
A Lunar Space Elevator Is Feasible and Inexpensive, Scientists Find - evo_9
https://observer.com/2019/09/moon-space-elevator-lunar-exploration-columbia-study/
======
vinaypai
It is not the fault of the students who wrote the paper, but this is an
exceptionally good example of terrible science reporting in popular media.
Practically every sentence of the article is wrong including multiple errors
in the title.

> Feasible & Inexpensive

The paper says "Building a spaceline would be a huge engineering challenge,
stretching the limits of current human capacity - but not exceeding them"
which is a far stretch from "feasible and inexpensive"

> Scientists Find

Second year graduate students

> In a paper published on the online research archive arXiv

An as yet un-peer-reviewed pre-publication draft that is being prepared for
submisson --- it says that right on top of the first page.

> After doing the math, the researchers estimated that the simplest version of
> the lunar elevator would be a cable thinner than a pencil and weigh about
> 88,000 pounds

They they actually said: "Let’s say such a line was made of a cable with a0
=10−7m2: its total mass would then be around 40,000 kg.". So yes, they're
right that it would be "thinner than a pencil". A cable with diameter section
of 0.36mm is definitely "thinner than a pencil". (They are misquoting them
saying thinner than a pencil _lead_... presumably referencing the lead in a
0.5mm mechanical pencil, not the lead in the regular pencil).

So yes, you could spend billions of dollars to build an elevator that could
lift ~100kg off the surface of the moon to GEO, and take months to years to do
it any any speed you're likely to achieve with a solar powered elevator
tethered by a 0.36mm thick line.

~~~
jkqwzsoo
> Practically every sentence of the article is wrong including multiple errors
> in the title.

>> But the Columbia study differs from previous proposal in an important way:
instead of building the elevator from the Earth’s surface (which is impossible
with today’s technology), it would be anchored on the moon and stretch some
200,000 miles toward Earth until hitting the geostationary orbit height (about
22,236 miles above sea level), at which objects move around Earth in lockstep
with the planet’s own rotation.

I see. The difference is they proposed to build their Moon space elevator on
the Moon, while others have proposed building the Moon space elevator on
Earth... /s

Also, obviously, even if the Lunar tether reaches the _altitude_ of
geosynchronous orbit, it will not have the _velocity_ of geosynchronous orbit
(it will have the angular velocity of... the Moon). Since the Moon orbits once
every 30-ish days and the orbital period of a geosynchronous orbit is 1 day,
an object at the end of this tether would not be in geosynchronous orbit. I'll
not bother to check and see if that orbit would have an apogee above 100, or
0, km.

In other news, Wet Streets Cause Rain.

~~~
ncmncm
We know the altitude of an object with an orbital period of a month: the moon
is there. An object going the speed of the end of the tether would drop like a
stone.

Objects in geosynchronous orbit are going 3000+ mph, where the end of the
tether would be at about a standstill. Still, if you managed to grab on, on
your way past, there would be plenty of swing and stretch. It would be hard to
keep it from swinging all over, all the time, as the tides had their way with
it.

~~~
s1artibartfast
This is actually a huge advantage. As I understand it, there would be no need
to accelerated to GEO before docking with the station. The earth side of the
teather would travel at about 10% of GEO. This is a large savings in energy
expenditure because kinetic energy is m*v^2

~~~
ncmncm
True, presuming you could arrange to be at the same place as the tether at the
same time. However, with it whipping around loose, how easy would that be?

Maybe a landing platform could be hung from it, helping to stabilize the end.

------
kuu
The key point:

 _the Columbia study differs from previous proposal in an important way:
instead of building the elevator from the Earth’s surface (which is impossible
with today’s technology), it would be anchored on the moon and stretch some
200,000 miles toward Earth until hitting the geostationary orbit height (about
22,236 miles above sea level), at which objects move around Earth in lockstep
with the planet’s own rotation.

Dangling the space elevator at this height would eliminate the need to place a
large counterweight near Earth’s orbit to balance out the planet’s massive
gravitational pull if the elevator were to be built from ground up. This
method would also prevent any relative motion between Earth’s surface and
space below the geostationary orbit area from bending or twisting the
elevator_

~~~
coldtea
> _instead of building the elevator from the Earth’s surface (which is
> impossible with today’s technology), it would be anchored on the moon and
> stretch some 200,000 miles toward Earth until hitting the geostationary
> orbit height (about 22,236 miles above sea level)_

Yeah, that's totally feasible and useful... /s

I hope those guys are not paid with public money...

