Okay, I stand corrected. They don't often use liquid oxygen in hospitals.<br />===================<br />I stand corrected again, it's a lot more common than I had realised. It's still not the preferred method, but for people on long-term oxygen therapy, it's a option. The advantage, as you point out, is that you can cram a lot of oxygen into a small space that way. The disadvantage is that if the pressure of oxygen boiling off isn't relieved properly the tank develop many thousands of psi and explode.
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A lot of hospitals have on site liquification systems. They liquify air and distill out the Oxygen just like an oil refinery separates oil into it's components by their vapor points. A lot are in parking areas so they can't be too dangerous.<br /><br />For the foreseeable future Oxygen and Hydrogen are the best sources of energy available to us. The technology to produce Hydrogen and Oxygen is also long established, proven and commercially available. <br /><br />The problem becomes containing LH and LOX, getting it to orbit and storing it, basically the same problem as with any propellant we need to take, but a little more involved. The insulation mass of containers needed being a prime example. LH, LOX, powered launchers vent until just before launch to keep internal pressure under control and then use the propellant rapidly, lessening the thermal containment requirements. Shuttle carries LOX tanks and I believe a few survived relatively intact from the Columbia loss, an example of their structural requirements as well as their shapes. <br /><br />Once in LEO containment becomes simpler, because Solar power can be used to keep LH and LOX liquified, pressures can be kept in check and boil-off reliquified, near vacuum in LEO also simplifies insulation needs and a allows a lighter structure. Solar power can be used to produce LH and LOX, from water, probably the first thing humans learned to contain and transport, and also the most benign substance to carry in the event of a launch failure. <br /><br />It took the Saturn V to get three people to the Moon, it's ridiculous to talk about a one shot launcher that would allow meaningful operation at the Moon to be launched direct. The only feasible method is an assembly station in LEO and a dedicated transfer vehicle to move from LEO to Lunar orbit. Passengers and Payload would be brought up as needed and loaded into the waiting vehicle. Propellant, LH and LOX, would be produced at the station and loaded as needed.<br /><br /> <div class="Discussion_UserSignature"> </div>
Naj-<br />For what it's worth, many Navy aircraft, from F-14 Tomcats to C-9 type airliners use LOX instead of High Pressure Gas for breathing Oxygen. I was always scared when I worked with the stuff. But just like fuel lines are shrouded to vent safely overboard incase of leaks, LOX could be, too. Yes, it is mean stuff, not only does it want to rapidly burn everything that could possibly burn, but it expands several thousand to one when it changes from a liquid to a gas, which is also dangerous.<br /><br />However, I still can't believe it's a "show-stopper", like it has been for the past 20 years in the Shuttle Program. But even if it is just too dangerous to fly liquid payloads in the bay, there has got to be a "good" way to put a little extra fuel/LOX in the ET, and get that into a fairly stable orbit for a few days. I don't know how much deltaV is required by that OMS burn right after ET seperation, but I would guess that we could "bump freight for fuel", in other words, leave some freight and carry extra fuel. It wouldn't be the most efficient way because the weight of the tank itself has got to be pretty heavy, plus the fuel/LOX inside, but it would keep the Orbiter's payload bay "dry". Plus the SSME's would do the boosting all the way to orbit, but maybe the OMS are used because they can be more precise, I don't know.<br /><br />I'll bet dollars to pesos there is a good way to do it. <div class="Discussion_UserSignature"> </div>
><i>A lot are in parking area so they can't be too dangerous. </i><p>You've no idea how much that idea scares me. If there's one thing you don't want a liquid oxygen spill around, it's hydrocarbons (asphalt, grease, oil, etc). The reaction of the two meeting can be pretty spectacular, it doesn't even take a spark to ignite - simply dropping something can start a flash fire.</p>
I doubt it would be a problem. It vents rapidly upward.<br /><br />I know the hospital in our neighborhood in Washington had theirs sitting on the corner by the emergency room, the driveway was on one side and a small grass area between the generator and the building. <div class="Discussion_UserSignature"> </div>
><i>I doubt it would be a problem. It vents rapidly upward.</i><p>Dragging this thread even further off topic, that's exactly the problem. It doesn't.<p>Oxygen is the heavy quarter of air (molecular mass 32), nitrogen is the lighter three quarters (molecular mass 28). An oxygen spill tends to stay close to the ground until it's blown away by air movement or it <b>slowly</b> diffuses.</p></p>
Okay. I admit it, there isn't any good technical reason why you couldn't launch liquid fueled rockets in the Shuttle. The thought of tanks of LOX and LH2 in the payload bay being shaken halfway to nowhere during stage one flight (or, god-forbid, during an RTLS) just scares the bejesus out of me, that's all.
