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Comment by martythemaniak | Hacker News Reader

I read a good analysis of Artemis a while back that essentially calculated the cost per hour of time-on-moon and in that sense it was easy to see that the program was a significant upgrade over Apollo and the costs weren't that bad when calculated per hour. Achieving a 10x improvement over the previous generation usually can't be done without doing something new and different that hasn't been done before, and in-orbit refuelling fits right in. Gemini and Apollo had to work out and develop far more tech to do what they needed to do.

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How does this work out? Instead of one rocket they will have to launch a dozen or so rockets for one visit to the moon. Why did they choose this option to begin with? And is cost per time on moon not a bit misleading, just stay longer and this cost goes down? You obviously have to bring more food and air and so on, but is that really a significant amount? Or are there other limiting factors that prevent you from staying say a month?

> Why did they choose this option to begin with

Because this will be the first time in history that the cost of a launch will be mostly the cost of the fuel. This is the first fully reusable rocket in history. If you had to throw away a dozen tankers it wouldn’t make any sense.

Also being able to bring 100 tonnes to the surface of the moon is a fantastic reason as well. Everyone can bring a set of golf clubs and balls. Heck we can setup a little driving range with the extra mass allowance.

Notably, we don't need to bring 100 tonnes to the surface of the moon. Or golf clubs. Stable hypergolic fuel would be useful, but there are no plans for that.

NASA has stated they want to maintain a long term presence on the moon. If we take them at their word then we absolutely do need to be able to bring 100 tons to the surface of the moon.

Water, food, air, parts, habitats, ..etc. All of that adds up. Super Heavy lift capability and refueling will be vital to making those plans feasible.

How many flights do they want to get out of each rocket? For Falcon 9 the current record seems to be 18 which would be about one moon mission. They will have to go far beyond that, otherwise it would essentially be an expendable system - one rocket, one mission, just with a couple of launches each costing time and money and probably increasing the risk. Then again, if one does the accounting in terms of mass delivered to the moon, it would probably look more favorable even if they could only get one mission out of each rocket.

It's a crazy sounding goal, but I've heard the idea thrown around that they want them to be closer to airliners in terms of numbers of flights.

I have no idea if that's just Elon spouting nonsense or if it's realistic, but that seems to be the goal.

It’s not just the goal it’s the whole point. I’m not saying it will be achieved but that is the reason it exists and every promised capability is predicated on full reusability.

Not just a dozen. Current estimates say closer to 20.

It makes the notion of ss cans supporting Mars colonization a bad joke. The cans might be just barely adequate to support a Lunar outpost. The "gateway" concept is another bad joke. It is in plans solely because that is the closest to the moon that SLS can get to. It isn't legitimately a gateway to anything: stopping there makes getting where you really want to go substantially harder. The only legitimate place for a gateway would be in high Earth orbit, because it wouldn't require extra fuel to stop at it and then get moving again.

Mars landing is actually less energy intensive the moon landing.

SpaceX is already launching 100 times a year. Starship is supposed to have even faster turn around, launching multiple 100 times per year doesn't seem crazy, specially as current launches require complex iteration, unlike pure fuel launches. Its likely closer to 16 then 20. And optimizing the process and efficiency it will be less then that.

You end up landing around 100 tons. So you can potentially do 1000+ tons a year, and that is before you even go to having many ocean launch pads.

Ok not enough for colonization, but its a damn good start.

Not even enough for a Mars outpost, never mind colonization. The story about ferrying 100 people to Mars in a can is 100% lying; they might fit a dozen. And there is literally nothing on Mars worth refining and exporting home, not even the engines on the cans that got them there; so those would pile up.

The "Mars colonization" story is purely to pump up stock price, just like the "full self driving" that was supposed to enable you to farm out your car during the day for taxi service. Musk hyped that one hard.

> Not even enough for a Mars outpost

Landing a single Starship on Mars literally is already an output if we want to be exact about it.

The idea that the Starship architecture isn't enough to have a small base on Mars is just nonsense.

> The story about ferrying 100 people to Mars in a can is 100% lying; they might fit a dozen.

As with everything 100 was an inspirational goal, once you have good infrastructure on both sides and everything optimized for mass transport. And yes you might be right, 100 is to optimistic. He didn't sign any contracts based on those numbers, he promised nobody that number. Its literally an inspirational goal with a low chance of success.

> they might fit a dozen

Damn, a dozen is amazing.

> And there is literally nothing on Mars worth refining and exporting home

Nobody claimed their was ... but you are really good a fighting straw man.

