And as for science, knowing whether Venus is the fate of Earth, or how to determine whether an exoplanet would be a second Earth or a second Venus, is a lot bigger of a question than anything Mars can answer. Venus is not only our closest neighbor and almost the same size, but once had oceans like Earth. And her atmosphere appears locked into this vicious cycle, where she's hot because her CO2 isn't stored as carbonates, but she can't form carbonates because she's too hot. And even if you want to dismiss that as an indirect side effect of water loss due to devolatilization due to a lack of a magnetic field (and ignoring the question of "why" the latter is), that's not the only thing Venus is cautionary about. 500 million years ago it appears that the entire planet, or nearly so, was resurfaced by volcanism. Can such a thing happen here? We can't say so because we have no clue why it happened.
Venus once was another Earth. We want to know what went wrong. It's hard to model the Earth when Venus doesn't work with our models.
Ah, yes - the 20th century was filled with no shortage of disappointments concerning our planetary neighbors.
The unfortunate thing about Venus is, if its atmosphere had stopped at around the height that is today 54-55km, nobody would be talking about Mars as a human habitation destination. Indeed, one proposal for terraforming Venus is to build a whole new surface at that height and just call it good enough;)
My problem with the name Uranus isn't that stupid, overused joke - it's the fact that it's the only planet named after a Greek, not Roman, god. It should have been Caelus.
I remember as a kid watching reruns of Green Acres on Nick at Night. They had an ad - which my father had to explain to me - which showed the lead actress, with the voiceover: "This is Eva Gabor. Not Zsa Zsa. Eva won't hurt you."
Your standard Venera-style probe consists of the following layers:
1) Outer spherical steel shell 2) Insulation 3) Phase-change material as a constant-temperature heat heat sink 4) Everything that you don't want hot, compressed, or exposed to corrosive chemicals.
The only thing that's hard to keep from happening is the "hot" part, because eventually your phase change material reaches its limits and the temperature starts to rise.
Don't misunderstand, I think the goal is noble. I'd love to have some atmospheric data coming from Venus, information on surface, weather, etc.
I assume you mean "more data". We've already had the Venera probes, the Pioneer probes, and the Vega probes (including PTFE superpressure balloons - the only airborne vehicles on another world to date).
I just wish we used units that rendered the gas constant unnecessary. I should probably memorize it to more digits than "8,31" so that I don't have to keep looking it up :
Your post is largely correct, with the caveat that with proper insulation, the rate of heat flow to the exterior can be kept surprisingly small. But RTGs are indeed hindered by the external heat that they have to reject waste heat to. Solar power surprisingly actually works on the surface, but at terrible efficiency (if I recall correctly, something like 2.7W/m). And wind indeed has been proposed as a power source. Windspeeds are low, rarely more than a meter per second or so, but due to the high density it's not actually a bad power source. There's even been one wind-propelled rover proposal under investigation (Zephyr).
Indeed, the whole point of long-term Venus landers is indeed not large amounts of power, but basically surface "weather stations" or "seismic stations" that just sit there using a few watts here and there and transmitting results up to a higher power relay.
On the other hand, getting things to the surface of Venus is surprisingly easy. Landis once worked out that you could launch a hollow titanium sphere to Venus, have it aerocapture, and land safety on the surface, without any sort of aeroshell, ablation system or parachute whatsoever. Venus has a big "fluffy" atmosphere for slowing things down, and by the bottom the density is so great that terminal velocity can be survivable for well-built probes.
Except 1) A failure takes out an (expensive) launch pad for half a year, and 2) the FAA won't let you just take a "damn the torpedoes" approach, because these "torpedoes" contain the energy of a small nuclear bomb.
The industry average failure rate is commonly stated at 95%, although that number is biased down by older rockets who which were developed at a time where a higher failure rate was considered more acceptable (it's lower with modern rockets). SpaceX was at 93% after their last accident. I repeat what I wrote: "Not terrible, but not great."
As for mounting satellite before static testing:
According to Peter B. de Selding on Twitter, SpaceX implemented an optional policy of attaching the payload to the vehicle earlier this year with some “insurer upset”, as it saves about a day during of launch preparations, and allows SpaceX to monitor the payload’s interaction with the vehicle. The customer can decline this option if they wish.
The idea was SpaceX's. Operators can opt-out, but as a general rule customers go with whatever the launch provider thinks is best. And to be fair, there is some risk from opting out as well. If something is messed up with how the payload is mounted it might become clear during the static test.
Lastly, I would not call SpaceX's most recent failures "right up front". And while I was willing to give them a pass for their first failure (the short of it: a supplier who lied about their QA process), this last failure falls entirely on their risky decision to store COPVs with no external liner submerged in densified LOX. I certainly wouldn't have taken such a risk. And the design isn't changing. Great that they're trying to reduce buckling and changing their helium loading procedure and all of that, but at the end of the day, composites have poor LOX compatibility, and densification just makes it worse.
That sounds rather disingenuous if we're talking about two or three problems
What's disingenuous is selecting for comparison launchers that had early problems but leaving out those that didn't.
