Materials aging in space is a pretty deep subject. That it is the Russian Zvevda module that is leaking/cracking is likely related to the fact that it is also the oldest module in the ISS.
The ISS is/was scheduled to be retired in 2024 (aka 3 years from now) but there are calls to keep it going. My fantasy would be to have SpaceX move it into the Lunar L1 Lagrange point which would keep it in use but it would have to deal with more cosmic rays, also station keeping would be an issue unless we could really get energized tether station keeping to work (lots of solar energy to provide power, but not a lot of mass to provide thrust, so tethers are energized conductors that push against the Earth's magnetic field)
Parking it in L4 or L5 could keep it for future generations but it would be even more of a challenge to go visit.
> That it is the Russian Zvevda module that is leaking/cracking is likely related to the fact that it is also the oldest module in the ISS.
Definitely sounds like it. They can't identify the leak on the inside so it doesn't sound like a micrometeoroid impact and they suspect a second leak that is so small they need a microscope to verify:
> "So far, we have found one place and suspect another, where as some kind of leak exists. We must bring a powerful microscope on a cargo spacecraft and use to examine this place. We are not totally certain so far," Solovyov said.
IANAMS but that screams microfractures. The Zvezda is made largely of an aluminum magnesium alloy [1] that has a fatigue limit so even small repetitive stress can cause it to eventually fail. I'm curious whether this is wear and tear from just being in space and getting irradiated or if its repetitive mechanical stresses like a small tidal force as it orbits the earth.
It completes a cycle of heating and cooling every 90 minutes as it orbits. The temperature differential between sunlit/shaded is quite large, so even though it certainly does not heat to +120C / cool down to -100 C as there is just not enough time, it would still put some stress on it.
I was curious so I checked what temparature the sun exposed parts reached and what the shadow side reaches;
121c to -157c a temparature difference of over 278 degrees. Your remark was almost spot on.
The hull where they're able to manually inspect it shouldn't be going through quite that extreme of a temperature differential because it's wrapped in insulation and protective layers. But it's also almost 21 years old so even the smaller actual cycle is probably getting to it combined with all the other mechanical stresses from equipment and thruster firings.
Those are the cause of the stress cycles. Components don't expand/contact uniformly, resulting in deformation and therefore stress. This process goes through cycles, causing stress cycles which eventually cause the growth of cracks (fatigue).
Have we invented a material that is resistant to these thermal cycles indefinitely, or at least within a range of temperatures of several thousand degrees? I'm never going to have my own Star Destroyer if we continue to use subpar materials.
Carbon-Carbon composite has a cycle life in the millions when cyclically loaded between 0% and 85% of ultimate tensile strength.
Furthermore, that material has a very low thermal expansion coefficient and remains structurally sound at high temperatures.
It does oxidize at high temperature, so you'll have to coat it with something. It's also fairly brittle, basically a strong ceramic (it caused us to loose Columbia during re-entry).
There's plain old "carbon fiber" which is short for carbon fiber reinforced polymer/plastic (CFRP). This is the much more common type, and is a polymer matrix reinforced by carbon fibers. This is very strong and light, but not terribly heat-resistant. In a carbon-carbon composite, on the other hand, the plastic component is also replaced by graphite. This gives a very strong and heat-resistant, though somewhat more brittle, material.
Yes. It's a heterogeneous allotrope made from typically pyrolyzing the matrix, followed by slowly decomposing Acetylene inside the porous structure until the porosity is gone.
Other ways are to just infuse the porous matrix with more resin, before pyrolyzing again. Then loop a (few) dozen times.
As the other posts point out it's not just a matter of material, but a trade off. As you increase the ductile strength you end up with something that is more brittle and the same is true in reverse.
Brittle materials are more temperature sensitive and can rapidly fail. Brittle fracture is no joke look for WWII Liberty ships split in two as an example. We didn't really understand why at that point in time.
The answer though is actually pretty simple and why you can't get a perfect material. The lattice structure of the molecules connected to each other can be soft (plastic) or hard (steel).
In the plastic example just take a milk jug and poor boiling water into it. Don't actually do this without protective gear (oven mit should be fine). The molecules holding everything together get excited from the energy (heat) move around and since they are not closely bonded end up in a different configuration. Your milk jug at this point does not look the same and is deformed.
In the hard example just boil the water you are using for the plastic test. The pot you used does not change because the molecules are tightly bonded.
It turns out the the tighter the molecules are bonded there is still a point where that bond will break. Hence the brittle fracture, which is every molecule mic dropping and going home at the same time.
While I could go down another rabbit hole to the atomic, subatomic, level of how those lattice structures work. I won't as I think this example gives you what you need.
Finally in this case we have a very old, by modern space technology, structure that is made of material that was most likely never expected to last this long. If you want a space ship to last you just have to make sure the engineers understand what "last" means. :)
Climbers and riggers should all be familiar with fatigue limits.
It can be as high as 50% max tensile strength for steel, but I use 30% as my working figure when rigging, and I regularly re-inspect and age-retire gear (at least use annualized color coded markings).
When I’ve rigged circus in the past I’ve taken to replacing aluminum gear I find with steel, especially if it’s going to be installed for a while.
That said, I climb on aluminum. I just age out my equipment. I’d hate for my last thought to be “huh... I guess aluminum really does degrade with repeated stress.”
I had an aluminum bicycle where the front fork failed suddenly. Not instantly but in maybe one or two seconds (just slowly enough to let me not have a terrible fall). My next bike was chrome/steel.
Years ago I totaled a mountain bike in a strange pinched-wheel-in-crack accident that bent the frame in two places but left me uninjured.
