no free energy here. The only way to save rocket fuel is if you can somehow fuel it in space from space, but that is a long long way off.

Also, SpaceX landed at sea at last:

[RedOktober]

Why do they need spacex to land on a barge anyway?

Let's assume I haven't been paying attention.

[gumboot]

Because NIMBY?

[edit]
Actually, if you watch the video they explain that it's because it's cheaper to not come back to where you launched from. Obviously landing in the ocean gives you a lot more freedom in picking a landing site.

[Dio]

In addition, people feel a lot happier about rockets that fly over the sea, because they can't hit anyone.

[Darkflame]

Musk must be very happy right now with this ontop of the insane pre-orders levels for the new Telsa.

But you need to expend fuel getting the tether into space initially. Lots and lots of fuel. Then every time you use it you need to boost it yet again to restore energy lost/given up when it helps something else get into orbit. There really is no free energy here. The only way to save rocket fuel is if you can somehow fuel it in space from space, but that is a long long way off.

The energy can come from solar panels. Unlike with getting a craft into space itself, there are methods of adjusting orbits without needing propellant. Not without energy, but without 'fuel' as such. There are many variations on the skyhook idea, but they typically use a winch, counterbalance, and/or a electromagnetic tethers (https://en.wikipedia.org/wiki/Electrodynamic_tether) to regain lost momentum.

The "free" energy in all this is merely energy not used to lift propellant you'd require with other methods. Its free in the same way that 'buy one get one free' offers are free.

In many ways its a bit like a gravitational slingshot in that your stealing momentum. Admitably its not as convenient as planets (where we can take what we like and dont need to put that momentum back - which sort of is free energy...).

[pogo]

The energy can come from solar panels. Unlike with getting a craft into space itself, there are methods of adjusting orbits without needing propellant. Not without energy, but without 'fuel' as such. There are many variations on the skyhook idea, but they typically use a winch, counterbalance, and/or a electromagnetic tethers (https://en.wikipedia.org/wiki/Electrodynamic_tether) to regain lost momentum.

The "free" energy in all this is merely energy not used to lift propellant you'd require with other methods. Its free in the same way that 'buy one get one free' offers are free.

No, nonsense. There are two problems with trying to lift things into space with solar panels. One the energy is so piddlingly small it won’t work. Two you really do need propellant, because of conservation of momentum. You need to push something in the opposite direction to which you want to go, to move something or keep it in place. You need fuel.

And again, the propellant you don’t need because your tether lifts stuff part of the way, you need to get the tether up in the first place. Much more of it because the tether is big. The only way you “save” energy is if you can find it in space. Solar panels won’t work, but maybe a small asteroid could be guided into position, to act as both the tether and a supply of fuel. I imagine there will be other benefits, of having such a permanent platform in low earth orbit. But that is something for the far distant future.

[pogo]

A Space X launch aced the landing again. Here’s a rocket eye view of the landing.

[pogo]

China is launching their Tiangong-2 space lab, their own answer to ISS, and there’s a live stream. Lift off at about three o’clock

[Istar]

Well they made that look easy!

Anyone else notice how 'clean' and uncluttered the pad area was? And no outgassing of any sort from the vehicle or gantry during that last pre-launch couple of minutes...

Also, those engines just fire-up and fuck-off, don't they - none of this "ignition, engines on, throttle up, lift-off". That was "ignitio - oh off you go then".

[Darkflame]

The energy can come from solar panels. Unlike with getting a craft into space itself, there are methods of adjusting orbits without needing propellant. Not without energy, but without 'fuel' as such. There are many variations on the skyhook idea, but they typically use a winch, counterbalance, and/or a electromagnetic tethers (https://en.wikipedia.org/wiki/Electrodynamic_tether) to regain lost momentum.

The "free" energy in all this is merely energy not used to lift propellant you'd require with other methods. Its free in the same way that 'buy one get one free' offers are free.

No, nonsense. There are two problems with trying to lift things into space with solar panels. One the energy is so piddlingly small it won’t work. Two you really do need propellant, because of conservation of momentum. You need to push something in the opposite direction to which you want to go, to move something or keep it in place. You need fuel.

