5 ms·

Reaction Engines brings us a step closer to Mach5 commercial air travel

48 points by kareemm 12y ago

findjashua 12y ago
I'm assuming this can't be used for flying over land due to sonic boom?
- masklinn 12y ago
  Depends which land and — most likely — depends who builds it. It's not like the US forbid overland supersonic flight for their military planes (and overland commercial supersonic flight was only banned as the US's sole SST program was cancelled)
  - Crito 12y ago
    The US military is typically only allowed to go supersonic over land in the US in certain special areas.
  - hollerith 12y ago
    During 54 years of living in 5 different metropolitan areas of the U.S., I've never heard a sonic boom. (I know what one sounds like because they were frequent during a vacation I took in West Germany a long time ago.) The Blue Angels, for example, are not authorized to exceed the speed of sound: http://www.blueangels.navy.mil/show/faq.aspx http://www.blueangels.navy.mil/show/faq.aspx
    - rsync 12y ago
      I lived near colorado springs in the early 80s, as a child, and I can remember on two occasions being (figuratively) knocked out of bed by a sonic boom. Presumably from the Air Force Academy. Only happened those two times the entire time we lived there - presumably someone got in trouble for it...
soperj 12y ago
I've read about this before, and I do think it sounds pretty neat, but a small part of me hopes it doesn't work for putting satellites into space, only because the technology doesn't help us land on other planets.
- acchow 12y ago
  I disagree. Familiarity with microgravity and the vacuum of space in orbit will make developments in interstellar travel that much cheaper.
  - soperj 12y ago
    Cool. Love getting down voted for having an opinion & starting the conversation.
  - idlewords 12y ago
    I think we're pretty familiar with vacuum at this point. The obstacle to practical interstellar travel is 99.99999% propulsion, which you don't learn a lot about by endlessly falling in a circle.
    - XorNot 12y ago
      And the obstacle to propulsion is the inability to lift large payloads cheaply enough into orbit to start with. The problem is we can't build big things in LEO. At the moment its that our entire LEO-access infrastructure is woefully underdeveloped.
- Zigurd 12y ago
  The first few miles are the most expensive.
- bjelkeman-again 12y ago
  I saw a very good presentation by the CEO of Reaction Engine the other day, where he went through where they are at with the engine (Sabre) and with the vehicle (Skylon). He showed how Skylon could lift an interplanetary vehicle in pieces, just like the International Space station was built from modules. The Skylon/Sabre tech will certainly help us reach other planets, as the first 100 km to orbit is the really expensive part, and Skylon/Sabre addresses that well I think. They need some more development money though.
sp332 12y ago
So they can cool the engine, but what about the heat on the rest of the plane?
- icegreentea 12y ago
  The SR-71 Blackbird cooled itself through a combination of radiative cooling (hence the black), and using its fuel (that was about to be burned) as a heat sink. Some combination of these techniques (and others) would probably be used.
  - idlewords 12y ago
    Here the fuel is already being used as a heat sink to cool the inlet air. Liquid H2 doesn't have that big a heat capacity, you can't use it cool the fuselage and the cabin air and your cocktail and still expect it to keep the engine from melting.
- NamTaf 12y ago
  That's not the problem. The problem is that hot inlet air means that once you burn your fuel, the air post combustion stage is then too hot and melts things.
  - idlewords 12y ago
    It's a huge problem, unless you don't mind a flying oven. In the SR-71, the crew had to wear special cooling suits (presumably these will be available in first class).
    - virtue3 12y ago
      meh, insulated cabin. No big deal. just shitloads more weight and/or space (nasa aero gels would probably be great here). Aka this thing is never going to see commercial flight.
    - NamTaf 12y ago
      What I mean is that from a material standpoint, the engine turbine temperature tends to be the design limiting factor. Yes, there's going to be hot spots on leading edges due to stagnation for example, but you're not burning fuel there to intentionally jack the temperature up.
lubesGordi 12y ago
the video is 2 years old
idlewords 12y ago
We're not going to have Mach 5 commercial air travel for the same reason we don't have Mach 2 or 3 commercial air travel. The economics just don't work. That reason is much more boring than the technical obstacles, which are formidable, fun to try to solve, and kind of beside the point. In that sense, this problem resembles a lot of software engineering. But just to keep this comment from being too depressing, here's one technical gripe: consider that liquid hydrogen is an extremely bulky fuel, even if you don't include the necessary insulation. Notice how nearly the entire volume of the satellite launcher in the diagram consists of hydrogen tank. There's not a lot of room in there for passenger lounges and drink trolleys.
- twic 12y ago
  > The economics just don't work. Given that you don't know how much this will cost to operate, you can't possibly know that, right? At some point, i think i read a claim that an airliner based on this technology would be able to supply Europe - Australasia trips for about the same price as a business class ticket on a conventional airliner on that route. Passengers currently buy a fair few of those tickets; some might choose to do the trip in two hours instead of twenty-four in exchange for a smaller seat and the loss of a couple of meals.
  - idlewords 12y ago
    We know how much the Concorde cost to operate: a zillion shittons (metric) [http://www.concordesst.com/retire/faq_r.html http://www.concordesst.com/retire/faq_r.html] . And that was with proven technology and all the sunk costs behind them. I think that makes a sensible floor for this project, unless you are willing to argue that researching and deploying this completely new technology would somehow cost less.
  - jvm 12y ago
    Is there really a tremendous amount of demand on the Australia / Europe segment? If London/NYC wasn't viable for the Concorde (probably the most popular international airline segment), I can't imagine the demand being higher on routes to Sydney. If the fixed costs of a flight are high, it will likely be even more expensive than the Concorde on trans-Atlantic routes.
