Hyperloop Bankrupt and Busted.

[wanderingfool2]

20 minutes ago, Uttamattamakin said:

This does not quite work like that.  Drag forces are non linear.  So, a small amount of drag force will have a greater effect at higher velocity.  

Actually it does.  I never said they were linear; but we are comparing variables which means yes there is a relationship between density and the aerodynamics and the square gets cancelled out

 

Notice on that section I wasn't referring to velocity because velocity doesn't come into play as they cancel each other out when comparing the forces [as I previously had stated in the numbers a reduction to 1/4 atm gives you ~2x the velocity...but that means nothing when comparing atm vs aerodynamic efficiency].

 

This is still not the entirety

https://www.grc.nasa.gov/www/k-12/VirtualAero/BottleRocket/airplane/dragco.html#:~:text=The drag coefficient Cd is,times the reference area A.&text=This equation gives us a,value for the drag coefficient.

Cd = D / (A * .5 * r * V^2)

https://by.genie.uottawa.ca/~mcg3341/AerodynamicsOfHighSpeedTrains.pdf

 

Of course we are comparing D in this example, instead of calculating the Cd.

D₀ = Cd * A * 0.5 * r * V^2

 

We are comparing the effects of lets say lowing Cd by lets say x, vs the r variable (density) by x

 

D₁ = Cd/x * A * 0.5 * r * V^2

vs

D₁ = Cd * A * 0.5 * r/x * V^2

 

 

Both of which simplify to the following

D1 = (D0)/x

 

So yea, It's like I was saying, if you are comparing making it more aerodynamic vs lowering the air pressure there is a linear relationship between the two.

 

Modify the coefficient of drag down to 1/4 of what it was before is pretty much equivalent of reducing the density of air by 1/4 (which as I've mentioned before allows a doubling of speed).

 

Doing a preliminary search as well you can easily find
https://iopscience.iop.org/article/10.1088/1757-899X/184/1/012015/pdf

 

 

Notice the drag co-efficient between the baseline and M3 drops by half...but also notice the diminishing returns.

 

Modern highspeed trains already have adopted an even more streamlined model of M3 as well; so it's talking about making it even more efficient.

 

51 minutes ago, Uttamattamakin said:

Anything that is legally a train has to obey the laws made for trains.   The USA has regulations that tell you how high the steps have to be, how steep a wheel chair ramp can be etc etc.    During testing it is enough to shoehorn test subjects in.  When actually making a real thing real people will have to use it will have to at least be something kin to a subway tunnel within a city, or a full on Amtrak single decker if intra city in the USA. 

Again, there are already transits in place that have the vehicles which would be able to fit into a 3.3m tunnel.  Also laws can be overall flexible if the introduction of a new form of transit that is put in place.

 

53 minutes ago, Uttamattamakin said:

technology used to make trains more aerodynamic was used. 

You are making assumptions that you can make it more aerodynamic.  High-speed rail and bullet trains already have had innovations in aerodynamics, but it's the law of diminishing returns.  Just like pulling a vacuum is a law of diminishing returns.  It's easy enough to pull 1/2 atm but much harder to pull 1% vacuum.  (See above why aerodynamics is not and cannot be the solution).

 

On top of that, again you have the skin force effect which will also be effected by air density (which you can't design aerodynamics to really minimize that)

[leadeater]

8 hours ago, Uttamattamakin said:

Not just time, without air the only way for the tracks to cool down would be by radiation.  No air, no cooling. 

You would just have the tracks thermally connected to the outside, even the tube itself being metal is a heat sink. I don't know what would be enough but more just saying you'd have to actually design for it since you aren't having a train going over a specific track section once every hour or longer with the heat also able to spread down the track. Since they are talking about seconds/minutes between hyperloop trains dissipation along the track is not possible since there is no down time and space between friction/heat generation.

 

Water cooling the tracks also wouldn't be difficult either and relative cost wise not that expensive, everything just adds to the complexity of design.

 

I'd question the point since hyperloop trains aren't going to be that heavy nor need to be levitated that far off the tube surface so the energy required to do this is well below that of a high speed train, also lower per/kg as well. How much lower energy/kg I don't know but it will be "less". Which also means rail tracks might not actually be cheaper but I have no way to gauge that at all.

[leadeater]

8 hours ago, Uttamattamakin said:

Right now the land speed record is over 1200 km/hr.  If a train can be designed to do even 50% + of that through aerodynamic design, then why have hyperloop at all?  There is a good chance that while a hyperloop is being built if it is ever tried for real that is what will happen.    The fastest maglev in the world is already 600 km/hr as it is. 

ThurstSSC has ~101,379hp while hyperloop POC done so far have around 3,000hp. Little different amounts of power don't you think 

[CarlBar]

1 hour ago, leadeater said:

ThurstSSC has ~101,379hp while hyperloop POC done so far have around 3,000hp. Little different amounts of power don't you think 

 

Half the speed means a quarter the drag at normal atmospheric density, at a tube running a pressure equivalent to 60,000ft half speed would have 1/56th the total drag, thats the equivalent of needing around 1800HP. Honestly though for an electrically driven system the HP requirements of a given sped aren't a huge concern, it's the cooling aspects as noted that are a major pain in terms of carriage design, that and safety.

 

8 hours ago, HenrySalayne said:

People don't seem to follow how high-speed trains are mostly capped around the 300 km/h region. Even the speed record holding TGV with more than 500 km/h reaches the 300-km/h-mark rarely in everyday use

 

By it's nature a hyperloop is going to need reinforced and very levelled tracks. Thats actually how i expect it to come into use if it ever happens. We keep improving on existing high speed rail with the ever increasing track strength and track smoothness requirements to the point we start building it either elevated or below ground to let us control the smoothness to extreme amounts and eventually the extra challanges of pumping it down are just a minor addition to an allready complex program so we start building it in, (probably at a fairly high value, say 0.7-0.8 atmospheres, a value for which you don't need to seal the carriage as it's perfectly breathable), and we just scale it bit by bit until were running low pressures and super speeds.

[Kisai]

1 hour ago, leadeater said:

You would just have the tracks thermally connected to the outside, even the tube itself being metal is a heat sink.

I think the bigger problem there would be the metal fatigue. Metal expands when heated, and shrinks when cold, and if it's used as a heatsink, that would just accelerate the metal fatigue.

 

The Skytrain here, which operates using LIM's, have intrusion pressure plates at the stations which appear to double as heatsinks on the LIM rail (if even only anecdotally,) since during rain/cold weather, you can see steam rise off them where tracks are exposed, which means they're at least hot enough from braking to do that. But that may also be the reverse, the physical brakes only being used during wet weather, in addition to regenerative braking. Either way there is more surface area.

 

The stations without the plates use a different intrusion system and don't seem to generate very much steam when they are wet since the stations are more enclosed. The Canada Line stations (which are conventional motors) don't do this at all since there's no LIM strip.

 

At any rate, I think most of the arguments about if the hyperloop could/would work come right back to needing materials that are immune to thermal expansion and have tensile strength to support cycling air pressure as many times as needed.

 

Extended range Airplanes have a life span much longer than short-haul aircraft. 