By rocketry standards, SpaceX's record isn't terrible, but it's not great either.
This is true, nevertheless, the Soviets managed to reach something like sixty launches of an R-7 in a year sometime in the 1970s
Because the Soviets didn't have the FAA grounding them until they can prove to a very high degree of confidence that they'd identified and remedied the problem. The Soviets had precisely the opposite attitude. For almost every single Venus mission, for example, they launched in pairs, just in case there was a fault in one launch vehicle / transfer stage or probe en route (and sometimes they'd lose both!)
It's fine just as it is for a lot of non-legally-questionable uses, such as image compression (smaller number of real pixels to achieve the same aesthetic effect), upscaling old images (picture a high quality upscaler in an emulator for old games, for example), etc.
By the way, this appears to be basically the same thing that Magic Pony Technology already did. Another thing that MPT demonstrated with their software was infinite texture generation - given a fixed size texture, it can create an infinite amount more that "looks like it". Also, a neat thing was its use on images that contained text. If the neural net recognizes a letter, then it can obviously draw the letter in full, clear detail. I've had quite a few PDFs that were exported at too low of a resolution for their images that I would have liked that on; it's no fun having to zoom in and tease out the letters one-by-one manually.
That's the thing, there really is. With launch prices down, satellite tech advancing fast, and a rapidly growing middle class, there's a large demand for commercial launches right now, and it only looks to grow.
My problem with SpaceX's plan isn't the market - that's solid. My concern is that the faster you want to launch, the less you can tolerate failures. The time a failure leaves you unable to launch for is independent of how fast you're launching. The faster you launch, the sooner the time between failures. So an increasingly large percent of your time becomes time down due to failures. The only way to overcome this is to correspondingly boost reliability. Want to 10x launch rates? Better 10x reliability. It's a tall order. SpaceX is already on the low end on reliability (not terrible by rocketry standards, but not great), so they already have a deficit to overcome.
He honestly doesn't seem to realize that. The more of his tweets you read, the more it becomes clear. He honestly thinks he is being / will be listened to and will be a "moderating influence" on Trump.
All of his tweets on the topic, not counting replies:
"The blanket entry ban on citizens from certain primarily Muslim countries is not the best way to address the country’s challenges" "Many people negatively affected by this policy are strong supporters of the US. They've done right,not wrong & don't deserve to be rejected." "Please read immigration order. Lmk specific amendments. Will seek advisory council consensus & present to President." (links to executive order) "Reading the source material is better than reading other people's opinions about the source material" (links to a person saying "Not a trump lover by any means, but after reading the language of the order, it looks far less bad than portrayed by the left") "Regarding the meeting at the White House:" (links to image of text insisting that he's hoping to use his status on the advisory council to oppose the order, and that all he cares about is building a good future for humanity) "At my request, the agenda for yesterday's White House meeting went from not mentioning the travel ban to having it be first and foremost" "In addition, I again raised climate. I believe this is doing good, so will remain on council & keep at it. Doing otherwise would be wrong." "Many in America don't realize how proud they should be of the legal system. Not perfect, but nowhere is the cause of justice better served." "Activists should be pushing for more moderates to advise President, not fewer. How could having only extremists advise him possibly be good?" Retweet of someone quoting what he just tweeted "Signing off now. That was more than enough Twitter trouble for one morning!"
He sounds a bit stressed though, if you check out his replies. Examples:
@rtoro20: "@elonmusk Can you tweet more please." @elonmusk: "@rtoro20 Really? I already have both feet in my mouth and am levitating on my own idiocy..."
@eveegdmann: "@elonmusk not sure, though, to spend time on politics is the right way. Especially when you stayed away from it by your own choice before." @elonmusk: "@eveegdmann Really don't want to get in politics. I just want to help invent and develop technologies that improve lives. Feels so bizarre."
He seems to feel that people just "don't get" that he's trying to do good by being on the committee. He doesn't seem to understand that most of his critics know what he's trying to do, but see him as being used and falling for a bait of fake "influence". Like a mouse going, "No, you don't understand, if I just get this cheese that's on this trap, it'll feed us all! Stop saying that traps are bad and we shouldn't associate with them - I agree that traps are bad, but look, there's cheese right there!"
Check out his twitter posts. He's completely fallen for the bait, the exact same thing Trump used on his Republican political opponents: convincing them that they "have his ear" so that they self-censor if not outright help him, in order to avoid ruining their chance to "moderate his behavior". Which of course they actually have zero influence on whatsoever.
1) Mission failure does not mean explosion; it means mission failure. Aka, you fail to reach the desired orbit. 2) Explosion does not mean death; Dragon has a launch escape system, unlike the Shuttle. 3) Even if that was "0,04% chance of death", that would be an exceedingly low rate by spaceflight standards.
Exactly what I planned to write. Of all of the things SpaceX has done that hasn't proven unreliable, it's the Merlins. Maybe this will change with increasing reuse, but as it stands....
And I agree, bigger problems likely lie elsewhere. I'm still not that comfortable with their having COPVs lacking an outer liner just sitting around in densified LOX, regardless of how they handle load operations.
