We need a space elevator for constant raising of supplies to space. Even a few kilos at a time would be worth it long term.
Malfunctioning Russian supply podule EXPLODES above Pacific
The latest Russian Progress supply podule destined for the International Space Station has burned up over the Pacific, the Roscosmos space agency has confirmed. Progress M-27M, to give it its full title, ceased to exist at 5.04 Moscow standard time (just after 3am British time) as it entered the atmosphere over the central …
COMMENTS
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Friday 8th May 2015 14:16 GMT Remy Redert
It actually wouldn't. The bottom couple of kilometers would come down, the rest would burn up on reentry or go shooting out into deep space, depending on where it gets cut. Everything above the cut goes zipping off into deep space, everything below falls back into the atmosphere. Everything above ~50km is going to end up going fast enough to burn up on in the atmosphere.
You'd need to put the tether at the equator, so you'd probably attach it to a large floating platform. Attach some thrusters and you've got some rudimentary maneuverability to avoid collisions in the first place.
A severed orbital elevator would be very expensive, but it's not going to cause any serious damage back on Earth.
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Friday 8th May 2015 16:12 GMT mr.K
@Remy
What a fascinating thing to contemplate. Yes, everything above will go outwards, but I am not sure that it will go off into deep space, not even if you cut it above center of the mass (geo orbit). Essentially you will have an object in orbit where you have removed some of the mass and shifted the center of mass considerably in the non-uniform gravity field, but the velocity is unchanged. This will result in a high elliptic orbit, if it is rigid. I don't think it will be rigid. So you will at least for some time have a large whip spinning and yanking, possibly ripping itself apart, in an highly irregular orbit. Which is fine, not much so far out anyway.
If you sever the bit near the Atmosphere I agree that it will fall down and the bit furthest out will burn up before it hits. Something I would love to see and nobody will be able to compute the outcome of. The wire in front should push the air aside, no? So higher speed, so you might get friction heating to air on the sides instead of compression in front. I dunno, as I said, would love to see it.
But what if you cut it further out, lets say 10 000 km up. It would fall down, but it's velocity and altitude of the center of mass would indicate that it should be able to enter an elliptic orbit. However it is tied to the ground, but that bit would burn off some distance into the atmosphere. Which means the burnt off end would dangle into the atmosphere and drag the rest down unless it gets yanked out by the rest of the wire gaining higher speed. Which it would, but then it would probably bounce back and frequently touch the atmosphere. So for days or months the remaining wire would whip one of the ends into the atmosphere burning it off in what I will hope be a spectacular manner.
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Saturday 9th May 2015 01:24 GMT Robert Helpmann??
Re: @Remy
Something I would love to see and nobody will be able to compute the outcome of.
I would think this is exactly the sort of thing anyone contemplating the creation of such a structure would want to work out. As well, they would want to create contingency plans based on the modelling of such a catastrophe.
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Saturday 9th May 2015 01:43 GMT Allan George Dyer
@Remy Redert - So you're saying that, in the event of a cut, there will be ~50km of elevator cable hitting a major transport hub at terminal velocity? OK, not a dinosaur killer, but a hell of a lot more than a broken fingernail, probably dozens of deaths and enough public outcry to shutdown the orbital elevator industry for decades.
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Saturday 9th May 2015 11:52 GMT The Calvinator
But
what's the terminal velocity of something as necessarily light as a space elevator cable? I'm also not getting why people think it would burn up if severed near the bottom. It's stationary with respect to the atmosphere. If severed at low earth orbit shouldn't it fall more or less straight down at terminal velocity?
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Saturday 9th May 2015 22:28 GMT Adrian Midgley 1
You think it will come straight down?
onto the terminal below it, which has been constructed with the knowledge that a break is possible, and that that will cause severe damage?
It won't come straight down.
The cable low down is quite light.
Avoiding putting things in one direction along the plane of the cable - in an area which is likely to be mostly water - doesn't seem a major task.
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Friday 8th May 2015 13:59 GMT Anonymous Blowhard
Space Elevator to LEO?
Doesn't a "space elevator" need to be anchored to a heavy object in (or at least near) to geostationary orbit? My understanding was that the elevator's centre of gravity needs to be in geostationary orbit, so you need attach it to a heavy weight near geostationary to do this.
So a space elevator isn't 300km of string, it's 36,000 km of string; a bit more of an engineering challenge.
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Monday 11th May 2015 11:11 GMT cray74
Re: Space Elevator to LEO?
Doesn't a "space elevator" need to be anchored to a heavy object in (or at least near) to geostationary orbit? My understanding was that the elevator's centre of gravity needs to be in geostationary orbit, so you need attach it to a heavy weight near geostationary to do this.
