My Assistant
Site Message
(Message will auto close in 2 seconds)
  |
 [News] To space, and beyond!, Assorted cool space news |
 Mar 11 2006, 10:56 PM
Post
#26
|
|
|
Free Spirit  Group: Dumpshocked Posts: 3,928 Joined: 26-February 02 From: Bloomington, IN UCAS Member No.: 1,920  |
Anything on the commercial value of Mars? More Helium3?
|
 |
 
|
|
Mar 12 2006, 01:03 AM
Post
#27
|
|||
|
Shadowrun Setting Nerd Group: Banned Posts: 3,632 Joined: 28-June 05 From: Pissing on pedestrians from my electronic ivory tower. Member No.: 7,473 |
Boy, I bet that was embarassing. |
||
|
|
|
||
|
Mar 12 2006, 09:41 PM
Post
#28
|
|||||||||||
|
Running Target Group: Members Posts: 1,428 Joined: 9-June 02 Member No.: 2,860 |
You have to use the same machinery, use the same personnel, and pay for the same mortgage when you bring stuff down the elevator as stuff going up the ladder. So, if there's a difference in electrical bills, I don't think that's going to significantly alter the price of shipping cargo up or down a fancy vertical railroad that might cost trillions of nuyen.
Current global production of steel is in the range of 500 to 1000 million tons per year. That's 0.1 cubic kilometers of steel per year. A metallic asteroid might be 70% or more metal by volume, mostly iron. A 5km diameter asteroid, one with a volume of about 60 cubic kilometers, would have about 40 cubic kilometers of metal, mostly iron. In other words, at the consumption rate of steel (which has been roughly steady for a couple of decades), a 5km metallic asteroid would have enough iron to meet the needs of humanity for 400 years. The other metals present should be good for a similar time scale.
Research. Misguided goals lingering from the 1960s Space Race. If you're going as far as Mars for "practical" (profitable) reasons, you might as well go to the asteroid belt or capture an Earth-crossing asteroid.
The densest form of energy that is wandering about space - near Earth anyway - is sunlight. So solar power satellites, if built, would be big solar cell arrays (photovoltaics). They would then beam the power to Earth by microwaves or lasers. As for being undeveloped tech, it's not undeveloped. Microwave power delivery is proven and almost trivial to manage. It's a non-issue as far as offering road blocks. The bigger problems are: 1) Assembling large structures in space (not demonstated) 2) Maintaining large structures in space (not demonstrated) 3) Building large structures in space cost effectively (unlikely to no-chance in hell) I know SR has SPSs, but the real world economic analyses behind them are usually laughably optimistic and SR doesn't demonstrate the advanced launching systems (like orbital elevators) that might make SPSs cost-competitive with fusion power plants built on the ground (which SR also has). |
||||||||||
|
|
|
||||||||||
|
Mar 12 2006, 10:34 PM
Post
#29
|
|||
|
Midnight Toker Group: Members Posts: 7,686 Joined: 4-July 04 From: Zombie Drop Bear Santa's Workshop Member No.: 6,456 |
There is also the good 'old not keeping all of our eggs in on basket. Move a few million people to Mars and the human race can survive if the arth is destroyed from some unforseeable reason (presuming that Mars isn't destroyed, as well). This is the best and most practical reason for long term space colonization. |
||
|
|
|
||
|
Mar 12 2006, 11:12 PM
Post
#30
|
|||
|
Running Target Group: Members Posts: 1,428 Joined: 9-June 02 Member No.: 2,860 |
It's a practical reason for space colonization, but Mars has an obnoxiously deep gravity well. It's also about as hard to live on Mars as anywhere else in space. And Mars only has about as much elbowroom as Earth's surface. So, if you're going to live in space, you might as well pick some place that supports industry well, is easy to reach, has lots of elbowroom for the mass, and has all the elements you need to live - like the asteroid belt. |
||
|
|
|
||
|
Mar 13 2006, 05:52 AM
Post
#31
|
|||
|
Free Spirit Group: Dumpshocked Posts: 3,928 Joined: 26-February 02 From: Bloomington, IN UCAS Member No.: 1,920 |
Do you mean as compared to an asteroid, or is gravity there somehow not proportionate? Thank you very much for the clarification and answers. I appreciate it very much. |
||
|
|
|
||
|
Mar 13 2006, 01:14 PM
Post
#32
|
|||||
|
Running Target Group: Members Posts: 1,428 Joined: 9-June 02 Member No.: 2,860 |
