Of course it saves the rhinos. You put 100 times more fake stuff on the market and the price for rhino horn collapses, meaning people stop hunting them.
The brilliant part is that this makes use of something that's normally a bad thing - China's extensive peddling in fakes - to achieve a good result. I doubt it'll stop the really high end of the market, the sort of people who would instruct their buyer to send what they buy sent off to a lab (I don't think some rhino DNA alone would fool a lab, surely it looks different under microscopic examination), but for the rest of the market, it's a neat idea.
Why do you think over a dozen observatories have been built there? Think it's cheap to sent giant pieces of delicate scientific equipment from the mainland? TFA doesn't even mention the actual reason why Mauna Kea is one of the best places on the planet for optical telescopes: seeing conditions (aka, how much celestial objects "twinkle" on average. Outside of deep Antarctica (Dome A, not far east of the South Pole), there's no other better known location on the planet (a couple are pretty close, like La Palma and La Silla, but none exceed it). Good seeing requires high altitude with the area around being as perfectly flat and uniform as possible for hundreds of kilometers.
For optical telescopes, seeing is the most critical factor for resolving fine details. And this telescope is all about resolving fine details. Adaptive optics help counter seeing problems, but the better your seeing baseline, the better the final result.
They mentioned that the flow temperatures recorded in the hot pixels are colder than typical basaltic / rhyolitic flows and were speculating that they didn't catch freshly erupting material, but rather material that had a little time to cool. But I can't help but wonder.... does Venus have carbonatite flows? They're colder, and if there's anything Venus isn't short on, it's carbonic compounds...
(BTW, with those not familiar with carbonatite lava, its really weird stuff - incredibly fast-flowing and smooth (often less viscous than water), erupts looking black or dark gray like oil, doesn't (visibly) glow during the day (just a fast moving black substance), at night it has a weird maroon glow, and it oxidizes to bright white as it ages)
Ahh I think I see the problem, it was giving me the results for the city of Hyde near Manchester, not Hyde Park!
Okay, so according to the site, Dorking or Guildford to London is about an hour by rail during rush hour, 45 minutes during off-peak (15-20 quid each way); while according to Google Maps it's 1-2 hours during rush hour, 60-80 minutes during off-peak.
When I was in the UK, I found a strong inverse correlation between "how close I was to London" and "how polite and friendly people were". I could only verify the rule out to Northern Ireland, but if it continues to hold up, then the people of the Pitcairn Islands have to be the friendliest people on Earth;)
Victoria shows a much faster time - a bit over one hour and 15.70 quid. Probably because it has only one change (Hyde Park had three) and because I'm searching longer in advance. It's also possible that some routes were sold out at the last search time.
Still over an hour by rail, 1-2 hours by car, during rush hour (I'm searching for departure time 17:30 on a weekday each time - earlier it was today, now I'm searching for Monday)
I love how you called it an "official area of outstanding natural beauty".;) Are the swans trained to stand in just the right places?;)
I wasn't even thinking of standing-room only trains, I was picturing being in with a bunch of people sitting down. Yeah, crammed together standing up like a Tokyo subway would be even worse! And you have to "work flexible hours" to be able to avoid that? Geez...
OMG, I just looked up the Surrey Hills, and its literal name as marked on the map is "Surrey Hills Area of Outstanding Natural Beauty". I thought you were just reading off of a brochure or something - that's hilarious!
I just went to a UK rail planner website - http://ojp.nationalrail.co.uk/ - and picked a site downtown at random - Hyde Park (all stations) - and the nearest town I saw to "Surrey Hills Area of Outstanding Natural Beauty" (snicker), which was Guildford (all stations). The cheapest ticket is 89 bloody pounds and takes 4 hours 28 minutes. I then tried to Dorking (all stations) on the other side of SHAONB... same cost, same time.
Okay, so maybe it's absurdly long by rail not but not by car? Google Maps says 1-2 hours each way. Judging from the current traffic report, much of it spent dawdling along in-town.
(BTW, your opinions of "outstanding" are rather different than mine, apparently;) )
I don't get why people want to live in cities - I really just don't understand it. For example:
From stations within a few minutes walk of where I live, I can be at Victoria station in less than 20 minutes and London Bridge in less than 25.
