Moonwards

Russell Borogove

16:21

Battle fleet accidentally eaten by a small dog, etc.

kim holder

:D

Russell Borogove

Okay, so, Hohmann was of course right in saying the mining shuttle needed to be nuc.

kim holder

you think?

Russell Borogove

yeah. The CECE-based lander tops out at 4960 m/s ∆v with a full fuel load and -no- cargo, which isn't enough for a round-trip according to his figures.

kim holder

eep. can't design around that?

because this is all assumptions, so if it needs a different design, i should just do that.

not that nuclear shuttles don't really tickle me.

put a second engine on it?

Russell Borogove

16:24

Not in a way that makes it attractive. Scale it up and it doesn't fit on a SVE. I may be being over-conservative in structural mass, fuel for RCS thrusters, and so on, but even if I strip it it won't carry enough cargo to be worthwhile.

# engines don't matter, just fuel mass ratio and specific impulse.

kim holder

hm

Russell Borogove

I mean, what mass of ice are you hoping to move per trip?

kim holder

well, not much, necessarily. that's why i started going off on the overall plan. i'm not planning to sell this as fuel, it's to facilitate development of the colony itself.

and there won't be people on the site for several years, minimum 5, and the robots don't need water.

Russell Borogove

hmm

kim holder

but shuttles capable of going to LEO and picking up a cargo pod, for instance, could really increase the amount of mass that can be gotten to the moon for the same price

and of course it is good to stockpile, so maybe you could do something really audacious like put in a pool :D

might be useful for chemical processing too

Russell Borogove

16:29

Again you'd need nuclear for that. Hydrolox shuttle can happily go to lunar orbit and back with cargo, but not to earth.

kim holder

yeah. i've occasionally pondered adding on an ion drive system.

Russell Borogove

(To lunar orbit and back is only a little more ∆v than a one way suborbital hop!)

kim holder

i briefly wondered if it could drop things from orbit some way that wouldn't be completely disastrous, but that doesn't seem likely...

Russell Borogove

I have warm fuzzies about the hydrolox lander because it doesn't require any controversial or unproven tech. The RCS thrusters are straight off Apollo, even. (AJR still offers them on their site.)

The 50-year-old technology of the far future.

kim holder

yeah, these things are true. there is a stance i've taken for the sake of making the site more provocative and exciting - it presents what could be done if we went all-in, and used the best and most sensible technology.

on the other hand, i want it to present a realistic picture of what could be done, not doing anything that automatically tacks on a development program of 5 or 10 years at the beginning, for instance.

Russell Borogove

16:36

And for a lot of applications, I think NTR is great, particularly if it's headed away from anywhere where people want to live. It would just be a shame if you crashed a nuclear reactor into the site on the last ice run before people were scheduled to move in.

kim holder

hmmmm...

Russell Borogove

NTR is also in this weird limbo, where technically it's been ready for 40 years, but politically it's impossible.

I'll run the numbers on it and see what a NTR shuttle that can be launched on SVE equivalent looks like, though.

kim holder

i've decided to ignore political hurdles. the idea is 'this is what we could do if we tried. what is that worth to you?'

@RussellBorogove that would be great Russell. :)

Russell Borogove

But this is both ignoring political hurdles and actual risks, IMO. Sometimes landers crash.

kim holder

well, i'd need to look into it more. But my understanding was that the level of contamination that could be caused by reactors of this size can be managed.

maybe it means that the landing pad needs to be a good ways from the colony, for instance

Russell Borogove

16:41

yeah. A km or two of clearance would put me at ease, I guess

kim holder

that should be manageable

i mean, hydrolox rockets can explode, so some distance is nice for those too.

Russell Borogove

true story

As far as dropping cargo from LLO without a lander... take a tube with a bunch of breakable diaphragms along its length, and put a ballast on one end and a payload on the other, and drop it onto the moon. Each diaphragm slows the payload as it slides down the length of the tube until it stops gently at the ballast end.

If the payload can survive 100g deceleration, the tube only needs to be, let me see... one mile long!

