I imagine that any association with the US Govt. could engender distrust in such matters these (post Snowden) days.
It might engender quantitatively more distrust than in pre-Snowden days, but probably not deeper distrust. The US government has been deeply distrusted by the rest of the world for a long time.
but would it kill Microsoft to change the default behaviour to something more sensible (this can hadly be the only use case where this is an issue)
Science users with thousands of rows of data are a negligible market compared to beancounter-wannabes with a dozen (or maybe even up to 5 dozen) rows of data. So, to answer your question, yes it would kill Microsoft to change the default from behaviour that covers up common wannabe-beancounters errors.
Oh, the fuck-wittery of working round Excel v5 bugs like this to deal with combining hundreds of thousands of lines of data throughout the 1990s. And 2000s. And 2010s. And you an guess what I anticipate fucking with in the 2020s.
Why do astronomers use irregular units like "light years" and "parsecs"
I can't remember the last time I read an astronomy paper (NB : paper, not regurgitated shit in the popular press) which didn't use parsecs and/or AU as the primary description of astronomical distance (with , M-Earth and M-Sol in the mix). For parsecs, the reason is simple : what you measure when establishing distances is parallax, in seconds of arc. Hence PAR-SEC. No?
If converting to metres, then you need to factor in your estimate for the AU, but you only do that conversion when editing the final draft of the paper and the press release You do your working in parsecs. And if the estimate for the length of the AU in metres changes between your observatory time and publication date, then only that derived figure in metres (miles, Egyptian cubits, or whatever) changes NONE of your working or your experimental data changes.
Similar arguments apply to the masses and the AU. You can directly observe e.g. the timing of events in an eclipsing binary (in seconds or days after the start of your epoch of observation), and if you work in units of AU, M-Sol and M-Earth then you get your orbital parameters from those raw observations and Kepler's laws with no conversion factors. You only do the conversions for the proof copy of the paper - possibly not even for the initial copy to go to peer review.
Actually, I remember when the change to a speed-of-light based definition of the second came out, replaing the outmoded definition based on the hyperfine transition of blah-de-blah. It was in the mid-1980s and I was reading the commentary in 'Nature' in the library.
Not an "arbitrary substance", but (1) the most common "substance" in the universe by volume, and (2) probably the simplest "substance" in the universe.
(1) and (2) are probably related, but that's way above my pay grade.
It's also quite a hard substance to get access to without space flight.
Patel argues that when we grow reliant on self-driving cars, things will get far more complicated and futile if we don't make our maps and navigation services better.
No, Mr Patel, a significant number of your potential market/ audience will not become reliant on your product until after map and navigation services are better.
And incidentally, some of us are used to spending time where you don't have electrical power or any mobile phone/ data signal (Iridium excepted, all 9600 bps of it) , and the magnetic field is sufficiently variable that your compass is decidedly dodgy. We carry multiple different location-determining technologies that won't be disabled by simply running out of battery life. Because, that like kills people, you know?
so if you just went with the slashdot summary and quote
Haven't people learned to not fucking well do that by now? I mean the site has been going for what - nearly 20 years. There are account holders out there who're legally able to buy booze - drugs in some countries - and who were born after the site was set up. And still there are people fucking stupid enough to only read half TFS and none of TFA.
People wonder why many western nations have problems getting appropriate technical staff, and then they behave in such a stupid mannner. And don't see the connection?
As for the recovery procedures - well with a low-6-digit UID, you were probably around when they recovered SOHO from a similar orientation-power problem. Which doesn't make it any easier (space craft are different; locations are different ; latencies are different ; command sets are different), but it is a task that has been done before. And we've seen it (as have the mission managers at NASA).
If you need reaction mass, possibly material for making rocket fuel, non-volatile comet debris for soil and radiation shielding (*), the first place you'd move them to is "near earth". Not directly to LEO though - the cost of moving water or tanks between LEO and (say) Earth-Moon L2 or L3 is far lower than the cost of moving the same mass of water from Earth's surface to LEO. Of course, you'd have a staging area in space (three degrees of freedom) and velocity (another 4 degrees of freedom) for delivery of the dirty snowballs. The precise orbital details vary from comet to comet (or asteroid to asteroid - they're a continuum. See recent discoveries from the Dawn spacecraft.), but you can plot courses from "there" to "here" which use an interaction (or several) with the Moon to minimise the necessary delta-vee, and those lead to the incoming objects congregating around the L2, L3 points. The details change from orbital object to orbital object.