When I commented to a bike designer/engineer that it was a strange failure, he said that it was intentional, at least on hardtail mountain bikes like mine. A bent frame is ruined but doesn't lead to a catastrophic loss of control. A detached wheel or twisted fork would be next to impossible to control to a stop.
He looked at my frame and explained that that the two bends were in exactly the place they'd been designed to be, just behind the last butting. It's an impressive bit of forethought.
My guess on road bikes with steel forks, though, is that it's a matter of aerodynamic performance calling for compactness to reduce frontal area, something that would be harder to do in aluminum, and for far less weight savings than the longer tubes on the frame.
There's always titanium... The only big drawback is the cost...
I was told once that the reason for that was stiffness: apparently aluminum forks are stiffer, so unsuspended ones are way less comfortable (in terms of vibrations being transmitted to the frame and handlebars) than steel unsuspended forks.
I would suggest a thin, non-load-bearing, and easy to replace insulation / reflection layer above the pressurized hull. It could reflect much of solar energy back to space, and much of the hull's radiation back to the hull, keeping the difference of temperatures on the hull much lower.
But won’t anybody think of the souls of millions of people, snuffed from existence, and vaporized from the heat of a death laser from your Star Destroyer.
As if millions of voices suddenly cried out in terror and were suddenly silenced.
So bizarre to imagine a space station patched up with duct tape o_O
Assuming the ISS is never going re-enter the Earth's atmosphere, how permanent a solution is tape? Presumably the fracture underneath will get worse with time.
Other than the growth (in terms of length across the surface in question) of a crack/fracture, tape is a pretty valid solution as long as it can hold the pressure. In fact on the “inside” that’s even more strait forward since the pressure pushes the tapes bonding surface interface into the opening, so depending on how malleable the “tape” is, it might not even need “glue” to do the job of sealing a hole sufficiently to hold in the ISS’ internal atmosphere.
Effectively the major issue is “larger”width/diameter cracks/holes create greater pressures that eventually exceed the ability of simple “tape” to suffice for a workable patch. This is all ignoring any NASA engineering manuals and limits, I’m talking entirely theoretical “how long can my duct tape keep me from suffocating” type of engineering, just to be clear.
What needs emphasis in the long term for more permanent structures in space is on the poorly explored topic of welded joint fatigue, with respect to joints that were welded in low earth orbit.
We have welded with several techniques in space before (the Soviets did it) but it basically stopped there and not much has gone into studies of the long term fatigue of the resulting welded joints. If we want permanent space stations we need to be able to “patch them
up” in a way that we can rely on and at least have some idea what the lifespan will be. It’s ok if we have to re-weld pressure hull segments every decade or two but not if the large scale structural welds on a space station hull assembled in space only hold for a few years before they start leaking.
> The pressure difference is one bar, so duct tape is more than enough to hold that.
This is something I have to consciously remind myself of a lot when thinking about space technology. I have this reflex-like feeling that "the vacuum of space" must be a huge obstacle. But then one remembers that 1 atmosphere is the equivalent pressure of a water depth of 10 m. This always blows my mind. In some sense, humans do live naturally pretty close to one end of an absolute scale (pressure). Dealing with near-0 temperature is hard. Dealing with near-0 spatial distance is hard. Dealing with 0 pressure is actually not that hard in the grand scheme of things.
The ISS and all spacecraft that dock with it run at 1 atm. Which is nearly all currently flying spacecraft. (And probably Shenzhou does too, since it's basically a Soyuz.)
Full Disclosure: I have no financial interest in flex-seal.
My general experience with glues is I'll use bolts. I can't get superglue to stick anything together other than my fingers. My rear view mirror fell off again, the third time I glued it on with superglue.
The trick with superglue is to make sure you have a really good contact between two clean surfaces. If you don't have that, superglue will do nothing for you and you're better off with something else. If you do, it's quite strong.
The annoying thing is, glues work best when you use them in the exact situation (material, pressure, etc) they are designed for, but manufacturers are really vague about active ingredients or fillers, so you end up having to buy broad-spectrum glues that are not particularly good at anything.
I've had good luck with super glue when roughing and recleaning the interface surfaces. That said, cyanoacrylate (?) does seem to have sudden fracture failure, e.g. cracking.
When in doubt, I'm a firm believer in two part epoxy [0]. Fiberglass impregnated when necessary. Also stores easier!
And where water is involved (e.g. fiberglass shower tubs), marine epoxy like PC-11 [1]. Can attest it works fine as a multi-year shower patch.
I hate glue for almost everything, but as proof-of-principle check out VHB acrylic adhesive tape[1], or Gorilla double-sided[2]. VHB adhesive is also available on mushroom-head dual-lock fastener, in rolls.[3] (Also no financial interest.)
Side note: there also exist more temperature-tolerant duct tapes.
I used some of this [0] in a last ditch effort to patch a small tear in a Miata canopy (rubber-coated canvas?). Everything else fell off. It's still happily holding, past 3x summers and winters.
Superglue is horrible for rear view mirrors, for a few reasons none of which I remember offhand. There exists special rear-view mirror glue, which is easy to use and is a permanent fix.
I used superglue because the special rearview mirror glue was pretty expensive. And the latter failed anyway, which is why I was looking to glue it back on.
I was also suspicious of the special rearview mirror glue being special. For example, I have a VHS head cleaner tape that comes with magic head cleaner fluid, refills cost $$$$. One sniff told me what it was - alcohol. I use alcohol with it, and it works just great.
