SpaceX for Moon Base

[Ictogan]

Exactly, LunOx (Lunar Oxygen) would be the first industry on the moon.  Only need decent LOx and then reload ascent on the surface.  The logical step would then be a tanker from the Lunar surface to carry LunOx to LLO.  Then use it to return to earth.  As well it could ultimately become worth shipping LunOx to LEO and refuel for the return trips to the moon or onto Mars.

Why climb out of the Earth's gravity well if you don't need too?

Because each one way trip between LEO the Lunar surface takes about 5.5km/s of delta-V. When considering that the tanker would need twice that to get from lunar surface to LEO and back to the lunar surface again, this becomes 11km/s - a similar amount to what's needed to get from earth's surface to LEO and back to earth's surface(assuming reentry with a heatshield and propulsive landing).

Delivering earth oxygen to LEO would still be a lot easier.

The basic delta-v requirements are well defined in the ACES paper... delivering propellant to EML-2 puts it on the gravity well cusp -- ready to depart for interplanetary destinations or drop to the Lunar surface.  Tankers never will travel to Lunar surface (in a sane world that can do the maths*).

* Which I wished I lived in...

Meant that mostly as a point against shipping lunar oxy to LEO, not to EML-2. Should have pointed that out.

[clongton]

Earth-Moon Transportation: We need to turn all this thinking completely around. We need to source propellant and oxidizer totally from lunar materials. Transportation between the lunar surface and LEO should be in a vehicle that departs lunar surface, not LLO, with full tanks, arrives in LEO with enough propellant and oxidizer remaining for the return trip to the lunar surface, again not to LLO. We need to stop thinking of the lunar surface as the destination. It's not. Instead it is the beginning and ending of the journey. LEO is the destination, not the moon. It is a round trip from the moon to LEO and return to the moon. Thought of that way it completely changes the way we think about this. Earth is left completely out of the equation. That's how we need to design the Earth-Moon transportation system. ALWAYS *begin* the trip from the location with the smallest gravity well with completely full tanks. And return there with what's left after destination arrival; pushing less mass because of the expended propellant. Forget about climbing up out of earth's deep gravity well just to get to LEO. Leave that to the taxis.

The delta-v requirements are lunar surface to LEO and back again, begun with full tanks.

[AncientU]

Earth-Moon Transportation: We need to turn all this thinking completely around. We need to source propellant and oxidizer totally from lunar materials. Transportation between the lunar surface and LEO should be in a vehicle that departs lunar surface, not LLO, with full tanks, arrives in LEO with enough propellant and oxidizer remaining for the return trip to the lunar surface, again not to LLO. We need to stop thinking of the lunar surface as the destination. It's not. Instead it is the beginning and ending of the journey. LEO is the destination, not the moon. It is a round trip from the moon to LEO and return to the moon. Thought of that way it completely changes the way we think about this. Earth is left completely out of the equation. That's how we need to design the Earth-Moon transportation system. ALWAYS *begin* the trip from the location with the smallest gravity well with completely full tanks. And return there with what's left after destination arrival. Forget about climbing up out of earth's deep gravity well just to get to LEO. Leave that to the taxis.

The delta-v requirements are lunar surface to LEO and back again, begun with full tanks.

I like your vision as a potential end point, but the pragmatist in me balks at 'designing' the full system that way. What we should do, IMO, is get started with what we have, which includes a fairly vibrant society (though clearly dysfunctional in many respects) on Earth with a few fossil spacecraft on the Lunar surface.  We want to arrive at a self-sustaining space infrastructure.  How do we go from here to there?

Waterfall development might be fine if the USG or some fictitious international collaboration is going to foot the entire bill -- which isn't likely -- so we have to depend on bootstrapping.  What can we start with, that is the question...

So, let's start from where we are and see where we can get.

[clongton]

I like your vision as a potential end point, but the pragmatist in me balks at 'designing' the full system that way. What we should do, IMO, is get started with what we have, ...

Didn't intend to suggest that we *start* there. It's what we want to transition to as rapidly as lunar ISRU development will allow.

[AncientU]

I like your vision as a potential end point, but the pragmatist in me balks at 'designing' the full system that way. What we should do, IMO, is get started with what we have, ...

Didn't intend to suggest that we *start* there. It's what we want to transition to as rapidly as lunar ISRU development will allow.

I wouldn't be surprised if the 'end point' is something along your lines, but markets tend to find the path of least resistance to getting the job done -- while radically altering what the 'job' itself entails.  Doing something gets things moving... where the trail leads is the adventure that I look forward to enjoying.

[AncientU]

This is essentially the fork in the road for 'exploring' space.  Do we just go, have what we have, use what we can get on the launch pad... and see what happens?  Quite a departure from the exquisitely planned mission approach, decades long roadmap approach.

[watermod]

This is essentially the fork in the road for 'exploring' space.  Do we just go, have what we have, use what we can get on the launch pad... and see what happens?  Quite a departure from the exquisitely planned mission approach, decades long roadmap approach.

