Discussion The next 100 years..

[Urwumpe]

Well I didn't meen composites like ceramics and metal mixes I meant plastics... Why don't we make modules out of hard plastics...

Do you know the VST of hard plastics? I do.

 

[HopDavid]

An era when permafrost on the Moon would have been a perfectly respectable concept.

Permafrost on the moon remains a respectable concept.
NASA radar finds ice deposits at Moon's North Pole

Even if the moon did have rich ores, I don't believe lunar gold, platinum or diamond mines could enjoy a return on investment.

Lunar water is another story.

(sorry about thread necromancy).

 

[T.Neo]

Permafrost on the moon remains a respectable concept.

Yes and no. At the poles there seems to be considerable water ice deposts, but the rest of the surface is relatively dry- I was referring to ice abundant over the entire surface.

Even if the moon did have rich ores, I don't believe lunar gold, platinum or diamond mines could enjoy a return on investment.

Lunar water is another story.

To who are you going to sell this water? Earth is covered with it, so to sell it to us would be like "selling coal to Newcastle".

Of course, selling it to use as rocket propellant... physics wise, the concept may be sound. The problem is that it isn't only physics, it's logistics, infrastructure, and economics as well. On Earth we have literally thousands of years of infrastructure that is developed for us.

On the Moon, infrastructure is everything. The problem is that there is absolutely no infrastructure on the Moon, and any infrastructure you want to put on the Moon will have to be taken there (difficult and expensive) or built there (difficult, unknown, and also expensive).

The cost of setting up and maintaining that infrastructure quickly outweighs any physics advantage of selling lunar propellant.

A lunar propellant mine would do (if feasible at all) for at least several tens of billions of dollars extra, what a means to effectively use Earth-launched propellant could do for far less money, far less risk, and far less time. We don't need it for BEO exploration, it is just a money-trap there. I personally want to see people land on Mars in my lifetime... :dry:

You may save rocket launches from Earth for propellant, but now you have to launch replacement parts... consumables... crews (if your propellant mine has a human presence, which many vehemently suggest), food, even replacement landers and so on. Soon it all adds up. Already the rocket equation means you could end up producing more propellant to get your propellant somewhere useful, than you would use as a 'product'.

 

[HopDavid]

Yes and no. At the poles there seems to be considerable water ice deposts, but the rest of the surface is relatively dry- I was referring to ice abundant over the entire surface.

There's estimated to be 600 million tonnes at the north pole in sheets of ice at least two meters thick.

True, this is a relatively small portion of the moon.

But then again, Hawaii and Japan are a small fraction of the Pacific ocean. Should the worth of these islands be disregarded for that reason?

To who are you going to sell this water? Earth is covered with it,

Thank you for pointing out the obvious. I will return the favor.

Earth's surface isn't the only realm of economic activity. We have extensive and valuable assets in orbit.

LEO and GEO are not covered with water.

Earth's surface is 9 to 10 km/sec from LEO. Any earthly propellant delivered to GEO must be delivered with multi-stage expendables.

On the other hand, lunar propellant is 2.5 km/s from EML1. And EML1 is .7 km/s from LEO (with aerobraking)

Given a 4.5 km/s EML1-LEO round trip and a 5 km/s moon to EML1 round trip, propellant delivery can be accomplished with single stage, reusable vehicles.

Of course, selling it to use as rocket propellant... physics wise, the concept may be sound. The problem is that it isn't only physics, it's logistics, infrastructure, and economics as well. On Earth we have literally thousands of years of infrastructure that is developed for us.

I'm not talking about manufacturing space ships, or computers on the lunar surface. Or even mining iron or aluminum. I'm talking about splitting ice to make hydrogen and oxygen.

The cost of setting up and maintaining that infrastructure quickly outweighs any physics advantage of selling lunar propellant.

The cost of establishing a lunar propellant mine remains an open question. Rather than use BFRs like Ares or SLS I would go with something like the ULA lunar architecture.

It also remains an open question how much human presence would be needed. Mining companies such as Rio Tinto are already investing in telerobotics. Any hard to reach and/or dangerous workplace could benefit by advancing the state of art for teleoperated equipment.

The moon is one of the few places where teleoperated mining equipment is remotely plausible. Light lag is less than 3 seconds. And LRO has demonstrated high bandwidth is doable.

A lunar propellant mine would do (if feasible at all) for at least several tens of billions of dollars extra, what a means to effectively use Earth-launched propellant could do for far less money, far less risk, and far less time.

Depends on how much propellant is used.

As mentioned earlier, earthly propellant must be launched with disposable vehicles. Enough propellant deliveries with reusable vehicles might pay for a lunar base.

There is already considerable propellant burned in earth orbit. To get a com sat from LEO to GEO takes more than the sat's dry mass in propellant.

Presently our orbital assets are so hard to reach the paradigm is design, build, launch, discard. With vehicles that routinely move between orbits, modular, upgradeable sats amenable to maintenance might become cost effective.

I read an orbiter thread about cleaning up space debris. Some people mentioned nets or aerogel bricks. Debris hit an aerogel brick at 3 or 4 km/s will just make more debris. To collect debris, a vehicle would need to match velocities with the trash. Which would take lots of propellant.

We don't need it for BEO exploration, it is just a money-trap there. I personally want to see people land on Mars in my lifetime... :dry:

Why on earth do you want to see people land on Mars? Surely you know Zubrin's Mars Direct isn't sustainable. The best outcome I could see for that is a half dozen abandoned Martian habs gathering dust with maybe two, three hundred billion flushed down the toilet. Apollo redux.

Fantasies of colonizing and terraforming Mars are not plausible.

You may save rocket launches from Earth for propellant, but now you have to launch replacement parts... consumables... crews (if your propellant mine has a human presence, which many vehemently suggest),

Not me. See my earlier comments on telerobots.

Already the rocket equation means you could end up producing more propellant to get your propellant somewhere useful, than you would use as a 'product'.

I want to break the exponent in the rocket equation not to save propellant. But to enable smaller, simpler, reusable vehicles.

This is the paradigm I want to leave behind:

 

[T.Neo]

There's estimated to be 600 million tonnes at the north pole in sheets of ice at least two meters thick.

True, this is a relatively small portion of the moon.

But then again, Hawaii and Japan are a small fraction of the Pacific ocean. Should the worth of these islands be disregarded for that reason?

It depends on where on Earth you are, specifically. I'm not going to bother going to Hawaii, it's half a world away and I have what I have right where I am.

Thank you for pointing out the obvious. I will return the favor.

Earth's surface isn't the only realm of economic activity. We have extensive and valuable assets in orbit.

LEO and GEO are not covered with water.

Earth's surface is 9 to 10 km/sec from LEO. Any earthly propellant delivered to GEO must be delivered with multi-stage expendables.

On the other hand, lunar propellant is 2.5 km/s from EML1. And EML1 is .7 km/s from LEO (with aerobraking)

Click this bar to view the full image.


Given a 4.5 km/s EML1-LEO round trip and a 5 km/s moon to EML1 round trip, propellant delivery can be accomplished with single stage, reusable vehicles.

I already stated;

Of course, selling it to use as rocket propellant... physics wise, the concept may be sound. The problem is that it isn't only physics, it's logistics, infrastructure, and economics as well.

Physics is not everything.

Also, physics equations can be pretty easy, compared to economics. You can't just bash things into working best by doing physics, and that is where the compromises in the art of good engineering come in.

I'm not talking about manufacturing space ships, or computers on the lunar surface. Or even mining iron or aluminum. I'm talking about splitting ice to make hydrogen and oxygen.

And you suggest that this will not require infrastructure of any kind?

The cost of establishing a lunar propellant mine remains an open question. Rather than use BFRs like Ares or SLS I would go with something like the ULA lunar architecture.

It also remains an open question how much a human presence would be needed. Mining companies such as Rio Tinto are already investing in telerobotics. Any hard to reach and/or dangerous workplace could benefit by advancing the state of art for teleoperated equipment.

The moon is one of the few places where teleoperated mining equipment is remotely plausible. Light lag is less than 3 seconds. And LRO has demonstrated high bandwidth is doable.

Well... at least we agree on BFRs. And from what I've read, the ULA lunar architecture looks pretty good.

But you don't make launch costs go away by abandoning BFRs. You don't make equipment costs for landers and suchlike go away, either.

Teleoperated mining equipment would be a given. The issue is when that mining equipment breaks or when a problem arises that it simply can't fix.

Depends on how much propellant is used.

As mentioned earlier, earthly propellant must be launched with disposable vehicles. Enough propellant deliveries with reusable vehicles might pay for a lunar base with enough propellant demand.

