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Space Elevators Are Possible

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Re: Space Elevators Are Possible

#71

Post by Schwolop »

percentcer wrote: post #38
User8712 wrote: post #35

Earlier quoted context omitted.

1. How fast can a satellite travel up the tether? Let's say 50km/h, and it's going to an altitude of 35,000km. That's a month just in travel time. Using the tether for that period of time would be extremely costly. Currently, around 125 satellites launch a year, so they would need to be going up the tether at 500km/h, one after the other, day and night. And if we need to wait for a platform to descend, they need to b…

Couldn't you launch multiple satellites at a time?

Seems legit to me - a bunch of robots on the elevator that are each responsible for perhaps ten kilometres of travel, and they pass the parcel to the next one in line then move back down. You could launch way more things in pseudo-parallel that way.

Or just an up line and a down line like most cable cars.

Re: Space Elevators Are Possible

#72

Post by Fuxy »

Schwolop wrote: post #70
avmich wrote: post #19

The main problem with the elevator, in my opinion, for many years already is not in the strength of the material. After all, nanotubes are known for many years, and their properties are sufficient for the tether, so in principle it can be done. No, the main problem is with satellites. In fact, asking many times - what to do with existing or future satellites - I never heard a workable answer, even in principle. Just…

Couldn't the tether just have a friendly robot in charge of what I'll politely refer to as "catch and release"?

Fast moving objects are quite hard to catch even micro meteorites could do considerable damage a fast moving satellite would be a disaster.

The best option energy wise would be to have the satellite adjust its obit however that would deplete its energy reserves a lot quicker then not having an elevator to avoid colliding with.

Then again satellites should never have energy problems ever again since the can just be refueled cheaply via the elevator.

Re: Space Elevators Are Possible

#73

Post by mcv »

avmich wrote: post #19

The main problem with the elevator, in my opinion, for many years already is not in the strength of the material. After all, nanotubes are known for many years, and their properties are sufficient for the tether, so in principle it can be done. No, the main problem is with satellites. In fact, asking many times - what to do with existing or future satellites - I never heard a workable answer, even in principle. Just…

> The main problem with the elevator, in my opinion, for many years already is not in the strength of the material. After all, nanotubes are known for many years, and their properties are sufficient for the tether, so in principle it can be done.

You say that now, but I remember that years ago, when nanotubes were hailed as the material that would make the space elevator possible, people quickly pointed out that nanotubes were still not strong enough to carry their own weight over such a tremendous distance.

What changed? Why are nanotubes now strong enough?

Re: Space Elevators Are Possible

#74

Post by vesinisa »

nmc wrote: post #69

Why does this seem like a shamelessly unacknowledged copy-paste from [1]? Is it the other way around? Where is the original post? [1] http://motherboard.vice.com/blog/space-elevators-are-totally...

To me, it seems like this site Techblog copied Vice without giving any credit. Vice credits the original story to their in-house journalist, while Techblog.co seems like a news aggregation service. I am cool with news aggregation (think Google News), but they should definitely always credit the original source.

Re: Space Elevators Are Possible

#75

Post by userulluipeste »

User8712 wrote: post #35
avmich wrote: post #19

The main problem with the elevator, in my opinion, for many years already is not in the strength of the material. After all, nanotubes are known for many years, and their properties are sufficient for the tether, so in principle it can be done. No, the main problem is with satellites. In fact, asking many times - what to do with existing or future satellites - I never heard a workable answer, even in principle. Just…

1. How fast can a satellite travel up the tether? Let's say 50km/h, and it's going to an altitude of 35,000km. That's a month just in travel time. Using the tether for that period of time would be extremely costly. Currently, around 125 satellites launch a year, so they would need to be going up the tether at 500km/h, one after the other, day and night. And if we need to wait for a platform to descend, they need to b…

Many activities are affordable only as long as the true costs are not paid in full. The world had to allow massive burning of fuels, even if it's costly for the environment, only because the alternatives were not feasible yet. When better technologies allowed even a mild reduction of the pollution's effects (like combustion engine improvements, and later development of hybrid/electric solutions), things started to change and the reckless burn of fuel is now discouraged. Don't stop at the level of 125 launches per year, expect it to grow orders of magnitude, and the effects to grow proportionally. The market cost for fuel may be only $200,000 and it might get even lower, but the true costs... well, I think you got the idea.

