Elon Musk says he will put millions of people on Mars.

[Skipjack]

Woah, is there evidence that this report was held back specifically so it could not be used to sell SLS? I was under the impression that NASA doesn't much want SLS. OBama didn't want it. It's Senator Nelson who wants it, and everyone else who doesn't know what's going on.

You are not that far off. The administration did not want the SLS and rather wanted funding for commercial crew and ideas like the things discussed in the paper. But NASA is just a government agency and there are people at NASA that work for Nelso and most of all Shelby and Hatch.

[GIThruster]

Em, I don't think so. NASA is an executive agency. There's no legal authority that anyone there should be working for anyone in congress. Congress may hold the purse-strings, but legally, it is the executive that directs NASA and as time goes on, it is congress who has been violating separation of the branches by making stipulations as to how NASA will spend its money. For instance, when Nancy Pelosi stipulated there would be no money spent on a Mars program, she was violating the separation between executive and legislature.

What people like Nelson are doing is likewise unconstitutional. Congress can fund or not fund NASA, but they are not supposed to be micromanaging what NASA does, and we can now see what can go wrong when this authority held by the executive migrates to the legislature--you have people spending what will amount to many tens of billions of dollars (latest estimate is $86B) on programs not in the national interest.

[HopDavid]

But I entered the conversation when someone said Mars is a better near term goal than the moon.
If the moon is skipped for Mars, lunar propellant wouldn't be avaiable.
If the program is government funded, a long term project is difficult to sustain through many election cycles.
If the program is privately funded, a long term project is difficult to sustain past an investor's working lifetime.

Lets see now...I started the thread based on Musk's statement in the link on the 1st page about his desire to see millions on Mars. I said nothing about "skipping the moon".

And your OP isn't the entire thread. If you endorse going to the moon, we're on the same page. But not everyone participating in this thread shares your view.

Far as I am concerned you can do both concurrently.

So far as I know, Musk's plan doesn't include lunar development. Nor is there a NASA plan for developing the moon.

Should we develop the moon, a lot of Musk's dreams would become much more viable. Whether that comes to pass is an open question.

[HopDavid]

Musk hasn't developed any oogie boogie science that enables us to circumvent the rocket equation.

True, but Tethers Unlimited has.

A tether loses momentum each time it makes a suborbital catch. How is momentum maintained?

If the tether was making catches from higher orbits as well as suborbital, momentum boosts could be balanced with momentum sapping catches. Thus receiving lunar propellant could balance catching suborbital rockets. Lunar commerce could make a tether more viable.

Given tethers and lunar propellant in LEO, the FMR needed becomes much less of a show stopper.

However, so far as I know, Musk's plans don't include tethers, nor do they include lunar development.

[KitemanSA]

Musk hasn't developed any oogie boogie science that enables us to circumvent the rocket equation.

True, but Tethers Unlimited has.

A tether loses momentum each time it makes a suborbital catch. How is momentum maintained?

Electro-dynamic tether, i.e., and electric motor using Earth as the reaction mass. Ok, MAYBE the rocket equation actually applies, but that is one HECK of a big reaction mass!!!

[Skipjack]

There's no legal authority that anyone there should be working for anyone in congress.

Just like noone in congress should be working for some private corporation, but from what it looks like, they are all in somebodies pocket.

[HopDavid]

That means YOU try figuring. Until you do, you won't accept others statements. Try it and see.

Here's some numbers:

285.83 kJ to crack a mole of water (18 grams)

An I.S.S. Solar array wing puts out about 32.8 kilowatts

Each I.S.S. solar array weighs about 1087 kg This doesn't include the SARJ.

That's about 30 watts per kilogram.

It'd take about 13 mega joules to make a tonne of propellant.

A 50 tonne solar power source with the same power density of the I.S.S. SAW would take about 3 months to crack a tonne of water.

This doesn't include the power needed to liquify the hydrogen and oxygen.

You see the above? That's numbers. Those are cites.

So far I haven't seen you provide either. Furious flapping of the lips is no substitute.

[krenshala]

So, at 1 AU, our star provides approximately 1353 ±21 W m-2 (per this page). So, thats 1.353 ±0.021 kJ/sec. If a one square meter mirror was able to focus all the sunlight it received it would generate 1353 kJ/sec. Lets be pessimistic/conservative and say only half of that ends up being "useful" -- 676.5±10.5 kJ/sec of reflected sunlight from the 1 m^2 mirror.

