
A plane that will be able to fly anywhere in the world within 4 hours - dnetesn
http://www.sciencealert.com/this-plane-will-be-able-to-fly-anywhere-in-the-world-within-4-hours
======
nickhalfasleep
They talk over and over about their engine, when there are plenty other hard
problems they do not have solutions for. For instance light enough cryogenic
fuel tanks don't exist. This was part of the reason the Venture Star / X-33
never met their weight budget.

~~~
ChuckMcM
Came here to say the same thing. And note that you're "burning" 400MW of
energy in the heat exchanger (transferring it to the helium) at some point you
have to re-cool that helium back to liquid) if you outgas the helium you are a
net loss because helium has a limited supply. Doing it with hydrogen doesn't
get nearly the thermal mass. So it is a really really cool engine, but it
remains to be seen how practical it can be.

The second thing, consider the experience from the SR-71. To stay light and
still be able to withstand the frictional heating of the air at mach 5
requires some pretty exotic materials. And matching thermal properties for
materials at mach 5 vs sub mach. Covering the whole thing in thermal tiles
adds weight which comes out of the payload.

To me, adding on the possibility that it could be some sort of Mach 5 super
airliner, suggests that the practicalities of it as an SSTO platform are
perhaps not nearly so compelling as once thought. Fortunately they were not
talking about the multi-gigawatt ground lasers to boil hydrogen. That idea,
while nominally physically possible, is impractical to imagine the rest of the
world being "ok" with.

~~~
cstross
_To me, adding on the possibility that it could be some sort of Mach 5 super
airliner, suggests that the practicalities of it as an SSTO platform are
perhaps not nearly so compelling as once thought_

Ding!

Yeah, that was my reaction. If SpaceX get the reusable first stage tech
running on Falcon 9, then they shave $40M off the cost of each launch (the
first stage fuel and oxidant costs $300,000; the stage itself, including nine
motors, costs around $40M). Even if each flight costs a couple of mill to
refurbish and can only fly 10 times, they'll still have cut the $40M price to
around $6-7M.

Meanwhile, here's Skylon, a decade late off the starting blocks. With the
Sabre engine running on liquid hydrogen, which is a beast to handle, with
valuable He as a consumable.

Frankly, the airliner option looks silly to me. The only _real_ target market
for a Mach 5 in-air vehicle is the military.

~~~
outworlder
Not much of a target at that, otherwise they'd still be flying the SR-71,
which doesn't need as many... unproven technologies.

------
jessriedel
Honest question: Can someone explain why a Mach 5 air-breathing engine is
important for reaching low-Earth orbit (~Mach 25)? I still don't understand
after watching the video.

I recall from a video interview that Elon Musk is skeptical of the utility of
air-breathing engines for economic access to LEO since, as he put it, the
atmosphere is "thick as soup" and you basically want to get out of it ASAP
before you get up to orbital velocity. Breathing air up to Mach 5 allows you
to save some weight, but you have to bring enough liquid O2 for the rest of
your acceleration from Mach 5 to Mach 25. So is the idea that this modest
savings in weight is all that's needed for a single-stage to orbit?

~~~
pwnna
Some background: This company's engine is based on its previous design, the
SABRE engine. That engine is designed to reach an altitude at 28km, flying at
Mach 5 (which works out to be about 1.5km/s at that altitude, ~15% of orbital
velocity at LEO). After that the engine is designed to switch to a rocket
mode, where it burns fuel and oxygen it brought, rather than taking it from
the atmosphere.

Since the an air breathing engine is much more efficient (10x) than a
traditional rocket engine, it allows the launch vehicle to conserve mass that
would otherwise be used to overcome the high drag encountered in lower
altitudes. You can roughly think of this as a rocket with all of its mass
being launched at 28km, with a velocity of Mach 5 already.

