Scramjet FTW!

[Isgrimnur]

MSNBC

An experimental aircraft has set a new record for the longest hypersonic flight after streaking across the sky Wednesday for more than three minutes while flying at Mach 5 — five times the speed of sound — the United States Air Force has announced.

The vehicle, called the X-51A Waverider, dropped from a B-52 Stratofortress mother ship while flying over the Pacific Ocean just off the southern California coast. It successfully ignited an air-breathing scramjet engine than accelerated up to Mach 5, Air Force officials said in the announcement.

The entire test flight lasted just over 200 seconds, more than 10 times longer than the previous hypersonic record (just 12 seconds) set by NASA's X-43 vehicle in 2004.
...
Four seconds into the flight, the X-51A's solid rocket booster – actually an adapted Army Tactical Missile booster – accelerated the experimental aircraft to Mach 4.8 before being jettisoned to let the scramjet engine take over.

After the flight, the vehicle was expected to splash into the ocean. There were no plans to recover the craft, according to the Air Force.

[craterus]

After the flight, the vehicle was expected to splash into the ocean. There were no plans to recover the craft by the US, according to the Air Force.

ftfy



would be surprised if there wasn't something useful in the recovery of that device (whether to china or russia or whomever)

[LawBeefaroni]

would be surprised if there wasn't something useful in the recovery of that device (whether to china or russia or whomever)

If there was, I'm sure the Air Force took the appropriate steps to ensure it was unrecoverable/unusable.



I wonder at what point an unmanned aircraft becomes a missile? It is based on flight capabilities? Recoverability? I guess a missile is a weapon itself, an aircraft carries weapon systems, maybe?

[stessier]

If I did the math right (and assuming that Mach is using the speed of sound at sea level and not whatever that altitude was), the jet was only under power for 42 miles (761 mph * 200 s * 1 h / 3600s). Seems like it should be further than that.

[theohall]

If I did the math right (and assuming that Mach is using the speed of sound at sea level and not whatever that altitude was), the jet was only under power for 42 miles (761 mph * 200 s * 1 h / 3600s). Seems like it should be further than that.

I think you forgot the "* 5" on top. It was Mach 5, not Mach 1.

So 761 mph * 5 * 200s * 1 h/ 3600 s = ~211 miles.

[Biyobi]

That would explain all the high altitude vapor trails I saw across the sky yesterday afternoon. Somehow missed the sonic booms though.

[stessier]

If I did the math right (and assuming that Mach is using the speed of sound at sea level and not whatever that altitude was), the jet was only under power for 42 miles (761 mph * 200 s * 1 h / 3600s). Seems like it should be further than that.

I think you forgot the "* 5" on top. It was Mach 5, not Mach 1.

So 761 mph * 5 * 200s * 1 h/ 3600 s = ~211 miles.

At least I had the disclaimer in there and showed my work. Partial credit FTW!

[Remus West]

The way they are forcing standardized testing down our throats everything is multiple choice. Which means extra credit is a thing of the past and you are just wrong.

[Isgrimnur]

The test was at Angels 50 (50,000 feet). Per NASA, Mach speed at that alititude is 660.5 mph, making Mach 5 to be 3,302.5 mph

660.5 mph * 5 * 200 s * 1 h / 3600s = 183.472 miles

The craft is covering over 9/10 of a mile every second at full speed.

[LawBeefaroni]

Metres per second anyone?

[Isgrimnur]

Metres per second anyone?

Google FTW!

[stessier]

The test was at Angels 50 (50,000 feet). Per NASA, Mach speed at that alititude is 660.5 mph, making Mach 5 to be 3,302.5 mph

660.5 mph * 5 * 200 s * 1 h / 3600s = 183.472 miles

The craft is covering over 9/10 of a mile every second at full speed.

So my question is when they report Mach numbers, do they always take into account the altitude? I know that the speed of sound changes with altitude, but why would you make your reports variable like that? Isn't the whole point to show off in comparison to other reports (which would be far more complicated if you had to take altitude into account every time)?

[stessier]

The way they are forcing standardized testing down our throats everything is multiple choice. Which means extra credit is a thing of the past and you are just wrong.

