Shackleton Energy Company Launches Plan for First Lunar Mining Operation

[Robotbeat]

I think the correct statement here is surface to orbit vehicles could be made to be reusable more easily for the Moon than for Earth.

Thank you, that is what I meant to say.

So far as I know, the jury is still out whether practical RLVs for earth surface to orbit is doable.

Lunar surface to orbit has much smaller delta V budget (therefore less challenging mass fraction). And doesn't endure 8 km/s re-entry.

The atmospheric reentry makes the problem easier on the way down, not harder.

The Moon has the added complication of sharp, abrasive dust over its entire surface. Earth has the added benefit of the option to use non-propulsive terminal "landing" techniques like lifting runway landings, parachutes, and splash-downs. On the way up, the Earth also has an atmosphere that can be used as part of the reaction mass. Earth also has a much greater satellite navigation and satellite communication infrastructure already in place. Also, RLVs can be easily inspected and maintained without requiring being in a pressure suit to do so (or spend huge sums to live on the Moon). The cost of man-power on the Earth is around a hundred times less on the Earth compared to the Moon (and will likely always be far less expensive). Liquid oxygen on Earth is easily produced just with fractional distillation of the air, and fuel is easily produced with fractional distillation of stuff that's pumped out of the ground.

Really, is it necessary to say all this? It's all kind of obvious when you aren't in space cadet fantasy land.

And I support reusable landers (if we're going to be doing a bunch of lunar missions), mind you.

[Warren Platts]

I think the correct statement here is surface to orbit vehicles could be made to be reusable more easily for the Moon than for Earth.

Thank you, that is what I meant to say.

So far as I know, the jury is still out whether practical RLVs for earth surface to orbit is doable.

Lunar surface to orbit has much smaller delta V budget (therefore less challenging mass fraction). And doesn't endure 8 km/s re-entry.

The atmospheric reentry makes the problem easier on the way down, not harder.

The Moon has the added complication of sharp, abrasive dust over its entire surface. Earth has the added benefit of the option to use non-propulsive terminal "landing" techniques like lifting runway landings, parachutes, and splash-downs. On the way up, the Earth also has an atmosphere that can be used as part of the reaction mass. Earth also has a much greater satellite navigation and satellite communication infrastructure already in place. Also, RLVs can be easily inspected and maintained without requiring being in a pressure suit to do so (or spend huge sums to live on the Moon). The cost of man-power on the Earth is around a hundred times less on the Earth compared to the Moon (and will likely always be far less expensive). Liquid oxygen on Earth is easily produced just with fractional distillation of the air, and fuel is easily produced with fractional distillation of stuff that's pumped out of the ground.

Really, is it necessary to say all this? It's all kind of obvious when you aren't in space cadet fantasy land.

And I support reusable landers (if we're going to be doing a bunch of lunar missions), mind you.

Haha! You're steppin' into the trap--you really don't want to go there, my friend! I recommend reverting to your usual tactic of avoiding confrontation...

[Hop_David]

The atmospheric reentry makes the problem easier on the way down, not harder.

Round trip moon to EML1 is less than just the up leg to LEO.

5 km/s vs 9.5 km/s

Then on top of the 9.5 km/s you shed 8 km/s over an hours time by aerobraking.

So this is the comparison:
moon: 5 km/s, no atmospheric re-entry
earth: 9.5 km/s plus 8 km/s re-entry.

The Moon has the added complication of sharp, abrasive dust over its entire surface. Earth has the added benefit of the option to use non-propulsive terminal "landing" techniques like lifting runway landings, parachutes, and splash-downs.

Parachutes, TPS, wings are all mass penalties and possible failure modes a lunar vehicle doesn't suffer. And as mentioned, the delta v for the ascent and landing is about half the delta v for just the up-leg of an earth to LEO round trip.

The atmospheric reentry makes the problem easier on the way down, not harder.