"Getting out of the atmosphere" is a pretty vague statement. Atmospheric
pressure and density is about 1-2% that of the ground. So drag at these
altitudes will be less. However, some quick and dirty calculations by me makes
this seem like a relatively small number compared to the amount of energy it
takes to actually get to orbit. Quick search indicates the same as well[1].

However, a "thick" atmosphere is something that has to be dealt with. For
example, rockets also need to overcome pressures that exists at lower
altitudes. If you take a look at any rocket launch videos, you will notice
that the exhaust at higher altitudes (typically about 2-3 minutes after
launch) will expand outwards with respect to the rocket itself. This means
that the flow out of the rocket engine is "underexpanded", making the engine
less efficient than it would be otherwise. By starting your rocket engine at a
higher altitude, you can improve the efficiencies by designing your rockets to
lower atmospheric pressures (I don't know if this is done for the SABRE
engine, but this is theoretically possible).

So based on these, the main motivation for this is _probably_ for the mass
savings and efficiency. Additionally, this engine presents itself with
potentials for complete reusability, which is very attractive as most current
launch cost is from the unrecoverable launch vehicle itself.

[1]: forum.nasaspaceflight.com/index.php?topic=9959.msg189860#msg189860

~~~
iwwr
>So based on these, the main motivation for this is probably for the mass
savings and efficiency.

They plan to invest all those savings into a single-stage-to-orbit launcher.
It's appealing in a similar manner that SpaceX's stage-return strategy, but in
a one-spacecraft package. High-mach aircraft will find other uses too besides
orbital launchers.

As for saving a 'mere' 15% at launch that can be crucial from a payload
perspective in the rocket equation.

~~~
m_mueller
Starting the rocket at 15% velocity is not the same as saving 15% of the
energy though.

* you have slightly reduced gravity field

* you have a big win in reduced drag energy loss

* these wins have an exponential effect on your fuel requirements at sea level, since less weight in additional fuel again means less fuel to transport that fuel up there etc.

* On the other hand, energy is proportionate to velocity squared, so that gives you less than 15% savings if you assume no atmosphere.

Looking at the wiki[1] these SABRE engines (according to manufacturer specs)
will have a 7-8 times higher fuel efficiency than typical rocket engines while
in atmosphere (3500 seconds vs. 450 seconds specific impulse). Since this has
been peer reviewed by ESA, I'm trusting these numbers. The ascend profile of
these machines will look quite a bit different than rockets, so it's hard to
compare the efficiencies, but the 'rocket starting at mach 5 horicontal
velocity and out of atmosphere' comparison seems to be a good intuition to me,
although we still have to reduce it by the amount of fuel that has been used
in order to get to that point (which will not be insignificant, even though
it's 7.7 lower). We also shouldn't forget that the hybrid system has a thrust-
to-weight ratio of 14 compared to 150 of SpaceX' merlin engine, which means
that it will take longer for such a system to reach the same speeds, reducing
its efficiency gains. The reduced weight of the whole orbiter will make up
some of that though, so unless we get more publicised informations on the
whole ascend path along with simulated data it's hard to tell. All I know is:
When using the simplified versions in KSP these hybrid engines make a lot of
sense, i.e. it's the easiest way of getting an SSTO there ;-).

[1]
[https://en.wikipedia.org/wiki/SABRE_(rocket_engine)](https://en.wikipedia.org/wiki/SABRE_\(rocket_engine\))

------
chx
Cool. This
[http://en.wikipedia.org/wiki/Reaction_Engines_A2](http://en.wikipedia.org/wiki/Reaction_Engines_A2)
is six years old. What's the news?

~~~
gilgoomesh
There is no new information here. It looks like sciencealert.com got its
information from businessinsider.com's Dec 11, 2014 article which references a
"new video" as its source:

[https://www.youtube.com/watch?v=yLD1TPsEi3E](https://www.youtube.com/watch?v=yLD1TPsEi3E)

but that "new" video is from 2012.

------
jzwinck
The article title refers to a "plane engine" not a "plane." There is a huge
difference: the passenger plane airframes everyone knows and flies on are made
by totally separate companies (Airbus, Boeing) from the engines (Rolls Royce,
GE, Pratt & Whitney).

A great engine will get you nowhere without a great airframe, and when you
start talking about supersonic passenger service, you have to add politicians
as well. For example, the Concorde briefly flew between London and Singapore
but was stopped partly due to complaints from the Malaysian government. And of
course the Concorde is long since retired, despite no comparable replacement
existing; this has nothing to do with its engines not being good enough.