By comparison, from my land in 25 minutes I drive past my neighbor's waterfall on the other side of my canyon, past the fjord, down between the mountains and the ocean and into town. You share a ride with little personal space with strangers in an underground tunnel.
I just don't understand why people want that kind of life.
Okay, okay, the bottom 90% of the vehicle that gets to a translunar trajectory is real because we saw it go up and disappear. But the top 10% was faked. That makes sense.
What sort of nuclear engine are you envisioning that would match the thrust of bombs boiling off the asteroid's surface in a big plasma wave?
Anyway, as for the question at hand, there's an obvious solution: design and build nuclear bombs for the purpose that would make terrible weapons. Make them way too big to fit on ICBMs, requiring giant, easy to target, support infrastructure-heavy boosters to get into space. Which of course, when you're talking about NEOs, you want "huge" anyway, Tsar Bomba or bigger in size. Effective weapons against Earth targets are much smaller, hundreds of kilotonnes to a few megatonnes in MIRV configruation. Deflection devices would just be massive layer-cake Teller-Ulam systems.
Anyway, detection is top priority. Construction and testing of deflection prototypes is second priority. As for whether we should keep things on hand, if we have a good enough detection network, that may not be necessary - it may be enough simply to have a tested design on hand that we could build and field in a few years' time if there came a need.
More than that not all of it hits you is that it doesn't all hit you at the same time. Earth has a massive radiative surface area; any delays between deposits of energy are hugely important.
Anyway, the AC who replied first got it exactly right. Nuclear weapons in space are X-ray weapons that deliver force by boiling away the surfaces of objects (even at a distance). Not only is there an immediate direct effect from the boiling off of mass, but you're also creating a coma around the object which will also have an effect by increasing the force of the solar wind on it. It's like giving the object a magnetic sail.
Redirection really isn't inconceivable.... given enough time. But "time" is really the key issue. You're not going to redirect a large asteroid days before impact. But years in advance, that's quite doable for reasonable sized bodies.
Indeed, while it's not discussed in the Hyperloop Alpha plans (surely they don't want to complicate the issue at this stage), there's no reason why one couldn't. The main challenge is this isn't some sort of freight switch, at such high speeds you have exceedingly tight tolerances. I almost wonder if the best solution wouldn't just be to briefly retract the skis a centimeter or so for just the brief moment where the craft passes over the switching point - not long enough to "fall" by any significant amount. That would eliminate the need to align the pipes to sub-millimeter precision.
Broad networks would be pretty interesting concept... a hydrogen-filled Hyperloop concept could realistically do LA to NYC in an hour and a half. If you raise the temperature of the rarified hydrogen (which at such low pressures its a terrible conductor), the only limit to speed would be accel/decel/bending G-forces. You could really get anywhere, fast.
(Come to think of it, I wouldn't be surprised if the rarified gas temperature inside ends up significantly hotter than the pipeline walls/external air on its own just from compression heating - at such low pressures, I doubt that it loses its heat very quickly in the five minutes between capsules... even regular air might have a far higher speed of sound than Hyperloop Alpha accounts for)
At either end, of course, you have to take some form of local transport - for those without a car, local trains/buses/etc. But given that Hyperloop capsules are designed to operate on electric-driven wheels at low speeds (since there's little lift at low speeds), eventually even the need to switch to local transport might not hold. What a coup that would be if the Hyperloop capsule wheels could run on standard gauge;) Think about it: the capsules are 2,23m in diameter and standard gauge is 1,435m rails, 3.15m max width... I mean, it's a perfect fit.
Unfortunately, where I am is unlikely to see anything like Hyperloop for a long time;) (Iceland) We're the size of Kentucky and really mountainous, with one of the world's lowest population densities (though the pipeline aspect would be nice to prevent weather delays... though it better be built to tolerate high winds!)
1. Nor can you breathe in the environment out your window in an airplane. Your point being?
2. "Precision" was listed as one of the examples of where Hyperloop has greater costs than pipelines. But it also has significantly reduced costs in others like, as mentioned, the lack of highly flammable and environment-contaminating contents (also significantly reduced thermal management challanges, far fewer "pumping" stations containing far lower-wear hardware, etc). The environmental and fire issues are the biggest; getting approval for these and all of the features required to gain approval make up a large portion of a pipeline's total cost.
