Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

If We Can Put a Man on the Moon, Why Can’t We Put a Man on the Moon?

wsj.com

Post reply on HN
Print view View original

51–60 of 246 posts

Re: If We Can Put a Man on the Moon, Why Can’t We Put a Man on the Moon?

#51

Post by pvaldes »

thaumasiotes wrote: post #42
TylerE wrote: post #8

THere is little POINT in putting a man on the moon after you've done it. We have plenty of moon rock to run experiments on. Any micro/low gravity experiment can be run cheaper in LEO. There aren't any valuable resources there to exploit. It's a bit like asking why we don't build a habitat on the bottom of the Marians Trench - we COULD, but why WOUDL we?

> It's a bit like asking why we don't build a habitat on the bottom of the Marians Trench - we COULD, but why WOU[LD] we? This is overstated. We could build a habitat on the moon. We cannot build a habitat on the bottom of the ocean; that's much, much more difficult.

But would be much more rewarding, because we know that this other "moon" has living creatures that are practically unknown to us.

Re: If We Can Put a Man on the Moon, Why Can’t We Put a Man on the Moon?

#52

Post by perilunar »

RikNieu wrote: post #45
phillc73 wrote: post #44

Earlier quoted context omitted.

If the benefit of manufacturing optical fibre cables in a low gravity environment was so great, would it be more economically viable to build a 'low gravity' factory on earth?

How would one produce low gravity on earth?

Two methods: the vomit comet [1], and shot towers [2].

1. https://en.wikipedia.org/wiki/Reduced-gravity_aircraft

2. https://en.wikipedia.org/wiki/Shot_tower

Re: If We Can Put a Man on the Moon, Why Can’t We Put a Man on the Moon?

#53

Post by maccam94 »

T-A wrote: post #38

Edit: nope, looks like it's this one: "Stepping Stones: Economic Analysis of Space Transportation Supplied From NEO Resources" https://www.nasa.gov/sites/default/files/atoms/files/eso_fin... --- I think the report in question is "NASA's In Space Manufacturing Initiatives: Conquering the Challenges of In-Space Manufacturing": https://ntrs.nasa.gov/search.jsp?print=yes&R=20170011108 These may also be interesting: "NASA…

I really want to see asteroid mining prioritized, as well as a space station capable of permanent human habitation (either partial or full gravity). A space station is also preferable to another planet for our next big space endeavor IMO because it is easier to get materials to and from it (no extra gravity well to deal with). Also, I feel like a lot of people think "ah, everything has to be done differently because space is a zero-G environment", but I bet it would be easier to adapt a lot of traditional technologies, engineering processes, and biological elements in a rotating station. Once we have the ability to do fabrication and construction in space, everything becomes much cheaper. Lastly, if researchers need to experiment in zero-G, we could construct zero-G modules adjacent to the center of the ring for experimentation.

The primary blocker for a rotating station as far as I know has been the mass requirement. If you have a structure above a certain rotational speed with a radius that is too small, the occupants are likely to become nauseous. From the research I've seen, the minimum size for a viable rotating station would be about 600 tons[1]. Moving that amount of mass into orbit would have been extremely expensive, but Falcon Heavy could launch it for under $1.5B, and the BFR for even less.

[1]: http://www.nss.org/settlement/space/GlobusRotationPaper.pdf (page 22)

Re: If We Can Put a Man on the Moon, Why Can’t We Put a Man on the Moon?

#54

Post by jpatokal »

Al-Khwarizmi wrote: post #50

This seems to happen to a lot of things. In my city (random Spanish mid-sized city, around 250K population) there is often debate about building a light rail or tram public transport line. But it is always dismissed by the administration for being too expensive, pharaonic, disproportionate for a city of this size, etc. Doing some research on the history of the city, I discovered that not only there were several tram…

Classic trams and modern light rail are different beasts.

Trams were popular worldwide back in the days where automobiles were far too expensive for most people and buses hadn't taken off yet, and since they were the only practical means of transport for medium distances, even small cities had massive ridership. They also ran right on the road, sharing space with cars, which was OK because there were a lot less cars and cars were not meaningful competition.

These days cars are affordable, and light rail has to be better than cars to be competitive, and do so well enough to entice a significant portion of the population out of their cars to be affordable. In practice this means dedicated right of way, which is far more expensive to purchase and fit out as a rail line than just laying some rails on an existing street. And of course modern safety, environmental and just plain bureaucratic regulations also inflate the prices of public works considerably compared to the good/bad old days, particularly in the US.

Re: If We Can Put a Man on the Moon, Why Can’t We Put a Man on the Moon?

#55

Post by Fnoord »

Al-Khwarizmi wrote: post #50

This seems to happen to a lot of things. In my city (random Spanish mid-sized city, around 250K population) there is often debate about building a light rail or tram public transport line. But it is always dismissed by the administration for being too expensive, pharaonic, disproportionate for a city of this size, etc. Doing some research on the history of the city, I discovered that not only there were several tram…

In early 20th century:

1) Communities were more local and relevant than today. This also means travel was more local and relevant.

