Friday, August 10, 2018

NASA To Produce Next X- Plane to Test Reducing Sonic Booms

NASA's X-planes are justly famous.  The X-15 rocket plane from the 1950s that came close to suborbital spaceflight, the X-1 that broke the sound barrier for the first time, and the X-29 with its bizarre, reverse swept wings, to name just a few.

This year, NASA announced they've cut a contract to produce the next plane, the X-59 aimed at researching a hot area of aviation: whether supersonic aircraft can be designed to produce less boom and become commercially viable - a topic I covered a few years ago.
To help with that first issue, noise, specifically the sonic booms generated by aircraft breaking the speed of sound, NASA plans on building its first manned X-plane in decades, the X-59 Low Boom Flight Demonstrator (LBFD). The single-engine jet will be built by Lockheed’s Skunkworks as they were the only company to submit a bid on NASA’s request for an aircraft. Lockheed, which will be paid about $247.5 million for the single aircraft has a vested interest in supersonic flight; it is partnering with Aerion on a supersonic 12-passenger business jet.
To summarize the earlier discussion, everyone has heard about (or heard!) sonic booms.  When an aircraft passes through the air it creates a series of pressure waves in front of it and behind it, similar to the bow and stern waves created by a boat. These waves travel at the speed of sound, and as the speed of the aircraft increases, the waves are forced together, or compressed, because they can't get out each other's way. Eventually they merge into a single shock wave, which travels at the speed of sound.  This expands in a cone behind the plane and creates a loud sound, sometimes close to the volume of an explosion.  On a smaller scale, virtually all rifle rounds are supersonic and much of what you hear at the range is the sound of the sonic boom the bullet generates.

A theoretical model was developed by aerodynamics researchers that said the aircraft's shape could be modified to change the interaction of the waves and reduce the "boom".  Tests were performed by modifying existing aircraft and results confirmed there was improvement, leading to this X-plane program.  Rather than small modifications to an existing air frame, this one starts with a clean sheet.
That theory postulated that shockwaves generated from the front and rear portions of a plane as it sped past Mach 1 coalesced or joined together as they expanded away [from the] plane, creating two thunderous booms when they hit the ground. So, NASA’s X-59 will have a fuselage shaped by aerodynamicists so that there will be small and nuanced volumetric changes from nose to tail designed so that shockwaves off the plane do not come together and coalesce as they move toward the ground. It is hoped they create an S-shaped boom that creates a mild thump as loud as a car door closing, not the classic double-bang of an N-wave sonic boom.
(X-59 concept art.  The engine is mounted above the wing and shielded from the ground. This should direct engine noise up, keeping it from being too loud on the ground under the plane’s flight path.)
“The airplane is a brand-new shape,” says LBFD program manager at Lockheed Martin Peter Iosifidis. “Everything else within the plane, however, is commercially off the shelf or salvaged from other aircraft.”

The plane will also fly slower than the Concorde since speed is directly related to the sound level of the boom. The cruising altitude will be above 50,000 ft, about 15,000 ft higher than most airliners’ cruising level. Higher altitudes soften the booms.

The plane is designed to replicate the sonic boom of a small supersonic airliner. It is predicted to have a maximum boom loudness of 75 PLdb when going Mach 1.5 at 55,000 ft. The Concorde generated a boom of about 110 PLdb when cruising at Mach 2. (PLdb stands for “perceived decibel level. It was developed to compare the loudness of aircraft in flight and takes into account the frequency content, rise time, and several other acoustic parameters.) Flight experts think a PLdb of 75 would be low enough that regulators would permit unrestricted supersonic flight over land, but NASA’s goal is to get the X-59’s boom down to 70 PLdb.

“This is a purpose-built experimental research aircraft,” says director for air vehicle designs and technologies at Lockheed Martin, Dave Richardson. “It is not a prototype for a supersonic business jet or weapon systems. It is not a derivative or some other modification an existing airplane.”
(Confidential to Lockheed: your last few dB from 75 to 70 will probably cost as much as going from 110 to 75.  DAMHIK)  Current schedule is for the aircraft to be delivered to NASA in 2021, with first test flights from Edwards AFB's supersonic test range.  This will be to confirm safe flight and then make measurements of the sonic booms (with some interesting photographic techniques I could do a separate piece on).
Then from 2023 through 20205, Phase Three, the plane will make “community response” flights staged out of Armstrong Flight Research Center located inside Edwards AFB. There it will flyover some as-yet-unnamed California cities. Then it will demonstrate its hushed sonic boom over four to six other cities around the U.S. The communities’ responses to the sonic booms, along with readings from ground and flight instruments will be given to the U.S. and international flight agencies. Those agencies could use this data to rewrite the rules governing supersonic flight over land and open the hangar doors to faster-than-sound passenger and cargo travel over the U.S. and other countries. If the booms are too loud and obnoxious, however, supersonic flight over land will remain a dream.
(The X-59 will fly precise flight profiles as it creates sonic booms. The chase plane will also have to maintain a precise flight path as it maintains a set distance from the NASA plane while it takes schlieren photos of the X-59 backlit by the sun as both fly supersonic. A TG-14 plane will record the shockwaves in the air, and NASA will record the sonic booms those same shockwaves make on the ground. Later analysis will let NASA determine how turbulence and weather affect shockwaves.)

I'm a little schizo on this.  It is pretty cool.  If we're going to pay for a National Aeronautics and Space Administration, this is exactly the kind of research they should be involved in.   On the other hand, if they're not able to do it, someone like Lockheed or Boeing should be paying for it out of their own R&D funds. 


  1. Well, ending Phase Three in the year 20205 should give them plenty of time to figure it out...

    1. Ack!

      When I copy something like this directly from another source, I still try to proofread it. For example, I added the "[from the]" in the paragraph above the artist's concept picture. Missed this one, though.

