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Water Found Deep Inside the Moon

news.nationalgeographic.com

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Re: Water Found Deep Inside the Moon

#251

Post by nine_k »

danielbarla wrote: post #236
nine_k wrote: post #214

Earlier quoted context omitted.

On Earth, it's hard to build due to much higher gravity, higher required orbit, and the atmosphere. Getting much shorter lengths of much less strong fiber to Moon may be more realistic than 20.000 km of super strong carbon fiber to GEO.

I'm not too clued up on the topic, but I was under the impression that a lunar elevator would potentially require much longer cables than on Earth (primarily due to the lack of spin of the moon). From the Wikipedia article [1] > There are two points in space where an elevator's docking port could maintain a stable, lunar-synchronous position: the Earth-Moon Lagrange points L1 and L2. L1 is 56,000 km away from the Ear…

This is correct, unlike my assumption of a shorter cable above. OTOH due to lower gravity, the tensile strength required is still much lower. To quote the very article you lonked:

> the engineering requirements for constructing a lunar elevator system can be met using currently available materials and technology.

Re: Water Found Deep Inside the Moon

#252

Post by Kubuxu »

dwringer wrote: post #248
hoorayimhelping wrote: post #217

Earlier quoted context omitted.

fewer than twenty five seconds of googling: https://en.wikipedia.org/wiki/Delta-v_budget From LEO to the surface of the moon is 5.9 km/s From LEO to the surface of Mars is 4.1 km/s

Unless I'm misreading something, both the text and graphic of that page seem to indicate it's 4.1km/s from low Mars orbit to the surface of Mars. I can't find anywhere saying it's 4.1 from LEO.

I get 2.5+0.7+0.6=3.8 to get into Mars Transfer from LEO. If we were to execute perfect aerobraking, the rest would be free. It for sure wouldn't be perfect so some fuel will be needed but not that much.

Source: https://en.wikipedia.org/wiki/Delta-v_budget#Delta-vs_betwee...

Re: Water Found Deep Inside the Moon

#253

Post by bb611 »

Abishek_Muthian wrote: post #210

"In 2009, NASA crashed a rocket and a satellite into a crater on the moon’s south pole, in the hopes of picking up additional watery evidence. " NO, In 2008 ISRO crashed Moon Impact Probe (MIP) into lunar surface as part of Chandrayaan-I mission. MIP didn't have any specific role, other than political agenda. The NASA's Moon Minerology Mapper M3 onboard of the Chandrayaan spacecraft was instrumental in providing the…

I think you're right to ask for credit where it's due, but this is not such a place - the event being referenced is the 2009 LCROSS mission: http://www.cnn.com/2009/TECH/space/10/09/probe.moon.crash/in...

I discovered this with a very quick google search of the terms "2009 NASA crash moon"

Re: Water Found Deep Inside the Moon

#254

Post by Tepix »

i2shar wrote: post #184
Robotbeat wrote: post #172

Earlier quoted context omitted.

It's questionable that it's really much lower cost. The Moon, as a vacuum body, doesn't give the option of aerobraking or atmospheric entry, which dramatically reduces delta-V. You can get a payload to Mars' surface with less propellant than getting it to the Moon's surface. And because atmosphere is everywhere (which includes oxygen in the form of CO2 and also water vapor), propellant is way easier to make, so it's…

[To put things in perspective] travel time to the Moon is about 3 days, Mars would be about 150 to 300 days (source: Google).

You don't have to use the cheapest, but slowest Hohmann transfer orbit to get to your destination. You can also spend more fuel and get there faster.

Re: Water Found Deep Inside the Moon

#255

Post by Tepix »

OtterCoder wrote: post #230
Robotbeat wrote: post #175

Earlier quoted context omitted.

Years? Absolutely not. Transfer can be done in about 90 days, less (30 days) if you pursue aggressive entry, high orbit refueling, and nuclear thermal propulsion. Assuming you're settling the place and not just doing flags and footprints, transfer time is the important part.

That's astoundingly quick. 30-90 days is in the same range as crossing the Atlantic via tall ship. With transfer time that low, it really does seem feasible. The two year gaps are a bit rough, but there are plenty of ways to plan for it.

Nowadays ships cross the Atlantic in less than a week.