Scatter-gunning LEO without any planning - in exactly the casual way that NASA does at the moment - with comets launched randomly from the snow line, is likely to end badly for someone. But some of these NASA boffins are using a controversial new theory from some English alchemist called "Newton" (obviously an Apple fanboi), and they claim they can plan orbital transfers in considerable detail. Which is stupid, because that would imply that we'd know if the Sun was going to rise tomorrow, or whether a dirtball 7 light-hours away was going to occult a particular star years, before the event.
(*) all of these are things which will be needed, in abundance, for humankind to have any long term (say 100kyr +) future in space. Given the geological record, that duration would have around a 5% chance of having a km-scale object impacting the Earth.
I doubt they'd be rated, after the stresses of launch, for long-term habitation,
Is anything at all "rated" for long term habitation in space. You'd never get the physical ailments consequent on a 6-month spaceflight past any industrial safety laws. Seriously, not.
but there's going to be ample need for the bulk storage of mass.
You've gone from step 1 to step 100 without showing any of your intermediate working. This blank assertion does not convince me. Would you fill in a few of the steps by which you arrived at that assertion.
perfectly good organics and mass that might be someday useful in orbit, [...] Then the containers themselves could be used as raw material for some hypothetical future process.
Hmm. "GIGO". Not "garbage in, garbage out," but "getting it in and getting it out". Unless you're *only* talking about sewage. But having had to unblock the family shitter more than a few times after the sister blocked it with nappies (EN_US : diapers), I don't relish that task in zero-g. "Who'd use diapers?" I hear you say. Well, having friend who are saturation divers, and never once having heard someone on a spacewalk tell ground control that they need to go inside for a shit... I think that every EVA, particularly the 6-, 7-, 10- hour ones has generated a moist nappy, and probably one full of shit.
Tanks are good for getting liquids and gasses in and out ; for pastes and solids, not so good.
Also, for long term storage, you're either going to need a gas venting system (in which case you've got a rocket effect which you've got to control... more complications) or you're going to need to mix "biocide" with it in appropriate amounts. Then, when you want to re-use it (e.g. to manure your eating plants) you need to neutralise the biocide before it kills your carefully maintained microbiological environment.
What is that "zeroth law of science"? Oh yes, "It's not as simple as that."
It costs energy to move heat.
Expending energy generates heat.
Moving heat generates heat.
Condensed version of the Laws of Thermodynamics : you can't win ; you can't break even ; you can't stop playing ; absolutely everything is subject to the Laws of Thermodynamics, including specifically anyone who objects to the tyranny of the Laws of Thermodynamics.
You're probably thinking of things like hydrazine, or some of the hypergolic mixtures. (A and B are "hypergolic" if mixing A and B results in explosion in milliseconds without needing any initiator, detonator etc. Very good if you want your motor to re-start reliably. The explosion delay is an important characteristic. Milliseconds matter.)
The main fuel in the Centaur stages under discussion are liquid hydrogen ("LH2") and liquid oxygen ("LOX"), but the reliable re-ignition of the engine is controlled by what they refer to as "hypergolic cartridges" - see the engine schematic on page 377 of the Atlas (RT)FM.
Whatever hypergolic mix they use, you don't want to get that shit mixed up with your "intimate lubricant".
If you're doing the (larger) hydrogen tank, how 100% sure are you that you're not making an explosive fuel-air mixture, given that hydrogen burns at just a couple percentage concentration?
Well, for the actual system they're considering, it's the larger (volumetrically) part of a single tank, the LH2 and LOX being separated by a "fibreglass honeycomb", which I guess is glued in place after welding together the bottom end of the tank and the main length of the tank body, but before welding on the top end. I'm not sure whether the LOX is in the upper or lower part of the tank.