~~~
rtpg
Also important to mention why Concordes got cancelled: even with cheap oil,
there wasn't much demand for the plane. After a certain point, not much
changes between a 4 hour flight and an 8 hour flight, especially if you have
red-eye flights. Unless we figure out a way to have fast planes be cheaper to
run than current models, then markets seem to show lack of interest in a
Concorde-like

~~~
smikhanov
Correct, especially with the added time of getting to, from and through the
airports.

Some materials about a short-lived Hindenburg airship
([http://www.retronaut.com/2011/04/inside-the-hindenburg-in-
co...](http://www.retronaut.com/2011/04/inside-the-hindenburg-in-colour/))
mention its travel time between Europe and North America to be 40+ hours. I
wonder, if they were available today, would there be a demand for this type of
travel? For me the choice between a seat in 8 hour flight or a comfortable
cabin in 40 hour is often not in favour of speed.

~~~
christoph
There have been murmurs of this possibly having a renaissance. [1]

I read an article in a magazine sometime back as well, talking about the
possibility of luxury flights like London -> New York, but boarding in a nice
piece of park land instead of an airport. The flight would be much longer, but
there would be essentially no jet lag, much nicer quarters to sleep in, five
star restaurant food, etc. It certainly seemed to me there is potentially a
niche market there somewhere.

EDIT - all I can find is a DailyMail(!) article -
[http://www.dailymail.co.uk/home/moslive/article-1357747/Airs...](http://www.dailymail.co.uk/home/moslive/article-1357747/Airships-
Pioneering-Brits-heralding-dawn-new-Zeppelin-age.html)

EDIT 2 - seems to be this company -
[http://www.hybridairship.net](http://www.hybridairship.net)

1 - [http://m.ibtimes.com/zeppelins-making-comeback-aeroscraft-
ai...](http://m.ibtimes.com/zeppelins-making-comeback-aeroscraft-airship-
future-air-transportation-says-california-company)

~~~
mariuolo
> boarding in a nice piece of park land instead of an airport.

I don't see this happening in the current climate of hysteria.

------
tdicola
I think I've read this exact same story for the last 25 years. Will believe a
Mach 5+ commercial jet when I see it.

~~~
cabalamat
It goes back longer than that; the HOTOL project started in 1982 --
[http://en.wikipedia.org/wiki/HOTOL](http://en.wikipedia.org/wiki/HOTOL)

~~~
johan_larson
And even earlier:
[http://en.wikipedia.org/wiki/Supersonic_transport](http://en.wikipedia.org/wiki/Supersonic_transport)

I suspect this is one of those Big Challenges that keeps tempting aeronautical
engineers, and they try to apply the pushing-the-envelope high tech of their
era to it. The problem seems to be the economics. There aren't a lot of people
who are willing to pay 10x prices (or whatever) for 3x reductions in travel
time.

------
moron4hire
It's basically the Sears-Haack body with some engines bolted on:
[http://en.wikipedia.org/wiki/Sears%E2%80%93Haack_body](http://en.wikipedia.org/wiki/Sears%E2%80%93Haack_body)

------
minor_nitwit
Ok, these guys claim to have invented a great engine, really just the pre-
cooler. Why are they trying to build a plane instead of licensing it to
others? That seems to be several orders of magnitude more difficult and
increases the likelihood of failure.