The Hyperloop Alpha design goes in significant detail toward how they plan to achieve the precision, and it's quite reasonable. The segments are to be radially welded in an automated fashion just like an ordinary modern pipeline. However, they add a subsequent step of running a polishing vehicle down the center of the pipeline. It spins a circular sander / polisher (the size of the pipe's inner diameter) as it goes, ensuring that the entire inside matches a precise radius.
I see nothing unreasonable about this approach. Not that all the engineering work is done, of course. In particular, I'm not sure how well their thermal expansion concept would work out in practice - it'll take test hardware to find that out for sure. But these aren't the sort of things that should stop the project from moving on to the stage of building small-scale test hardware.
3) That only applies if you hit a wall. Believe it or not, the point of Hyperloop isn't to shoot people into walls at high speed;)
Hyperloop capsules lose so little energy to their exterior environment that by far most of their journey is spent drifting. If they were dumping energy into the pipeline, this would of course not be possible.
5) There were no Hyperloop proposals from the 1930s and 1940s. See point #1: Hyperloop Is Not A Vactrain. It's a channel for ground-effect aircraft that utilize small compressors to prevent a pressure buildup.
Indeed, hence the "very high altitude". The key point is that there's still enough pressure that it has aerodynamic effects (for both good and bad). This differs fundamentally from a vactrain where it's critical that there are effectively no aerodynamic effects, or you end up pushing a column of air.
It gives you the option to go faster where you have sufficiently straight paths - it doesn't mean you have to go faster all the time. While paths straight enough for extreme speed travel are somewhat limited in California, in other locations, such as the US midwest, such straight paths are the norm.
The article's understanding of things is no better.
The reason we don't use Pu238 more as a primary power source isn't NIMBYs - it's because we're almost out of it and it's absurdly expensive. Pu-238 isn't a "waste product" (except as mixed in with other isotopes and costing a fortune to isolate), it's a manufactured product - and with all transmutation, that means "slow" and "taking up neutronicity that could otherwise be going towards generating power". The plutonium to fuel Philae would have not only cost us a lot but also robbed us of the potential of an outer planets mission until our work to increase plutonium production catch up to our consumption.. It's just not worth it.
I agree with the author about heaters - sort of - but that's really a rather minor point compared to the bigger picture. As it stands, no, they should not have powered Philae with an RTG. And be freaking patient, Philae got to observe the surface when it was cold and is now getting to observe it hotter than we ever thought we'd get the chance to observe. And more to the point, you can't shut off an RTG or a radiothermal heater. Meaning if Philae had been nuclear, it'd be overheating today.
1. All the diagrams give the impression that it will be like people flying through tubes as in Futurama. Instead you will be sealed inside a metallic "bullet", that runs in a metallic tube - no windows for you (sort of like James Bond in The Living Daylights).
Rather than windows, it's to have large digital wall displays that show the outside as if you had giant picture windows. This is the direction airplanes are looking to move in the future as well. Tests run by researchers have shown it to be well received by passengers.
It's a pity if you have any sort of claustrophobia.
The seats are actually quite roomy - check out the dimensions in the Hyperloop alpha document.
2. While the device doesn't run in a complete vacuum, it runs in an atmosphere that is low to the point of being unbreathable. But the device doesn't contain any onboard air supply
Yes, it does. Section 4.5.2. Same system as on an airplane.
3. There was no indication that the loop itself was anything more than a single tube.
It's two tubes, one for each direction. In the event of a long term outage, the one open tube can be periodically reversed to allow traffic in both directions, at a cost of throughput.
So if a device fails, all devices that are already in transit and behind it are screwed (see 2 above).
All capsules have mechanical braking systems and are spaced five minutes apart, automatically triggered in the event of an obstruction. They also all have powered wheels for low-speed travel. Section 3.5.2.
It'd be nice if you'd read the document before complaining about the concept.
On the front of how the concept can be significantly improved upon, here's one: pumping is a very small fraction of the total costs. You could significantly increase the pumping and not have a significant impact on the costs. If you increase the pumping by, say, an additional 4x and inject water vapor, then you will achieve an 80% water vapor atmosphere (water does not condense at such low pressures). This offers a ~40% increase in the speed of sound and thus the maximum speed of the vehicle and reduces its resistance at a given speed.