 

At any rate, I do feel the thread has kinda turned into a discussion of arm-chair discussion of the viability of the hyperloop.

https://www.tesla.com/sites/default/files/blog_images/hyperloop-alpha.pdf

Quote

Constraining the Problem

 

The Hyperloop (or something similar) is, in my opinion, the right solution for the specific case of high traffic city pairs that are less than about 1500 km or 900 miles apart. Around that inflection point, I suspect that supersonic air travel ends up being faster and cheaper. With a high enough altitude and the right geometry, the sonic boom noise on the ground would be no louder than current airliners, so that isn’t a showstopper. Also, a quiet supersonic plane immediately solves every long distance city pair without the need for a vast new worldwide infrastructure.

The first mistake was mentioning supersonic aircraft. 

https://ntrs.nasa.gov/citations/20205009400

 

Quote

Supersonic aircraft would be bad for the planet at above Mach 1.5 it appears.

 

The problem is that Super sonic aircraft are not economically viable unless they are fast, the Concorde was Mach 2, and new aircraft are proposed at Mach 1.7.

 

So back to the Hyperloop proposal:

Quote

So, no maglev. These are LIM's (like the Skytrain) but on vehicle pods that are about the same size as the MK I skytrain with half the capacity:

Quote

 

So at just under Mach 1, at 100 Pascals at 20 degrees C.

Quote

So it's not maglev, it's just being lifted by "air bearings."

Quote

So theoretically each "hyperloop" capsule costs 54 million dollars.

 

Let's compare that to trains, and airplanes:

http://www.axonaviation.com/commercial-aircraft/aircraft-data/aircraft-pricing

A 737-900ER is about $112Million, or slightly more than double the "hyperloop pod", and the plane can carry 220 passengers, vs Hyperloop pods 28.

 

Before the 2017 accident, the new Talgo VIII trains that Amtrak Cascades had cost $38m, 13 cars long, and seats 285 people.

http://web.talgoamerica.com/about-us-menu/news/49-odot-purchases-talgo-passenger-trains

 

So we're right back at to the logical costs. So if a tube had to be built, and the pods cost more than entire high speed trainsets (and for the sake of argument, yes the cascades are capable of 125MPH (200kph) to 250kph but are only run at 79MPH (127kph.)) Which is still faster than the highway speed on I5.

 

But of course we're talking about California HSR, not Seattle.

 

 

Quote

So note the hyperloop doesn't run at 760mph except during the long "I5" coasting sections. The rest of the time it's 300mph.

 

Compare to the California HSR:

https://hsr.ca.gov/communications-outreach/info-center/get-the-facts/

Quote

So the top speed of the HSR is well below the "bottom speed" of the hyperloop, but is also about as far away as the Talgo trainset Seattle uses that is capable of 250kph (155mph), but the "slowest" speed, is also well above the "fastest" speed Amtrack Cascades seattle-to-portland service is (110mph vs 79mph)

 

Now, I don't think anyone is actually proposing the HSR or hyperloop to actually plow straight into a city center at top speed and then stop on a dime. The G forces would be quite... a mess. That said, under any metric used, the Hyperloop looks good on paper until you look at the costs, and pretty much come to the conclusion that it wouldn't be economically viable to build if the pods alone cost more than a train with 10x the capacity. Even if the train is 3.5 times slower, it's still capable of delivering more people... and in a more comfortable mode.

 

You build the track once, but you have to replace the trains every 30 years. When the pods cost as much as a plane or a complete train it looks extremely dubious. You need to move a lot of people quickly, and it's cheaper to send a train or airplane on schedule even if it's half empty than than it is to wait until it's full because of the cost of energy/fuel to keep it idling. You can right-size your schedules, and thus people can plan their trips around it and get more customers.

 

Anyway, personally, I still feel the hyperloop was pretty stupid, and while the paper looks researched, it makes some pretty bold asks on unproven technology. Meanwhile we have proven technology in both Japan and Europe, all that was needed in California was some will to build it. 

 

Also keep in mind that if the HSR is capable of 220MPH, that puts it above most operating Shinkansen routes (which top out at 260kph (160mph)), we have "high speed" capable trains in the US, we just don't have high speed routes/tracks.

 

 

[Uttamattamakin]

7 hours ago, wanderingfool2 said:

Actually it does.  I never said they were linear; but we are comparing variables which means yes there is a relationship between density and the aerodynamics and the square gets cancelled out

 

You didn't say it but the way you were and are discussing it is using a linear approximation to a non-linear effect.   The basic equation to start from is here. 

 

 

The assumption in your thinking is that the drag force is the one on top.  When for this it needs to be the one on the bottom.  When you analyze this using the energy-momentum formulation, aka Hamiltonian mechanics you see that this velocity certainly does not drop out.   The faster you go the stronger drag becomes and the more energy you loose to it... until at the highest velocities you get the heat of re-entry from space.  We aren't going anywhere near that fast but computer models take account of it.  

 

The research you found is good but it does not use a linear model This graph does not show the alleged diminishing returns you speak of. 



Note in the graph from your own citation the sharp nosed train encounters less than half the drag just by being sharp nosed. The faster the train is going the more of a difference it makes.  Also note the lines are curved, hence it is a non-linear effect.  In a linear model the lines would be straight.

Since you were nice about this I am very grateful. 

 

  NOW since drag is non linear this means that a small reduction in pressure to the equivalent of 10,000 feet... or better still 8000 ft (An allowed cabin pressure inside the Boeing Business Jet http://www.b737.org.uk/pressurisation.htm#:~:text=The pressurisation system of all series of 737,of 8.99psid above 37%2C000ft) to increase passenger comfort.)  We could run a "Hyperloop" that won't have the worry of implosion to the same degree as a more extreme vacuum and be able to breath inside without having to have a pressurized cabin inside an evacuated tunnel.  

What I am saying is something @leadeater commented towards a few pages ago.  So credit him with making me think this over.  IF the pressure is just a BIT lower AND the train a BIT more aerodynamic we can get 80% or 90% of what we'd get out of a hyperloop without needing to do anything quite so radical and potentially dangerous.  Getting a trip time comparable to a high speed turboprop out of an intracity mass transit system would be pretty good.

 

Not discounting what you said and did.  None of that is necessary.  We don't have to re-invent high speed rail to apply some fo what has been learned from Hyperloop projects to it in a modified and more practical form. 

2 hours ago, leadeater said:

ThurstSSC has ~101,379hp while hyperloop POC done so far have around 3,000hp. Little different amounts of power don't you think 

True and what you said about the tracks ... I guess that depends if we are abandoning having a strong vacuum chamber for this to run in maybe we don't need a steel tube ... which means that having a giant heat spreader is lost.  So maybe we want a thinner steel tube that could be cooled by cooling the lower pressure air inside it a bit and keeping it moving. 

I am thinking the problem with this idea was and is not having a mag lev in a tube it is the demand that it be at an air pressure so low that it becomes a problem in and of  itself. 

You're a sys admin right?  It's like making a custom water cooled server for the Lulz when air cooled will do. 


 

 

11 minutes ago, Kisai said:

I think the bigger problem there would be the metal fatigue. Metal expands when heated, and shrinks when cold, and if it's used as a heatsink, that would just accelerate the metal fatigue.

This is a good fundamental point that I did not think of.  Even if this is not one big piece, but ... acts like one since everything would be welded together, expansion and contraction due to heating and cooling would over time cause cracks.  

