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Engine Gases Leaking Into Airframe Led To Early Termination of X-51A Flight

by John Reed on March 17, 2011

A manufacturing flaw led to the early termination of last May’s test flight of the Air Force’s X-51A Waverider hypersonic vehicle, according to Air Force officials.

The historic flight out of the Naval Air Station Point Mugu in California was terminated by safety officials about half way through its mission when the Air Force lost contact with the vehicle due to hot engine gases seeping into the aircraft’s body through a seam separating the engine and airframe.

A significant portion of the X-51A’s actual engine is mounted on the bottom of the aircraft, as seen in the picture above. A weak interface between that and the exhaust nozzle mounted on the back of the vehicle allowed hot engine gases to flow into the actual airframe. This started melting wiring packets and other critical parts, including those that transmit data back to flight controllers. Never a good thing for a flight.

“Because of those hot gases we were starting to have telemetry problems” in receiving flight data a the control center, said Charlie Brink, the Air Force Research Laboratory’s X-51A program manager during a March 15 call with bloggers. “At that 143 second point, we lost it, they did the [five second safety] count, we didn’t hear back from it so the Point Mugu folks hit the button and we terminated it.”

The Waverider was supposed to fly for about 300 seconds, reaching a speed of Mach 6. Instead, it only flew for 143 seconds hitting a max speed of Mach 5 before Point Mugu safety officials killed the flight by ordering the craft’s control surfaces to suddenly pitch, sending the X-51A cartwheeling rapidly toward the sea.

Brink says that a misread of the design team’s intentions by the builders of the X-51A led to a weak seam between the exhaust nozzle on the vehicle and the actual engine.

“There was some discrepancies in what I would call design intent, meaning what that designers wanted to happen and what the folks down in Florida put that installation together,” said Brink. “The interface was rather complex, it was the first time we ever put the vehicle together so there was no indication of sloppy workmanship of things like that. In a demonstrator you learn things and as you start talking to people and you go ‘oh, that’s what you meant, i didn’t understand the nuance of what you were calling out in that drawing’.”

In the months since, the Air Force has made the interface between engine and nozzle “a lot more robust,” added Brink.

The next flight is slated for March 22.

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{ 21 comments… read them below or add one }

Oblat March 17, 2011 at 12:47 pm

Yea another day, another botched design. Yea definitely fund this one.

>There was some discrepancies in what I would call design intent. In the months since, the Air Force has made the interface between engine and nozzle “a lot more robust,”

I guess the fix is more "robust" communication to the builders. Sort of like when you add a chunk of titanium because the seam is weak – that is really saying – "this bit shouldn't leak hot engine gases no sir-ee" to those builders.

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Bill March 17, 2011 at 2:18 pm

You seem like the sort that would say
"Hey, I could have thought of that" to every good idea ever conceived.

Hypersonics are a huge step, and are relatively uncharted. Sometimes things don't work.

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pjriot March 17, 2011 at 1:04 pm

Seriously? This is hypersonics we're talking about. Real engineering here. Its not like when you accidentally put cheese on your customers burger here. Mistakes are made, experience gained. Its called progress.

Also, well worth funding. Stuff like this has a wide variety of applications outside missile tech. Jesus, seriously, look at the last century and see what Military spending has done for the world outside of the actual military. Case in point: you're reading this.

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jeff m March 19, 2011 at 1:25 am

In other news, iRobots are being put on nulear reactor firehose duty.

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Oblat March 17, 2011 at 1:22 pm

>Mistakes are made

No you got the story wrong it was just a 'mis-communication' – the design office waved their hands like 'so' and the builders mistook it for a request to weaken the seam.

But good to see that the design spec calls for a full 6 minutes before frying the craft. Not just the 2.1 minutes achievable.

That means that after taking half an hour to get to height "anywhere in the world" 6 minutes away will live in fear of a strike. Terrorists in Canada will definitely be concerned, not all of Canada, but those in Toronto will have to be.