Unlike most people here (and I think you and I have discussed this before), I've worked with hydrogen gas too (in analytical instruments), so I appreciate what you're saying about it's flammable limits. What I'm wondering is - with relatively minor modifications to the tank's structure, would it be workable to get rid of the dregs of the fuel by pumping O2(g) into the H2(g) headspace of the tank and lighting a flame of O2 burning in hydrogen. So you approach the UEL of [H2] from the other end, and you have your oxygen going into a mix of H2(g) and H2O(g). Any water that condenses out is uninteresting from an explosion safety point of view. For maintaining the desired pressures in the tank, you'd need an inert pressurising gas - N2 being where I'd start from (might need He for thermal reasons ; meh).
Plan B might be to install a mixing fan into the H2 tank which was covered in Pt-coated wire wool, and to use that to agitate the gaseous contents of the H2 tank, again while bleeding in O2. Monitor tank temperature (Pt-resistance wire as in a kathaometer, perhaps ; kill two stones with one bird?) as the Pt assists the reaction ; if it gets too warm, turn off the O2 supply and let some of the water condense out. Again, make efforts to avoid ever having an atmosphere in the tank that isn't a mix of H2(g) and H2O(g).
I bet the procedures for filling a newly-made tank with it's first charge of LH2 are a real fun read. I don't recall anything about it in "Ignition!" - but that concentrated more on exciting fuels like red-fuming nitric and the "mythical monoprop" and less on dull, pedestrian fuels like LH2/LOX.
I'm tempted to change my signature to :
'monopropellant' is an anagram of 'explosive' for all important meanings of "Kaboom!"
If the tank is in low orbit then gas can be concentrated and blown to the bottom of the tank and allowed to escape from the top.
Even in low orbit (i.e., where the drag is sufficient to de-orbit the tank within a couple of years), you're still in what on Earth would be considered a really hard vacuum.
Your reasoning leading up to "we're going to have to master welding in space" is?
You may be right. But I don't see it as automatically being the case that welding would automatically be stronger, quicker, cheaper or more effective than, say, gluing. We do have some pretty effective glues, for example, and in space, you don't have an oxide or moisture film forming after you abrade the surfaces to join.
'cos getting water into LEO is going to be so easy.
A fair enough point. Of course, getting water from the asteroid belt isn't likely to be free either. But if only there were some other reason for learning how to move overgrown dirty snowballs around in space... like the dinosaurs didn't.
(No, it's not certain that the Chicxulub impactor did for the non-avian dinosaurs - see signature ; I've been following Gerta Keller's work for over a decade - but it sure as hell wasn't a good day for anyone on the planet. Really, knowing - by having done it - how to move multi-kilometre natural objects around in space would be a damned useful skill for a species with a desire to see the distant future. If you're American, you could spend an educational day wandering around in the desert 20-odd miles W of Winslow, Arizona picking lumps of nickel-iron out of the ground and waiting for the 10 megaton energy release. Actually, at 10 megatons, it wouldn't matter much if you walked around in the desert, or sat in a diner in Winslow. Bad hair day, either way.)
[Searches toolbox] "Nobody sent us a hammer!" [Radio to mission control] "Can you send up a hammer in the next tool shipment." [Mission control] "No. Next question?"
Seriously, [Myself on an oil rig 3km above the Atlantic mud, off the African coast] : "Your equipment is giving suspicious results. Pass me your multimeter so I can check if it's working properly."
[Service company rep.] "Our office will only send out a multimeter if it is accompanied by a technician. Technician visits requested by the client are billed at $1500/day."
[Self leaves problem on the table. Returns to office. On night shift with junior service company rep on duty, I take out my multimeter, teach him how his equipment works and how to fix the problem. Next morning, senior service company rep is annoyed and his Boss onshore is furious at losing $5000-9000 of technician fees. Client (who hired me) is happy at not paying the fees.]
or punctures it with a micrometeor,
See my comment upthread about coating the outside with ice bags (sorry - Slashdot-ism : "frosty piss bags"). They won't stop all meteorites, but will certainly stop a lot of them. While also providing both thermal and radiation insulation.
We live at the bottom of an atmosphere approximately equivalent to 10m of (liquid) water, and are evolved to handle that level of radiation. Every mm of water (or equivalent) that we can put outside the space habitat helps towards the goal of radiation dose management.
