Why getting back to the moon is so damn hard | Hacker News Reader

Why getting back to the moon is so damn hard

technologyreview.com

53 pointsmkm41644 comments

"the Saturn V rocket used in the Apollo program would cost about $1.16 billion"

The US military budget is over $500 billion per year. Cut 10% of the military spending and we could send a few missions to the Moon each year.

I always think it might have turned out better if the US hadn't tried to land a man on the moon. Instead if the goal had been to place a space station in permanent orbit around the moon. The USSR would have also been capable of this (even using Soyuz technology), leading to a permanent manned presence from both sides, and inevitable incremental development of the technology to keep people there.

And raising demand for building a space elevator, making further development even easier!

Why would that have caused more technology development than Skylab, Mir, or ISS?

What's the use of a lunar orbiting space station though? What science can you do in orbit of the moon that you can't do in orbit of the Earth?

Building a space station in Low Earth Orbit nearly killed NASA's budget for 20 years. Lofting all of that mass to lunar orbit would have added considerably to the cost. At least with the landers we got to bring back some regolith.

It doesn't need a use when two superpowers are using it as a proxy for war. What "use" did the Space Race have?

> Lofting all of that mass to lunar orbit would have added considerably to the cost.

Sure, but when you have to do it to keep up with a Space Race, you have 5% of your country's output being used to apply brains to the problem.

These are all rockets. What happened to attempts and more permanent space launch fixtures like: https://en.wikipedia.org/wiki/Space_elevator

I am under the impression many other methods of getting into space have been hypothesized but never attempted.

At least for the space elevator, we do not have the necessary materials to create it. There's been some hypotheses that carbon nanotubes could have the required strength, but we cannot produce strands long enough.

And there are other challenges, including:

- Wind: variable speed & direction, can be high.

- Ionosphere charges: the sapce elevator would essentially be a giant ground rod in the ionosphere… that might attract a few bolts of lightning.

You don't need to attach a space elevator to the ground. Keeping one end of the tether at 100,000 feet still makes access to space cheap without many of the security issues of a ground based tether.

Interesting. How do you get stuff to 100,000 feet? I'm imagining some sort of cargo helicopter but that is probably not at all the right idea.

We used a balloon to lift Felix Baumgartner 135,000 feet for his record jump [1]. Could this be scaled up for larger payloads?

[1] https://en.wikipedia.org/wiki/Felix_Baumgartner

Rockets or balloons can get to that altitude fairly easily. You could even build a second elevator that gets to 100,000 feet hanging off a balloons.

But, really it's just a security precaution to prevent terrorists or whatnot just flying into the thing.

Forget terrorist, an accident is more likely including earth quakes, tsunamis and storms and one of the biggest problems is that while building it might just be the easy part maintaining it and decommissioning it when the material fatigue sets in is a much more complicated mess.

Depending on the failure you might have a cable with a length greater than the earth’s circumference if we are putting it to a geostationary orbit falling down to earth.

For a space elevator to work it’s center of mass needs to be at or above geostationary orbit, depending on the counterweight at the end of the tether it will likely be at least 50,000KM long.

So what we need to do is start building down towards Earth from an anchor point

While the materials don't quite exist for a tether that can survive the forces needed to escape Earth gravity, the wiki you linked mentions the moon as a place where current materials could be used.

Makes me wonder about the near-term viability of an elevator on Mars, which IIRC has 2/3rd Earth's gravity...

The WP page describes the viability of a Martian in the paragraph before the Lunar one.

A launch loop is perhaps a better solution (meaning no material breakthrough needed):

https://en.wikipedia.org/wiki/Launch_loop

How exactly are you going to build a 50 mile tall structure? Current world record is Burj Khalifa, which is 828 meters tall, which is 0.51 miles. We're not even close.

On the ground.

Actually the answer is very interesting. The launch loop is a so-called active structure. The momentum of the rotor is raising the structure (notice that there are cables stays, but they are to hold it down, not to support it). In this way active structures can be made to any height, taller than material properties that limit static buildings.

At some point this technique will have to be used to make the next world's tallest building. Disadvantage is that the power must be kept on or the building collapses.

Relevant Isaac Arthur video:

https://www.youtube.com/watch?v=zSimYARyL2w&index=15&list=PL...

https://www.youtube.com/watch?v=5QLOAQmZbZs

Isn't the idea with the launch loop that it suspends itself by electrical force? The downside being that when it looses power it comes crashing down.

