What today is better than the Saturn V? That thing could put something like 3x the mass into lunar orbit than the Falcon Heavy.
The only missing piece is that it would be nice to use cryogenic fuels but these outgas over time so long duration is not a thing. Solving the on-orbit refueling puzzle would make this sort of endeavor pretty straight forward from a planning standpoint.
For example the stage of the Apollo mission that took it from Earth orbit to a trajectory that would intercept the Moon was https://en.wikipedia.org/wiki/S-IVB, which nearly twice the maximum payload of the Falcon Heavy. Do you really want to trust this step to a rocket that has to be assembled and fueled in space?
Yes. Isn’t that the next logical step to developing space—the ability to build structures in orbit?
That aside I wouldn’t object to building a Saturn V either.
I think you're totally right about this. If we want to really get going on living in space or even just doing certain manufacturing processes in space, it seems like we're going to need to start building real structures in orbit rather than fitting everything into a launch or two.
My guess is that, if it doesn't happen now, we'll start doing construction in orbit if/when we start mining the Moon or asteroids. Not having to haul equipment up Earth's gravity well and producing fuel in situ seems like it will allow small launches on reusable "tugs" to become the most efficient means of getting things into space.
There's a chicken and egg problem at work here. The robotics technology to do orbital construction exists, and in fact has existed for a couple of decades now. Nobody wants to fly it because the older technology - which amounts to “spend lots of money to fit your payload in a single rocket fairing” - has worked so far. The James Web Space Telescope will have a 6.5 meter primary optic. It will require something like 70 separate deployments in order to deploy the primary optic and the sunshield.
At some point, custom designing hundreds of deployment mechanisms for every single mission becomes both more expensive and higher risk than just flying a damned robot arm. As does “just build a bigger rocket”.
FYI, robotic refueling on orbit has been demonstrated a couple of times (Orbital Express and RRM).
Do you know how many times two objects were successfully docked in space? And how many times they did that automatically?
> Also that imposes very severe constraints on size and shape of those pieces.
Objection to "very severe". You can have your standard fairing size full, with diameter about 5 meters and length of 15 meters or so. That's quite comparable to 6.6 meters diameter of Saturn-V payloads, is more than LEM without legs. What shape constraints you have in mind?
> This is not technology that we have demonstrated in a meaningful way.
We didn't demonstrate orbital docking technology?
> nearly twice the maximum payload of the Falcon Heavy.
But it was launched with one rocket altogether. Nobody prevents us from launching the booster stage separately and dock it with spacecraft on LEO. More, nobody prevents us from sending analog of Apollo spacecraft and LEM to the moon separately - with their own booster each. Those variants were considered in 1960-s and rejected purely on the basis of time to develop the technology - something which we have today well developed.
> Do you really want to trust this step to a rocket that has to be assembled and fueled in space?
Let me remind you that Gemini and Atlas-Agena stage docked and changed orbits in mid-1960-s, confirming that it at least can be done with then-current technology. Today ISS has a history of pushes by Shuttle, of refuels with Progress and ATV ships and I'm not sure what prevents using similar - though not identical - approach with translunar injections.
You are right that it would be possible to send the Apollo spacecraft and LEM to the Moon separately, to join there, but the Apollo spacecraft is 2/3 of that mass. The rocket to do the Apollo spacecraft by itself exceeds the specs that we can launch on Falcon Heavy.
It would be more doable to build a multi-stage rocket in space and fire that. So one launch for Apollo+LEM, 2 launches for 2 booster stages. Put the three together and off you go. Of course this requires designing a new rocket, designed to be carried into space, to dock robotically, and then launch. Which is doable. But also isn't current tech.
If we're going to build a new rocket ANYWAYS for this mission, I think it makes more sense to cross fingers and wait for SpaceX's SuperHeavy + Starship configuration.
Update: While looking for current news on that, I found that SpaceX building SuperHeavy rockets in two locations. And I found that, today, they reported raising a billion dollars in funding for their development efforts. Which I submitted as a news article because I think that it is of interest separately from the NASA discussion.
…if all goes well. If you have to pause countdown of a rocket to check some part, it is “less ideal” if that rocket is in space.
Also, if you have to cancel countdown to try again at a later date, how do you get unstable fuel such as liquid oxygen out? Venting it may seem easy, but it changes the rocket’s trajectory. Even more problematic: how do you get new fuel in, so that you can retry a launch?
I agree that we don't have some components to take "off the shelf" - lunar module being the primary example. But "to put a payload on a rocket which never flew on this rocket" is not the "not current tech" - and since we have docking components, including robotic docking, existing elsewhere, I would argue that it won't require any significant time (like 5 years) to get ready.
The point is that we don't need to build rockets to go to the Moon - we have them already. We currently don't have lunar module - and we'll need to create that. Also we didn't do some specific integration of existing technologies - space boosters, docking etc. - but making that is way easier than making a new rocket.
> The component that I laid out is larger in both diameter and length than the standard fairing size you list.
It's not necessary to re-create 3rd stage of Saturn-V to fly to the Moon. Today there are better ways - using the existing launchers.