Everything about space flight is terrifying.

kim holder

:D

i thought about the balloons used on mars, but the deceleration they had to handle was a small fraction of what this would be.

my mind keeps turning to sling launchers, you see, but i can't figure out how to decelerate the packages on the arriving end

besides, that comes when the colony is highly developed

Russell Borogove

If you're just sending bulk matter, maybe dig a really big hole and aim carefully? But I'm guessing that it would just pulverize and go everywhere even so

kim holder

yeah, i wondered if you could get it to hit a slope that almost matches its vector, so it rolls...

but that is a mighty big hole...

Hohmannfan

20:16

@KimHolder I can not find a structured way of expressing my thoughts on the IceShuttle, so here is a blob of text instead:

Example vehicle, just to get the feel about it:
If we use a RD-0410 nuclear engine, (perhaps a bit unfair, as it was just a prototype, but its parameters can be used as a lower bond). To have a thrust to weight ratio larger than 1.5, the shuttle can be approximately 25000 kg fully loaded. From the loooooong list of upper stages listed at encyclopedia, it seems that the totall mass to dry mass ratio is approximately 12. If we assume a ratio of perhaps 10 for the mass not including the engine, we can have 20700 kg of water. I chose to round that down to 20000 kg to have some margins. After a …

Another thing is, why carry water? After all, water is 8/9 oxygen, and that is easy to produce anywhere. The hydrogen is the important stuff.

kim holder

hm. and hm.

producing enough oxygen to make water again, and the equipment needed to do that, is a lot of infrastructure though.

Hohmannfan

But transporting dead weight is also a waste.

You probably want to produce oxygen at the base anyway

kim holder

at least, that is my thought. I have no idea what the production rate of oxygen would be for the solar furnace. It is highly experimental.

finding a good reference paper on pyrolysis of oxygen has eluded me so far.

Hohmannfan

"Pyrolysis" is such a cool word :)

kim holder

i believe the figure quoted in one document i have somewhere is that extended time at over 2000 C would likely yield about 20% of the charge's oxygen

but it isn't clear what they mean by 'an extended time'

given that if the solar furnace works and there aren't problems with the tank degrading, or something else, you just fill it with regolith and it works away using very little power

Hohmannfan

20:22

Heating up a rock, what can be escaping other than oxygen? I guess the process can actually produce pretty high grade oxygen, if you chose the right rock.

kim holder

below the temperature that produces oxygen, oxides of sodium, potassium, and phosphorus boil off first

and sulfur

Hohmannfan

If the regolith has enough carbon or nitrogen to contaminate the oxygen, well, then it is a valuable resource.

kim holder

sulphur :)

Hohmannfan

:P

kim holder

the content of C and N is in parts per million, i am ignoring it for now

Hohmannfan

20:25

That is a little bit sad. Bottleneck resources and everything

kim holder

the content of both could be significant at the poles

Hohmannfan

I really hope so

I am a big fan of ammonia

kim holder

in a closed-loop system - supplemented from Earth until we figure out how to do that right - i don't think those two chemicals will be a big issue, really

i have done little work so far on manufacturing, but what i have looked into, in relation to construction, doesn't need either

Hohmannfan

But in the long run, you are going to need carbon, phosphorous and nitrogen to expand. Closed loop first though.

Do you consider metal production?

kim holder

i'm leaning really heavily on the use of basalt at first of course. but iron production seems relatively easy to reach.

elemental iron is enriched by oxygen production

Hohmannfan

20:30

The creative use of basalt was what made me take a closer look at Moonwards originally.

kim holder

if an electrolysis method works out, which it really should, aside from whether it is efficient

then you get mixed metals as a product

@Hohmannfan :)

it really would be great if production of basalt fiber is fairly easy

Hohmannfan

Worst case in metal production, you can electrolyse water, and reduce the ore with hydrogen.

Anyway, internet=down soon. Good night.

kim holder

aw - gonna miss the soyuz launch :)

good night sig

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