I also remember years ago you could buy special vinyl record cleaning fluid for $$$$. It's just vinyl. I use liquid dish detergent, which does a superb job. Doesn't hurt the vinyl one bit, and all the grease, dirt, hair, and who-knows-what-that-is is all gone. (I buy old records at the thrift store because I like the easy listening style from the 60s and 70s.)
I think we need a "Space New Deal", I'm honestly saddened by the lack of progress in space in my lifetime. I mean we've done some great work, but we haven't made any giant leaps since getting to the moon 51.5 years ago.
Thankfully, we do have SpaceX et. al. who really are making some big strides -- but how do we multiply & speed up that effort? ... sorry, I'm being selfish, but I really want to go to Mars.
I think it's pretty much politically impossible. The first big space push was mostly a political pissing match (i.e. not really driven by doing it for its own sake). It's pretty easy to come up with other major challenges that most people will consider more important that also aren't getting funding ... so private industry looks more likely to get some traction. States might get interested if/when those efforts start to get more interesting or threatening.
Mars in your lifetime is implausible, but not impossible I suppose.
> The first big space push was mostly a political pissing match (i.e. not really driven by doing it for its own sake).
My understanding is that the Defense Department was interested in human manned spy satellites liked the planned Manned Orbital Laboratory early on, but that automation progressed to the point where it was preferable.
I think that's one thing people miss when they talk about lack of progress in space. We use space, a lot. The thing is, in terms of things we actually want to do, automated vessels work a lot better than manned ones. People who are focused on manned space missions aren't focused on space, they're advocates for one particular tech stack that's extremely inefficient at doing the things we currently want to do in space.
There's still a lot of defense reasons to go to the moon. You can put much larger telescopes there, though you're back to windows of time you can look at a location but you can have good will and dedicate time to scientists. Though they might not want to reveal the resolution even though this can be roughly back tracked through size. There's also the weapons incentive even though that's illegal. But if you're able to cheaply and consistently put people on the moon then you clearly have the resources to cheaply put large rods of tungsten in orbit (good luck responding to), being able to take out enemy satellites (nav, surveillance, missile launch detection, etc), replace/upgrade satellites quickly, etc. The Apollo missions were always about how much payload you could put in orbit.
It's also beneficial if you want to start space mining, really essential for that actually.
Putting a spy telescope on Moon seems like a bad idea.
- Moon moves across the sky very slowly (relative to stars) which means that your spy satellite would have about 30 days to cover full earth, and would be able to see only a part of Earth at any given moment (theoretically half, but lot of it would be from very bad angles)
- Moon is in an ecliptic? orbit, so spying on anything close to the poles will be from an angle - this might not be bad in all cases but the lack of flexibility is a big thing
- Putting any mass on the Moon requires much more delta V than putting something in orbit. If you can put a big telescope on Moon, you can put several in Earth orbit or put one much bigger one.
Having capability to stage on the Moon would be interesting, especially if fuel can be made on the moon. It would be easier on human bodies and you have access to lot of resources. If you can find water and decent metals, that's a pretty good spot to fuel your rockets.
The moon moves slowly but the Earth rotates quickly. Most of the earth surface can be seen during one day. The earth is not illuminated by sunlight all the time, about half of the lunar month would be completely dark.
Moon is in an inclined orbit, which is slightly elliptic. I assume this is what you meant by "ecliptic" (which refers to the orbital plane of the Earth around the Sun). The orbital inclination has the most significant implications to Earth surface visibility, but the Moon is far enough that almost half of Earth surface is visible at all times.
For Earth observation, satellites are better positioned than a lunar surface observatory.
The moon isn't a great place for an outpost or staging point for exploration. Launches and descents are expensive and spoil all the savings. Maybe if LH2/LOX could be manufactured on the moon very cheaply (from water ice), it could make sense to do refueling for exploration vehicles parked on a halo orbit near Lagrange points.
But orbital refueling of cryogenic propellants (especially hydrogen) or manufacturing them on the moon aren't viable in the near future.
There aren't a lot of good economic or exploration incentives to go to the moon, unfortunately. It only has scientific and prestige value. The long lunar night (14 earth days) makes it a poor location for a permanent outpost.
All of that said, I'm all for going to the moon with humans on board.
You are right about Earth rotating. I spaced out on that one.
About the ecliptic, I was trying to say that any observatory on the moon would have issues observing polar regions because the Earth surface in polar regions would be at a low angle. I know some spy sats "look ahead" to get better detail resolution but they have ability to look from different angles as well. Moon would be a bad spot for that.
Rest of it I mostly agree. One thing up to debate is whether an outpost on the moon would be useful. If you can manufacture fuel on the Moon, it would be very useful. Another aspect is human health in zero G. Moon with low gravity may be enough to help with long term human stay.
The lunar orbit is inclined so that the moon moves between about +/- 28 degrees north/south latitude with reference to the Earth equatorial plane.
That's Earth's axial tilt of ~23 deg + the inclination of the lunar orbit w.r.t. the ecliptic of ~5 deg.
This means that when the moon is at its northest (above southern Florida), it has a pretty good view over the north pole (but it's at quite an oblique angle of ~60 deg), and the south pole is not visible. About 14 days later it's the opposite.
But yeah, I agree with the conclusion that the Moon is not a good place for a Earth observation for a lot of reasons.
>being able to take out enemy satellites (nav, surveillance, missile launch detection, etc)
You can easily do it without having objects in orbit. You can simply launch a ballistic cloud of debris at suborbital speeds and kinetic energy of the targeted satellite will do the rest. Time to hit could be shorter for an orbital system, but not significantly so. This is why I consider the recent news about the Russian orbital satellite killer to be a cheap fearmongering.