IF this is done at high vacuum then a tiny crack means implosion and sudden death to many.   If this is done at a low vaccum, similar to the pressure inside the cabin of a jet when cruising, then this will be much less of a problem.   A train derailing with injuries VS an un survivable catastrophe. 

 

11 minutes ago, Kisai said:

At any rate, I think most of the arguments about if the hyperloop could/would work come right back to needing materials that are immune to thermal expansion and have tensile strength to support cycling air pressure as many times as needed.

So, we are back to needing Adamantium and Vibranium.    

OR being brave and visionary enough to see that Carbon Fiber is perfect for holding up under extremes of temperature and pressure. 

 

(I wonder how much Carbon Fiber was mentioned in various Hyperloop promotional materials.  There was a time there when EVERYTHING was being made with carbon fiber when it was meant to be "space age" and advanced.   Like everyone thought they were Burt Rutan of Scaled Composites designing an aircraft). 

 

11 minutes ago, Kisai said:

So theoretically each "hyperloop" capsule costs 54 million dollars.

So less than the DOD spends on a toilet at some top secret base somewhere I'll bet. 

 

11 minutes ago, Kisai said:

Now, I don't think anyone is actually proposing the HSR or hyperloop to actually plow straight into a city center at top speed and then stop on a dime. The G forces would be quite... a mess. That said, under any metric used, the Hyperloop looks good on paper until you look at the costs, and pretty much come to the conclusion that it wouldn't be economically viable to build if the pods alone cost more than a train with 10x the capacity. Even if the train is 3.5 times slower, it's still capable of delivering more people... and in a more comfortable mode.

... all that and as others have said to keep cost down corners would be cut  which would make it less safe.    I predict if someone does build a hyperloop, in the strong sense of the word.  100 pascal vaccum, pods just small enough to get into, all of that... it may work well for a while then it will suddenly catastrophically fail.  Basically it will be like the Hindenburg. 

Edited January 24 by Uttamattamakin
Lightening the mood.

[wanderingfool2]

Can you seriously stop posting those annoying NSFW gif's that have nothing to do with the topic.  I don't open this thread with anyone around because of images like that.

 

1 hour ago, Uttamattamakin said:

The assumption in your thinking is that the drag force is the one on top.  When for this it needs to be the one on the bottom.  When you analyze this using the energy-momentum formulation, aka Hamiltonian mechanics you see that this velocity certainly does not drop out.   The faster you go the stronger drag becomes and the more energy you loose to it... until at the highest velocities you get the heat of re-entry from space.  We aren't going anywhere near that fast but computer models take account of it.  

What is frustrating about your comments is you intentionally ignore the basic level common sense.  If you look at the formula that I stated IN MY POST you wouldn't have to make a faulty assumption because *gasps*...I am using the bottom one; you just are failing to comprehend that the point I was talking about doesn't refer to the velocity variable

 

AGAIN it's basic level arithmetic;  I'm thinking you are lacking the understanding that there is a drag coefficient vs drag force

 

You are the one that was talking about the fact that you could achieve the same effects by making current trains more aerodynamic.

 

I'm not arguing about velocity contributing a square to the equation.  I'm arguing that saying to make things "aerodynamic" has a linear relationship when compared to the same effects of reducing density

 

Let me spell it out for you:

We are talking about manipulating the aerodynamics of the vehicle (i.e. drag coefficient, represented as the variable C in your image)

We are also talking about manipulating the density (i.e. p in your image)

 

 

i.e. If you are travelling at 100 km/h, and you reduce the drag co-efficient by half (i.e. make it more aerodynamic), the drag force reduces by half...which if you reduce density by half you have the same effect

 

The only variable that doesn't have a linear effect on the result is velocity; which again, if you had any basic understanding of the formulas you would realize why I said a reduction from 1 atm to 0.25 atm meant you could double your velocity.

 

So again, let me be VERY VERY clear.  Reducing aerodynamics has a linear effect and in fact the same linear effect as reducing density.

 

1 hour ago, Uttamattamakin said:

Note in the graph from your own citation the sharp nosed train encounters less than half the drag just by being sharp nosed. The faster the train is going the more of a difference it makes.  Also note the lines are curved, hence it is a non-linear effect.  In a linear model the lines would be straight.

Since you were nice about this I am very grateful. 

You are either being dense or you seriously do argue in bad faith.

 

You showed a graph comparing the drag to velocity; which if you took 2 seconds to look at the formulas I've already stated doesn't matter because I have never suggested that changing velocity was linear.  I said that the effect changing the co-efficient of drag (not drag force) is linear...which if you look at the graph, the ratio between the drag compared to drag co-efficient at velocity 20 vs velocity 40 is the same.

 

i.e. if you have D(vel, drag co-efficient) as your input  D(x, 0.5)/D(x, 0.25) = 0.5 for all values of x

 

1 hour ago, Uttamattamakin said:

NOW since drag is non linear this means that a small reduction in pressure

No that's wrong, the drag is non linear in association to change in velocity; but you are manipulating the pressure variable which has a linear effect

Look at a basic level equation y = (Ax)² + Bx + C

A is said to contribute non-linearly

B contributes to a linear effect

and

C has a constant effect/offset

 

Your suggestion of making it aerodynamic is manipulating a variable that has a linear effect.  It's why you have to reduce the drag co-efficient (not drag force) by 4x in order to achieve doubling the velocity with the same force.

 

1 hour ago, Uttamattamakin said:

Not discounting what you said and did.  None of that is necessary.  We don't have to re-invent high speed rail to apply some fo what has been learned from Hyperloop projects to it in a modified and more practical form. 

You were the one saying that we could just achieve better aerodynamics, which is not practical/limited...given that bullet trains already have a low drag co-efficient.  How do you suggest making high-speed trains or bullet trains better?  If you claim aerodynamics like you are, you need to have the basic understanding that even if you assume it's compared to a 0.5atm hyperloop you are talking about needing to reduce the drag co-efficient by half to achieve the same effect (which see below in regards to diminishing returns).

 

1 hour ago, Uttamattamakin said:

The research you found is good but it does not use a linear model This graph does not show the alleged diminishing returns you speak of. 

Do you seriously not get what I mean by diminishing returns?

 

Let me break it down like this,

You have the boxy baseline, which has ~0.5 drag co-efficient

You have streamlined M3, which has ~0.2 drag co-efficient

Current high-speed rails sits actually beyond the M3 design (i.e. modern high speed/bullet trains have a lower number than the M3)..from what I can tell the current ones are ~ 0.12+0.0075x
https://www.jstage.jst.go.jp/article/jsme1958/8/31/8_31_390/_article

 

Now what do you propose to beat the ~0.12, an airfoil as per NASA can reduce drag down to 0.045...but achieving that would be hard, and only would amount to the equivalent of reducing the atm down to 0.34 atm.

 

That's what I mean by diminishing returns, it gets harder and harder to achieve a given result the more you progress in the design.  It's easy to go from a boxy frame to something like M3...but it takes a lot more work to get it from M3 to the current, and even tougher if not impossible to get it to the most idea shape of 0.045

 

Just like reducing the ATM from 1 to 0.5 ATM is pretty trivial compared to 0.5 to 0.25ATM and more so going from 0.25 to 0.125ATM.

