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

The Lunacy of Artemis

idlewords.com

Post reply on HN
Print view View original

321–330 of 539 posts

Re: The Lunacy of Artemis

#321

Post by gus_massa »

idlewords wrote: post #91
SJC_Hacker wrote: post #84

Loss of crew tolerance is not what it used to be. The Apollo astronauts were given about a 10% chance of not coming back. In Apollo 13 they very narrowly avoided. Which was considered acceptable for the time period. I'd argue that mission failure tolerance is also considerably lower, in todays political environment. Again, Armstrong said their chances of actually landing were maybe 50/50. So if they get there and hav…

According to NASA's own advisory panel, the chance of losing the crew on just the SLS/Orion portion of the mission (so not including the landing, Gateway, or the trip to and from the lunar surface) is 1 in 75. If you make the reasonable assumption that the landing is at least as risky as the trip over, you get a 1 in 30 chance the crew dies. The Shuttle towards the end of its life had an estimated chance of loss of c…

IIRC from the Feynman apendix, Nasa claimed in the official reports that the SLS had 1/10.000 or 1/1.000.000 chance of failures, but the real numeber was close to 1/100.

If they now claim 1/75 in the official reports, I'm very worried.

Re: The Lunacy of Artemis

#322

Post by usrbinbash »

pfdietz wrote: post #318
usrbinbash wrote: post #315

Earlier quoted context omitted.

> The cost of developing space robots doesn't decline nearly as much. Developing Costs wouldn't, but deployment costs would. If launching becomes cheaper, then, sure, I could launch more space toilets and freeze-dried groceries. Or I could use that capacity to launch more and bigger robots, more often and further. Guess which of these two has a better ROI given the many many many limitations humans have once they lea…

> It doesn't matter how cheap a launch becomes. I have to support an astronaut with food. So, if it were to be as cheap to go into space as to go to St. Louis, sending a person would make no sense because of... food? This makes no sense. Obviously there is some breakpoint at which it would make sense. You can't just handwave and say that universally without doing arithmetic.

> So, if it were to be as cheap to go into space as to go to St. Louis

Obviously there is a breakpoint at which the cost differential would no longer matter, I agree.

It's just as obvious however, that this breakpoint won't be reached in the near future, or even the forseeable future.

It would require a radically new propulsion technology, which, and this is the sad truth, we don't have. The way we launch rockets today has remained pretty much the same for more than half a century: By burning chemicals in a tube.

As long as that doesn't change, I can pretty much guarantee that the cost differential between doing space-exploration using humans, and doing it with robotic probes, will not look good for good 'ol humans any time soon.

Re: The Lunacy of Artemis

#323

Post by PaulHoule »

kqr wrote: post #296
PaulHoule wrote: post #265

It's easy to miss how clever the Apollo mission architecture was. The moon is not so far away in terms of distance but it is very far away in terms of Δv because, not least, you have to land propulsively because there is no atmosphere to slow you down. Trips to some near-Earth asteroids are easier than the lunar surface, Mars and Venus aren't that much harder because in any of those cases the Moon's gravity can be he…

> The moon is not so far away in terms of distance but it is very far away in terms of Δv because, not least, you have to land propulsively because there is no atmosphere to slow you down. Not least, but certainly the requirement to brake before you land must be on the small order compared to achieving escape velocity from the much bigger rock I'm on?

You gotta get off Earth no matter where you go in space. It's almost free to come home from LEO, you get a huge amount of free velocity change returning from the moon. (At the cost of rejecting the heat)

In the rocket equation

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

the required mass ratio is an exponential function of the velocity change so adding another 2.5 km/sec for this and another 2.5 km/sec for that you are making the mission much more difficult.

It's bad enough that it takes two stages to get to LEO comfortably but going beyond that adds cost and complexity pretty quick, for instance the large number of Starship launches required to get a Moon mission into the right orbit.

I like to think about what interstellar travellers would do if they wanted to land on the Earth on the assumption that they are accustomed to life in deep space and have spent 1,000 to 10,000 years "living off the land" off comets and rouge planets and are used to a lifestyle like cutting up a planet like Pluto and building a number of small ringworlds powered by D-D fusion.