There have been studies and the rods from the gods concept doesn’t work. Atmospheric braking would slow them to their terminal velocity before impact. You might as well throw them out of a plane. There are also all kinds of problems with time to target, terminal guidance and cross range capability.
All of what you said can better be done by machines and many such things are done by machines.
The milestones that get people existed are when men reach places hitherto unreached, but there is no practical purpose to risking the life of a man who needs far more complicated facilities to survive, other than bragging rights.
The I.S.S. was largely a political and not a scientific endeavor, and it's a shame it consumed so many resources, that could have gone to more serious scientific efforts.
The cost of the I.S.S. could have easily given mankind nuclear fusion, — the ability to power entire countries with a couple of litres of seawater. It's strange where priorities lie.
There's no proof of this because viable nuclear fusion has not yet been achieved. Humanity may never achieve this for all we know (though I sincerely hope we do).
The same can be said about any research whereto resources are allocated.
Making a reasonable estimate when both started, nuclear fusion seems to be a smarter investment, for if it finally be there, the benefits are incalculable.
We have nuclear fusion, both from the sun and here on Earth (ITER, NIF, H-bombs). The main problems with human-started nuclear fusion are that (so far, iirc) it consumes more energy than it produces, and we cannot sustain it for a long time.
"The benefits" are currently very calculable, and direct economics of nuclear fusion is very negative. (The research benefit is unique though.)
For nuclear fusion to be of incalculable benefit to mankind, we need insanely small nuclear fusion that is energy-positive and sustainable in a simple way. "Insanely small" means smaller than Moon-sized, when we know that Jupiter-sized is too small/light in nature.
Sustained nuclear fusion for energy generation still faces daunting challenges.
10 years ago the consensus--scientists, engineers, etc--was that self-driving cars would be ubiquitous or on the cusp of ubiquity today. That same common but woefully mistaken wisdom is also behind the preference for remote space exploration and exploitation.
We clearly have issues with underestimating the complexity of these engineering problems and overestimating the pace of technological progress. I'd also argue, albeit more contentiously, that we systematically underestimate the utility of a physical human presence at exploration sites, and the cognitive dissonance of our biases cause us to scale back our ambitions so we don't have to admit to the limitations of the remote-controlled approach.
Exclusively committing to remote-controlled exploration also avoids the thorny issues around deliberately putting explorers into harms way or even actual harm. I think Musk understands, knowingly or at least intuitively, that the debate is basically impossible to have; our culture isn't equipped for it. Necessity will drive us toward human space exploration. Safety will be to some extent needlessly neglected, and then there'll be vigorous finger pointing and "I told you so"s after the fact--after the sacrifices have been made and after the benefits have been secured for all. Basically the same pattern will play out as with any other area where prohibition or abstention is the official choice despite its patent unviability.
Engineering difficulty is often put forward as a limiting factor. But actually I think history suggests that with enough resources we can accomplish things. And in fact it is possible for a project to have astonishingly brilliant engineering and still be disappointing in terms of wider impact (see the space shuttle).
The limiting factor is much more mundane. Getting humans to collaborate selflessly on complex projects is difficult. Effective communication in large groups is a massive unsolved problem. That is what holds us back, not engineering complexity. Perhaps the true genius of SpaceX is using Mars to bring people together. Something the bean counters at Boeing never thought of!
> 10 years ago the consensus--scientists, engineers, etc-
This is only true if you were sampling the people trying to build them (which is mostly what the popular press did). Really there wasn't anything like consensus, but there was a lot of optimism.
Really hope China ditches the Outer Space Treaty and claims sovereign territory on the moon. Only then will the space race ignite again. It seems only competition makes the human spirit move.
I suspect any player powerful enough to have the means to claim territory on the moon, will ditch the outer space treaty eventually.
Unless it is a purely scientific mission, but that is un likely at the moment.
> I'm honestly saddened by the lack of progress in space in my lifetime
I just told my youngest kid this the other day:
When I was his age (~25 yrs ago), my dad told me with a bit of a sad look on his face, "I hope we return to the moon within your lifetime." At the time, I kind of laughed because, hey, we're sending people to the moon CONSTANTLY. It took me a minute to realize that I was sorely mistaken and that we haven't sent a human to the moon at ALL in my lifetime. I was taken aback.
All this history about Neil Armstrong and the Apollo missions and the space shuttles -- we even got to see from Cocoa Beach a shuttle launch on a family vacation. So much of it even from MY DAD's youth, him telling us about when he got to hear the famous "One small step for [a] man" live from his Scout Jamboree trip. All of that, and we haven't actually been to the moon in decades? It totally blew my mind.
I think before that moment, I must have assumed that it was Real Soon Now before we'd have a permanent base with people living and even being born. And to learn that we sort of gave up...
It's not unlike when I was six and remembered reading about fully autonomous cars that were coming Real Soon Now, too. Thirty+ years later and that reality actually seems farther away than I had imagined despite the actual progress we've made.
I've been watching a lot of documentaries about Mars and the more I learn the more it seems so incredibly daunting and overwhelming. The atmosphere isn't even thick enough to slow down properly from the massive speed you need to get there at a time scale that works. How do you land large colonization facilities, landers, etc. in an atmosphere that is 1% as dense as Earth's? How do you then have enough fuel to leave? I know there are workarounds for everything but there are some hard physics walls here.
>The highest atmospheric density on Mars is equal to the density found 35 km above the Earth's surface.
How do you land large colonization facilities, landers, etc. in an atmosphere that is 1% as dense as Earth's?