I always figure out how they get all the answers on a multiple choice test, so I would have caught my error in that case.

That's my story and I'm sticking to it.

[Isgrimnur]

So my question is when they report Mach numbers, do they always take into account the altitude? I know that the speed of sound changes with altitude, but why would you make your reports variable like that? Isn't the whole point to show off in comparison to other reports (which would be far more complicated if you had to take altitude into account every time)?

Wiki

The Mach number is a dimensionless, unitless number that is derived from the speed of an object divided by the speed of sound in the medium through which it is travelling. Given that the speed of sound varies by altitude, the Mach number has to account for it at all times. It also has to account for atmospheric pressure, so the speed to get to a particular Mach number would be lower at the eye of a hurricane and higher at the center of a high pressure system.

My understanding is that once you get to these high speeds, the Mach number has more to do with the physics involved regarding the airflow and shockwaves than any objective measure of the speed does. Knowing the performance at Mach 5 at Angels 50 extrapolates well to Mach 5 at Angels 10 better than knowing the performance at 3,000 mph, as the shockwave effects and airflow issues are going to be less pronounced, as your Mach number is lower at the lower altitude.

[stessier]

Gotcha (and thanks!).

But still - for the general public consumption, it is a lot more interesting to hear something went 3000 mph vs 4000 mph, regardless of how high it was when it did it.

[The Meal]

That would explain all the high altitude vapor trails I saw across the sky yesterday afternoon. Somehow missed the sonic booms though.

My understanding is that (part of the) technology here is to make a system where the bow-shock adders on the jet profile itself do not lead to such severe sonic booms. Yeah, the propellant is technology, but so is the profile smoothing (so to speak).

Cool stuff.

[Bakhtosh]

Many people belive the Air Force has been using black-project hypersonic aircraft for years. IF that's the case, is there any significance to the timing of this test?

What's the distance from CA to N. Korea? Divide that by 3,300 mph.

[stessier]

Many people belive the Air Force has been using black-project hypersonic aircraft for years. IF that's the case, is there any significance to the timing of this test?

What's the distance from CA to N. Korea? Divide that by 3,300 mph.

Flight math says CA to Seoul is 5,968 miles. Add a bit to get further north. So a little under 2 hours.

[Isgrimnur]

Make that Mach 6.

[Teggy]

Test today:
http://www.npr.org/blogs/thetwo-way/201 ... nic-flight" target="_blank

Odd that they just dump the thing in the ocean. Today's test pilots are wimps - I'm sure Chuck Yeager would have taken it for a spin

[theohall]

Test today:
http://www.npr.org/blogs/thetwo-way/201 ... nic-flight" target="_blank

Odd that they just dump the thing in the ocean. Today's test pilots are wimps - I'm sure Chuck Yeager would have taken it for a spin and landed it.

(FTFY in italics)

[LawBeefaroni]

Test today:
http://www.npr.org/blogs/thetwo-way/201 ... nic-flight" target="_blank

Odd that they just dump the thing in the ocean. Today's test pilots are wimps - I'm sure Chuck Yeager would have taken it for a spin and landed it.

(FTFY in italics)

Chuck Yeager is the man but even he can't fly and land an unmanned plane.

[Ralph-Wiggum]

Scramjet FTL!

The U.S. Air Force's experimental X-51A Waverider failed yesterday in its bid to hit that hypersonic speed. Although the aircraft did separate as planned from its B-52 mother ship in midair, things quickly went wrong. The official Air Force statement describes things this way:

The X-51 safely separated from the B-52 and the rocket booster fired as planned. However after 16 seconds, a fault was identified with one of the cruiser control fins. Once the X-51 separated from the rocket booster, approximately 15 seconds later, the cruiser was not able to maintain control due to the faulty control fin and was lost.

The X-51A was supposed to fly for 300 seconds (that is, 5 minutes).

[LawBeefaroni]

Heads are probably rolling...

[theohall]

Test today:
http://www.npr.org/blogs/thetwo-way/201 ... nic-flight" target="_blank

Odd that they just dump the thing in the ocean. Today's test pilots are wimps - I'm sure Chuck Yeager would have taken it for a spin and landed it.