One can take it further and inject hydrogen instead of water vapor. Most of the downsides that immediately come to mind don't actually turn out to be problems in practice - at such low pressures it's not flammable even if mixed with air, such low pressures aren't an embrittlement risk, the quantity of hydrogen needed is trivially small and thus costs little and poses little ozone hazard, etc. It's basically still "nearly a vaccuum", just with trace hydrogen rather than trace air. Pure hydrogen allows a maximum velocity nearly 4x that of the standard Hyperloop approach.
(Helium is another option, though not quite as good as hydrogen and more expensive. Also, if one wants to go faster and with less resistance than hydrogen, then there's only two options: 1) hot hydrogen, and 2) hard vacuum with maglev (aka, not hyperloop))
1) It's not a vactrain. It's not even that similar to a vactrain. It functions like a very high altitude aircraft, with such rarified air (and the ground-effect surface for lift) being provided by a tube. Nothing is "sucking" or "pushing" it, and nor is it maglev. The compressor at the front exists to stop a column of higher pressure air from building up in front of it, not for propulsion.
2) It is not a train. Rates for building train tracks, rail bridges, etc, are not applicable. Of human structures it's most similar to, an oil pipeline is the most apt comparison - very long, continuously welded elevated tubular steel segments capable of withstanding a pressure differential. It has some disadvantages versus a pipeline, such as much tighter tolerances, as well as some advantages, such as not containing environmentally-hazardous flammable materials. A full comparative list is too long to go into at the moment.
3) Like a pipeline and unlike rail, costs for elevating it are significantly reduced because it doesn't experience wide load swings. The cars are an order of magnitude lighter than a high speed train and thus exert an order of magnitude less loading as they pass (and only briefly). The difference in throughput is compensated for by much higher launch frequency via computer control. With dramatically reduced loading comes dramatically reduced support structure costs - more akin to the supports on the Disney Monorail than that of a rail bridge.
4) It is not meant (as per the source) to be an exact replacement for rail; it's meant to be an intermediary transportation system between rail and air travel.
5) Yes, the original design has flaws. No, none of them are fundamental. Yes, the concept can be significantly improved upon.
Slashdot Mirror
The longitude center of the eastern hemisphere is 90 degrees east longitude. Dome A is about 80 degrees east longitude.
Of course it saves the rhinos. You put 100 times more fake stuff on the market and the price for rhino horn collapses, meaning people stop hunting them.
The brilliant part is that this makes use of something that's normally a bad thing - China's extensive peddling in fakes - to achieve a good result. I doubt it'll stop the really high end of the market, the sort of people who would instruct their buyer to send what they buy sent off to a lab (I don't think some rhino DNA alone would fool a lab, surely it looks different under microscopic examination), but for the rest of the market, it's a neat idea.
Why do you think over a dozen observatories have been built there? Think it's cheap to sent giant pieces of delicate scientific equipment from the mainland? TFA doesn't even mention the actual reason why Mauna Kea is one of the best places on the planet for optical telescopes: seeing conditions (aka, how much celestial objects "twinkle" on average. Outside of deep Antarctica (Dome A, not far east of the South Pole), there's no other better known location on the planet (a couple are pretty close, like La Palma and La Silla, but none exceed it). Good seeing requires high altitude with the area around being as perfectly flat and uniform as possible for hundreds of kilometers.
For optical telescopes, seeing is the most critical factor for resolving fine details. And this telescope is all about resolving fine details. Adaptive optics help counter seeing problems, but the better your seeing baseline, the better the final result.
You know, I should really learn to google things before I suggest "new" ideas ;)
They mentioned that the flow temperatures recorded in the hot pixels are colder than typical basaltic / rhyolitic flows and were speculating that they didn't catch freshly erupting material, but rather material that had a little time to cool. But I can't help but wonder.... does Venus have carbonatite flows? They're colder, and if there's anything Venus isn't short on, it's carbonic compounds...
(BTW, with those not familiar with carbonatite lava, its really weird stuff - incredibly fast-flowing and smooth (often less viscous than water), erupts looking black or dark gray like oil, doesn't (visibly) glow during the day (just a fast moving black substance), at night it has a weird maroon glow, and it oxidizes to bright white as it ages)
(Just one of many unusual types of volcano :) )
Ahh I think I see the problem, it was giving me the results for the city of Hyde near Manchester, not Hyde Park!
