
Musk's Hyperloop - autotravis
http://prattleat.us/post/5
======
malandrew
It sounds like a Lofstrom loop <http://en.wikipedia.org/wiki/Launch_loop>

~~~
schiffern
That was my leading theory, and "cross between a rail-gun and a Concorde" all
but confirms it. Flight path like a Concorde, propulsion like a rail-gun.
Exploit the natural vacuum above our heads without expensive tunnels.

Let's look at the attributes Elon has described publicly, and see how they
compare to a launch loop:

<https://www.youtube.com/watch?v=uegOUmgKB4E#t=43m13s>

* could be cheaper than CA high-speed rail? Check (no right-of-way).

* "theoretically fastest way" from A-B? Check.

* can't crash? Check (w/ well-designed rails).

* immune to weather? Check.

* twice as fast as a plane? Check.

* lower energy cost than a car? Check.

* self-powering with solar panels? Check.

* stores power w/o batteries? Check.

<https://www.youtube.com/watch?v=L-s_3b5fRd8#t=18m20s>

* requires aerodynamic expertise? Check.

* "ground-based Concorde – as fast as a Concorde, but on the ground"? Arguably. All weight is supported by the ground, and cars take a Concorde-like path.

* rails are not needed? BZZT!! However, he may be talking about the "right-of-way" aspect of rails here.

[http://www.businessweek.com/printer/articles/71590-elon-
musk...](http://www.businessweek.com/printer/articles/71590-elon-musk-
the-21st-century-industrialist)

* leaves right when you arrive? Check (w/ individual pods).

<https://twitter.com/elonmusk/status/224406502188916739>

* isn't a vac tunnel? Check.

Of all the ideas that have been kicked around, the launch loop seems to fit
best. Elon would certainly have been exposed to the idea when brainstorming
for SpaceX.

My only question for the past few weeks has been, "How do you _build_ the
thing?" It doesn't inertially support itself in the air until the rotor is
spun up, and the rotor can only be spun up when it's fully constructed between
the endpoints. Catch-22!

There are basically three ways to do it, each with their own challenges.

Build it in the air. You would need huge numbers of lifting balloons
(presumably of zero-pressure solar Montgolfier design, ala ARCA), and the
portions of the system in the troposphere would be incredibly susceptible to
adverse weather while under construction. You would want to have the entire
thing already built, then unreel it as fast as possible. Smart tethering would
reduce this risk, and the whole thing would need emergency descent parachutes
for operation anyway. This seems like the least unworkable scheme, imho.

Build it in the water. Ocean currents and tides are now your problem instead
of wind. The requirement to survive the corrosive salt water environment puts
additional constraints on material selection. Oh, and you have to shut down
all boat traffic from LA to SF. And your base station either has to be mobile
(to start out in the ocean) or you have to start with a big arc out from the
coastline and "tip it up" vertically. Do the math on how big the rotor
endpoints would be (given reasonable assumptions about bending magnets), and
you quickly realize that building them in place is the only option.

Build it over land. This seems the most unworkable – all the risk of having it
fall (or worse, lose containment), and now you have to build tall towers every
few thousand feet and string a high-tension support cable between them.
Imagine explaining to homeowners that the "rail" we're building above their
house will have parts moving at 10 km/s inside before it lifts off. Ouch.

~~~
keenerd
Over water seems rather reasonable considering what we can do with cable
laying ships.

Whatever method is used to get it up in the air, it'll need to be safely
reversible. Over water bringing it down is much easier. And you'll have to
bring it down for repairs. Every five minutes it will do a full loop.. Iron is
fairly ductile, but those stresses will add up. And wikipedia says the kinetic
energy involved is close to a small nuclear bomb. Back of the envelope math
suggests the iron cylinder would be very thin. It will wear out sooner or
later.

My guess is that Musk's big breakthrough is for a cheap and reversible
deployment system.

