Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[Starver]

They weren't aiming for a Herge-esque landing, aiming straight at the Moon and then turning round to perform a tail-sitting landing after a completely non-orbital approach. They had the fortunate wiggle-room of a free-return orbit available, from their trajectory that was always intended to bend round the side.

Probably less difficult, saving for the new need to rely on unplanned/ad hoc manual control, than the planned orbital insertion would have been.

They 'just' had to make sure their slingshot sent them back to Earth, not into solar orbit. Which was somewhat crucial, I'll admit.

[Reelya]

I figured you were talking about Venus, though I missed that it's only the upper atmosphere which rotates quickly, the lower atmosphere doesn't move anywhere nearly as much.

Fortunately "only" the upper atmosphere has about 1 G gravity and 1 atmosphere pressure, and reasonable temperature. So you could float a large habitat up there and have it move with the winds, getting a day/night cycle.

Maybe we can send Trump. He can be used as the lift source.

[Starver]

Actually looked to confirm things.

Apollos 8-11 used free-return trans-lunar orbits (with aimed-for Earth re-entry as part of the first cycle) for safety reasons, inserting into lunar orbit at the appropriate point, then out again once the desired orbits/landing were achieved.

Apollos 12+ then switched to using 'free-return-to-Earth' (sub-lunar, perigee low enough for re-entry) orbits that were then boosted to (non-free-return) trajectories for trans-lunar and then (planned!) lunar-insertion adjustment.  13 seemed to be past the first stage, when they had "a problem" and then had to retune the trans-lunar into a free-return to Earth (that ended up aiming at an Indian Ocean splashdown) which was then further modified such that it both reduced the return time and re-aimed at the Pacific.

Can't get definitive details of the delta-V differences between the planned insertion and unplanned return maneuvers, though, at first glance.

[Max™]

Maybe we can send Trump. He can be used as the lift source.

That is the smartest thing I've ever heard anybody say since I saw a friend of mine tell one of his sisters friends that he would happily give her shirt back in exchange for her bra.

[WillowLuman]

No political cheap-shots, please.

[Max™]

Her career in politics was doomed from the start, to be fair...

[WillowLuman]

That goes for you too. Don't start this crap on my thread, please.

[LordBaal]

Well yeah? We are gonna build our own space thread with blackjack and hookers.
In fact forget the thread!

Now. On topic. Which are the real, real implications of a space economy as currently proposed. I mean legally. Also which are the real motivators behind, besides turism and maybe a few rare elements from the moon. I'm talking about the moon.

[Reelya]

https://yro.slashdot.org/story/17/03/01/0416232/congressional-candidate-brianna-wu-claims-moon-colonizing-companies-could-destroy-cities-by-dropping-rocks

Brianna Wu is running for Congress and warning about orbital bombardment with moon rocks. Which is pretty much the entire plot of The Moon Is A Harsh Mistress.

[Starver]

It's the stealthy redirection of asteroids that we need to look out for.  So many places they can come from, and it would be trivial to reduce their optical/radar signatures as they head onto their new Earth-intercepting solar orbit.  And the perpetrators (who have the capability to do all this) can so easily hop between multiple asteroids for aiming or additional raw materials and arrange for a multi-shot attack to be initiated before the first detection (or impact, if it takes that long) is made.

[sluissa]

Well yeah? We are gonna build our own space thread with blackjack and hookers.
In fact forget the thread!

Now. On topic. Which are the real, real implications of a space economy as currently proposed. I mean legally. Also which are the real motivators behind, besides turism and maybe a few rare elements from the moon. I'm talking about the moon.

The moon would be an excellent place to build/launch spacecraft from if we could get manufacturing set up there. It's fairly difficult to launch anything large from the earth because of the gravity and atmosphere. The moon only has the gravity to deal with and only 1/6 of it, but if it gets to the point where we only need to launch crew with about a week of supplies (like Spacex is planning to do next year, at a cost less than half the cost of a single shuttle launch. (only about 15% the cost of a shuttle launch if you divide total cost of the program by number of launches, but that comparison is just a BIT unfair) then that opens up a lot more options. Space stations built and launched from the moon and moved into low earth orbit to be crewed by launches from the earth. Large, science fiction scale interplanetary ships built and launched from the moon.

[Culise]

But then, why launch from the Moon instead of constructing your sci-fi scale interplanetary ships in orbital space directly?  On the Moon, you're still sitting at the bottom of a significant gravity well, but you don't have enough gravity to actually ensure the health of your local workers without additional measures.  You don't have the mineral resources of Earth, and you can't tap a convenient NEO that may have the heavy elements you need in abundant supply much more easily on the Moon than you could on Earth.  You also get to worry about that lovely sharp lunar dust getting into everything; your entire construction area needs to be safed against it unless you want to worry about damaged gaskets, sealing, wires, fine lenses, and so forth. 

EDIT:
Ah, at any rate, my own thoughts.  I see the moon being primarily a resource-extraction industry at the very most, albeit one primarily focused on relatively light elements: helium-3, oxygen, water, and (on the heavier side) aluminum and maybe iron.  It's generally believed that short of a trip out to the outer planets, the Moon is the most convenient source of helium-3 in the inner system.  This, however, requires effective cold-fusion to make any use of ³He; most present uses for the isotope aren't really worth the cost of going to the Moon and back.  Even as a power source, it's questionable if it's worth the cost.  A space economy is likely going to be centralized in Earth orbit with possible occasional forays to near-Earth objects or even the asteroid belt for the foreseeable future.  While resource extraction is going to be major due to the wealth of accessible resources available in certain types of asteroids, zero-G manufacturing does have significant promise.  Power generation is also a possibility: without gravity, tremendous solar arrays can be constructed without the structural support necessary on Earth, and without occlusion by weather or the planet itself, can operate continuously, but the question then becomes if efficiency losses from power transmission from orbit to the ground outweigh this. 

[Strife26]

You can dig underground on the moon. The biggest risk for significant times off of earth is radiation and the most cost efficient way to deal with radiation threat is to dig deep. Lunarcrete is cheap because it's in situ.

[MetalSlimeHunt]

What would be nice is if we could get around to testing centrifugal beds. If that allows indefinite maintenance of bone and muscle density a lot of problems suddenly evaporate.

[Starver]

They're already trying that idea, in a roundabout way...