The problem is a human one that vision disappears into bureaucracy with multi-decade plans.   In the end nothing useful happens.

[envy887]

Earth-Moon Transportation: We need to turn all this thinking completely around. We need to source propellant and oxidizer totally from lunar materials. Transportation between the lunar surface and LEO should be in a vehicle that departs lunar surface, not LLO, with full tanks, arrives in LEO with enough propellant and oxidizer remaining for the return trip to the lunar surface, again not to LLO. We need to stop thinking of the lunar surface as the destination. It's not. Instead it is the beginning and ending of the journey. LEO is the destination, not the moon. It is a round trip from the moon to LEO and return to the moon. Thought of that way it completely changes the way we think about this. Earth is left completely out of the equation. That's how we need to design the Earth-Moon transportation system. ALWAYS *begin* the trip from the location with the smallest gravity well with completely full tanks. And return there with what's left after destination arrival; pushing less mass because of the expended propellant. Forget about climbing up out of earth's deep gravity well just to get to LEO. Leave that to the taxis.

The delta-v requirements are lunar surface to LEO and back again, begun with full tanks.

Lunar surface to LEO and back is 11.8 kms, minimum (all propulsive). That's not much better than Earth surface to EML1/2 and back with aerobraking.

The main issue I have with starting at the lunar surface and taking the same vehicle all the way to LEO and back is it eliminates low thrust, high specific impulse vehicles.

Ideally, you would have deep space SEP/NEP/NTR taxis, shuttling propellant and cargo between dedicated high thrust vehicles for getting into and out of the gravity well.

[TrevorMonty]

Start from LEO with low cost fuel ($1000/kg) thanks to Blue and SpaceX RLV. Then add ISRU for surface to lunar orbit stage and eventually surface to LEO.

[sanman]

Lunar surface to LEO and back is 11.8 kms, minimum (all propulsive). That's not much better than Earth surface to EML1/2 and back with aerobraking.

The main issue I have with starting at the lunar surface and taking the same vehicle all the way to LEO and back is it eliminates low thrust, high specific impulse vehicles.

Ideally, you would have deep space SEP/NEP/NTR taxis, shuttling propellant and cargo between dedicated high thrust vehicles for getting into and out of the gravity well.

What about VASIMR? Nuclear-powered VASIMR from lunar surface to LEO and back could potentially do a lot of round trips.

[Pete]

If you are assuming enough infrastructure to bulk mine LOX on the Moon, and you want to figure out the best way to use it..
Why fiddle around with spaceships landing on the Lunar surface??

Build yourself a 1.2km mass driver flat on the surface of the moon, put some oxygen in a sturdy aluminum container (both obtainable from local regolith), and fire off the thing at a mere 50g.

That, and only a few dozen m/s of impulse (use oxygen venting if you have to!)  is quite sufficient to get the container to earth-moon Lagrange point, where it can be picked up and used wherever with minimal maneuvering.

Building a 50g mass driver is well within our capability.
Making it just over 1 km in length is not that large a project.
Making a container capable of handling 50g acceleration is not a problem, as long as you don't put squishy organics in it.

[Nilof]

Lunar surface to LEO and back is 11.8 kms, minimum (all propulsive). That's not much better than Earth surface to EML1/2 and back with aerobraking.

The main issue I have with starting at the lunar surface and taking the same vehicle all the way to LEO and back is it eliminates low thrust, high specific impulse vehicles.

Ideally, you would have deep space SEP/NEP/NTR taxis, shuttling propellant and cargo between dedicated high thrust vehicles for getting into and out of the gravity well.

What about VASIMR? Nuclear-powered VASIMR from lunar surface to LEO and back could potentially do a lot of round trips.

SEP gives you more power per unit mass than NEP at 1 AU from the sun. Both are really more capable in heliocentric orbits though, where their thrust is relatively high compared to the characteristic timescales of the orbit.

Electric propulsion to the moon takes a fairly long time compared to chemical, unfortunately. Depending on the launch rate of your tankers you might get more payload per unit time with chemical than with electric propulsion, because the chemical stage can be reused more time (unlike for mars trips where electric propulsion can potentially be reused more often because of more lenient launch windows).

Ultimately I think that tethers or any other reusable-propellant architecture is the best bet for getting stuff to the moon cheaply, since they can give you both the benefits of high throughput, short transfer times, and avoiding high propellant and energy expenditures. But near-term I think it's difficult to beat plain chemical propulsion for delivering payloads to the moon.

[AncientU]

We don't need exotic, someday solutions.  We have the technology to get a Cis-Lunar program running, refueling, landers, and all.  If we refuse to use it, why does anyone think we'll build more sophisticated systems?

There will be roles for SEP, NEP, whatever once infrastructure enables growth, and growth demands a range of solutions for different aspects of the tasks that are happening.  Like a great ship... must be underway to steer.

