Supersonic flight is the stuff of dreams. Perhaps you know someone that is (or was) a fighter pilot, or a lucky passenger on a Concorde flight. NASA, along with many large corporations with vast resources, are trying to reignite the next commercial supersonic era.
I’ll talk a bit about what’s going on today and the big plans of one major player in supersonic flight. As many of you know, the biggest hurdle to supersonic flight is the current regulation against flying faster than the speed of sound over land due to the sonic boom that is created for those on the ground. The sonic boom is not heard by the occupants of the aircraft.
NASA and Lockheed Martin are developing an aircraft capable of reaching supersonic speed without creating the sonic boom of past aircraft. The experimental plane has entered production and is called the X-59 Quesst with two ‘S’s for Quiet Supersonic Technology. The aircraft flies at 55,000 feet and can reach speeds of about 940 miles per hour or Mach 1.4. The aircraft’s sonic boom is expected to create a noise level like the sound of a car door closing.
One of the goals of the program is to change the regulations to allow supersonic flight over land. The X-59 will be flown over US cities to collect data on how communities respond to the sound. NASA is hoping to establish an acceptable commercial supersonic noise standard to overturn current regulations banning supersonic flights over land. The first flight of the X-59 is scheduled for 2021.
Other countries have announced plans to develop experimental aircraft to test the reduction of the sonic boom. These include Japan and Russia.
This is non-business jet related but very cool all the same: Lockheed Martin is also in the process of developing the SR-72, a hypersonic unmanned plane dubbed the “son of the Blackbird.” I Googled hypersonic and its definition: an aircraft travelling at more than five times the speed of sound or Mach 5. In 1976, the Air Force flew Lockheed Martin’s SR-71 Blackbird from New York to London in less than two hours at speeds in excess of Mach 3. The SR-72 is planned to operate at speeds up to Mach 6. And while the hypersonic SR-72 isn’t expected to be operational until 2030, the company and the US military sees the SR-72 platform as a massive tactical advantage.
So I mentioned that current regulations ban commercial supersonic aircraft from operating over land. New companies like Boom Supersonic are developing test aircraft and flying them next year. And they have big money backers like Richard Branson and Japan Airlines who have placed orders for their supersonic airliners. According to the Boom Supersonic website they have a two-seat test aircraft and plan to build a passenger aircraft for airline operations.
What about business jets?
Aerion is a supersonic business jet manufacturer and their business jet is called the AS2. There is industry support as Flexjet placed an order for 20 Aerion AS2s in 2016. The rules against flying at greater than supersonic speeds over land are holding back development, and probably some interest, as having to slow down over land, no matter how efficient the aircraft is at slower speeds, is simply a waste of the supersonic technology. These aircraft are very expensive as well. A true supersonic business jet ought to be able to fly supersonic from shortly after takeoff to just before landing.
Some are advocating for supersonic flight above a certain altitude over land to minimize the sound on the ground. The aircraft could then slow down in descent to below Mach 1 above a certain altitude to prevent ground disturbance.
This is a quote from NASA, “Altitude determines the distance shock waves travel before reaching the ground, and this has a significant effect on intensity. As the shock cone gets wider, and it moves outward and downward, its strength is reduced. Generally, the higher the aircraft, the greater the distance the shock wave must travel, reducing the intensity of the sonic boom.”
NASA also pointed out that “increasing speeds above Mach 1.3 results in only small changes in shock wave strength.” This points to the benefits of designing super sonic business jets that can fly much faster than the Mach 1.4 as the sonic disturbance is not increased greatly.
Let’s talk about the airplane that some of our listeners may get a chance to fly…
The most advanced supersonic project may be the Aerion AS2 that I mentioned before. This is the first privately built supersonic commercial aircraft ever.
