Those of us of a certain age can remember when sonic booms were a semi-regular feature of life. During the Cold War, the Air Force and the Navy/Marines were a lot more casual about breaking the sound barrier. (Today, they try to restrict it to airspace where it won’t impact people on the ground. Usually.) For those who haven’t experienced one, here’s a NASA video explaining what happens.
The speed of sound refers to the speed at which pressure waves (sound) move through the air; an aircraft (or rocket) moving faster than that speed is moving faster than the air can get out of the way and flow around it. The aircraft is shoving it out of the way, like barreling through a crowd knocking people down. (Think of the boom as air molecules shouting “Hey!”) Supersonic flight is best done at higher altitudes where the air is thinner, among other reasons.
There are reasons to go supersonic besides a high-speed scramble by fighters trying to intercept something or a bomber trying to penetrate hostile airspace as quickly as possible. For commercial purposes, it’s about reducing travel time on really long flights — usually trans-oceanic. (The Soviet Union was a case where domestic supersonic air travel seemed like a good idea. Even though they’re now talking about going from 11 down to 9 time zones, it’s still a long way to travel.)
Sonic Booms are disruptive obviously — and can be destructive — but it’s the noise that’s the big problem for commercial flights. Hence this program by NASA to explore if aircraft shape can be tailored to minimize the shockwave and ground footprint from supersonic flight. And if you think we’ve been here before with Concorde,
...Concorde, which last flew in 2003, utilized 1950s technology, was only supersonic over the ocean and was deemed too noisy to fly over people. It also burned a lot of fuel and was an expensive ticket. Approximately $15,000 for a round-trip seat in today’s dollars! That makes our wallets hurt.
Ok, so just build a new Concorde with new technology that saves fuel. Well, it’s really not that easy. Since 1973, supersonic flight over land has been forbidden in the United States because of the noise from sonic boom. A new supersonic commercial airplane needs to beat the boom problem and be efficient as well.
NASA has begun work to build an experimental aircraft to test theories on ways to reduce the “boom” to more of a muffled “thud”.
NASA selected a team led by Lockheed Martin Aeronautics Company of Palmdale, California, to complete a preliminary design for Quiet Supersonic Technology (QueSST). The work will be conducted under a task order against the Basic and Applied Aerospace Research and Technology (BAART) contract at NASA's Langley Research Center in Hampton, Virginia.
After conducting feasibility studies and working to better understand acceptable sound levels across the country, NASA's Commercial Supersonic Technology Project asked industry teams to submit design concepts for a piloted test aircraft that can fly at supersonic speeds, creating a supersonic "heartbeat" -- a soft thump rather than the disruptive boom currently associated with supersonic flight.
The preliminary artwork for the X-59 QueSST is pretty exotic-looking. Here’s a video from Lockheed Martin showing how the concept aircraft is shaping up.
If you think we’ve been here before, the Douglas X-3 Stiletto looks like somebody was anticipating developments.
If you are a fan of the assorted TV shows Gerry Anderson created, there were a number of exotic aircraft and spacecraft in those. The Angel Interceptor looks like another entry in the long-nosed aircraft family.
One problem with having that long nose out in front is how the pilot can see what’s in front of him — especially what’s in front and below when coming in for a landing. Delta wing aircraft typically call for a nose-high attitude on take off and landing as well, making it an even bigger problem.
The Concorde (and the ill-fated TU-144) got around that with a drooping nose for takeoff and landing. The X-59 is going to take a different approach: no forward view at all. Instead, it will be done with cameras and cockpit displays.
For those wondering why NASA is being tasked with developing this technology, it’s actually part of NASA’s mission. They are in the business of exploring new aviation technology and doing basic research. Whether or not it ever gets picked up by commercial interests, it still expands the pool of knowledge. On the scale of things in the aerospace world, the cost is relatively cheap.
Lockheed Martin will receive about $20 million over 17 months for QueSST preliminary design work. The Lockheed Martin team includes subcontractors GE Aviation of Cincinnati and Tri Models Inc. of Huntington Beach, California.
The company will develop baseline aircraft requirements and a preliminary aircraft design, with specifications, and provide supporting documentation for concept formulation and planning. This documentation would be used to prepare for the detailed design, building and testing of the QueSST jet. Performance of this preliminary design also must undergo analytical and wind tunnel validation.
A single F-35 costs between $94 million and $122 million. A single Boeing 737 MAX costs $99.7 million.
Depending on how the X-59 initial phase goes on the cost and engineering side, that will be a factor in funding the program for actual construction of an aircraft. It’s not a done deal yet.
So how soon will we be able to book a flight on a low-noise supersonic passenger aircraft? Don’t make any travel plans just yet. There are a number of other obstacles to overcome even if the X-59 does soften sonic booms into sonic thuds instead.
- Extended flight at supersonic speeds causes aircraft heating from air friction. Bigly. Major Kong’s look at the Speed of Heat — SR-71 Blackbird details some of the problems with heating, which is why they built them out of titanium. Concorde stretched 5-12 inches in flight just from the heating at cruise. (Details and temperature charts here.) Feel the burn...
- Noise is only one part of the problem. The other is fuel burn. Airlines are flying slower these days because holding fuel costs down is critical to making a profit. There’s a trade off between speed and money.
- Another is range. Concorde fell short because it couldn’t carry enough fuel to cross the Pacific non-stop, which would have been a prime market. (Putting new engines on B-52’s would have the effect of significantly increasing their range — because modern engines could give the same performance as old ones, but with burning a lot less fuel.)
- This makes engine design critical. The problem comes down to designing engines that can handle subsonic flight for take off and landing, and transition to supersonic flight for cruise — without needing massive amounts of fuel. (Again, see Major Kong for Blackbird engine details.)
- Add in greenhouse gas considerations and carbon footprints, and it gets to be an even tougher sell. There are bound to be protests against any proposals to put a new generation of SST’s into the air, on the basis of their environmental impact and the perception that they only problem they ‘solve’ is for the .1%. Could they fuel them with Hydrogen? That might be a partial answer, but a whole ‘nother set of issues.
- The final hurdle is this: even if all the pieces come together and all the challenges are met, none of it matters if the airlines won’t buy any airliners using this technology. If they don’t think they can make enough money with them — and it would have be a higher profit margin than with current subsonic aircraft — they are not going to gamble on buying them. People forget that the 747 was a huge gamble when it first flew, and the Airbus A-380 super jumbo is on the way out.
Does this make the X-59 a pointless dead-end project? No. Whether or not it leads to the commercial production of aircraft based on the technology they hope to develop, basic research is still useful in its own right. Further, NASA is good at taking projects like this and finding additional ways to put them to use. Whether or not it succeeds at finding ways to muffle sonic booms, an aircraft that can cruise at those speeds at those flight levels is bound to have other uses for research.
There’s a certain value in projects like this simply from putting people and resources to a challenge, because facing a challenge like this is comparable to regular exercise to stay healthy. And you never know what might be discovered along the way, or where else that pool of talent and skills might be of use.
Are there better places to spend money? Are there needs going unmet? Of course there are. There always are. Pitching it as an either/or choice is not necessarily the only way to frame this — and all too often cuts are just cuts. Those better places, those needs go unaddressed. The US saved money by not building the Superconducting Supercollider. There were originally going to be more Apollo missions. Is the US in a better place today because we made those cuts?
There are also worse places and things to spend money on than this too.
Let’s see what we can learn with the X-59. At worst we will be a little less ignorant. That’s a trend to encourage.