On the way up, the Earth also has an atmosphere that can be used as part of the reaction mass.[/quote]

Last I heard Skylon hasn't flown.

Further, slings, rail guns and other non reaction mass launches are possible on the moon. Doing stuff like that in earth's troposphere is extremely difficult, if not impossible.

Further, earth's atmosphere mandates a higher vertical ascent that increases gravity loss.

Also, RLVs

What RLVs? An RLV that can accomplish 9.5 km/s and 8 km/s re-entry still hasn't come to pass.

can be easily inspected and maintained

With a single stage, no stage recovery is needed. No reassembly is required. With no TPS needed, you don't need a standing army to check the TPS tiles.

The inspection and maintenance is far less than that needed for an earth to surface spacecraft.

Also OTV maintenance can be made easier by using ORUs.

Really, is it necessary to say all this? It's all kind of obvious when you aren't in space cadet fantasy land.

Really, is necessary to point out 9.5 km/s > 5 km/s? And on top of  a nearly double delta V budget you have a 3000 degree F re-entry?

[Robotbeat]

I see you avoided nearly all my points other than "delta-v, delta-v."

In response that there are no RLVs:
There are no RLVs, but neither are there any reusable landers.

How many RLVs are in active development, though (i.e. millions being spent on them, metal being bent)?
I count at least three:
Falcon 9 reusable (currently readying the Grasshopper VTVL testbed) http://spacex.com/multimedia/videos.php?id=0 already has proven the lightweight reentry tiles on Dragon and has attempted several first stage recoveries to no avail before switching to the Grasshopper VTVL-like concept for recovery

Blue Origin's hydrogen-powered RLV http://hobbyspace.com/nucleus/index.php?itemid=28803 with some funding from CCDev2 going toward their hydrogen engine... they've already demonstrated VTVL technology with their New Shepherd program.

Skylon: http://www.flightglobal.com/news/articles/skylon-spaceplane-engine-technology-gets-european-funding-322765/ and http://www.innovationnewsdaily.com/218-skylon-space-plane-british-engine-test.html


Plus the Air Force/Lockheed $250 million flyback booster program:
http://defensesystems.com/articles/2011/12/07/agg-air-force-reusable-booster-system.aspx

Plus whatever XCor is cooking up: http://www.xcor.com/products/vehicles/frequent_flyer_and_teledyne_brown_spaceplane.html

And plus likely whatever this apparently well-funded group is doing:
http://forum.nasaspaceflight.com/index.php?topic=27572.0

How many fully reusable lunar landers are under active, funded development? None.

Shuttle was full of all sorts of expensive requirements that aren't strictly required for an RLV, like for large cross-range, a large minimum payload to polar orbit (even though Shuttle never launched from Vandenberg), a huge long payload bay that almost never was fully taken advantage of, a requirement to always be manned, and still it managed to be almost entirely reusable other than the external tank. It was also incredibly costly (which considering its requirement of "zip-code engineering," is a wonder it was the price it was), but it is basically fully reusable other than the drop tank.

So while it's true that neither exist right now, there has only been one single lunar lander design demonstrated that was even close to the class necessary for moving propellant around, and it was entirely expendable and very expensive. There have been countless orbital launch vehicles plus the mostly-reusable Space Shuttle. And there's something like half a dozen RLVs in active development at this moment.

Here's another point: Where does the fuel come from for a reusable lunar lander? You can't fill up a lander with regolith (even if it's slushy, which hasn't been directly verified by a lander), it must be processed with quite a large amount of infrastructure (perhaps tens of billions of dollars), none of which exists on the Moon. There are also no people on the Moon right now and no market for lunar propellant. But there are dozens and dozens of launches per year that could be served by an RLV which could also launch plenty of propellant.