And finally, if it "dies" for some reason the only loss is money -- no grieving relatives or national flag at half mast.
Grieved though I am when one of my colleagues is killed at work (only a couple dead this year), I've yet to see a case in which any flags went to half mast. Besides, whose flag would you lower? The worker's nationality? Their country of origin? Their cultural identity? Their employer's nationality? The ISS's (or other vessel) "flag of convenience" for insurance purposes (I assume that like every other American vessel I've been on, the ISS is flagged in either Panama or Liberia for tax reasons. And the crew are 30% American, 70% Filipeno? For wage packet reasons.)
50's sci-fi style rotating space station at a lagrange point or in geosync orbit and sending people up to LIVE there
But, but, but, that would involve learning how to live in an environment without polluting it. We can't do that - it'd pander to the global warming socialist conspiracy to even consider the possibility of having to pay attention to the environment.
Seriously - seeing all the problems consequent on trying to live in microgravity, one very obvious answer is the old "Doctor! doctor!" joke :
Patient : "Doctor, doctor! It hurts when I do X!"
Doctor : "Then don't do X."
It doesn't have to be a 2001-style "torus" station (to start with). A nuclear power plant (or solar panel array) at one end of a tether (rigid, flexible, or whatever) and human volume at the other end ; rotate. Then add modules one at a time. (Two at a time for the first few.) All it needs is power (which the local thermonuclear power plant provides, one photon at a time), reaction mass and building material. The latter probably requires capturing an icy asteroid, or muddy comet, but I personally think that would be a really really good technology to have practice at doing, before we need it in a hurry.
See signature line. The aviation programme of the dinosaurs saved them from extinction, but if they'd had an asteroid-moving space programme, we'd probably all be speaking Brontosaur. And be watching the North Atlantic start to open.
I would suspect that having an extra ton or two of oxygen and hydrogen wouldn't be all that hard to turn into an extra ton of H2O,
This is an exothermic reaction. You want to be careful starting those on Earth, where "run away" is an option. You're even more careful about starting them at sea (I work on offshore oil rigs ; trust me on this, or I'll start to talk about the Hot Work Permit system!), where "run away" has a good chance of being followed by "die of hypothermia or shark attack". You're even more careful in the air (see all the stories bout laptop batteries in particular and lithium ion batteries in general). For space... What did rgb@duke say earlier about "unintended consequences"?
they could designate one tank as the recovery tank.
Having been RTFMing for the Atlas-Centaur system, the Centaur tank is a single stainless steel (OK - NASA speak of "corrosion resistant" steel ; I just bet there's a story behind that. Possibly a blood-stained story. Or maybe a red-fuming-nitric-stained story?) tank body with an internal partition of fibreglass (ugh, sorry Dad! "GFRP") honeycomb which separates the LOX and LH2 sections. Now... there should be some way to guarantee (or control, actively) the pressure differential across that partition. And already you can see the complications of re-filling one tank from multiple others. Please remember that LOX and LH2 have boiling points 70K apart (at atmospheric pressure) and I dread to think how different their specific latent heats of vapourisation are, or their specific heat capacities.
Doable, I'm sure. Simple, I doubt.
explosive decompression while cutting openings into the tanks
That does not seem to be on the agenda, ever. It's a damned sight harder to close a hole than it is to route cables, hoses etc around the problem.
Just haing a think... I'd consider procedures like wrapping the exterior of the tank with multi-wall plastic film tubing (here's a concept I was examining for work a while ago) then filling it with water - e.g piss - and letting it freeze for both micrometeorite protection, thermal and radiation insulation. Then cut the LOX-LH2 baffle from the sides, slide it down to the far end and re-glue. Then start to build up unpressurised partitioning as desired, gluing stuff to the wall.
The design NanoRacks are talking of is to build, effectively, a different Centaur-to-payload adaptor which incorporates a pressure door (to keep the LOX in the tank on Earth), and to have a module with a NASA dock, an ISS dock, a Centaur dock, and then the actual planned Centaur payload mated to that. (Check the Atlas User Guide for information on the 3 existing Centaur-Payload Adaptors) Then the payload module is mated to the ISS as planned and the Centaur tank re-mated to it's mounting point using the ISS's arm.