Much of this information is from the Aerion website and it’s pretty exciting: The AS2 will have a Mach 1.4 supersonic cruise. The aircraft will fly at the fastest sub-sonic cruise of any jet ever at Mach 0.95. It has a luxurious cabin as you would expect for the $120 million price tag. It has global range but Aerion doesn’t have a a range listed. Aerion says that their operation is carbon-neutral but are a bit vague on how they will achieve this.
While we are on the subject of environmental…
Aerion says that they are the first aircraft OEM to commit to a goal of carbon neutrality. This commitment has led their design to a lot of firsts:
- The AS2 is the first supersonic aircraft designed without an afterburner,
- The AS2 is the first supersonic aircraft designed with the ability to accept 100% biofuels as opposed to blends,
- Aerion says they are the first OEM to plan for truly carbon-neutral operations via carbon reduction strategies, not just financial offsets.
So they mentioned no afterburner. What engine are they using?
GE is developing the new engine for the AS2 and they call it the Affinity. They have a cool video on the Aerion website but in a nutshell…
- It has a carbon fibre casing, new exhaust, and a two-stage fan.
- The Affinity is classed as a medium-bypass-ratio engine.
- The engine is controlled by a next-generation full authority digital engine control or ‘FADEC’.
Aerion wants to sell this aircraft if the supersonic noise rules change or not so it is designed to enable efficient supersonic flight over water and efficient subsonic flight over land. GE says the Affinity engine provides performance across subsonic, transonic, and supersonic speeds.
Aerion talks about Boomless Cruise on their website, what’s that?
The Aerion website says it will be the first commercial aircraft to fly at supersonic speeds over land with no noise on the ground. This is a bold statement considering NASA and Lockheed are developing their X-59 aircraft that will reduce the sonic boom, not eliminate it. Aerion says it’s all in the aircraft design and the incredibly efficient supersonic engine from GE called the Affinity.
Aerion goes on to say that BOOMLESS CRUISE™ technology is possible at speeds approaching Mach 1.2, depending on atmospheric conditions like air temperature and wind. Aerion is currently working with certifying authorities to approve “boomless” cruise capability.
What about the Flight Deck?
The AS2 will have an advanced version of Honeywell’s Primus Epic avionics system. Honeywell Primus Epic avionics are widely used today, and Honeywell products have been part of thousands of supersonic military jets for decades.
So with all this high tech how long will it take to fly places??
There are many examples on the Aerion website but here’s two:
- A flight from LAX to JFK, which is 2150 NM would save 1:25 in the AS2 and make the trip in 3:17.
- A flight from JFK to Cape Town, South Africa which is almost 6800 NM would save 3:39 and make the trip in just under 10 hours.
There are many hurdles to overcome but we are on the verge of passenger flights to space, so it seems anything is possible.
OK aviation professionals let’s change gears for a moment…
In the news is a segment of the podcast where I talk about other happenings in aviation. SAFO 19003 released a few months back warns operators and pilots about braking distance on wet and contaminated runways. Overruns have occurred when the crew has used the correct advisory data for wet runway landings, but a safe stopping distance was not achieved in conditions of moderate or heavy rain. TALPA defines WET as “Includes damp and 1/8-inch depth or less of water,” while CONTAMINATED is “greater than 1/8-inch of water.”
Overruns have occurred on grooved and smooth runways during periods of moderate to heavy rain. Analysis of the occurrences indicates that the braking coefficient of friction in each case was significantly lower than expected, and that 30 to 40 percent of additional stopping distance may be required if the runway transitions from wet to contaminated. The pilot must determine whether the runway is wet or contaminated.
Also consider that an airport may not be able to generate a Field Condition NOTAM or ‘FICON’ for sudden rain showers that results in water on the runway of more than 1/8 of an inch in depth which makes the surface contaminated. Rainfall intensity may be the only indication available to the pilot that the water depth could be greater than planned. The SAFO is a good read and reminder to get into the books so when conditions change in the descent you can calculate a new landing distance and make a plan.
That’s our podcast for today. Thanks for listening and have a great day.
AINsight: The Need for $peed by Matt Thurber