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Comment by pclmulqdq | Hacker News Reader

Falcon rockets can't get to the moon. You need a lot more fuel to do that. That's why SLS and Starship are both being developed.

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In 1990's Dan Goldin, the NASA administrator at the time, was looking for ways to return to the Moon for cheap. One of the least expensive variants which was presented included launching multiple Protons and assembling lunar exeditionary complexes on LEO. The quoted number at that time was $1 billion to put boots on regolith again.

Falcon-9 is about as capable in terms of payload as Proton. And even without inflation the launch price is comparable. So, Falcon-9 is quite capable to get people on the Moon. It isn't really considered because there are other options and some additional requirements.

That plan was rejected for the reasons I stated in a sibling comment.

Completely terrible reasons. There is no good justification for SLS.

“HUMAN LUNAR RETURN X-PROJECTS APPROACH” (a Briefing to the Administrator, NASA Johnson Space Center, November 1995)

https://space.nss.org/lunar-base-studies-1996-human-lunar-re...

hey avmich, thnx 4 the memories ;)

SLS is needed only because they were not allowed to adopt on-orbit propellant transfer. With rockets like the Falcons, propellant (which is most of the mass needed to get something to the moon) is launched in smaller quantities and accumulated.

What sort of future in space do those advocating SLS imagine for us if moving a liquid from one tank to another is too challenging?

One where we just launch one rocket instead of building a giant orbital bomb slowly (accumulating fuel) and transferring all those explosives through a complex series of difficult rendezvous maneuvers? One rocket is risky enough.

There's a huge amount of extra risk involved in that sort of idea, which is why NASA isn't doing it, which can just be avoided with SLS and Starship.

It's actually less risky. Most of the launches are of propellant, which is completely replaceable. Reliability of a launcher is achieved by using it many many times, exposing all the gotchas. SLS will launch so infrequently it will be extremely risky.

And you didn't answer my question, so I will answer it for you. If simply transferring a liquid from one tank to another is too risky, then there is no future in space. No activities of any significance could ever be done there. With that established, we can shut down the human space program and lose nothing of value.

There is plenty of future in space by limiting propellant transfers to times when they are absolutely necessary. We can do them today, and have been able to for 30 years, and yet we rarely do, and never for the volumes of fuel you are proposing.

There's no reason to have humans on board while transferring fuel, the risk to human life from this "giant orbital bomb" (ridiculous fear mongering) is nonexistent. Anyway, the whole thing is a pointless waste of time and money. The only non-pork reason to return to the Moon is to blunt the impact of the PRC doing the same (should that happen.)

A “giant orbital bomb” is part of the Lunar Starship plan. Starship will launch tankers

> Starship HLS requires in-orbit propellant transfer in its mission profile. Prior to the launch of the HLS vehicle from Earth, a Starship variant configured as a propellant depot would be launched into an Earth orbit and then partially or fully filled by between four and fourteen Starship tanker flights carrying propellant. The Starship HLS vehicle would then launch and rendezvous with the already-loaded propellant depot and refuel before transiting from Earth orbit to Lunar orbit.

https://en.m.wikipedia.org/wiki/Starship_HLS

I’m a little confused why you call it a giant orbital bomb. It wouldn’t be particularly giant. Four reusable flights could only bring 600T of propellant to LEO. A single starship is fueled with 4600T of propellant, or 18400T of propellant to get that 600T into LEO. I would argue the starship itself is a much more giant bomb with all sorts of fire and stress and chances to explode. 600T of fuel exploding in orbit might not even be visible. But there’s been a number of tests of in orbit refueling and it doesn’t seem much more complex than, say, docking with a space station and transferring bags of mostly water without damaging them.

One giant rocket would also be a "bomb", and it would have to take a more dangerous path.

Docking isn't a safety risk.

Falcon Heavy is capable of going to the Moon or even Mars.

Technically so is falcon 9, but they can’t return and they have to be totally dry with no cargo, and definitely not a terrarium full of humans. Falcon heavy is even capable of going to Pluto. But it wouldn’t be a very interesting mission. More interesting would be launching unmanned probes.

Regardless, the plan is to use starships to build a LEO refueling platform and bring propellant for a lunar lander brought to orbit via a starship. Such a platform could also be used for Mars. It’s a much smarter move than trying to bring everything from earth in a single shot. And I can vouch for the sanity of the plan - I have almost 600 hours on KSP which makes me a bit of an expert ;-)

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