Hacker News Reader

Comment by syntaxing | Hacker News Reader

Aren’t rockets to the moon vs LEO and GEO on completely different levels of requirements?

To send starship to the moon takes 5-10 more starships to refuel it first. Of course, comparing orion to starship is like comparing a dragon to the space shuttle. Starship is enormous and that's why it needs so much fuel lol.

I'm not saying there's room for improvement, but I think people neg Artemis way too hard for what it is. And people give Starship too much credit for what it is (so far). (And I DO like the idea of Starship and hope it succeeds). If it succeeds things will be awesome!

Starship hasn’t made orbit yet. I’m hopefully it will, even factoring in Elon time (wasn’t he talking about reaching Mars unmanned in 2024?) it’s slow going.

I’m hopeful it will meat here falcons success, but until then compare what’s actually possible today.

That is a very unfair comparison. You are giving numbers for Starship going to NRHO, then landing the whole upper stage on the moon, then returning it to NRHO. That is a completely different ballpark to SLS's ‘dump a capsule in a lunar flyby which itself can't even get to LLO’.

And if the SLS/Orion architecture wasn't so underperforming, Starship could waste less energy making up for it.

Not really. If you have enough payload to LEO you can also throw something to TLI, just less. All commercial rockets like Falcon 9 or Atlas 5 can throw lots of payload to the moon as well. Even tiny rockets like Rocket Lab Electron have launched moon missions.

Now what is true that the further out you go, a hydrogen RL-10 based upper stage will win out better then a Falcon 9 based kerlox upper stage.

So while the payload to LEO between rockets can be pretty close, the payload to a moon orbit can be quite different.

2nd LEO should be something else.

Correct, I originally wanted to write LLO but that wasn't correct either as that requries a space craft to fly insertion and many rockets couldn't do that. But TLI is what all rockets should be capable of doing.

I've seen a lot of people claim that, but it's misleading. Falcon Heavy is the most powerful rocket to LEO, GEO, TLI (trans lunar injection), and higher energy orbits like the ones you use for Jupiter and beyond.

When SLS finishes development, it will also hold the record for all 3.

I’m curious about this too. Are any of the private companies anywhere near ready to send a ship to the moon and back?

SpaceX is closest, but no. Not until Starship flies.

If history is any guide and they haven't missed any big blockers though, then they'll get there - but I think a 10 year horizon is probably a reasonable expectation.

Falcon Heavy (existing SpaceX rocket, not human rated) can get a ship to above the moon and back today, but probably not within enough margin to land on the moon in one launch. Making a lander which launches on top of it would require substantial development work anyways, so not really close (and not planned).

Starship is a SpaceX rocket reasonably late in the development cycle, and is planned to land on the moon in an uncrewed demonstration flight no earlier than 2024, and with people during NASA's Artemis 3 mission no earlier than 2025. According to the plan this will be the first mission to land people on the moon since Apollo.

SLS at this point is not planning on launching a vehicle that lands on the moon, instead just a very very expensive taxi to a starship in lunar orbit which could have easily carried the astronauts there itself...

That said, it seems unlikely that a vehicle will go from "has never reached orbit and has a novel refueling model" to "is rated for human spaceflight" in a year or two. I think the Starship is cool as hell, but realistically we're probably looking at 2027+ before we see substantial missions on it.

On-orbit refueling is neither very complex nor untried.

Really? We've loaded that much cryogenic fuel before on a manned mission?

Pretty sure it's untried. Theoretically easy, just like launching starship is theoretically easy.

Fuel transfer is mechanically the same whether there are people around or not, and whether you are talking 1 ton of propellant or 100 tons.

It does matter if people aboard, there are more rules and procedures. You need a vessel with safeties that can allow them to eject safely if there's an anomaly.

Of course it's more challenging.

And it does matter if there's more fuel, you have to have valves and pipes that won't freeze after lengthy contact with cryogenic fuel. And you need larger pressure vessels, which scale in volume differently from surface area. It's not at all the same whether you move one ton or a hundred.

The fueling is done without people onboard.

But you still have to build additional safeties into the craft if it's rated for humans. A refueling craft is more complex than a non refueling craft. A crewed craft is more complex than an uncrewed craft (even if no one is aboard). A crewed, refueling craft is more complex still.

No earlier than dates are optimistic by nature. I could believe the dates if everything (from launches to environmental approvals) goes well, that is unlikely though.

Regardless of the dates, Artemis using starship as a lander seems practically guaranteed at this point, so SLS really is relegated to the role of unnecessary taxi...

Yes. If you send stuff to orbit you can probably also send stuff to the Moon, it's just a payload penalty.

Several Moon missions were launched on commercial rockets. Even tiny RocketLab launched one: https://en.wikipedia.org/wiki/CAPSTONE

Eh, once you get to orbit you are more than halfway there. Once you get to the moon you need only very little deltaV to make it back.

But yeah, they’re on completely different levels.

No. Falcon 9 can launch objects to the moon as well.

Not to and from the moon. It has a Delta v budget a little low for a full round trip that includes a landing and ascent, iirc. It could hurl something at the moon though.

SLS can't do that either ...

The Artemis 3 will launch on SLS and land humans on the moon?

Reply on news.ycombinator.com