If you gave an equal amount of funding... say, $5 billion, for an RLV for Earth and a reusable lunar lander (plus all the necessary infrastructure for filling up on the lunar surface for delivering propellant), who do you think would be successful? The amount of funding needed to make a reusable lunar lander PLUS all the new ISRU infrastructure and is probably more than enough to develop and demonstrate EVERY SINGLE RLV CONCEPT I listed above, including the most expensive Skylon (which wouldn't necessarily have the lowest cost per kg). And there are far more customers for putting ANYTHING in orbit versus just putting propellant into orbit.

[Robotbeat]

This idea that we should invest in a huge lunar mining operation to serve a market which doesn't exist instead of encouraging a cheap way to get into space in the first place (which could easily serve the same market plus many more new markets plus the existing launch market) is absurd. And I've wasted far too much time responding, here.

Shackleton can do whatever they want with the money they don't have, obviously, but in no way is it a substitute for inexpensive access to space. In the far future where lunar propellant mining for export makes any sense whatsoever, it will serve as a complement to cheap access to space, not as a replacement. For the Shackleton plan to be possible at all, cheap access to space will be required anyway. You need customers in order to have a business, after all.

[QuantumG]

I agree but it should be said that reusable lunar landers do make sense without ISRU - refueling at EML-1 - and there's a gradient between those two extremes with just some of the fuel or oxidizer supplied from ISRU.

[Robotbeat]

I agree but it should be said that reusable lunar landers do make sense without ISRU - refueling at EML-1 - and there's a gradient between those two extremes with just some of the fuel or oxidizer supplied from ISRU.

Oh, absolutely. I strongly support reusable landers even though I think lunar ISRU for export to, say, LEO or GSO isn't likely to be cheaper than Earth-sourced propellant for a similar additional investment in each (partly because the Earth-based side has the benefit of a ~quadrillion dollars of investment over time already) until well after several full RLVs have been fielded.

This is why I object when people compare lunar ISRU with an enormous investment in lunar infrastructure and equipment to just the ELVs we have today. The relevant comparison would be with RLVs or other (potentially cheaper) methods space access.

[Warren Platts]

I see you avoided nearly all my points other than "delta-v, delta-v."

In response that there are no RLVs:

There are no RLVs, but neither are there any reusable landers.
So while it's true that neither exist right now, there has only been one single lunar lander design demonstrated that was even close to the class necessary for moving propellant around, and it was entirely expendable and very expensive. There have been countless orbital launch vehicles plus the mostly-reusable Space Shuttle. And there's something like half a dozen RLVs in active development at this moment.

There was the DC-X; it was reusable. With its 4 RL-10 engines, it's exactly what a reusable SSTO Lunar tanker-lander would be like. Moreover, it worked in dusty environment and was turned around quickly with a small crew.

Here's another point: Where does the fuel come from for a reusable lunar lander? You can't fill up a lander with regolith (even if it's slushy, which hasn't been directly verified by a lander), it must be processed with quite a large amount of infrastructure (perhaps tens of billions of dollars), none of which exists on the Moon. There are also no people on the Moon right now and no market for lunar propellant. But there are dozens and dozens of launches per year that could be served by an RLV which could also launch plenty of propellant.

If you gave an equal amount of funding... say, $5 billion, for an RLV for Earth and a reusable lunar lander (plus all the necessary infrastructure for filling up on the lunar surface for delivering propellant), who do you think would be successful? The amount of funding needed to make a reusable lunar lander PLUS all the new ISRU infrastructure and is probably more than enough to develop and demonstrate EVERY SINGLE RLV CONCEPT I listed above, including the most expensive Skylon (which wouldn't necessarily have the lowest cost per kg). And there are far more customers for putting ANYTHING in orbit versus just putting propellant into orbit.

Marginal costs to an L1/L2 depot are what you should be looking at for an apples to apples comparison; for Earth based propellant to be cost competitive, costs to LEO would have to get down to < $100/kg. There is no way that is going to happen.

And $5B for a reusable LV on Earth isn't nearly enough.