(FTFY in italics)

Chuck Yeager is the man but even he can't fly and land an unmanned plane.

Says who?

[Paingod]

Heads are probably rolling...

Is this a "lowest bidder" failing, or some geek in engineering that accidentally forgot to carry a 1?

[LawBeefaroni]

Test today:
http://www.npr.org/blogs/thetwo-way/201 ... nic-flight" target="_blank

Odd that they just dump the thing in the ocean. Today's test pilots are wimps - I'm sure Chuck Yeager would have taken it for a spin and landed it.

(FTFY in italics)

Chuck Yeager is the man but even he can't fly and land an unmanned plane.

Says who?

Everyone! Well, except maybe Slim Pickens.

[LawBeefaroni]

Heads are probably rolling...

Is this a "lowest bidder" failing, or some geek in engineering that accidentally forgot to carry a 1?

They've described the control fin as "faulty" so depending on the cause of the fault, I'm guessing whoever designed or built the subsystem. It did work previously but a 66% reliability rate on 3 flights isn't exactly a statistic.

It's not a lowest bidder thing, I don't think, because it's a prototype.

[theohall]

Heads are probably rolling...

Is this a "lowest bidder" failing, or some geek in engineering that accidentally forgot to carry a 1?

They've described the control fin as "faulty" so depending on the cause of the fault, I'm guessing whoever designed or built the subsystem. It did work previously but a 66% reliability rate on 3 flights isn't exactly a statistic.

It's not a lowest bidder thing, I don't think, because it's a prototype.

66% reliability for an aircraft???? Say a passenger airline had 66% reliability for the empennage working properly. 1 in 3 planes fall out of the sky. That is not "reliability" but more accurately a 33% failure rate.

[Isgrimnur]

That X stands for experimental. Experimental things fail, and knowledge is gained in the process to account for the cause and prevent repeat failures.

Any comparison to a passenger aircraft of any sort is specious at best.

[theohall]

That X stands for experimental. Experimental things fail, and knowledge is gained in the process to account for the cause and prevent repeat failures.

Any comparison to a passenger aircraft of any sort is specious at best.

True - but having a 33% failure rate on a component which does not fail that often on most aircraft is not a good thing. Particularly when aircraft designed in the 60s flew for decades at close to these speeds without failing at all in actual operation.

[Isgrimnur]

Give them some more time to get TW sample size up. Also, they're not reusing craft. It's one out of three vehicle failures, which means that it's one out of eighteen fin failure.

[theohall]

Give them some more time to get TW sample size up. Also, they're not reusing craft. It's one out of three
vehicle failures, which means that it's one out of eighteen fin failure.

Is it the same fin failing? If it is the same fin on three aircraft, it is a one in three failure - not a 1 in 18. Do we have that detail? It's not evident from the articles.

[Isgrimnur]

The first flight was a successful launch, but failed to meet the planned duration. The second was a failure to start the test engine. Only the third has had a control surface malfunction.

Details are at the wiki page in the OP.

[Fretmute]

The first flight was a successful launch, but failed to meet the planned duration. The second was a failure to start the test engine. Only the third has had a control surface malfunction.

Given that we can land a car on Mars via the most elaborate shenanigans ever, a fin failure is pretty depressing.

[Isgrimnur]

Fourth test coming:

The U.S. Air Force says it now plans to fly the last in a series of four Boeing-built experimental hypersonic vehicles in late spring or early summer under a troubled testing program that the service weighed canceling following an Aug. 14 failure.
...
The failure investigation [on the third flight] is expected to be completed by mid-December, Brink said.
...
[Charlie] Brink [X-51A program manager] said he expects the Air Force to conduct a follow-on program to "mature scramjet engine technology" after the fourth X-51A flight but declined to discuss specifics.

[Isgrimnur]

Fourth (final) flight results

EDWARDS AIR FORCE BASE, Calif., May 3, 2013 – A Boeing [NYSE: BA] X-51A WaveRider unmanned hypersonic vehicle achieved the longest air-breathing, scramjet-powered hypersonic flight in history May 1, flying for three and a half minutes on scramjet power at a top speed of Mach 5.1. The vehicle flew for a total time of more than six minutes.

