Wanted: practical launch vehicle, cheap!

Got a second-hand spaceship you need to sell?

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Post Sat Oct 31, 2009 11:11 pm

Re: Wanted: practical launch vehicle, cheap!

RickLewis wrote:If you had no brakes, would you go fast enough to burn up in the atmosphere? :o


NS: If we're still on the elevator model, then the counterweight that aided in your lift-off would also serve to counter-balance (slow down) your descent, no?

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Post Sat Oct 31, 2009 11:50 pm

Re: Wanted: practical launch vehicle, cheap!

RickLewis wrote:If you had no brakes, would you go fast enough to burn up in the atmosphere? :o

Okay… not that fast… lol. :lol:

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Post Sat Nov 07, 2009 4:35 pm

Re: Wanted: practical launch vehicle, cheap!

I thought a stumbling block with a 'space elevator/lift' is that we need a large 'weight' at the top, e.g. a large asteroid. So we need to get one of these first?

People are working on using lazers to power photo-electrical motors which could then 'drive-up' any cable.

NS's point about using the cable to produce the power is a good one. I suspect that producing a 'cable' strong enough that is also conductable may be a problem, but don't know how the properties relate. Although, if we could produce such a 'cable' then we could use it as an electrical generator that effectively produces free-electricity, as all we'd have to do is take advantage of the potential between the ground and space, and that the earth spins within a magnetic field.
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Post Sun Nov 08, 2009 1:30 am

Re: Wanted: practical launch vehicle, cheap!

arising_uk wrote:NS's point about using the cable to produce the power is a good one. I suspect that producing a 'cable' strong enough that is also conductable may be a problem, but don't know how the properties relate. Although, if we could produce such a 'cable' then we could use it as an electrical generator that effectively produces free-electricity, as all we'd have to do is take advantage of the potential between the ground and space, and that the earth spins within a magnetic field.

That's an amazing idea. Of course, there is no such thing as a free lunch, so I wonder where that free electricity would come from. For instance, would this arrangement fractionally slow the rate of rotation of the Earth? I can imagine that being the focus of environmental campaigns a hundred years from now!

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Post Sun Nov 08, 2009 2:56 am

Re: Wanted: practical launch vehicle, cheap!

The pulley-system going up & down from Earth to orbit would have to be spun in a circular motion so weights would need to be attached near Earth to keep the pulley system moving.

You cannot put a counterweight at the top, in orbit, because there would be 0-gravity there so the load would not do anything except maintain momentum in the load.

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Post Sun Nov 08, 2009 4:24 pm

Re: Wanted: practical launch vehicle, cheap!


rick wrote:That's an amazing idea. Of course, there is no such thing as a free lunch, so I wonder where that free electricity would come from. For instance, would this arrangement fractionally slow the rate of rotation of the Earth? I can imagine that being the focus of environmental campaigns a hundred years from now!


:oops: I thought this was 'old news', Teslas idea I think and been bandied about for quite a while now, at least in the sci-fi genre :) , and yes it would be the Earths rotation that would pay the cost.

realunoriginal wrote:The pulley-system going up & down from Earth to orbit would have to be spun in a circular motion so weights would need to be attached near Earth to keep the pulley system moving.

You cannot put a counterweight at the top, in orbit, because there would be 0-gravity there so the load would not do anything except maintain momentum in the load.
Fair enough. I was not thinking of a 'pulley-system' as I thought the problem was just how to get things up as its easy to get things down in a cable system, its just the braking tha'll be the issue. So you are right I did use the wrong idea as the asteroid would be there to keep the cable-end 'anchored' and in stable orbit I'd guess? I've also heard that the idea is that it acts as a factory and resource for building the actual cable as it'll have to be lowered to earth rather than built upwards, as that'd be a 'ladder' :)
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Post Thu Nov 12, 2009 12:25 am

Re: Wanted: practical launch vehicle, cheap!

On second thoughts, would the cable actually be moving relative to the Earth's magnetic field? :?

The cable runs between the ground and a geostationary satellite. It doesn't move relative to the ground, as that would be a bit of a hazard and also tricky for people to get on and off the space elevator! :mrgreen:

Therefore, surely the cable no more moves in the Earth's magnetic field than it would if it was just running up the side of a skyscraper?

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Post Thu Nov 12, 2009 2:44 am

Re: Wanted: practical launch vehicle, cheap!

Realunoriginal: You cannot put a counterweight at the top, in orbit, because there would be 0-gravity there so the load would not do anything except maintain momentum in the load.

NS: Of course, 0 gravity is a result of the orbiting satellite/pulley's motion through space, not the distance from the Earth's surface. Anyway, the counter-weight wouldn't need to be set at the very top (i.e. beside the pulley). It's at the lower half of the trip that the most lift (or braking force) is required, and that is where the counter-weight serves at its most 'weighty' effectiveness. The 'space-side' half of the up/down voyage would require the least amount of force, which might be had by some auxillary power source.

Hi
Arising UK: I suspect that producing a 'cable' strong enough that is also conductable may be a problem, but don't know how the properties relate.

NS: No need for one cable to provide both pull and power. An electically conductive cable could be attached, or internal, to the pulling cable.

ArisingUK: ...the asteroid would be there to keep the cable-end 'anchored' and in stable orbit I'd guess? I've also heard that the idea is that it acts as a factory and resource for building the actual cable as it'll have to be lowered to earth rather than built upwards, as that'd be a 'ladder'

NS: Good point. The sunside of this asteroid could also serve as the ideal location for a sizable solar array as one potential power source. Another power possibility is the temperature differential between planet surface and that of the asteriod, or sun-side/Earth-side of the asteroid. Power generation has been done with ocean layer temperature differences, but the instability of the sea surface made for stormy problems. With space, it would be much smoother sailing, and the temperatures more disparate, and hence more power productive.

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Post Thu Nov 12, 2009 2:48 am

Re: Wanted: practical launch vehicle, cheap!

BTW, those who are also having difficulty reading their just posted post due to its dark-on-dark display, just highlight by selecting the 'dark matter,' and it becomes instantly readable. :geek:

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Post Tue Nov 17, 2009 11:12 pm

Re: Wanted: practical launch vehicle, cheap!

RickLewis wrote:On second thoughts, would the cable actually be moving relative to the Earth's magnetic field? :?

The cable runs between the ground and a geostationary satellite. It doesn't move relative to the ground, as that would be a bit of a hazard and also tricky for people to get on and off the space elevator! :mrgreen:

Therefore, surely the cable no more moves in the Earth's magnetic field than it would if it was just running up the side of a skyscraper?

My understanding is that the Earth is spinning relatively to the MF(but I stand to be corrected) so the 'cable' if conducting would produce electricity. But if not, I think Tesla points out that it doesn't matter as the electrical potential between the ground and the higher MF is such that a massive current would be generated, unfortunately(I guess) this would mean massive surges or pulses of electricity, so some way of transforming or storing would be needed?
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