There is already considerable propellant burned in earth orbit. To get a com sat from LEO to GEO takes more than the sat's dry mass in propellant.

Presently our orbital assets are so hard to reach the paradigm is design, build, launch, discard. With vehicles that routinely move between orbits, modular, upgradeable sats amenable to maintenance might become cost effect.

Reusability does not fix everything. At least it has an easier job out in cislunar space, but it still has limitations.

And modern launch vehicles are optimised for being expendable. Expendability is not necessarily a bad thing.

Also, it is not required to use expendable vehicles to reach LEO. The biggest criticism I seem to hear about RLVs is flight-rate. But if you can make a reusable RLV- and I don't think it pays to ignore the possibility- then that is a good thing, of course.

And there's another issue: propellant is intrinsically cheap. It isn't like satellites or space probes or people. The cost of that propellant is under $1-$2 per kilogram. This makes it a perfect payload for vehicles that are optimised for cost at the expense of reliability- if costs are low enough and schedules can work around failures, theory is that you could afford to lose a considerable amount of vehicles and still come out better off.

Also, propellant does not care about high accelerations. It does not care about vibration, or noise. This potentially makes propellant a good payload for solid fueled or pressure fed vehicles.

Of course a space architecture centered around launch vehicles and depots and tugs, does not need the Moon.

Why on earth do you want to see people land on Mars? Surely you know Zubrin's Mars Direct isn't sustainable. The best outcome I could see for that is a half dozen abandoned Martian habs gathering dust with maybe two, three hundred billion flushed down the toilet.

Fantasies of colonizing and terraforming Mars are not plausible.

Why? Because it's cool, of course. This is the primary motivation I have for wanting to see humans on Mars, and I think as little as many other people want to admit it, it is their primary motivation as well.

I know Zubrin's Mars Direct is unsustainable; it relies on a SHLV. But there are other ways, to make a sustainable Mars project. They again do not require the Moon.

My issue with the "use the Moon to get to Mars" idea is that the only thing a lunar program will truely achieve, is stealing funding away from a Mars program, just as STS left no funding behind for the station or BEO programs it was originally meant to support.

Constellation was the very epitome of this eventuality.

Also, just because colonisation and terraforming aren't economically feasible (not by a longshot, the numbers are absolutely painful) does not mean they are not physically and technologically feasible, which they could very well be.

Kind of like mining propellant from the Moon.

Not me. See my earlier comments on telerobots.

What happens when a telerobot breaks? What happens when part of a telerobot breaks?

Now you have to ship a new telerobot to the Moon.

I want to break the exponent in the rocket equation not to save propellant. But to enable smaller, simpler, reusable vehicles.

Reusability does not necessarily solve things. Reusability and a whole lot of other stuff that becomes mandatory in an architecture does not solve things either.

I find it pretty confusing that you suggest "Reusability" and then bypass decades of RLV concepts to suggest the Moon...

Already the requirements on an upper stage are not that different from those on a space tug. Trying to get the upper stage back on the ground is tricky, not impossible but it comes at a cost.

You might want to try disposing of the stage and recovering the engines, since they are expensive and also pretty dense.

First stages can be simpler, more rugged, and heavier, because they are 'discarded' early into the flight. This makes it easier for the stage to survive recovery.

There are many ways to "skin a cat", and an uneconomical Lunar program likely isn't one of them. There are ways that are more direct, less costly, and hold more potential.

If we take a Delta IV Heavy launch as $265 million, and we suggest that the propellant tanker it is carrying costs another $50 million, with a payload (propellant) fraction of 0.9, would have a cost/kg of perhaps $15 300/kg.

For a lunar outpost, producing 150 tons of propellant a year over 20 years to match that cost, the entire program cost would have to be... $46 billion dollars.

Frankly, I think that is optimistic for a lunar program. And I'm not sure about the 150 tons of propellant a year... or even if that fits into the demand that exists in reality. Certainly a good deal of the propellant you produce will be used to ship your product, not be used as the product itself.

And of course, if launch rate goes up (to cart more propellant into LEO), vehicle cost goes down. A period of high launch rates in your lunar propellant factory program will occur while it is being constructed, but afterwards launch rate to the Moon would be relatively low, and you still have to contend with the cost of all the other stuff. And you have to pay for the large number of launch vehicles that you would need to assemble all the required equipment on the Moon.

A Delta IVH launch could probably tend to one or two "space tug" flights to put reasonably sized satellites into GTO.

 

[HopDavid]

I find it pretty confusing that you suggest "Reusability" and then bypass decades of RLV concepts to suggest the Moon...

Already the requirements on an upper stage are not that different from those on a space tug. Trying to get the upper stage back on the ground is tricky, not impossible but it comes at a cost.

You might want to try disposing of the stage and recovering the engines, since they are expensive and also pretty dense.

First stages can be simpler, more rugged, and heavier, because they are 'discarded' early into the flight. This makes it easier for the stage to survive recovery.

I am thinking of three types of vehicles:

The yellow will probably always be multi-stage expendable. Just the 9 to 10 km/s going up mandates expendables. The 8 km/s going down is accomplished by aerobraking, which has a cost. Re-entry mass can include wings, parachutes, ablation shield, etc. Also shedding 8 km/s over an hour's time inflicts terrible abuse. The high temperatures place constraints on the materials used. It also increases possible failure modes and maintenance time.

The red and green vehicles would be lofted once as upper stages. Once up, they would not return to earth's surface.

The red vehicle would move between earth orbits. The green vehicle would move between EML1 and the moon's surface.

Neither the red or green needs the re-entry mass the yellow must have. Neither the red or green have a 17 km/s round trip delta V budget. Rather closer to 5 km/s.

If you wish to argue the shuttle and other efforts have demonstrated these RLVs are impractical, I would reply 17 is not equal to 5.

 

[T.Neo]

The yellow will probably always be multi-stage expendable. Just the 9 to 10 km/s going up mandates expendables. The 8 km/s going down is accomplished by aerobraking, which has a cost. Re-entry mass can include wings, parachutes, ablation shield, etc. Also shedding 8 km/s over an hour's time inflicts terrible abuse. The high temperatures place constraints on the materials used. It also increases possible failure modes and maintenance time.

No, it does not mandate expendables, as much as some might believe. It has just been accomplished by expendable engineering solutions so far.

And aerobraking is not the same as launch. Your structure is heated, but you can handle this. It isn't the same as operating rocket engines, for example.

Also, STS had a really bad, fragile TPS... but you do not need a fragile TPS like that. There are many other ways to tackle the problem, especially as methods and technologies and material sciences have advanced since the 1970s when STS was constructed.

What you're saying is basically this:

Oh woe! A reusable launch vehicle needs to ascend to orbit! It needs rocket engines! And it needs to reenter, it needs a TPS!

To me, it sounds a like:

Oh woe! A steam-driven locomotive will need a furnace! And a boiler! And pistons! It will need to deal with high pressures and temperatures!

All of those concerns for a steam-driven locomotive are valid, as are concerns over the limitations of launch vehicles. However, neither are impossible and can be tackled well providing you engineer things intelligently.

The red and green vehicles would be lofted once as upper stages. Once up, they would not return to earth's surface.

The red vehicle would move between earth orbits. The green vehicle would move between EML1 and the moon's surface.

Neither the red or green needs the re-entry mass the yellow must have. Neither the red or green have a 17 km/s round trip delta V budget. Rather closer to 5 km/s.

Delta V budgets do not directly drive costs.

And the round trip budget isn't 17 km/s for an RLV. You don't have to pay for aerobraking, aerobraking is free.

If you wish to argue the shuttle and other efforts have demonstrated these RLVs are impractical, I would reply 17 is not equal to 5.

Yeah, but 5 km/s also happens to be in the range of the dV requirement of an upper stage.

And aerobraking does not magically add another 7 km/s to your dV budget. :beathead:

Perhaps STS demonstrated that RLVs are impractical. But STS also most definitely demonstrated how you shouldn't try to build an RLV. What was done over the course of the STS program is a learning experience. You can take that knowledge and apply it, and make a better system.

And you totally neglect the gigantic problem of infrastructure on the Moon, and focus on the physics. But like I said, the physics gets overridden.

 

[HopDavid]

No, it does not mandate expendables, as much as some might believe.

Evidence? I'm not taking your word for this.

Delta V budgets do not directly drive costs.

They do set mass fractions, unless you know of a way to circumvent the rocket equation

(propellant mass + dry mass) / (dry mass) = e^{dV / Vexhaust}

And when delta V budget compels an impossibly small dry mass fraction, you're required to throw away dry mass along the way.

And the round trip budget isn't 17 km/s for an RLV.

