Envisioning the world of 2100

[gturner]

Keeping the aluminum molten in just an insulated tank is pretty simple because it has a huge thermal mass. Getting it molten is also simple with just resistance coils or even tungsten halogen lights in an insulated oven (which would describe the fuel tank) because it melts at 900 to 1200F. Of course the simplest way to melt aluminum is probably with a solar reflector, after which you'd pump it into the tank.

I'd try to heat it much higher than the melting point to improve viscosity and impart a little extra energy, since extra thermal energy in the aluminum translates into better performance as a propellant. If you heat it to 900C you add about 1.2 MJ/kg to the 32.2 MJ/kg heat of combustion, probably raising the ISP from about 285 up to 290, which is servicable as a lunar propellant.

I'm not sure what experiments have been done with molten metal fuels, though. The probably questions to answer are how the injectors fair. If the engine and tank are being heated prior to launch anyway, and you only depend on one big burn to get into orbit, it wouldn't really matter if residual aluminum in the lines or injectors solidified after engine shutdown, because such an engine would only be used to launch other materials to a fuel depot or assembly station.

Extracting aluminum on the moon is relatively straightforward, since the most common mineral on the moon is anorthite (NaAlSi3O8), which we're looking at switching to because bauxite is getting harder to find. The cost is of processing anorthite is about twice that of bauxite. You're just going to need a lot of electrical power.

[gturner]

sojourner wrote:

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The problem with your idea is that means a lot of time spent in the Van Allen belts. Not a good thing for a healthy crew. You want to traverse them as quickly as possible.

It's a tradeoff between the mass of radiation shielding and extra food (and pay!) you need to dawdle through the Van Allen belt versus the mass of fuel you save by taking the high ISP, low thrust route. If the trips are going to be frequent, you'd want to have radiation shielding anyway in case of solar storms.

You could also provide for both, going light and fast on early missions until you can launch crudely processed lunar material for radiation shielding, and then add that to your ships along with the ion drives. The internal core of the ship (the expensive part) thus gets re-used.

Or you could think further on the problem and use the extra mass of cargo you're delivering (with the high-ISP engines) as the radiation shielding on the outbound flight, and use cheaper lunar fuel and no cargo to make a rapid return trip.

[Crazy Eddie]

sojourner wrote:

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The problem with your idea is that means a lot of time spent in the Van Allen belts. Not a good thing for a healthy crew. You want to traverse them as quickly as possible.

The Van Allen belts aren't that big of a problem; shielding against them isn't overly hard, and if you're using an ion engine, you can run a course that partially bypasses them anyway.

gturner wrote:

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You could also provide for both, going light and fast on early missions until you can launch crudely processed lunar material for radiation shielding, and then add that to your ships along with the ion drives. The internal core of the ship (the expensive part) thus gets re-used.

I'm thinking the crossing through the Van Allen belts wouldn't take so long that the crew couldn't ride out that part of the trip in a heavily-shielded central node (three or four days through either belt, depending on the flight profile). Heavier shielding would be an upgrade with better technology, but again, we're talking 2020s, 2030s timeframe and that might be available by then.

OTOH, I've heard Franklin Chiang Diaz suggest the VASIMR's magnets could be used to provide shielding for a craft during CMEs. A similar technique may be applicable in this case (also, using a VASIMR could reduce your transit time from three or four months to three or four weeks).

[gturner]

A couple of days transiting the Van Allen belt shouldn't present much of a mass issue, since Gemini showed you could shove two astronauts in a phone booth for a week. About 6 inches of polyethylene would stop most of it (99%) and with California bans on plastic shopping bags, there should be enough of it freed up for deep space applications.