I'm double checking my numbers now (and reading the original papers) but the
entire contraption might weight a lot less than we are implicitly assuming.
Like, light enough that a single large plane/blimp could support the entire
cable/sheath system. And a small fleet of planes could safely tow the cable
through the sky. Or a fleet of blimps could support the entire cable while it
was stopped for maintenance. (Both would need a large number of well trained
pilots, it would make the skycrane maneuver look simple.)

edit: The original paper talks about a ribbon 5cm wide and 7.6mm thick
weighing 15.6 Gg. I dropped a kilo in the back of the envelope calculations.
So it would need at least 100 very large aircraft to hold up. Still feasible,
but more than a little crazy.

~~~
schiffern
Interesting. The linear density given is 7 kg/m, which if you wanted to lift
to the tropopause (density 0.35 kg/m^3, temperature ~266 K) you would need a
continuous 30 °C solar Molgolfier balloon 18 m^2 in section, or a 10 meter
strip of of 15 µm HDPE. Not as bad as I thought. Still, it would be hard to
roll it out before sunset.

Hydrogen is another possible lifting gas, with all its associated foibles.
Obviously lifting bags would have to be isolated to prevent catastrophic
failure, but you could get a lot more lift out of them.

This must take place in a La Niña year, when the jetstream is north. Reel out
the track, drag it into place with two airships, join the parts and start 'er
up. You could even name the airships Jupiter and Number 119. ;)

This simplified strategy that would avoid the need for aerial stations at both
ends, intead using a gentle curve achieved by anchor cables and varying linear
density. Acceleration would begin immediately upon departure, leaching energy
from the rotor (generating eddy currents), then contributing it back by
braking off the rail on the descending side.

Of course, maybe I'm just dreaming here…

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KevinEldon
The OP suggests (jokingly?) that driverless cars and Musk's Hyperloop are
somehow in competition. I don't see that. Cars today are about transportation
and cabin conveniences. Why can't the two be separated over time? Your "car"
takes your cabin to the train that takes your cabin to the high-speed rail
(Hyperloop?) that takes you from Atlanta to Kansas City. Perhaps you switch
cabins based on price to transport... maybe you rented a bigger one for local
travel, but don't want to pay a higher price for long range travel... lots of
ifs, but to me, this and/or scenario seems more likely than driverless cars
vs. Hyperloops.

~~~
autotravis
> Here I was getting excited about Google's work on driverless cars.

OP here, only competing for my (unfortunately limited) excitement. There is
definitely room in this world for both.

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SuperChihuahua
I believe that the Hyperloop is some sort of cannon. He has earlier revealed
that it won't need a tube or tracks

Edit: Source to the no-tube from Elons twitter: "Will publish something on the
Hyperloop in about four weeks. Will forgo patents on the idea and just open
source it. Not a vac tunnel btw."

~~~
lowkey
Are you sure he specifically said it wouldn't require any sort of tube? I was
under the impression that Elon's Hyperloop would be a derivative of the
concept of Evacuated Tube Transport - a capsule containing passengers launched
inside a tube under vacuum (eliminating air resistance) and levitated using
some sort of MagLev (eliminating rolling resistance).

The concept isn't entirely new but having someone with Musk's credibility and
resources as a proponent may be the catalyst required to make it happen.

I distinctly recall seeing some PR material circling the internets a few
months back from a consortium known as ET3.com The group claims to have been
working on a similar project for the past decade.

~~~
omegant
I don´t think is a vacuum tube, it seems more like a tube with railgun like
propulsion(elevated via towers, like power lines, even using the same power
lines routes), but the guiding is maybe based on aerodinamics. There must be
some kind of sound contention because he says it is supersonic.

He also said that it would be energetically independent so he may be using the
external part of the tube to install solar cells, and the tube itself may be
used for accumulation (capacitation maybe?).It doesn´t need to be air tight,
just somehow sound insulated. The steering or "levitation" inside the tube may
be obtained via shock waves (note his actual experience with high energy
aerodinamics due to the development in spaceX).

He surely is taking advantage of the knowledge gained in the R&D of SpaceX,
Tesla and Solar city.

~~~
schiffern
With all the aerodynamic losses in such a system, it will use much more energy
than a plane ride.

"it would cost you much less than an air ticket or car – much less than any
other mode of transit – because the fundamental energy cost is so much lower"
– <https://www.youtube.com/watch?v=uegOUmgKB4E#t=46m03s>

Oh, and he said elsewhere that you wouldn't have to wait, which implies
individual cars. That means much more frontal area per person than a regular
plane.

My money is on this: <http://news.ycombinator.com/item?id=4806350>

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squid_ca
The cynic in me is reminded of the Segway at this point. I'm not calling
bullshit on this, but I'll wait to get excited when something is actually
shown.