So, if it takes 285.83 kJ/mole of water (and assuming 676.5 kJ/sec input) you should be able to crack 2.3667914495 moles per second. 23472.940790014 seconds (6.5202613306 hours) for 1 Kg of water.

If you get really pessimistic, and assume only 10% efficiency, you still end up with 135.3 kJ/sec or 0.4733582899 moles/sec. This would be 32.6013066528
hours for a Kg of water.

From a quick googling, there appear to be a number of choices in material to thermally crack water via chemical reaction (O2 absorbed by a material that is then heated to release the oxygen after the hydrogen has been collected). I didn't look deep enough to see what inefficiencies that adds to the process, which is why I started at 50% and included 10%. It is entirely possible the process is more efficient, and thus would provide shorter times than what I show above.

[KitemanSA]

That means YOU try figuring. Until you do, you won't accept others statements. Try it and see.

Here's some numbers:
...
You see the above? That's numbers. Those are cites.

So far I haven't seen you provide either. Furious flapping of the lips is no substitute.

If you insist on doing this the STUPIDEST way, then fine, it doesn't work well.

Now, try THERMAL cracking with lightweight mirror; like I said before.

[KitemanSA]

If you get really pessimistic, and assume only 10% efficiency, you still end up with 135.3 kJ/sec or 0.4733582899 moles/sec. This would be 32.6013066528 hours for a Kg of water..

per square meter of area. Assuming a kapton mirror (~12g/m²) and using the same mass as HopDavid did (2x1087kg) you would have ~ 2.2E6/12 m² ~ 1.8E5 m². So: 32.6hr/kgm²/1.8E5m² = 1.81E-4hr/kg or 5.5E3kg/hr. Let us call it 5Mg/hr. A tad different.

[GIThruster]

http://www.youtube.com/watch?v=4fS1FxBq ... =endscreen

[krenshala]

If you get really pessimistic, and assume only 10% efficiency, you still end up with 135.3 kJ/sec or 0.4733582899 moles/sec. This would be 32.6013066528 hours for a Kg of water..

per square meter of area. Assuming a kapton mirror (~12g/m²) and using the same mass as HopDavid did (2x1087kg) you would have ~ 2.2E6/12 m² ~ 1.8E5 m². So: 32.6hr/kgm²/1.8E5m² = 1.81E-4hr/kg or 5.5E3kg/hr. Let us call it 5Mg/hr. A tad different.

Yeah. I picked a 1 m² mirror on purpose. Its tiny and easily put in place. A more likely scenario would be 10 m² at a minimum, which decreases the times accordingly.

[HopDavid]

So, at 1 AU, our star provides approximately 1353 ±21 W m-2 (per this page). So, thats 1.353 ±0.021 kJ/sec. If a one square meter mirror was able to focus all the sunlight it received it would generate 1353 kJ/sec. Lets be pessimistic/conservative and say only half of that ends up being "useful" -- 676.5±10.5 kJ/sec of reflected sunlight from the 1 m^2 mirror.

So, if it takes 285.83 kJ/mole of water (and assuming 676.5 kJ/sec input) you should be able to crack 2.3667914495 moles per second. 23472.940790014 seconds (6.5202613306 hours) for 1 Kg of water.

Thermal energy isn't the same as electrical energy.

From a quick googling, there appear to be a number of choices in material to thermally crack water via chemical reaction (O2 absorbed by a material that is then heated to release the oxygen after the hydrogen has been collected). I didn't look deep enough to see what inefficiencies that adds to the process, which is why I started at 50% and included 10%. It is entirely possible the process is more efficient, and thus would provide shorter times than what I show above.

If you had provided cites showing x number of thermal joules cracks y kg of water, that would have been useful.

As it is, the above is nothing more than furious hand waving. I am not interested in your unsubstantiated speculation.

[HopDavid]

Assuming a kapton mirror (~12g/m²)

Saran wrap that magically assumes the shape of paraboloid.

Sorry, your mirror will need some structural support. There will also need to be some sort of turntable to keep the parabolic mirror focused on the water as the water depot changes its position with regard to the sun.

[HopDavid]

Now, try THERMAL cracking

You have yet to provide a cite describing this thermal cracking process.