Boom Supersonic Overture M1.8 SST

Fifteen more test fights until going supersonic? Given the XB-1 no longer shares aerodynamic configuration with the Overture I'm not sure what such a cautious test program is meant to achieve.

Its planform is different, its configuration is different, its engines are different. What is its purpose?
 
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Kiltonge said:
Its planform is different, its configuration is different, its engines are different. What is its purpose?
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At this point I think it’s just to build confidence - that the engineers know what they’re doing, that the design models work, and that they have a good experimental process in place. Any mistakes they make at this step are less serious and good learning opportunities. I guess that shouldn’t be underestimated.
 
Zoo Tycoon said:
Zoo Tycoon said:
“Does anyone know if the J85 has steel LP compressor blades/staters?

I notice it was never used in any super cruise applications and typically super cruise engines will have a steel front end. This was/is because of the heat build up during sustained supersonic flight. Aluminium Alloy loses strength too quickly and Titanium has a habit of catching fire although has seen a few applications. Most supersonic aircraft such as the F5 will only be cleared for a short time at high speed measured in tens of seconds to a few single minutes. The XB1 usefulness will be significantly limited if it can’t collect sustained supersonic flight thermal flux data.

Also has anyone seen objective for time at supersonic Mach number?
Nobody has had issues with titanium fires in their engines since the 1960s, because people learned just how much stretch was happening and made the appropriate allowances for it.”

Scott Kenny replied;-
Nobody has had issues with titanium fires in their engines since the 1960s, because people learned just how much stretch was happening and made the appropriate allowances for it.

Zoo Tycoon
Ah no, Concorde entered service in 1976, and by 1980 had suffered two Ti compressor fires. So several Ti compressor stages were changed to steel. I understand the problem wasn’t blade stretch, but manufacture quality assurance. Remember that in the first five years of Concorde service the fleet, although small, achieved about 100 x the time at Mach 2 as the entire military previous experience. The grim reality associated with pioneering is a harsh mistress.
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Titanium fires (or as we in the propulsion community call them “rapid oxidation events”) need high oxygen partial pressures and temperatures to propagate and very high temperatures to start. The rear stages of the compressor can provide the pressure / temperature conditions and a broken Ti blade rub can generate the ignition temperature.

Most modern engine compressors have Ti front ends and transition to nickel disks, airfoil and cases toward the rear of the compressor to address the Ti fire issue. The original F100 had a complete Ti high compressor and had to change to Ni in the last 7 compressor stages after a few development engines virtually disappeared on test cell when a fire started. The higher the compression ratio and the faster you fly, the farther forward the nickel components. But even the Mach 3+ J58 first few compressor stages were Ti construction and nickel (Waspalloy) after that.

When P&W added fan blade containment to the F-14 / TF30-P-412 engine, they found that a fan blade release caused sufficient vibration that resulted in a Ti fan spacer to rub against a Ti stator inner shroud, generating high enough rub temperatures to ignite the Ti. The fix was to change the stator inner shroud to steel. The rub still occurred in a blade out condition, but the steel melted below the Ti ignition temperature, and it acted as a molten steel journal bearing to keep the fan rotor centered until the engine stopped turning.
 
F119Doctor said:
When P&W added fan blade containment to the F-14 / TF30-P-412 engine, they found that a fan blade release caused sufficient vibration that resulted in a Ti fan spacer to rub against a Ti stator inner shroud, generating high enough rub temperatures to ignite the Ti. The fix was to change the stator inner shroud to steel. The rub still occurred in a blade out condition, but the steel melted below the Ti ignition temperature, and it acted as a molten steel journal bearing to keep the fan rotor centered until the engine stopped turning.
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I bet those were exciting...
 
Scott Kenny said:
I bet those were exciting...
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It was definitely demonstrated on test cell with the first fan disk deliberately modified with features that would release one fan blade on command.

There were several F-14s lost due to fan blade uncontained liberations that caused secondary damage to hydraulic line, etc. The containment fix was retrofit on the -412A engines, and in production in the -414 variant. I’m not sure there was ever a blade liberation event after the containment was implemented, so it wasn’t ever challenged on a flying engine.
 
Titanium (?) Port Engine Mount/Housing, looking forward.

On a side note, the XB-1 has no egress or ejection seat!
 