ufmace 12y ago
Sounds a little odd. I'm not really an expert on this area or anything, but it sounds plausible that if they are able to cool the incoming air stream to that temperature, then they might be able to make the speeds they're claiming. But I have to wonder, not only how they made a heat exchanger capable of cooling the incoming air that fast, but what are they doing with those megawatts of heat that they're taking out of the air? They claimed air temperatures coming out of the heat exchanger of -150, so where are they getting a cooling fluid colder than that to do exchange with?
- idlewords 12y ago
  The incredibly huge tank of liquid hydrogen not pictured in the diagram. The same one that makes the idea completely unfeasible for commercial transport.
TeMPOraL 12y ago
Nitpick about the title[0], but it's a kind of thing that really irks me. It's "Reaction Engines", not "Reaction engines". It's a proper name of a private limited company, not a class of engines. [0] - at the time of writing this, the title was: "Reaction engines bring us a step closer to Mach5 commercial air travel".
- alexvr 12y ago
  Based on the grammar following "Reaction engines," it's clear that the OP simply thought the new engine was actually called a "reaction engine" (I'm sure the author would not write "Google bring us closer to autonomous cars")
  - TeMPOraL 12y ago
    Well, the article clearly states that Reaction Engines is a rocket company, so it follows that OP must have not read the article very carefully, if at all.
  - MaysonL 12y ago
    The Star is a British paper: UK usage would be Reaction Engines bring, and yes the author would write "Google bring...".
- kareemm 12y ago
  I'm the OP. I'm 90% sure I submitted it as "Reaction Engines" - I was surprised it was "Reaction engines" when I visited the site an hour after submitting. I would've edited it when I revisited the site, but wasn't able to by that point. But, then, it's also entirely possible I submitted it incorrectly.
  - dang 12y ago
    No, that was our mistake. Sorry—fixed now.
parley 12y ago
In a previous post (a little over a year ago) about the same engine I posted a link to a video with a Q&A with Elon Musk where he was a bit pessimistic about the idea. I'm not a rocket scientist so I wouldn't know the first thing about it, but if anyone is interested in his (then) opinion it's after 48m55s in the video here: http://www.oxfordmartin.ox.ac.uk/videos/view/211 http://www.oxfordmartin.ox.ac.uk/videos/view/211
- XorNot 12y ago
  Elon Musk isn't the expert in this area. Practically no one except Reaction Engine employees and some guys at Area 51 are - in the entire world. It's certainly not an easy thing to do, but since they actually do seem to have the heat exchanger figured out then that's kind of a big deal. Burying the lead is the whole commercial air travel angle though. What they're building is a fully reusable, cheap to operate SSTO to low earth orbit.
  - bjelkeman-again 12y ago
    ESA did a review of Skylon and the Sabre engine and said "...the SKYLON vehicle can be realised given today's current technology and successful engine development." http://www.reactionengines.co.uk/space_skylon.html http://www.reactionengines.co.uk/space_skylon.html Of course, there needs to be a successful engine development project. Which needs another billion or two to complete according to the CEO/MD of Reaction Engine. (He was a bit more specific than that when I heard him say it, but it is in the ballpark.)
trhway 12y ago
the thermodynamic economics of ram/scram jets at the Mach5+ speeds is almost killed compare to the rocket engines by the fact that oxygen is only 20% of the incoming air, while the whole incoming air needs to be processed through the engine, ie. compressed/(may be cooled interstage)/heated/expelled. Various unavoidable losses on this 80% (nitrogen) of the incoming air eat deeply into end-result efficiency of such engine when compared to a rocket engine.
ChuckMcM 12y ago
The trick is, and it is a trick, to "instantly cool the air". Think about that for a moment. Generally the way most 'air breathing' engines work is that they take air, heat it (which expands it (thanks Boyle!)) and toss it backwards which imparts a forced in the forward direction (thanks Newton!). The difference in temperature between the inlet and exhaust temperature of a jet engine is a component of its efficiency. (see http://en.wikipedia.org/wiki/Jet_engine#Energy_efficiency http://en.wikipedia.org/wiki/Jet_engine#Energy_efficiency for some math :-) But basically if you're suddenly cooling air it gets smaller, which creates a lower pressure, and was used effectively in steam pumps to create the vacuum needed to lift water out of mines. So the Reaction Engines concept takes really hot air that is compressed because it is being pushed out of the way by the air frame, then super cools it which causes it to become much smaller, and then dumps that into the engine. Which then heats it up again and pushed out. If I understand the theory correctly, it takes heat from the air, removes it and puts it into liquid hydrogen (which then becomes vaporous(sp?) hydrogen) and then burns that hydrogen with residual oxygen to put the heat back into the air plus what ever is extra from the hydrogen. What bugs me about it is that it seems to double count the energy in the air rather than single count it. But I'm interested in seeing one of their machines in action. If someone knows whether or not there is a violation of thermodynamics in there I'd like to understand that. That said a mach 5 vehicle with a range of 12,000 miles and a payload capacity of 15 tons has much more interesting uses than carrying passengers I think. Would make a heck of a cruise missile.
- trhway 12y ago
  >That said a mach 5 vehicle with a range of 12,000 miles and a payload capacity of 15 tons has much more interesting uses than carrying passengers I think. Would make a heck of a cruise missile. yes and no. No - early detected and easily destroyed even by previous generation of anti-missile systems. This is basically why Valkyrie and the likes were scrambled 50 years ago. Yes - quick deployment against countries still not having any meaningful anti-missile defense :) Also, quick jumps above 60mi (space international border) would probably allow to legally fly modern day U-2 style missions over some relatively narrow territories like over Crimea, Cuba, North Korea, etc...
  - 12y ago