~~~
echelon
> I hope those guys are not paid with public money...

I hope they are.

Engineering feats like this propel us as a species forward. Imagine the
material science involved in simply achieving the correct tensile strength.
Every thought that goes into this will find application in other areas.

I can't imagine this will get built, especially not in our lifetimes, but I do
hope that it is one of many such endeavors humans will embark upon.

~~~
coldtea
> _Engineering feats like this propel us as a species forward._

Note that there are no feats thus far...

~~~
asavadatti
What device did you type your comment on?

~~~
coldtea
Not a space elevator or anything designed by the team in the article, I can
assure you of that...

It's not like there can't be some research that's realistic and have tangible
(even if remote) goals, like e.g. rocket research in the 20s and 30s, and some
that's just theoretical filler -- and that we can never tell one from the
other...

------
kerkeslager
I have only been following space elevator research cursorily, but it seems to
me that this proposal lacks the most compelling reason for building a space
elevator: breaking the bonds of Earth's gravity well. The most expensive part
of space travel now is getting from the earth's surface to a stable orbit, and
a space elevator from the moon does exactly nothing to reduce this cost.

It does still have some benefits, i.e. if I'm not mistaken you could still use
this elevator to "slingshot" spacecrafts on interplanetary trips, and it would
make it cheaper to get to and return from the moon. But it's unclear (to me)
whether these benefits could actually be realized when the cost to get to the
space elevator in the first place is still so prohibitive.

I guess what I'm saying is that this is just the cost analysis, not the full
cost/benefit analysis. The costs may be a lot less than a space elevator from
the surface of the earth, but the benefits are a lot smaller too.

~~~
scardine
Leaving moon's gravity well may be cheaper than getting to space from earth
but it is far from free.

With a space elevator in the moon you can use raw material from the moon to
assemble huge stations and ships in space.

~~~
Shivetya
Not a snark, but how long before the is some sort of preservationist,
nationalist, or other, declaration that the moon isn't they to be exploited.

I do not know how much is in place already with regards to regulation but you
can be damn sure nations and people will be tripping over themselves once
someone does find a means to make money using the moon for resources.

the fantasies of space elevators appeal the geek/nerd in many of us but as a
world we are far from the need of one if not too far from being united to
having one. throw in there are just enough parties with the means to damage or
destroy the ground side of one if ever built

~~~
scardine
I just finished reading the "Mars Trilogy" by Kim Stanley Robson where there
is a tension between the "red" and "green" parties (first group want to keep
Mars pristine, the other want to terraform it). The reds even sabotaged Mars
space elevator in order to slow down emigration.

I guess it will be like Antarctica, where several countries made territorial
claims[1] over it, many of them overlapping.

The UN's 1984 Moon Treaty[2] is dead letter - it has never been defied but is
defunct in practice as none of the most prominent space-faring nations have
ratified it.

If someone settles in the Moon you can refute their claims over territory
there but what else can you do? Set an embargo? Send a military force and try
to kick them out? Nuke them? Someone with knowledge and resources to colonize
that desolated rock in space is not an adversary to be underestimated...

[1] [http://www.antarctica.gov.au/about-antarctica/people-in-
anta...](http://www.antarctica.gov.au/about-antarctica/people-in-
antarctica/who-owns-antarctica) [2]
[http://disarmament.un.org/treaties/t/moon](http://disarmament.un.org/treaties/t/moon)

------
m4r35n357
Glanced through the paper quickly, couldn't find _any_ references to
elasticity or strain, just the breaking stress. I would have thought that
would be in the calculations somewhere, considering this thing would be a
quarter of a million miles long! Maybe I'm just being a killjoy . . .

~~~
jacquesm
Think of the breaking stress as the harder problem to solve.

~~~
inetknght
Breaking stress would cause catastrophic failure, for sure. Nonetheless when
you're talking _hundreds of miles_ of cable, elasticity can make for some
fairly profound failure modes too.

------
dmckeon
First sentence of the paper:

> 1.INTRODUCTION For a vehicle travelling in empty space it’s momentum, as
> well as it’s energy, comes from it’s fuel.

His, hers, its - are all possessives.