Clearly, one should avoid buggy, high-end devices that are updatable over the net, and instead, opt for tested, low-end devices that are non-flashable.:D
Agreed.
Kidding aside,
You're kidding? But why? That is such an eminently workable strategy. Definitely let someone else take the pain of debugging the X.0 versions of devices. I want something that will work out of the box. Version X.1, minimum, and preferably X.2
My, what an unforeseeable problem. nobody could possibly have predicted this could happen in 2014.
Unless, of course, they'd had any involvement with chemical plant safety since about 1990, which was the first time I encountered exactly this problem with "oil absorbent" material reacting with a chemical to catalyse an exothermic reaction. And a literature search then (which I did by taking the bus to the university library and persuading a friend who worked there to let me use a terminal and his log in details. Work had fax machines, but no email or any other internet access.) revealed the problem to have been known for decades - including in the nuclear industry.
Something was lost in translation. From pixels on screen (or pressure waves in the air, if you're using a screen reader, or elevations on your Braille display) to ideas in your head. I speak more Russian than is needed to understand this joke and got it immediately.
Slashdot Mirror
Well it is about Windows machines. Nobody with any sense has this problem.
It might engender quantitatively more distrust than in pre-Snowden days, but probably not deeper distrust. The US government has been deeply distrusted by the rest of the world for a long time.
Science users with thousands of rows of data are a negligible market compared to beancounter-wannabes with a dozen (or maybe even up to 5 dozen) rows of data. So, to answer your question, yes it would kill Microsoft to change the default from behaviour that covers up common wannabe-beancounters errors.
Oh, the fuck-wittery of working round Excel v5 bugs like this to deal with combining hundreds of thousands of lines of data throughout the 1990s. And 2000s. And 2010s. And you an guess what I anticipate fucking with in the 2020s.
Then
"Those who cannot remember the past are condemned to repeat it.
Carlos Santana"
(I always struggle to differentiate those two.)
I can't remember the last time I read an astronomy paper (NB : paper, not regurgitated shit in the popular press) which didn't use parsecs and/or AU as the primary description of astronomical distance (with , M-Earth and M-Sol in the mix). For parsecs, the reason is simple : what you measure when establishing distances is parallax, in seconds of arc. Hence PAR-SEC. No?
If converting to metres, then you need to factor in your estimate for the AU, but you only do that conversion when editing the final draft of the paper and the press release You do your working in parsecs. And if the estimate for the length of the AU in metres changes between your observatory time and publication date, then only that derived figure in metres (miles, Egyptian cubits, or whatever) changes NONE of your working or your experimental data changes.
Similar arguments apply to the masses and the AU. You can directly observe e.g. the timing of events in an eclipsing binary (in seconds or days after the start of your epoch of observation), and if you work in units of AU, M-Sol and M-Earth then you get your orbital parameters from those raw observations and Kepler's laws with no conversion factors. You only do the conversions for the proof copy of the paper - possibly not even for the initial copy to go to peer review.
Actually, I remember when the change to a speed-of-light based definition of the second came out, replaing the outmoded definition based on the hyperfine transition of blah-de-blah. It was in the mid-1980s and I was reading the commentary in 'Nature' in the library.
(1) and (2) are probably related, but that's way above my pay grade.
It's also quite a hard substance to get access to without space flight.
No, Mr Patel, a significant number of your potential market/ audience will not become reliant on your product until after map and navigation services are better.
And incidentally, some of us are used to spending time where you don't have electrical power or any mobile phone/ data signal (Iridium excepted, all 9600 bps of it) , and the magnetic field is sufficiently variable that your compass is decidedly dodgy. We carry multiple different location-determining technologies that won't be disabled by simply running out of battery life. Because, that like kills people, you know?
Haven't people learned to not fucking well do that by now? I mean the site has been going for what - nearly 20 years. There are account holders out there who're legally able to buy booze - drugs in some countries - and who were born after the site was set up. And still there are people fucking stupid enough to only read half TFS and none of TFA.
People wonder why many western nations have problems getting appropriate technical staff, and then they behave in such a stupid mannner. And don't see the connection?
