Starship lunar lander missions to require nearly 20 launches, NASA says | Hacker News Reader

Starship lunar lander missions to require nearly 20 launches, NASA says

spacenews.com

26 pointsironyman60 comments

20 launches of reusable vehicles. At an estimated $40 Million per launch, 20 launches is still way cheaper than a single launch of an expendable moon rocket (Saturn V ~ $1.3 Billion per launch, Artemis ~ $ 4.1 Billion per launch).

> In order to be able to meet the schedule that is required, as well as managing boiloff and so forth of the fuel, there’s going to need to be a rapid succession of launches of fuel

20 launches in rapid succession

Fantasy rockets are always cheap! Let's wait until they fly one.

But there's a separate issue too; let's say generously each launch has a 98% success rate, that alone means a 1/3 chance the mission will fail. So you need to start adding backup missions to the plan, exacerbating the problem.

The trouble here is not just launch cost but also launch cadence. How do you launch 20 huge rockets in short succession when one heavy launch per month is about the best that's been done to date?

You need one backup launch window (so 21 instead of 20) and a backup rocket; these seem like no problem. I think launch cadence can also be solved with proper incentives.

If launch #8 blows up your launch tower, you do in fact have a launch cadence problem.

For the naive math to work, you need to build 21 launch pads, etc.

If the optimistic guess is $40M, wouldn't things have to go really, really, really wrong for it to be anywhere near the $1.3 Billion? I mean, those numbers aren't exactly close at all. Even if it's naively optimistic, it still seems unquestionable that it'll be a lot cheaper, no? Am I missing something?

That's 20 launches for 1 lunar mission. Vs 1 Artemis launch per lunar mission. Comparable to 800 million for 1 lunar mission for SpaceX.

So, 4.1 / .8 ... Starship would need to be 5.125 times the cost estimated to cost as much as Artemis. As others pointed out, it relies on un-tested in-orbit refueling and 20 times the opportunity for launch failure. I wouldn't be surprised if it's 5x off.

I don't know what SpaceX's overrun record is so far, but I'm sure it's way less than 5x.

Edit: It did take 20 tries[0] to get from the first launch of Falcon 9 to vertical landing (after a detour through parachuting systems).

40 million seems like a post-development estimate.

[0] https://en.m.wikipedia.org/wiki/Falcon_9_flight_20

Apples and oranges. Starship delivers far more to the Moon surface in one flight, which is handy if somebody wants to actually stay on the Moon for prolonged activity. And on a per-kilogram on the Moon surface comparison Starship is quite competitive.

There is a backup launch pad. Presumably if you blow up two launch pads you will probably decide to scrub the rest of the launches until you've solved the issue.

It's the most fantasy rocket, except for all the others.

Not a fan of this whole plan, but the Starship program is much further along than any other. BO has never orbited anything, and the Senate Launch System is planning around a year between launches, at best, at $1b per. Meanwhile F9 is up to ~273 orbital launches at far better than 98% success. Starship already proved the flip and land. OFT1 surpassed its first test goals (clear the pad). I don't think it's unreasonable to extrapolate for now.

lol if it actually ends up even being 1b per launch XD

The 20 launches includes backup missions. The actual number of launches they need is in the teens.

Spacex has averaged a launch every 4 days this year. That heavy launches are infrequent is due to the limited demand. To meet this cadence, they'ed need to average one launch per launch pad every 12 days. If they fail to meet that cadence, it just means a little more propellant boils off, which can still be topped off with one of the backup launches.

I would not describe something currently going through flight tests as a fantasy rocket. At the time of this comment it has made it into space (even if just barely). Sure it's not ready to go yet, but it's not just an idea on paper either.

2021 Blue Origin on SpaceX's Artemis III plan doesn't seem far off:

https://www.reddit.com/media?url=https%3A%2F%2Fexternal-prev...

According to Wikipedia: https://en.wikipedia.org/wiki/SpaceX_Starship_(spacecraft)

    Launch mass: 1320 tons (120 tons dry)
    Payload capacity: 100 - 150t (fully reusable)[1] 250 - 300t (expendable)[2]

So, to fully fuel up a Starship on LEO 1200 tons of fuel are needed, which are between 8 and 12 full payloads of said Starship.

Yes there could be some boil-off.