I'd conjecture that despite having advanced technology they would still find the "reverse space shuttle" problem where you land with a full load of fuel and then take off from the ground to be difficult. It's not like they are going to haul a space shuttle along with them and would probably find it non-trivial to 3-d print one from plans that old. My take is that it would probably take them a decade to figure it out and that they might well come up with an alternative answer like

https://en.wikipedia.org/wiki/Skyhook_(structure)

which depends on in-space infrastructure that they'd be experience with although it could work together with an air-breathing aircraft which would be something new for them.

Re: The Lunacy of Artemis

#324

Post by PaulHoule »

sidewndr46 wrote: post #271
PaulHoule wrote: post #265

It's easy to miss how clever the Apollo mission architecture was. The moon is not so far away in terms of distance but it is very far away in terms of Δv because, not least, you have to land propulsively because there is no atmosphere to slow you down. Trips to some near-Earth asteroids are easier than the lunar surface, Mars and Venus aren't that much harder because in any of those cases the Moon's gravity can be he…

When you say "Moon's gravity can be helpful." do you mean some sort of slingshot around the moon to get to a trajectory that is closer to a Mars orbital insertion?

Yes, but the right way to think about it is

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

and Luna is just the first stop on the way from Earth. That Wikipedia article doesn't explain the concept as well as I'd like but the papers it references do.

Re: The Lunacy of Artemis

#325

Post by [deleted] »

kqr wrote: post #180

I didn't live through the early space programmes, but having read about them recently, I'm surprised by how incremental they (and the Soviet Sputnik and Vostok counterparts) were. - The early Mercury flights developed the idea of putting a human in a capsule on top of an ICBM to see what happens at altitude and during re-entry. - Later Mercury flights experimented with de-orbiting techniques. (The early flights didn'…

[deleted]

Re: The Lunacy of Artemis

#326

Post by hersko »

usrbinbash wrote: post #279
jwells89 wrote: post #273

Earlier quoted context omitted.

Long-term habitation of surfaces of bodies other than that of Earth is a stepping stone to being able to live in space long term in very large, permanently spaceborne crafts. It’s easier to develop these things on the moon, mars, etc because of immediate access to materials that’d need to be launched into orbit otherwise. In the long term, it may make sense to build shipyards on the moon, on Mars, or somewhere in the…

> a stepping stone to being able to live in space long term in very large, permanently spaceborne crafts. That is not going to happen, without technology that currently only exists in Science Fiction, like artificial gravity, for the simple reason that we require 1g to live, let alone thrive. > because of immediate access to materials that’d need to be launched into orbit otherwise. 1. How does this "immediate access…

> That is not going to happen, without technology that currently only exists in Science Fiction, like artificial gravity, for the simple reason that we require 1g to live, let alone thrive.

Artificial gravity is easily generated via rotation or thrust.

> 1. How does this "immediate access" benefit the aforementioned "very large, permanently spaceborne crafts", which apparently won't be moored to planetary bodies?

It will be far easier to get materials into space from the moon than from the much deeper gravity well of earth.

> I agree. But given that, what evidence supports the idea that the branch that eventually allows us to leave our solar system requires us to first waste tons of resources on trying to send people to inhospitable, irradiated rocks for no good reason?

How do you see us developing the technology for humans to leave the solar system if we never develop the technology to visit the moon?

Technology is generally driven forward by increments, and having smaller goals leading to the larger one is pretty normal. Also, you don't need to "cheat physics" to explore space.

Re: The Lunacy of Artemis

#327

Post by avmich »

dotnet00 wrote: post #141
avmich wrote: post #122

Earlier quoted context omitted.

I'm strongly disagreeing with some qualifications there, to the point it's hard to find where to start. E.g. what this passage mean - "...this single-use lander carries less payload (both up and down) than the tiny Lunar Module on Apollo 17." ? Can't Starship HLS lift more than 50 kg of rocks from the Moon?.. I'm intentionally simplifying the question.

Starship HLS can lift much more than 50kg, but since Congress/NASA requires Orion to be the return vehicle, the amount they can return is limited by that, which only has a 100kg payload return capacity (and presumably a chunk of that is going to be taken up by food, spacesuits etc). Same with why each stay is going to have to be just ~1 week. Starship can obviously carry more than enough stuff for 2 people to live of…

But that's not the lander's problem.