No, you should try comprehending the abstract. Solid and liquid rocket motors are about as different as internal combustion engines and steam engines. Pointing to some generic study about some arbitrary solid rocket propellant as if that's supposed to mean anything whatsoever concerning a rocket that does not use solid rocket propellants of any kind just makes you look you don't know anything about the topic being discussed.
Let me rephrase: It sounded like you were saying the lengthwise expansion would indeed occur, but that this wouldn't cause undue stress because the pipe would be allowed to move freely on these supports, thereby allowing movements to easily propagate along the length of the pipe (if not the entire length... I'm not sure how things work out at curves, for instance.)
That is correct. It is guided, but allowed to expand. All the towers have to do is withstand any lateral forces. If the stress in the pipe is sufficient to overcome friction, it moves. If it's not, then it just sits there, either in tension or compression. Pieces of steel existing in tension or compression being perfectly normal in engineering.
Thermal stress is not something you can just ignore, but it's anything but some sort of huge problem to deal with. You either let the thing move in a direction you're comfortable with it moving, or you resist the stresses. Both solutions are widely utilized. Stop acting like basic engineering equals magic.
This is turning a bit pedantic and tangential, though. "It's good that it's so fast!" handwavery is not something I can *conclusively* attack without a lot of serious research and calculating.
The maximum G forces in the car are 0,5g. At this force it would be oriented at 45 from vertical in the tube, so it experiences 1 + cos(45) g downward and sin(45) lateral. Independent of whether the vehicle is moving at 700mph or 70 mph. The radius is calculated so that the g loads remain low. So the speed doesn't change the force on the tube. It does, however, change the duration - it reduces it. Same amount of force, less time.
My overarching point is there aren't good precedents, and the pipe will suffer stresses of a sort that an oil pipeline never has to
In that the total loading in Hyperloop is more than an order of magnitude lower, yes, and that the momentary force of a capsule passing overhead less than fluid hammering in them, yes (hammer cannot happen in Hyperloop, since it contains a compressible gas, and barely any of even that). Or vs. natural gas pipelines, in that the pressure differential with the outside is more than an order of magnitude lower, yes.
It's being given as one of the major advantages of the hyperloop, as if it will automatically be used at maximum theoretical capacity. I'm not sure I follow the logic there. Out of all of the tracks I've ever seen in my life, none of them ever remotely appeared to be operating at full capacity
And once again you make incorrect assumptions that you wouldn't have had you actually read the design document (what is it that drives people to want to discuss something that they've never taken the time to educate themselves on?). Hyperloop's operation is based on 7,4m passengers each way per year. At the maximum launch rate in the document, that's an average of only 7 people per 28-passenger capsule. By contrast, HSR is built on the assumption of an annual ridership of 29.6 to 43.9 million people, for a ride that's four times as long and costs an order of magnitude more.
You just arbitrarily assumed that Hyperloop Alpha assumed that they're constantly operating at full capacity. Why would you do that?
And I was also trying to hint that a massively parallelized terminal setup designed for a very high frequency launch schedule does not sound especially cheap
Right, because nobody's ever loaded multiple vehicles at once in a station that before. Certainly not subways, train stations, roller coasters, and pretty much everything else.
There's a wider discussion of hyperloops out there. Some of them are maglev.
I have stated from the very beginning that I will only be discussing, and defending, Hyperloop
Well, it seemed like you were pretending like the stresses were magically taken care of by these multiaxis gimbaled whatevers.
How could you possibly have gotten that from what I wrote?
"Which is accounted for in the Hyperloop Alpha design document, via the increase allowing the pipe to slide along its length because..." "The expansion would be visible as a millimeters-per-second crawl of the pipe" "The document describes how to deal with thermal expansion in this manner, including the need for the end stations to accommodate the length changes." "whereby the pipe would be allowed to move in a desired direction"
And then I continued into other workable solutions, aka what HSR does. None of them in any way shape or form "magically taken care of by these multiaxis gimbaled whatevers"
I know you don't bother to read design documents before talking about topics, but could you at a bare minimum read the comments of the person you're replying to?
we're talking about pipe designed to hold liquids or gasses, not multi-thousand pound capsules screaming along at 600 MPH.
Back to "did you even read what I wrote previously?". The fact that the loads are only brief is a good thing. And the pipe is inch thick tubular steel. Something with orders of magnitude higher of a bending moment of inertia (resistance to deflection) than HSR rails - the latter of which you hardly seem to think ise some sort of magical technology.
Have you never heard of any engineering project ever that experienced material degradation or failure?
Unless periodically stressed to - and this part is critical - near its tensile limit - carbon steel suffers no discernable fatigue (unlike aluminum, which slowly accumulates fatigue even on bending far from its moment of inertia; if you're not familiar with the concept, google "fatigue limit"). And again to repeat: HSR rails experience far more force than the Hyperloop tube..