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Flogger15 said:
On a side note, the XB-1 has no egress or ejection seat?
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I thought you might have been kidding about that and did a quick check.
This is what I've found here:
Screenshot 2024-03-24 at 22-15-44 Should This Exist What if you could travel faster than the s...png
Screenshot 2024-03-24 at 22-16-05 Should This Exist What if you could travel faster than the s...png

Yep.
Not putting an ejection seat on an experimental supersonic aircraft is just like eating lettuce.

These people are completely REDACTED
 
In avoidance of risk, you end up taking the worst risk of all, which is not making any progress, and not having any adventure.

Now where have I heard that before?

Oh yes...

www.businessinsider.com

The maker of the lost Titan submersible previously complained about strict passenger-vessel regulations, saying the industry was 'obscenely safe'

In a 2019 interview about the Titan, OceanGate CEO Stockton Rush lamented the effect of safety regulations on the commercial submersible industry.
www.businessinsider.com www.businessinsider.com

www.goodreads.com

A quote from Peter Pan

To die will be an awfully big adventure.
www.goodreads.com
 
I took a short tour of the Boom Supersonic facility several years ago and asked about what type of ejection seat they planned on using in the XB-1, the answer was 'none'. Considering the size of the fuselage and the additional weight of any current ejection system (except maybe a 'Yankee' type), I can see why they chose not to install one.
I'm attaching a few pictures of some XB-1 wind tunnel models they have on display in their lobby.
 

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CiTrus90 said:
I thought you might have been kidding about that and did a quick check.
This is what I've found here:
View attachment 723385
View attachment 723386

Yep.
Not putting an ejection seat on an experimental supersonic aircraft is just like eating lettuce.

These people are completely REDACTED
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You're talking about putting an ejection seat into an aircraft powered by a single J85 engine that makes less than 3000lbs thrust (5klbs in afterburner).

An ACES II seat is 127lbs and the rockets are another 21, total of ~150lbs of seat. Can't find a reference online for the weight of the internal structure, but it's not going to be light since you need a solid bulkhead to attach the seat rails to. Guesstimating another 100lbs of structure, maybe someone can prove me wrong. That's 250lbs of weight you need, compared to a ~25lb pilot seat and another ~25lbs of parachute (if you're testing with the pilot wearing a parachute). 200lbs or so extra.

Sometimes you just have to say "we cannot afford that much weight."

And then you run a model in the wind tunnel (or the full size plane in a big enough wind tunnel!) to make sure that it will actually fly well enough at low speeds.

You need to know where you can take risks, and where you need to avoid them.
 
Scott Kenny said:
You're talking about putting an ejection seat into an aircraft powered by a single J85 engine that makes less than 3000lbs thrust (5klbs in afterburner).
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Actually three J-85s, with an MTOW of 17,400 lbs (per AvWeek in 2020). That's up from 13,500 lbs in 2016 (per a Boom Press release back then)

If the AvWeek story is still correct, Boom expect the XB-1 to be decidedly "sporty" on landings; they designed for 185 knots touchdown speeds and 13 fps (almost 800 fpm) sink rates.
 
Scott Kenny said:
Sometimes you just have to say "we cannot afford that much weight."
[...]
You need to know where you can take risks, and where you need to avoid them.
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As pointed out by TomS, the XB-1 has 3 J-85s.
It immediatly comes to my mind that there already exist an aircraft powered by 2 J-85s that routinely reaches over mach 1 since the year 1959: it's the T-38.
And that aircraft has 2 ejection seats on board.

Opting to not put an ejection seat into the XB-1 is not a matter of saving weight because they would otherwise not reach supersonic speeds.
They chose to do so, because increasing weight would add costs and time (which is, once again, money) to their project.

To say they are taking risks to make something innovative is simply not true.
Supersonic flight is something that we, as a species, have been routinely doing for well over 60 years.
They are not pushing any particular technological barrier here, they are not at the bleeding edge of the envelope. The engines they use are dated, the aerodynamics they are investigating is nothing exotic and the materials they use aren't anything novel per se.
The XB-1 as an aircraft is meant to:
1 - validate Boom Supersonic internal R&D efforts and
2 - show something tangible to their investors

These people willingly sat down in a room, in front of an excel spreadsheet, and decided where they could cut corners to reach those two points above.

That is morally reprehensible to me.