And again, the propellant you don’t need because your tether lifts stuff part of the way, you need to get the tether up in the first place. Much more of it because the tether is big. The only way you “save” energy is if you can find it in space. Solar panels won’t work, but maybe a small asteroid could be guided into position, to act as both the tether and a supply of fuel. I imagine there will be other benefits, of having such a permanent platform in low earth orbit. But that is something for the far distant future.

Theres many factors here other then "conservation of moment!" "you dont get anything for free" which while true does not mean methods other then chucking fuel behind you cant possible be more efficient.
The benefits of not lifting your fuel is not the same as "take the fuel from space".

One pertinent point is the more energy you have the less propellant you need. That's the idea of ion drives. low thrust but super efficient because of the speed of the propellant. I Likewise (within reason) time is a factor, if you don't need to change momentum quickly you can get away with a dribble - which means the re-balancing process does not need to take the same time as the momentum exchange to lift assist. The speed of compensation for momentum differences would thus likely come down to a proportion of the size of your solar array. (That is you move your counterbalance slowly back into place after the quicker period of momentum exchange. Depending on your solar array, you could get away with more/less time for this reset)

(also, the link, within earth orbit, there is magnetic effects that can be exploited that require no propellant at all. see; electrodynamic tethers. Nature can have some quite cool effects)

Overall;
I'm not talking magic here, and neither am I talking about things I made up. There's been plenty of engineers and physicists looking into this and not finding any of your objections. Your not arguing with me, your arguing with, for example, researchers at Boeing (http://www.niac.usra.edu/files/studies/ ... 1Grant.pdf)

The problems with this stuff is big, but its not the core physics, but rather materials,cost,precision etc.
People far smarter then me have looked into it, and not dismissed it out of hand as being in principle wrong.

because of conservation of momentum. You need to push something in the opposite direction to which you want to go,

umm...wait.....maybe this might be the critical point, there is a counterbalance. If I wasn't making that clear, maybe you should read other sources.
(I mean, how much propellant does a regular earth elevator take?)
This doesn't work without some sort of mass going the other way.
(It is not necessarily the case that the counterbalance is littoral though - Boeings suggestion is to recapture mass, for example [which could be any waste product, crew going down again etc].
The momentum/energy cost you have to pay for, according to physics, is the difference - and that difference does not need to include the weight of the ship or the additional fuel. )

[pogo]

I'm not talking magic here, and neither am I talking about things I made up. There's been plenty of engineers and physicists looking into this and not finding any of your objections. Your not arguing with me, your arguing with, for example, researchers at Boeing (http://www.niac.usra.edu/files/studies/ ... 1Grant.pdf)

Did you read that? I just did, or at least skimmed it. The highlight is the timeline on page 64, where they have a timeline which puts operational deployment at from 2006 – 2014. I.e. those researchers thought they would have something up and running by now. That didn’t turn out quite to plan did it? This is how blue-sky thinking works: give us a lot of money and in 15 years we will have a working skyhook/moonbase/interstellar drive.

Earlier it is clear how far from actually delivering anything they were, or are, as a number of the technologies required for it are given as being at Technology Readiness Level 2, out of 9, which is basically still being worked out the drawing board, still a very long way from realisation.

[Absolute_Zero]

As a bit of a congenital heretic, I've long moaned about the hypothetical and ad-hoc, 'dark' entities. Far too early for claims of victory but this looks like a big fat nail in the coffin of dark matter.

http://www.dailygalaxy.com/my_weblog/20 ... atter.html

With similar reservations, I don't much like MoND either.

[Dio]

Yeah, there's an awful lot of experiments finding an awful lot of nothing when they go looking for it too.

[Absolute_Zero]

Yeah, there's an awful lot of experiments finding an awful lot of nothing when they go looking for it too.

Much has to be assumed regards the properties of the hypothetical WIMP, hence ditto on detection strategies. Maybe we just need bigger detectors. And after all, the WIMP is but one candidate; what of the Lightest Super Symmetric Particle, Neutralino, Majorana fermion, Planck-mass-sized black hole remnant, Sterile neutrino? Please send more money. /sarc

The advantage of the study above is that it (seemingly) obliterates the entire raison d'etre of dark matter.

Bring on the dark energy. My $0.02: standard candle fail.