As for the recovery procedures - well with a low-6-digit UID, you were probably around when they recovered SOHO from a similar orientation-power problem. Which doesn't make it any easier (space craft are different; locations are different ; latencies are different ; command sets are different), but it is a task that has been done before. And we've seen it (as have the mission managers at NASA).
Scatter-gunning LEO without any planning - in exactly the casual way that NASA does at the moment - with comets launched randomly from the snow line, is likely to end badly for someone. But some of these NASA boffins are using a controversial new theory from some English alchemist called "Newton" (obviously an Apple fanboi), and they claim they can plan orbital transfers in considerable detail. Which is stupid, because that would imply that we'd know if the Sun was going to rise tomorrow, or whether a dirtball 7 light-hours away was going to occult a particular star years, before the event.
(*) all of these are things which will be needed, in abundance, for humankind to have any long term (say 100kyr +) future in space. Given the geological record, that duration would have around a 5% chance of having a km-scale object impacting the Earth.
Is anything at all "rated" for long term habitation in space. You'd never get the physical ailments consequent on a 6-month spaceflight past any industrial safety laws. Seriously, not.
You've gone from step 1 to step 100 without showing any of your intermediate working. This blank assertion does not convince me. Would you fill in a few of the steps by which you arrived at that assertion.
Hmm. "GIGO". Not "garbage in, garbage out," but "getting it in and getting it out". Unless you're *only* talking about sewage. But having had to unblock the family shitter more than a few times after the sister blocked it with nappies (EN_US : diapers), I don't relish that task in zero-g. "Who'd use diapers?" I hear you say. Well, having friend who are saturation divers, and never once having heard someone on a spacewalk tell ground control that they need to go inside for a shit ... I think that every EVA, particularly the 6-, 7-, 10- hour ones has generated a moist nappy, and probably one full of shit.
Tanks are good for getting liquids and gasses in and out ; for pastes and solids, not so good.
Also, for long term storage, you're either going to need a gas venting system (in which case you've got a rocket effect which you've got to control ... more complications) or you're going to need to mix "biocide" with it in appropriate amounts. Then, when you want to re-use it (e.g. to manure your eating plants) you need to neutralise the biocide before it kills your carefully maintained microbiological environment.
What is that "zeroth law of science"? Oh yes, "It's not as simple as that."
Condensed version of the Laws of Thermodynamics : you can't win ; you can't break even ; you can't stop playing ; absolutely everything is subject to the Laws of Thermodynamics, including specifically anyone who objects to the tyranny of the Laws of Thermodynamics.
You're probably thinking of things like hydrazine, or some of the hypergolic mixtures. (A and B are "hypergolic" if mixing A and B results in explosion in milliseconds without needing any initiator, detonator etc. Very good if you want your motor to re-start reliably. The explosion delay is an important characteristic. Milliseconds matter.)
The main fuel in the Centaur stages under discussion are liquid hydrogen ("LH2") and liquid oxygen ("LOX"), but the reliable re-ignition of the engine is controlled by what they refer to as "hypergolic cartridges" - see the engine schematic on page 377 of the Atlas (RT)FM.
Whatever hypergolic mix they use, you don't want to get that shit mixed up with your "intimate lubricant".
Well, for the actual system they're considering, it's the larger (volumetrically) part of a single tank, the LH2 and LOX being separated by a "fibreglass honeycomb", which I guess is glued in place after welding together the bottom end of the tank and the main length of the tank body, but before welding on the top end. I'm not sure whether the LOX is in the upper or lower part of the tank.
Unlike most people here (and I think you and I have discussed this before), I've worked with hydrogen gas too (in analytical instruments), so I appreciate what you're saying about it's flammable limits. What I'm wondering is - with relatively minor modifications to the tank's structure, would it be workable to get rid of the dregs of the fuel by pumping O2(g) into the H2(g) headspace of the tank and lighting a flame of O2 burning in hydrogen. So you approach the UEL of [H2] from the other end, and you have your oxygen going into a mix of H2(g) and H2O(g). Any water that condenses out is uninteresting from an explosion safety point of view. For maintaining the desired pressures in the tank, you'd need an inert pressurising gas - N2 being where I'd start from (might need He for thermal reasons ; meh).