And reusability isn't a panacea either. A reused SRB is 80% of a brand new one. Not game-changing.

And there aren't "dozens and dozens" of launches going on. I think the US had something like 18 launches last year.

And there's no point in putting propellant in orbit unless its to support BLEO exploration.

And the only BLEO exploration project that's big enough to provide a market for 500 to 1000 tonnes of propellant in LEO and that's also doable is a major Lunar IRSU base.

This is something we could be working on right now. It's actual exploration. Tech development is not exploration.

This idea that we should invest in a huge lunar mining operation to serve a market which doesn't exist instead of encouraging a cheap way to get into space in the first place (which could easily serve the same market plus many more new markets plus the existing launch market) is absurd.

You would have us twiddle our thumbs not even in LEO, but right here on Earth's surface until some sort of magic bean technology invents itself, if and when. Also, the market doesn't exist mainly because the supply doesn't exist. If we could put up a few thousand tonnes of propellant to L2, that would be game-changing and allow a truly sustainable Mars program, complete with a permanently staffed research station. That is something you should be for. You're shooting yourself in the foot by being negative about something you've never taken the time to understand.

Q: Why must we raid the HSF budget to develop commercial RLV's? The dozens and dozens of launches you mention aren't people mainly. So why not go after the science budget instead? They have more launches per year, and could really benefit from $100/kg launch services. Think they would go along with that? Why not? Isn't it absurd to be spending money on exploration before $100/kg cheap lift comes into being?

Shackleton can do whatever they want with the money they don't have, obviously, but in no way is it a substitute for inexpensive access to space.

Total straw man. Nobody here has claimed that Lunar ISRU is a substitute for "cheap lift". That's on you pardner. It's primary purpose is for moving outward, not inward back toward the Earth. You're still stuck in the old-fashioned, Apollo template of space exploration: that everything must come out of the gravity well of Earth. Boring and uncool....

And I've wasted far too much time responding, here.

You're right: arm-waving is a waste of time...

[Warren Platts]

I just watched the Bill Stone TED video. I guess it is his plan to bring it back to LEO. With aerobraking or electromagnetic braking, he probably could get back for $500/kg, maybe less.

The $15B to set up the operation I find hard to believe, however. I'd be interested to see how he plans on pulling that off. For NASA to pull that off using the ACES architecture would probably cost 10 times as much IMO.

EDIT: Bill also wants to haul plain water to LEO and then distill it there. Which will result in a lot of excess O2, unless he can convince people to buy propellant with a mass ratio of 8.

http://www.space.com/10619-mining-moon-water-bill-stone-110114.html

EDIT: Rockethub performance was pretty dismal: $5,517 / $1,200,000 = 0.46%

[Hop_David]

I see you avoided nearly all my points other than "delta-v, delta-v."

Delta V is a very important consideration. That you choose to ignore it damages your credibility.

How many RLVs are in active development, though (i.e. millions being spent on them, metal being bent)?
(snip)
How many fully reusable lunar landers are under active, funded development? None.

Your argument seems to be since development of lunar ISRU and vehicles isn't being done now, it shouldn't be done in the future. A "Stay The Course" argument.

A "Stay The Course" argument endorses the lion's share of funding to SLS and table scraps to Commercial. It endorses 7 to 8 billion per year for maybe flags and footprints to an NEO. Or maybe a brief stay on Mars. No ISRU. No thought of resource exploitation.

Like our present HSF program, lunar development would take about 6 to 8 billion per year. After 10 or 15 years you'd have substantial infrastructure. I see a series of goals for this infrastructure:
1: Propellant on the lunar surface
2: Propellant to EML1 and EML2
3: Propellant to GEO
4: Propellant to LEO

1, 2 and 4 would reduce difficulty of transportation to the moon. 3 and 4 would give a lunar base a source of revenue.

Propellant to LEO would make Earth surface to LEO RLVs more doable.