With supersonic retro propulsion on a rocket that can be reused.
How do you then have enough fuel to leave?
You don’t, so you need to make the fuel with robots landed on one-way missions first. Luckily there are plenty of raw materials on Mars (in the atmosphere, soil and water deposits).
It’s very hard but it’s certainly doable if you can do the first part.
I feel like we sort of did get a "Space New Deal" in the form of "Let's just send robots everywhere." Not great from a human space flight perspective, but political will is what it is.
Look at the SLS, how much money was spent, and how unlikely it is to ever do anything, and it looks like we aren't even capable of a Space New Deal if we wanted to.
Going to space is only a secondary goal for SLS though. Keeping a bunch of people in politically influential states and congressional districts employed is the primary goal and it's succeeding at that.
Not quite. Under certain conditions (high marginal propensity to consume, etc.) the "multiplier" can be > 1, and then your stimulus really creates value.
Well, in the literal sense, the government can raise revenue via tax and employ people. So it's literally true... You might not like it, or it might be ill advised, or might believe that all taxation is theft, but it is what it is.
Money represents work, and the government is waisting billions of dollars of highly trained professional work hours on the SLS. This money could have been used in unaccountably more productive enterprises, but the incentive structures and feedback loops are so broken in government, it can't even build a rocket ship, in an era where every two bit backyard company is building their own.
The taxes raised to pay for SLS actually are screwing over the rocket industry because companies actually getting things accomplished have to compete for the highly trained engineers and scientists being wasted on SLS. There's no amount of "trickle down theory" that makes the SLS a net gain for society.
> This money could have been used in unaccountably (sic) more productive enterprises
The space industry is one of the major resource sinks that prevent runaway economic growth that would destroy civilization as we know it: the so-called "economic supernova".
The natural result of scientific progress is a kind of economic singularity beyond which is entirely unknown territory. What happens to our civilization when the primary underpinnings are obviated by technology? No one knows.
So, NASA, FAANG, the Financial Industry, most of the lawyers, accountants, and bureaucrats, etc. are just make-work jobs to occupy productive people to keep them from inadvertently causing the apocalypse.
(FWIW Bucky Fuller calculated that the inflection point to runaway wealth was in the mid-1970's. We're fifty years over due for the end of history.)
While I am horrified by the sums of money, I think there's a slightly less cynical take than the congressional districts one.
If you want to have an industry of people who make X, then there need to be people employed making X, every year, for decades. And at more than one company, so that it isn't too fragile a career path. When X is single-use rockets there is the advantage that after one flight you have to re-build, whereas when X is tanks (or other long-lasting hardware) you have to choose to throw the old ones away.
I don't share your gloomy view. The annual rate of orbital space launches has been steadily climbing since 2000 and is now double what it was then. It's still slightly below the peak of the 1960s-70s but I'm pretty optimistic based on the clear trend.
Men on the moon was just a gimmick. I'm pretty excited by all the stuff we keep sending to Mars. There's another rover landing there in just a few weeks' time.
It's not just NASA and SpaceX. We've recently seen Israel go to the Moon, Europe and India go to Mars, Japan return samples from an asteroid, and China return samples from the Moon. Who knows what one of them will do next. The only value I see in having people on the Moon or Mars is in working towards a permanent colony that could eventually become self-sufficient. Anything less and what's the point? We have robots to do almost all the stuff humans used to be needed for.
Seems we have dialed back manned missions, but the rovers on Mars, the satellites orbiting Jupiter (Juno) and Cassini, reaching Pluto (New Horizons), and asteroids (Hayabusa) and soon to be James Webb Telescope are all very exciting and represent significant progress.
There has to be some revenue stream beyond just satellite launches and government research. Right now there's only so many reasons to go to space and a lot of those are pretty small markets or able to be served by one or very few provider(s) pretty well.
Sorry, what? The reason we have so many launch providers today is because space is extremely valuable. Even though you don't realize it there are hundreds of satellites above you head and you're connected to many of them. Telecommunicate (not just your phone), GPS, weather, etc. We wouldn't have the modern world without access to space. Things getting cheaper is causing a boom.
I'm largely talking about setting up a space industry that includes human spaceflight independent of government spending which is what you need for it to really take off because unless it's specifically designed to be impossible to kill like the SLS other missions get killed and messed with as each new admin or congress decides it's an easy place to make a mark.
There's a lot up there but it's still not that big and there's limited space for new arrivals. SpaceX largely exists because of the government contracts to launch to the ISS and for various NRO launches there's not enough public need for launches alone to sustain a rocket industry is what I mean. Especially for human launches, the only reason to have a human rated orbital capsule is to service the ISS.
low attenuation means fewer repeaters needed on oceanic cables, reducing the cost of operating the fiber optic cable.
"Using estimates for the theoretical loss limit of ZBLAN glass, a 2,000-km length of ZBLAN fiber could have the same optical loss as 10 km of silica fiber, which would be an extraordinary performance gain."
"Fluoride fibers inherently provide naturally a much wider bandwidth than silica with up to 100x usable number of data channels, <2 petabytes per second of data with no amplification for 1,000km or more and no need to carry power for said amplification lines. By comparison, current undersea cables use one repeater for amplification every 100-150km, at a cost of ~$1M each."
I can only guess that it would be much harder to accomplish than one would imagine. Definitely want a padded room so you dont bang your head, or other parts slamming into sharp objects.
Putting aside space-sex, I really like the idea of an inflatable module that can quickly (and presumably fairly cheaply) increase the space on a station.