> "Mars colonization" story is purely to pump up stock price

That just proves that you don't have the first clue what you are talking about. Musk literally admits that Mars colonization isn't gone make money. The reason they want Starlink is because they think that can actually make money and support large rockets so they can use it for Mars. Musk things he will spend his private money on Mars colonization. Pushing Mars is literally the opposite of stock price pumping.

"Inspirational goal" is a lot of syllables for "lie". Make no mistake, nobody who understands ever thought they could take 100 people in there without freezing them. Musk said it because he thought it sounded good, fully aware it is impossible.

He also knows there can be no colony. So, every falsehood promoting it is a lie.

Re-usability was once a 'lie' Starlink was also 'lie'. Their high launch rate was also consider a 'lie'.

100 people would mean about 10m3 per person. That sounds like more then some prisoners have had in isolation cells. Of course wouldn't be comfortable necessary, and in practice you likely wouldn't do that way.

Of course this talks about a situation where there is lots of infrastructure on both sides. No need to bring extra food or equipment. A pure crew ship. Near perfect system of water reuse and so on.It also presupposes some understanding of solar radiation or much better cancer treatment.

In addition you can think of a number of ways to expand volume.You can potentially stretch the ship, or widen the ship. You could have inflatable hubs to temporary create extra volume. The earlier version of the ship when that 100 number was first talked about was also much bigger then the current one, the ship designed has changed because they realized lower cost per stack and higher re-usability made more sense. Maybe it would require medically induce sleep (bear style).

100 is of course inspirational and might be off by a factor of 2-4x but to act like this statements are some unforgivable lie is ridiculous. Specially because there is are no contracts signed or promises made, its literally just 'this is our long term goal'. Complaining because a ship can 'only' transport 12 people to FUCKING MARS is just insane to me.

And in the end the cost per person is what actually matters, and that is what they are trying to reduce systematically. If you actually listen to Elon that's what he talks about most and what has always been the main driving goal. He talks far more about that in the interviews about this, the actual number he threw out are just estimation, and he makes that very clear. He even makes it clear that they don't know how to get there yet, they literally just working towards it as best as they can. 100 per ship is just one of many estimated numbers. A million people to self sufficiency. 1000 ships operational. Many others. All those numbers might be very wrong and Elon would admit as much. Its not the 'gatcha' you think it is.

And notice how you didn't defend your ridiculous 'pump-and-dump' nonsense.

Liars typically lie for reasons. Some are just pathological, but Musk has visible reasons. He lies a lot, so is seeing which stick and repeating those.

Nobody mentioned "dumping". Please do not make things up.

What's also fascinating is that they are going with, in VERY BROAD strokes, the concept that was Von Braun's preferred method to achieve this back in the day too, but it was abandoned in favor of the lunar orbit rendesvouz.

For a critique of the current method, I found the SmarterEveryDay lecture on it gave some good food for thought!

What were Von Braun's reasons for something akin to a Near Rectilinear Halo Orbit? Links anyone?

The SmarterEverDay concerns about the orbit seemed to be that while landing or taking off maneuvers were short & low energy (good), it meant the opportunity only came about every couple days (bad).

SED also stressed that Artemis is relying on crulyonic fuel transfer. SED repeatedly pointed out this is a tech that has never been tested, ever.

6 days (worse).

I watched the SmarterEveryDay lecture last night, so I was primed for this story. He mentioned fuel transfer being a huge unknown.

https://www.youtube.com/watch?v=OoJsPvmFixU

The other thing he mentioned was the Apollo success playbook (SP-287), "What Made Apollo a Success?"

https://ntrs.nasa.gov/api/citations/19720005243/downloads/19...

Link to EPUB version https://old.reddit.com/r/SmarterEveryDay/comments/18aw4ca/i_...

The more I've thought about that lecture the less I really agree with most of the things he raised, for the simple reason that Apollo is never, ever going to happen again. It's a lot of argument from increduality (e.g. it's easy to pretend starship launch's are "too many", without addressing that practical reusability has been a thing for years right now).

At it's peak, the Apollo project was funded to the tune of 1.1% total US federal outlays during the time period it ran. That's an enormous amount of money, which failed to produce a remotely sustainable result. You got what you got: moon landings done quick, and then never again.

The modern Apollo project is SLS which...is a big, expensive, absolutely cannot fail rocket (which is really a jobs program for preferred contractor districts, with technology choices decided by politicians not engineers).

Basically the SED lecture spends a lot of time gesturing at Apollo, but never addresses the actual problem which is NASA is funded the way it's funded: of course they know they're going to miss their launch dates, they're not funded to hit them, and they're probably going to wind up redesigning the mission once Starship is flying to orbit and actual performance numbers are realized off-paper. The SLS is the SLS for the same reason: at the time the program started there was no SpaceX, nor Space Shuttle and it was something of a national embarrassment the US didn't have a manned space capability but the Russians still did.