This is why one should have papers for publication, a CV, or a résumé
proofread by someone who can spell correctly and understands grammar. Spell-
checking software is fine, but it will not catch everything. If it is
important, read it aloud to yourself, then get a friend to read it aloud to
you. Yes, here the intended meaning is obvious, but this left me wondering
about the accuracy of the rest of the paper, which is not a good start for any
reader of anything written.

------
ColinWright
The comment[0] I made a previous time this was submitted[1]

> _One major problem with the classical Earth based Space Elevator is the
> problem of security. It wouldn 't take much (relatively speaking) for a
> terrorist organisation to create a credible threat._

> _A Moon-based Space Elevator wouldn 't have that problem._

[0]
[https://news.ycombinator.com/item?id=20977269](https://news.ycombinator.com/item?id=20977269)

[1]
[https://news.ycombinator.com/item?id=20977142](https://news.ycombinator.com/item?id=20977142)

~~~
jobigoud
The cable is held by tension from the Moon anchor point right, so I wonder
about ramming a satellite a few hundred kilometers above the endpoint. If the
cable is severed in this way, will the loose end fall straight to Earth
causing damage? It's not itself in GEO orbit, it's moving at Moon orbital
speed and pulled by Earth gravity. So I feel it should fall pretty much
straight down.

~~~
ColinWright
Yes, clearly there are failure modes that can be provoked, and breaking the
cable close to the Moon's surface will result in this thing falling to Earth
from a great height.

But most terrorist organisations short of governments won't have the
capability to provoke such damage, and it's likely that most of it will burn
up on re-entry, and possibly can be designed explicitly to do so.

------
SaturateDK
Was on HN 10 days ago:
[https://news.ycombinator.com/item?id=20895443](https://news.ycombinator.com/item?id=20895443)

------
t_fatus
Without considering the fact that the orbit of the Moon is not circular, this
only helps reduce the delta-v needed to go from the surface of the earth to
the surface of the moon by ~3.2km/s, but we still need ~12-14km/s to go to
GTO/GEO.

~~~
t_fatus
However since the moon period is not the same as a GEO period, maybe the fact
that you could juste 'catch' the end of the cable before falling back to earth
without having the speed to maintain at GEO could help you save some delta-v.

~~~
extropy
That's essentially what GTO is - an orbit going close and fast at one side and
going high and almost stopped at high side.

Going directly up means over 1h of fighting earth gravity. So need Isp >
3600\. Much cheaper to go for orbit.

~~~
logfromblammo
An elliptical orbit that intersects the surface of the massive body at the
periapsis side is fine, if you can change the orbit when you reach apoapsis.

But if you miss the cable, you're boned.

------
excalibur
1\. Build a space elevator anchored to the moon.

2\. Mine raw materials on the moon.

3\. Send them over the elevator piece by piece to earth orbit.

4\. Assemble the counterweight for an earth-space elevator in orbit.

5\. Have TWO space elevators, one to get you to orbit, another to take you to
the moon.

6\. Colonize the solar system or whatever.

~~~
vinaypai
Getting the counterweight to orbit is not the hard part of building an earth
space elevator. The hard part is the 36,000 km cable from the surface of the
earth to geostationary orbit that can support its own weight against earth's
gravity.

There are a few experimental materials like carbon nanotubes that have the
right tensile strength to weight ratio, but we aren't anywhere close to making
them in more than microscopic lengths.

~~~
excalibur
That's okay, we'll keep ourselves occupied with the moon mining part, you work
on the cable.

------
neuromancer2701
This a moon-GEO elevator which may have its advantages but it does not help
you get out of the planetary gravity well.

~~~
loudmax
Exactly. Overcoming Earth's gravity well is the reason building a space
elevator is such an exciting prospect.

The geosynchronous orbit is about a 10th of the way to the moon, so this moon
elevator would go 9/10ths of the way toward the Earth. That's significant but
it's precisely that remaining 10th of the way where the vast majority of
energy expenditure occurs. If you can make it from the surface of the Earth to
geosynchronous, then making it to the moon is relatively cheap.

~~~
narag
Not orbit, the Moon doesn't orbit the Earth in one day, but a month. The cable
would be almost stationary compared to orbit. That needs less power.