[HenrySalayne]

2 hours ago, CarlBar said:

By it's nature a hyperloop is going to need reinforced and very levelled tracks. Thats actually how i expect it to come into use if it ever happens. We keep improving on existing high speed rail with the ever increasing track strength and track smoothness requirements to the point we start building it either elevated or below ground to let us control the smoothness to extreme amounts and eventually the extra challanges of pumping it down are just a minor addition to an allready complex program so we start building it in, (probably at a fairly high value, say 0.7-0.8 atmospheres, a value for which you don't need to seal the carriage as it's perfectly breathable), and we just scale it bit by bit until were running low pressures and super speeds.

I don't follow your point.

Allowing high speeds on tracks is not about smoothness but dynamic loads. Not only is there an air pressure wave from the train but also a pressure wave moving through the foundation. Just to name a few things that might need to be done:

• reinforcement of the foundation and bridges
• increased spacing between the tracks, so pressure waves won't endanger passing trains on neighbouring tracks
• reinforcement / addition of walls along the track for noise suppression and sheer wind reduction
• reinforcement and tensioning of the overhead wires and their towers
• rebuilding / reinforcement of tunnels to account for the air pressure wave

I think it's rather obvious that this massively increases the cost of the track. In most cases it would probably be more sensible to built entirely new routes than to retrofit existing ones.

Hyperloop doesn't have these issues. The vacuum tube is a rather heavy and expensive piece but it's a static load. Aerodynamics, noise and wind are non-issues. And the lower moving mass (instead of 50 axles with 10 t each, the entire vehicle might be around 10 t) substantially reduces dynamic loads.

 

On a side note, high speed trains already have pressure cabines (not pressurised!) so you won't pop your ear-drums every time you pass another train or a tunnel.

[leadeater]

6 hours ago, Uttamattamakin said:

(I wonder how much Carbon Fiber was mentioned in various Hyperloop promotional materials.  There was a time there when EVERYTHING was being made with carbon fiber when it was meant to be "space age" and advanced.   Like everyone thought they were Burt Rutan of Scaled Composites designing an aircraft). 

Carbon Fibre was literally never considered viable for space usage, wonder material sure, space age attributed no. It's the same reason only one person/company ever tried to use carbon fibre the way they did and died and took the lives of others while doing it.

 

Actual engineers don't listen to Nat Geographic etc and treat materials as wonderous things perfect for everything, that is not a thing. Only those that ignore common sense do, they die while doing it.

 

As you may have noticed Virgin used Metal not Carbon Fibre for the tubes, they had common sense, it was never even considered.

 

6 hours ago, Uttamattamakin said:

True and what you said about the tracks ... I guess that depends if we are abandoning having a strong vacuum chamber for this to run in maybe we don't need a steel tube

Why abandon a strong vacuum? What is a strong vacuum?

 

If ThrustSSC were operating in 0.5atm how much thrust(hp) would it have needed? How much at 0.25atm?

 

Obviously low air density is a massive benefit and you can't do that out in open air aka earth atmosphere without flight so trains must do it in a contained environment.

 

High speed trains that can go above 200mph require greater than 10,000hp. Which then my next question would be how much do you think they would need to go 500mph?

 

At some point it is actually more viable, more cost effective and more reliable to just put the train in low pressure than to throw the equivalent amounts of energy at the situation as a contained large explosive bomb continuously.

 

If you look at every factor that contributes towards what is required to move, velocity, and you aim to minimize every single one of them the most cost effective way then you'll have the best chance at achieving the lowest total cost of ownership than to focus on only one or a select few and have to do something revolutionary i.e. ThrustSSC.

 

In principle Hyperloop is exactly this, looking to optimize every factor to achieve the peak possible at the lowest practical effort for each factor. There are just a lot of things we don't do that is needed in a hyperloop that make it expensive or not fully understood. Do consider that if you never do it then you'll never understand it and you'll also never create the knowledge, tooling and supply chain to make it cheaper and thus commercially viable.

 

Space flight was always said to not be commercially viable and nation state only, now we have multiple different companies in different countries all achieving what was said to not be "commercially viable". Opinions of the day can be correct, that doesn't mean they stay that way in to the future forever. Those that are able to see those future changes and further that for their own gains are the ones that become billionaires or remembered as revolutionaries that brought about real social change i.e. personal vehicles for the masses (freedom of movement).

 

One of the easiest things in life is to say no, the easy path is not always the best path.

[CarlBar]

34 minutes ago, leadeater said:

Carbon Fibre was literally never considered viable for space usage, wonder material sure, space age attributed no. It's the same reason only one person/company ever tried to use carbon fibre the way they did and died and took the lives of others while doing it.

 

US navy built deep diving underwater RoV's with it. In fact the designs are so similar that it looks a lot like they scaled up the US navy RoV design. The issue seems to be more to do with how they manufactured the hull and the safety margins they assigned.

[leadeater]

22 minutes ago, CarlBar said:

 

US navy built deep diving underwater RoV's with it. In fact the designs are so similar that it looks a lot like they scaled up the US navy RoV design. The issue seems to be more to do with how they manufactured the hull and the safety margins they assigned.

Potentially also one of those scale effect situations? Good when small, bad when bigger? 

[CarlBar]

4 hours ago, leadeater said:

Potentially also one of those scale effect situations? Good when small, bad when bigger? 

 

Probably not,whilst it's not an ideal material for compression loads you can use it there with the right method of construction and a lot of very careful behind the scenes design and testing work. Oceangate where just really slapdash about the whole thing, and when your pushing a material into an area thats not well understood thats not a good idea.

[Uttamattamakin]

8 hours ago, leadeater said:

Carbon Fibre was literally never considered viable for space usage, wonder material sure, space age attributed no. It's the same reason only one person/company ever tried to use carbon fibre the way they did and died and took the lives of others while doing it.

I felt lazy so I asked Microsoft Co Pilot.  I'd add to this Space Ship 1 and Space Ship2 designed by Scaled Composites. 

8 hours ago, leadeater said:

Actual engineers don't listen to Nat Geographic etc and treat materials as wonderous things perfect for everything, that is not a thing. Only those that ignore common sense do, they die while doing it.

 

As you may have noticed Virgin used Metal not Carbon Fibre for the tubes, they had common sense, it was never even considered.

See above 

 

8 hours ago, leadeater said:

Why abandon a strong vacuum? What is a strong vacuum?

Strong enough to crush a metal tube if the tube isn't made right.  

For our purposes a weak vacuum is anything less than 1 ATM of pressure and up to say the air pressure at 10,000 feet.  Air planes that are not pressurized can fly for hours at that height with no hypoxia effecting the passengers or crew without supplemental oxygen. 

8 hours ago, leadeater said:

 

If ThrustSSC were operating in 0.5atm how much thrust(hp) would it have needed? How much at 0.25atm?

If we make the simplest non-linear model and approximate the drag-pressure dependence as quadratic.  

For a constant velocity

Drag ~ pressure^2

 

So, Doubling the pressure would be 4 times the drag while 1/2in'g the pressure would be 1/4 the drag.  The thrust would be equal in magnitude but opposite in direction to the drag.   Here is a simple plot screen shot from my own desktop. 

