Hermeus hypersonic aircraft project

@F119Doctor In the SABRE concept(s) the helium is in a closed loop. It works due to also having the large volume resevoir of LH2 to reject the heat into. Effectively its somewhat allowing you to decouple precooler flow rate and fuel flow rate. Whereas if you use LH2 for both then the fuel consumption rate is very high.
 
Thanks for the schematic, now I understand. Basically using the helium as the working fluid for a heat pump system moving heat from the inlet to the LH2 fuel, which is the ultimate heat sink with the waste heat going out the exhaust. I still don’t really see how this decouples the system from the LH2 fuel flow, since a lower LH2 flow rate means less heat rejection, raising the inlet temperature, etc.

The other issue I see is using the same nozzle for the rocket combustion chamber and the air breathing combustor. Rockets chamber pressure tends to be way higher than an air breathing combustor, even with the ram recovery and air compression system. Using both is likely to have the rocket exhaust very under expanded (inefficient) to prevent operating the air breathing system with an over expanded nozzle condition (separated unstable flow, poor efficiency)

Hopefully the SABRE group knows more than I do!
 
Sabre uses the He loop because too much hydrogen was diffusing through the heat exchanger tube walls. With H2 massive flammability range it was considered a fire/explosion risk downstream with the elevated T and P.

I remember once being told that LACE had suffered likewise in its brief operation and was one of the “to be solved” problems at cancellation. Also LACE’s individual engine were all very short due to the icing and that had saved it from going bang.
 
F119Doctor said:
Thanks for the schematic, now I understand. Basically using the helium as the working fluid for a heat pump system moving heat from the inlet to the LH2 fuel, which is the ultimate heat sink with the waste heat going out the exhaust. I still don’t really see how this decouples the system from the LH2 fuel flow, since a lower LH2 flow rate means less heat rejection, raising the inlet temperature, etc.
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It means less heat rejection from the He in the LH2 pump heat exchanger, but it also means less heat sink into the He in the post-pre-burner heat exchanger. :)

F119Doctor said:
The other issue I see is using the same nozzle for the rocket combustion chamber and the air breathing combustor. Rockets chamber pressure tends to be way higher than an air breathing combustor, even with the ram recovery and air compression system. Using both is likely to have the rocket exhaust very under expanded (inefficient) to prevent operating the air breathing system with an over expanded nozzle condition (separated unstable flow, poor efficiency)

Hopefully the SABRE group knows more than I do!
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The combustors aren't shown in great detail in that diagram. There are two ways out, ramjet burners and LOx-supplied rocket burners at higher speeds, with presumably some partial flow through each in the transition phase.

1716283272573.png
 
Just thought about something... if they use MIPCC, they will fly to Mach 5. Is that hypersonics ?
 
Archibald said:
A quarter horse ? does it only have one leg ?

...

(runs for cover).
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Heh.

en.wikipedia.org

American Quarter Horse - Wikipedia

en.wikipedia.org en.wikipedia.org
The American Quarter Horse, or Quarter Horse, is an American breed of horse that excels at sprinting short distances. Its name is derived from its ability to outrun other horse breeds in races of 1⁄4 mi (0.40 km) or less;
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I'd assume that if they get to something closer to a full-sized aircraft they might call it a Thoroughbred.
 
Pre-coolers are great, reducing the inlet temperature of a jet engine can greatly increase the available performance.

The problem is always - where does the waste heat from the pre-cooler go? LH2 is always a go to heat sink, but it has storage and handling problems. You can move the heat and try to shed it to the free stream, but that is hot also. Trying to use a heat pump to move the heat is a complicated….

Sometimes I wonder if old fashioned inlet water injection would be just as effective and simpler…..
 
But why would they do otherwise? Their pre-cooling needs are only transitional. If they lighten the vehicle enough, with that F-100, the time to get from Mach2,5 to Mach3+ to switch to the ramjet might be very short. Spraying should be enough.
 
Hermeus has selected Cecil Airport in Jacksonville, Florida for its hypersonic engine test facility. Named HEAT (High Enthalpy Air-Breathing Test Facility), this facility will be Hermeus’ largest and most technologically advanced test site to date and become a national asset for hypersonic testing. The site will also be the initial base for Hermeus’ high-Mach flight test capabilities starting in 2026, expanding cadence and affordability of the nation’s flight test infrastructure.

We announced our plans for the new facility at a groundbreaking ceremony at Cecil Airport in Jacksonville. Hermeus executives and employees were joined by U.S. Congressman Aaron Bean (FL- 04), U.S. Congressman John Rutherford (FL-05), State Sen. Clay Yarborough (R-Jacksonville), Mayor Donna Deegan, Florida Department of Commerce officials, JAXUSA officials, and other community leaders.

The HEAT facility will provide continuous high flow rate, high enthalpy and low-pressure conditions required for high-supersonic and low-hypersonic flight modeling. This capability will make the facility an important asset to more effectively test and field various hypersonic technologies – not only for Hermeus but also for the Department of Defense and its commercial partners.

Hermeus will test a variety of engines and propulsion subsystems at HEAT – from the Pratt & Whitney F100 engine to Hermeus’ proprietary hypersonic Chimera engine. The facility will be built in phases with initial sea-level static engine tests starting before the end of 2024. Future phases of the facility will introduce continuous high-Mach vitiated air flow to simulate more flight-like high-Mach testing conditions on the ground.
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View: https://www.youtube.com/watch?v=0rGZoFqqi-k
 
From P&W:

1726585501918


www.rtx.com

After 50 years, the F100 is going hypersonic

It’s sleek and shimmering, gliding through sun-tinted clouds. It’s moving at nearly four times the speed of sound – faster than the famous SR-71 Blackbird, which set the airspeed record some 50 years ago.Its name is Quarterhorse, its mission is to be the world’s first high-Mach autonomous...
www.rtx.com www.rtx.com
 

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