It is simply too expensive for government to do it. It'll have to be private enterprise. (Not that private enterprise could pay what NASA spends either, but that it would be 10x cheaper for private enterprise to do it.)
You think NASA, ESA, Roscosmos, etc can build the ISS but they can't raise it to a higher orbit? Honestly, this cheering for privatization of space research is getting out of hand.
It's not too expensive for governments to do it, and it doesn't have to be private enterprise. Neither of those things are true. Nor is it even clear that it would be cheaper to contract with some private provider to boost the ISS than for the space agencies to figure it out themselves with the launch vehicles they have. How do you think NASA, ESA, etc build rockets anyway? They contract with Lockheed, Boeing, Airbus, Northrop, and others to build them. Having the whole operation be under the auspices of SpaceX doesn't do much other than make other governments more reluctant to help fund it.
Government contracting is not at all indicative of how the free market works.
Also, the free market would never have built a design like the space shuttle. Pushing very heavy wings and landing gear into space doesn't make sense and never did.
To be fair, the magnitude of that risk was not realized in the design phase. Though one could hardly miss the giant, heavy wings & landing gear and the heavy structure to support it. That was obvious to me at the time, and I often wondered why no article about the shuttle ever mentioned it.
Musk figured out a far better way to make a reusable rocket. All it needs is a bit of extra fuel that is burned at the last second.
(Playing the Lunar Lander game in college, I soon realized that the minimum fuel burn to land it was to fall ballistically and go to full power as late as possible, hitting 0 fps just as one touched down.)
Yes, a crewed fuel tank was one of the designs considered, as was three shuttles (2 crewed tanks + 1 ship) in a triangle. Visit the Udvar-Hazy Air & Space Museum Annex in Virginia if you ever get a chance, there’s an exhibit on all the proposed designs. We got the worst possible one.
In 2021, the cheapest and most reliable way to send a man to space is to use a Soyuz, for a cost of 19-22 million dollars per person. This is of course a communist design launched by a public space agency built by a majority public ownership factory.
I think it might be time to accept that in these cases its pretty often not the inherent efficiency of the free market - which can often be less efficient than alternatives - but the ineptitude of the US government and it's agencies as far as doing things efficiently.
There are US politicians and functionaries that admitted publicly that they made the government less efficient for ideological reasons to make the free market look better.
That doesn't mean it was profitable. The price could have been set for political reasons. Or it could have been set by the marginal cost of the launch, ignoring entirely the development cost that was written off when the USSR collapsed. Or it could have been enough to simply pay for the weight of the astronaut in a rocket that was going up anyway, like a hotel will sell rooms at a deep discount just to not lose as much money if it cannot otherwise. If communism produces goods and services cheaper than the free market, we'd be awash in Soviet goods.
The US government produces goods and services at "cheap" prices, but the losses are made up for by the taxpayer.
> which can often be less efficient than alternatives
You mean my whole youth lived around Soviet-made goods is an 'anecdotal evidence'?
Well, perhaps I should have tried living in those fantasy Soviet Unions some people on the internet love so much. Those must have been magnificent states!
Well, it does remain anecdotal evidence. The point of the above commenter is that while they could be made the lack of creativity in planned economies lead to them not being made, not that there were made.
You talk about planned economy shows that you learned about it from third-party sources. There was an abundance of creativity, it just wasn't aimed at creating consumer goods, because they just could not be made in the planned economy at all.
Yes what you present is anecdotal evidence. Also nobody is saying they like the Soviet Union that is an idiotic strawman. My point is that they could be made but the USSR wasn’t gearing its economy towards consumer goods because it was a military state who cared almost entirely about heavy industry to benefit its military industrial complex and competition with the US.
While that is true, the USSR produced a better military and more, higher quality consumer goods than most nations of it's size.
That said, it is certain that the soviet system was suboptimal in a great many ways.
But, crucially to the fact at hands, 1960s' USSR produced better rockets to send people to the ISS, at a lower cost, than 2021's USA, so there something beyond the free market in this particular case.
I'm sorry, what else are you suggesting? That we let the free market figure out by itself how to maintain the ISS without signing any government contract?
Also, Falcon 9 wasn't the product of a government contract.
I’m not arguing the US isn’t a better system. I’m saying had the USSR decided to allocate its resources towards consumer goods, it’s ridiculous to think they couldn’t have had a large industry.
It's ridiculous to think that that could produce anything good for consumers. The system just didn't work towards that goal. You can't design a fashionable piece of clothing if you have a 5 year plan imposed on you.
It's also the framework I think of when I use my own phrase 'New New Deal', as in a jobs program that focuses on building fresh public infrastructure (not-broken window jobs).
I've been watching a lot of documentaries about Mars and the more I learn the more it seems so incredibly daunting and overwhelming. The atmosphere isn't even thick enough to slow down properly from the massive speed you need to get there at a time scale that works.
>The highest atmospheric density on Mars is equal to the density found 35 km above the Earth's surface.
Since there's virtually no drag between the planets, the distance doesn't linearly determine the amount of fuel. What matters is velocity changes. It's about 10km/s to get into orbit, and 5km/s or so to transit to Mars. Coming back is a lot easier because Mars has less gravity and atmosphere, and you don't need to bring as much stuff back. So maybe let's call it 20km/s total? Fuel has mass, so it takes fuel to bring fuel. If you were to bring all the fuel you needed along, it's probably going to end up being 5-10x the fuel for getting just to low earth orbit. Either you build one giant rocket, or more realistically you launch a few smaller rockets. Alternatively, if you can manufacture fuel on Mars, you only need to take along 15km/s worth of fuel. A single falcon heavy launch could probably handle that.
