Hermeus hypersonic plane

[Asteroza]

So yet another supersonic startup decloaked. Apparently aiming for a hypersonic aircraft. Apparently got VC funding based on the strength of their hypersonic propulsion concept, which is unfortunately not disclosed.

https://www.hermeus.com/

Notable that the founders are ex-Generation GO members, which is part of the stable of SEI startups, and it seems like they bailed out after the X-60A announcement. Ordinarily with the hypersonic talk, I would have expected Dr. Olds of SEI to be an advisor, but he's notably absent...

[jstrotha0975]

Great. Another hypersonic plane that's only 10 years away for the next 40 years.

[john smith 19]

Great. Another hypersonic plane that's only 10 years away for the next 40 years.

If you're lucky.

No mention of the engine.

If SEI is involved we will almost certainly find (surprise surprise) that some kind of SCramjet is essential to make this thing work. 

[CameronD]

Great. Another hypersonic plane that's only 10 years away for the next 40 years.

If you're lucky.

No mention of the engine.

If SEI is involved we will almost certainly find (surprise surprise) that some kind of SCramjet is essential to make this thing work. 

In some rare spare time yesterday I happened upon a Youtube rendering of a TV programme about the failure of the Boeing SST programme way back when:



It seems the most insurmountable hurdles back then were (a) the cost of the unobtainium skin required for sustained flight of such a large vehicle much faster than M2 and (b) the furore over sonic booms - which eventually grounded the Concorde also.  AFAIK, both remain hurdles to this day.

In comparison to the other show-stoppers on this one, the engines aren't a problem.

[Archibald]

I once red that paper about the LAPCAT derived from Skylon. The sonic boom remain such a problem, to go from Europe to australia they had to create a very "imaginative" corridor not to overfly landmasses. This instantly killed the concept, IMHO.

https://en.wikipedia.org/wiki/LAPCAT

If we ever want ultrafast passenger transportation someday, then it will be through rockets and suborbital, ballistics hops - not through airbreathers and hypersonics.  Elon understood this pretty well.

note that a 0.85 propellant mass fraction, kerosene / H2O2 rocketplane, with turbofans, rockets, and nothing else, would have a top speed of 6 km/s, plenty enough to make a 5000 mile ballistic hop with 100 passengers.
Fly out of an ordinary airport on the turbofans, quietly, climb to 55000 ft, mach 0.95 and then light the rocket. Boom, suborbital hop, land at another airport on the turbofans.

It is also possible to "cheat" ballistics to get a longer range through ricochet trajectories - see the works of Preston H. Carter, the father of Hypersoar. He reworked Sanger skip-glide concept with modern tools and found it could work, although at a smaller scale.
Also this https://isulibrary.isunet.edu/doc_num.php?explnum_id=95

[john smith 19]

It seems the most insurmountable hurdles back then were (a) the cost of the unobtainium skin required for sustained flight of such a large vehicle much faster than M2 and

And you'd be wrong. Watch the programme. What killed the Boeing design was it's weight kept going up, partly due to the very complex (and heavy, and probably unreliable) all moving swing wing. Looked very cool on the presentations, actually a massive PITA to design and mfg.

Titanium was available but only Lockheed had the skills (inside the APD who built the SR71. And that's where they stayed, along with the understanding of how to build a M3 aircraft that didn't need variable geometry). OTOH North American had built a M3 aircraft 10x bigger than the SR71 (the XB70) out of stainless steel, because it was expected you'd need to build them by the 100, not the 10. While the XB70 was a bad idea as a bomber as a basis design for an SST it would have been quite reasonable.

(b) the furore over sonic booms - which eventually grounded the Concorde also.  AFAIK, both remain hurdles to this day.


In comparison to the other show-stoppers on this one, the engines aren't a problem.

What grounded the Concorde was the Air France crash that killed everyone on board.  Prior to that the design had flown for 30 years with a perfect safety record.

The problem with takeoff noise was the generation of aircraft Concorde was designed to compete with were turbojets. This was around the time of the shift to turbofans. It was expected that the engine and fuselage  improvements the makers wanted to introduce for the 17th copy (they'd worked out how to eliminate needing the afterburners. Concorde was a "supercruise" aircraft for 30 years without anyone thinking how astonishing that was) would have substantially reduced all noise.

