112 votes

Why is using a space elevator cheaper than rocket power?

With a rocket you have to carry the fuel with you. You are not just propelling the mass of the payload, but also the mass of the fuel. Installing a space elevator is a one-time event that can then be ...
called2voyage's user avatar
  • 23.7k
67 votes

Why is using a space elevator cheaper than rocket power?

In addition to not requiring fuel: A rocket has to accelerate to orbital speed. This takes a lot of energy. A space elevator can climb at a low, constant vertical speed (albeit for a very long climb)...
Hobbes's user avatar
  • 127k
67 votes

Why can't they just drop a solar winch down from a shuttle and have planes fly up and clip things on?

Because space isn't about going high; it's about going fast! For example, in a 400 km orbit (like ISS) you need a speed of about 27,500 km/h or 7.66 km per second. So if you would extend a ...
DarkDust's user avatar
  • 12.5k
63 votes

Why is using a space elevator cheaper than rocket power?

Here's a simple reason: Most of the rocket's fuel is used just to push the rest of fuel! It sounds strange for those unfamiliar with Rocket equation. The reality is, if we want to accelerate by ...
Heopps's user avatar
  • 9,041
53 votes

Why isn't it possible to build a space elevator at the north pole?

A "space tower" could be built at the north pole, but only if materials capable of supporting its weight were available. The "space tower" should be supported by the Earth's crust below it, but the ...
Uwe's user avatar
  • 48.9k
40 votes

Why is using a space elevator cheaper than rocket power?

It boils down to efficiencies of energy conversion and the cost of the technologies doing the conversions. If you have a given mass at Earth's surface that you want in geostationary orbit, you have ...
Tom Spilker's user avatar
  • 18.3k
29 votes

Would reusable rockets render the idea of space elevators useless?

A Space Elevator would still be amazingly useful The two factors that come to mind are forms of power and scale: Power With a space elevator connected to the ground, you could use the energy in ...
JMekker's user avatar
  • 391
25 votes

Why is using a space elevator cheaper than rocket power?

Ultimately an elevator is going to be more efficient, because it doesn't have to deal with gravity losses. Let me pose a question to you. What does it take for a rocket to hover in place like Blue ...
Evan Steinbrenner's user avatar
23 votes

Why does the material for space elevators have to be really strong?

Supplemental to the other answers; you are correct that the net force on the tether would be minimal, since the rotation of the counterweight would counteract the force of gravity. But, the ...
Maxander's user avatar
  • 331
20 votes
Accepted

Tethered geostationary orbit

At the geostationary orbit, the growth (gradient) of tension will be practically zero, but the value will be far, far from zero. Actually, it will be the highest in the whole tether. After all, the ...
SF.'s user avatar
  • 54.9k
19 votes
Accepted

Space elevator - cord thickness - why is the strength to weight ratio a problem?

It's the exponential nature of the equation determining the thickness. Let's discretize the problem to make it simpler to picture: you have a thread of very strong material, that has a self-breaking ...
SF.'s user avatar
  • 54.9k
18 votes

Why isn't it possible to build a space elevator at the north pole?

As an assist to the current answers. Try imagining an analogy: First you hold a rope with your arms held out horizontally and you spin. The result would be the rope spinning with you, tending ...
Lio Elbammalf's user avatar
18 votes

Why can't they just drop a solar winch down from a shuttle and have planes fly up and clip things on?

As an alternative to DarkDust's answer, if you start higher, at the classic altitude for space elevators, the end of your cable is indeed stationary to the air. But your cable needs to reach from ...
GremlinWranger's user avatar
17 votes

Why isn't it possible to build a space elevator at the north pole?

Because a space elevator would connect to a geostationary satellite. Geostationary satellites can only exist above the equator.
gerrit's user avatar
  • 11.5k
15 votes

Would reusable rockets render the idea of space elevators useless?

Rockets suffer from the tyrrany of the rocket equation. While a reusable rocket is great, you need to burn a lot of propellant for each kg of mass to reach orbital velocity. A space elevator can ...
Yakk's user avatar
  • 573
15 votes
Accepted

Why can't buoyancy of air be used to support a mega structure as an alternative to a space elevator?