 

So we see from here that at 0.5 Atm for a constant velocity of mach1  the drag force is about 25% of what it would be at 1 ATM at sea level.  So, 2500 hp.   
For a typical high speed train going about 0.25 of the speed of sound the green line on that chart applies.  At 1/2 of at atm a train going  around 300 km/h would encounter 0.066, or 6% of the drag force at 1 ATM.   (When discussing how much of a mag lev would be needed in such a system this needs to be taken account of). 

What I propose would not be 1/2 of an atmosphere but instead to operate at the pressure of 10,00 feet.  Which is 0.7 atm.  People who do not have breathing problems can breathe for hours at this level of pressure.   This is the altitude a jet will dive to if it experiences decompression at cruising altitude. 

 

At 0.7 ATM pressure a train maintaining 1/2 the speed of sound would need only about 30% of the thrust it would need at 1 atmosphere. 

 

8 hours ago, leadeater said:

At some point it is actually more viable, more cost effective and more reliable to just put the train in low pressure than to throw the equivalent amounts of energy at the situation as a contained large explosive bomb continuously.

Agreed see above.  Lower pressure but not so low that it causes problems like catastrophic implosion. 

 

8 hours ago, leadeater said:

In principle Hyperloop is exactly this, looking to optimize every factor to achieve the peak possible at the lowest practical effort for each factor. There are just a lot of things we don't do that is needed in a hyperloop that make it expensive or not fully understood. Do consider that if you never do it then you'll never understand it and you'll also never create the knowledge, tooling and supply chain to make it cheaper and thus commercially viable.

What what cost do you want to go a bit faster? 

 

8 hours ago, leadeater said:

Space flight was always said to not be commercially viable and nation state only, now we have multiple different companies in different countries all achieving what was said to not be "commercially viable".

Until now the issue wasn't could a private company make money but could anyone but the government afford the bill. 

The truth is space has BOTH Always been a private enterprise AND always will be government funded via contracts.   All sorts of private entities were involved with the Space Shuttle.  Just now we have Space X putting their name right on it and using it to service contracts that are also not government. 

 

Before I go on one thing has to be said.  

 

You're telling me the person who has actually dedicated their professional life to space exploration all of that.  I know that. 

 

I know you mean well but in response to your sermon I need to remind you I am in the choir.  Though you are preaching I probably know the scriptures of nature, the laws of nature better. 

 

Do you all see (Don't you remove this image lots of people here have tried to talk down to or about me.  NOw that this is serious lets be serious.  One of the people on this thread knows all of these factors and can work them out in their head.  I can be wrong but I admit it, correct it, and have NEVER INSULTED ANYONE HERE. Yet I get preached to and insulted all the time

 

@leadeater I am not distinctly speaking about you on this but just something that has  been building up for a while.   You have been civil and wonderful and a real role model in this thread.  

So I give you a curtsy 

 

A general thing I need to get off my chest. 

 

I am a bit lost I am told the news section is super serious by someone else.  Then I should be able to post my CV and credentials and all the dilettantes should be silent.  Since what I say is based on knowledge too deep to lay all of it down here.  I should not have to justify a thing. There are calculations in my head behind every word that would take a semester course to explain.

 

They are how I knew that LK99 was 99.9% BS.  Remember how soooo many here were telling me I didn't or couldn't know about it.  Accused me of making up that I know what I'm talking about.  Did any one of those people have the integrity to say you know what... we were wrong.  No instead they try to act like specialists in this area of knowledge couldn't tell how unlikely it was to be right after viewing the data. 

 

 I don't think that this is all so serious, so I don't think that way.  I think that some degree of banter and fun are part of this.   Anyone can know things and anyone can make a good point.  Just don't forget at least one of us has dedicated their life to science.  Not just taken a course in it or something.  If this is serious then Professor Uttamattamakin is in class.  If not then I am here to have fun.  

 

Now I don't want to hear anyone try to come back at this about things they looked up on the internet (which I already knew and knew why they don't apply or don't apply the way they think they do.  If you want to talk down to me show me your PhD.   If some of you who I won't name did know what you are doing then you'd know that you are ... not even wrong.    Not right but so far off that youd need to learn more in order to be wrong. 

 

Now I  have a physics textbook to help edit.   I can relax by solving some equations.  Jeeze I try to relax and kick around some ideas and this is what I get.  Now I'm off wearing a suit. 

 

I feel my boy Thunderf00t and why he started his video with a clip of (was that from the Highlander) sharpening his sword to take no prisoners.)

Darn boring textbook... So I looked up carbon fiber and hyperloop.  One of those outfits really did develop a "wonder matterial" with Carbon fiber and called it Vibrainium. LOL. 

https://medium.com/@matmatch/which-materials-are-making-the-hyperloop-possible-393c96189602#:~:text=In the development of its Hyperloop pods%2C HTT,skin type material to protect the Hyperloop pods.

 

Quote

In the development of its Hyperloop pods, HTT has developed a new type of carbon fibre composite that is eight times stronger than aluminium and ten times stronger than steel alternatives. The material, named vibranium (inspired by Marvel’s fictional metal), has been designed to be a skin type material to protect the Hyperloop pods.

I can just hear Thunderf00ts voice in my head reading that part. LMBO

[wanderingfool2]

7 hours ago, leadeater said:

Carbon Fibre was literally never considered viable for space usage, wonder material sure, space age attributed no. It's the same reason only one person/company ever tried to use carbon fibre the way they did and died and took the lives of others while doing it.

 

Actual engineers don't listen to Nat Geographic etc and treat materials as wonderous things perfect for everything, that is not a thing. Only those that ignore common sense do, they die while doing it.

 

As you may have noticed Virgin used Metal not Carbon Fibre for the tubes, they had common sense, it was never even considered.

I do agree in that it probably was never considered viable; although they might have still tried running the numbers to see if it might be viable...then again carbon fiber's drawback would be changing pressure the material just doesn't hold up overtime.

 

A note about space usage though, firefly Alpha actually uses a carbon fibre composite for their framework on their rocket (but those rockets are one time use things).

I think the Electron rocket also is carbon fibre.  SpaceX actually considered carbon fibre for their starship, although they eventually switched to steel after realizing steel had better strength across all temperature ranges that it would experience.

 

6 minutes ago, Uttamattamakin said:

I can be wrong but I admit it, correct it, and have NEVER INSULTED ANYONE HERE. Yet I get preached to and insulted all the time

Your ideas you present are being attacked; and your overall insistence on relying on those facts...and yes generally your ideas are attacked because you are attributing the ideas as facts because you overall argue in bad faith.

 

It's like the whole insistence on using 10m as a round number, when clearly the number should be 3.3m.  The claim that people like ThunderF00t knows what he's talking about and has degrees in it when in fact his degree is in Chemistry.

 

10 minutes ago, Uttamattamakin said:

If we make the simplest non-linear model and approximate the drag-pressure dependence as quadratic.  

For a constant velocity

Drag ~ pressure^2

Show an actual formula then that shows Drag ~ pressure squared...because as I've pointed out already twice the formula CLEARLY shows pressure (density) in the formula has a LINEAR effect on drag.

 

Here's the formula that I've been using, that you claim I should also be using (thinking I used the wrong formula).

dragforce = -1/2 * C * p * A * v2

C = drag co-efficient

p = density

A = cross-section area

v = velocity.