Said another way, such a mission could probably be completed with one or two falcon heavy launches. That's basically equivalent to 3-6 falcon 9's worth of fuel, and a falcon 9's fuel cost is something like $200k. So, $600k-$1200k in fuel.
A spaceship system actually suitable for going to Mars would probably use cheaper fuel than falcon heavy. By the time it's actually built, though, inflation and politics will have made the fuel expensive again. So my best guess is a cool $1million!
Space Force is specifically for military and not public. To protect strategic assets like keystone satellites, launch detection system, etc. Stuff the Air Force was doing but the sub department in the AF grew big enough that it became it's own thing. Similarly it's not unlikely to see a cyber force happen in the future.
Well, if you want something done, the best way is to do it yourself. How much labour/$$$ are you willing to put per month for the space exploration efforts?
Station keeping. The L4 and L5 points are nominally self stable, if you put something there it won't wander off. (this isn't true of the L1 point which is more dynamic). To do station keeping you need reaction mass and working thrusters. That level of infrastructure requires some maintenance, whereas you could put an empty/abandoned ISS in the L4 or L5 point and it would just sit there for no additional cost.
Right, but why do you need to do station keeping at all. Tracking objects is cheap, and a normal graveyard orbit isn't going to be perturbed so much that it would be notably harder to reach again in any reasonable timeframe.
Skylab was in LEO. There is hardly any decay once you get higher up, you're quickly approach "many lifetimes". That's why the new huge LEO constellations won't be a big space garbage problem.
That's shooting an ant with a rocket launcher. You could avoid space junk in much lower orbits than the Lagrange points.
I encourage everyone to get a sense for the sheer scale of this. Do it on your floor or walls. Try a scale of 1cm = 5000km or 1cm = 10,000km. Cut out little Earths and moons and map out geosynch, the lagrange points, etc.
At some point, if you go too high you end up in the Van Allen belts, which if I understand correctly are a really harsh place for spacecraft to be. Generally those orbits are used for parking bulky rubbish that's too much trouble to de-orbit.
Geosynchronous orbits are above the worst parts of the radiation belts, so maybe that's a good place for the ISS. Or even higher; it doesn't need to be geosynchronous. The main advantage of a low orbit is that it's easier to get to from Earth, but if you're just parking it long-term as a museum piece that doesn't matter as much.
I wouldn't expect Lagrange points to have much of a problem with clutter unless we decide to start parking enormous quantities of stuff there. Objects can spread out and orbit the points; as long as they're all going in about the same direction they should be able to avoid running into each other.
You don't need a stable orbit, just one that will keep it in our neighborhood and away from the atmosphere and congested orbits.
Put it in a high orbit, and point a telescope at it every now and then to update our record of it's orbit. By the time we are ready to visit it, even if its orbit changed, its new orbit would not be any more inconvenient then where we left it.
The moon's lumpy gravity field actually causes the eccentricity of most orbits to raise quite fast, eventually bringing the periapsis below the surface (or the apoapsis on an escape trajectory, but I recall the former being more of an issue): https://www.youtube.com/watch?v=EadClM4Y45A
For future spacecraft, would it be possible to have a double hull with a self-healing jell in the middle? (In concept, I'm thinking similar to tire sealer, something with clotting agents in it).
That'd stop the leaks but not mitigate the risk of catastrophic hull failure caused by untreated cracks originating from repeated thermal cycling stresses
I realize their orbit is relatively clear of debris and micro meteors, but is this materials decomposing or degrading and not random damage and happenstance?
The ISS has no doubt been important and I remember how excited I was when it was being assembled. Is it really so historically significant it's worth the amount of effort you're describing?
Hull is definitely not decomposing or degrading. If left in peace at sufficiently high altitude it would look the same in a million years.
My bet is the issue is most likely stresses due to vibrations under pressure and pressure changes. It is complex but also well known problem. As the astro/kosmonauts move about the station, resupply dock, pressure changes, etc. some parts are being subject to constantly changing stresses while already being stressed due to pressure.
It might also be possible that there are some additional thermal stresses but I think it is less likely these are source of the problem.
These discussions about materials are often difficult, because there are meaningfully different processes that are lumped together in everyday language.
Mechanical stresses leading to failure at a particular point are certainly a form of degradation, but I believe they mean degradation in the sense where the entire body of the material is undergoing some change (like a plastic bottle fogging or such).
I think seeking clear descriptions is fine, treating it as a "gotcha" game is tedious and unnecessary.
I took liberty to look through the literature and it seems change of physical and chemical properties of material due to all types conditions (including physical stresses) is covered by the term.
I am not into mechanical science that much, I have always treated degradation as a kind of surface or volume phenomena where the material looses its properties due to temperature, radiation, age, chemical reaction, etc. For mechanical effects there are already very good terms like metal fatigue and stress induced cracking.
I agree but you can say the same thing in reverse. This is a public forums, you don't need to claim something isn't right because it doesn't fit the technical description.
Cracks are a common sign of metal fatigue, which can be caused by repeated stress cycles. Imagine bending a piece of plastic back and forth until it snaps.
I don't recall which of the many print books I read in my gearhead/TIG-welding days had used the term, but the lack of a distinct fatigue/endurance limit [0] for these metals was put into practical terms with something along the lines of "like slightly bending a cold stick of butter".
It's why aluminum airplanes are supposed to get inspected for cracks regularly, and why aluminum bicycle frames must be so uncomfortably rigid. If there's cyclic stress occurring, it's a question of when, not if they will crack.