Technically, you'd want the center of mass somewhat above geosynchronous orbit. It'd be kept under tension because Earth's rotation would spin it faster than the orbital velocity of that higher altitude. This does at least a couple of useful things: 1) the tension will help damp any vibrations in the tethers; 2) more importantly, when you add more mass on the cable - like payload and passengers - below the center of mass, the elevator won't be inclined to collapse. If the center of mass was exactly at geosynchronous orbit, the first payload to start climbing from the ground would lower the center of mass and start the collapse of the elevator. It wouldn't be an instant thing, but it is a problem, hence the value of raising the center of mass of the elevator above geosynchronous.
Also, the counterweight needn't be near geosynchronous orbit. Your goal is to get the center of mass at/near geosynchronous, but there are any number of ways to distribute mass to accomplish this. For example, it may be worthwhile to stretch the elevator's cable well beyond geosynchronous. This would allow you to sling payloads off the high end of the tether (at the expense of Earth's rotational velocity, but it's got plenty to spare). Or you could use a big counterweight, but the required mass of the ballast will drop the further away from geosynchronous orbit it is placed. Also, the counterweight would be moving above orbital velocity, so it'd produce a modicum of centripetal "gravity" where Earth would seem to be overhead. That might be handy for a resort, crew quarters, etc.
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Friday 8th May 2015 22:48 GMT Anonymous Coward
Space Elevators
Biggest problem with the Space Elevator, atm, is finding a material that could not only sustain the tension of 22,000 miles of its own mass against the Earth (the Space Elevator needs to be balanced, so it's Cog is in geosynchronous orbit, otherwise it'd be all over the place), but also needs to be producable to both an extremly high quality, and in a vast quantity.
Afaik, it's been suggested that Carbon nao-tubes just might be able to support their own 'weight', but even then, we don't really have much practical experience with Carbon nano-tubes beyond the micro-scopic, let alone a structure > 22,000 miles long/high.
It'll happen one day, but probably not in our life-times.
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Friday 8th May 2015 16:51 GMT Anonymous Coward
"well at least you can enjoy burnt and broken pieces of Labour of Scottish origin. "
I'm looking forward to the inevitable single party Scottish Soviet Socialists Republic. It's going to be great fun watching them learn the hard way. The Scots will be better off than in the Union, but only after seven years of Grecian decline, and then fourteen years hard slog of recovery.
Now, I'm torn whether England should offer Scottish Unionists asylum, or whether the reverse should be the case with forcible repatriation of ethnic Scots. I think the latter is fairer (we wouldn't want to starve their economy of skills), and it has the benefit of reducing English unemployment, the only downside is Her Maj would need to find an alternative pad to Balmoral. And in the meanwhile we need to find a way of persuading the Welsh to take their football away.......
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This post has been deleted by its author
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Friday 8th May 2015 14:40 GMT Anonymous Coward
Erm...
"The spacecraft would have accelerated to around 16,000mph causing the air in front of it to heat up and destroy the capsule …"
Actually, the spacecraft _decelerated_ to around 16,000 mph; its orbital velocity was greater.
You can look at it as an energy equation - it would have needed an input of energy to accelerate the spacecraft; the kinetic energy lost by the spacecraft, via its deceleration, was transferred to the air, which caused the heating.
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Friday 8th May 2015 22:33 GMT Anonymous Coward
Re: Erm...
A valid point - move inwards and orbital velocity increases, except that to move in you must slow down; accelerate and you'll move out, and then subsequently slow down... Dending upon the timing...
Let's say we start from achieving a perfectly circular initial insertion orbit... We we add energy (at any point, because we're in a perfectly circular orbit), which means we'll accelerate, which will take us 'out' ('in' & 'out' are a better way to think of gravity wells than 'up' & 'down'), because we've changed the equilibium of V vs. G, to the advantage of V at a tangent to G. The result, with a single input of energy, is that we'll end up in an elipitical orbit. So you'll need at least two burns; one to slow down and therefore move in, which will speed you up, into an elipitical orbit, which means that you'll catch up with a target ahead of you, but which then means you'll need a second burn to speed up, to take you back out, and back in to a circular orbit, ahead of where you would have been if you'd just stayed in orbit (phew).
The same works for a higher initial orbit but that's a waste of fuel.
In practice, you're not going to go for a circular initial insertion orbit - no need, what with current computational power available; Newton is good enough for LEO stuff until local RADAR and LASER comms can cope with mm accuracy, so in practice, unless there's a really good reason, then each launch to the ISS is quite a clever bit of choreography.
Most definitly written whilst under the influence of the icon...
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