 

As you stated constant velocity, so v is no longer a variable in the equation but a fixed number.  A and C will also be fixed number in this case

v² since v is constant you can express v²  as some constant as well (so you can combine -1/2, A, C and v² into a single constant)

 

It's basic level math at this point, dragforce = B * p

Where B is some fixed constant that is determined by B = -1/2 * A * C * v2.  The key is B should not be changing..so with a relatively constant B the pressure can be said to have a linear effect.

 

Now if you really wanted to go into detail, you could talk about how the drag co-efficient also is a function of density, but from what I've seen it contributes to a smaller effect; as can be seen again in the boxy version vs M3 version, the ratios stay the same (they don't grow exponentially apart when you factor out the velocity)

 

38 minutes ago, Uttamattamakin said:

I am a bit lost I am told the news section is super serious by someone else.  Then I should be able to post my CV and credentials and all the dilettantes should be silent.  Since what I say is based on knowledge too deep to lay all of it down here.  I should not have to justify a thing. There are calculations in my head behind every word that would take a semester course to explain. They are how I knew that LK99 was 99.9% BS. 

 

 I don't think that this is all so serious, so I don't think that way.  I think that some degree of banter and fun are part of this.   Anyone can know things and anyone can make a good point.  Just don't forget at least one of us has dedicated their life to science.  Not just taken a course in it or something.  If this is serious then Professor Uttamattamakin is in class.  If not then I am here to have fun.  

The issue is you are making outlandish assumptions, like a 10m wide tunnel

 

I don't care if you have a PhD in mathematics/physics etc...if you make an outlandish claim based on assumptions that are faulty then your numbers come out wrong.  It's the same argument being made over on the SpaceX stuff, you make faulty statements based on terrible assumptions and claim to know better when you get called out on it.

 

The fact is:

No the tunnel won't be 10m wide, and won't be 10 cm thick

No you cannot just simply improve the aerodynamics of modern trains

No the density of air doesn't contribute to a square of density.

 

Quadruple the density of air and you now are only afford half the speed to maintain the same drag.

 

Again, PhD's can mean nothing because again I know computer science PhD who cannot properly operate a standard computer.  A PhD does not prevent you from making an ignorant or blatantly wrong statement...it is concerning though that you seem to resort to the whole I have a PhD when your arguments get picked apart.

 

I dare you to go to one of your colleagues, and show them the drag formula from NASA or the edu one, and then tell them that changing p by half will result in drag being 1/4 the size.

 

 

Anyways, one of the things I wanted to point out.

 

LIGO

https://www.ligo.caltech.edu/page/vacuum

1.2m tube - drum roll please, thickness of 3mm (at an ultra high vacuum).  Even using the rule of thumb before it would state you need 1.2cm.  So clearly at 2m, using 2cm would be overkill.

 

[HenrySalayne]

39 minutes ago, wanderingfool2 said:

LIGO

https://www.ligo.caltech.edu/page/vacuum

1.2m tube - drum roll please, thickness of 3mm (at an ultra high vacuum).  Even using the rule of thumb before it would state you need 1.2cm.  So clearly at 2m, using 2cm would be overkill.

The tube is clearly not infinitely long and they added frames / stiffeners to prevent it from buckling and collapsing! Unfair!

Not to mention they used it for 20 years and clearly didn't use stainless steel (since there is a lot of rust). Fascinating, but also against the rules...

 

1 hour ago, Uttamattamakin said:

[...]

 If you want to talk down to me show me your PhD. 

I think that shows a mentality I can absolutely not agree with...

[Uttamattamakin]

58 minutes ago, HenrySalayne said:

The tube is clearly not infinitely long and they added frames / stiffeners to prevent it from buckling and collapsing! Unfair!

Not to mention they used it for 20 years and clearly didn't use stainless steel (since there is a lot of rust). Fascinating, but also against the rules...

 

I think that shows a mentality I can absolutely not agree with...

I don't either which is why I never decided to post my CV until now.  I also said that ANYONE can make a good point and ANYONE can be wrong.  I've admitted if I was wrong about something many times.   

 

I also never denigrated anyone when explaining to them WHY they are wrong.  

 

Can you and @wanderingfool2 say the same regarding how you write to me much of the time?.  Honestly? 

 

In speaking of which Wandering fool.  Do you want a full course on Fluid dynamics?   OR do you want a formula that is good enough for a quick estimate?    A course taught by me cost the state of IL 1242 USD / Contact hour.  For free you get a simple estimation based on what I know of things. 

 

Here's a short explanation for where you are going wrong with the application of that source to this.  I know what LIGO is doing very well.  I am working on a Space Based successor to it called LISA.   Building a relatively small tube down which to send light is one thing.  Building a tube real human beings who come in all shapes and sizes and some of whom are like my father, blind, with COPD and sometimes need to be moved in a Wheel chair.  

Any system that can only be ridden by svelte toned young people who are able to climb over and around and all of that is not worth the money.  The tunnel size comes from scaling up the Hyperloop 1 tunnel to carry a passenger pot that would meet the same standards as applied to a passenger train in the United States of America. 

IT's also odd that you would object to that formula.  Since it shows that as you remove pressure from the tube you get a HUGE return in having less drag.  Thereby needing less thrust, and being able to go faster while using less energy.  If anything, my formula demonstrates in simple terms WHY hyperloop is attractive.  Lowering the pressure in the tube even a little bit makes it much more efficient. f

 

We can talk about different pressures, materials, thermal considerations and on and on.  We can even collectively build a computer model if you like.  Just remember KEEP IT FUN.  KEEP IT LIGHT.  Don't be so serious.  I'd not be surprised if this message board could work out an actual practical Hyperloop or hyperloop like (Hyperloop lite???) system better than a billion dollar company.   

Said with a smile. 
 

[wanderingfool2]

46 minutes ago, Uttamattamakin said:

Here's a short explanation for where you are going wrong with the application of that source to this.  I know what LIGO is doing very well.  I am working on a Space Based successor to it called LISA.   Building a relatively small tube down which to send light is one thing.  Building a tube real human beings who come in all shapes and sizes and some of whom are like my father, blind, with COPD and sometimes need to be moved in a Wheel chair.  

Any system that can only be ridden by svelte toned young people who are able to climb over and around and all of that is not worth the money.  The tunnel size comes from scaling up the Hyperloop 1 tunnel to carry a passenger pot that would meet the same standards as applied to a passenger train in the United States of America. 

And this is exactly why I said earlier people who rely on things like a PhD's mean nothing; because you are lacking the adequate capacity to apply basic level logic/reasoning when your ideas are challenged.  (It's like I said about ThunderF00t's videos, he pulls numbers out of what amounts to thin air that matches his argument and pretends they are the be all and end all).

 

Otherwise you would have noticed that I already pointed out that Canada Line as an example has trains could fit in a but that's less than 4 meters (the actual one they use is 5 meters, but again we are talking about a system when when at capacity is sitting 4 people across it and two people standing next to the seat which is overkill) .

 

The London Underground only has tunnels 3.56 meters.  To suggest a hyperloop would require more is just crazy.

 

I brought up LIGO because it shows that the 1/100 rule does take liberties in terms of how much extra safety factor might be involved...so 2cm for 2m is completely a reasonable amount (if not an excessive amount, as it won't be an ultra strong vacuum).  Ligo gets away with using 1/400.  Not denying that there wouldn't be extra bits of safety factor when humans are involved, but we also aren't talking about ultra strong vacuums.