Refueling station could be protected both by Sun screens (a-la JWST if you wish) and include active coolers. This is an old topic in space technology, e.g. both Buran (30 days of orbital flight while keeping LOX liquid onboard) and Vulcan's second stage (LH2 onboard) focused to an extent on that.

We do have a long history of refueling - since at least station Mir the visiting Progresses used to refuel the station, only the liquids were different, and of course the amounts were very different. Still this increases hopes that we can develop the refueling technology since we'll soon need more of it.

Those multiple launches don't necessarily spell doom to the lunar plans for Starship. For example, Falcon-9 is reliable enough to have a hundred consecutive successful flights. And even in 1960-s the idea to have multiple launch pads to be able to launch even after catastrophic event on one of them wasn't too radical. And majority of activity of this kind is probably going to be unmanned, which makes things faster and cheaper to repeat if something goes wrong.

No one seems to mention that this whole architecture requires a specific technology, in-orbit refueling, that does not exist.

It would be cool to have it! But it's one of those technical problems that grows in difficulty and complexity the more you look at it in detail. It is very hard to move tons of propellant around in zero-G (or fractional G) and the learning curve for it has to be done in space. Multiply the difficulty by a factor of 10 or so if the propellant is also a cryogen.

I'm curious why a crygenic fuel is harder to transfer in space than something like kerosene? Space is cold, so my naive idea is that a crygenic fuel is easier to keep liquid (non-frozen).

Space isn't "cold", it's a thermal insulator. Objects in space are still illuminated by sunlight whenever they're not in shadow, which heats them up, and the vacuum makes it difficult for them to get rid of that heat.

That's why (for instance) the JWST has a sunshade that is considerably larger than the telescope itself, just to keep it cooled to 50K -- which is still well above the boiling point of liquid hydrogen. It's also why the ISS has large radiators so that it doesn't get too hot for human habitation.

A large sun shade for an object in low earth orbit shouldn't be that much of a problem. Transferring a liquid in microgravity should be equally difficult regardless if it's cryogenic or not.

That sunshade will turn into a big sail in LEO, annoyingly.

The issues are: a) boil-off (others have addressed that elsewhere in this these threads), and b) transfer in zero G (something close to an inertial frame of reference). (b) is hard because bubbles of gas form randomly as you drain one tank, so the pump can't work very well. Bubbles of gas are not a problem for rockets normally because they either are always under acceleration (so the gas floats to the top of the tank, while the outputs are at the bottom) or because they have small and full tanks that SpaceX calls "header tanks" to make engine start possible which then resolves the gas bubbles problem in the larger non-full tanks.

It's possible to avoid creation of the bubbles in the first place though. Some tanks could use pistons, and some - flexible membranes between displacing gas and the liquid fuel. Or tanks could be flexible themselves, squeezing the fuel out when their volume decreases and when being fueled, increasing their volume.

If bubbles appear, it's possible to liquify them back. Increase of pressure with possible decrease in temperature (active cooling) could help.

This is an old problem, with quite a few ideas how to solve, some of those ideas even tried in practice.

Retrofitting such things into Starship sounds difficult.

The environment in low earth orbit isn't cold, beyond the obvious direct sunlight the earth is warm and fills a lot of the sky. Shielding stuff from it is a challenge. Even near Mars orbit isn't cold enough to store liquid methane, let alone liquid hydrogen.

No one knows how to do fuel transfer in zero g, but there must be ways. Here's one: lash the orbiters and make them spin as a centrifuge and, of course, drain from the donor where the fuel piles up.

The problem is not a lack of ideas, it's in the engineering details of how to do it. "Lash together spacecraft" and "spin x as a centrifuge" are also hard technical problems.

What makes this particularly difficult is it can't really be tested and prototyped on Earth, you have to make all your mistakes the expensive way.

It doesn't have to be that expensive. They could start with a small scale demonstrator that could fly on Falcon 9 just to explore feasibility and make the mistakes at less cost. Or once Starship is operational they could fly several different small scale prototypes just to test them in one go, and they could even do this on an early flight that they wouldn't use to launch commercial payloads. Still expensive, because it might need two flights for them to get the confidence they need to go with one design. But not as expensive as "the expensive way".