9 to 10 km/s going up. And 8 km/s must be shed on the way down. Going up is achieved with propellant, going down by aerobraking.

You don't have to pay for aerobraking, aerobraking is free.

Absolutely false. Wings are not free. Ablation shields are not free. The constraints from high temperatures and abuse boost the price.

Yeah, but 5 km/s also happens to be in the range of the dV requirement of an upper stage.

Indeed. So it's been demonstrated 5 km/s can be achieved with a single stage.

Obviously the lower stages delivering the tug to orbit would be a multi stage expendable. But I'm not talking the vehicle that delivers the tug to orbit. I talking about the tug that will remain in orbit.

And aerobraking does not magically add another 7 km/s to your dV budget. :beathead:

You evidently don't know what dV means. Delta V is change in velocity.

Some change in velocity is achieved with propellant. Some with aerobraking.

If you don't change your velocity by 8 km/s, your return to earth will not go well.

Perhaps STS demonstrated that RLVs are impractical.

Earth to LEO and back isn't the only possible vehicle.

A vehicle for travel between earth orbits would only need to be launched from earth's surface once. It would not return to earth's surface. This point seems to be escaping you.

The requirements for a vehicle traveling between earth orbits are much less than a vehicle that must lift off from earth's surface and achieve LEO.

And you totally neglect the gigantic problem of infrastructure on the Moon, and focus on the physics. But like I said, the physics gets overridden.

You have said a lot of things that are questionable. Addressing them all at once is something I don't have time for at the moment.

For now I would like you to acknowledge some differences between an earth to orbit vehicle and an inter-orbital vehicle.

1) An inter-orbital vehicle does not need propellent to achieve 9 or 10 km/s
2) An inter-orbital vehicle does not have the endure the abuse of re-entry.

 

[T.Neo]

Evidence? I'm not taking your word for this.

Evidence to the contrary?

And don't say "all vehicles to date have been expendable and the Shuttle was a complete failure", because I can also say "there is no lunar architecture and satellites get to GEO just fine".

They do set mass fractions, unless you know of a way to circumvent the rocket equation

(propellant mass + dry mass) / (dry mass) = edV / Vexhaust

And when delta V budget compels an impossibly small dry mass fraction, you're required to throw away dry mass along the way.

Mass fractions do not directly drive costs.

"Throw away dry mass" does not necessarily mean "destroy forever", and some would disagree that the mass fractions needed for an SSTO are 'impossibly small'.

SSTO is more of a practicality issue than anything else. The only thing that makes it justifiable is reusability, and you can't even be sure of that...

9 to 10 km/s going up. And 8 km/s must be shed on the way down. Going up is achieved with propellant, going down by aerobraking.

And aerobraking is free.

If you don't believe me, crunch the numbers for a vehicle that does full propulsive descent (in other words, really does have a dV requirement around ~17 km/s).

Absolutely false. Wings are not free. Ablation shields are not free. The constraints from high temperatures and abuse boost the price.

Yes, they are. When you compare them with propellant to go all the way back down.

Now, the total velocity change may be in the region you are talking about... but as a guy who wrestles the rocket equation for fun, having to carry wings and a TPS to orbit is not the same as having to do a propulsive descent. Please don't equate the two.

And who said anything about ablative thermal protection systems? There are multiple vehicles that have returned from orbit (one over a hundred times over 30 years) using non-ablative heatshields.

Indeed. So it's been demonstrated 5 km/s can be achieved with a single stage.

Obviously the lower stages delivering the tug to orbit would be a multi stage expendable. But I'm not talking the vehicle that delivers the tug to orbit. I talking about the tug that will remain in orbit.

Actually, the Centaur space tug is delivered by a vehicle with only a single stage (plus boosters if you count all of the Dial-a-rocket variants of Atlas V). It can make its way to orbit all on its own, it has the dV capability.

You evidently don't know what dV means. Delta V is change in velocity.

Some change in velocity is achieved with propellant. Some with aerobraking.

If you don't change your velocity by 8 km/s, your return to earth will not go well.

The difference is that a dV of 8 km/s done with propellant is extremely painful, and 8 km/s done with air and a TPS is far less so.

If you want to return to Earth, you will change your velocity by some ~8 km/s however you do it. The trick is to change your velocity by 8 km/s and have an intact vehicle afterwards.

Earth to LEO and back isn't the only possible vehicle.

A vehicle for travel between earth orbits would only need to be launched from earth's surface once. It would not return to earth's surface. This point seems to be escaping you.

The requirements for a vehicle traveling between earth orbits are much less than a vehicle that must lift off from earth's surface and achieve LEO.

No, the point does not escape me. The problem is, the problems don't escape me either. That's why I don't like the idea.

A vehicle acting as the second stage of a launch vehicle will be under much the same forces as a space tug. In fact they could become one and the same thing.

You have said a lot of things that are questionable. Addressing them all at once is something I don't have time for at the moment.

What have I said that is questionable? That there are multiple ways to do things in engineering and they all have their benefits and disadvantages? Or that I said that you don't necessarily have to do things the way you suggest things are done with the disadvantages that you insist are so damaging?

For now I would like you to acknowledge some differences between an earth to orbit vehicle and an inter-orbital vehicle.

1) An inter-orbital vehicle does not need propellent to achieve 9 or 10 km/s
2) An inter-orbital vehicle does not have the endure the abuse of re-entry.

I don't appreciate the fact that you keep on dodging the issue of the nonexistant lunar architecture. The big issue I see here with the sort of "Lunar resource paradigm" is that the lunar architecture is just supposed to appear magically and operate magically. No attention (or poor attention) is paid to the difficulties that such an idea faces.

A second or first stage don't need to have a 9-10 km/s dV capability either.

Have you ever done any foray into the actual engineering difficulties of deorbiting a launch vehicle from orbit and landing it intact? Have you done any engineering work on the engineering and mechanical constraints on the structure and components? Have you ever tried to find innovative ways of creating good solutions in that field?

 

[HopDavid]

And aerobraking is free.

If you don't believe me, crunch the numbers for a vehicle that does full propulsive descent (in other words, really does have a dV requirement around ~17 km/s).

I will try to explain this as simply as possible.

To review, the 3 sorts of vehicles I imagine.

Yellow:

Going up: 9 to 10 km/s
Going down: .1 km/sec
Reentry abuse: Extreme. Typically 8 km/s is shed over an hour's time.

Red:

Going up: 3.8 km/s
Going down: .7 km/sec
Reentry abuse: Mild. 3.1 km/s suffices to circularize in LEO. And this 3.1 km/s can be accomplished over several perigee drag passes through the upper atmosphere.

Green:

Going up: 2.5 km/s
Going down: 2.5 km/sec
Reentry abuse: None.

It's my opinion the red and green could be small, economical, reusable vehicles. The yellow vehicle faces a completely different set of constraints and requirements. In my opinion this vehicle can't be small, economical and reusable.

Thus it would cost less to transport lunar propellant than earth propellant.

You correctly argue the mass penalty for the yellow's re-entry is insignificant compared to what an 8 km/s propellant mass penalty would be. Then you go on to say the 8 km/s is free. Which is utter bull. Besides the non-zero mass to help with re-entry, the atmospheric drag inflicts extreme temperatures. If re-entry weren't a problem, R.G. Clark's arguments for a SSTO RLV wouldn't be quite so ridiculous.

But for the sake of argument, let's say the yellow's 8 km/s re-entry can be disregarded. The round trip delta V for the blue and red are still less than half of the delta V for yellow's trip up.

I will now address other arguments you've made.

---------- Post added at 01:29 PM ---------- Previous post was at 01:28 PM ----------

Of course a space architecture centered around launch vehicles and depots and tugs, does not need the Moon.

Wrong.

LEO is a bad thermal environment for cryogenics. Boil off is a problem.

However, propellant boil-off is mitigated if you have steady throughput.

Lunar launch windows open every two weeks from a given LEO. Steady throughput is possible with a lunar architecture.

Mars launch windows open each 2.14 years. Your propellant depots spend most of their time sitting unused in LEO.

My issue with the "use the Moon to get to Mars" idea

That's certainly not my idea. I see no reason to go to Mars.

is that the only thing a lunar program will truely achieve, is stealing funding away from a Mars program, just as STS left no funding behind for the station or BEO programs it was originally meant to support.

Constellation was the very epitome of this eventuality.

Look at the name of Griffin's rocket: Ares V, straight off the pages of Zubrin's The Case For Mars. That was a Mars rocket.

Same for SLS. A lunar architecture doesn't need 130 tonnes to LEO.

So don't try to pin the HLV pork frenzy on the moon.

That albatross belongs firmly around Zubrin's neck.