2) Trams didn't have as much competition with other viable, automated means of transport.

Re: If We Can Put a Man on the Moon, Why Can’t We Put a Man on the Moon?

#56

Post by maccam94 »

abecedarius wrote: post #9
TylerE wrote: post #8

THere is little POINT in putting a man on the moon after you've done it. We have plenty of moon rock to run experiments on. Any micro/low gravity experiment can be run cheaper in LEO. There aren't any valuable resources there to exploit. It's a bit like asking why we don't build a habitat on the bottom of the Marians Trench - we COULD, but why WOUDL we?

Lunar resources could have great value just by their location. The energy cost to lift them into space is much lower than from Earth. Doing anything ambitious in space would require a lot of material, which has limited our ambitions since the 1970s. (Asteroids might serve better, though: a wider variety of stuff, comparable in energy cost but farther away.) I wish the damn article would link to this new report, or at…

I'm not sure what the delta-V is like to get materials from an asteroid vs the Moon, but I'd expect there is much more variety of resources on asteroids. I think an orbital station is also more attractive than the Moon from a delta-V standpoint.

Re: If We Can Put a Man on the Moon, Why Can’t We Put a Man on the Moon?

#57

Post by Doxin »

jpatokal wrote: post #54
Al-Khwarizmi wrote: post #50

This seems to happen to a lot of things. In my city (random Spanish mid-sized city, around 250K population) there is often debate about building a light rail or tram public transport line. But it is always dismissed by the administration for being too expensive, pharaonic, disproportionate for a city of this size, etc. Doing some research on the history of the city, I discovered that not only there were several tram…

Classic trams and modern light rail are different beasts. Trams were popular worldwide back in the days where automobiles were far too expensive for most people and buses hadn't taken off yet, and since they were the only practical means of transport for medium distances, even small cities had massive ridership. They also ran right on the road, sharing space with cars, which was OK because there were a lot less cars…

> They also ran right on the road

Sidenote: so do many modern tram systems.

Re: If We Can Put a Man on the Moon, Why Can’t We Put a Man on the Moon?

#58

Post by Al-Khwarizmi »

jpatokal wrote: post #54
Al-Khwarizmi wrote: post #50

This seems to happen to a lot of things. In my city (random Spanish mid-sized city, around 250K population) there is often debate about building a light rail or tram public transport line. But it is always dismissed by the administration for being too expensive, pharaonic, disproportionate for a city of this size, etc. Doing some research on the history of the city, I discovered that not only there were several tram…

Classic trams and modern light rail are different beasts. Trams were popular worldwide back in the days where automobiles were far too expensive for most people and buses hadn't taken off yet, and since they were the only practical means of transport for medium distances, even small cities had massive ridership. They also ran right on the road, sharing space with cars, which was OK because there were a lot less cars…

Yes, that's a very good summary of what happened.

I'm aware of those factors, but I still think we took a wrong turn. Maybe not in the US due to the population sparsity and sprawl, but in Spain and many other European countries, if we could connect every town or city of more than 10K people by either rail, light rail or tram (instead of having spent billions on highways), that would cover 80% of the population. A large majority wouldn't need a car, and could instead use Uber-like services for the last mile. Pollution and emissions would be much less of a problem, and quality of life in cities much better.

But that's what happens with gradient descent, it can lead you to a local minimum...

Re: If We Can Put a Man on the Moon, Why Can’t We Put a Man on the Moon?

#59

Post by kalleboo »

Al-Khwarizmi wrote: post #50

This seems to happen to a lot of things. In my city (random Spanish mid-sized city, around 250K population) there is often debate about building a light rail or tram public transport line. But it is always dismissed by the administration for being too expensive, pharaonic, disproportionate for a city of this size, etc. Doing some research on the history of the city, I discovered that not only there were several tram…

I lived in a Swedish city of a similar size. They had a tram network that was dismantled bit by bit until it was completely shut down in 1973 because it was seen as unmodern. And now 40 years later they're all talking about building trams again since they're so modern...

Re: If We Can Put a Man on the Moon, Why Can’t We Put a Man on the Moon?

#60

Post by jpatokal »

Doxin wrote: post #57
jpatokal wrote: post #54

Earlier quoted context omitted.

Classic trams and modern light rail are different beasts. Trams were popular worldwide back in the days where automobiles were far too expensive for most people and buses hadn't taken off yet, and since they were the only practical means of transport for medium distances, even small cities had massive ridership. They also ran right on the road, sharing space with cars, which was OK because there were a lot less cars…

> They also ran right on the road Sidenote: so do many modern tram systems.

Sure, but sharing right of way with cars is slow, dangerous and generally avoided whenever feasible.
Post reply on HN