Naj-<br />A LOX spill in a typical parking lot would scare me, too. On my ship, there was an Engineer who stepped in a puddle of LOX with grease on his shoe, after the fire fighters put out out the extremely hot fire, they realized they had been standing on the guy, what was left of him. It happened about a year before I got onboard.<br /><br /><i>USS INDEPENDENCE (CV 62), Class A Fire/AM1D LOX Shop, August 1991</i><br />http://www.dcfp.navy.mil/mc/museum/casualties.htm <br /><br />*EDIT*<br />Edit for speeling <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> </div>
Remember that a version of the Centaur was built for the shuttle, but I don't think it ever flew.<br /><br />The Centaur (RL-10 engine) is LOX/LH2. (And a favorite of Henry Spencer to be sure 
<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything." Admiral Jackie Fisher</p> </div>
<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything." Admiral Jackie Fisher</p> </div>On an unrelated note of perhaps sick humor - I remember ClF5 being given as an example of a nast oxidizer where the definition of nasty was given as<br /><br />"A material known to be hypergolic with just about anything you would think of using to put it out with."<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything." Admiral Jackie Fisher</p> </div>
Thats why you use it as propellant for the launcher but take it to LEO as water. Much safer. <div class="Discussion_UserSignature"> </div>
Scottb50:<br /><br />Water is inert, and inert is certainly safer to transport, but it’s not that easy to crack water into LOX and LH especially in a LEO environment. <br /> <div class="Discussion_UserSignature"> </div>
I don't think it makes a lot of difference whether you are in zero G or not. A little pressure and permeable membranes goes a long way. <br /><br />By the way a fuel cell is the same thing as a hydrolizer, just reversed and they work just fine. <div class="Discussion_UserSignature"> </div>
><i>I don't think it makes a lot of difference whether you are in zero G or not. A little pressure and permeable membranes goes a long way.</i><p>The ongoing and current problems with the Elektron system put that evaluation in doubt. Not that it is impossible, but it isn't necessarily as easy as it might seem.</p>
If you take water to LEO in order to produce oxygen/hydrogen there, then what's the point in trying to contain it liquified cryogenically instead of geseous? Seems a lot easier and you can simply produce it when you need it and not before.<br /><br />Teije
There are a few possible reasons. The actual reasons would depend on the particular mission -- there always tradeoffs for any approach, after all.<br /><br />* Water is easy to handle. But it freezes at a relatively high temperature (compared to oxygen and hydrogen) and that means that in space you're going to have to keep it warm in order to pipe it around.<br /><br />* The equipment for separating and liquifying oxygen and hydrogen is bulky. It may impart a substantial mass penalty on your spacecraft if you have to bring that up as well as the fuel.<br /><br />Personally, I think separating water into hydrogen and oxygen on orbit would be most practical for the following cases:<br /><br />1) Recycling materials for a fuel cell. The Shuttle, for instance, converts oxygen and hydrogen into water to produce electricity. This water is potable, which means the Shuttle never has to bring up water; it always has more than enough, because it's constantly making it.<br /><br />2) Mining offworld ice. This is extremely long term, and would not be practical for a lunar shot. But in the distant future, perhaps we will be getting water from comets, or Europa, or other icy worlds to fuel spacecraft. It's not practical in the immediate future, but I think that someday it might be. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em> -- The Tenth Doctor, "Blink"</font></p> </div>
I linked to this thread from my site, however I would rather link to a thread titled The Earth, The Moon, Then Mars... or something to that affect.<br /><br />I for one, would like to see a international base on the moon within my lifetime, and I want to do what can to make sure this happens...<br /><br />I think the main problem with accomplishing this goal is financing, and I am determined to find a way to fund a robust program...<br /><br />All we need to do is find a few million people that are willing to autodraft $25 per month. This will generate 1.25-billion per month, or 15-billion per year, which is almost as much NASA's 2005 budget proposal.<br /><br />But still that is only 300-billion in 10-years combined, which is only about 25% of the total funds we will need. This is why it is critical that we make this an intenational effort, because I really think it will cost more that a trillion dollars over a twenty-year period to make this goal.<br /><br />What do you think?<br /><br />http://jatslo.com/ : Jatslo
Because the volume needed would require huge containers if you were keeping it a gas. Keeping it liquid in Space would also be fairly simple the insulation would basically be sunlight shielding.<br /><br />Having the capability of producing it as needed could allow for more economical and safer storage though. It would even be possible to set up a supply depot in Lunar, or Mars orbit, for that matter, transport water and refuel the vehicle for return, that would lower the energy needed to leave Earth orbit for cargo and passenger transits. Then it becomes a matter of which is more economical, transporting the equipment and water to Lunar orbit or containing round trip supplies. <br /><br /> <div class="Discussion_UserSignature"> </div>
rogers_buck,<br />Something similar, but using RS-68's was proposed awhile back. That way a reentry capsule would not need to be developed, at least up front. With a single SSME upper stage, over 160 tons could be lifted. Even at .5 billion you get a decent price per pound.