Via Constellation and SLS, Mars has sucked the life out of the HSF program. It has also hogged the lions share of robotic missions.

Why? Because Zubrin has sold Mars as the new frontier. It's a frozen wasteland with a 3 millibar CO2 atmosphere. Settlers aren't going to chop down trees to build log cabins and plant corn fields. Any humans there would be living underground in wholly artificial environments, just as they would on asteroids or the moon. Further, settlement of the Americas was aided by trade with Europe. What would Mars export profitably? It has a 5 km/s gravity well to climb. Trip times to earth are more than half a year and constrained to launch windows each 2.14 years. Zubrin's vision is bogus.

Also, just because colonisation and terraforming aren't economically feasible (not by a longshot, the numbers are absolutely painful) does not mean they are not physically and technologically feasible, which they could very well be.

Kind of like mining propellant from the Moon.

Colonizing Mars and mining lunar propellant aren't remotely comparable.

The last: 3 second light lag vs 10-30 minute light lag is the most important, in my opinion. I see improved telerobotics as the only way we'll establish substantial infrastructure on another body. Another advantage for telerobotics: the moon's proximity allows for high bandwidth. LRO achieved 100 Mbps.

And of course, if launch rate goes up (to cart more propellant into LEO), vehicle cost goes down.

High flight rate is everything, in my opinion. It could provide rapid acquisition of experience as well as economies of scale.

Elon Musk is making a boatload of Merlin engines trying to achieve economies of scale. Is it a given he'll sell enough launches to stay profitable? Far from it, in my opinion. Have you followed the tug of war between players like Shelby and Rohrabacher?

The ULA lunar architecture calls for many deliveries of propellant to LEO and then EML2. Until lunar propellant comes online, this would be a great market for SpaceX, Blue Origin, et al.

Given rarity of launch windows, I see HLVs as the best way to reach Mars or NEOs. I can't see a mars architecture providing a high flight rate for small and medium lift vehicles.

So I see Moon vs Mars as Commercial space and propellant depots vs HLV pork frenzy. One has the possibility of changing paradigms. The other employs a lot of people to do extremely expensive flags and footprints publicity stunts.

Either option would be expensive. I would go for the moon. But a flag and footprints on an NEO? A few abandoned habs on Mars? Better to cancel HSF and save the money.

---------- Post added at 02:45 PM ---------- Previous post was at 01:29 PM ----------

To who are you going to sell this water? Earth is covered with it, so to sell it to us would be like "selling coal to Newcastle".

Nor have I suggested this. Those are your words which you have failed to put in my mouth.

IAnd you suggest that this will not require infrastructure of any kind?

I have suggested no such thing. Again, your words, not mine.

I believe propellant depots and infrastructure for a lunar propellant mine would cost about the same as a sortie mission to an asteroid or a brief stay on Mars: around 100 billion. I would guess any of these three would take 15 to 20 years. So 5 to 7 billion a year.

What you're saying is basically this:

If you want to repeat what I say along with quote tags, please use my actual words.

Stop trying to volunteer arguments for me. More often than not, they are straw men.

 

[T.Neo]

It's my opinion the red and green could be small, economical, reusable vehicles. The yellow vehicle faces a completely different set of constraints and requirements. In my opinion this vehicle can't be small, economical and reusable.

Thus it would cost less to transport lunar propellant than earth propellant.

You correctly argue the mass penalty for the yellow's re-entry is insignificant compared to what an 8 km/s propellant mass penalty would be. Then you go on to say the 8 km/s is free. Which is utter bull. Besides the non-zero mass to help with re-entry, the atmospheric drag inflicts extreme temperatures. If re-entry weren't a problem, R.G. Clark's arguments for a SSTO RLV wouldn't be quite so ridiculous.

But for the sake of argument, let's say the yellow's 8 km/s re-entry can be disregarded. The round trip delta V for the blue and red are still less than half of the delta V for yellow's trip up.

Ok, let's crunch some numbers here. Let's say we've got a vehicle with a mass ratio of 11.25 and an ISP of 440 seconds.

Now let's say that th effective payload mass is doubled by adding a recovery system. In this case, the wet mass goes up by 1.25 times.

Now let's change the dV from ~10.4 km/s, to 18.4 km/s. The wet mass goes up a whole 6.4 times, and that is with the dry mass magically staying the same. Factoring in the ballooning of mass that would occur, it could be an increase in wet mass of over 40 or 50 times at least.

Aerobraking is free, In the same was that a desert on a moonless night with a car's headlights shining at you from 20 kilometers away is pitch black, compared to the same desert with a tactical nuclear device detonating 20 kilometers away.

A recovery system massing 20, or 30, or even 50 tons is nowhere close to a recovery system (propellant and tankage) weighing tens of thousands of tons.

Reentry isn't the biggest problem with RGClark's SSTO RLV suggestions. My biggest problem with what he suggests is the fact that he underestimates the engineering difficulty and cost of the modifications he suggests, as well as the addition of reusability. And the fact that he believes that you can fill just about any volume on a spacecraft with propellant.

Otherwise, stuff like hooking up a Falcon 9 first stage to NK-33s instead of Merlins more-or-less makes physical, if not practical or economic sense. And while reentry is a whole new problem, it is not one that can be solved by "I insist that this is impossible".

Also, one thing you forget about your "economical, reusable vehicles" is that they will have to exist and operate for years, even decades- their entire lifespan- in the wilderness. While the recovery cycle of a launch vehicle might be tougher, on the ground it has access to a huge infrastructure and complements of qualified technicians that can use extensive facilities for refurbishment, repair, and fault-checking.

The fact that your "economic" vehicles will have to operate for years without considerable (or any) maintainance, will drive up their cost considerably.

Wrong.

LEO is a bad thermal environment for cryogenics. Boil off is a problem.

However, propellant boil-off is mitigated if you have steady throughput.

Lunar launch windows open every two weeks from a given LEO. Steady throughput is possible with a lunar architecture.

Mars launch windows open each 2.14 years. Your propellant depots spend most of their time sitting in LEO.

Why is it wrong? Because you demand it to be so?

Cryogenics can cope in LEO, even with boiloff. You can mitigate boiloff and have reserve margins. You don't plan to put cryogenics into LEO for years, you structure things so that they are used within a certain time of launch and you have a reserve margin to cope with delays. You don't need the Moon.

Launch windows from a point on Earth to a depot in LEO occur more-or-less on the order of days. In the time it would take you to wait for the next window from the Moon you would have multiple launch oppurtunities.

If boiloff is that much of a problem you might want to consider shipping water to LEO and electrolysing it onsite into its constituent, cryogenic parts.

If you really are worried about propellant boiloff in the lead-up to a Mars mission, you could ship your propellant up from LEO to EML1/2. It'll be more expensive dV wise but it'll save you the immense cost of a lunar infrastructure that doesn't exist.

That's certainly not my idea. I see no reason to go to Mars.

I am disappointed by that kind of attitude. I see many reasons to go to Mars, I just don't see many reasons for it to make sense (yet). Ignoring the possibility totally is not a good thing.

Look at the name of Griffin's rocket: Ares V, straight off the pages of Zubrin's The Case For Mars. That was a Mars rocket.

Same for SLS. A lunar architecture doesn't need 130 tonnes to LEO.

So don't try to pin the HLV pork frenzy on the moon.

That albatross belongs firmly around Zubrin's neck.

I will pin the HLV pork frenzy (partially) on the Moon, because for the past few years all the HLV nonsense that has been flying around has been focused primarily on the Moon.

Ares V was a Moon Rocket, plain and simple. It kept on getting more and more bloated, perhaps in Griffin's idea of eventually needing a supergigantic rocket for Mars, but its use was going to be- even in the optimistic, unrealistic, advertised schedules- a Moon rocket.

You don't need an HLV to lift a Mars mission, as much as some people might believe.

SLS can't be pinned on the Moon, nor can it be pinned on Mars. The reason SLS exists is because politicians have vested interests, plain and simple. If sense prevailed in the US government, we would have no SLS today. NASA is against the SLS, even Obama is or was against SLS... it is being pushed totally, by politicians that would benefit from it politically. And Mike Griffin, who would probably also benefit from it politically (somehow).

Via Constellation and SLS, Mars has sucked the life out of the HSF program. It has also hogged the lions share of robotic missions.

Why? Because Zubrin has sold Mars as the new frontier. It's a frozen wasteland with a 3 millibar CO2 atmosphere. Settlers aren't going to chop down trees to build log cabins and plant corn fields. Any humans there would be living underground in wholly artificial environments, just as they would on asteroids or the moon. Further, settlement of the Americas was aided by trade with Europe. What would Mars export profitably? It has a 5 km/s gravity well to climb. Trip times to earth are more than half a year and constrained to launch windows each 2.14 years. Zubrin's vision is bogus.