At M5+ both the engines and the skin are problems. Modern M2+ aircraft (even the old F111) are actually low bypass ratio turbofans, not pure turbojets (like those of Concorde and the XB70). The fan blades at the front of the engine can handle around M2.2 airflow but not much above. Since it's likely to be a small production run you can't justify a custom engine just for this application. So at M5+ engines are a problem. AFAIK the lightest SCramjet had a T/W ratio of 2:1. The J58's on the SR71 (mid 50's jet engine tech) were about 5.5 with the nacelle doubling the weight (but absolutely crucial for M3.3 cruise). BTW keep in mind the SR71 SOP was to take off with just enough fuel to get to the tanker and on-load most  of it's fuel.  IOW it's actually a 2 plane system. Acceptable in a military context but no airline will put up with such a system.

So yes, at M5+ cruise the engines are going to be a problem.

M5+ is described as "continuous re-entry." So for hypersonic cruise it's very tough.

Sonic boom control might be the easy part of the problem to solve.

The American SST programme is something of a model of how not to innovate. The lesson was repeated (with the same results) for the X-33 programme. Different players, same failure. 

[john smith 19]

I once red that paper about the LAPCAT derived from Skylon. The sonic boom remain such a problem, to go from Europe to australia they had to create a very "imaginative" corridor not to overfly landmasses. This instantly killed the concept, IMHO.

Unless you have a very efficient engine design. If you have the range you can still do the trip in a reasonable time.

BTW REL's design was the slow vehicle. The DLR proposed a Kerosene SCramjet that couldn't make the range target.

If we ever want ultrafast passenger transportation someday, then it will be through rockets and suborbital, ballistics hops - not through airbreathers and hypersonics.  Elon understood this pretty well.

That also needs an "IMHO".

note that a 0.85 propellant mass fraction, kerosene / H2O2 rocketplane, with turbofans, rockets, and nothing else, would have a top speed of 6 km/s, plenty enough to make a 5000 mile ballistic hop with 100 passengers.
Fly out of an ordinary airport on the turbofans, quietly, climb to 55000 ft, mach 0.95 and then light the rocket. Boom, suborbital hop, land at another airport on the turbofans.

You might like to look up the mass fractions of actual aircraft to find out how tough that is, starting with Concorde and the SR71

[Archibald]

I checked X-33, shuttle buran orbiters, skylon mass fractions, thanks: all of them 0.80 or more.  Your beloved Skylon is above 0.80 too.

Efficient engine or not, NOT overflying landmasses (because no solving the sonic boom)  is NOT viable. Way too much constraining. How do you reach Beijing Moscow Frankfurt Berlin without blasting everybody ear drums and windows ?

 it is you that is wrong. Long duration hypersonic flight was and still remains a huge tricky thing. Kinetic heating is just horrible. Plus the awful sonic boom even at 80 000 ft or higher.

Boeing perfectly knew about titanium. They actually met Soviet engineers in Paris for further  learning ( source Air Force space magazine) Once the L2000 rejected   and Tristar underway, Lockheed and NASA ran the YF-12 fleet and some SR-71s right from 1970 to gather data.
Finally, the final 2707-300 design which ditched the VG was far better. Range was near 4000 miles, better than Concorde.
Concorde repeatedly blew tyres that smashed the tanks and intakes the undercarriage being ill placed. Despite Michelin best efforts it remained an unresolved danger (think sts-27 sts-107 foam losses) that finally doomed the aircraft.

[Star One]

Thread link cross-posted into the existing hypersonic and flight thread.

https://forum.nasaspaceflight.com/index.php?topic=37698.msg1381522#msg1381522

[john smith 19]

I checked X-33, shuttle buran orbiters, skylon mass fractions, thanks: all of them 0.80 or more.  Your beloved Skylon is above 0.80 too.

Perhaps you should read what I wrote again. Slowly.
The mass fraction is always going to be tough. SABRE is what makes it possible.