~~~
mertd
There is a segway-esque secrecy around it. However if there is one person I
would give the benefit of the doubt, that person would be Elon Musk, and he
said they'll open source the project.

------
mtgx
The real question is - will you have to go through TSA first to get in it?

~~~
kmfrk
I'm sure people will find a way to lose my luggage.

------
lutusp
Since there are no details, we can only speculate. There are only a few
practical implementations. At the top of the list is an evacuated tube.

The linked article says it's desirable to do this without requiring a right-
of-way or moving people out of their homes. So that puts the tube below ground
level -- well below.

Let's say an evacuated tube, below ground level, in California, between San
Francisco and Los Angeles. This really isn't going to work, because (all other
considerations aside) the route crosses any number of known geological faults
that are in constant relative motion -- some creep past each other, some wait
and then periodically move all at once in an earthquake. You can't build a
subsurface tube that crosses geological faults.

I don't think this is a practical idea. But it's a nice one in principle.

~~~
schiffern
>At the top of the list is an evacuated tube.

Except for the small problem that Elon said it's not an evacuated tube:
<https://twitter.com/elonmusk/status/224406502188916739>

~~~
lutusp
Yes, I noticed since I wrote the original, but that might be smoke. It's not
obvious how the system would work without some sort of dedicated pathway that
remains the same day after day. The word "tube" leaps to mind. :)

~~~
schiffern
This discussion may get you started:
<http://news.ycombinator.com/item?id=4806350>

TL;DR Build a rail with a high-velocity rotor inside that inertially supports
it above the atmosphere. Essentially it's a space fountain with two base
stations instead of one.

So yes there's a pathway, but since it's not on the ground it requires no
right-of-way.

~~~
tzs
I'm not so sure about the right-of-way issue, since we are talking about a
permanent structure. The case law that weakened the old "Cuius est solum, eius
est usque ad coelum et ad inferos" ("for whoever owns the soil, it is theirs
all the way up to Heaven and down to Hell") rule, as far as I've seen, all
involved aircraft passing over land. I'd not be surprised if a court
considered that case law irrelevant when it comes to permanent structures
overhanging someone's land.

~~~
schiffern
Good question! I found a summary of the ruling:

>However, while the Court rejected the unlimited reach above and below the
earth described in the common law doctrine, it also ruled that, "if the
landowner is to have full enjoyment of the land, he must have exclusive
control of the immediate reaches of the enveloping atmosphere." Without
defining a specific limit, the Court stated that flights over the land could
be considered a violation of the Takings Clause if they led to "a direct and
immediate interference with the enjoyment and use of the land."

Would a hyperloop cause direct and immediate interference with the enjoyment
and use of the land? It might if it failed!

------
wololo
> killing countless people daily

2.09% of deaths, according to
<http://en.wikipedia.org/wiki/List_of_causes_of_death_by_rate>

Question: what would an Elon Musk of those even more common causes of death
build?

~~~
w1ntermute
For cardiovascular disease, how about a way to stop people stuffing their
faces with greasy and fattening food?

~~~
whatusername
So the Paleo Diet community (and Taubes/etc) would say that the greasy food is
part of the solution (and that some perceptions of "fattening" food are wrong)

~~~
stcredzero
I am doing a low carb thing, and as far as my experience goes, I think they're
right.

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endlessvoid94
I suspect there is no hyper loop. I wouldn't put it past Elon to use his
reputation to spur people to think big about these kinds of problems.

It's worked, too. The ideas people have had, just trying to "figure out" what
the hyperloop might be, are very interesting and diverse.

~~~
pdenya
I've never heard anything about Elon Musk that indicates he speaks lightly
about things like this. He has an amazing track record and a habit of taking
on huge problems. There is no reason to think that he's not working on a hyper
loop.