Almost any proposal for near-term deep space needs to include something like an upsized, shielded Soyuz orbital module with its own life support, power, sleeping arrangements, and bathroom, which due to its mass and sophistication should be reused across many missions. That means it needs one or more docking adapters and perhaps its own minimal RCS system for station keeping between missions. The ideal way to test the living arrangements would be to attach it to the ISS for several months, perhaps as a block I non-shielded to be followed by a block II shielded version that includes layout and equipment improvements based on experience with the block I. Unfortunately there's no current funding available for such a module because everything is allocated to the SLS and Webb.

[Crazy Eddie]

^ That doesn't strike me as the kind of thing that would be difficult for private companies to tinker with, though. Depending on the mass of the shielding, a radiation-hardenned Dragon would suffice for that application (and Dragon is ALOT roomier than a Gemini).

[RAMA]

Ghostavo Fring wrote:

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And yet investment in fossil fuel development continues to go up, not down. That undercuts your entire premise.

As for peak oil--US oil production peaked about 30 years ago. It's ticking up now, but global production is nearly flat. We're looking at more of a "plateau oil" scenario.

http://www.investmentu.com/2012/Octo...-resurces.html

http://www.triplepundit.com/2012/06/...-billion-2011/

http://revmodo.com/2012/06/14/solar-...nts-worldwide/

http://www.guardian.co.uk/environmen...nt-solar-power

http://www.affordable-solar.com/News...rgy-investment

http://www.treehugger.com/clean-tech...red-laser.html

http://www.popsci.com/technology/art...wer-down-earth

http://www.dailymail.co.uk/sciencete...ally-WORK.html

https://www.youtube.com/watch?featur...v=5dz-iiVPLL4#!

https://rt.com/news/solar-energy-record-break-332/

https://www.nytimes.com/2012/06/19/b...anted=all&_r=0

[sojourner]

Hey! spamming links to unrelated articles! good job. Not one of those links relates to Ghostavo's comments on oil production. Unless you somehow got confused by the word "solar" and thought it meant "oil". And hey, you slipped in a Diamandis TED talk that's about on the level with a TV evangelist? seriously?

[Crazy Eddie]

It also leaves out the fact that we are not less than forty years from anything resembling practical asteroid mining.

And even then, mining asteroids is extremely unlikely to provide any benefit whatsoever to the global economy, for the very simple reason that the demand for those resources will be far higher among off-world outposts and communities than it will be back on Earth. You wouldn't spend forty thousand dollars shipping a kilogram of platinum to a consumer on Earth when you could spend four thousand dollars shipping it to a consumer on the moon, especially if that sale also turns into an investment that strengthens future sales.

Earth is sitting at the bottom of a steep gravity well, which prevents us from cheaply sending materials into space; it's also surrounded by a thick atmosphere, which prevents things in space from cheaply returning. It is the most literal manifestation of the term "trade barrier," and most of the solar system's resources are on the other side of it. The instant humans begin living in space and using those resources, Earth will ALWAYS be at a competitive disadvantage; and off-world products will begin to replace Earth-made ones almost the instant they become available.

[publiusr]

newtype_alpha wrote:

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HLVs simply don't have the work history to justify the kind of money NASA has been ordered to spend on them, even if they had a coherent plan for how to USE them, and they don't.

Again, STS is a history of HLLV scale operations and nasaspaceflight is full of coherant plans being developed for BEO exploration that VentureStar--which would have cost more than STS--would have competed with.

gturner wrote:

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I just did an interesting first pass calculation based on an Apollo mission using lithium aluminum hexahydride/H2O2 instead of Aerozene-50/N2O4.

http://www.sps.aero/Key_ComSpace_Art...plications.pdf

With a 500 psi chamber pressure it has a vacuum ISP of 469, whereas everything above the S-IVB on Apollo had an ISP of 311 to 314.

Holding the dry mass of the lunar ascent module, descent module, command module, and service module consant would still result in a required LEO mass of 57 tonnes, instead of 130 tonnes. Using it the 3rd stage would reduce that stage's dry weight, too, meaning you'd only need one launch on a Falcon 9H to fly the same mission.