Anecdote time: A few years ago, I seriously looked into the possibility of building a house out of steel shipping containers
I made an underground shed made out of one. Fun times.:)
It turns out that when you try to save money by using mass-produced commodity good X for radically different engineering project Y
So using pipe segments to build pipe is a radically different engineering project from using pipe segments to build pipe, using the exact same construction process that everyone else uses?
"Strength" in metallurgy is, I suspect, not a one-dimensional value, especially if we're talking about all kinds of different and novel stresses involved here. Off the top of my head, I saw a documentary once that claimed that it was specifically the decision to use welded beams weakened the Hyatt Regency walkway
The beams were always planned to be welded. It split at the seam because they welded with an electrode with a lower yield strength than the C sections they were joining. The ultimate cause of the failure however was the doubling of the loads on the box beam due to the altered design.
You certainly can make a weld have properties stronger or weaker than the adjacent steel - but that's not what I was referring to. I was referring to the fact that unlike structural aluminum, which relies on its temper to gain half an order of magnitude higher tensile strength than O, basic carbon steels do not, and thus heating does not weaken the pipe itself at the weld.
Anyway, the track is only tiny part of the equation here. We still have cost and maintenance of the jet engine
There is no "jet engine". There is a compressor. You can see a diagram on figure 10 if you want. 0,49kg/s, 20:1 compression - hardly any
If you're looking for a meaningless elongation calculation, steel's linear coefficient of thermal expansion is generally 12 microns per meter per degree kelvin. The distance is 563km. The temperature difference is whatever a person arbitrarily pulls out of a hat - say, 20C. The length change is 135 meters.
But this is, as mentioned, meaningless, because the real world doesn't behave in this simplified way that people like Thunderf00t who have no experience in the field assume. Temperature changes don't directly result in size changes, they result in internal stress changes. An engineer is free to handle internal stress changes in whatever manner they choose, whether to resist them or allow for size changes, and if the latter, to allow them in whatever manner best suits them. And depending on the design you can make it so that the change in temperature is either causing or relieving stress. It's not only extremely well covered territory, but the exact same well-covered territory that HSR faces. Hyperloop's choice of how to handle it is different than HSR's (float the pipe vs. resist it), but both are acceptable engineering choices.
I wouldn't attack Thunderf00t had he not had this habit of repeatedly going off on rants about thing he has no understanding whatsoever about as if he's an expert. He's not. And people shouldn't treat him as such. If he wants to post something about chemistry, then it's fine to take him at his word until proven otherwise. But if he makes some sort of engineering claim, you should inherently take it with a big grain of salt.
ThunderF00t is, always has been, and always will be a moron. You do a disservice to your argument by bringing him up.
d that an effective one-piece pipe like you're describing would expand and contract lengthwise
Which is accounted for in the Hyperloop Alpha design document, via the increase allowing the pipe to slide along its length because - as was mentioned in the last post - it's not rigidly attached to the pylons, but rather held up by a multiaxis damper. The expansion would be visible as a millimeters-per-second crawl of the pipe. The document describes how to deal with thermal expansion in this manner, including the need for the end stations to accommodate the length changes.
Three common methods of accommodating this pipe movement are to 1) provide an expansion joint; 2) allow the system to “freefloat” whereby the pipe would be allowed to move in a desired direction through the use of anchoring and/or guidance, if necessary, taking into account the capability of branch connection or changes in direction which may have resultant harmful bending moments; or 3) utilize the linear movement/deflection capabilities of flexible grooved couplings
It is a standard method to deal with thermal expansion.
That said, that's hardly the only thing they can do. For lower velocity segments, they can simply accommodate expansion by arc radius changes. They can also use the standard HSR approach (HSR also uses continuously welded rail and is thus subject to the exact same issue) for dealing with thermal expansion: laying tracks in the heat of summer. This means that they contract and remain in tension in colder weather, so the thermal expansion just serves to relieve tension rather than physically increasing length. The other thing that HSR does is anchor the rail by heavy concrete blocks, rather than just light wooden sleepers like conventional rail. The force required to move the concrete ties is greater than the stress in the rails.
To put it another way: actual engineers have solved these problems long ago. Which is why you listen to actual engineers rather than listening to a chemist playing armchair engineer like Thunderf00t.
Also, while you're perusing it, calculate the amount of steel used, then look up the price of that much steel pipe, versus how much they're budgeting. And how much typical pipelaying projects cost, relative to length and diameter, versus the estimate. I did. Contrary to what internet quarterbacks who never bothered to read the document before playing amateur engineering critic might say, their budgeting for the track is quite conservative
Using the present tense does not a persuasive argument make.
Hyperloop Alpha is a design document. It already exists, hence present tense.
Those joints remain completely airtight even with a pressure differential of nearly 1 atm?
Why are you acting like 1 ATM pressure differential is a high pressure differential for 1" thick steel pipe to bear? Natural gas pipelines operate at about 17 atm, and that's hardly the highest pipelines go. And orbital welding of pipeline segments is an extremely mature technology, there's nothing at all exotic about it.
Thermal expansion under the California sun doesn't weaken or break that airtight seal?