In short, for a lecture which opens talking about people worrying about disagreeing with their superiors, he stays well away from the actual live-wires of the issues.

> Achieving a 10x improvement over the previous generation usually can't be done without doing something new

It is definitely possible if the fixed cost(e.g. R and D, manufacturing capability, testing infrastructure etc) is majority of the cost and scaling up doesn't increase them linearly. Cost of raw materials like fuel or building material would be negligible for Apollo or SLS in comparison.

Its hard to calculate because non of the costs are really all that clear. There are not even lander contracts for any mission after Artemis 3. It also depends on how long into to future you think this continue.

And I think what that kind of analysis misses is how many important multi-use technologies are developed. Starship will mostly not be used for moon, but financed with moon money.

The problem with EVA on the moon is the reliability and endurance of the space suits. Even if HLS delivers, there could be delays simply because there are no suits. When you consider the near rectilinear orbit having a seven day period, then bad suits are a deal breaker for the entire mission.

Conversely if you have reliable payload to the lunar surface, delivering special-use lunar escape vehicles to keep on standby is a better option then having the entire mission pay an ongoing cost for what should be an exceptional and unlikely scenario.

The problem of "we need to get off the moon now" is "okay, but where are you going and what's going to be there that's more useful then where you are?"

It's not unreasonable to note that a medical emergency would be much better dealt with on the moon - where you have gravity - then in orbit, where you don't. Whereas if you need to bail out and get to Earth fast (which you can't) then you'd be better off just dropping a vehicle which can do that onto the surface.

Yeah Apollo was obviously incredibly impressive but was sort of a technological dead-end. There was no path from that program to a permanent human presence on the moon.

If they can really get Starship and orbital refueling working, it's a step function forward.

I tend to disagree. There was very much a evolutionary path forward.

There were already programs like NERVA in development for an advanced nuclear upper stage. Once you have that, making the Upper Stage refuel-able, makes it basically into a multi-use space tug for cis-lunar.

Then you could evolve Saturn 1B into a reusable Saturn 1C, just like Falcon 9. That gives you a reusable heavy lifter. And it would also safe a gigantic amount of money that was spend on Atlas/Titan/Delta in the next 40 years.

The Apollo capsule was not reusable but continuously evolving a capsule design in that direct was certainty possible. But its not the most important part of the system in terms of cost.

What really need more development is the lander itself. Making a large reusable lander would have been costly but not really out of reach.

You can use an occasional Saturn V for large things like Skylab and special deep space mission.

That was a much better path forward then Space Shuttle and ISS.

> a technological dead-end.

"The Apollo lunar base proposal saw an uncrewed Saturn V used to land a shelter based on the Apollo Command/Service Module (CSM) on the Moon." <https://en.wikipedia.org/wiki/Apollo_Applications_Program#AE...>

I feel this somewhat glosses over the unsolved challenge of how to land a Saturn V rocket.

Much easier to do on the moon than on Earth though at least, right? No atmosphere, fraction of the gravity.

Yeah but there's still no precedent at all for re-ignition, stabilization, automatic landing, etc. It took SpaceX like 20 tries to do this using 2010's technology and computer automation, with a much smaller rocket.

No? Grid fins don’t work in a vacuum. Lower gravity means your engines need a wider throttle range, which was already challenging at Earth gravity.

No! Not at all! The Moon is harder to land on then Mars!

Aerodynamic drag is amazing. It means fins and parachutes work. It means you can slow yourself down without propellant and with passive systems.

Mars actually kind of sucks too because it has just enough atmosphere to interfere with rocket engine ignition but not enough to be able to land on chutes alone. But any amount of parachute and aerobraking is better then none.

But the Moon is terrible: no atmosphere, so you're under engine power the whole way down. The propellant and mass demands are thus much higher.

Thanks, good explanation. My thought on "no atmosphere" is that it eliminates the need for heat shielding to enter it, but I can see how that's not really an issue compared to all the benefits.

What would be being landed would be a CSM-based shelter, not the whole Saturn V.

Nobody proposed landing a Saturn V. The Apollo lunar base proposal called for a shelter based on the existing Lunar Module[1], along with an extended CSM and LM Taxi hardware derived from the basic Apollo program.

1. http://www.astronautix.com/a/apollolmshelter.html

OK, and then what? You can land the tiny capsule that you took back and forth to the moon and call it a permanent shelter, sure, but you're not going to be able to build any kind of substantial base at a rate of one giant rocket per tiny capsule.

http://www.astronautix.com/l/lesalunarbase.html

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