We already do in orbit refueling for the ISS. Those are different propellants and smaller volumes, but we know how to pump liquids in zero-G. Cryogenics are no harder to pump, the only difficulty is storage.

How did the folks in the 60s do this? Starship is going to be vastly more capable, but it's not finished, and it's vastly more complex.

Money, brains, and a perceived existential threat from the Soviet Union.

I was a toddler when the Soviet Union dissolved, do you think the public/cultural perception of China, of Russia, or of middle-eastern terrorists that we have today is of a similar character to the Soviet bogeyman?

Also, I don't think that brains have changed that much in the past 60 years. Many of our best and brightest are now in fintech or adtech instead of manufacturing and research groups, but I wouldn't say that better brains were why the Saturn program succeeded when Starship seems to be as much of a challenge today (rather, I'd say the goalposts in economics, risk, and capacity have shifted).

> public/cultural perception of China, of Russia, or of middle-eastern terrorists that we have today is of a similar character to the Soviet bogeyman?

I don't think so, i was a kid but remember breaking news on TV of Russian strategic bombers enroute to the US only to turn away at the last second. It was day by day whether society ended or not during the cold war.

China is where my iPhone is made (and everything else). Middle East is where my oil comes from. Russia is in a stalemate with a former satellite country whose main export is grain.

They don't make a good antagonist.

Could be surprising, but some kids of the day in the Soviet Union were more fearful (well... wrong word...) of Chinese nukes rather than American ones.

Lots of money, only landing two people in a foil can with very little additional payload capacity, and not staying very long.

Apollo cost something like $300 billion in 2023 dollars.

NASA's contract for the Starship landing is $2.9b. SLS development has been around $12b with a marginal cost of $4b per launch.

All together the Artemis program (SLS, Orion, Lunar Gateway Space Station, and Landers) is estimated to cost around $93b through 2025.

The Apollo LEM had a payload capacity in the neighborhood of 1T. The Starship Lunar Lander is supposed to handle 100T+

More middlemen these days, all looking for their handouts.

More middlemen?

(pdf warning) https://media.defense.gov/2022/Feb/15/2002939087/-1/-1/1/STA...

> Since the 1990s, the defense sector has consolidated substantially, transitioning from 51 to 5 aerospace and defense prime contractors.

Also- if an entity is performing work under contract and gets paid for it how is that a handout?

I'm not necessarily agreeing with the poster above, but surely the number of prime contractors is not relevant to the number of non-prime sub-contractors?

Artemis is less expensive than Apollo, at least so far.

There is definitely a fighting over handouts component, but this mostly seems to be at the Congressional level where they legislate how the rocket will be built and what kind of boosters it will have, and those requirements have a habit of lining up nicely with existing defense contractors in the states they represent.

Much more money was spent, and mass to the lunar surface was far smaller than the Starship lander.

Single use 'Hail Mary' style rockets

> How did the folks in the 60s do this?

A huge commitment of resources relative to national output (2.5% of GDP over a decade—that's spending annually about 70% of what the US currently spends on defense), limited mission scope, limited planning for anything to be usable beyond “get to the moon”, and higher risk tolerance.

Also, counting both unmanned tests as part of the program, the 1960s moon program (Gemini + Apollo programs) took more than 20 launches given all that.

The Apollo Lunar Module had 6.7m³ volume. Starship HLS should have around 1000m³.

Apollo LM had about a 5 ton dry mass. Starship LM would be probably well over 200.

Apollo LM got around with a ton of stages. Starship LM gets around with refueling flights.

High risk tolerance in a war-torn era which held military pilot lives cheap, expendable, noble to sacrifice.

(Not commenting which mindset is wiser or foolish-er; just think it worth highlighting, underscoring how starkly different our eras' mindsets are. I think it's worth pondering. Do you even know how many workmen died in the trenches of the Apollo Program industry? I don't have a clue either. That one SpaceX employee died on the job is national news in our time—in the 50's-60's, all blue-collar jobs were orders of magnitude more horrible).

https://en.wikipedia.org/wiki/List_of_spaceflight-related_ac... is a start? Probably doesn't take into account contractor lives offsite or heart attacks offsite, etc.

I've read a couple histories of the Apollo program, and they spared no effort to keep the astronauts safe.

The Apollo 1 fire came close to causing the entire program to be shut down.