Re: Space Elevators Are Possible

#76

Post by mcv »

mahranch wrote: post #6
kornork wrote: post #2

Great! What does the paper say about overcoming some of the problems that seem to make it tough, like the radiation that humans will receive riding up, or avoiding space debris? I'm assuming problems like building a rope strong enough to hold its own weight will be overcome, as well as developing the technology to climb the elevator.

Radiation is only a minor concern, astronauts in the space station experience similar radiation doses. I assume if it's cheaper to get things into orbit [with the elevator], it's also cheaper to shield the entire contraption. Climbing isn't much of a concern either, they've already run a bunch of tests and NASA has already awarded their prizes out for the challenge. The real issue is mass producing the carbon nanotub…

> Radiation is only a minor concern, astronauts in the space station experience similar radiation doses.

Why would they be similar? The space station is only in LEO. That's not remotely comparable to geostationary orbit, or the Van Allen belts.

Fortunately, shielding is a lot cheaper than on anything a rocket carries.

Re: Space Elevators Are Possible

#77

Post by twic »

ghayes wrote: post #23
avmich wrote: post #19

The main problem with the elevator, in my opinion, for many years already is not in the strength of the material. After all, nanotubes are known for many years, and their properties are sufficient for the tether, so in principle it can be done. No, the main problem is with satellites. In fact, asking many times - what to do with existing or future satellites - I never heard a workable answer, even in principle. Just…

Couldn't the elevation of the satellite be at a specific elevation that no other satellite is allowed to orbit at? I.e. using the z-axis to your advantage?

If by 'elevation' you mean 'latitude', then no. The elevator has to be on the equator. Or rather, the geosynchronous anchor has to be over the equator. I think the elevator cable could run to any point on earth, but it's going to hang as a curve where most of it is vertical over the equator, and so is in the way of satellites in equatorial orbits.

Re: Space Elevators Are Possible

#78

Post by twic »

bduerst wrote: post #21
avmich wrote: post #19

The main problem with the elevator, in my opinion, for many years already is not in the strength of the material. After all, nanotubes are known for many years, and their properties are sufficient for the tether, so in principle it can be done. No, the main problem is with satellites. In fact, asking many times - what to do with existing or future satellites - I never heard a workable answer, even in principle. Just…

The benefit with space elevators is that you can use mechanical energy to move payloads up the gravity well, as opposed to the chemical energy we use now. What do you think of rail guns, which use electrical energy?

They're still less efficient. With a gun, you have to put all your energy in as kinetic energy at the start of the trip, which means the payload leaves the earth at a considerable speed. Objects passing through the atmosphere with that sort of speed lose a lot of energy as drag.

There's a continuum between guns and rockets: you can fire a projectile with a motor on board. That lets you launch with a lower speed, but you have to lift fuel along with your payload. It's a tradeoff.

Space elevators step outside the tradeoff because they add energy to the payload during the trip, to avoiding the drag cost, but don't have to lift the energy as fuel, so avoiding the weight cost.

Re: Space Elevators Are Possible

#79

Post by userulluipeste »

Fuxy wrote: post #72
Schwolop wrote: post #70

Earlier quoted context omitted.

Couldn't the tether just have a friendly robot in charge of what I'll politely refer to as "catch and release"?

Fast moving objects are quite hard to catch even micro meteorites could do considerable damage a fast moving satellite would be a disaster. The best option energy wise would be to have the satellite adjust its obit however that would deplete its energy reserves a lot quicker then not having an elevator to avoid colliding with. Then again satellites should never have energy problems ever again since the can just be re…

"The best option energy wise would be to have the satellite adjust its obit"

The best option is to do the math first and plot an orbit that will avoid all the existing known objects for the given satellite's entire active period. And maybe a built-in decommissioning mechanism that will throw it back to the ground afterwards.

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