“This demonstration of a practical hypersonic scramjet engine is a historic achievement that has been years in the making,” said Darryl Davis, president, Boeing Phantom Works. “This test proves the technology has matured to the point that it opens the door to practical applications, such as advanced defense systems and more cost-effective access to space.”

A U.S. Air Force B-52H Stratofortress from Edwards Air Force Base released the X-51A from 50,000 feet above the Point Mugu Naval Air Warfare Center Sea Range at 10:55 a.m. Pacific time. After the B-52 released the X-51A, a solid rocket booster accelerated the vehicle to about Mach 4.8 before the booster and a connecting interstage were jettisoned. The vehicle reached Mach 5.1 powered by its supersonic combustion scramjet engine, which burned all its JP-7 jet fuel. The X-51A made a controlled dive into the Pacific Ocean at the conclusion of its mission. The test fulfilled all mission objectives.

The flight was the fourth X-51A test flight completed for the U.S. Air Force Research Laboratory. It exceeded the previous record set by the program in 2010.

[Isgrimnur]

The Drive

The Air Force recently broke the record for the highest thrust producing air-breathing hypersonic engine the service has ever tested in its history, at least that we know about. Northrop Grumman built the scramjet engine for the Air Force Research Laboratory and its development comes amid a general renaissance in all things hypersonic across the U.S. military.

The Air Force Research Laboratory announced the achievement on Aug. 5, 2019, but did not say specifically when it had occured. AFRL and Northrop Grumman had tested the 18-foot long fighter-engine sized scramjet powerplant across a nine-month period. The engine ran for a total of 30 minutes across an unspecified number of tests, generating up to 13,000 pounds of thrust under conditions the engine would experience at speeds of above Mach 4. The testing occured at the Arnold Engineering Development Complex's (AEDC) Aerodynamic and Propulsion Test Unit at Arnold Air Force Base in Tennessee.
...
It is worth noting that while the Air Force's official release described the engine running at "conditions above Mach 4," hypersonic speed is typically described as being Mach 5 and above. As such, the actual conditions during at least some of the testing may have been more extreme.

[Isgrimnur]

Scramjet FTL!

The U.S. Air Force's experimental X-51A Waverider failed yesterday in its bid to hit that hypersonic speed. Although the aircraft did separate as planned from its B-52 mother ship in midair, things quickly went wrong. The official Air Force statement describes things this way:

The X-51 safely separated from the B-52 and the rocket booster fired as planned. However after 16 seconds, a fault was identified with one of the cruiser control fins. Once the X-51 separated from the rocket booster, approximately 15 seconds later, the cruiser was not able to maintain control due to the faulty control fin and was lost.

The X-51A was supposed to fly for 300 seconds (that is, 5 minutes).

December 2012 report

"At about 15 seconds, inexplicably, the upper right fin became unlocked, and the fin, because of the aerodynamic forces that were seen, pitched," says Charlie Brink, the AFRL's X-51 programme manager, "and in a few seconds moved from zero angle-of-attack to full trailing edge down. The whole stack assembly started to do a very slow corkscrew," he adds.

Having become unstuck and mobile several seconds before it was meant to, the fourth fin was uncontrollable by the time the other three aerodynamic fins were powered on; about 2s before the booster rocket detached and fell away.

"The actuator was either damaged or stuck, so for about a second and a half the booster was struggling to maintain aerodynamic control, and we had three fins controlling a vehicle that requires four," says Brink. The X-51 lost control before its scramjet engine was scheduled to ignite.

While technicians quickly surmised that the fin had become unstuck, the investigation ruled out an erroneous command signal or electromagnetic interference. It now appears most likely that the stack (as the vehicle plus booster is known) began to vibrate at a frequency sympathetic to a crucial fin part.

"It looks like the second bending node at the stack, the frequency at which that occurs happens at a key frequency that is very close to the lock mechanism that holds the actuator. That's very preliminary," says Brink, but it "looks like we had some cross-coupling between the natural resonance of the stack and the natural resonance of that actuator."