I'm not even sure that you understand what welding is, let alone orbital welding. There is no "seal". It's a uniform piece of metal. The metal is literally melted by welding, and rehardens into a single piece. Basic carbon steel doesn't weaken from welding (like, say, T6 aluminum does), it can actually get stronger. An orbital pipe welder is an automatic piece of hardware that circles a piece of pipe on its own, connecting two segments; it leaves a perfect, identical, machine-precision weld every time.
There are no "joints". It's just continuous steel. Just like oil and gas pipelines. There's no technological ground being broken in this regard.
Mild earthquakes doesn't weaken or break it?
You really should read the design document before discussing things. No, it's not directly supported by the ground, its supported on the towers by a multiaxis isolation system, which also allows it to shift via thermal expansion / contraction. A big advantage over HSR, which suffers from serious problems with ground shifting under the rails, particularly in earthquakes.
The absorbed force of a 600 MPH capsule weighing lord knows how many pounds going around a curve isn't going to weaken it?
1) Speed is a good thing, it means loadings are only borne for a short period of time. 2) The capsules weigh about a tenth as much as a HSR train. Which is one of the big advantages of the Hyperloop system. 3) Pipe loadings are likewise about an order of magnitude less than that of HSR rails. But spread out over a greater amount of steel.
Seriously, before you hit that reply button, google "Hyperloop Alpha" and read the design document. It won't take all day. I don't want to have to reply to whatever things you're thinking about writing that are already answered in the document.
Slashdot Mirror
Venus is absolutely not uninhabitable.
And as for science, knowing whether Venus is the fate of Earth, or how to determine whether an exoplanet would be a second Earth or a second Venus, is a lot bigger of a question than anything Mars can answer. Venus is not only our closest neighbor and almost the same size, but once had oceans like Earth. And her atmosphere appears locked into this vicious cycle, where she's hot because her CO2 isn't stored as carbonates, but she can't form carbonates because she's too hot. And even if you want to dismiss that as an indirect side effect of water loss due to devolatilization due to a lack of a magnetic field (and ignoring the question of "why" the latter is), that's not the only thing Venus is cautionary about. 500 million years ago it appears that the entire planet, or nearly so, was resurfaced by volcanism. Can such a thing happen here? We can't say so because we have no clue why it happened.
Venus once was another Earth. We want to know what went wrong. It's hard to model the Earth when Venus doesn't work with our models.
Ah, yes - the 20th century was filled with no shortage of disappointments concerning our planetary neighbors.
The unfortunate thing about Venus is, if its atmosphere had stopped at around the height that is today 54-55km, nobody would be talking about Mars as a human habitation destination. Indeed, one proposal for terraforming Venus is to build a whole new surface at that height and just call it good enough ;)
My problem with the name Uranus isn't that stupid, overused joke - it's the fact that it's the only planet named after a Greek, not Roman, god. It should have been Caelus.
I remember as a kid watching reruns of Green Acres on Nick at Night. They had an ad - which my father had to explain to me - which showed the lead actress, with the voiceover: "This is Eva Gabor. Not Zsa Zsa. Eva won't hurt you."
Your standard Venera-style probe consists of the following layers:
1) Outer spherical steel shell
2) Insulation
3) Phase-change material as a constant-temperature heat heat sink
4) Everything that you don't want hot, compressed, or exposed to corrosive chemicals.
The only thing that's hard to keep from happening is the "hot" part, because eventually your phase change material reaches its limits and the temperature starts to rise.
I assume you mean "more data". We've already had the Venera probes, the Pioneer probes, and the Vega probes (including PTFE superpressure balloons - the only airborne vehicles on another world to date).
I just wish we used units that rendered the gas constant unnecessary. I should probably memorize it to more digits than "8,31" so that I don't have to keep looking it up :
Your post is largely correct, with the caveat that with proper insulation, the rate of heat flow to the exterior can be kept surprisingly small. But RTGs are indeed hindered by the external heat that they have to reject waste heat to. Solar power surprisingly actually works on the surface, but at terrible efficiency (if I recall correctly, something like 2.7W/m). And wind indeed has been proposed as a power source. Windspeeds are low, rarely more than a meter per second or so, but due to the high density it's not actually a bad power source. There's even been one wind-propelled rover proposal under investigation (Zephyr).
Indeed, the whole point of long-term Venus landers is indeed not large amounts of power, but basically surface "weather stations" or "seismic stations" that just sit there using a few watts here and there and transmitting results up to a higher power relay.
On the other hand, getting things to the surface of Venus is surprisingly easy. Landis once worked out that you could launch a hollow titanium sphere to Venus, have it aerocapture, and land safety on the surface, without any sort of aeroshell, ablation system or parachute whatsoever. Venus has a big "fluffy" atmosphere for slowing things down, and by the bottom the density is so great that terminal velocity can be survivable for well-built probes.
Except 1) A failure takes out an (expensive) launch pad for half a year, and 2) the FAA won't let you just take a "damn the torpedoes" approach, because these "torpedoes" contain the energy of a small nuclear bomb.