I want to see a human presence whose revenues exceed operating expense. If this is accomplished, growth of a HSF is inevitable. This is perhaps doable with a lunar base. Much less so for NEOs or Mars.

[Robotbeat]

Not my argument at all. I was merely responding (in a long-winded manner, granted) to your statement: "What RLVs?"

Delta-v is not the whole story; I am not ignoring it.

[Hop_David]

Not my argument at all. I was merely responding (in a long-winded manner, granted) to your statement: "What RLVs?"

Let me summarize: Some money is being spent or earth to LEO RLVs that don't exist yet. No money is being spent on lunar RLVs that don't exist yet.

From that you conclude lunar is a waste. A "Stay The Course" argument.

Delta-v is not the whole story; I am not ignoring it.

You correctly point out that aerobraking would be useful for earth to LEO RLVs -- Aerobraking can shave off 8 km/s from a 17 km/s round trip  delta V budget, reducing it to a more doable 9 km/s.

When you say it's an advantage over lunar, you're ignoring that lunar is much less than 17 km/s. Or even 9 km/s. It's 5 km/s.

Half the delta V budget and no need for TPS, wings, parachutes, any of that stuff. The challenges for these RLVs are far less formidable than what Musk, Bond, etc. face.

I will further note that Musk's Grasshopper video shows use of reaction mass to shed re-entry velocity, in addition to the usual aerobraking. This makes for a delta V budget even greater than 9 to 10 km/s and an even more difficult mass ratio. If his second stage could refuel in orbit, his design becomes more plausible.

[Robotbeat]

Not my argument at all. I was merely responding (in a long-winded manner, granted) to your statement: "What RLVs?"

Let me summarize: Some money is being spent or earth to LEO RLVs that don't exist yet. No money is being spent on lunar RLVs that don't exist yet.

From that you conclude lunar is a waste. A "Stay The Course" argument.
...

Nope. Not my conclusion and not my argument.

[Hop_David]

Nope. Not my conclusion and not my argument.

You have an argument?

[Robotbeat]

Nope. Not my conclusion and not my argument.

You have an argument?

According to you in your post.

[Hop_David]

Nope. Not my conclusion and not my argument.

You have an argument?

According to you in your post.

According to you that's not your argument.

So I'm asking for clarification. Do you have an argument?

[Robotbeat]

Nope. Not my conclusion and not my argument.

You have an argument?

According to you in your post.

According to you that's not your argument.

So I'm asking for clarification. Do you have an argument?

Yes, my argument is that it's worthless to compare the cost of lunar ISRU propellant in LEO to the cost of the very expensive ELVs often used now, which is often done to justify lunar ISRU.

The relevant comparison is with whatever LVs could be developed for a similar sum of investment, which you'd have to say includes RLVs. And then you have the fact that RLVs could serve other markets, so their investment costs are spread. Another point is that you likely wouldn't have a sizable market to sell lunar ISRU to unless you had cheap access to space (i.e. RLVs) in the first place. Additionally, having RLVs would make installing the lunar infrastructure needed for extensive lunar ISRU far more reasonable. In other words, I'm frustrated with the apparent opposition to RLVs coming from folks here who are in favor of huge amounts of investment for lunar ISRU instead.

I'm pretty sure the Shackleton folks are not opposed to RLVs, so my argument is not pointed towards them.

Personally, I think work on both can proceed in parallel, but it doesn't make sense to spend 11 or 12 figures on lunar ISRU in the meantime.

[Warren Platts]

Yes, my argument is that it's worthless to compare the cost of lunar ISRU propellant in LEO to the cost of the very expensive ELVs often used now, which is often done to justify lunar ISRU.

Not the case: the comparison is usually made by comparing optimistic, but not pie-in-the-sky estimates of the next generation of LV's, ELV's and RLV's. 3 to 5 $K/kg in other words. When Elon can beat $3K/kg, I'll believe. Hempsell says even Skylon's cost to LEO will be $8K/kg upon inception, and $1K/kg when in mature service.