Other means of launching would be massive infrastructure projects, have huge power requirements, or simply might not be practical with current technology (as with a space elevator). I would guess that the most practical would be some sort of EM launch system + rocket/ramjet, if you could figure out how to transition from the first part to the second, but who knows.

Getting into space isn't hard. It's STAYING there that's difficult.

Relevant XKCD What If: https://what-if.xkcd.com/58/

This is why a space elevator needs to go much higher than low-earth orbit. Reach all the way to geostationary orbit, and then you are already going fast enough to stay in space.

A space elevator is a long ways off - assuming that human interest in space continues and technology develops at similar rates to today, I wouldn't expect something like that to be constructed for at least a couple centuries. Hopefully I'm wrong, I'd love to see something like that, but a project of that sort would make the space station look like a dinky house-boat in terms of scale and complexity. As crappy as rockets are, I expect we will continue to be using them for the duration of our lifespans.

What do you think about space elevators for asteroid mining? A large asteroid has a non-negligible escape velocity (e.g. for Ceres it's 500m/s), so taking stuff from them via regular rockets requires a significant amount of fuel. On the other hand, a space elevator could just be possible with our current materials and technology.

I think a mass driver in most cases would be simpler and more economical. We would use them on earth if we didn't need to worry about the atmosphere.

A Space elevator would require that the body spins fast enough that the centripetal acceleration would equal the gravitational acceleration. Ceres spins roughly every 9 hours - I haven't done the math but that seems like it could work in that case, but even so I would still vote mass driver.

Because $20 million is about 0.05% of what Apollo cost.

The rocket equation still applies. You still need a huge booster, and prices haven't improved all that much.

The first time we went was motivated (and funded) by the Cold War. Now someone has to come up with a viable business model.

I'm not smart enough to come up with one. Space tourism for the super rich?

I liked the idea of helium mining. Even if we couldn't ship it back, it could be used remotely for the applications that require liquid helium cooling. We're running out of helium, and sometimes liquid nitrogen doesn't cut it.

As a somewhat partial astrophysicist, remembering the increasing scarcity of helium on Earth is always amusing. It's the second most abundant element in the universe, after all. It's just that when you are near a star, light elements are easily heated and move away quickly towards the oort cloud and interstellar space.

Is there any reason why I cannot view this in In-Cognito/In-Private mode?

> Is there any reason why I cannot view this in In-Cognito/In-Private mode?

They want to track you to count articles you have read:

> Visitors are allowed 3 free articles per month (without a subscription), and private browsing prevents us from counting how many stories you've read. We hope you understand, and consider subscribing for unlimited online access.

However you can easily defeat this by:

A) Using a different browser session and just clearing it once you read 3 (they don't appear to be using advanced tracking).

B) The article is still actually sent, just remove the div in the body element with class "incognito-wall", then click on the body element and remove the "overflow: hidden" style.

C) Don't bother visit that site at all. I pretty much always surf incognito. Everything I know about that site is that they refuse to serve me.

Because of it I don't have the slightest interest to read anything from that site.

All it takes is someone to fund it..

What if we never went to the moon the first in the first place? I am joking of course, but I think it's weird we went to the moon in 1969 and in 2018 we can't do that anymore.

https://en.wikipedia.org/wiki/Capricorn_One

What part of this is "can't"? No one wants to spend the money, end of story.

https://en.wikipedia.org/wiki/Budget_of_NASA

Sorry, can you elaborate on the point you are trying to make?

People may think of, say, the Hubble space telescope as being a big deal and costing a lot, but when you realize there were lots of similar ones, only they were classified spy satellites, it puts into perspective how small NASA's budget is.

Surviving outside the Van Allen belt would require your spaceship to have 4ft thick lead walls.

I assume that is a big part of it.

This is mostly incorrect. The Van Allen belt is not some protective shield from radiation, it is an area of concentrated radiation. There is radiation exposure once you exit the sphere of Earth's magnetic field, but I believe it is lower energy than the belt's themselves.

>it is lower energy than the belt's themselves

Doesn't mean you can survive in it.

A dental x-ray is probably lower energy than the belts too but if you sit in front of one for 6 hours you will likely regret it.

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