The industry average failure rate is commonly stated at 95%, although that number is biased down by older rockets who which were developed at a time where a higher failure rate was considered more acceptable (it's lower with modern rockets). SpaceX was at 93% after their last accident. I repeat what I wrote: "Not terrible, but not great."
As for mounting satellite before static testing:
The idea was SpaceX's. Operators can opt-out, but as a general rule customers go with whatever the launch provider thinks is best. And to be fair, there is some risk from opting out as well. If something is messed up with how the payload is mounted it might become clear during the static test.
Lastly, I would not call SpaceX's most recent failures "right up front". And while I was willing to give them a pass for their first failure (the short of it: a supplier who lied about their QA process), this last failure falls entirely on their risky decision to store COPVs with no external liner submerged in densified LOX. I certainly wouldn't have taken such a risk. And the design isn't changing. Great that they're trying to reduce buckling and changing their helium loading procedure and all of that, but at the end of the day, composites have poor LOX compatibility, and densification just makes it worse.
What's disingenuous is selecting for comparison launchers that had early problems but leaving out those that didn't.
By rocketry standards, SpaceX's record isn't terrible, but it's not great either.
Because the Soviets didn't have the FAA grounding them until they can prove to a very high degree of confidence that they'd identified and remedied the problem. The Soviets had precisely the opposite attitude. For almost every single Venus mission, for example, they launched in pairs, just in case there was a fault in one launch vehicle / transfer stage or probe en route (and sometimes they'd lose both!)
Indeed. It's equivalent to asking an artist paint a face onto a blur.
It's fine just as it is for a lot of non-legally-questionable uses, such as image compression (smaller number of real pixels to achieve the same aesthetic effect), upscaling old images (picture a high quality upscaler in an emulator for old games, for example), etc.
By the way, this appears to be basically the same thing that Magic Pony Technology already did. Another thing that MPT demonstrated with their software was infinite texture generation - given a fixed size texture, it can create an infinite amount more that "looks like it". Also, a neat thing was its use on images that contained text. If the neural net recognizes a letter, then it can obviously draw the letter in full, clear detail. I've had quite a few PDFs that were exported at too low of a resolution for their images that I would have liked that on; it's no fun having to zoom in and tease out the letters one-by-one manually.
That's the thing, there really is. With launch prices down, satellite tech advancing fast, and a rapidly growing middle class, there's a large demand for commercial launches right now, and it only looks to grow.
My problem with SpaceX's plan isn't the market - that's solid. My concern is that the faster you want to launch, the less you can tolerate failures. The time a failure leaves you unable to launch for is independent of how fast you're launching. The faster you launch, the sooner the time between failures. So an increasingly large percent of your time becomes time down due to failures. The only way to overcome this is to correspondingly boost reliability. Want to 10x launch rates? Better 10x reliability. It's a tall order. SpaceX is already on the low end on reliability (not terrible by rocketry standards, but not great), so they already have a deficit to overcome.
He honestly doesn't seem to realize that. The more of his tweets you read, the more it becomes clear. He honestly thinks he is being / will be listened to and will be a "moderating influence" on Trump.
All of his tweets on the topic, not counting replies:
"The blanket entry ban on citizens from certain primarily Muslim countries is not the best way to address the country’s challenges"
"Many people negatively affected by this policy are strong supporters of the US. They've done right,not wrong & don't deserve to be rejected."
"Please read immigration order. Lmk specific amendments. Will seek advisory council consensus & present to President." (links to executive order)
"Reading the source material is better than reading other people's opinions about the source material" (links to a person saying "Not a trump lover by any means, but after reading the language of the order, it looks far less bad than portrayed by the left")
"Regarding the meeting at the White House:" (links to image of text insisting that he's hoping to use his status on the advisory council to oppose the order, and that all he cares about is building a good future for humanity)
"At my request, the agenda for yesterday's White House meeting went from not mentioning the travel ban to having it be first and foremost"
"In addition, I again raised climate. I believe this is doing good, so will remain on council & keep at it. Doing otherwise would be wrong."
"Many in America don't realize how proud they should be of the legal system. Not perfect, but nowhere is the cause of justice better served."
"Activists should be pushing for more moderates to advise President, not fewer. How could having only extremists advise him possibly be good?"
Retweet of someone quoting what he just tweeted
"Signing off now. That was more than enough Twitter trouble for one morning!"
He sounds a bit stressed though, if you check out his replies. Examples:
@rtoro20: "@elonmusk Can you tweet more please."
@elonmusk: "@rtoro20 Really? I already have both feet in my mouth and am levitating on my own idiocy..."
@eveegdmann: "@elonmusk not sure, though, to spend time on politics is the right way. Especially when you stayed away from it by your own choice before."
@elonmusk: "@eveegdmann Really don't want to get in politics. I just want to help invent and develop technologies that improve lives. Feels so bizarre."
He seems to feel that people just "don't get" that he's trying to do good by being on the committee. He doesn't seem to understand that most of his critics know what he's trying to do, but see him as being used and falling for a bait of fake "influence". Like a mouse going, "No, you don't understand, if I just get this cheese that's on this trap, it'll feed us all! Stop saying that traps are bad and we shouldn't associate with them - I agree that traps are bad, but look, there's cheese right there!"