  2. Very interesting.

    Yeah, the last few dB always cost more and take longer than anybody expects.

  3. I'm a little schizo on this.

    Socialize the costs and privatize the profits. This is tax the middle class and pay the rich just like every other thing government does. Monopolies produce high prices and bad service, and there is no exception for airplane research. Government can't develop a helicopter, a fighter airplane, or a ship that works. Nowadays NASA does space like the Veterans Administration does medicine.

  4. NASA has already been playing with this up here in the Great White North of Brevard County:

    NASA is forced to work within the constraints defined by the President and Congress. Some Congress critters take the agency seriously and use it to advance their agenda. Think Barbara Mikulski. Others do not. Think Billy Nelson or Little Marco.

    1. I knew NASA had research going since back in 2001 at various centers, but I didn't know they had flown here.

      The way that article describes the tests, it doesn't sound like they modified the airframe, but collected tons of data on how the sound waves propagate.

      Absolutely essential to have that data.

  5. They've already had an X-59, the XP-59A.

    Sort of a full-circley, repeating history thing.

  6. In no particular order:

    1) Actual scientists, and even more egregiously so, engineers, let alone the PR flacks and administration weenies who shepherd their labors, are somewhat fuzzy on the linguistic difference between "research" and "discovery". Their forte is mathematics, especially relating to chemistry and physics, and then some, but most language per se baffles the shit out of them. The two words have two distinct meanings, and are not interchangeable.

    This is not a flight research project, it's a flight discovery project. Jefferson did not send the Company Of Research to seek out the hitherto unknown headwaters of the Missouri River and the hoped-for Northwest Passage, for good reason, not least of which his facility with the English language.

    2) I note from the concept art that the airframe is to be entirely incapable of forward vision, relying presumably on purely electronic means.
    That should pay enormous dividends in taking off and landing the craft when something stops working unexpectedly. Of course, that never happens in any aircraft, let alone experimental ones, so it should pose much of a problem.
    Or are we just switching aircraft flight entirely to the aerial equivalent of submarine navigation now? Trading pilots for aeronauts?
    If that's the case, it should be a boon to would-be aviators previously turned down for wearing coke-bottle-thick glasses. I thought we'd settled this sort of question decisively during Project Mercury.

    3) Attenuating the noise is all well and good, and actually exactly the sort of frontiers-of-flight stuff NASA was charged with when it started out as NACA. But absent nearly any direct governmental, i.e. Air Farce/Navy/etc. applicability or benefit, which looks to be essentially nil, this is a research project well within the capabilities of the budgetary means of Boeing, Lockheed, and Northrop. It should therefore be funded by each of them, without exception, to the tune of 30% apiece from the outset, with NASA taking up the last 10%, and under joint direction and supervision, with any discoveries joint property. If anyone else wants to share in the risk and bounty, let them ante into the game, and thus take the bear trap out of the taxpayers' @$$#$ for funding this project. Fair is fair.

    1. Sounds like a great idea as long as you're willing to let the data gained be proprietary. Furthermore, Uncle gets involved heavily when sonic booms are generated. Doing this under the auspices of NASA makes the results publicly available, and eases the government approval aspect. But then if you don't mind setting up a monopoly, then your approach is fine.

    2. There are three major American aerospace firms. There would be no such monopoly, nor would it be proprietary except to those participating. A three way split, plus the government, by definition is a non-monopoly. The results simply would be proprietary to the participating American companies.
      Unless, by mutual assent, some other equal partner wanted to ante into the game.

      The only party being squeezed out of this deal is the taxpayer's wallet, for the most part, i.e. 90%.


  7. (cont.)
    4) As noted by the host, setting specific dB targets is recockulous.
    One digs down for oil, and hits it where they do. Or not. One does not specify the exact foot-level where that will occur, even with a rough idea of where it lies.
    And if it proves impossible to get to 70 PLdB, they may well expend metric f**ktons of taxpayer dollars chasing Moby Dick, when they could have quit at, e.g., 72 dB or 74 dB, should something like that prove to be the actual capability achievable.

    Since they're government workers (and I use that last word in the loosest connotations), and getting paid by the hour, which scenario is more likely...? Declaring victory at 90-something percent of goals, or experiencing a budgetary lifespan that would shame the longevity of the TVA and the Federal Mohair Subsidy?

    So once again, either put the funding back in private pockets, or cap this thing at a set - and short - timespan. Say two years, max, to get what they can get.

    Otherwise, it's textbook boondoggle.

    And in ten years, it will be charged with reducing the noise of sonic boons over Mecca and Medina during 5X/daily prayers, like similar NASA nonsense during the last administration. If not cancelled entirely to save the hearing of the spotted owl after PETA and WWF raise concerns.

    I point to the asstards from Greenpeace complaining about nautical sonar and engine noise in the oceans already as proof of the concept.
    If the navy would simply and literally sink their silly-ass craft on sight, it would all be quite a hoot, or Congress mandate that if they had any complaints, they themselves be directed to stuff earplugs into every mammal and whale extant. But that would require both a Congress and Navy worthy of the name, and both are too busy crashing into everything that moves to do their frickin' jobs as it is.

    5) As to the actual venture, I look forward to the day when the trip from my doorstep to the boarding gate takes five times as long as the trip from the LAX to New York or Hawaii, instead of the current system under which the two portions of the trip are roughly equal periods.
    If the project can figure out a way to disband the TSA entirely instead, possibly by ejecting them individually from test aircraft at altitude at Mach 5 to see if their screams can be made quieter, I would march in their parade and subscribe to their newsletter. Heaven knows it's the only way they can be made to move any faster than their current speed, and at least they'd be improving the lot of the common citizen and expanding the boundaries of science at the same time.