Again, please don't try to blame SLS on Mars. There's much reason to be angry with the SLS debacle but 'favourite destinations' in space aren't among them.

And Constellation was not a Mars program. There was no Mars hardware or plans in Constellation at all. Even Ares V does not count, because a heavy rocket will not give you a Mars program, a fact that is completely missed by many. If anything it is a testament to the bad design ethics stemming from Mr Griffin, but that's another story.

Mars was always a "maybe if" "after 2030" with Constellation. There were no concrete Mars plans. The DRMs that were done during the Constellation era and Griffin's tenure were similar to previous DRMs.

The difference of course, is that DRM 3.0 required the launch of six 80 ton vehicles, if I remember correctly. DRM 5.0 required the launch of seven +180 ton Ares Vs.

Constellation's Moon plans would have delayed a mission to Mars by decades and tens of billions of dollars, needlessly. But that wasn't the real problem with CxP... that problem was that Mike Griffin's approach to engineering and spaceflight was and is "I reject your reality and substitute my own."

I agree with you that Zubrin is... enthusiastic. However, Mars has a lot to offer and can't be ignored. If there is a frontier in space... it is Mars. Granted, that isn't saying much.

Colonizing Mars and mining lunar propellant aren't remotely comparable.

No, they are not. A lunar propellant mine has to be profitable, which it will not be, and a Mars mission has to be successful, which it very well can be if everything is done correctly.

In your comparison list, I see several cases of "this is supposed to happen this way/be an insurmountable problem because I demand it to".

And where have I suggested colonising Mars? I have actually pointed out why Mars colonisation doesn't make sense multiple times, much to the chagrin of other Orbinauts. But "going to Mars" is not synonymous with "colonisation". Antarctica has not been settled, but that does not mean that there are no research bases there whatsoever.

The last: 3 second light lag vs 10-30 minute light lag is the most important, in my opinion. I see improved telerobotics as the only way we'll establish substantial infrastructure on another body. Another advantage for telerobotics: the moon's proximity allows for high bandwidth. LRO achieved 100 Mbps.

I do not. Partially because telerobotics are not essential to develop infrastructure and partially because they simply cannot develop "substantial" infrastructure, at least not easily (or cheaply).

It's possible at the Moon because we've tried it there, and therefore impossible anywhere else? I think it's high time we experimented with high bandwidth communications over further distances.

High flight rate is everything, in my opinion. It could provide rapid acquisition of experience as well as economies of scale.

Yes! Exactly.

Elon Musk is making a boatload of Merlin engines trying to achieve economies of scale. Is it a given he'll sell enough launches to stay profitable? Far from it, in my opinion. Have you followed the tug of war between players like Shelby and Rohrabacher?

Yes, I have...

But SpaceX has other problems. They haven't achieved a high flight rate or switched over from what is essentially testing, to operational routine. Unless people like Shelby become absolutely evil opponents of anything that might make sense, these are (at least for me) far more pressing concerns about SpaceX's viability.

The ULA lunar architecture calls for many deliveries of propellant to LEO and then EML2. Until lunar propellant comes online, this would be a great market for SpaceX, Blue Origin, et al.

Yes, and providing your lunar infrastructure magically works... that market would then crash. I don't think that would be particularly healthy.

Given rarity of launch windows, I see HLVs as the best way to reach Mars or NEOs.

:facepalm:

So I see Moon vs Mars as Commercial space and propellant depots vs HLV pork frenzy. One has the possibility of changing paradigms. The other employs a lot of people to do extremely expensive flags and footprints publicity stunts.

:facepalm:

It doesn't work that way. An HLV, especially if launched every 2 years or so, is massively expensive and unsustainable.

You launch your smaller vehicles in the lead-up to a launch window. Launch windows don't suddenly change on you and mess your plans up. Technical problems are more of a worry and they are more of a worry with an HLV.

Simply put, an HLV does not make sense at all, unless the launch market makes it viable. Currently such a market does not exist and it likely will not for some time. It is far better to utilise the existing market.

Even if you want flags and footprints, an HLV has a pretty low chance of getting that objective done.

BEO exploration doesn't have to mean pork frenzy. The pork frenzy stifles BEO exploration.

Commercial does not mean lunar infrastructure.

Commercial is not anti-HLV, there are multiple commercial ideas/proposals for superheavy vehicles, the market just does not exist for them.

Either option would be expensive. I would go for the moon. But a flag and footprints on an NEO? A few abandoned habs on Mars? Better to cancel HSF and save the money.

An NEO mission doesn't have to be flags and footprints and a Mars base does not have to be abandoned. Don't insist that they would be.

The thing is that exploration and research does not have to be profitable. A lunar infrastructure does, if it doesn't beat propellant launched from Earth, it loses. But on the other hand, a lunar infrastructure is pretty useless for research.

I would go for the research and exploration. That would mean going to the Moon, but only in tests- it would be a lot like the learning done in LEO with the Gemini missions. NASA didn't build a space station there. It did not need to, it would have only stifled the goal, which was the Moon.

The thing is that the required paradigm shift needed for BEO exploration is useful in other areas (profitable areas- satellite launching and soforth). The required paradigm shift isn't on the Moon, it's on and around Earth. The Moon is just a dusty space-trap.

 

[RisingFury]

Is glass fibre not good enough? Is it too dense? Too weak? Too floppy? Considering the number of fiberglass objects made today, wouldn't wrapping glass fibre composite around a mandrell be cheaper than forming and welding together a series of metal panels?

Fiberglass, kevlar, carbon fiber and other fabrics are held together by a resin that doesn't react well to high and low temperatures. At low temperatures it shatters easily and at high temperatures it melts. Not ideal if you want your spacecraft to stay together.

 

[HopDavid]

Ok, let's crunch some numbers here. Let's say we've got a vehicle with a mass ratio of 11.25 and an ISP of 440 seconds.

Now let's say that th effective payload mass is doubled by adding a recovery system. In this case, the wet mass goes up by 1.25 times.

Now let's change the dV from ~10.4 km/s, to 18.4 km/s. The wet mass goes up a whole 6.4 times, and that is with the dry mass magically staying the same. Factoring in the ballooning of mass that would occur, it could be an increase in wet mass of over 40 or 50 times at least.

And that supposedly demonstrates 8 km/s via aerobraking is inconsequential.

Tell that to the crew of Space Shuttle Columbia. Tell Linda Ham, “That silly little 8 km/s was nothing! If that 8 km/s were accomplished with propellant, that would’ve boosted ship mass 7 fold!”

Tell the families of Colonel Husband, Cammander McCool, Commander Anderson, Colonel Ramon, specialist Chawla, Captain Brown and Laurel Clark “e^10.4/4.3 is 11.25. But e^18.4/4.3 is 72.17. TPS is of no concern!”

In NSF's RLV Technical Issues Thread ,aerospace engineer Danny Dot talked about available materials that could withstand temperatures at the wing edge. One of his comments: “And on NASA buying off on a broken design, it took me over a year and 7 dead astronauts to convince NASA it was a bad idea to build a spaceship out of a material softer than chalk.”

Danny Dot also wrote “Shuttle does NOT bring its huge tanks back to Earth.† This makes shuttle possible.† As soon as you want to bring the tank back home (wings, wheels, TPS, etc.), the design breaks.”

Danny Dot regards TPS and other re-entry provisions as a concern. You claim they’re trivial. Perhaps you are a more competent aerospace engineer than he. But that remains to be demonstrated.

For the moment your argument seems to be exp(8/4.3) = 6.5. This does nothing to demonstrate re-entry is trivial. It only demonstrates that you Just. Don’t. Get It. :facepalm:

And while reentry is a whole new problem, it is not one that can be solved by "I insist that this is impossible".

No-one is insisting it's impossible. I do insist an 8 km/s re-entry adds to difficulty and expense.

The 10 km/s ascent also adds to difficulty and expense.

Also, one thing you forget about your "economical, reusable vehicles" is that they will have to exist and operate for years, even decades- their entire lifespan- in the wilderness. While the recovery cycle of a launch vehicle might be tougher, on the ground it has access to a huge infrastructure and complements of qualified technicians that can use extensive facilities for refurbishment, repair, and fault-checking.

The fact that your "economic" vehicles will have to operate for years without considerable (or any) maintainance, will drive up their cost considerably.

That is a valid criticism. Having a pressurized hangar they could be serviced in would be a very ambitious project.

A dextrous telerobot with binocular vision, movable head, torso and arms might help.