48 points by kareemm 12y ago

findjashua 12y ago

I'm assuming this can't be used for flying over land due to sonic boom?

masklinn 12y ago
Depends which land and — most likely — depends who builds it. It's not like the US forbid overland supersonic flight for their military planes (and overland commercial supersonic flight was only banned as the US's sole SST program was cancelled)
- Crito 12y ago
  The US military is typically only allowed to go supersonic over land in the US in certain special areas.
- hollerith 12y ago
  During 54 years of living in 5 different metropolitan areas of the U.S., I've never heard a sonic boom. (I know what one sounds like because they were frequent during a vacation I took in West Germany a long time ago.) The Blue Angels, for example, are not authorized to exceed the speed of sound: http://www.blueangels.navy.mil/show/faq.aspx http://www.blueangels.navy.mil/show/faq.aspx
  - rsync 12y ago
    I lived near colorado springs in the early 80s, as a child, and I can remember on two occasions being (figuratively) knocked out of bed by a sonic boom. Presumably from the Air Force Academy. Only happened those two times the entire time we lived there - presumably someone got in trouble for it...

soperj 12y ago

I've read about this before, and I do think it sounds pretty neat, but a small part of me hopes it doesn't work for putting satellites into space, only because the technology doesn't help us land on other planets.

acchow 12y ago
I disagree. Familiarity with microgravity and the vacuum of space in orbit will make developments in interstellar travel that much cheaper.
- soperj 12y ago
  Cool. Love getting down voted for having an opinion & starting the conversation.
- idlewords 12y ago
  I think we're pretty familiar with vacuum at this point. The obstacle to practical interstellar travel is 99.99999% propulsion, which you don't learn a lot about by endlessly falling in a circle.
  - XorNot 12y ago
    And the obstacle to propulsion is the inability to lift large payloads cheaply enough into orbit to start with. The problem is we can't build big things in LEO. At the moment its that our entire LEO-access infrastructure is woefully underdeveloped.
Zigurd 12y ago
The first few miles are the most expensive.
bjelkeman-again 12y ago
I saw a very good presentation by the CEO of Reaction Engine the other day, where he went through where they are at with the engine (Sabre) and with the vehicle (Skylon). He showed how Skylon could lift an interplanetary vehicle in pieces, just like the International Space station was built from modules. The Skylon/Sabre tech will certainly help us reach other planets, as the first 100 km to orbit is the really expensive part, and Skylon/Sabre addresses that well I think. They need some more development money though.