Efficient engine or not, NOT overflying landmasses (because no solving the sonic boom)  is NOT viable. Way too much constraining. How do you reach Beijing Moscow Frankfurt Berlin without blasting everybody ear drums and windows ?

The EU accepted REL's strategy so they thought it viable enough to fund REL for the LAPCAT II programme.
This is the relevant design as it's a M5 plane we're talking about. Still no word of how Hermeus plans to solve this problem. 

it is you that is wrong. Long duration hypersonic flight was and still remains a huge tricky thing. Kinetic heating is just horrible. Plus the awful sonic boom even at 80 000 ft or higher.

As I've noted before "continuous reentry" How these guys propose to solve the problem other than "We'll build a really cool aircraft" still remains a blank sheet of paper. 

Boeing perfectly knew about titanium. They actually met Soviet engineers in Paris for further  learning ( source Air Force space magazine) Once the L2000 rejected   and Tristar underway, Lockheed and NASA ran the YF-12 fleet and some SR-71s right from 1970 to gather data.

Knowing about what you can do with a few sq ft of alloy is rather different to building nearly a whole aircraft out of it. The classic stories are that marking the alloy with a felt tip pen ate through the alloy, while Chrome Vanadium tools had to be pickled to remove one of the elements that also lead to Titanium failure. These are the lessons you learn when you work alloys for  the first time on a large scale. 

Finally, the final 2707-300 design which ditched the VG was far better. Range was near 4000 miles, better than Concorde.

And had it been the design they started with it might have gotten built. 

One of the key elements that made Concorde possible was the (very) subtle shape of its wings. The chines on the SR71 did something similar (and APD certainly understood how important they were). It allowed a fixed wing with adequate performance across the whole operating speed range. Even the Soviets, when they stole the design, did not realize this. It was only when they tried to build the design they realized they didn't know enough and had to resort to canards.

Concorde repeatedly blew tyres that smashed the tanks and intakes the undercarriage being ill placed. Despite Michelin best efforts it remained an unresolved danger (think sts-27 sts-107 foam losses) that finally doomed the aircraft.

Until Air France took off with a massive overload of both fuel and passengers and managed to kill them all. 

Those facts turned an unfortunate situation into a catastrophe. 

However none of this adds to my knowledge of how Hermeus plans to solve the design problem, either in materials or engine tech.

Other than demonstrating that M5 flight is harder than M2+ is there anything you know about their design?

[john smith 19]

Yes it's necro but they have caught the eye of USAF section that operates the presidents flight.

[libra]

Great. Another hypersonic plane that's only 10 years away for the next 40 years.

If you're lucky.

No mention of the engine.

If SEI is involved we will almost certainly find (surprise surprise) that some kind of SCramjet is essential to make this thing work. 

In some rare spare time yesterday I happened upon a Youtube rendering of a TV programme about the failure of the Boeing SST programme way back when:



It seems the most insurmountable hurdles back then were (a) the cost of the unobtainium skin required for sustained flight of such a large vehicle much faster than M2 and (b) the furore over sonic booms - which eventually grounded the Concorde also.  AFAIK, both remain hurdles to this day.

In comparison to the other show-stoppers on this one, the engines aren't a problem.

Well, Boeing SST - 2707-300 after 1969 - was to be build of titanium. Building Lockheed A-12 family out of that stuff was already extremely difficult.

Well in order to pack 250 passengers the 2707-300 was to be extremely long - 300 ft. It would be even heavier than the XB-70 Valkyrie (which was build of stainless steel, incidentally).

 In the end the expense and flexibility issues just killed the beast.

See attached document for more details.

[john smith 19]

Well, Boeing SST - 2707-300 after 1969 - was to be build of titanium. Building Lockheed A-12 family out of that stuff was already extremely difficult.

Well in order to pack 250 passengers the 2707-300 was to be extremely long - 300 ft. It would be even heavier than the XB-70 Valkyrie (which was build of stainless steel, incidentally).

 In the end the expense and flexibility issues just killed the beast.

See attached document for more details.

A bunch of things killed it. Staring with Congress deciding to cut funding.  Boeing scrapping their swing wing design (very cool and very complex and heavy) and basically replacing it with the Lockheed approach (more conservative and frankly more doable) cost a lot of money.