If I had to guess it's from Carroll Smith's 80s-era Engineer to Win, it sounds like something he'd write.
I think it refers to the type of break the joint makes?
However, while searching I found this search excerpt:
Which metals diffuse into other metals and how? | Naked ...
www.thenakedscientists.com › forum
Sodium and potassium metal (both *soft solids, like cold butter*) react
So perhaps it is used to designate 'soft solids' versus 'hard solids'
> Is it really so historically significant it's worth the amount of effort you're describing?
Space launches are getting a lot cheaper, so moving the ISS to another orbit might not be such a big deal as it used to be. We don't really need to keep the ISS around forever, but on the other hand, losing it would in some ways be similar to the burning of Notre Dame in 2019 (I can't believe that was less than two years ago). It's mankind's first permanent foothold in space. In that sense, it's irreplaceable.
Let's say moving the ISS at the end of its usable lifespan costs a half billion dollars. That's like asking every U.S. taxpayer to pay about two dollars. Is it worth it? To me I think it's worth a lot more than two dollars, even if it unlikely that i'll ever actually be able to visit the ISS in my lifetime.
Are tidal forces a significant source of strain on the ISS, due to the size of the station putting different parts of it in slightly different orbits? And if so, would these forces be less at a lagrange point?
Make it robotic only. Stop/dump all life support, but leave manipulators/robots like Canadarm, and accept robotic add-ons and commercial sub-satellites.
Scotchweld 2216 is often the glue of choice in space aplications, or if higher temperatures are needed there are other more specialist glues out there.
But Scotchweld is as easy to use as JB Weld and also very cheap.
Source: Am an spacecraft AIT engineer responsible for much gluing
I'm betting on something closer to "slime" the stuff they put in tubeless mountain bikes. Or at least I don't know why the thing isn't built with an inner self sealant. If nothing else if its made with a bit of florescent die locating leaks becomes as simple as looking for the glowing spot on the outside.
You're joking but this reminds me of a hard sci-fi novel I read recently, Saturn Run[0]. One of the minor worldbuilding trivia there is that adhesives seem to be way overused to fix and modify things in space.
(The book also features the coolest design for a radiator I've ever seen anywhere.)
> He underscored that air loss due to the crack are insignificant. "This leak is like as if you’d drill the hull with a 0.2 mm diameter drill. I’m not sure such drills even exist in household.
I had to check my collection of PCB drill bits when I was reading it, and yes, I confirm that I'm a proud owner of a 0.2 mm drill at home, it was the smallest one in the box ;-)
The existence of a drill is no guarantee that you can actually create a hole. I once was a battle tank maintenance guy and we had to replace a cover placed in front of the armor. The replacement had holes in different positions, no problem, just drill a new hole, right? An hour and a few broken drills later we gave up. No doubt there are drills that work on that armor-steel, my point is, depending on the material just any drill may not be good enough. An hour of hard work barely caused a <0.5mm "deep" scratch to appear!
PS: We solved the problem by not solving it. Attaching three points instead of four was enough, de decided. That tank would never see a real battle but was only used for training anyway.
True. But if it's a PCB drill as (s)he said, then it's likely either solid carbide or has a carbide tip. Hold everything rigidly enough and run that drill at the right speed and feed rate, and there's a good chance that it will drill armor plate.
They leak 0.3 mmHg per day and are currently at 750 mmHg. An emergency is 0.5-1 mmHg per minute. They really don't have anything urgent to worry about.
As a person that's previously owned a Zodiac-type boat, I really wonder what an ISS patch kit looks like.
What sort of adhesives, covering materials, chemicals and application stuff do they have on hand for quick "we need to stop air escaping through this hole NOW" type situations?
Obviously the problem is sort of reversed, if you have a leaky zodiac you're patching it from the outside and trying to stop air escaping into the atmosphere. If you have a leaky ISS module you're inside it, and applying some sort of quick-setting malleable chemical goop into a hole that's sucking your air outwards...
You'd have to take the derivative with respect to time, I'd think, because the ejection rate might decrease with pressure.
Instantaneously, with a 1mmHg/min leak I think you'd lose roughly 1.5kg or a little
over a cubic meter's
worth in the first minute, given the 915.6 m^3 pressurized volume and a mass of ~1.3kg/m^3 for air at sea level (760mmHg, which is close enough). How long it takes to get down to an unsurvivable ~250mmHg (assuming an Earth-air-like breathing gas aboard ISS, which seems reasonable) takes more trouble to figure out than I care to go to on a Friday night, but the lowest possible bound (assuming a constant ejection rate) would be somewhere around 500 minutes, or between eight and a bit to nine-ish hours.
Honestly I'm more curious what area a breach would have to have to produce that kind of leak rate.
edit: Actually, given the effectively infinite volume at effective vacuum outside the hull, you wouldn't see the same "counterpressure" effect you would in atmosphere, that causes pressure equalization to slow
down as it approaches equality - there's no equalization that can happen here. That said, you'd still lose less mass per unit time over time, as the internal pressure and thus the mass per unit volume drops.
The ISS is/was scheduled to be retired in 2024 (aka 3 years from now) but there are calls to keep it going. My fantasy would be to have SpaceX move it into the Lunar L1 Lagrange point which would keep it in use but it would have to deal with more cosmic rays, also station keeping would be an issue unless we could really get energized tether station keeping to work (lots of solar energy to provide power, but not a lot of mass to provide thrust, so tethers are energized conductors that push against the Earth's magnetic field)
Parking it in L4 or L5 could keep it for future generations but it would be even more of a challenge to go visit.