~~~
imaginenore
Do you know any Mach 5 planes?

~~~
jschwartzi
Does he know of anyone in the tightly-regulated airline industry who would be
crazy enough to build a completely new airframe and engine around a currently-
experimental precooler?

~~~
foobarian
And using LH2 and LOX as fuel? With 3g acceleration? :-)

~~~
aragot
At that speed, I wonder what accidents will look like. I respect this
technology as totally serious but in case of accident the NTSB may just
delegate the investigation to a Darwin prize:

Is the plane sensitive to slight variations, like a few people walking in the
alley? Since at Mach 5 we can expect a 5000K temperature for the dislocated
parts [1], will the pieces completely burn and disintegrate before falling
back to Mach 1, effectively acting as a MH370 at each accident, by design? Can
we at least have a video of that on 9gag? Or will we have to search a 5,000-km
radius if we have a 20minutes uncertainty for the accident window?

[1]
[http://en.m.wikipedia.org/wiki/Atmospheric_entry#Shock_layer...](http://en.m.wikipedia.org/wiki/Atmospheric_entry#Shock_layer_gas_physics)

~~~
marcosdumay
With LH2 and LOx as fuel-oxidizer, whatever are the consequences of speed,
they'll be over a completely pulverized ex-airplane, not over entire parts.

Also, with that to speed, I wonder how big a runway this thing would need. It
would probably operate on a completely separated airport, faw away from
cities.

------
Animats
This company has been in business since 1989, and has never produced anything.
Here's their own statement of their own history:

[http://www.reactionengines.co.uk/about_history.html](http://www.reactionengines.co.uk/about_history.html)

That's not encouraging. They own a machine shop company and a sheet metal
company. They should have built a working model of something by now.

~~~
tomelders
That sort of sentiment is why we can't have nice things. These thing stake
time.

Remember, this isn't a kick-starter campaign. They're not trying to dupe other
people out of money on some hair-brained scheme. This work has been reviewed
by the British Interplanetary Society and the ESA. It's real science, tackling
a real problem.

I'll make a bet with you now. In 15 years, the Sabre Engine will be carrying
more payloads into space than anyone else, and for less money than anyone else
can offer.

~~~
darkmighty
[http://longbets.org/](http://longbets.org/)

------
untilHellbanned
Bored Elon musk is already doing this in 3 hours.

[https://twitter.com/boredelonmusk](https://twitter.com/boredelonmusk)

~~~
pariya
I actually bet he reads through that Twitter account and rolls his eyes
because he has already secretly invented half of it.

------
acd
The cool part is that this plane will do US to Europe in 1-2 hours which is a
game changer.

Given how fast it flies, how much would the tickets cost?

~~~
tomelders
I get the impression that the passenger flight times are more marketing talk
intended to frame the technical achievement in terms people can understand
rather than an actual intended use case. Reaction Engines do have plans to use
the engine on a passenger plane, but the Skylon is designed to take payloads
up into space cheaply.

[http://www.reactionengines.co.uk/lapcat.html](http://www.reactionengines.co.uk/lapcat.html)

------
jmnicolas
It looks like a marriage between a SR-71 Blackbird and a Concorde.

At 1.1 billion each, it's about 10 times as expensive as a Concorde. I hope
they will find a way to keep it profitable.

~~~
martinko
The A-380 costs about 414 million usd and can carry ~500 people. A flight from
Europe to Sydney takes north of 22 hours (not counting stop-overs).

Off the top of my head, this new plane seems like a pretty good deal, doing
Europe to Sydney in ~4 hours with 300+ passengers for a unit cost of 1.1
billion.

~~~
hvidgaard
You cannot ignore fuel cost and investment to handle the new fuel. We'll see
what happens, but the most compelling thing to me seems to be the fact that it
burns hydrogen and not kerosene which seems to be more environmental friendly,
but I'm no chemist.

~~~
Luyt
Burning hydrogen releases water vapour, while burning fossil fuels release
carbon dioxide and water vapour. So, you could call it indeed more
environmental friendly if you consider carbon dioxide harmful.

However, hydrogen doesn't occur on Earth in a pure state (at least not in
mineable quantities). There are no hydrogen wells.

Creating the hydrogen (for example, by electrolysis of water) is expensive and
generally a net loss of energy. Maybe storing energy in hydrogen is feasible
if it's generated with excess nuclear or solar electricity.