What I mean by "obnoxiously deep gravity well," is a personal opinion thing. My pet definition is that any vehicle launching from the object needs to be over half fuel by mass (when using realistic chemical fuels) just to reach orbit. Earth's moon is at the low end of "obnoxiously deep" because a launch vehicle needs to be about half fuel by weight to reach orbit. Mars is worse - the vehicle needs to be about 3 parts fuel per part of dry weight and cargo. On the other hand, a launch vehicle operating from even the largest asteroid, Ceres, only needs to be 20% fuel by mass to reach orbit with a generous safety margin and average fuel efficiencies. A vehicle just barely able to reach Martian orbit would be hotrod in the asteroid belt. Communities and industrial facilities in the asteroid belt are like...seaport and river communities on Earth. They have easy access to high-capacity, cheap shipping via barges and gigantic oceangoing ships because it takes almost no effort to transfer cargo from the city to the transport and send the cargo on its way across the world. In comparison, colonies on planets and large moons are like landlocked cities in Alaska or Siberia. You can run train tracks out to them and fly in supplies, but the cost will be painful - compare shipping 70,000 tons of ore on a Great Lakes bulk freighter to shipping 70,000 tons of ore on 747s. |
||||
|
|
|
||||
|
Mar 13 2006, 01:21 PM
Post
#33
|
|
|
Horror Group: Members Posts: 5,322 Joined: 15-June 05 From: BumFuck, New Jersey Member No.: 7,445 |
Cray, you make good points with that bit about obnoxiously deep gravity wells, but then you forget the applications of space elevator technology.
If your vehicles never need to go closer tha orbit, they never need to try and fight a gravity well. (Unless something has gone horribly, horribly awry, but if that happens you're fragged anyway.) |
|
|
|
|
Mar 13 2006, 01:32 PM
Post
#34
|
|||||
|
Running Target Group: Members Posts: 1,428 Joined: 9-June 02 Member No.: 2,860 |
No, I didn't forget them. I dismissed them earlier in the thread as too optimistic. If they're present, life is easier but still not perfect.
That's incorrect. Once you're in Earth orbit, it still takes about as much effort (~3230m/s) to escape Earth's gravity well as it does to reach orbit from Mars' surface. Further, if you use a low thrust means of climbing out of the gravity well (e.g., ion rockets), the required change in velocity is doubled (~6460m/s). Similar situations apply to any astronomical object. Getting to orbit is, energetically speaking, only half way to escape velocity. In terms of velocity, orbit is only 70.7% of the way to escape velocity (for high-impulse rockets). Basically, once you're in orbit the gravity well still has some fight left in it. |
||||
|
|
|
||||
|
Mar 13 2006, 02:10 PM
Post
#35
|
|
|
Horror Group: Members Posts: 5,322 Joined: 15-June 05 From: BumFuck, New Jersey Member No.: 7,445 |
Well, you make good points there...
Still, get creative. With a large, heavy and suffenciently masseous anchorpoint station, you could use a mass driver to give your space vehicles the nessessary push out. Of course, then you'd need some way to correct for the resulting equal and opposite, but... Hey, we're getting creative here. We'll figure something out. Maybe launch a counterweight load straight down at the same time? :) |
|
|
|
|
Mar 13 2006, 02:31 PM
Post
#36
|
|||
|
Running Target Group: Members Posts: 1,428 Joined: 9-June 02 Member No.: 2,860 |
Instead of a compact counterweight on the space elevator, you can just extend the space elevator tens of thousands of kilometers further beyond geosynchronous orbit. The far end of the elevator will be moving well above orbital velocity for that altitude. A spacecraft can be "flung" off the end. The energy for this ejection is taken from Earth's rotation. Alternately, you can use a series of rotating tethers to fling payloads around and reboost the tethers by a variety of means: high efficiency, low thrust engines (SR has some form of fusion rocket, based on the Probe Race fluff); interactions with Earth's magnetic field; braking returning payloads after launching other material; etc. http://www.tethers.com/MXTethers.html |
||
|
|
|
||
|
Mar 13 2006, 03:44 PM
Post
#37
|
|
|
Horror Group: Members Posts: 5,322 Joined: 15-June 05 From: BumFuck, New Jersey Member No.: 7,445 |
Yes, but the thought of firing a huge thor shot down below as a way to faccilitate the launching of spacecraft is funny.
