# gas turbines in supersonic flight **URL:** \ **Category:** Factual Questions\ **Created:** [May 14, 2012, 3:28am UTC](https://boards.straightdope.com/t/gas-turbines-in-supersonic-flight/621837 "2012-05-14T03:28:57Z")\ **Posts on this page:** 5\ **Page:** 2
**Author:** ![jz78817](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jz78817/32/1028_2.png) [@jz78817](https://boards.straightdope.com/u/jz78817)\ **Post date:** [May 20, 2012, 2:35am UTC](https://boards.straightdope.com/t/gas-turbines-in-supersonic-flight/621837/21 "2012-05-20T02:35:06Z")
> [@Hail\_Ants](#): > > No, that’s not really the point I was trying to make, airfoil vs paddle wheel. The point was that in a ducted fan the turbine-ish fan blades are directly generating thrust, similar to a standard propeller. In a true turbo-jet the turbines primarily serve to feed compressed air into the combustion chamber where it’s mixed with fuel, ignited, and thrust is created from this combustion. No, that’s the compressor. The turbine is after the combustor, and it extracts the necessary energy from the expanding hot gases to drive the compressor. The remaining energy is fired out the nozzle as thrust. > **[File:Turbojet operation- axial flow.png](https://en.wikipedia.org/wiki/File:Turbojet_operation-_axial_flow.png)** > >   > \[edit\] > > Derivative works of this file: ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [May 20, 2012, 3:00am UTC](https://boards.straightdope.com/t/gas-turbines-in-supersonic-flight/621837/22 "2012-05-20T03:00:22Z")
All this exciting pedantry aside, what happens on a supersonic jet if the inlet ramp or aerospike malfunctions (or, for the sake of argument, suddenly disappears altogether)? Probably not compressor stall, since the slipstream is delivering air to the front of the compressor at Ludicrous Speed. So…what’s the result? ---
**Author:** ![oliversarmy](https://avatars.discourse-cdn.com/v4/letter/o/eb8c5e/32.png) [@oliversarmy](https://boards.straightdope.com/u/oliversarmy)\ **Post date:** [May 20, 2012, 3:16am UTC](https://boards.straightdope.com/t/gas-turbines-in-supersonic-flight/621837/23 "2012-05-20T03:16:57Z")
Kaboom? ---
**Author:** ![Raguleader](https://avatars.discourse-cdn.com/v4/letter/r/258eb7/32.png) [@Raguleader](https://boards.straightdope.com/u/Raguleader)\ **Post date:** [May 20, 2012, 3:20am UTC](https://boards.straightdope.com/t/gas-turbines-in-supersonic-flight/621837/24 "2012-05-20T03:20:22Z")
And what if the SR-71 is on a tread-_THUNK__thud_ ---
**Author:** ![Gray\_Ghost](https://avatars.discourse-cdn.com/v4/letter/g/c0e974/32.png) [@Gray\_Ghost](https://boards.straightdope.com/u/Gray_Ghost)\ **Post date:** [May 20, 2012, 4:19am UTC](https://boards.straightdope.com/t/gas-turbines-in-supersonic-flight/621837/25 "2012-05-20T04:19:10Z")
> [@Machine\_Elf](#): > > All this exciting pedantry aside, what happens on a supersonic jet if the inlet ramp or aerospike malfunctions (or, for the sake of argument, suddenly disappears altogether)? Probably not compressor stall, since the slipstream is delivering air to the front of the compressor at Ludicrous Speed. > > So…what’s the result? In the case of the [SR-71](http://www.wvi.com/~sr71webmaster/j-58~1.htm), lots of exciting things: > [@](#): > > At Mach 3+ the spike is three feet to the rear of it’s takeoff position, slowing down the incoming airflow, establishing an area of pressure within the nacelle, which is now pushing the engine. This action is so powerful that it accounts for 58 percent of the total thrust, the engine providing only 17 percent, and the ejectors (surrounding the nacelle near the afterburner) is responsible for the remaining 25 percent. Should the shockwave be expelled from the inlet, a condition known as an “Unstart” occurs. **Unstarts have been known to be so violent as to crack the pilots helmet from the severe yaw of the aircraft.** [Emphasis added] If unchecked, the resulting yaw is described by SR-71 pilots as though the nose and tail are trying to swap ends. [Previous page](https://boards.straightdope.com/t/gas-turbines-in-supersonic-flight/621837.md?page=1)