Re: Water Found Deep Inside the Moon

#256

Post by anon_christian »

For this they willingly are ignorant of, that by the word of God the heavens were of old, and the earth standing out of the water and in the water: Whereby the world that then was, being overflowed with water, perished: 2 Peter 3:5,6

National Geographic: 'Inner Earth May Hold More Water Than the Seas' http://news.nationalgeographic.com/news/2002/03/0307_0307_wa...

Re: Water Found Deep Inside the Moon

#257

Post by Dylan16807 »

aptwebapps wrote: post #222
ChuckMcM wrote: post #189

Earlier quoted context omitted.

Per glindahl's comment from earlier, if we established a space elevator for the moon[1] it would make the delta-v issues moot. Drop off an pick up supplies at the elevator while swinging by on an continuous Earth/Moon translunar orbit. [1] https://en.wikipedia.org/wiki/Lunar_space_elevator

There would still be some delta-v. Anyone have a handle on how much? I'm too lazy to look up the data and do the math.

http://i.imgur.com/SqdzxzF.png

You might save 2km/s if you can use an elevator on the moon. Which is not a lot compared to a space elevator on Earth, but it would definitely be useful. That could be half your delta-v budget if you're going between the moon's surface and an orbit around Earth/Mars/Venus.

Re: Water Found Deep Inside the Moon

#258

Post by tambourine_man »

thescriptkiddie wrote: post #131
tambourine_man wrote: post #7

I've always been more excited about a Moon colony than a Mars one. I mean, compared to Mars, the Moon is ridiculously close. Many of the same benefits Musk seeks (backup for Civilization, excitement) for a fraction of the cost. Low gravity and atmosphere on a dome would be more complicated, but again, compared to Mars, it's right there . It would be a more humble and realistic first step, IMO.

I'm all for building Lunar outposts, but colonization is not really practial. Luna simply doesn't have the natural resources to sustain a civilization. Yes there is water in the regolith, but nowhere near as much as on Mars. And critically, Carbon, Nitrogen, Phosphorus, and Sulfur are only present in trace amounts. Nearly all of the elements essential to life will have to be imported, either from Earth, from Mars, or…

I imagine the first step for producing food in loco would be hydroponic agriculture on either place. Tiny bits of dissolved nutrients (extracted or brought along) should be fine. Actually building soil would be a second step.

Once you get there, almost everything is a little easier on Mars, but getting there (and back?) is a heck of a lot harder.

Re: Water Found Deep Inside the Moon

#259

Post by simonh »

keenerd wrote: post #194
simonh wrote: post #167

Earlier quoted context omitted.

SpaceX have run the simulations and while Red Dragon is possible, there's no way they can adapt Dragon to land on the Moon without adding an extra stage. That difference is entirely down to Aerobraking. Even the thin atmosphere of Mars makes a huge difference. Anyone who plays KSP can confirm this for you, especially using the Real Solar System mod, though the same lessson is apparent even in the stock game.

We can also look at delta-V charts. Earth to the Moon is like 16.4km/s, Earth to Mars is like 14.3km/s using every available aerobraking opportunity (6.4km/s saved) and assuming 500m/s for the final powered landing. (The Red Dragon plan called for aerobraking from 6km/s to 540m/s and then switching to thrusters.) Is that 2.1km/s really a whole extra stage? Or can it be met by reducing cargo capacity somewhat? Two int…

For Red Dragon they were going to add an asymmetrical 'sled' under the capsule that alters its geometry to form a lifting body, so it could spend significantly more time up in the atmosphere braking than most custom designed landers would. The sled would be jettisoned immediately before the propulsive landing.

It's not an ideal design, but this way they would only have had to make minor changes to the capsule, mainly to add more fuel for the landing than the regular design.

Re: Water Found Deep Inside the Moon

#260

Post by Dylan16807 »

Tepix wrote: post #254
i2shar wrote: post #184

Earlier quoted context omitted.

[To put things in perspective] travel time to the Moon is about 3 days, Mars would be about 150 to 300 days (source: Google).

You don't have to use the cheapest, but slowest Hohmann transfer orbit to get to your destination. You can also spend more fuel and get there faster.

A bit of searching suggests that a mildly increased delta-v budget can get your half-year trip down to a quarter-year, but beyond that you're looking at ridiculous costs.
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