Regardless of the accuracy of your calculations, what you propose isn't useful. Space isn't high, space is fast. Getting above the atmosphere only saves a little bit of energy; you still need to get ...
Mark's user avatar
  • 14.7k
14 votes

What tensile strength would be needed for a lunar space elevator?

Your question in its present form is unanswerable. Tensile strength is not the limiting factor of how space elevators are designed. Space elevators are designed to have an arbitrary constant amount ...
Knudsen Number's user avatar
13 votes
Accepted

Why would a space elevator / structure need to be in Geosynchronous orbit?

I've read a bunch on space elevators and from what everyone is saying, it would be required that the elevator is in geosynchronous orbit. The center of gravity of a space elevator would need to be at ...
David Hammen's user avatar
  • 73.8k
12 votes

Would reusable rockets render the idea of space elevators useless?

Whatever concept of space elevator you want to build, it requires you to transport massive amounts of material into space, so no. Having cheap launch vehicles is actually a requirement to building a ...
Rikki-Tikki-Tavi's user avatar
12 votes
Accepted

How about space ziplines

Unless the zipline stretches all the way to geosynchronous orbit (GSO), it will wrap around the earth and be destroyed. Remember that a typical satellite orbits the earth in about 90 minutes. Your ...
hdhondt's user avatar
  • 1,194
12 votes
Accepted

What are the calculations for gas transport to the Moon with a pipeline?

Pipelines two orders of magnitude shorter on Earth are usually divided into many compressor stations. But let's take a look at how feasible it is. At the very least, a compressor station would have ...
SE - stop firing the good guys's user avatar
12 votes

Could a space elevator launch a payload to a solar orbit?

Yes. If you could build the elevator, it could be used to launch satellites into prograde orbits with the same inclination as the Earth's equator. This includes solar orbits. Changing orbital ...
Woody's user avatar
  • 21.4k
11 votes

Why can't they just drop a solar winch down from a shuttle and have planes fly up and clip things on?

Have you ever flown a kite with a tail? The tail flies almost horizontally, kept up by the wind. It would hang at a steeper angle if you made it heavy, but what would then happen to your kite? Now ...
Peter - Reinstate Monica's user avatar
9 votes

Balloon Space Ladder

Summary: No, this won't work in any way, shape or form. And if you did get it to work, it'd be more expensive than using rockets. 10 reasons it won't work: Aircraft can get to an altitude of ~30 ...
Hobbes's user avatar
  • 127k
9 votes
Accepted

"Free energy" moving the space elevator possible?

Yes, but E' > E is dubious, at least in case of Earth. The point of reversal lies exactly at the GEO altitude, where the elevator moves at speed proper for that ...
SF.'s user avatar
  • 54.9k
9 votes

Would Starship be able to lift mass to orbit (both low and geo-stationary) cheaper than "any" space elevator?

Short answer The price of Starship is definitely going to make things cheaper, but a space elevator still is cheaper than Starship is - atleast in the long run. Long answer It is a bit hard to compare ...
The Rocket fan's user avatar
9 votes

Would Starship be able to lift mass to orbit (both low and geo-stationary) cheaper than "any" space elevator?

Bradley C. Edwards at NIAC published a detailed study of space elevators in 2000 that resulted in energy costs alone of \$220/kg. This is an easy order of magnitude above the aspirational operating ...
Christopher James Huff's user avatar
9 votes
Accepted

What Δv is needed to reach LEO from a space elevator?

A better, but not the best, answer: 2 km/s Since Woody put up an answer I consider absurd, here's a first cut that shows if you actually use your space elevator to go sideways fast instead of just ...
Erin Anne's user avatar
  • 10.8k
8 votes

How does the gravity of Earth change as you climb a space elevator?

If you want to consider the centripetal force too, you can do that by just adding a little more to the equation already suggested by Organic Marble: $$g_h=g_0 \left(\frac{r_e}{r_e + h}\right)^2 - \...
SE - stop firing the good guys's user avatar

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