Personally reading that attachment suggests they didn't really have a deep grasp of just how much heat they were going to deal with.

However this is OT for the thread title.

Hermeus benefits from knowing all this already, and the 5 decades improvement in modelling.

Just a reminder that the heating levels of M5 have been referred to as being like continuous  reentry. What can work for a 15 min decent is unlikely to prove workable for hours of flight.

[ncb1397]

Just a reminder that the heating levels of M5 have been referred to as being like continuous  reentry. What can work for a 15 decent is unlikely to prove workable for hours of flight.

You think this is going to run for hours? At Mach 5, New York to London is like 1 hour. What do you think the range is going to be? The example they give on their website is new york to paris, so I guess that is a bit longer. But I think they would be going slower over land.

edit: The website says 4600 miles at 3300 mph. That is 1.39 hours.

[RonM]

Hermeus' range is better than Concorde and that would open up more options. Concorde flew into Atlanta once to show off, but the FAA denied a London to Atlanta route because they were concerned about fuel reserves. Hermeus Corporation is based in Atlanta, so they'll keep additional Atlantic routes in mind.

[john smith 19]

Hermeus' range is better than Concorde and that would open up more options. Concorde flew into Atlanta once to show off, but the FAA denied a London to Atlanta route because they were concerned about fuel reserves. Hermeus Corporation is based in Atlanta, so they'll keep additional Atlantic routes in mind.

Wrong tense.

Hermeus has a planned range of 4000nm, which is better than Concorde

What it ends up being, if it gets built, is anyone's guess. 

[Robotbeat]

A valid approach would be to insulate everything and use water to keep everything cool.

[john smith 19]

A valid approach would be to insulate everything and use water to keep everything cool.

The "Wet wall" was proposed for the X20 but only for the pilot compartment. "Sweat" cooling systems are fixed duration designs. BTW at the stated range of 4000nm (1nm being 1852m and M1 being 340ms) that's 2 hrs 1 min and 2 secs of flight.

Given the considerable scepticism when Virgin Galactic announced they are building an M3 aircraft of this size I'll just cross post some comments on what M3 designs face.

Good Luck Branson, you need it !

This will be fun to see how this project will struggle with various problem
first design, construction, if R&R is able to build the needed engines
next to that finance issue and high operation cost

Virgin Galactic will have hell of with Fuselage to endure the heat during flight.
For Comparison

SR-71 skin temperature during Mach 3 +316°C or 600 F° airframe active cooled
Concorde skin temperature during Mach 2 +127°C or 261 °F

Concorde fuselage expand 300mm during flight
SR-71 Titanium fuselage expand 1016mm during flight

And this is for a company that has actually built vehicles of the kind of size and designed to carry passengers, with an engine partner (Rolls Royce) who knows quite a lot about engines for M2+ aircraft.

At M5 I think we can comfortably multiply those issues.

At M3 you have 2 known models of crewed aircraft design and construction (the XB70 in SS honeycomb being the other) you could "borrow" if you didn't want do come up with your own approach.

At M5 that narrows to just the X15. It would be interesting to see how much the X15 would have had to have growth to do a runway takeoff (or conversely how much it's 1500lb of test equipment and pilot would have had to have shrunk).

I'll also note that at Generation Orbit they spent 9 years building a Kerolox sub orbital rocket with a bought in engine and failed to launch anything. 

Now it's possible that that delay was due to complex internal management and funding issues that were nothing to do with their technical abilities and, unencumbered by such politics and better funding, their rate of progress will vastly outstrip their rate at GO.

I will wish them well and look forward to seeing what progress they make in what is a very bold goal.

BTW a quick look at biz jets shows only the Embraer Lineage and Boeing and Airbus models have room for more than 10 passengers. Everything else is 10 or less. So in addition to being a FOAK passenger carrying M5 aircraft it is also a large FOAK aircraft in its class.

[john smith 19]

In case anyone is wondering what a 19 passenger biz jet looks like. It looks like one of these
GTOW 54.5 tonnes.

[libra]

Before Flight International took their archive away, I downloaded all the stuff about Dassault own SSBJ. project (1998).