[guckyfan]

I note that this thread takes the opposite way most threads go. Usually there is a general discussion which ends with how it can be done with SpaceX assets.

Here we see a thread dedicated to what SpaceX might do for a Moon Base. That thread slips into general far distant future technologies and developments which have no connection whatsoever to what SpaceX does or may do in the foreseeable future.

[blasphemer]

The delta-v requirements are lunar surface to LEO and back again, begun with full tanks.

Why would you do that?? Such a huge delta-v would require massive propellant tanks and tiny payload. Not efficient at all. Unless I somehow misunderstood your post..

Here is how it should look like IMHO:

1. Launch from lunar surface with enough delta-v to reach LEO depot (2.74 km/s).
3. Refuel empty tanks at LEO depot, launch back to L1 with enough delta-v to reach it (3.77 km/s).
4. Refuel empty tanks at L1, burn for Moon surface with enough delta-v for landing (2.52 km/s).

Delta-v requirements for the spacecraft never exceed comfortable 4 km/s. Lunar surface depot and L1 depot is kept full mainly from Lunar ISRU, LEO depot is kept full mainly from Earth.


Alternatively, you could have a lander repeatedly going between Lunar surface and L1 depot, and a ship repeatedly going between LEO and L1, of course both refueling after each burn. Requires one more stop along the way and transfer of cargo but may be advantageous due to crafts being specialized for their task. Also alternatively, depot may be at LLO instead of L1.

[philw1776]

Lunar surface to LEO and back is 11.8 kms, minimum (all propulsive). That's not much better than Earth surface to EML1/2 and back with aerobraking.

The main issue I have with starting at the lunar surface and taking the same vehicle all the way to LEO and back is it eliminates low thrust, high specific impulse vehicles.

Ideally, you would have deep space SEP/NEP/NTR taxis, shuttling propellant and cargo between dedicated high thrust vehicles for getting into and out of the gravity well.

What about VASIMR? Nuclear-powered VASIMR from lunar surface to LEO and back could potentially do a lot of round trips.

No expensive to develop politically infeasible space Nuclear reactor exists.
VASIMR is unproven.
Even a multi-megawatt VASIMR has order of magnitude too little thrust to do lunar takeoff.
VASIMR is for deep space with T/W << 1

SEP LEO to LLO would be orders of magnitude more feasible.

[Norm38]

I can see SpaceX being interested in hauling cargo to the moon, not sure about bringing anything back but people. Their architecture is methane, their ISRU won't work. So how do any of their ships get back up off the surface while delivering any cargo?  The answer is they don't.

Cargo to build a base will be mostly one way. The big reusable ships deliver one-use landers to LLO, then head back to Earth. The landers get scrapped for their refined metals that a growing base needs.

Personel ride dedicated LLO-Surface taxis that refuel from ships/tankers/stations in LLO. Lunar supplied LOX can
come online when possible, but methane comes from earth. That way the amount of mass coming up from Luna, and hence fuel, is minimized.

SpaceX may supply the lunar taxi, they may not. I see them as bulk freight haulers.

[Robotbeat]

Pah, the BFS presented at IAC had 9.9km/s delta-V. It takes only 9km/s from LEO to the Moon's surface and then launching back and landing on Earth, maybe even less than that (8.6-8.8km/s) if you're clever.

So you already have ~1km/s in extra performance.

Now if you refuel in something like supersynch GTO instead of LEO, you'll add another >2km/s to that margin, giving you tons of extra performance for bringing cargo both ways.

[Nilof]

I can see SpaceX being interested in hauling cargo to the moon, not sure about bringing anything back but people. Their architecture is methane, their ISRU won't work. So how do any of their ships get back up off the surface while delivering any cargo?  The answer is they don't.

Cargo to build a base will be mostly one way. The big reusable ships deliver one-use landers to LLO, then head back to Earth. The landers get scrapped for their refined metals that a growing base needs.

Personel ride dedicated LLO-Surface taxis that refuel from ships/tankers/stations in LLO. Lunar supplied LOX can
come online when possible, but methane comes from earth. That way the amount of mass coming up from Luna, and hence fuel, is minimized.

SpaceX may supply the lunar taxi, they may not. I see them as bulk freight haulers.

According to the results from LCROSS, the ice in the cold traps is a mix of CO, H2O, and CO2. Methalox ISRU should be just as attractive for the Lunar poles as for Mars, the main difference being that you replace atmospheric ISRU with more mining for ice. The lunar equator, on the other hand, is a bit drier, so only LOX ISRU works there which tends to push design towards hydrolox due to its higher O/F ratio.

Alternatively, if planetary resources or some other company starts making propellant from carbonaceous chondrite NEO's, that could provide Methane + LOX as well, since carbonaceous chondrites are carbon rich. Methalox is a great propellant combination for ISRU almost everywhere, not just for Mars.

[savuporo]

Here's a novel idea for a SpaceX for moon base: bulk buy of F9 launches.

If you want a moon base, build a moon base and stop screwing around with more launch vehicles.