Why is it wrong?

I'm going by what Zegler, Kutter, Barr, Goff, Bienhoff, Chandler and Marchetta write.

Cryogenics can cope in LEO, even with boiloff. You can mitigate boiloff and have reserve margins.

From page 5 of this pdf:

"The higher heating rate in LEO motivates us to move propellants onward as rapidly as possible to the better thermal storage conditions at L2. It is a very basic “use it or lose it” proposition. The capacity of the LEO depot drives us to execute a propellant transfer to L2 roughly once every other month."

Also page 13 of this pdf:

"EML-1 or -2 depots are in a much more benign thermal environment, with very low boil-off levels. This leads to the conclusion that the best way to use a depot system like this is to forward propellants on from the LEO depot to the EML-1 or -2 depot as quickly as possible. The higher the tempo of flights beyond LEO, LEO, the lower the percentage of propellants lost to boil-off in LEO."

Both these papers mention using boil off for station keeping. The also both advocate high throughput to EML2, a more benign thermal environment.

Why should I ignore what these ULA guys write? Because you demand that I recognize T.Neo as the first and foremost authority on propellant depots?

You don't plan to put cryogenics into LEO for years, you structure things so that they are used within a certain time of launch and you have a reserve margin to cope with delays.

If you're send all this stuff to LEO just prior to the launch, better to just send up EDS stages.

If you really are worried about propellant boiloff in the lead-up to a Mars mission, you could ship your propellant up from LEO to EML1/2. It'll be more expensive dV wise but it'll save you the immense cost of a lunar infrastructure that doesn't exist.

So you recommend doing a 3.8 km/s burn to reach EML2 when 3.6 suffices for TMI?

I am disappointed by that kind of attitude. I see many reasons to go to Mars, I just don't see many reasons for it to make sense (yet). Ignoring the possibility totally is not a good thing.

I'm all for exploration. But not 100 billion to establish a few temporary Martian habs. Better investment is robotic probes to the Europa or the lunar poles. Or a sustained human presence on the moon (that human space flight goal is actually doable.)

IAres V was a Moon Rocket, plain and simple.

According to Astronautix, four launches of the Ares V would assemble the Mars spacecraft in low earth orbit.

True, Ares rockets were planned for delivery to I.S.S. and the Moon. But that is like using a massive freight train to deliver pizza from the corner Dominoe's to your apartment. While they cited transportation to I.S.S. and the moon as one of the motivations, that obviously wasn’t the ultimate goal they had in mind.

You don't need an HLV to lift a Mars mission, as much as some people might believe.

Do tell. I've read about Mars Direct and Mars Semi Direct. Tell me about the T.Neo architecture.

And Constellation was not a Mars program. There was no Mars hardware or plans in Constellation at all.

And Bushes original Vision for Space Exploration called for learning how to use lunar resources and learn how to live on the moon. So far as I know, Constellation didn't have this hardware either.

Even Ares V does not count, because a heavy rocket will not give you a Mars program, a fact that is completely missed by many.

A heavy rocket will not give you a Moon program, a fact that is completely missed by you.

It's possible at the Moon because we've tried it there, and therefore impossible anywhere else?

Signal strength falls with inverse square of distance. As signal falls, signal to noise ratio falls. Thus high bandwidth is more doable for near locations.

Yes, and providing your lunar infrastructure magically works... that market would then crash.

It would take ten or fifteen years for lunar propellant to come online. A ten or fifteen year market would give New Space a chance to achieve ROI and economies of scale. It could get them over the hump of recouping their design and set up expenses.

It doesn't work that way. An HLV, especially if launched every 2 years or so, is massively expensive and unsustainable.

Agreed.

So instead of a few big rockets you suggest a flurry of small rockets launched right around the biannual launch window? This presents its own set of challenges. Please forgive me that I'm not familiar with the T.Neo Mars architecture.

And this still doesn’t give a steady flight rate during the two year lulls.

The thing is that exploration and research does not have to be profitable. A lunar infrastructure does, if it doesn't beat propellant launched from Earth, it loses. But on the other hand, a lunar infrastructure is pretty useless for research.

I disagree. Prospector rovers able to assess ore bodies could also return scientific data.

Infra structure able to mine propellant would also be able to build radiation shelters, extract water for drinking. The local propellant would make it easier for humans to land as well leave. In other words, a robotic presence would make an extended human presence more plausible. And human mining geologists at the site could also do science.

And the lunar poles are scientifically interesting. They are some of the strangest locations in the solar system.

Without ISRU, robots, and a human presence, much less science would be done.

That would mean going to the Moon, but only in tests-

In other words, extremely brief sortie missions. Flags and footprints Apollo redux. And you say these would accomplish more science than an extended stay?

The Moon is just a dusty space-trap.

We know very little about the moon. It is an interesting target in it's own right. If you're using science as a reason for spending 100 billion on Mars, the moon deserves no less.

Given the difference between Mars and Lunar launch windows, delta V, trip times, bandwidth, light lag, etc., a 100 billion would do a lot more science on the moon than it would on Mars.

 

[T.Neo]

And that supposedly demonstrates 8 km/s via aerobraking is inconsequential.

Tell that to the crew of Space Shuttle Columbia. Tell Linda Ham, “That silly little 8 km/s was nothing! If that 8 km/s were accomplished with propellant, that would’ve boosted ship mass 7 fold!”

Tell the families of Colonel Husband, Cammander McCool, Commander Anderson, Colonel Ramon, specialist Chawla, Captain Brown and Laurel Clark “e10.4/4.3 is 11.25. But e18.4/4.3 is 72.17. TPS is of no concern!”

:facepalm:

Please do not bring the death of people due to an accident caused by a failure in a specific system into this, and then complain that it is caused by reentry.

When people ignore the reasons for failure, it severely annoys me.

In NSF's RLV Technical Issues Thread ,aerospace engineer Danny Dot talked about available materials that could withstand temperatures at the wing edge. One of his comments: “And on NASA buying off on a broken design, it took me over a year and 7 dead astronauts to convince NASA it was a bad idea to build a spaceship out of a material softer than chalk.”

Woah, I didn't know the RCC panels were softer than chalk. They're pretty brittle, sure... but that doesn't stop people from making rocket nozzles and brake pads from RCC.

Unless you mean the silica tiles, in which case... maybe. But they were not the cause of the Columbia accident, nor are they the only solution to shielding a spacecraft from the temperatures of reentry.

Danny Dot also wrote “Shuttle does NOT bring its huge tanks back to Earth.† This makes shuttle possible.† As soon as you want to bring the tank back home (wings, wheels, TPS, etc.), the design breaks.”

Er... no.

A larger surface area for your mass means lower heating. Lower heating means a less intensive TPS.

This is why Skylon gets away with using ceramic plates as its TPS over most of its surface (it only needs active cooling because of something about shockwaves from the engine nacelles).

Maybe the design always breaks in Mr. Dot's world where he refuses to try to fix the problem.

Trying to reuse the ET might bring new problems in to the system, but they need not make it impossible.

Danny Dot regards TPS and other re-entry provisions as a concern. You claim they’re trivial. Perhaps you are a more competent aerospace engineer than he. But that remains to be demonstrated.

Well, I don't know what your qualifications are, but speaking as a complete amateur I have an overwhelming feeling that I'd make a better aerospace engineer than you would.

I too understand the concern of TPS and recovery provisions. My point is that they are trivial compared to trying to design a vehicle to perform fully powered descent. There is a big difference between aerobraking and using your propulsion system to change your velocity, and they should not be compared.

No-one is insisting it's impossible. I do insist an 8 km/s re-entry adds to difficulty and expense.

The 10 km/s ascent also adds to difficulty and expense.

Yes, and? You can't magically get away with difficulty and expense with a difficult and expensive lunar propellant production facility (that also does not exist).

That is a valid criticism. Having a pressurized hangar they could be serviced in would be a very ambitious project.

A dextrous telerobot with binocular vision, movable head, torso and arms might help.

:facepalm:

You try to service a spacecraft from 300 000 km away using a teleoperated robot, working in the wilderness with limited capabilities.

The teleoperated robot, the stuff it has to work with (that now has to withstand years/decades in the wilderness environment), the training for the person to operate it, and the extra time needed to operate it (since you take a performance hit when you do stuff like this) will all cost money.

Also, "pressurised space hangar"? What is this, Star Trek? :dry:

I'm going by what Zegler, Kutter, Barr, Goff, Bienhoff, Chandler and Marchetta write.

And what makes these people so important now, the fact that their names are mildly unusual?