Okay, so according to the site, Dorking or Guildford to London is about an hour by rail during rush hour, 45 minutes during off-peak (15-20 quid each way); while according to Google Maps it's 1-2 hours during rush hour, 60-80 minutes during off-peak.
When I was in the UK, I found a strong inverse correlation between "how close I was to London" and "how polite and friendly people were". I could only verify the rule out to Northern Ireland, but if it continues to hold up, then the people of the Pitcairn Islands have to be the friendliest people on Earth ;)
Victoria shows a much faster time - a bit over one hour and 15.70 quid. Probably because it has only one change (Hyde Park had three) and because I'm searching longer in advance. It's also possible that some routes were sold out at the last search time.
Still over an hour by rail, 1-2 hours by car, during rush hour (I'm searching for departure time 17:30 on a weekday each time - earlier it was today, now I'm searching for Monday)
No, you're right - you're a serf locked into a large city against your will. My mistake.
I love how you called it an "official area of outstanding natural beauty". ;) Are the swans trained to stand in just the right places? ;)
I wasn't even thinking of standing-room only trains, I was picturing being in with a bunch of people sitting down. Yeah, crammed together standing up like a Tokyo subway would be even worse! And you have to "work flexible hours" to be able to avoid that? Geez...
OMG, I just looked up the Surrey Hills, and its literal name as marked on the map is "Surrey Hills Area of Outstanding Natural Beauty". I thought you were just reading off of a brochure or something - that's hilarious!
I just went to a UK rail planner website - http://ojp.nationalrail.co.uk/ - and picked a site downtown at random - Hyde Park (all stations) - and the nearest town I saw to "Surrey Hills Area of Outstanding Natural Beauty" (snicker), which was Guildford (all stations). The cheapest ticket is 89 bloody pounds and takes 4 hours 28 minutes. I then tried to Dorking (all stations) on the other side of SHAONB... same cost, same time.
Okay, so maybe it's absurdly long by rail not but not by car? Google Maps says 1-2 hours each way. Judging from the current traffic report, much of it spent dawdling along in-town.
(BTW, your opinions of "outstanding" are rather different than mine, apparently ;) )
Technically a fjord is a glacier-cut U-shaped valley with the bottom submerged. There are some in Scotland but none that I'm aware of in England.
Since when is London not an oppressive dystopian nightmare?
I don't get why people want to live in cities - I really just don't understand it. For example:
By comparison, from my land in 25 minutes I drive past my neighbor's waterfall on the other side of my canyon, past the fjord, down between the mountains and the ocean and into town. You share a ride with little personal space with strangers in an underground tunnel.
I just don't understand why people want that kind of life.
I'm not sure that the people he's meeting are as happy with him as he thinks.
Sounds to me like a polite way of saying "It's it about time that you get the F* out of our country?"
Clearly fake. I can tell from some of the pixels.
Okay, okay, the bottom 90% of the vehicle that gets to a translunar trajectory is real because we saw it go up and disappear. But the top 10% was faked. That makes sense.
What sort of nuclear engine are you envisioning that would match the thrust of bombs boiling off the asteroid's surface in a big plasma wave?
Anyway, as for the question at hand, there's an obvious solution: design and build nuclear bombs for the purpose that would make terrible weapons. Make them way too big to fit on ICBMs, requiring giant, easy to target, support infrastructure-heavy boosters to get into space. Which of course, when you're talking about NEOs, you want "huge" anyway, Tsar Bomba or bigger in size. Effective weapons against Earth targets are much smaller, hundreds of kilotonnes to a few megatonnes in MIRV configruation. Deflection devices would just be massive layer-cake Teller-Ulam systems.
Anyway, detection is top priority. Construction and testing of deflection prototypes is second priority. As for whether we should keep things on hand, if we have a good enough detection network, that may not be necessary - it may be enough simply to have a tested design on hand that we could build and field in a few years' time if there came a need.
More than that not all of it hits you is that it doesn't all hit you at the same time. Earth has a massive radiative surface area; any delays between deposits of energy are hugely important.
Anyway, the AC who replied first got it exactly right. Nuclear weapons in space are X-ray weapons that deliver force by boiling away the surfaces of objects (even at a distance). Not only is there an immediate direct effect from the boiling off of mass, but you're also creating a coma around the object which will also have an effect by increasing the force of the solar wind on it. It's like giving the object a magnetic sail.