Plan B might be to install a mixing fan into the H2 tank which was covered in Pt-coated wire wool, and to use that to agitate the gaseous contents of the H2 tank, again while bleeding in O2. Monitor tank temperature (Pt-resistance wire as in a kathaometer, perhaps ; kill two stones with one bird?) as the Pt assists the reaction ; if it gets too warm, turn off the O2 supply and let some of the water condense out. Again, make efforts to avoid ever having an atmosphere in the tank that isn't a mix of H2(g) and H2O(g).
I bet the procedures for filling a newly-made tank with it's first charge of LH2 are a real fun read. I don't recall anything about it in "Ignition!" - but that concentrated more on exciting fuels like red-fuming nitric and the "mythical monoprop" and less on dull, pedestrian fuels like LH2/LOX.
I'm tempted to change my signature to : 'monopropellant' is an anagram of 'explosive' for all important meanings of "Kaboom!"
Even in low orbit (i.e., where the drag is sufficient to de-orbit the tank within a couple of years), you're still in what on Earth would be considered a really hard vacuum.
You may be right. But I don't see it as automatically being the case that welding would automatically be stronger, quicker, cheaper or more effective than, say, gluing. We do have some pretty effective glues, for example, and in space, you don't have an oxide or moisture film forming after you abrade the surfaces to join.
A fair enough point. Of course, getting water from the asteroid belt isn't likely to be free either. But if only there were some other reason for learning how to move overgrown dirty snowballs around in space ... like the dinosaurs didn't.
(No, it's not certain that the Chicxulub impactor did for the non-avian dinosaurs - see signature ; I've been following Gerta Keller's work for over a decade - but it sure as hell wasn't a good day for anyone on the planet. Really, knowing - by having done it - how to move multi-kilometre natural objects around in space would be a damned useful skill for a species with a desire to see the distant future. If you're American, you could spend an educational day wandering around in the desert 20-odd miles W of Winslow, Arizona picking lumps of nickel-iron out of the ground and waiting for the 10 megaton energy release. Actually, at 10 megatons, it wouldn't matter much if you walked around in the desert, or sat in a diner in Winslow. Bad hair day, either way.)
See "Doctor" joke upthread. Don't do that.
[Searches toolbox] "Nobody sent us a hammer!" [Radio to mission control] "Can you send up a hammer in the next tool shipment." [Mission control] "No. Next question?"
Seriously, [Myself on an oil rig 3km above the Atlantic mud, off the African coast] : "Your equipment is giving suspicious results. Pass me your multimeter so I can check if it's working properly."
[Service company rep.] "Our office will only send out a multimeter if it is accompanied by a technician. Technician visits requested by the client are billed at $1500/day."
[Self leaves problem on the table. Returns to office. On night shift with junior service company rep on duty, I take out my multimeter, teach him how his equipment works and how to fix the problem. Next morning, senior service company rep is annoyed and his Boss onshore is furious at losing $5000-9000 of technician fees. Client (who hired me) is happy at not paying the fees.]
See my comment upthread about coating the outside with ice bags (sorry - Slashdot-ism : "frosty piss bags"). They won't stop all meteorites, but will certainly stop a lot of them. While also providing both thermal and radiation insulation.
We live at the bottom of an atmosphere approximately equivalent to 10m of (liquid) water, and are evolved to handle that level of radiation. Every mm of water (or equivalent) that we can put outside the space habitat helps towards the goal of radiation dose management.
Grieved though I am when one of my colleagues is killed at work (only a couple dead this year), I've yet to see a case in which any flags went to half mast. Besides, whose flag would you lower? The worker's nationality? Their country of origin? Their cultural identity? Their employer's nationality? The ISS's (or other vessel) "flag of convenience" for insurance purposes (I assume that like every other American vessel I've been on, the ISS is flagged in either Panama or Liberia for tax reasons. And the crew are 30% American, 70% Filipeno? For wage packet reasons.)
But, but, but, that would involve learning how to live in an environment without polluting it. We can't do that - it'd pander to the global warming socialist conspiracy to even consider the possibility of having to pay attention to the environment.