Unless you're a surface dweller. Sux t' be you. |
|
|
|
|
Mar 13 2006, 05:14 PM
Post
#38
|
|
|
Midnight Toker Group: Members Posts: 7,686 Joined: 4-July 04 From: Zombie Drop Bear Santa's Workshop Member No.: 6,456 |
Deep gravity wells are bad for space travel but they're good for humans. Microgravity really messes up the human body even in the short term. If you want a long-term colony then it is best if the colonists don't die young due to microgravity related health complications. Now, artificial gravity could work but not on an asterois. You'd need a self-contained space station designed from the ground up for that.
|
|
|
|
|
Mar 13 2006, 05:33 PM
Post
#39
|
|||
|
Running Target Group: Members Posts: 1,428 Joined: 9-June 02 Member No.: 2,860 |
Artificial gravity works fine on asteroids. There are several options available: **A rail habitat that circles the equator of the habitat, a train of habitats. **A rotating wheel or cylinder built on the surface or in the interior of the asteroid. **The Cole habitats, which melts and inflates the asteroid into a sphere or cylinder that can be rotated for gravity (Cole habitats are crap, though. Atmospheric pressure would blow them apart because of the crappy, impure materials used in their construction.) In higher gravity asteroids, or even on places like the Moon or Mars, you can use rotating habitats. However, the wheel needs to tilt outward a bit so the rotational "gravity" and natural gravity add up to a single gravity vector (i.e., so the floor doesn't seem tilted to occupants.) You end up basically building a spinning space station on the asteroid, which is convenient - there's no shipping to be done, unlike for stations built in open space. Plus, radiation shielding is easy if you build inside the asteroid, and you don't have to worry about finding reaction mass to spin up large rotating habitats. For further gamer-friendly info, I'd recommend picking up GURPS Transhuman Space "In the Well" and "High Frontier." Also, scan to the highlighted words "track" and "habitat" here. There are some diagrams of a rotating track habitat on the asteroid Eros. |
||
|
|
|
||
|
Mar 14 2006, 12:00 AM
Post
#40
|
|
|
Running Target Group: Members Posts: 1,283 Joined: 17-May 05 Member No.: 7,398 |
Or you just spin up the asteroid, and build your habitats so that it look like you'd be 'hanging upside down', but the centrepedal force (which isn't actually a force, but nevermind that) acts like gravity on Earth (and counteracts the Asteroid's gravity).
|
|
|
|
|
Mar 14 2006, 01:13 AM
Post
#41
|
|||
|
Running Target Group: Members Posts: 1,428 Joined: 9-June 02 Member No.: 2,860 |
I really doubt any asteroid could handle 1G of spin. Most seem to be big balls of gravel and dust. Others, even if they're made of solid rock, aren't going to stay together after billions of years of being pounded by meteors and other impactors. All those faults and fractures... |
||
|
|
|
||
|
Mar 14 2006, 06:56 PM
Post
#42
|
|
|
Running Target Group: Members Posts: 1,028 Joined: 9-November 02 From: The Republic of Vermont Member No.: 3,581 |
It's pretty easy to figure the amount of spin that any asteroid that's not a single cohesive chunk of rock can take... when the centrifugal force* produced by the spin exceeds the surface gravity of the asteroid, the asteroid will start coming apart. This basically means that the maximum artificial gravity you can produce by spinning an asteroid is equal to its natural gravity, which pretty much makes spinning it up a waste of time and energy.
* (Yes, I know there's No Such Thing As Centrifugal Force. That doesn't make it a less useful tool in practice.) |
|
|
|
|
Mar 14 2006, 07:12 PM
Post
#43
|
|
|
Running Target Group: Members Posts: 1,428 Joined: 9-June 02 Member No.: 2,860 |
Nitpick: Some small, solid objects have been found in environments that should pull them apart. For example, Metis and Adrastea orbit inside Jupiter's Roche limit, where tidal forces should overcome gravity. So material strength matters a little, but you're not going to get near 1G by spinning an asteroid.
|
|
|
|
|
Mar 14 2006, 08:55 PM
Post
#44
|
|
|
Incertum est quo loco te mors expectet; Group: Dumpshocked Posts: 6,546 Joined: 24-October 03 From: DeeCee, U.S. Member No.: 5,760 |
As an aside, if the asteroid is made of mostly iron, wouldn't it be possible to use that iron to reinforce the 'exterior' wall of two asteroids, then join them together so they spin around a common axis? If it's only five miles across and you have two teams working on two asteroids (or more), it seems like you have all the ingredients you need to make a cheap solution to the lack of gravity.
|
|
|
|
|
Mar 14 2006, 10:04 PM
Post
#45
|
|
|
Running Target Group: Members Posts: 1,028 Joined: 9-November 02 From: The Republic of Vermont Member No.: 3,581 |
When you drop all the unnecessarily difficult bits out of that plan, it basically becomes, "Build a space station out of asteroidal materials," which is a perfectly feasible solution.