Well, it is supposed to lift only 40-53 tons or so. Now some solid augmentation might allow for that if Musk will allow it. But even he is looking at the BFR concept again it seems

Falcon MCT

http://www.flightglobal.com/news/art...rocket-377687/
http://forum.nasaspaceflight.com/ind...?topic=30103.0
http://www.nasa.gov/home/hqnews/2010...eavy_Lift.html

"7m+ Core, Not RP-1, 150T or larger"

Now with the fuel you are talking about--this can only increase cargo to the Moon using both methods (large LVs and different fuels.) Besides, using HLLVs allows faster transit than using the pieces-parts method--and Nautilus-X was designed by Mark Holderman, who was a proponent of some form of shuttle derived heavy lifters and External tank applications: http://aeromaster.tripod.com/grp.htm Three or so SLS launches should do the trick.

Something interesting I saw from the web:

Given the availability of high efficiency tankage and high T/W ratio engines from SpaceX, then reusable boosters make the lunar surface directly available to earth launched hydrogen upper and core stages with no interim staging, stops or refueling necessary. We've already gamed this out completely and have published our results. Given enough boosters, you could even land an SLS stage on the moon by incorporating the upper stages engines (throttleable Rl-10s) into the interstitials of the four SSMEs.

We can be there just as soon as current upper stage engines are converted to low gee landing engines. These kinds of engines were tested in the sixties (J2-S) and with the Delta Clipper (RL10A-5).

Similar: http://books.google.com/books?id=KOQ...20Moon&f=false

All hydrolox HLLV's with no payload other than a docking port themselves can become wetstage station modules with no chemical contamination associated with other fuels, so it isn't as if room need be an issue.

gturner wrote:

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Getting back to the SLS, the design has inherent limitations from the requirements to keep the same people building the same things. At what point in the SLS program will someone ask if using the same basic SRB for 50 years is the opposite of cutting edge? The core stage is already over 200 feet tall (due to using a narrow tank diameter for heavy lift).

R-7 is over fifty years old and going fine--and will be developed. The "narrow" tank was probably a result of the meddlers from DIRECT who wanted to kill off the larger Ares V for current ET tooling, which does allow things to get started off easier. BFR will be a bit slimmer if made, but Musk is already working with Dynetics on Stratolaunch--and they are the ones looking at an F-1 comeback for LFBs. They actually might play a part in MCT as well...

gturner wrote:

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Keeping the aluminum molten in just an insulated tank is pretty simple because it has a huge thermal mass.

Yep, I've seen molten aluminum carried by trucks over the freeway
http://www.youtube.com/watch?v=Nhvm_VOOWC0

Speaking about Gemini, you might find these links interesting
http://www.wired.com/wiredscience/20...m-gemini-1962/
Dyna-Soar's cousin http://www.wired.com/wiredscience/20...s-glider-1960/

[Crazy Eddie]

publiusr wrote:

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Again, STS is a history of HLLV scale operations...

So was Saturn V. How'd that work out for NASA?

and nasaspaceflight is full of coherant [sic] plans...

The internet IN GENERAL is full of coherent plans for space exploration, but I wouldn't want to spend a billion dollars putting a piece of Doctor Who fanfiction into orbit.

R-7 is over fifty years old and going fine--and will be developed.

SLS is not the Soyuz, and neither was the shuttle. Both are projected to operate at five to ten times the cost at perhaps one third the flight rate; both would be damned lucky to have the Soyuz's success rate.

But that just raises another interesting point, doesn't it? Why is it that HLVs like Saturn-V, Energia and STS have consistently under-performed in terms of cost to lift ratio and reliability compared to smaller launchers like Saturn-IB and Soyuz? We consider the shuttle program to be impressive -- 140 missions in over twenty years -- but that's small potatoes compared to the R-7 family, with a resume that includes over 1700 launches since they went operational; Soyuz alone accounts for over half of those.