We are talking about a single seat experimental aircraft, not a passenger jet where you can't realistically provide the people on board with an escape system while in flight.
Designing their aircraft with an ejection seat from the start wouldn't have made it impossible for them to make a supersonic aircraft.
It would have just taken longer and made it more expensive.

Flying is a risky activity, we can all agree on that. But pushing the envelope has always gone hand in hand with mitigating those risks to a reasonable and acceptable level. Nobody is "yoloing" in this industry anymore when we have already learnt so much through the sacrifice of the many that came before us.
Boom is not pushing the envelope with the XB-1.
If they will ever be able to make their Overture passenger jet (which is a big IF), that aircraft will already be obsolete by the time it takes to the sky, thanks to NASA's X-59 research efforts in quieter supersonic flight.
Oh and, by the way, the X-59 has an ejection seat.

Mitigating risks means doing everything reasonably possible to avoid the worst outcomes. Putting an ejection seat on a research aircraft is not something impossible, it's just what they decided NOT to do.

That is infuriating to me.
They are betting on everything hopefully working to perfection, but hope is not a viable currency in this line of work.

And comparing the risk of crashing in a research aircraft to getting E.Coli while eating a salad is the stupidest thing I've ever read.
 
@CiTrus90 Did you miss where they said as a result of NOT having the "get out of jail free card" (their words) in the ejection seat, they ran some physical tests in a wind tunnel to get some early verification of their computer modeling?

(My edit to make it very clear who I am replying to)
 
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Scott Kenny said:
Did you miss where they said as a result of NOT having the "get out of jail free card" (their words) in the ejection seat, they ran some physical tests in a wind tunnel to get some early verification of their computer modeling?
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“Should it have an ejection seat?” That particular one was really a gut-wrenching decision that I ultimately had to make myself. We decided not to put an ejection seat in the airplane.


The second order effects were fascinating. As soon as we said we’re not giving ourselves a “get out of jail free” card on safety, all of a sudden a lot of other things that we hadn’t been doing that would bring home the airplane and the pilot started to be on the table: “Why don’t we do a final confirmatory wind tunnel test instead of trusting our iterations on the simulations?”
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Ok, let's try to understand what that means. Can we do that effort?

They decided for "whatever reason" (i.e. money) not to put an ejection seat into the XB-1.
They then realized they still needed to consider (and provide) some mitigating safety efforts to "bring home the airplane and the pilot" that, by their own admission, they "had not been doing" beforehand.
Which is absolutely retarded, because those safety concerns needed to be addressed even if there was an ejection seat on board, since you plan for an aircraft to fail-safe with redundancies.
Multiple redundancies.

Doing a "final confirmatory wind tunnel test" doesn't address safety of flight concerns for the pilot. It's just a way to verify correspondence between what you see on the software and what the scale model effectively does in the wind tunnel.
Both of those things are not necessarily going to align 100% with what the aircraft will do once in the air.
Also, all aircraft projects go through wind tunnel testing at some point or the other in their development, they don't just go from software to being cut into metal and composites.

If the hydraulic system fails, how is the confirmatory wind tunnel test going to help the pilot bring the aircraft home?
If one (or more) of the engines has an uncontained engine failure or experiences a bird-strike, how is the confirmatory wind tunnel test going to help the pilot bring the aircraft home?
We assume with 100% certainty that nothing is going to ever fail on that aircraft under any circumstance?

The ejection seat is the last resort when things don't go to plan, it's not a commodity, there is a reason they exist.
We are not talking about a Citation or a Gulfstream or a 737 where you can't realistically put one on board due to the nature of the aircraft in consideration.

If Boom Supersonic is that confident in their own processes they should have built the Overture from the start, without starting with a scale demonstrator.
Usually, if you are not confident in something that means you should take actions to reduce risks. Not putting an ejection seat in, doesn't reduce risks, it reduces costs here.
 
Scott Kenny said:
You're talking about putting an ejection seat into an aircraft powered by a single J85 engine that makes less than 3000lbs thrust (5klbs in afterburner).
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The Folland Gnat trainer, powered by a 20 kN Bristol Orpheus, had TWO ejection seats.
 

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CiTrus90 said:
As pointed out by TomS, the XB-1 has 3 J-85s.
It immediatly comes to my mind that there already exist an aircraft powered by 2 J-85s that routinely reaches over mach 1 since the year 1959: it's the T-38.
And that aircraft has 2 ejection seats on board.
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Which ironically is the chase aircraft for the XB-1.
 