From page 5 of this pdf:

"The higher heating rate in LEO motivates us to move propellants onward as rapidly as possible to the better thermal storage conditions at L2. It is a very basic “use it or lose it” proposition. The capacity of the LEO depot drives us to execute a propellant transfer to L2 roughly once every other month."

Also page 13 of this pdf:

"EML-1 or -2 depots are in a much more benign thermal environment, with very low boil-off levels. This leads to the conclusion that the best way to use a depot system like this is to forward propellants on from the LEO depot to the EML-1 or -2 depot as quickly as possible. The higher the tempo of flights beyond LEO, LEO, the lower the percentage of propellants lost to boil-off in LEO."

Both these papers mention using boil off for station keeping. The also both advocate high throughput to EML2, a more benign thermal environment.

Why should I ignore what these ULA guys write? Because you demand that I recognize T.Neo as the first and foremost authority on propellant depots?

Because you'll waste more propellant shipping that propellant to EML2 from LEO, and you'll waste more money trying to mine that propellant from the Moon.

However, for a BEO mission things might be different, since you will have to boost that hardware/propellant to a similar dV anyway, and dV from EML2 to various locations is (AFAIK) relatively low. This means you could fully reap the benefits of low boiloff conditions during the build-up to a Mars mission.

But it depends on several factors, including all-up spacecraft mass (including things like habitats).

If you're send all this stuff to LEO just prior to the launch, better to just send up EDS stages.

EDS stages filled with propellant, sounds like a fair idea to me.

So you recommend doing a 3.8 km/s burn to reach EML2 when 3.6 suffices for TMI?

Do you really want to spend, what is it? 6 months? 8 months?

When you're going for Mars you don't really want to be going on the bare minimum delta V, and the bare maximum transit time...

I'm all for exploration. But not 100 billion to establish a few temporary Martian habs. Better investment is robotic probes to the Europa or the lunar poles. Or a sustained human presence on the moon (that human space flight goal is actually doable.)

Why sustained human presence on the Moon? What is that going to do for you? The Moon is even more of an unlivable hyperdesert than Mars.

And stop insisting that habitats on Mars would be temporary. They don't have to be.

According to Astronautix, four launches of the Ares V would assemble the Mars spacecraft in low earth orbit.

True, Ares rockets were planned for delivery to I.S.S. and the Moon. But that is like using a massive freight train to deliver pizza from the corner Dominoe's to your apartment. While they cited transportation to I.S.S. and the moon as one of the motivations, that obviously wasn’t the ultimate goal they had in mind.

:facepalm:

Just because Ares could lift a Mars mission does not mean that was its main goal. Also, I don't think I've once seen a proposal to use Ares V to service the ISS. That was (at least originally) the job of Ares I/Orion. Ares V was the moon rocket.

DRM 5.0 had seven, not four Ares V launches. And the Delta IV Heavy could launch a Mars mission in some ~20 launches, doesn't mean it's a Mars rocket.

Do tell. I've read about Mars Direct and Mars Semi Direct. Tell me about the T.Neo architecture.

Please do not imply that I am being so heavily pretentious, that I am advocating my own pet Mars architecture. I am not.

Just because Zubrin says you need an HLV, doesn't mean you do. I suggest you look at the Mars for Less concept developed by Grant Bonin.

And Bushes original Vision for Space Exploration called for learning how to use lunar resources and learn how to live on the moon. So far as I know, Constellation didn't have this hardware either.

It had the lander, it had the rover. It had no Mars hardware whatsoever.

It was a lunar program, plain and simple.

A heavy rocket will not give you a Moon program, a fact that is completely missed by you.

No, it is not completely missed by me. Of course, Ares V was to work in tandem with Altair. Altair existed, but no Mars lander existed. No transit habitat existed. There was no push to find solutions to the unsolved problems of Mars exploration.

Signal strength falls with inverse square of distance. As signal falls, signal to noise ratio falls. Thus high bandwidth is more doable for near locations.

Perhaps, but it doesn't mean that it is impossible further out.

So instead of a few big rockets you suggest a flurry of small rockets launched right around the biannual launch window? This presents its own set of challenges. Please forgive me that I'm not familiar with the T.Neo Mars architecture.

And this still doesn’t give a steady flight rate during the two year lulls.

It will reduce launch costs.

Also, I never said all the vehicles would be launched in... I dunno, the last two weeks before the launch window. You would obviously average everything out to get a steady flight rate.

I disagree. Prospector rovers able to assess ore bodies could also return scientific data

Ore?

There are no resources on the Moon that you could prospect for that would be profitable.

Infra structure able to mine propellant would also be able to build radiation shelters, extract water for drinking. The local propellant would make it easier for humans to land as well leave. In other words, a robotic presence would make an extended human presence more plausible. And human mining geologists at the site could also do science.

And the lunar poles are scientifically interesting. They are some of the strangest locations in the solar system.

Without ISRU, robots, and a human presence, much less science would be done.

At the risk of disappointing lunar science fundies, Mars is far more scientifically interesting than the Moon. Far more so. If you deny it, I think you just haven't researched Mars enough.

There is so much we can learn from Mars. Stuff about planetary evolution... how things interact in that different environment... past existence of water, environmental changes... even things that could affect our knowledge of how life formed and how it could potentially arise elsewhere (which is, of course, a Very Big Question).

As much as you may say that the polar craters on the Moon are "some of the strangest locations in the solar system", it won't take away the fact that Mars is the ultimate scientific goal.

And there is another issue: if you can do Mars, you can do the Moon. But if you can do only the Moon, chances are very good that you won't be able to do Mars. Insisting that lunar science is so extremely important is robbing science of the ultimate goal of Mars.

Everything else should be a secondary goal. Science on the Moon should be a secondary goal only, even if lunar flights precede Mars exploration chronologically. By pushing capabilities towards Mars, you will not only reach your major goal, but create the "spin off" capability to reach a number of other destinations.

In other words, extremely brief sortie missions. Flags and footprints Apollo redux. And you say these would accomplish more science than an extended stay?

No, actually. I said absolutely nothing at all about "brief sortie missions" that would be a "Flags and footprints Apollo redux".

Lunar test missions can help us understand how astronauts can operate on the surface of a planetary body after an extended stay in space (simulated trip to Mars), and also give the benefit of being able to do lunar surface science.

Such a mission would also be anything but brief, or "flags and footprints".

It would actually be very daring. Daring, in an effort to make a Mars mission less so.

We know very little about the moon. It is an interesting target in it's own right. If you're using science as a reason for spending 100 billion on Mars, the moon deserves no less.

We know more about the Moon than we do Mars, and there's so much more to learn about Mars. I'm not nearly denying that the Moon is scientifically interesting- which it is- but it does deserve less than Mars, and it most definitely does not deserve to delay or stifle Mars exploration.

Given the difference between Mars and Lunar launch windows, delta V, trip times, bandwidth, light lag, etc., a 100 billion would do a lot more science on the moon than it would on Mars.

I severely doubt that. How do you measure "doing science"? How do you measure scientific return? How do you put a price on science?

 

[Urwumpe]

Just to make sure: I thanked for being against the abuse of dead astronauts.

Say no to necropolitics.

But seriously: Such "I will answer every single sentence of yours" posts are annoying and give me the impression, you are not interested in understanding what the other wants to express, but rather focus only on what he writes.

If I wouldn't be so damn liberal, I would call for forbidding such nonsense.

Can't you just try to be a bit more civilized? Please?

 

[HopDavid]

:facepalm:

Please do not bring the death of people due to an accident caused by a failure in a specific system into this, and then complain that it is caused by reentry.

The system was designed to deal with re-entry and TPS. That this accident occurred demonstrates re-entry isn't a piece of cake.

This is why Skylon

Skylon's a paper rocket.

Maybe the design always breaks in Mr. Dot's world where he refuses to try to fix the problem.

Not my words. I was citing an actual aerospace engineer. Who has worked for NASA and other aerospace entities. He says TPS is a problem. As an amateur you can deal with this engineering challenge with furious handwaving. In the real world, engineers don't have that option.

My point is that they are trivial compared to trying to design a vehicle to perform fully powered descent.

Since I have never advocated a fully powered descent, you are beating a straw man.

I have said the 8 km/s re-entry presents some serious engineering challenges. You, on the other hand, say that 8 km/s is free.

Yes, and? You can't magically get away with difficulty and expense with a difficult and expensive lunar propellant production facility (that also does not exist).

Once again:

Yellow:

Going up: 9 to 10 km/s
Going down: .1 km/sec
Reentry abuse: Extreme. Typically 8 km/s is shed over an hour's time.

Red:

Going up: 3.8 km/s
Going down: .7 km/sec
Reentry abuse: Mild. 3.1 km/s suffices to circularize in LEO. And this 3.1 km/s can be accomplished over several perigee drag passes through the upper atmosphere.