I do agree NASA's Artemis program is strange. However it's enmeshed with Starship, and that's sufficiently different story.

Re: The Lunacy of Artemis

#328

Post by jcranmer »

usrbinbash wrote: post #272
thisaccount546 wrote: post #261

Earlier quoted context omitted.

The weird thing about NASA's budget when you look at it[1] is that funding allocation appears to be inversely proportional to the benefit. Human spaceflight is the largest chunk, at 44.9% of the budget. Aeronautics and technology are at the bottom, with technology being allocated 4.9% of the budget, and aeronautics 3.5%. There were good reasons why people were interested in sending people into space in the early days…

> There were good reasons why people were interested in sending people into space in the early days of space exploration. Before automated systems were sufficiently developed, manned programs looked like the best choice. But once automated systems became sufficiently advanced, it was clear that they were the way to go. This, and it never ceases to baffle me that there are people who still believe that there is some s…

There is one benefit to human spaceflight over robotic spaceflight: the human body is a much more adapted tool to unknown situations than robots are. A human hand is a better manipulator than any robotic tool (look up videos of robots trying to turn a doorknob and open a door, e.g.), and our locomotion tends to be well-adapted to adverse terrain.

But it is far from clear that such versatility is worth all of the costs of human spaceflight, principally the fact that humans are fragile bags of water that require fine-tuned environmental conditions to operate (and such conditions are difficult to provide in space).

Re: The Lunacy of Artemis

#329

Post by ryandrake »

kqr wrote: post #296
PaulHoule wrote: post #265

It's easy to miss how clever the Apollo mission architecture was. The moon is not so far away in terms of distance but it is very far away in terms of Δv because, not least, you have to land propulsively because there is no atmosphere to slow you down. Trips to some near-Earth asteroids are easier than the lunar surface, Mars and Venus aren't that much harder because in any of those cases the Moon's gravity can be he…

> The moon is not so far away in terms of distance but it is very far away in terms of Δv because, not least, you have to land propulsively because there is no atmosphere to slow you down. Not least, but certainly the requirement to brake before you land must be on the small order compared to achieving escape velocity from the much bigger rock I'm on?

Everything is on the small order of magnitude when compared with getting into Earth orbit. As the quote goes, "Once you get to earth orbit, you're halfway to anywhere in the solar system."

Re: The Lunacy of Artemis

#330

Post by cratermoon »

smallmancontrov wrote: post #309
GMoromisato wrote: post #282

Earlier quoted context omitted.

This is an excellent narrative, but I think it omits the many risks the program took to get to the moon before the Soviets. For example, Apollo 8 was the first time a Saturn V (and command module) was sent all the way to the moon, and it was done with a crew. Because there was no lander, there was no backup in case the command module had a problem. If the explosion on Apollo 13 had happened on Apollo 8, the crew woul…

Yeah, the risk appetite was much higher. Those are good reminders on Apollo 1/6/8, but the problems didn't stop there. The first 5 landing missions all had huge problems that nearly killed everyone, too. Only the last 2 landings were sort of OK. Apollo 1: burned all astronauts alive ... Apollo 10: POGO oscillations on launch (Saturn V still trying to tear itself apart), LEM tumbling Apollo 11: Computer kept crashing…

Counterpoint: all of those incidents, except Apollo 1 are proof that the engineering was great, because nobody died.

For example, you mention the computer on the Apollo 11 lunar module crashing. In fact, it was recovering and working properly. The astronauts had left the rendezvous radar on during descent, in case it was needed for abort. That was not a nominal configuration, and the radar kept stealing cycles and causing the guidance computer to be overloaded with tasks. Remember, it was a hard real time system. What did the computer do? Reset and prioritize the key task: landing.

Apollo 12: Got hit (twice) by lightning. The electrical system wasn't fried, it survived it, in a protective mode. Importantly, the computers in the Instrument Unit, placed on the third stage, were completely unaffected.

Apollo 15: One lost parachute, still landed safely (if a bit hard) because of redundancy.

I could go on, but you get the point. It was a well-engineered system backed by a team of engineers.

Post reply on HN