 

As a few facts as well, talking about safety; Via Rail had passengers stuck for 18 hours.  Canada Line has broken down a few times now and in some cases it took 3 hours before the people could "safely" exit the train.

 

1 hour ago, Uttamattamakin said:

IT's also odd that you would object to that formula.  Since it shows that as you remove pressure from the tube you get a HUGE return in having less drag.  Thereby needing less thrust, and being able to go faster while using less energy.  If anything, my formula demonstrates in simple terms WHY hyperloop is attractive.  Lowering the pressure in the tube even a little bit makes it much more efficient. f

Reading comprehension by you is at 0 at the moment.

 

Where did I object to using that formula?  I object to you with your fancy Masters in supposedly this field lacking the basic understanding of a formula.  Yes, if you plot a curve based on velocity it has a non-linear trajectory...but you seem to fail that if you plot the curve based on density, or based on drag co-efficient then you get *gasps* a line

 

 

You essentially said going from 1 atm to 0.5 atm means drag is about 25% assuming constant velocity...which is nonsense because the equation clearly states it will be 50%.  Again the only variable that changes drag non-linearly in that equation is velocity; which you set as a fixed velocity.

17 hours ago, Uttamattamakin said:

Don't believe me, look at this graph again since you seemed to think it disproved me.

 

Look at when we assume velocity V = 40 and V = 60 (since we assume constant velocity, it should only require 1 but lets do 2 to verify it's in the ballpark)

Look at when we assume velocity V = 60

The standard nose (~0.5 drag co-efficient as defined in the paper)

Drag(N) = ~4700 @ V = 40

Drag(N) = ~10500@ V = 60

 

Sharp Nose (~0.26 drag co-efficient as defined)

Drag(N) = ~2200 @ V = 40

Drag(N) = ~5600 @ V = 60

 

Notice, the only thing that has changed is the drag co-efficient in this example.

Lets divide the drag force from each type to get a ratio.  If it's linear it should roughly match (tolerances of me eyeballing the data since it didn't give it in a table form so probably ~200+- in the guess), if it's non-linear there should be a difference.  Still enough to check, as your claim of things being square should show a drastic difference at half the drag co-efficient.  Remember the predicted should be roughly ~0.52 as per my assertion that the variable contributes to the equation linearly; if your assertion of square terms it should equate to a ratio of ~0.27

 

So lets see the ratio

5600 / 10500 = ~0.53

2200 / 4700 = ~0.47

 

I don't need a masters in order to see that a paper, which was written by multiple PhD's, with experimental data and calculated data is validating my point that drag co-efficient and changing the atm will have similar effects that are linear.

 

 

And not that it matters, my education is a Bachelors in Applied Sciences (Computer science), graduated with honors; in the arrangements of courses I took "top level courses" that actually could be also applied to beginner level masters in mathematics (not joking, there were actually Math majors who were in their Masters program)...and specifically as well if I wanted to I could have taken 1 extra course and gotten a dual bachelors degree in both Applied Sciences AND a bachelors in mathematics, but I didn't want to waste money/time on what amounts to essentially a paperweight.  Some of the literal classes I took literally had the description linear equations, discrete mathematics, etc.

 

1 hour ago, Uttamattamakin said:

In speaking of which Wandering fool.  Do you want a full course on Fluid dynamics?   OR do you want a formula that is good enough for a quick estimate?    A course taught by me cost the state of IL 1242 USD / Contact hour.  For free you get a simple estimation based on what I know of things. 

So far what has been presented has only shown proof towards what I have been stating.

 

Changing atm has a linear effect (reducing it by half, and drag decreases by half).  Reduce aerodynamic by half you reduce drag by half.

Reduce both atm and aerodynamic by half, you can now double your v and get the same drag.

 

If you think the following formula is wrong, then state what you think is wrong

dragforce = -1/2 * C * p * A * v²

C = drag co-efficient

p = density

A = cross-section area

v = velocity.

 

But at the moment it's you stating it density p is a square; which is abhorently wrong given the above formula.  The only other reasoning is to state the one of the other variables C, or A has an equation that also has p in it...but as per the NASA site, and the other papers I linked they all pretty much assume the drag co-efficient is a constant for a given design.

 

The way you are stating it, it's like you are thinking the formula is like the following

dragforce = -1/2 * (C * p * A * v)²

[leadeater]

4 hours ago, wanderingfool2 said:

A note about space usage though, firefly Alpha actually uses a carbon fibre composite for their framework on their rocket (but those rockets are one time use things).

I think the Electron rocket also is carbon fibre.  SpaceX actually considered carbon fibre for their starship, although they eventually switched to steel after realizing steel had better strength across all temperature ranges that it would experience.

Oh yes I know it is used, I was commenting on when Cabron Fibre was developed and became the new hottness, NASA determined it was not suitable. It took a long ass time of perfecting usage of it to get it in applications we have it today.

[leadeater]

5 hours ago, Uttamattamakin said:

I felt lazy so I asked Microsoft Co Pilot.  I'd add to this Space Ship 1 and Space Ship2 designed by Scaled Composites. 

Sure but how many rockets and usages between earth atmosphere to space 

 

I mean yea my comment was inaccurate but Carbon Fibre until SpaceX was never used as a structural material for space travel, going to space.

 

5 hours ago, Uttamattamakin said:

Strong enough to crush a metal tube if the tube isn't made right.  

Then make it right, literally not an issue at all which is what you have been arguing this whole time. The start and end of it is we know how and can make metal tubes do this job just fine. Literally argue about other aspects and not this, this is NOT a problem in the slightest.

 

At least if you want to go on about this in particular focus on cost.

[Uttamattamakin]

59 minutes ago, wanderingfool2 said:

If you think the following formula is wrong, then state what you think is wrong

dragforce = -1/2 * C * p * A * v²

C = drag co-efficient

p = density

A = cross-section area

v = velocity.

Leadeater and I were talking about a relationship between 

 

PRESSURE and Drag force not DENSITY and drag force.    

 

Lets take the equation you have up there.  Pressure is force / Area.  So we could derive a ... drag pressure 

 

Drag force / A = 1/2 * C * p * v²

 

But it's more complicated because p density also depends on pressure.     Consider the ideal gas law, and assume the atmosphere in low pressure is ideal enough to apply it.   

 

PV=NRT.  (N is the number of particles usualy involves avogadros number some versions just use m, R is the ideal gas constant)  Solve for N/V to get a sort of  molecular density.    N/V=P/RT  Putting these together we get. 

Drag force / A =1/2 * C * (N/V) * v²=  1/2 * C * (P/RT) * v²

An equation that has the same, or the same sort of variable on both sides tend to become very non linear and very complicated very fast.  SO instead of doing all of that for a forum post... I just said lets assume it's just a bit more than linear.  

 

Plus it matches the observation that the higher a plane flies, the lower the air pressure, the less fuel is used to maintain velocity. 

59 minutes ago, wanderingfool2 said:

But at the moment it's you stating it density p is a square; which is abhorently wrong given the above formula.  

 

The way you are stating it, it's like you are thinking the formula is like the following

dragforce = -1/2 * (C * p * A * v)²

See... you are squareing the p there which is not pressure it is density.   