~~~
peeters
Less, but not much less. Around 12 km/s instead of 14 km/s.

~~~
narag
Escape is 11.2 so something must be off.

Edit: actually you don't need any specific speed. Reaching orbit does, around
9 km/s for low orbit, vertical uplift doesn't.

------
kerkeslager
So if the elevator from the moon extends toward earth and is held in place by
Earth's gravity... why stop at geostationary orbit height?[1] Wouldn't you
want to extend the elevator as close to the earth as you could go? It seems to
me that the closer to the earth the elevator goes, the more Earth's gravity
keeps its location stable, and the easier it is to get from Earth's surface to
the tip of the elevator.

It seems to me you'd want to stop the elevator just shy of the strength
limitations of the cable material (with some margin of error).

[1] I suspect the article may just be wrong about this, since as others have
pointed out, the moon has an elliptical orbit that is not geostationary.

~~~
ARandomerDude
*Assume the ball and the man are point masses, the man is standing on frictionless ice, and there is no drag when the ball is thrown.

------
mLuby
Lot of talk about how

1\. a Moon elevator is pointless without an Earth elevator, and

2\. we can't build an Earth elevator with today's technology.

However we can build an _orbital ring_ around Earth with today's technology,
and it'd be much better than space elevators.

[Video]
[https://youtu.be/LMbI6sk-62E?t=254](https://youtu.be/LMbI6sk-62E?t=254)

[Paper]
[https://jenda.hrach.eu/f2/Low%20cost%20design%20of%20an%20or...](https://jenda.hrach.eu/f2/Low%20cost%20design%20of%20an%20orbital%20ring%20-%202017-1.pdf#page=5)

~~~
empath75
That paper doesn't strike me as being particularly credible.

------
sathackr
If one end is tethered to the moon, and the other end is in geostationary
orbit...you're gonna have a bad day. The moon is not in geostationary orbit.

Not an orbital scientist but doesn't seem that will work out very well.

~~~
Majestic121
It would be an issue if you expect it to always end up to the same place, but
if you don't care where the elevator ends on the Earth side, because you know
it will be in your area at regular intervals, it can be dealt with.

I'm not sure why they picked geostationnary orbit distance if they don't look
for locked location though, it seems the risk of colliding with objects would
be greater at this height

~~~
extropy
Since the tether will be moving a lot slower than sattelites in geostationary
orbit, and the risk of collision, I assume stopping just short of
geostationary is the closest that will be deemed reasonably safe.

------
34679
What cable weighs less than half a pound per mile?

200,000 miles 88,000 lb cable

No friggin way.

~~~
mkl
Yes, that seems to have been misunderstood. The cable that weighs 88,000lb (in
the paper, 40,000kg), has a cross-sectional area of 10⁻⁷m²! That won't stand
up to much use.

If I'm reading (skimming) right, they say "this would only allow transport of
weights up to 100kg".

~~~
jandrese
100kg seems like a barely usable amount of lift. It means you need an in-orbit
assembly system for most things you want to launch and I'm pretty sure you're
not going to be able to launch a person with life support gear.

~~~
mkl
Yes, it's hard to imagine a cable-crawling machine and its power source being
under that mass limit, let alone a payload.

~~~
jandrese
I had assumed the cost of the crawler was already included in that 100kg
figure, but if not then yeah, that's even more marginal. It really can't bring
its own fuel source along, it needs to work on beamed power or maybe a current
between two parallel tethers.

------
timthorn
Zephyr Penoyre (one of the paper's authors, then at the IoA in Cambridge) gave
a talk about his proposal for a Moon-tethered spaceline earlier this year, and
is available here:
[https://upload.sms.cam.ac.uk/media/2921572](https://upload.sms.cam.ac.uk/media/2921572)

The talk starts with a polemic about the way research is done, but the physics
starts about 16:40.

------
umvi
> Future moon travelers will still have to ride a rocket, though, to fly up to
> the elevator’s dangling point, and then transfer to a robotic vehicle, which
> would climb up the cable all the way up to the moon.

And... how long is that going to take? A few months? A year? 200,000 miles is
like going the circumference of the earth 10 times and I can't imagine a
machine attached to a pencil-thin cable could go very fast

~~~
hguant
If you assume the cable car is moving at a constant 60 miles per hour, about 4
and 1/2 months (138 days). The current fastest elevator in the world (in the
Burj Khalifa) moves at 22 mph; taking that up would take you about a year.
However, I'm told by a friend who used to work at Otis (the company that made
the Burj Khalifa elevator) that the limiting factor on elevator speed is the
comfort factor - there's a hard cap on the acceleration a standing person can
comfortably take, and the course of the elevator is generally pretty short, so
you don't have time to build up a decent head of speed.