Check out his twitter posts. He's completely fallen for the bait, the exact same thing Trump used on his Republican political opponents: convincing them that they "have his ear" so that they self-censor if not outright help him, in order to avoid ruining their chance to "moderate his behavior". Which of course they actually have zero influence on whatsoever.
Elon Musk is his newest Chris Christie.
No, I think you do.
1) Mission failure does not mean explosion; it means mission failure. Aka, you fail to reach the desired orbit.
2) Explosion does not mean death; Dragon has a launch escape system, unlike the Shuttle.
3) Even if that was "0,04% chance of death", that would be an exceedingly low rate by spaceflight standards.
Exactly what I planned to write. Of all of the things SpaceX has done that hasn't proven unreliable, it's the Merlins. Maybe this will change with increasing reuse, but as it stands....
And I agree, bigger problems likely lie elsewhere. I'm still not that comfortable with their having COPVs lacking an outer liner just sitting around in densified LOX, regardless of how they handle load operations.
No, you should try comprehending the abstract. Solid and liquid rocket motors are about as different as internal combustion engines and steam engines. Pointing to some generic study about some arbitrary solid rocket propellant as if that's supposed to mean anything whatsoever concerning a rocket that does not use solid rocket propellants of any kind just makes you look you don't know anything about the topic being discussed.
That is correct. It is guided, but allowed to expand. All the towers have to do is withstand any lateral forces. If the stress in the pipe is sufficient to overcome friction, it moves. If it's not, then it just sits there, either in tension or compression. Pieces of steel existing in tension or compression being perfectly normal in engineering.
Thermal stress is not something you can just ignore, but it's anything but some sort of huge problem to deal with. You either let the thing move in a direction you're comfortable with it moving, or you resist the stresses. Both solutions are widely utilized. Stop acting like basic engineering equals magic.
The maximum G forces in the car are 0,5g. At this force it would be oriented at 45 from vertical in the tube, so it experiences 1 + cos(45) g downward and sin(45) lateral. Independent of whether the vehicle is moving at 700mph or 70 mph. The radius is calculated so that the g loads remain low. So the speed doesn't change the force on the tube. It does, however, change the duration - it reduces it. Same amount of force, less time.
In that the total loading in Hyperloop is more than an order of magnitude lower, yes, and that the momentary force of a capsule passing overhead less than fluid hammering in them, yes (hammer cannot happen in Hyperloop, since it contains a compressible gas, and barely any of even that). Or vs. natural gas pipelines, in that the pressure differential with the outside is more than an order of magnitude lower, yes.
And once again you make incorrect assumptions that you wouldn't have had you actually read the design document (what is it that drives people to want to discuss something that they've never taken the time to educate themselves on?). Hyperloop's operation is based on 7,4m passengers each way per year. At the maximum launch rate in the document, that's an average of only 7 people per 28-passenger capsule. By contrast, HSR is built on the assumption of an annual ridership of 29.6 to 43.9 million people, for a ride that's four times as long and costs an order of magnitude more.
You just arbitrarily assumed that Hyperloop Alpha assumed that they're constantly operating at full capacity. Why would you do that?
Right, because nobody's ever loaded multiple vehicles at once in a station that before. Certainly not subways, train stations, roller coasters, and pretty much everything else.
I have stated from the very beginning that I will only be discussing, and defending, Hyperloop
How could you possibly have gotten that from what I wrote?
"Which is accounted for in the Hyperloop Alpha design document, via the increase allowing the pipe to slide along its length because..."
"The expansion would be visible as a millimeters-per-second crawl of the pipe"
"The document describes how to deal with thermal expansion in this manner, including the need for the end stations to accommodate the length changes."
"whereby the pipe would be allowed to move in a desired direction"
And then I continued into other workable solutions, aka what HSR does. None of them in any way shape or form "magically taken care of by these multiaxis gimbaled whatevers"
I know you don't bother to read design documents before talking about topics, but could you at a bare minimum read the comments of the person you're replying to?
Back to "did you even read what I wrote previously?". The fact that the loads are only brief is a good thing. And the pipe is inch thick tubular steel. Something with orders of magnitude higher of a bending moment of inertia (resistance to deflection) than HSR rails - the latter of which you hardly seem to think ise some sort of magical technology.
Unless periodically stressed to - and this part is critical - near its tensile limit - carbon steel suffers no discernable fatigue (unlike aluminum, which slowly accumulates fatigue even on bending far from its moment of inertia; if you're not familiar with the concept, google "fatigue limit"). And again to repeat: HSR rails experience far more force than the Hyperloop tube..
I made an underground shed made out of one. Fun times. :)
So using pipe segments to build pipe is a radically different engineering project from using pipe segments to build pipe, using the exact same construction process that everyone else uses?
The beams were always planned to be welded. It split at the seam because they welded with an electrode with a lower yield strength than the C sections they were joining. The ultimate cause of the failure however was the doubling of the loads on the box beam due to the altered design.