Meanwhile, a 15,000 mT/year water operation on the Moon (about 6 Olympic sized swimming holes) would produce 10,000 mT of LH2/LO2, of which 4,000 mT could be transferred to L1/L2 with a fully reusable, SSTO tanker-lander. A Moon base self-sufficient in propellant won't be much more to operate than ISS, especially considering progressively lower, albeit marginally, launch costs from Earth. $2B/year overhead is not unreasonable, once construction of the base is more or less complete.

Thus, $2B/4,000 mT = $500/kg. If a way could be devised to use aero- or electromagnetic braking, this propellant could be transferred the rest of the way to LEO essentially for free. If done fully propulsively, the cost would be roughly $1200/kg. Those figures are cost competitive to any non-pie-in-the-sky, i.e., reasonable, prediction on what Earth to LEO costs are going to be within the next several decades.

The problem is physics, not dollars. Earth has a deep gravity well. Getting out of it is damned hard with a decent mass fraction. LV's are near the best of what is physically possible. There simply isn't much scope for improvement. Such improvements as are possible will be at the margins--there is no magic bullet in the offing.

The relevant comparison is with whatever LVs could be developed for a similar sum of investment, which you'd have to say includes RLVs. And then you have the fact that RLVs could serve other markets, so their investment costs are spread.

Essentially, you're proposing that we gut the exploration budget--again!--to fund tech development of RLV's. We've already had one $100B experiment. It was called Shuttle. The results were mixed. It did not result in massive savings over ELV's. Yes, yes, I know, there were a ton of "unnecessary" requirements like cross range capability, man-rating, down mass, etc.

But still it doesn't follow that the next generation of RLV's will dramatically lower launch costs compared to the best, next-generation ELV's.

One thing I notice with guys like you and Martijn who are relentless RLV boosters is that you never say how "cheap" is cheap enough. I get the feeling you guys will never be happy until launch costs get down to $10/kg--about what it costs to fly from New York to London.

Thus, the fact that the first $100B wasn't enough means nothing to you guys. You're fully ready to put the HSF program standby for another 15 years so the next $100B can be spent on RLV's again. And since there's no way spending this $100B will achieve $10/kg, then the third $100B will have to be spent, ad infinitum!

Honestly, here's a direct question for you Robotbeat: You tell us: If we blow off Lunar exploration in order to fund RLV's, just how cheap do you think it will get?

It's just not that easy. Skylon says $1000/kg. How is Elon's flyback booster concept going to blow that out of the water by an order of magnitude??? Keep in mind that a refurbished SRB costs 80% of brand new one. Maybe liquids will be easier to refurbish, but still, it's going to wreck havoc on your payload mass fraction. I wish them all the luck in the world, but $10/kg or $100/kg simply isn't in the cards.

Another point is that you likely wouldn't have a sizable market to sell lunar ISRU to unless you had cheap access to space (i.e. RLVs) in the first place.

Not true: a Lunar ISRU program could make available to NASA 3,000 mT per year that could be used for a sustainable Mars program for $2B/year. That's a pretty big market.

Additionally, having RLVs would make installing the lunar infrastructure needed for extensive lunar ISRU far more reasonable. In other words, I'm frustrated with the apparent opposition to RLVs coming from folks here who are in favor of huge amounts of investment for lunar ISRU instead.

Why are you going after the HSF budget? Why not take it from the Science Mission Directorate instead? What's the difference? Or leave it up to the Pentagon. They want RLV's badly enough, they will develop them. Why should NASA subsidize DoD? And if Elon et al. want to develop RLV's, nobody's stopping them. LV's are old school, and the NASA's success at developing LV's is checkered at best. NASA should be concentrating on doing something new. Exploration in other words, and as an oil man, I mean exploration in the same way that Exxon uses the word.