That generations safety obsession lost us space for a generation, in the same way their no-nuke fixation lit our only planet on fire.

These are the sins of my parents.

They did it by not trying to land a huge fueled rocket on the Moon (on its tail!) and then have the whole thing take off again. The rocket equation bites you in the ass very quickly once you commit to a 1950's sci-fi style landing with a big silver rocket that you insist on taking home with you.

I don't know what you mean by more'capable' in this context if the system needs 20 times the launches and nonexistent technology (in-orbit refueling) to achieve the same goal.

This is the answer. Apollo missions were essentially 6 stages (3 to orbit then TLI, lunar descent stage, lunar ascent stage, CSM). Maybe 7 if you count dropping the service module for reentry.

The whole concept of starship only works if they can launch reliably a couple times a day

I wonder, is it science that limits our payload sizes or is this just modern bureaucracy that forces so many launches. My money is on bureaucracy.

Blame the rocket equation for this one.

If you are not familiar with this:

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

Yeah, this one is pure physics. It's hard and expensive to get off the planet, and even more so to get to the Moon.

Here's your culprit:

Mtotal = Mempty * e^(deltaV/Vexhaust)

If you work backwards from launching a couple of hundred tons from the moon, you end up needing all these refueling flights. Compare that to the 2.5 ton mass of the Apollo ascent stage. The rocket equation does not play.

man is on drugs comment

I look forward to the time in the future when life is more than about living eg. going to work, paying bills, etc... the greater picture of what is out there and spreading ourselves out, in case we are the first which is hard to believe.

I'm sitting at a work cubicle now typing this, my mind is constrained to the system on Earth.

It is sad to think you're just a cause-effect driven machine eg. if happy/good = continue.

You're pinning a lot of hope on space, and I doubt it's going to work out to you.

You right now exist on a planet with an epic amount of empty space: deserts, oceans, and a ton of 3D volume under the ocean surfaces. You can spread out today, right now. You'll have air available for free, at a pressure and temperature you can tolerate (or easily modify to get there).

Space isn't going to improve your nihilism. It's incredibly hostile to life, and you'll put in all of your effort just keeping from asphyxiation. The rocks out there are different from earth rocks, but I bet you haven't even put much thought into all of the different kinds of rocks you have available to you right now.

I suspect you'll quickly get bored of the fact that non-living planets have a lot less going on than living ones. There will be a chance for people to do them the first time, but the low-hanging fruit will all be picked quickly, and everybody else is just going to be standing about wondering why they wanted so badly to go to a place with nothing interesting happening.

Don't get me wrong: space is cool and I'm glad we're going. But I don't think it's the existential cure-all that you (and many others) seem to imagine that it is. If your actual interest was spreading out, you'd already do it. I believe that your malaise is due to something else entirely, and I think you could take more realistic steps to do something about it.

I bet even if you did nothing everyday on the moon it would feel more productive and have more gravitas just because you’re on the moon; atleast for the first few decades.

> You right now exist on a planet with an epic amount of empty space: deserts, oceans, and a ton of 3D volume under the ocean surfaces.

All already owned and claimed by someone, backed by the force of violence.

I agree with you about space not being solution, but I don't think its as simple as you put it.

Most of the ocean is unclaimed and unclaimable.

Most of the deserts are technically owned by somebody, but you can easily get far away enough that nobody is going to come looking if you don't call attention to yourself.

"Easily" here is defined as "walking for many weeks through deeply unpleasant territory". Which is, of course, very hard, but orders of magnitude easier than space.

None of it's simple, of course, as you note. But space is always far, far, far harder. You could go McCandless yourself right now. Which, of course, means dead, but even McCandless made it there, and a few (miserable) months. Which is months longer than you'd survive in space without vast armies of people helping.

It's more than one place, all humans shouldn't just be on Earth, because if this place was wiped out then we're gone, all that time/knowledge gained wasted.

I wasn't talking about as a solution to over population/pollution or anything. Just eventually when we have the tech eg. warp drive/FTL that would be nice.

The future in space will come about from terraforming the moons and planets.

Unfortunately, NASA is terrified of introducing terran life to any of the bodies it visits. We should be doing the opposite - spreading life everywhere we go.

Reply on news.ycombinator.com