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Zenst
Would this possibly be using a railgun to initiate takeoff speed (reducing
fuel a lot) and then some for a plane that then obtains very high speed in
very high orbits to then be able to land and use existing airports.

This is only logical given the prospect to use a railgun type launcher to
eliminate booster rockets or reduce fuel for space flight. So would marry in
with other avenues of research and as such be less of a risk and Musk don't
like risk.

This at least would fit the criteria, maybe with the initial speed a form of
electric powered plane, maybe Musk and Dyson could get together and invent a
good electric jet engine (yes probably be ion based but still).

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swalsh
In the past, it sounded like he really wanted to see someone work on the idea,
but was not interested in doing it himself. Now it seems he's coming around to
the idea. This is really exciting.

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rehack
Elon Musk is Leonardo Da Vinci of the present times. More power to him.

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ekianjo
" This is over 100 years after the first mass-produced automobile was sold,
with the announcement of (another) successful nano-scale teleportation
experiment just the other day."

So what? This is 40 years after the first Man walked on the Moon and we are
still all living on Earth. It's been about 60 years we have discovered the
double-helix structure of the DNA and we still have yet to see revolutions in
medical practice coming from it. What is your point, exactly ? There are clear
reasons why no huge technology leaps take place at once. Most innovation is
progressive, iterative and it is very likely that you will not see a drastic
change of technology within your lifetime.

~~~
tsewlliw
Perhaps I am just much more impressed with the last 30 years than you. I'm not
a point-by-point rebuttal man, but its very tempting. Try thinking about the
massive changes if you don't limit radical progress to being in a straight
line going the direction you want.

~~~
jacquesm
Cars were doing 100 Mph on the German autobahn in the 60's, they're not much
quicker today and most drive a lot slower than that.

There is progress, but on the transportation front from a practical point of
view the biggest one so far is the electric bicycle.

~~~
jlgreco
Fastest production car from the 60's that I can think of would do 171 mph
(Lamborghini Miura). The fastest production car today will do damn close to
100 mph more than that (Bugatti Veyron Super Sport).

Certainly the top speed of either of those cars isn't practical, but the
reason that the Veyron can go so much faster is that there have been massive
improvements in automobile technology since the 60s, in just about every every
way imaginable. Safety, efficiency, control, materials tech, aerodynamics,
etc. That we still drive so slowly can be probably attributed to momentum in
automotive laws and/or driver skill / lax license requirements. If we were
willing to invest more in our roads and stop thinking of driving as a right
instead of a privilege, we could be driving _much_ faster today.

~~~
jacquesm
The biggest factor is reaction time.

Also, above 100 Mph or so the aerodynamics change substantially. There is a
clear cut-off point above you are definitely in 'no mistakes' territory, even
ignoring a bit of cross wind as you come out from under an overpass get get
you slammed into the guardrail or driven off the road.

Add to that ice, snow, rain, night conditions, glare, low sun and so on and
pretty soon the driver (automated or not) is not the limiting factor but
physics and getting reliable sensor inputs is.

Anything over 140 will probably not be practical for mainstream deployment,
even in Germany where there are lots of skilled drivers and it isn't rare to
see an old lady do 150 Km/h there is a sharp drop-off above that point
reserved for those the possession of more money than brains. It simply isn't
practical from a fuel consumption and safety point of view and even the safest
cars are death traps at speeds beyond that.

See 'crashedexotics.com' for the end result of that route.

~~~
jlgreco
Certainly when you get up into the sort of speeds things become very tricky
and unpractical. The problem right now though isn't really that we aren't all
driving at 100+, but that we still have all of those straight as an arrow
55/65mph roads criss-crossing fly-over country in the US. Those may have made
sense at some point, but modern cars can easily do 100mph on those roads with
no particularly unusual danger. Pretty much everywhere in this country speed
limits are artificially low though. Most country/wooded area roads don't make
any sense in cars with ABS or traction control; my limiting factor on most
Pennsylvanian roads is the danger of deer, not road geometry or car
capabilities.

I think with the spread of autonomous driving technology we'll be able to see
even more proper, and reasonably safe, speed from cars.

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Uchikoma
Sounds like the Segway.

~~~
ferferferfrr
Agreed