 

@Wanderingfool2  Id' take it personally if you weren't like this very often.  You hurl all manner of insults but you don't seem to get the equation you just wrote. 

 

7 minutes ago, leadeater said:

Sure but how many rockets and usages between earth atmosphere to space 

Lol.  Yeah.    Then it comes back to what we both (I think both) tried to explain to folks about a Balloon holding IN pressure VS a chamber holding OUT pressure.  Very different things once one realizes Carbon fiber just makes very rigid balloons. 

 

7 minutes ago, leadeater said:

At least if you want to go on about this in particular focus on cost.

 Eh I'm kinda over it.  I figure if anyone can do this it will be Saudi Arabia which has money independent of spending it wisely OR the PRC which is the worlds factory and can just make things happen by government force alone.   

 

 

[leadeater]

5 hours ago, Uttamattamakin said:

The truth is space has BOTH Always been a private enterprise AND always will be government funded via contracts.   All sorts of private entities were involved with the Space Shuttle.  Just now we have Space X putting their name right on it and using it to service contracts that are also not government. 

 

If it's government funded then it's natation state. Who does the work doesn't matter, it's not like USA Gov builds F35, B21 etc do they?

 

Where as Rocket Labs in my own country is not majority government funded aka not nation state

[Uttamattamakin]

3 minutes ago, leadeater said:

If it's government funded then it's natation state. Who does the work doesn't matter, it's not like USA Gov builds F35, B21 etc do they?

 

Where as Rocket Labs in my own country is not majority government funded aka not nation state

Yeah here in the states we have a way of thinking we are such a capitalist free enterprising country.   YET most companies that do things like Aerospace or tech or even FARMS are all subsidized by and depend on the government.   
 

I'll bet your rocket lab IS truly independent of government.  Meanwhile in the USA. 

[wanderingfool2]

29 minutes ago, Uttamattamakin said:

See... you are squareing the p there which is not pressure it is density.   

 

@Wanderingfool2  Id' take it personally if you weren't like this very often.  You hurl all manner of insults but you don't seem to get the equation you just wrote. 

I'm attacking your premises that show a complete lack of understanding, and your insistence that you are an expert in a field making you the authority.

 

If you notice, or even clued in I said that you seem to be under the belief the formula was like that...notice how I said you seem to think the formula is like that; while if you look above I specify the real formula.

 

Here's a quote of myself so you can see exactly how absurd you sound by somehow quoting as though implying that the one you quoted is the correct formula.

 

1 hour ago, wanderingfool2 said:

If you think the following formula is wrong, then state what you think is wrong

dragforce = -1/2 * C * p * A * v²

 

...

 

The way you are stating it, it's like you are thinking the formula is like the following

dragforce = -1/2 * (C * p * A * v)²

So yea, if you think the bolded formula is the correct formula then you are a lost cause.

 

35 minutes ago, Uttamattamakin said:

An equation that has the same, or the same sort of variable on both sides tend to become very non linear and very complicated very fast.  SO instead of doing all of that for a forum post... I just said lets assume it's just a bit more than linear.  

See the quoted below

6 hours ago, Uttamattamakin said:

If we make the simplest non-linear model and approximate the drag-pressure dependence as quadratic.  

For a constant velocity

Drag ~ pressure^2

6 hours ago, Uttamattamakin said:

So we see from here that at 0.5 Atm for a constant velocity of mach1  the drag force is about 25% of what it would be at 1 ATM at sea level.  So, 2500 hp.   
For a typical high speed train going about 0.25 of the speed of sound the green line on that chart applies.  At 1/2 of at atm a train going  around 300 km/h would encounter 0.066, or 6% of the drag force at 1 ATM.   (When discussing how much of a mag lev would be needed in such a system this needs to be taken account of). 

What I propose would not be 1/2 of an atmosphere but instead to operate at the pressure of 10,00 feet.  Which is 0.7 atm.  People who do not have breathing problems can breathe for hours at this level of pressure.   This is the altitude a jet will dive to if it experiences decompression at cruising altitude. 

Don't try to gaslight me.  You literally made made a linear system non-linear in your assumptions here and made some a crazy statement which is false.

 

ATM and density are linked linearly as well: https://www.omnicalculator.com/physics/air-density
1 ATM @ 32C with no moisture = 1.09232 kg/m3

0.5 ATM @ 32 C with no moisture = 0.54616 kg/m3

 

So back to what I've been saying changing p has a linear effect...you are talking about 1atm and 0.7 atm and mindlessly pulling that it's now somehow a quadratic effect to justify; when in reality you still are looking at a linear relation...unless you again can show a formula that is proving otherwise.

 

45 minutes ago, Uttamattamakin said:

Drag force / A =1/2 * C * (N/V) * v²=  1/2 * C * (P/RT) * v²

Notice how only the velocity term is squared in your equation.  You mentioned assume a constant velocity...which means you guess it...according to your formulate you can replace v^2 with a constant and there  you have it no more squared terms.

 

This is why I attack your facts because you are claiming to be an expert in a field and you make arguments like the above.  Either you truly don't understand the topic, or you are arguing in bad faith.

 

 

Here's some NASA documents for you:

https://www.grc.nasa.gov/www/k-12/VirtualAero/BottleRocket/airplane/drageq.html

They are using the same formula that I have been using all along, and is our baseline
D = Cd * A * .5 * r * V^2 

Lets see how they define density

https://www.grc.nasa.gov/www/k-12/VirtualAero/BottleRocket/airplane/density.html

Quote

we could define its density to be the mass divided by the volume

So yea, 1 atm vs 0.5atm you will have density in the equation to be effectively linear (It is technically associated with temperature humidity etc, but it still follows again a linear path).

 

 

Let me put it this way, you have 2 knobs one that changes "pressure" and one that changes "drag co-efficient".  You turn the pressure knob...what part of the formula makes you think that the drag will increase at a quadratic rate?

[suicidalfranco]

So of this thread just the inevitable bickering between a physicist and an engineer? Cause if so the only person missing is a mathematician and we can get a full circle

[Uttamattamakin]

2 hours ago, suicidalfranco said:

So of this thread just the inevitable bickering between a physicist and an engineer? Cause if so the only person missing is a mathematician and we can get a full circle

Basically. LMBO. 
 

@wanderingfool2  I have explained how and why you are so far off for trying to use simple linear models for an extreme engineering question like this.  There are equations that you see in the textbook in intro physics.  Then there are the ones that consider all the factors one sees in real life.  You know the kind that make it necssary to model complex systems with super computers.  

 

 

 

The fact that you are so wrong that the above quote applies all while making it about the whole idea that I know what I litterally teach to other people and have a degree in..    It reminds me of when I teach remedial math and theres one student who is CERTAIN they are right and that both I and the computer homework system that graded them are both wrong.    Then they get angry when I do the problem again and show them that they are wrong.  Thats. you. 

My final word on this.  

There are things which violate the laws of physics and they don't exist for that reason.  Like traveling faster than light (without perhaps warp drive). 

Then there are things like Hyperloop, Lk99 and perhaps room temp super conductors in general, and the 12VHPWR standard.  They PUSH the laws of physics, are very hard to make work for that reason, and if they work even a little at best you get Bubbling Plastic on your GPUs power connector. 

 

Time to relax