Falcon 9 has twice the capacity of the Soyuz family, and it's only just entered service. Now imagine what the Falcon family is going to look like with 1700 launches under its belt. Right around the time SLS begins to achieve its maximum carrying capacity, the Falcon Heavy will have already surpassed its Block 1 configuration for about a tenth of the cost.

[sojourner]

You know, I'll say it right now. If SpaceX decides to build an HLV, I would support it. You know why? Because they will only do it if they can close a business case. It will put SLS out to pasture.

[publiusr]

They say they will have more in one to three years. This looks to compete with Block II

Now 1,700 launches, newtype? R-7 was able to do that because it was funded by a nation. I hope Space X is around in 50 years. Remember too--R-7 was considered too large at first too--a product of big gov't too. So while Ayn Rands fictional heros were making skyscrapers, Korolov's cross rose much higher.

[sojourner]

publiusr wrote:

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They say they will have more in one to three years. This looks to compete with Block II

Now 1,700 launches, newtype? R-7 was able to do that because it was funded by a nation.

Because it was affordable to that nation. How many N-1's did they launch?

Remember too--R-7 was considered too large at first too

For about 10 minutes.

[gturner]

publiusr wrote:

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They say they will have more in one to three years. This looks to compete with Block II

Now 1,700 launches, newtype? R-7 was able to do that because it was funded by a nation. I hope Space X is around in 50 years. Remember too--R-7 was considered too large at first too--a product of big gov't too. So while Ayn Rands fictional heros were making skyscrapers, Korolov's cross rose much higher.

Korolev didn't succeed because of the state, he largely succeeded despite it. He had to take an extremely hands on approach, from supervising the designs and the running of the machine shop (basically being their Elon Musk, not their James Webb), to firing any underling who crossed him or screwed up, to walking up to machinists and offering them cash to do things his way. It barely worked, and once he was gone they really couldn't take things much further because government agencies are notoriously non-cooperative.

[Crazy Eddie]

publiusr wrote:

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They say they will have more in one to three years. This looks to compete with Block II

Now 1,700 launches, newtype? R-7 was able to do that because it was funded by a nation.

Correction: the R-7 was funded by a military. Which means that unlike the Saturn-V and the shuttle, it had a continuing justification to exist irrespective of the nation's political will. Military spending is ALWAYS politically acceptable; peaceful space exploration, not so much.

Remind me again: what are the potential military applications being considered for the SLS?

I hope Space X is around in 50 years. Remember too--R-7 was considered too large at first too

Too large for a practical ICBM, yes. But Korolev didn't built it to be an ICBM, despite the fact that that's what the Soviet military had ordered him to develop. He managed to piggyback his exploration program onto the back of what was essentially a nuclear weapons delivery system, and he was damn lucky to get away with it.

Consider the question I asked you above. The EELVs all have a much higher flight rate than the shuttle or the SLS can ever aspire to. They get most of their business by handling government contracts, including spy satellites and mysterious automated spaceplanes. Even if we never ever put another American into space, ULA will still be able to stay in business using those defense contracts.

SpaceX has wisely made a move to make the Falcon 9 available for military payloads as well, especially with their little trick of implying (falsely, I sometimes think) that the Falcon Heavy would be launching primarily out of Vandenburg. Right now they're depending on their service contract to the space station, but if they succeed with the Falcon Heavy gambit, SpaceX too will have a "sure thing" fallback if space exploration bites the political dust and will continue in business through its military contracts.

I repeat that there are no military payloads being considered for the SLS at the current time. The Air Force and the NRO are happy with the Delta-IV Heavy and the Atlas-V, and they're likely to be even happier with the Falcon Heavy when it becomes operational. SLS is too high profile, too expensive, and when it goes online, too restrictive in its schedule in addition to being untried and untested. That means that SLS is already on shaky political ground, and depends entirely on how fashionable space exploration is in the minds of a collection of fickle voters; its chances of being cancelled would probably double if Star Trek Into Darkness starts getting bad reviews.