Seriously - seeing all the problems consequent on trying to live in microgravity, one very obvious answer is the old "Doctor! doctor!" joke :
Patient : "Doctor, doctor! It hurts when I do X!"
Doctor : "Then don't do X."
It doesn't have to be a 2001-style "torus" station (to start with). A nuclear power plant (or solar panel array) at one end of a tether (rigid, flexible, or whatever) and human volume at the other end ; rotate. Then add modules one at a time. (Two at a time for the first few.) All it needs is power (which the local thermonuclear power plant provides, one photon at a time), reaction mass and building material. The latter probably requires capturing an icy asteroid, or muddy comet, but I personally think that would be a really really good technology to have practice at doing, before we need it in a hurry. See signature line. The aviation programme of the dinosaurs saved them from extinction, but if they'd had an asteroid-moving space programme, we'd probably all be speaking Brontosaur. And be watching the North Atlantic start to open.
This is an exothermic reaction. You want to be careful starting those on Earth, where "run away" is an option. You're even more careful about starting them at sea (I work on offshore oil rigs ; trust me on this, or I'll start to talk about the Hot Work Permit system!), where "run away" has a good chance of being followed by "die of hypothermia or shark attack". You're even more careful in the air (see all the stories bout laptop batteries in particular and lithium ion batteries in general). For space ... What did rgb@duke say earlier about "unintended consequences"?
Having been RTFMing for the Atlas-Centaur system, the Centaur tank is a single stainless steel (OK - NASA speak of "corrosion resistant" steel ; I just bet there's a story behind that. Possibly a blood-stained story. Or maybe a red-fuming-nitric-stained story?) tank body with an internal partition of fibreglass (ugh, sorry Dad! "GFRP") honeycomb which separates the LOX and LH2 sections. Now ... there should be some way to guarantee (or control, actively) the pressure differential across that partition. And already you can see the complications of re-filling one tank from multiple others. Please remember that LOX and LH2 have boiling points 70K apart (at atmospheric pressure) and I dread to think how different their specific latent heats of vapourisation are, or their specific heat capacities.
Doable, I'm sure. Simple, I doubt.
That does not seem to be on the agenda, ever. It's a damned sight harder to close a hole than it is to route cables, hoses etc around the problem.
Just haing a think ... I'd consider procedures like wrapping the exterior of the tank with multi-wall plastic film tubing (here's a concept I was examining for work a while ago) then filling it with water - e.g piss - and letting it freeze for both micrometeorite protection, thermal and radiation insulation. Then cut the LOX-LH2 baffle from the sides, slide it down to the far end and re-glue. Then start to build up unpressurised partitioning as desired, gluing stuff to the wall.
The design NanoRacks are talking of is to build, effectively, a different Centaur-to-payload adaptor which incorporates a pressure door (to keep the LOX in the tank on Earth), and to have a module with a NASA dock, an ISS dock, a Centaur dock, and then the actual planned Centaur payload mated to that. (Check the Atlas User Guide for information on the 3 existing Centaur-Payload Adaptors) Then the payload module is mated to the ISS as planned and the Centaur tank re-mated to it's mounting point using the ISS's arm.
It certainly looks an interesting idea.
Agreed.
You're kidding? But why? That is such an eminently workable strategy. Definitely let someone else take the pain of debugging the X.0 versions of devices. I want something that will work out of the box. Version X.1, minimum, and preferably X.2
Unless, of course, they'd had any involvement with chemical plant safety since about 1990, which was the first time I encountered exactly this problem with "oil absorbent" material reacting with a chemical to catalyse an exothermic reaction. And a literature search then (which I did by taking the bus to the university library and persuading a friend who worked there to let me use a terminal and his log in details. Work had fax machines, but no email or any other internet access.) revealed the problem to have been known for decades - including in the nuclear industry.
Yawn. no surprise. Makes work for people.
Something was lost in translation. From pixels on screen (or pressure waves in the air, if you're using a screen reader, or elevations on your Braille display) to ideas in your head. I speak more Russian than is needed to understand this joke and got it immediately.
Possibly the funniest comment in the thread (so far).
Subject says it all.