Green:

Going up: 2.5 km/s
Going down: 2.5 km/sec
Reentry abuse: None.

Granted a lunar propellant mine would be difficult and expensive. However the mine could enable some very useful and economical vehicles.

And what makes these people so important now, the fact that their names are mildly unusual?

If you had followed the links I posted, you would know.

Have you heard of ULA (United Launch Alliance)? Have you heard of Boeing?

Here:

Jonathan A. Goff
Masten Space Systems, Inc., Mojave, CA, 93501
Bernard F. Kutter and Frank Zegler
United Launch Alliance, Littleton, CO, 80127
Dallas Bienhoff
The Boeing Company, Arlington, VA, 22202
Frank Chandler
The Boeing Company, Huntington Beach, CA 92647
Jeffrey Marchetta
The University of Memphis, Memphis, TN, 38152​

(snip irrelevant stuff)

We were talking about LEO propellant depots needing throughput, remember? You say they don't. But the ULA engineers recommend it.

A lunar architecture can provide constant, steady throughput.

Steady throughput is harder when your launch windows occur every 2+ years.

EDS stages filled with propellant, sounds like a fair idea to me.

Which is pretty much the Mars Semi Direct architecture. You're back to big HLVs.

And stop insisting that habitats on Mars would be temporary. They don't have to be.

A permanent Mars presence could easily cost trillions.

A brief stay would cost about 100 billion.

Please do not imply that I am being so heavily pretentious, that I am advocating my own pet Mars architecture. I am not.

Just because Zubrin says you need an HLV, doesn't mean you do. I suggest you look at the Mars for Less concept developed by Grant Bonin.

(Googling...) Ah

"The key issues in using smaller launch systems will always revolve around orbital assembly and wait time, and these issues are certainly not trivial." Just as I have been saying.

And unless you're doing a bunch of launches near the launch window, you're going to have stuff hanging around in LEO for months or even years. During which time you're assembling it. They say it's not an I.S.S., but a prolonged LEO orbital assembly would need some I.S.S. like capabilities.

Also I saw much less detail than other schemes. But still interesting.

It was a lunar program, plain and simple.

Orion Mars Mission (Wikipedia)

"The Orion Mars mission plan for NASA's Constellation program is a manned mission with the intent to land humans on Mars in the 2030s. Originally the ultimate goal of NASA's Apollo Applications Program (AAP) in the 1960s, the Orion Mars Mission would utilize the hardware, primarily the Orion spacecraft (or a variation based on the Orion), and the Ares V cargo-launch vehicle,[53]"

The ultimate goal for the Ares V rocket was Mars.

Ore?

Water ice. Remember?

There are no resources on the Moon that you could prospect for that would be profitable.

That is what I've attempting to discuss since I first posted.

Propellant at various orbital locations would enable travel about our neighborhood in simpler, single-stage, reusable vehicles.

In my opinion, this capability would pay for the cost of setting up a lunar propellant mine.

At the risk of disappointing lunar science fundies, Mars is far more scientifically interesting than the Moon. Far more so. If you deny it, I think you just haven't researched Mars enough.

Or possibly you haven't researched the moon enough.

The cold traps can reach 30 degrees Kelvin. A cryogenic chemistry and geology laboratory in our back yard. We could study this in the Kuiper belt or in our own back yard.

The sheets of ice are thought to be an accumulation of billions of years of cometary vapors. The layers of these ice sheets could tell us the history of our solar system just as sedimentary rock tells the history of life on earth.

The cold traps would be ideal places for infra red telescopes. The lunar far side can shield from earth's radio noise.

The presence of water in lunar magma have also upset accepted theories on lunar formation. We have a great deal to learn from the moon.

There is so much we can learn from Mars. Stuff about planetary evolution... how things interact in that different environment... past existence of water, environmental changes...

And the moon also has history and geology lessons to teach.

Given that the moon's face isn't regularly erased by weather and erosion, the moon is a better record of history. The lunar cold traps are the best time capsule I could imagine.

even things that could affect our knowledge of how life formed and how it could potentially arise elsewhere (which is, of course, a Very Big Question).

Assuming there's life on Mars, which hasn't been demonstrated. If our goal is to look for life in a liquid water environment, Europa's a 1000 times more interesting than Mars.

And there is another issue: if you can do Mars, you can do the Moon. But if you can do only the Moon, chances are very good that you won't be able to do Mars. Insisting that lunar science is so extremely important is robbing science of the ultimate goal of Mars.

Were you aware that EML1 and 2 are potential hubs for low delta V routes to various destinations in our solar system?

EML1 and 2 have a 2.4 km/s advantage over LEO for Mars or any deep space destination. It has an about 12 km/s advantage over earth's surface.

Lunar propellant, drinking water, radiation shielding water, nitrogen and oxygen to breath -- all can be exported to EML1.

A ship fully stocked with propellant and consumables departing from EML1 has far more capability than a ship of similar mass launched from LEO.

Given a propellant depot in LEO, a propellant depot in EML1 as well as life support consumables, A very able MTV could be launched from earth's surface with a 70 tonne to LEO launch vehicle.

On the other hand, Mars is not well situated to export propellant and consumables to the EML1 transportation hub.

 

[Urwumpe]

Skylon is way more than just a paper rocket already. It is a early concept that, contrary to the rockets and spacecraft of a major western hemisphere spaceflight agency, manages to meet its development milestones.

It can still fail, the technological risk is still high despite the very advanced precooler concept being now validated. But it won't fail because of bad planning.

 

[T.Neo]

Urwumpe is right. I'm not going to go responding to each and every single thing you say.

Hop David, I find the way you present your views to be extremely frustrating.

You cherry pick things to support your version of reality and make any engineering solution that you don't like seemingly impossibly difficult.

You follow the words of certain aerospace engineers like they are gospel. Yet you deride the work of other engineers as "paper rockets".

You accuse me of handwaving while you furiously handwave away the issue of infrastructure on the Moon. This is clearly evident not by efforts to address the issue, but rather the lack thereof.

Your comments on Mars surface science illustrate your grand lack of knowledge in that area, and you make debatable claims about the value of the Moon.

You confuse a specific accident with a specific cause with the difficulty of a very wide range of engineering solutions. Then you equate the death of astronauts with the difficulty of a wide range of engineering solutions.

You keep on complaining about Ares V having issues because it was being designed as a "Mars Rocket" while you don't bother trying to understand the various problems with the Constellation program structure, or the fact that no plans, dates, or concrete hardware concepts existed for Mars under Constellation.

When considering anything other than the Moon, you become a proponent of heavy lift vehicles. But instead of trying to justify the problems of HLV's, you support them.

You don't acknowledge when I have pointed out problems. Instead you insist such problems do not exist and that I "do not know" or "do not understand".

You don't bother about the way systems perform or their requirements. You just stick to (some of) the physics. You say "this number is smaller than that number, therefore this is better than that by a magical margin". You illustrate your claims with cute pictures but you don't try to address solutions to really pressing problems.


I've dedicated most of my boring and uneventful life to understanding how these things work. I may not be very good at it, but at least I try. In short, your lack of common sense in terms of considering problems and solutions instead of sticking to your favourite idea like cyanoacrylate, is something I find highly infuriating.

 

[HopDavid]

Skylon is way more than just a paper rocket already. It is a early concept that, contrary to the rockets and spacecraft of a major western hemisphere spaceflight agency, manages to meet its development milestones.

The vehicle is based on HOTOL. Did HOTOL meet its milestones?

Also contrary to the rockets and spacecraft of a major western hemisphere spaceflight agency, Reaction Engines hasn't achieved orbit.

It can still fail, the technological risk is still high despite the very advanced precooler concept being now validated. But it won't fail because of bad planning.

Until Skylon has flown, it is too early to sing praises for it's re-entry and TPS design.

Re-entry and TPS are and will remain formidable engineering challenges.

 

[T.Neo]

The vehicle is based on HOTOL. Did HOTOL meet its milestones?

The vehicle solves the problems of HOTOL.

Also contrary to the rockets and spacecraft of a major western hemisphere spaceflight agency, Reaction Engines hasn't achieved orbit.

And this makes them incapable of reaching orbit? :facepalm:

Until Skylon has flown, it is too early to sing praises for it's re-entry and TPS design.

Re-entry and TPS are and will remain formidable engineering challenges.

According to whom? You? Have you even tried to find out what the TPS of Skylon is like?

I don't think I've seen people complaining too much about Skylon's TPS. I may be wrong. I think there is more concern over the engines, which would be solved by some of the testing Reaction Engines plan to perform.