I doubt the problems with Elektron have as much to do with the operating environment as the age of the unit and the operation it performs. Elektron is basically a sewage plant and dumps rather corrosive waste overboard, from yesterdays observations it appears the main problem may be restricted vents as much as anything else. <br /><br />As for being easy, their are a great many hydrolizers available, from small desktop demonstrators to huge industrial versions.<br /><br />http://media.nasaexplores.com/lessons/01-009/5-8_3.pdf<br /><br />http://www.fuelcellstore.com/information/how_fuelcells_work.htm<br /><br />http://www.goodideacreative.com/shfc_sys.html<br /><br />http://minihydrogen.com/catalog/index.php?cPath=42&osCsid=8cb7bf435560f0615a4ed4f6aba75feb<br /><br />http://www.dangerouslaboratories.org/h2homesystem.pdf<br /><br /> <div class="Discussion_UserSignature"> </div>
><i>Elektron is basically a sewage plant...</i><p>You <b>do</b> know what Elektron is, right?<p>><i>I doubt the problems with Elektron have as much to do with the operating environment as the age of the unit...</i><p>I'm speaking subject to correction here, but I believe the currently operating Elektron unit was flown up on either the most recent Progress flight, or the one before.</p></p></p>
In a space environment, wouldn’t it require too much energy to keep water as a liquid? I guess we could regulate the radiant energy of the sun or we could keep it frozen and melt off only what is needed when it’s needed. <br /><br />It still takes time, effort, energy & very specialized equipment to convert water to LOX and LH2. If it were an easy process, we would all be filling our gas tanks with water and running our vehicles on hydrogen. <br /><br />Keeping the resources in one place might be a future consideration. It would be like a gas station parked between the earth and the moon. I don’t see it as practical. It would take too much energy to slow down and accelerate again. I perceive it to be more like a KC135 tanker in orbit. <br /><br />What would be really nifty is lassoing a small comet and dragging it into orbit around the earth where we can feed off of it. <br /> <div class="Discussion_UserSignature"> </div>
" Keeping the resources in one place might be a future consideration. It would be like a gas station parked between the earth and the moon. I don’t see it as practical. It would take too much energy to slow down and accelerate again. I perceive it to be more like a KC135 tanker in orbit. "<br /><br />It seems more practical to have Three service stations; one in orbit around the Earth; one in orbit around the Moon, and the other in orbit around Mars.<br /><br />Then it would be a matter of docking, rather than expending fuel to slow down and excelerate.<br /><br />http://jatslo.com/ : Jatslo
It would make economical since to manufacture fuel from The Earth, The Moon, and Mars... If this involves nuclear power plant thermal cracking for each planetary body, maybe then, we should also think of the terraforming potential of nuclear power plants...<br /><br />It has been a vision of science fiction writers for a long time, but terraforming - the art of making a planet habitable for humans - is fast becoming serious business.<br /><br />It may seem a strange choice to invest human resources on making other planets habitable, while we are on a fast track to devastating our own.<br /><br />But, considering that we have yet to set foot an another planet, dreaming about creating new homeworlds may be a good way to learn how to engineer our own climate better. Terraforming is a science which demands great knowledge about biology, chemistry, ecology and geology - and almost any other science you choose.<br /><br />By studying the possibilities for terraforming The Moon and Mars, our closest neighbors, we may in fact learn how to counteract global warming and other effects of our harsh treatment of the environment.<br /><br />http://jatslo.com/ : Jatslo <br />
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