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Anthony March 17, 2011 at 1:55 pm

Someone call in an airstrike on this wanker please…If u hate America so much stop using the internet that we created with R&D funding. The only one who needs to work on their scientific literacy is you. Were slipping behind by what standards? Sooo many third world nations have better hypersonic missile programs than the USAF? Unless you were recently laid off at DARPA, please keep your assessments of American military technology to yourself, or to your buddies at Burger King. Thanks!

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Oblat March 17, 2011 at 3:45 pm

See what I mean. Ignorant, illogical, and barely literate – really sometimes I think we're raising monkeys to take over.

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Gregory Savage March 18, 2011 at 2:16 pm

You are the most illogical on here. When someone confronts your bs with the truth you just deflect and change the subject. Again your home nation is hardly the poster child of innovation and far from the warriors you'd like them to be. It's funny that you make these assesments.

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blight March 17, 2011 at 1:56 pm

I imagine this means you warm up and launch sooner than 143 seconds, minimum.

Alternatively in the old days, design and engineering was more closely integrated akin to the classical Skunk Works model. Nowadays, I imagine designers can no longer run down to the factory floor to check how the real deal matches up with what they have designed; which means these kinds of screwups will be tacked onto R&D costs.

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Gregory Savage March 17, 2011 at 2:13 pm

What do you mean about we? Come on we all know your not with us. You are with somebody but not the USA. Remember your calling for France selling Arms to China? That doesn't sound like its about us does it? Maybe your just jealous because France can't make this, damn they can't even make a drone.

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theman March 17, 2011 at 3:10 pm

Is anybody else stunned by how obtuse Oblate is?

Also, is anybody else aware of any other national hypersonic program that comes close to our considerable progress? I don't think we are slipping behind just yet.

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Carbon43 March 17, 2011 at 3:21 pm

I kind of like Oblat, just for the ridiculousness of their comments. I think we should keep them around for a good laugh :)

I mean "Terrorists in Canada will definitely be concerned, not all of Canada, but those in Toronto will have to be." is truly a literary gem!

Yes, Oblat is a troll… but he's so cute! Can we keep him, please?!?

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Chris Rapp March 17, 2011 at 4:45 pm

Lol, awesome.

"Oh shit, that's what you meant? See… I thought you were…. damn it."

"Yea, sorry about that. I thought you knew."

"Obviously not… shit, we just wasted a crap load of money."

"Eh, it's all for progress. We could just blame it on Iron Man screwing with our crap."

"Yea! He already took out an F-22, whats a prototype hypersonic missile?"

And then they realized Iron Man doesn't exist and went with the above story.

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Belesari March 17, 2011 at 5:43 pm

Welcome to the cutting edge people it hard.

And people dont feed oblat. HE is a troll. He really doesnt care or if he does he's just repeating what he read in the latest BS pamplet from some anti US site.

Replying to him only encourages him lok at his posting patern.

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Wells March 17, 2011 at 7:49 pm

hardly true

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PGDC March 18, 2011 at 11:00 am

You're right, the US is lagging behind a number of industrialized nations, but I wouldn't say we're completely in the hole. We've been behind before, and still managed to pull ourselves out. We may not be destined to be on top, but I wouldn't discredit the country too much. History shows we're full of highs and lows.

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Mike March 19, 2011 at 2:18 am

I still don't think that we (the US) are behind anyone in technology, at the moment, that is not to say that won't change though. What we are behind in, is the ability to purchase and field the newer high tech equipment. It's simply becoming too expensive, or is it that our money is becoming worthless….?

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asdf March 19, 2011 at 11:09 am

haven't you looked at the situation in def. procurement in europe in this….
century?
you're not the only ones that are broke.

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asdf March 19, 2011 at 11:11 am

i think in that case (being broke) it's better to have a couple of golden bullets (this missile here, for example, which would be perfect to messing up a carrier's day) then a superarmy, run on a loan.

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asdf March 19, 2011 at 11:13 am

there is also no need for a million of f-35s, especially if the version that drove the most basic requirements or design (b) is about to be cancelled…

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william September 11, 2013 at 9:51 pm

A seam between the exhaust and the body.? Am I the only one who thinks that might be a critical area!!!

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