So, space elevators

So, space elevators

Are they the key to a Space Program Revolution or are they nothing more than hotair monuments to popular science?

it would be very useful yes

>implying the government would pay for it
If anything, it'd be built from the moon to earth.

You mean a connection between the Earth to the Moon?

Disregarding the scale in question, how do you propose to have the Earth-side of the connection move across the planet to keep in place with the Moon?

>If anything, it'd be built from the moon to earth.

I kek'd

I don't think it would last long before some dickhead flies a plane into it. But yes, I think if we were to build one it wold spark a new age in space travel as transporting materials into space would become incredibly cheap.

Well, you see what had happen was...

You are a reasonable person.

Silly, unworkable idea.

Problem 1: building and maintaining it. The size would be like building a suspension bridge all the way around the equator of the world. The strength requirements push the limits on what is theoretically possible for ideal, entirely flawless materials.

Problem 2: climbing it. You might be picturing some "pretty fast elevator ride". Well, it's longer than a trip around the world, up a rope all the way. One very small climber (in relation to the mass of the cable) at a time, with things to deal with like friction losses. Remember, with an elevator, you're not in orbit until you reach GEO. You can't just drop off at LEO after a 100 km climb, you have to go all 36000 km. The ride would probably take weeks.

Problem 3: powering the climber. You can't just run wires down it, the transmission losses would be total. You don't want to put a heavy power source like a nuclear reactor into it, because you're trying to keep the mass to a minimum. Proposed solutions are things like lasers and microwave power transmission. This would be very inefficient.

tl;dr: a space elevator would cost more, be less versatile, take way longer to get working, lift much less, and be less energy efficient than reusable chemical rockets. In fact, it would probably be more expensive per kg lifted than expendable rockets, at any tech level.

I'm not sure in the life of the thing, you could ever lift the mass of stuff that needs to be put into orbit to build it.

The theory behind it is solid and the needed material has already been proven to exist.
The technical difficulties though are many and quite big, they may be unsolvable.
One of the less known: if one elevator breaks it would destroy all the others.

>You can't just drop off at LEO after a 100 km climb, you have to go all 36000 km.
What about bringing rockets together with you?

Getting out of the atmosphere is a significant benefit in getting to orbit, but you wouldn't gain an appreciable amount of the sideways component of velocity. It cuts about 2 km/s off your delta-v requirement, but there's still about 8km/s left. So your rocket only has to be about half the size, but it's still a fuckhuge rocket, and now your elevator has to be able to lift fuckhuge rockets.

Basically, for the same payload, you need at least ten times as much elevator, and all you get for it is about a 50% reduction in rocket cost.

Dammit NASA where's my ladder to heaven??

2 U
>correct usage

If you think a bit harder you'll see that you just said the stupiest thing on /sci so far.

A functional space elevator would be able to take thousands (if not millions) of tons of cargo into orbit, which is a magnitude of 1000x than we have now. And it could operate without any fuel, only electric power. So yes it would be very useful as it would immediately make 2/3rds of the complications of space travel irrelevant.

Which is why anyone is even bothering to look at it in the first place.

1. technical issue, can be figured out if good enough materials are discovered

2. nonissue, even a week to get into space is still getting into space. A higher payload capacity can compensate for this.

3. climber can be a maglev-type linear motor, possibly powered by a rectenna rather than an on-board power supply

>tl;dr: a space elevator would cost more, be less versatile, take way longer to get working, lift much less, and be less energy efficient than reusable chemical rockets. In fact, it would probably be more expensive per kg lifted than expendable rockets, at any tech level.

wrong, it would lift much more than any normal rocket. And that alone is why it's worth pursuing in the first place.

Well, cheap-er. Not incredibly cheap. You still have to pay the energy to escape the gravitational potential energy. But you don't have to do it with rockets, which means you get big savings by avoiding the rocket equation e.g. you don't have to have fuel for your fuel, and you also don't need to achieve orbit by massive lateral thrust. In practice, IIRC like 10% of the energy to achieve common orbit is just getting up, and the rest is the lateral motion to get into orbit.

Yea but rockets also go fast getting up there, a slow climb up an elevator is going to have lots of gravity losses.

Conversion losses from fuel into electricity into beamed power into w/e vs just burning the fuel in a rocket.

And then someone allah ackbars a missile into it, goodbye 50 billion dollars....

>And then someone allah ackbars a missile into it, goodbye 50 billion dollars....

Yep.

Good idea

Earth radius: 6,371 km
Earth circular geosynchronous orbit radius: 42,164 km
Ultra high voltage direct current transmission losses: 3.5% per 1000 km

Total losses
= 100% - [(100% - 3.5%) ^ ((42,164 km - 6,371 km) / (1000 km))]
= 100% - [(100% - 3.5%) ^ ((42,164 km - 6,371 km) / (1000 km))]
= about 72%
e.g. for every 1 Joule sent from the ground, a moving platform would receive only about 0.28 Joules.

And this analaysis assumes the electricity has to be sent the whole distance. Actually, because the platform moves from 0 to the full distance, total losses are probably close to about half of the above number.

So, probably 56% efficient electricial transmisison. Am I missing something? This seems to be the obvious answer - assuming you solve the materials problem, and various other political and technical problems. In other words, with a space cable in place, it seems quite obvious you'd just put an electrical motor on a platform to move the platform up and down the space cable, powered by an electrical cable running the length of the space cable.

>The ride would probably take weeks
As soon the pod is outside of the atmosphere 200 km/h isn't unrealistic. 36000/200 = 180 hours = 7 days.
Some sources claim 4 days is reachable.
>microwave power transmission. This would be very inefficient.
Not really, we have already reached 60%.
>space elevator would cost more
For a few launches probably, but if you want to send a lot more it's entirely possible it could become quite convenient.
Basically the more launches the less the cost per ton in orbit.

Well, you could just have a tether that reaches down to the Earth, but doesn't attach. It just stays up high enough not to hit anything on the planet. Make a platform there for docking and you can fly to it then ride up the elevator to the moon.

Too bad there's no materials that could withstand those types of forces.

>NASA is an F distribution

More dangerous than Muslims though are micro-meteors.

Those little fucks are everywhere and they'll shred a space elevator apart over the course of a few decades.

So unless you've got an auto-repair system in mind, your space elevator is going to have a decades-long expiration date.

>if good enough materials are discovered

THEY ALREADY EXIST BUT CAN'T BE PRODUCED IN THE QUANTITIES WE NEED

>Remember, with an elevator, you're not in orbit until you reach GEO

Only if you want to go into a circular orbit. You could theoretically drop off a bit sooner for an eccentric orbit with a low perigree, which would be ideal for further manoeuvres.

>theoretically

With a very high risk of fucking it up and burning in the atmosphere

God, materials engineering has got to be the most dry field there is but there's such a high fucking demand for it.

>Spending all day figuring out new ways to lay atoms together and seeing what comes about from it

If you don't think that's the coolest shit ever get the fuck out of my face