You certainly can make a weld have properties stronger or weaker than the adjacent steel - but that's not what I was referring to. I was referring to the fact that unlike structural aluminum, which relies on its temper to gain half an order of magnitude higher tensile strength than O, basic carbon steels do not, and thus heating does not weaken the pipe itself at the weld.
There is no "jet engine". There is a compressor. You can see a diagram on figure 10 if you want. 0,49kg/s, 20:1 compression - hardly any
If you're looking for a meaningless elongation calculation, steel's linear coefficient of thermal expansion is generally 12 microns per meter per degree kelvin. The distance is 563km. The temperature difference is whatever a person arbitrarily pulls out of a hat - say, 20C. The length change is 135 meters.
But this is, as mentioned, meaningless, because the real world doesn't behave in this simplified way that people like Thunderf00t who have no experience in the field assume. Temperature changes don't directly result in size changes, they result in internal stress changes. An engineer is free to handle internal stress changes in whatever manner they choose, whether to resist them or allow for size changes, and if the latter, to allow them in whatever manner best suits them. And depending on the design you can make it so that the change in temperature is either causing or relieving stress. It's not only extremely well covered territory, but the exact same well-covered territory that HSR faces. Hyperloop's choice of how to handle it is different than HSR's (float the pipe vs. resist it), but both are acceptable engineering choices.
I wouldn't attack Thunderf00t had he not had this habit of repeatedly going off on rants about thing he has no understanding whatsoever about as if he's an expert. He's not. And people shouldn't treat him as such. If he wants to post something about chemistry, then it's fine to take him at his word until proven otherwise. But if he makes some sort of engineering claim, you should inherently take it with a big grain of salt.
ThunderF00t is, always has been, and always will be a moron. You do a disservice to your argument by bringing him up.
Which is accounted for in the Hyperloop Alpha design document, via the increase allowing the pipe to slide along its length because - as was mentioned in the last post - it's not rigidly attached to the pylons, but rather held up by a multiaxis damper. The expansion would be visible as a millimeters-per-second crawl of the pipe. The document describes how to deal with thermal expansion in this manner, including the need for the end stations to accommodate the length changes.
Google, for example, "accommodating pipe thermal growth". Here's the #2 hit I get.
It is a standard method to deal with thermal expansion.
That said, that's hardly the only thing they can do. For lower velocity segments, they can simply accommodate expansion by arc radius changes. They can also use the standard HSR approach (HSR also uses continuously welded rail and is thus subject to the exact same issue) for dealing with thermal expansion: laying tracks in the heat of summer. This means that they contract and remain in tension in colder weather, so the thermal expansion just serves to relieve tension rather than physically increasing length. The other thing that HSR does is anchor the rail by heavy concrete blocks, rather than just light wooden sleepers like conventional rail. The force required to move the concrete ties is greater than the stress in the rails.
To put it another way: actual engineers have solved these problems long ago. Which is why you listen to actual engineers rather than listening to a chemist playing armchair engineer like Thunderf00t.
Also, while you're perusing it, calculate the amount of steel used, then look up the price of that much steel pipe, versus how much they're budgeting. And how much typical pipelaying projects cost, relative to length and diameter, versus the estimate. I did. Contrary to what internet quarterbacks who never bothered to read the document before playing amateur engineering critic might say, their budgeting for the track is quite conservative
Hyperloop Alpha is a design document. It already exists, hence present tense.
Why are you acting like 1 ATM pressure differential is a high pressure differential for 1" thick steel pipe to bear? Natural gas pipelines operate at about 17 atm, and that's hardly the highest pipelines go. And orbital welding of pipeline segments is an extremely mature technology, there's nothing at all exotic about it.
I'm not even sure that you understand what welding is, let alone orbital welding. There is no "seal". It's a uniform piece of metal. The metal is literally melted by welding, and rehardens into a single piece. Basic carbon steel doesn't weaken from welding (like, say, T6 aluminum does), it can actually get stronger. An orbital pipe welder is an automatic piece of hardware that circles a piece of pipe on its own, connecting two segments; it leaves a perfect, identical, machine-precision weld every time.
There are no "joints". It's just continuous steel. Just like oil and gas pipelines. There's no technological ground being broken in this regard.
You really should read the design document before discussing things. No, it's not directly supported by the ground, its supported on the towers by a multiaxis isolation system, which also allows it to shift via thermal expansion / contraction. A big advantage over HSR, which suffers from serious problems with ground shifting under the rails, particularly in earthquakes.
1) Speed is a good thing, it means loadings are only borne for a short period of time.
2) The capsules weigh about a tenth as much as a HSR train. Which is one of the big advantages of the Hyperloop system.
3) Pipe loadings are likewise about an order of magnitude less than that of HSR rails. But spread out over a greater amount of steel.
Seriously, before you hit that reply button, google "Hyperloop Alpha" and read the design document. It won't take all day. I don't want to have to reply to whatever things you're thinking about writing that are already answered in the document.