Redirection really isn't inconceivable.... given enough time. But "time" is really the key issue. You're not going to redirect a large asteroid days before impact. But years in advance, that's quite doable for reasonable sized bodies.
Indeed, while it's not discussed in the Hyperloop Alpha plans (surely they don't want to complicate the issue at this stage), there's no reason why one couldn't. The main challenge is this isn't some sort of freight switch, at such high speeds you have exceedingly tight tolerances. I almost wonder if the best solution wouldn't just be to briefly retract the skis a centimeter or so for just the brief moment where the craft passes over the switching point - not long enough to "fall" by any significant amount. That would eliminate the need to align the pipes to sub-millimeter precision.
Broad networks would be pretty interesting concept... a hydrogen-filled Hyperloop concept could realistically do LA to NYC in an hour and a half. If you raise the temperature of the rarified hydrogen (which at such low pressures its a terrible conductor), the only limit to speed would be accel/decel/bending G-forces. You could really get anywhere, fast.
(Come to think of it, I wouldn't be surprised if the rarified gas temperature inside ends up significantly hotter than the pipeline walls/external air on its own just from compression heating - at such low pressures, I doubt that it loses its heat very quickly in the five minutes between capsules... even regular air might have a far higher speed of sound than Hyperloop Alpha accounts for)
At either end, of course, you have to take some form of local transport - for those without a car, local trains/buses/etc. But given that Hyperloop capsules are designed to operate on electric-driven wheels at low speeds (since there's little lift at low speeds), eventually even the need to switch to local transport might not hold. What a coup that would be if the Hyperloop capsule wheels could run on standard gauge ;) Think about it: the capsules are 2,23m in diameter and standard gauge is 1,435m rails, 3.15m max width... I mean, it's a perfect fit.
Unfortunately, where I am is unlikely to see anything like Hyperloop for a long time ;) (Iceland) We're the size of Kentucky and really mountainous, with one of the world's lowest population densities (though the pipeline aspect would be nice to prevent weather delays... though it better be built to tolerate high winds!)
1. Nor can you breathe in the environment out your window in an airplane. Your point being?
2. "Precision" was listed as one of the examples of where Hyperloop has greater costs than pipelines. But it also has significantly reduced costs in others like, as mentioned, the lack of highly flammable and environment-contaminating contents (also significantly reduced thermal management challanges, far fewer "pumping" stations containing far lower-wear hardware, etc). The environmental and fire issues are the biggest; getting approval for these and all of the features required to gain approval make up a large portion of a pipeline's total cost.
The Hyperloop Alpha design goes in significant detail toward how they plan to achieve the precision, and it's quite reasonable. The segments are to be radially welded in an automated fashion just like an ordinary modern pipeline. However, they add a subsequent step of running a polishing vehicle down the center of the pipeline. It spins a circular sander / polisher (the size of the pipe's inner diameter) as it goes, ensuring that the entire inside matches a precise radius.
I see nothing unreasonable about this approach. Not that all the engineering work is done, of course. In particular, I'm not sure how well their thermal expansion concept would work out in practice - it'll take test hardware to find that out for sure. But these aren't the sort of things that should stop the project from moving on to the stage of building small-scale test hardware.
3) That only applies if you hit a wall. Believe it or not, the point of Hyperloop isn't to shoot people into walls at high speed ;)
Hyperloop capsules lose so little energy to their exterior environment that by far most of their journey is spent drifting. If they were dumping energy into the pipeline, this would of course not be possible.
5) There were no Hyperloop proposals from the 1930s and 1940s. See point #1: Hyperloop Is Not A Vactrain. It's a channel for ground-effect aircraft that utilize small compressors to prevent a pressure buildup.
Indeed, hence the "very high altitude". The key point is that there's still enough pressure that it has aerodynamic effects (for both good and bad). This differs fundamentally from a vactrain where it's critical that there are effectively no aerodynamic effects, or you end up pushing a column of air.
It gives you the option to go faster where you have sufficiently straight paths - it doesn't mean you have to go faster all the time. While paths straight enough for extreme speed travel are somewhat limited in California, in other locations, such as the US midwest, such straight paths are the norm.