I'm pretty sure the Shackleton folks are not opposed to RLVs, so my argument is not pointed towards them.

Then you're argument is pointed at nobody. Nobody is opposed to RLV's. Certainly not me nor Hop David. Go ahead build them. Good Luck! But if you'll watch Bill Stone's video's and read his interviews, his analysis is exactly the same was what I just reiterated here: LV costs are NOT going to be basically free for the foreseeable future; therefore, Lunar propellant is a winning opportunity.

Personally, I think work on both can proceed in parallel, but it doesn't make sense to spend 11 or 12 figures on lunar ISRU in the meantime.

Bill Stone is proposing to spend 11 figures on Lunar ISRU. Frankly, I can't see it. Maybe he knows something I don't. But for NASA to spend 12 figures on Lunar ISRU is in line with the big 3 other projects NASA has undertaken: Apollo, Shuttle, ISS. There is no better 4th $100B project, if you ask me. Certainly, another $100B tech development project on RLV's is not it....

[Patchouli]

Essentially, you're proposing that we gut the exploration budget--again!--to fund tech development of RLV's. We've already had one $100B experiment. It was called Shuttle. The results were mixed. It did not result in massive savings over ELV's. Yes, yes, I know, there were a ton of "unnecessary" requirements like cross range capability, man-rating, down mass, etc.

But still it doesn't follow that the next generation of RLV's will dramatically lower launch costs compared to the best, next-generation ELV's.

One thing I notice with guys like you and Martijn who are relentless RLV boosters is that you never say how "cheap" is cheap enough. I get the feeling you guys will never be happy until launch costs get down to $10/kg--about what it costs to fly from New York to London.

Thus, the fact that the first $100B wasn't enough means nothing to you guys. You're fully ready to put the HSF program standby for another 15 years so the next $100B can be spent on RLV's again. And since there's no way spending this $100B will achieve $10/kg, then the third $100B will have to be spent, ad infinitum!

Honestly, here's a direct question for you Robotbeat: You tell us: If we blow off Lunar exploration in order to fund RLV's, just how cheap do you think it will get?

It's just not that easy. Skylon says $1000/kg. How is Elon's flyback booster concept going to blow that out of the water by an order of magnitude??? Keep in mind that a refurbished SRB costs 80% of brand new one. Maybe liquids will be easier to refurbish, but still, it's going to wreck havoc on your payload mass fraction. I wish them all the luck in the world, but $10/kg or $100/kg simply isn't in the cards.

Actually $100 per kg is possible if the hardware can be reused 50 to 200 times.
If propellant  was the primary the cost you could do $10 per kg.
It's not even half of 1% of the cost of present launches which can be as low as $3093 per kg with Zenit.
F9-H will offer $1500 per Kg and even vehicles like Ares V/SLS can do sub $2500 per Kg if they have STS like flight rates.

This is with expendable hardware.

Skylon has a high R&D cost and is very dependent on flight rates initially it's assumed the flight rates would be low and the vehicles subject to inspection after each flight.

But if the flight rate ramps up sub $100 per kg numbers could be possible.

[Hop_David]

The relevant comparison is with whatever LVs could be developed for a similar sum of investment, which you'd have to say includes RLVs.

Given a 9 to 10 km/s delta V budget and 8 km/s re-entry, I don't think earth to LEO RLVs are practical. Throwing money at the problem won't change this, in my opinion.

Personally, I think work on both can proceed in parallel, but it doesn't make sense to spend 11 or 12 figures on lunar ISRU in the meantime.

I believe a propellant depot lunar architecture (such as ULA's) would do a lot to bring about less expensive earth to LEO vehicles.

1) It could provide the flight rate new companies need to amortize research and design expense.

2) With lunar propellant in LEO, reaction mass can be used to shed re-entry velocity. Thus returning vehicles would not suffer the high temperature and stress of an 8 km/s re-entry. This would be make earth to LEO RLVs much more doable.