sp332 12y ago

So they can cool the engine, but what about the heat on the rest of the plane?

icegreentea 12y ago
The SR-71 Blackbird cooled itself through a combination of radiative cooling (hence the black), and using its fuel (that was about to be burned) as a heat sink. Some combination of these techniques (and others) would probably be used.
- idlewords 12y ago
  Here the fuel is already being used as a heat sink to cool the inlet air. Liquid H2 doesn't have that big a heat capacity, you can't use it cool the fuselage and the cabin air and your cocktail and still expect it to keep the engine from melting.
NamTaf 12y ago
That's not the problem. The problem is that hot inlet air means that once you burn your fuel, the air post combustion stage is then too hot and melts things.
- idlewords 12y ago
  It's a huge problem, unless you don't mind a flying oven. In the SR-71, the crew had to wear special cooling suits (presumably these will be available in first class).
  - virtue3 12y ago
    meh, insulated cabin. No big deal. just shitloads more weight and/or space (nasa aero gels would probably be great here). Aka this thing is never going to see commercial flight.
  - NamTaf 12y ago
    What I mean is that from a material standpoint, the engine turbine temperature tends to be the design limiting factor. Yes, there's going to be hot spots on leading edges due to stagnation for example, but you're not burning fuel there to intentionally jack the temperature up.

lubesGordi 12y ago

the video is 2 years old

idlewords 12y ago

We're not going to have Mach 5 commercial air travel for the same reason we don't have Mach 2 or 3 commercial air travel. The economics just don't work. That reason is much more boring than the technical obstacles, which are formidable, fun to try to solve, and kind of beside the point. In that sense, this problem resembles a lot of software engineering. But just to keep this comment from being too depressing, here's one technical gripe: consider that liquid hydrogen is an extremely bulky fuel, even if you don't include the necessary insulation. Notice how nearly the entire volume of the satellite launcher in the diagram consists of hydrogen tank. There's not a lot of room in there for passenger lounges and drink trolleys.

twic 12y ago
> The economics just don't work. Given that you don't know how much this will cost to operate, you can't possibly know that, right? At some point, i think i read a claim that an airliner based on this technology would be able to supply Europe - Australasia trips for about the same price as a business class ticket on a conventional airliner on that route. Passengers currently buy a fair few of those tickets; some might choose to do the trip in two hours instead of twenty-four in exchange for a smaller seat and the loss of a couple of meals.
- idlewords 12y ago
  We know how much the Concorde cost to operate: a zillion shittons (metric) [http://www.concordesst.com/retire/faq_r.html http://www.concordesst.com/retire/faq_r.html] . And that was with proven technology and all the sunk costs behind them. I think that makes a sensible floor for this project, unless you are willing to argue that researching and deploying this completely new technology would somehow cost less.
- jvm 12y ago
  Is there really a tremendous amount of demand on the Australia / Europe segment? If London/NYC wasn't viable for the Concorde (probably the most popular international airline segment), I can't imagine the demand being higher on routes to Sydney. If the fixed costs of a flight are high, it will likely be even more expensive than the Concorde on trans-Atlantic routes.

ufmace 12y ago

Sounds a little odd. I'm not really an expert on this area or anything, but it sounds plausible that if they are able to cool the incoming air stream to that temperature, then they might be able to make the speeds they're claiming. But I have to wonder, not only how they made a heat exchanger capable of cooling the incoming air that fast, but what are they doing with those megawatts of heat that they're taking out of the air? They claimed air temperatures coming out of the heat exchanger of -150, so where are they getting a cooling fluid colder than that to do exchange with?

idlewords 12y ago
The incredibly huge tank of liquid hydrogen not pictured in the diagram. The same one that makes the idea completely unfeasible for commercial transport.

TeMPOraL 12y ago

Nitpick about the title[0], but it's a kind of thing that really irks me. It's "Reaction Engines", not "Reaction engines". It's a proper name of a private limited company, not a class of engines. [0] - at the time of writing this, the title was: "Reaction engines bring us a step closer to Mach5 commercial air travel".

alexvr 12y ago
Based on the grammar following "Reaction engines," it's clear that the OP simply thought the new engine was actually called a "reaction engine" (I'm sure the author would not write "Google bring us closer to autonomous cars")
- TeMPOraL 12y ago
  Well, the article clearly states that Reaction Engines is a rocket company, so it follows that OP must have not read the article very carefully, if at all.
- MaysonL 12y ago
  The Star is a British paper: UK usage would be Reaction Engines bring, and yes the author would write "Google bring...".
kareemm 12y ago
I'm the OP. I'm 90% sure I submitted it as "Reaction Engines" - I was surprised it was "Reaction engines" when I visited the site an hour after submitting. I would've edited it when I revisited the site, but wasn't able to by that point. But, then, it's also entirely possible I submitted it incorrectly.
- dang 12y ago
  No, that was our mistake. Sorry—fixed now.

parley 12y ago

In a previous post (a little over a year ago) about the same engine I posted a link to a video with a Q&A with Elon Musk where he was a bit pessimistic about the idea. I'm not a rocket scientist so I wouldn't know the first thing about it, but if anyone is interested in his (then) opinion it's after 48m55s in the video here: http://www.oxfordmartin.ox.ac.uk/videos/view/211 http://www.oxfordmartin.ox.ac.uk/videos/view/211

XorNot 12y ago
Elon Musk isn't the expert in this area. Practically no one except Reaction Engine employees and some guys at Area 51 are - in the entire world. It's certainly not an easy thing to do, but since they actually do seem to have the heat exchanger figured out then that's kind of a big deal. Burying the lead is the whole commercial air travel angle though. What they're building is a fully reusable, cheap to operate SSTO to low earth orbit.
- bjelkeman-again 12y ago
  ESA did a review of Skylon and the Sabre engine and said "...the SKYLON vehicle can be realised given today's current technology and successful engine development." http://www.reactionengines.co.uk/space_skylon.html http://www.reactionengines.co.uk/space_skylon.html Of course, there needs to be a successful engine development project. Which needs another billion or two to complete according to the CEO/MD of Reaction Engine. (He was a bit more specific than that when I heard him say it, but it is in the ballpark.)

trhway 12y ago

the thermodynamic economics of ram/scram jets at the Mach5+ speeds is almost killed compare to the rocket engines by the fact that oxygen is only 20% of the incoming air, while the whole incoming air needs to be processed through the engine, ie. compressed/(may be cooled interstage)/heated/expelled. Various unavoidable losses on this 80% (nitrogen) of the incoming air eat deeply into end-result efficiency of such engine when compared to a rocket engine.

ChuckMcM 12y ago

The trick is, and it is a trick, to "instantly cool the air". Think about that for a moment. Generally the way most 'air breathing' engines work is that they take air, heat it (which expands it (thanks Boyle!)) and toss it backwards which imparts a forced in the forward direction (thanks Newton!). The difference in temperature between the inlet and exhaust temperature of a jet engine is a component of its efficiency. (see http://en.wikipedia.org/wiki/Jet_engine#Energy_efficiency http://en.wikipedia.org/wiki/Jet_engine#Energy_efficiency for some math :-) But basically if you're suddenly cooling air it gets smaller, which creates a lower pressure, and was used effectively in steam pumps to create the vacuum needed to lift water out of mines. So the Reaction Engines concept takes really hot air that is compressed because it is being pushed out of the way by the air frame, then super cools it which causes it to become much smaller, and then dumps that into the engine. Which then heats it up again and pushed out. If I understand the theory correctly, it takes heat from the air, removes it and puts it into liquid hydrogen (which then becomes vaporous(sp?) hydrogen) and then burns that hydrogen with residual oxygen to put the heat back into the air plus what ever is extra from the hydrogen. What bugs me about it is that it seems to double count the energy in the air rather than single count it. But I'm interested in seeing one of their machines in action. If someone knows whether or not there is a violation of thermodynamics in there I'd like to understand that. That said a mach 5 vehicle with a range of 12,000 miles and a payload capacity of 15 tons has much more interesting uses than carrying passengers I think. Would make a heck of a cruise missile.

trhway 12y ago
>That said a mach 5 vehicle with a range of 12,000 miles and a payload capacity of 15 tons has much more interesting uses than carrying passengers I think. Would make a heck of a cruise missile. yes and no. No - early detected and easily destroyed even by previous generation of anti-missile systems. This is basically why Valkyrie and the likes were scrambled 50 years ago. Yes - quick deployment against countries still not having any meaningful anti-missile defense :) Also, quick jumps above 60mi (space international border) would probably allow to legally fly modern day U-2 style missions over some relatively narrow territories like over Crimea, Cuba, North Korea, etc...
- 12y ago