~~~
hvidgaard
> burning fossil fuels release carbon dioxide and water vapour

Either I have completely misunderstood something, or fossil fuels release only
CO2 and H2O under ideal conditions, which never happens. Add to the fact that
any jet engine is unable to utilize any after treatment systems to remove
harmful products. I am fully aware that hydrogen is rather expensive to
produce, but I think it's possible that nuclear energy, or (as you mention)
excess solar/wind power is several magnitudes cleaner than even the cleanest
burning fossil fuel engine (including all the resources it takes to pump it up
and refine it).

------
Involute
Odd that a picture of dead people (Palermo catacombs, I'm guessing) shows up
beside this headline in my RSS reader (Feedly).

~~~
tensor
Not odd at all. If you scroll down there are links to other articles. The last
one is a photo of the catacomb mummies. Your fead reader simply chose the
wrong photo from those on the page.

------
0x0
Is it still 25 years away from being available to commercial airlines, like
the wikipedia article mentions? Can't wait! :)

------
Zaephyr
So is the breakthrough just the pre-cooler, or the pre-cooler together with
the scimitar engine?

It sounds like the innovation is the helium pre-cooler, but even at that it's
hard for me to understand whether their advancements are in working with
liquid helium for a coolant or in the airflow cooling (both)?

I don't do anything remotely like this in my day job.

------
Gravityloss
Title reminds me of this 30-minute delivery anywhere in the world (much older
technology): [http://designobserver.com/feature/blast-door-art-cave-
painti...](http://designobserver.com/feature/blast-door-art-cave-paintings-of-
nuclear-era/6697/)

------
paulftw
Where does this liquid helium come from, and more importantly where does it go
after it's been heated? Im guessing they release it into atmosphere, so is
there enough helium to mine for this plane to go mainstream?

~~~
sparkzilla
It says in the Wikipedia article that: "The key design feature for the
Scimitar engines is the precooler, which is a heat exchanger that transfers
the heat from the incoming air into the hydrogen fuel."

~~~
sargun
Hydrogen? How are they storing that efficiently?

------
vinayp10
Richard branson was talking about doing this:

[http://www.businessinsider.com/richard-branson-supersonic-
pl...](http://www.businessinsider.com/richard-branson-supersonic-plane-2014-5)

------
wintermute306
I couldn't help but hum the British national anthem while reading this.

~~~
mst
I tried to join you but for some reason my brain decided to produce the
Imperial Death March instead.

------
tim333
Seems like cool technology. I wonder if it'll actually get to fly.

------
BendertheRobot
But, what about the carbon impact of this? It will only be available for one
percenters, no?

~~~
robotresearcher
A hydrogen/oxygen engine emits only water. You can choose to get the hydrogen
from water using from a non-carbon energy source, for a completely carbon
emission free system.

------
EGreg
I hope they dont make too many of these planes that breathe oxygen. We may
need some for humans.

------
dkopi
Hopefully, they've learned a few lessons from the Concorde.
[http://en.wikipedia.org/wiki/Concorde](http://en.wikipedia.org/wiki/Concorde)

------
Thomashuet
This is bullshit, -273°C is absolute zero so unless the plane is on fire, it
can't cool down the air by more than 1000°C.

~~~
nmjohn
Rocket engines get extremely hot:
[http://en.wikipedia.org/wiki/Rocket_engine#Cooling](http://en.wikipedia.org/wiki/Rocket_engine#Cooling)

~~~
Thomashuet
They pretend the air is precooled, not cooled after going through the engine.

~~~
encoderer
Is this not the same concept as any intercooler?

