In October 2021, NASA and GE Aviation announced a new partnership to mature a megawatt-class hybrid electric engine that could power a single-aisle aircraft. Three months later, they announced Boeing's involvement in the project, specifically the propulsion system testing.
This example - a five-year, $260 million effort - demonstrates the prioritization and collaboration around electrification in aviation and aerospace. Both industry pillars and rising startups are making significant commitments and investments in this area.
But as with any major undertaking, sustainability in aerospace presents significant challenges to engineers. Let’s walk through the key drivers of sustainable fuels in aerospace, major challenges, and how companies can respond.
Aviation and aerospace is one of the fastest growing sources of greenhouse gas emissions, which is causing major damage to our climate.
In response, the aviation industry has set ambitious targets to reduce greenhouse gas emissions by 2050. There are a number of options available to hit those targets:
According to the World Economic Forum, sustainable fuels and carbon offsetting are the tactics most likely to help reach those goals. In that same vein, Boeing CEO David Calhoun has stated that the pressure to invest in unproven technologies - like electrification - is unfounded. Instead, he advocates for mass production of sustainable aviation fuel.
However, this may be because electrification is in its infancy, and needs more time to develop to meet the climate targets. The faster engineers can overcome obstacles and drive the necessary innovations, the more feasible electrification will be as a solution to the climate crisis.
Given the need for broader, more transformational objectives to avoid global catastrophe, aerospace companies cannot afford to hedge on a single solution. While SAFs are a great first step, electrification is another tool in our climate-fighting belt.
In addition to the partnership among NASA, GE, and Boeing mentioned earlier, many other companies are pursuing electrification:
The key takeaway here: there are many successful (and some not so successful) startups in the field of aerospace electrification. However, despite major investments, the challenges faced by this sector still stand.
Companies who adopt new engineering processes will be able to overcome these obstacles faster. Given the opportunity in the market, a company who makes the right moves could soon find themselves a leader in the market.
Most challenges that companies face while trying to meet their aviation sustainability goals come down to a core issue: carrying enough power on board to fulfill the mission objectives.
The problem with most of the solutions is that they, in effect, reduce the operational design domain (ODD) of electric aircraft, rather than design a system that fits the standard use case.
To overcome these challenges, aerospace need to adopt new engineering processes that streamline the development, testing, and iteration cycle. This, in turn, will lead to more efficient innovation, which will solve the actual problems at hand.
The biggest technological challenge in aircraft electrification is battery power density, which is 4-10 times lower than what is needed for a typical all-electric regional commuter aircraft. For long-haul commercial flights, the gap is even greater.
The power density of aviation fuel is typically 43-48 MJ/kg, or approximately 40MJ/kg if fuel tanks and fuel handling are included. By comparison, in state of the art battery technology today, power density is around 1 – 1.1 MJ/kg.
This power density allows for short-range, sub-regional civil aviation. One example is electric vertical takeoff and landing (eVOTL). Several companies are exploring this option including Vertical Aerospace's “VX4”, Beta's “ALIA-250” and Wisk's “Cora.”
Modern aerospace platforms require more sophisticated capabilities to fulfill mission requirements, whether in civil or defense scenarios. These include more advanced avionics, navigation, communication, sensors, and identification tools.
These capabilities are powered by the electrical and electronic systems. Over the last 30 years, these systems have increased the electrical power demand of aircraft tenfold.
One potential solution to this problem is the use of integrated modular avionics (IMA), which distribute processing among multiple computing modules. This reduces the number of independent processing units, using less power.
Compared to automotive, aerospace has much stronger safety and compliance requirements - rightfully so. A plane that loses power mid-flight will cause major issues, compared to a vehicle that loses power on the ground.
DO-178, DO-278 and DO-330 standards are commonly followed across the industry. DO-178C provides guidance for the development of software used in airborne systems. DO-278 provides guidelines for the development of software used in communication, navigation, surveillance, and air traffic management systems. DO-330 provides guidance for the development and qualification of software tools used in the development and verification of safety-critical aviation systems.
As engineers experiment with electric power in aviation, they have to run a large number of scenarios and testing to accrue the data necessary to determine battery capabilities and pass the above certifications.
Until now, renewable energy has been handled entirely in the context of hydrocarbon technology. While electric power is familiar in the context of consumer electronics, there are many unknowns when it comes to air power - not the least of which are battery capacity, weight, and other factors.
Figuring out the trade-off between hydrocarbon energy and electric energy requires a large number of simulations. Engineers need to experiment with varying speeds, locations, and environments.
Companies who adopt model-based engineering processes place themselves as a unique advantage over competitors: