5 ms·

Air Force Reveals Tests of Supposed Record-Setting Scramjet from N. Grumman

70 points by nwrk 7y ago

ChuckMcM 7y ago
This is a pretty neat technical achievement. One of the things that has made it possible has been the ability to much better CFD simulations of the whole system. Rather than test/tail iterate cycle, they can get to a working system that can be refined in a shorter period of time. That said, its hard to beat the SABER engine's use of liquid hydrogen to cool the air coming into the engine and just achieving better thrust. I still find that concept mind blowing.
- drak0n1c 7y ago
  Always good to hear that software has a role in progressing hard technology.
- positr0n 7y ago
  You probably know that using liquid hydrogen to cool engine bells is common in rocketry as well. I found this video fascinating. On one side, the engine is so cold icicles are forming. Centimeters away, the other side is so hot that it would melt pretty much any metal except the most exotic of alloys. The engine is so efficient that all that energy is pointed straight down. None escapes to melt the icicles. https://youtu.be/4eM1mNNdguA?t=89 https://youtu.be/4eM1mNNdguA?t=89 Scott Manley has a good explanation but I can't find the video right now where he mentions it.
  - ChuckMcM 7y ago
    Yes, it keeps the bell of the nozzle from melting off the back of the rocket. And that is a really cool trick, extremely tough to pull off in the original F1 engines of the Saturn V (lots of welds) but easier to do now that you can 3D print the engine. However, the SABRE has a different challenge. Rather than cool metal (Inconel) which is a very good conductor of heat, the SABRE heat exchanger is cooling the air which has gained temperature for becoming compressed by the moving aircraft. Air, for all of its wonderful properties, is not a particularly good heat conductor[1]. Further, since heat transfer by conduction is a function of time in which the two dissimilar temperature materials are in contact, and hyper sonic craft are going very fast, it has to achieve this heat transfer in a literal "blink of an eye." It has been compared to shooting an acetylene torch through it and having a cool breeze come out the other side. Really amazing stuff. [1] This is fortunate as it makes down coats warm rather than cold.
    - inamberclad 7y ago
      Not only that, but it has to not ice up in the process.
  - Retric 7y ago
    That’s not what’s going on in the video. This is a cryogenic test, no part of the engine is hot.
    - positr0n 7y ago
      Sure doesn't seem that way to me. Blue rocket flame is coming out, and the operators talk about "ignition" and percentage thrust and shut down (when all the icicles fly off).
      - Retric 7y ago
        The ice is forming inches below the rocket engine. “The steam is cooled by the cold engine nozzle, condensing and eventually freezing at the nozzle exit to form icicles.” https://www.nasa.gov/mission_pages/constellation/multimedia/cece.html https://www.nasa.gov/mission_pages/constellation/multimedia/... In other words both sides of the base of the nozzle is cold. PS: Though presumably closer it combustion it may still get hot on the inside.
- FlyMoreRockets 7y ago
  Sure it is, oxidizer MIPCC. It's a lot easier/cheaper than SABRE and works when the air thins too much to support combustion.
mikece 7y ago
Is the SR-71 constrained by its engine or airframe? I know I’ve read that if the plane went any faster something would start melting and the plane would be lost but I don’t recall if it was the airframe or the engine.
- starpilot 7y ago
  Presumably both, to a large degree, since it's probably a pretty optimized aircraft. The engine & inlet are designed to compress the air using the shock patterns that develop at certain Mach numbers. Beyond that Mach range, it won't work. Likewise they probably didn't bother designing the airframe to work at speeds in which the engine couldn't.
  - cbanek 7y ago
    The SR-71 is also high altitude, so if there is less air (pressure), that can change things like: how much lift you need or can generate, the outside temperature, how much air can be used by the engine, heating due to air friction, etc.
  - JustSomeNobody 7y ago
    > Presumably both, to a large degree, since it's probably a pretty optimized aircraft. And all that was done without a computer.
- deepnotderp 7y ago
  Both propulsion (scramjet+ramjet TWR, reliability, startup, etc.) and aerodynamic heating are major problems for hypersonic flight.
- dexen 7y ago
  The aircraft was actively cooled[1], so I suppose they could always force a bit more cooling if needed. My guess is on engines - and not necessarily thermal limitation, probably rather inlet speed. Funnily enough, having read the Sled Driver[2], I don't remember any clear explainer whether the engine or the airframe was thermally limited. Perhaps it was there and I forgot by now? [edit] Wikipedia to the rescue, "Maximum flight speed was limited by the temperature of the air entering the engine compressor, which was not certified for temperatures above 800 °F (430 °C)." [3] The inlet air was necessarily heated as side effect of being slowed down to subsonic speeds, necessitated by the nature of the turbine engine. -- [1] by circulating the JP-7 fuel through critical sections, before sending it off to the engines [2] https://www.goodreads.com/book/show/1349004.Sled_Driver https://www.goodreads.com/book/show/1349004.Sled_Driver [3] https://en.wikipedia.org/wiki/Lockheed_SR-71_Blackbird#cite_ref-64 https://en.wikipedia.org/wiki/Lockheed_SR-71_Blackbird#cite_...
beefman 7y ago
> The Air Force recently broke the record for the highest thrust producing air-breathing hypersonic engine the service has ever tested in its history, at least that we know about. Nuclear scramjets achieved 3 times this thrust "record" under similar test conditions more than half a century ago.
- dtparr 7y ago
  Do nuclear scramjets count as air breathing? They don't use atmospheric oxygen for combustion, iirc, which is what I think of when I hear air breathing.
  - DuskStar 7y ago
    They're air breathing in the same sense that electric planes are, I suppose? They use air for propulsion, but not for chemical reactions.
  - deleted 7y ago
    [deleted]
- ian0 7y ago
  Project Pluto belongs [0] in the "what could possibly go wrong" bin: >> The SLAM, as proposed, would carry a payload of many nuclear weapons to be dropped on multiple targets, making the cruise missile into an unmanned bomber. After delivering all its warheads, the missile could then spend weeks flying over populated areas at low altitudes, causing tremendous ground damage with its shock wave and fallout. When it finally lost enough power to fly, and crash-landed, the engine would have a good chance of spewing deadly radiation for months to come. [0] https://en.wikipedia.org/wiki/Project_Pluto https://en.wikipedia.org/wiki/Project_Pluto
  - scottlocklin 7y ago
    Thank god we have MSNBC to keep the rooskie from sapping and impurifying our precious bodily fluids. https://thediplomat.com/2019/02/russia-conducts-test-of-nuclear-powered-cruise-missile/ https://thediplomat.com/2019/02/russia-conducts-test-of-nucl...
throwaway3627 7y ago
I remember scramjets in Popular Mechanics 30 years ago, but nothing seemed to materialize. Off-topic to scramjets but potentially military-related: Making a big stretch by assuming the "white Tic-Tac" isn't an elaborate hoax to get adversaries to overspend on propulsion technologies and/or troll the public, what type of propulsion could allow it to accelerate so quickly? Casimir effect thruster?
- kevin_thibedeau 7y ago
  Gamma ray to the visual cortex.
  - sgt101 7y ago
    or bits into the video camera and hud.
- beautifulfreak 7y ago
  They reported seeing the Tic Tac descend from 20,000 feet in just an instant, stopping at the surface of the ocean. This and other reports suggest a propulsion system that alters spacetime and mass, so that there's no inertia. We Earthmen have no such technology.
- y04nn 7y ago
  I don't really believe that it is achievable, but the US Navy published some intriguing patents: * Craft using an inertial mass reduction device [1] * High frequency gravitational wave generator [2] * Piezoelectricity-induced Room Temperature Superconductor [3] [1] https://patents.google.com/patent/US10144532B2 https://patents.google.com/patent/US10144532B2 [2] https://patents.google.com/patent/US10322827B2 https://patents.google.com/patent/US10322827B2 [3] https://patents.google.com/patent/US20190058105A1 https://patents.google.com/patent/US20190058105A1
fdavison 7y ago
Johnny Armstrong, the Hypersonics Combined Test Force Chief Engineer for Air Force, until his retirement in 2012, passed away just last week. He worked in hypersonics from the X-15 to the X-51 Waverider. https://www.edwards.af.mil/News/Article/1922993/team-edwards-loses-one-of-its-own-as-hypersonics-pioneer-johnny-g-armstrong-dies/ https://www.edwards.af.mil/News/Article/1922993/team-edwards... https://vimeo.com/37453969 https://vimeo.com/37453969
killjoywashere 7y ago
Here's a picture of the test apparatus. This barely resembles a typical wind tunnel. Anyone who know these things care to provide a illustrated guide to thing? https://media.defense.gov/2019/Aug/05/2002166487/-1/-1/0/190220-F-IL571-080.JPG https://media.defense.gov/2019/Aug/05/2002166487/-1/-1/0/190...
- namirez 7y ago
  Not sure about the details of this picture, but hypersonic wind tunnels look very different than subsonic wind tunnels. The cross section of a hypersonic tunnel is usually small and there are not many moving parts. The high Mach number is achieved by discharging compressed air into the tunnel. You can find more info about this specific tunnel on wikipedia [1]. [1] https://en.wikipedia.org/wiki/Aerodynamic_and_Propulsion_Test_Unit https://en.wikipedia.org/wiki/Aerodynamic_and_Propulsion_Tes...
  - NamTaf 7y ago
    I can't add much to this, besides the point that in my experience with expansion tunnels [1][2] from my time at uni, they are very short-term test facilities, lasting for fractions of a second. They work by compressing a big vessel of air with a piston, rupturing a diaphragm, and then blowing that highly compressed air through a expansion nozzle (which, unlike subsonic flow, accelerates the flow velocity through the nozzle) before passing it over the test piece. I'm not familiar with the APTU, but it would not surprise me if this is a similar concept, wherein it delivers a short-term high-velocity flow across a test object. I think the main difference is it heats with a combustion air heater, rather than pressurising with a big slug. In any case, because it's quick and requires a small cross-sectional area, much of the surrounds of the machine are all sensors to measure everything, since you don't want to have to do it over and over again. I think that is much of what can be seen in the photo of the APTU. [1] https://en.wikipedia.org/wiki/Expansion_tunnel https://en.wikipedia.org/wiki/Expansion_tunnel [2] http://hypersonics.mechmining.uq.edu.au/facilities http://hypersonics.mechmining.uq.edu.au/facilities (specifically X2 and X3)
mrtri 7y ago
hypersonic airplanes prove earth is flat. if it flies at 2000mph it gonna get 128 miles up higher after 30 minutes on the ball. (earth radius 3,959 miles) it get superheated at these speed, so they dont use the flaps to dip the nose down to fly over the curve https://youtu.be/OC417KBJNEg?t=46s https://youtu.be/OC417KBJNEg?t=46s just ask any pilot, no one will know how much earth curves per mile in front of them.

70 points by nwrk 7y ago

This is a pretty neat technical achievement. One of the things that has made it possible has been the ability to much better CFD simulations of the whole system. Rather than test/tail iterate cycle, they can get to a working system that can be refined in a shorter period of time. That said, its hard to beat the SABER engine's use of liquid hydrogen to cool the air coming into the engine and just achieving better thrust. I still find that concept mind blowing.

drak0n1c 7y ago
Always good to hear that software has a role in progressing hard technology.
positr0n 7y ago
You probably know that using liquid hydrogen to cool engine bells is common in rocketry as well. I found this video fascinating. On one side, the engine is so cold icicles are forming. Centimeters away, the other side is so hot that it would melt pretty much any metal except the most exotic of alloys. The engine is so efficient that all that energy is pointed straight down. None escapes to melt the icicles. https://youtu.be/4eM1mNNdguA?t=89 https://youtu.be/4eM1mNNdguA?t=89 Scott Manley has a good explanation but I can't find the video right now where he mentions it.
- ChuckMcM 7y ago
  Yes, it keeps the bell of the nozzle from melting off the back of the rocket. And that is a really cool trick, extremely tough to pull off in the original F1 engines of the Saturn V (lots of welds) but easier to do now that you can 3D print the engine. However, the SABRE has a different challenge. Rather than cool metal (Inconel) which is a very good conductor of heat, the SABRE heat exchanger is cooling the air which has gained temperature for becoming compressed by the moving aircraft. Air, for all of its wonderful properties, is not a particularly good heat conductor[1]. Further, since heat transfer by conduction is a function of time in which the two dissimilar temperature materials are in contact, and hyper sonic craft are going very fast, it has to achieve this heat transfer in a literal "blink of an eye." It has been compared to shooting an acetylene torch through it and having a cool breeze come out the other side. Really amazing stuff. [1] This is fortunate as it makes down coats warm rather than cold.
  - inamberclad 7y ago
    Not only that, but it has to not ice up in the process.
- Retric 7y ago
  That’s not what’s going on in the video. This is a cryogenic test, no part of the engine is hot.
  - positr0n 7y ago
    Sure doesn't seem that way to me. Blue rocket flame is coming out, and the operators talk about "ignition" and percentage thrust and shut down (when all the icicles fly off).
    - Retric 7y ago
      The ice is forming inches below the rocket engine. “The steam is cooled by the cold engine nozzle, condensing and eventually freezing at the nozzle exit to form icicles.” https://www.nasa.gov/mission_pages/constellation/multimedia/cece.html https://www.nasa.gov/mission_pages/constellation/multimedia/... In other words both sides of the base of the nozzle is cold. PS: Though presumably closer it combustion it may still get hot on the inside.
FlyMoreRockets 7y ago
Sure it is, oxidizer MIPCC. It's a lot easier/cheaper than SABRE and works when the air thins too much to support combustion.

mikece 7y ago

Is the SR-71 constrained by its engine or airframe? I know I’ve read that if the plane went any faster something would start melting and the plane would be lost but I don’t recall if it was the airframe or the engine.

starpilot 7y ago
Presumably both, to a large degree, since it's probably a pretty optimized aircraft. The engine & inlet are designed to compress the air using the shock patterns that develop at certain Mach numbers. Beyond that Mach range, it won't work. Likewise they probably didn't bother designing the airframe to work at speeds in which the engine couldn't.
- cbanek 7y ago
  The SR-71 is also high altitude, so if there is less air (pressure), that can change things like: how much lift you need or can generate, the outside temperature, how much air can be used by the engine, heating due to air friction, etc.
- JustSomeNobody 7y ago
  > Presumably both, to a large degree, since it's probably a pretty optimized aircraft. And all that was done without a computer.
deepnotderp 7y ago
Both propulsion (scramjet+ramjet TWR, reliability, startup, etc.) and aerodynamic heating are major problems for hypersonic flight.
dexen 7y ago
The aircraft was actively cooled[1], so I suppose they could always force a bit more cooling if needed. My guess is on engines - and not necessarily thermal limitation, probably rather inlet speed. Funnily enough, having read the Sled Driver[2], I don't remember any clear explainer whether the engine or the airframe was thermally limited. Perhaps it was there and I forgot by now? [edit] Wikipedia to the rescue, "Maximum flight speed was limited by the temperature of the air entering the engine compressor, which was not certified for temperatures above 800 °F (430 °C)." [3] The inlet air was necessarily heated as side effect of being slowed down to subsonic speeds, necessitated by the nature of the turbine engine. -- [1] by circulating the JP-7 fuel through critical sections, before sending it off to the engines [2] https://www.goodreads.com/book/show/1349004.Sled_Driver https://www.goodreads.com/book/show/1349004.Sled_Driver [3] https://en.wikipedia.org/wiki/Lockheed_SR-71_Blackbird#cite_ref-64 https://en.wikipedia.org/wiki/Lockheed_SR-71_Blackbird#cite_...

beefman 7y ago

> The Air Force recently broke the record for the highest thrust producing air-breathing hypersonic engine the service has ever tested in its history, at least that we know about. Nuclear scramjets achieved 3 times this thrust "record" under similar test conditions more than half a century ago.

dtparr 7y ago
Do nuclear scramjets count as air breathing? They don't use atmospheric oxygen for combustion, iirc, which is what I think of when I hear air breathing.
- DuskStar 7y ago
  They're air breathing in the same sense that electric planes are, I suppose? They use air for propulsion, but not for chemical reactions.
- deleted 7y ago
  [deleted]
ian0 7y ago
Project Pluto belongs [0] in the "what could possibly go wrong" bin: >> The SLAM, as proposed, would carry a payload of many nuclear weapons to be dropped on multiple targets, making the cruise missile into an unmanned bomber. After delivering all its warheads, the missile could then spend weeks flying over populated areas at low altitudes, causing tremendous ground damage with its shock wave and fallout. When it finally lost enough power to fly, and crash-landed, the engine would have a good chance of spewing deadly radiation for months to come. [0] https://en.wikipedia.org/wiki/Project_Pluto https://en.wikipedia.org/wiki/Project_Pluto
- scottlocklin 7y ago
  Thank god we have MSNBC to keep the rooskie from sapping and impurifying our precious bodily fluids. https://thediplomat.com/2019/02/russia-conducts-test-of-nuclear-powered-cruise-missile/ https://thediplomat.com/2019/02/russia-conducts-test-of-nucl...

throwaway3627 7y ago

I remember scramjets in Popular Mechanics 30 years ago, but nothing seemed to materialize. Off-topic to scramjets but potentially military-related: Making a big stretch by assuming the "white Tic-Tac" isn't an elaborate hoax to get adversaries to overspend on propulsion technologies and/or troll the public, what type of propulsion could allow it to accelerate so quickly? Casimir effect thruster?

kevin_thibedeau 7y ago
Gamma ray to the visual cortex.
- sgt101 7y ago
  or bits into the video camera and hud.
beautifulfreak 7y ago
They reported seeing the Tic Tac descend from 20,000 feet in just an instant, stopping at the surface of the ocean. This and other reports suggest a propulsion system that alters spacetime and mass, so that there's no inertia. We Earthmen have no such technology.
y04nn 7y ago
I don't really believe that it is achievable, but the US Navy published some intriguing patents: * Craft using an inertial mass reduction device [1] * High frequency gravitational wave generator [2] * Piezoelectricity-induced Room Temperature Superconductor [3] [1] https://patents.google.com/patent/US10144532B2 https://patents.google.com/patent/US10144532B2 [2] https://patents.google.com/patent/US10322827B2 https://patents.google.com/patent/US10322827B2 [3] https://patents.google.com/patent/US20190058105A1 https://patents.google.com/patent/US20190058105A1

fdavison 7y ago

Johnny Armstrong, the Hypersonics Combined Test Force Chief Engineer for Air Force, until his retirement in 2012, passed away just last week. He worked in hypersonics from the X-15 to the X-51 Waverider. https://www.edwards.af.mil/News/Article/1922993/team-edwards-loses-one-of-its-own-as-hypersonics-pioneer-johnny-g-armstrong-dies/ https://www.edwards.af.mil/News/Article/1922993/team-edwards... https://vimeo.com/37453969 https://vimeo.com/37453969

killjoywashere 7y ago

Here's a picture of the test apparatus. This barely resembles a typical wind tunnel. Anyone who know these things care to provide a illustrated guide to thing? https://media.defense.gov/2019/Aug/05/2002166487/-1/-1/0/190220-F-IL571-080.JPG https://media.defense.gov/2019/Aug/05/2002166487/-1/-1/0/190...

namirez 7y ago
Not sure about the details of this picture, but hypersonic wind tunnels look very different than subsonic wind tunnels. The cross section of a hypersonic tunnel is usually small and there are not many moving parts. The high Mach number is achieved by discharging compressed air into the tunnel. You can find more info about this specific tunnel on wikipedia [1]. [1] https://en.wikipedia.org/wiki/Aerodynamic_and_Propulsion_Test_Unit https://en.wikipedia.org/wiki/Aerodynamic_and_Propulsion_Tes...
- NamTaf 7y ago
  I can't add much to this, besides the point that in my experience with expansion tunnels [1][2] from my time at uni, they are very short-term test facilities, lasting for fractions of a second. They work by compressing a big vessel of air with a piston, rupturing a diaphragm, and then blowing that highly compressed air through a expansion nozzle (which, unlike subsonic flow, accelerates the flow velocity through the nozzle) before passing it over the test piece. I'm not familiar with the APTU, but it would not surprise me if this is a similar concept, wherein it delivers a short-term high-velocity flow across a test object. I think the main difference is it heats with a combustion air heater, rather than pressurising with a big slug. In any case, because it's quick and requires a small cross-sectional area, much of the surrounds of the machine are all sensors to measure everything, since you don't want to have to do it over and over again. I think that is much of what can be seen in the photo of the APTU. [1] https://en.wikipedia.org/wiki/Expansion_tunnel https://en.wikipedia.org/wiki/Expansion_tunnel [2] http://hypersonics.mechmining.uq.edu.au/facilities http://hypersonics.mechmining.uq.edu.au/facilities (specifically X2 and X3)

mrtri 7y ago

hypersonic airplanes prove earth is flat. if it flies at 2000mph it gonna get 128 miles up higher after 30 minutes on the ball. (earth radius 3,959 miles) it get superheated at these speed, so they dont use the flaps to dip the nose down to fly over the curve https://youtu.be/OC417KBJNEg?t=46s https://youtu.be/OC417KBJNEg?t=46s just ask any pilot, no one will know how much earth curves per mile in front of them.