Yes, it all come down to cost.
Fitting an ejection seat is not like shopping at IKEA. You need some more design hours and test benches for system test and integration and probably the scrutiny of some Martin Baker/Collins critical eyes.

Regarding the discussion on the burden of the extra mass, anybody with right academics can convert the extra material mass in the engine mounts (see picture above) into an adequate structure to safely hold an ejection seat in the cockpit (if that is not from their iron bird)
 
I'm thinking that if I were a test pilot flying any kind of prototype or high-performance aircraft, I would insist on some kind of ejection seat. Furthermore, if I were an aircraft designer, even for a 'demonstrator' aircraft, the plans would have included one from the start!
Pretty impressive either way, I hope they continue flight tests with no mishaps.

I thought about something a talking head said about the mess that Boeing Aircraft is in lately, they stopped listening to the designers and started listening to the MBA's!
 
Scott Kenny said:
Y'all gonna lose your minds when you find out how many transport aircraft are flight tested without any way for the crew to bail out...
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On the contrary, tansport aircraft are initially tested with the crew wearing bonedomes and parachutes. Their escape route is via slides with explosively-jettisoned external panels.

Here's the A350 test crew:
 

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Buffet at that low speed (which is not really low with an indicated 170kts something)? See also the aggravated downward pitch of the elevator in the landing phase. The nose is also yawing but I can't see an opposite aileron action from the pilot.

I guess that they could regret not to have an ejection seat.

Notice: that's probably why there was no attempt of a flare during the landing (see the hard landing comments).
 
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TomcatViP said:
Buffet at that low speed (which is not really low with an indicated 170kts something)? See also the aggravated downward pitch of the elevator in the landing phase. The nose is also yawing but I can't see an opposite aileron action from the pilot.

I guess that they could regret not to have an ejection seat.

Notice: that's probably why there was no attempt of a flare during the landing (see the hard landing comments).
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They had no flaps when the pilot said he was doing 12AOA. The elevators are very small I wonder if they are going to have to make them bigger to give the pilot more authority.
 
I might be mistaken, but the speed and decent rate of the XB-1 on landing is pretty close to an F-18, not figuring in a moving runway/deck.
 
Flogger15 said:
I might be mistaken, but the speed and decent rate of the XB-1 on landing is pretty close to an F-18, not figuring in a moving runway/deck.
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The Hornet is around 135 knots on approach, when the XB-1 reported 175 knots at the same stage. Descent rate at landing should be around 6-700 fpm, versus 800 for the XB-1. So, not super close, I'd say.
 
TomS said:
The Hornet is around 135 knots on approach, when the XB-1 reported 175 knots at the same stage. Descent rate at landing should be around 6-700 fpm, versus 800 for the XB-1. So, not super close, I'd say.
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I saw 1800fpm descent rate for a Hornet on a blind carrier approach...
 
Boom’s chief test pilot Bill “Doc” Shoemaker, who conducted a flying qualities assessment during the XB-1’s initial 12-min. flight, is scheduled to fly the second test mission. This will “take it up to 16 deg. AOA (angle-of-attack) and will also evaluate the sideslip which will expand the envelope in order to give us a little bit more margin on a nominal landing. It will also be the first time the ‘dampers’—or stability augmentation system—is used,” Shoemaker adds. The landing gear will also be retracted and extended for the first time on the second flight.
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FAA Clears Boom For XB-1 Supersonic Tests | Aviation Week Network

The special flight authorization is the first ever issued by the FAA for tests of a civil supersonic aircraft.
aviationweek.com aviationweek.com

As guessed earlier the lateral stability and AoA were problematic. It is then understandable that adding the SAS for the next flight takes them time. I am only wondering why it wasn´t part of the first flight configuration.
 
TomcatViP said:

FAA Clears Boom For XB-1 Supersonic Tests | Aviation Week Network

The special flight authorization is the first ever issued by the FAA for tests of a civil supersonic aircraft.
aviationweek.com aviationweek.com

As guessed earlier the lateral stability and AoA were problematic. It is then understandable that adding the SAS for the next flight takes them time. I am only wondering why it wasn´t part of the first flight configuration.
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My guess would be wanting a baseline. It's good to know that your plane is "only" a twitchy pain in the butt to fly if the SAS fails, instead of being a reason to eject immediately.
 

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