Having the entire asteroid under significant acceleration is probably counterproductive, anyway. Microgravity is a net benefit for a lot of processes, and for the ones that it's not, you can use smaller centrifuges to provide "gravity"-on-demand without (e.g.) making it a pain in the ass to drag a kiloton of ore around. |
|
|
|
|
Mar 15 2006, 01:34 AM
Post
#46
|
|||
|
Running Target Group: Members Posts: 1,428 Joined: 9-June 02 Member No.: 2,860 |
Spinning a couple of mountain-sized wads of dirty, stone-laden metal up to 1G is begging for trouble. Less trouble than a typical stony asteroid, let alone a dust ball, but it's a lot of effort and energy that isn't necessary. You're looking at creep problems, the iron flowing like taffy under its own incredible weight, nevermind the anchors and tethers that join the spheres together. Each 5-mile diameter ball of iron and rock (at about 6g/cc) is about 2 trillion tons. Spinning that up to 1G would take a lot of energy (nevermind the epic engineering challenges of spinning 4 trillion tons at 1G) that isn't needed. As John pointed out...why not just build a space station out of the asteroid material? The frame of a 2km diameter toroidal station can be about 10,000 tons, comparable with a small oceangoing ship. |
||
|
|
|
||
|
May 6 2006, 12:36 PM
Post
#47
|
|||||
|
Shooting Target Group: Members Posts: 1,635 Joined: 27-November 05 Member No.: 8,006 |
raises the dead I just came across this article about the physical chemistry experiements I mentioned a couple months back. That is likely the basis for what those kooks on Coast to Coast were talking about. Although I find quite dubious this claim about calculations not being able to account for all the hydrocarbons accessed and used, this article again mentions the small known deposits of methane that appear to be abiogenic.
As for how water gets down that far, marble is the metamorphic form of limestone which is a sedimentary rock. Meaning it was in the presence of water at one time and often it still has water in it's vugs, the small version of limestone caves. Since the normal source for limestone is marine life, shells and coral, I'm not sure exactly how that rock is down that far, it must be very, very early sedimentary rock and just has billions of years of rock piled on top of it. I don't really know of any other source of limestone other than marine life, but then again I don't have a geology degree. I'll try ask around with geologists and paleontologist I know. If it is marine life sourced it might also contain biological source methane as well as abiogenc methane. |
||||
|
|
|
||||
|
May 6 2006, 02:39 PM
Post
#48
|
|
|
Running Target Group: Members Posts: 1,428 Joined: 9-June 02 Member No.: 2,860 |
Interesting stuff. Thanks for posting it.
|
|
|
|
|
May 6 2006, 03:01 PM
Post
#49
|
|||
|
Moving Target Group: Members Posts: 903 Joined: 7-February 03 Member No.: 4,025 |
I thought that was a mistake at first. Now I'm not sure.... There's a really good description of a space elevator in Kim Stanley Robinson's Red Mars series. So Cray, Mars has two moons, but you mentioned that it "wobbles" a lot more than earth. Because it's closer to Jupiter, or because its moons are too small? (BTW: Do you work or study in the field? I'd like to refer to some of what you said, but I'd like to know who I'm referring to.) Another thing I read is that the fanciful elevator would have to be built on or near the equator. So, if anyone's going to use a space-elevator project in their game, there's bound to be some political considerations. |
||
|
|
|
||
|
May 6 2006, 07:47 PM
Post
#50
|
|
|
Target Group: Members Posts: 72 Joined: 26-February 02 From: Oak Ridge, TN, CAS Member No.: 407 |
I don't know if it's been mentioned, but there was a book titled Mining The Sky that covered this concept. My brothers (who tend to follow things like science and econimics) claimed that the author had No Friggin' Clue™ what sort of staggering costs this endeavor would require.
|
|
|
|
|
|
Lo-Fi Version | Time is now: 12th April 2022 - 10:44 AM |
Topps, Inc has sole ownership of the names, logo, artwork, marks, photographs, sounds, audio, video and/or any proprietary material used in connection with the game Shadowrun. Topps, Inc has granted permission to the Dumpshock Forums to use such names, logos, artwork, marks and/or any proprietary materials for promotional and informational purposes on its website but does not endorse, and is not affiliated with the Dumpshock Forums in any official capacity whatsoever.