Presumably we can do a little better than that

~~~
jaclaz
As a side note, usually cables used in lifts/cablecars/cranes/etc. have a 5x
(or even in some cases higher) factor of safety, i.e. the cable needs to
resist at least 5,000 Kg of traction in order to be used for a 1,000 Kg
weight.

Part of this high factor is because cables wear down during use (and they are
usually inspected _for all their length_ every 6-12 months), particularly when
relatively high travel speed is used.

------
davidhyde
One disappointment with space elevators is the speed at which you can safely
travel along them. For example, if you were to travel at 1000 km/h it would
take 15 days to get to the moon and just under 2 days to get to geostationary
orbit (if there was also an elevator for that)

~~~
gameswithgo
That might be disappointing for human travel, but for cargo its great. As long
as throughput is high the latency is no big deal.

~~~
perl4ever
But you can't get high throughput unless you have a large capacity in terms of
mass. It's easy to say "cargo", but if the only cargo it can carry is a flea,
not so much.

------
drakythe
Non scientific observation: The Earth and Moon are not a consistent distance
apart. XKCD What-If 157 ([https://what-if.xkcd.com/157/](https://what-
if.xkcd.com/157/)) neatly illustrates this with the idea of connecting a pole
from the earth to the moon, noting that "it's enough that the bottom 50,000 km
of your fire station pole would be squished against the Earth once a month".

I realize XKCD isn't precisely accurate, but even if 50,000 KM is a /rough/
estimate Geostationary Orbit Height is still around 35,785 km, significantly
less. As the moon and earth move closer this Lunar Space Elevator would need a
winch capable of taking in 50,000 KM (or perhaps less, but not much or the
earth's gravity would become much stronger on the 'station' end and the rope's
strength calculation would be off) of "rope" or we're all gonna have a bad
time.

------
isoprophlex
However wonderfully grandiose these elevator pitches sound, I'm always left
wondering: what happens when some space debris hits the thing? Instant Kessler
syndrome?

~~~
extropy
No, dual cosmic lashing. One end hitting the moon the other one earth.

On earth side the atmosphere will take the worst of it, moon will hurt...

Also there is hardly any space debris beyond geosynchronous.

~~~
isoprophlex
Interesting, that makes the case for a moon -> geostationary stronger...

------
yk
From the paper [0]:

> Values taken straight from Wikipedia.

:)

[0]
[https://arxiv.org/pdf/1908.09339.pdf](https://arxiv.org/pdf/1908.09339.pdf)

------
danschumann
Let's not call a 200,000 mile, multi billion dollar cable "easy", but let's
say it's doable, important, and absolutely necessary!

~~~
coldtea
In what way it's any more "doable" than e.g. digging a tunnel through the
Rockies with a spoon (or worse, a spork), given our current technology?

------
wbhart
Does someone know what the difference in deltav would be to get to
geostationary orbit from earth vs getting to lunar orbit from earth? A
citation would be helpful.

I've tried looking this up, but from previous comments on this paper, I infer
that I am misunderstanding something.

~~~
t_fatus
GTO: ~11.5 km/s

GEO: ~14 km/s (but you don't need that speed since the end of the cable is
much slower, orbit period of ~28days instead of 24 hours)

GEO <-> moon surface ~3.2km/s

superbe reddit source:
[https://www.reddit.com/r/space/comments/1ktjfi/deltav_map_of...](https://www.reddit.com/r/space/comments/1ktjfi/deltav_map_of_the_solar_system/)

~~~
wbhart
Thanks but that's not what I asked.

I asked what is the difference in delta-v between getting from the surface of
the earth to GEO vs getting from the surface of the earth to Lunar orbit.

The answer is, there is almost no difference.

------
dghughes
Would the Earth end still be in geostationary orbit even with a variation of
the Moon's orbit by 43,000 km?

And if the Moon end snapped would that mean the entire 380,000km cable would
crash to Earth? How much weight and what velocity would it be? Crazy!

~~~
sudhirj
It's 40,000kg, so about 400 heavy people or a handful of elephants. Might not
be fun if you're under it, but not particularly damaging to the planet.

~~~
dghughes
But what velocity would it be traveling?

Project Thor aka "the Rods from God" concept is a satellite with 20'x1' 76,000
lb (34,000kg) tungsten rods. No explosives just pure mass and kinetic energy.