The article's understanding of things is no better.
The reason we don't use Pu238 more as a primary power source isn't NIMBYs - it's because we're almost out of it and it's absurdly expensive. Pu-238 isn't a "waste product" (except as mixed in with other isotopes and costing a fortune to isolate), it's a manufactured product - and with all transmutation, that means "slow" and "taking up neutronicity that could otherwise be going towards generating power". The plutonium to fuel Philae would have not only cost us a lot but also robbed us of the potential of an outer planets mission until our work to increase plutonium production catch up to our consumption.. It's just not worth it.
I agree with the author about heaters - sort of - but that's really a rather minor point compared to the bigger picture. As it stands, no, they should not have powered Philae with an RTG. And be freaking patient, Philae got to observe the surface when it was cold and is now getting to observe it hotter than we ever thought we'd get the chance to observe. And more to the point, you can't shut off an RTG or a radiothermal heater. Meaning if Philae had been nuclear, it'd be overheating today.
Rather than windows, it's to have large digital wall displays that show the outside as if you had giant picture windows. This is the direction airplanes are looking to move in the future as well. Tests run by researchers have shown it to be well received by passengers.
The seats are actually quite roomy - check out the dimensions in the Hyperloop alpha document.
Yes, it does. Section 4.5.2. Same system as on an airplane.
It's two tubes, one for each direction. In the event of a long term outage, the one open tube can be periodically reversed to allow traffic in both directions, at a cost of throughput.
All capsules have mechanical braking systems and are spaced five minutes apart, automatically triggered in the event of an obstruction. They also all have powered wheels for low-speed travel. Section 3.5.2.
It'd be nice if you'd read the document before complaining about the concept.
On the front of how the concept can be significantly improved upon, here's one: pumping is a very small fraction of the total costs. You could significantly increase the pumping and not have a significant impact on the costs. If you increase the pumping by, say, an additional 4x and inject water vapor, then you will achieve an 80% water vapor atmosphere (water does not condense at such low pressures). This offers a ~40% increase in the speed of sound and thus the maximum speed of the vehicle and reduces its resistance at a given speed.
One can take it further and inject hydrogen instead of water vapor. Most of the downsides that immediately come to mind don't actually turn out to be problems in practice - at such low pressures it's not flammable even if mixed with air, such low pressures aren't an embrittlement risk, the quantity of hydrogen needed is trivially small and thus costs little and poses little ozone hazard, etc. It's basically still "nearly a vaccuum", just with trace hydrogen rather than trace air. Pure hydrogen allows a maximum velocity nearly 4x that of the standard Hyperloop approach.
(Helium is another option, though not quite as good as hydrogen and more expensive. Also, if one wants to go faster and with less resistance than hydrogen, then there's only two options: 1) hot hydrogen, and 2) hard vacuum with maglev (aka, not hyperloop))
1) It's not a vactrain. It's not even that similar to a vactrain. It functions like a very high altitude aircraft, with such rarified air (and the ground-effect surface for lift) being provided by a tube. Nothing is "sucking" or "pushing" it, and nor is it maglev. The compressor at the front exists to stop a column of higher pressure air from building up in front of it, not for propulsion.
2) It is not a train. Rates for building train tracks, rail bridges, etc, are not applicable. Of human structures it's most similar to, an oil pipeline is the most apt comparison - very long, continuously welded elevated tubular steel segments capable of withstanding a pressure differential. It has some disadvantages versus a pipeline, such as much tighter tolerances, as well as some advantages, such as not containing environmentally-hazardous flammable materials. A full comparative list is too long to go into at the moment.
3) Like a pipeline and unlike rail, costs for elevating it are significantly reduced because it doesn't experience wide load swings. The cars are an order of magnitude lighter than a high speed train and thus exert an order of magnitude less loading as they pass (and only briefly). The difference in throughput is compensated for by much higher launch frequency via computer control. With dramatically reduced loading comes dramatically reduced support structure costs - more akin to the supports on the Disney Monorail than that of a rail bridge.
4) It is not meant (as per the source) to be an exact replacement for rail; it's meant to be an intermediary transportation system between rail and air travel.
5) Yes, the original design has flaws. No, none of them are fundamental. Yes, the concept can be significantly improved upon.
Back to your regularly scheduled thread.