From low Earth orbit they would travel at Mach 10. Supposedly at impact each
rod would release the same energy as a small nuclear bomb.

------
ethagknight
totally unrelated but is there an opportunity or reason to tow a load to space
via cable behind a "rocket tractor-trailer" instead of rockets pushing from
behind? Maybe the tractor is a quadcopter or octocopter but rockets instead of
electric props. Rocket engines would need to aim their exhaust plumes outward
slightly to avoid melting the tow cable, but it would seem like a tow cable
could provide some level of suspension (stretch) to the load, reduce
structural requirements since materials dont require stiffness in tension.
Maybe there is no benefit compared to just pushing the load as is traditional.

------
dkrudy
[https://what-if.xkcd.com/157/](https://what-if.xkcd.com/157/) A fire pole
would be slightly cooler.

------
thecleaner
I think given the lack of precision in this article it is better to replace
the sensational news article with the actual arxiv paper.

------
andyford
how to get to moon without a rocket: 1\. go to moon and install thin wire on
moon and dangle it toward earth 2\. use a rocket to reach wire

------
sfjailbird
Wonder how fast the 'elevator cart' would be able to move. Considering that it
takes a rocket several days to reach the moon.

~~~
ed312
Most of the time the rocket isn't firing - you have a few minutes of burn to
change your delta v, then you just gotta sit and wait before decelerating into
orbit (or landing). Assuming the cart was attached to a powered cable you
could in theory constantly accelerate until half way, then constantly
decelerate. Possibly this would allow you to make the trip faster (unless you
had humans on board, then you're probably stuck with short accelerating
bursts).

~~~
brians
I'm pretty sure humans can take 1 g continuous.

~~~
pmontra
I'm not sure if the cable can take it: 1 g yields pretty large speeds quickly.
Somebody already made the math at [1]

[1] [https://space.stackexchange.com/questions/840/how-fast-
will-...](https://space.stackexchange.com/questions/840/how-fast-will-1g-get-
you-there/5016#5016)

------
adhoc32
How about moving stuff _from_ the Moon back to Earth. Harvesting the Moon for
rare materials is going to be relatively cheap.

~~~
jacquesm
What rare materials would these be?

The only thing that comes to mind at the surface would be Titanium but even
there the economics would probably not make sense if your goal is to use the
material on Earth.

~~~
MagnumOpus
> What rare materials would these be?

Every material is rare outside of gravity wells. Even plain steel, aluminium
or magnesium cost >$1000/kg if you want them delivered to geostationary orbit.
So this material would not be for earthbased construction, it would be for
space factories, space-based solar microwave powerplants, spaceships etc.

~~~
jacquesm
Absolutely, but GP said to import those materials _back to earth_.

------
tiku
Is there a sweet spot where both gravity's will pull it towards eachother?

~~~
jacquesm
The 'sweet spot' is called the Lagrange point.

[https://en.wikipedia.org/wiki/Lagrangian_point](https://en.wikipedia.org/wiki/Lagrangian_point)

------
mesozoic
Ok could be good but the real issue is leaving earths atmosphere.

------
codesnik
if the tether would be visible in sun light, and because of eccentricity of
moon orbit not always pointed directly to earth, it could look interesting
from earth.

------
lidHanteyk
Wouldn't a skyhook work better on the Moon?

------
Alex63
Now _that 's_ a zip line!

------
detcader
So inexpensive: Only a few billion dollars not going to people and communities
who actually need it.

~~~
jaimex2
They'd just blow it on booze and drugs right?

~~~
detcader
"And you know lately, I've been thinking about how I love Jesus / Because
Jesus was a dirty homeless, hippie peace activist / And he said, 'Drop out and
find God' to anybody who would listen / While turning water into space
bags..."

------
HenryKissinger
I'll believe it when I see it.

------
trickstra
> proposed the idea of a “lunar space elevator,” which is exactly what it
> sounds like—a very long elevator connecting the moon and our planet.

No that's absolutely not what a space elevator is

~~~
onion2k
A space elevator is a device that lifts things to space along a static cable.
A space elevator on Earth lifts things to outside of Earth's orbit. A space
elevator on Mars lifts things to outside of Martian orbit. And a space
elevator on the moon lifts things outside of lunar orbit. This definitely _is_
a space elevator by any definition of said technology.

~~~
trickstra
> connecting the moon and our planet

