Aerospace Environmental Challenges for Electrical Insulation and Recent Developments for Electrified Aircraft

Abstract

The growing trend towards high voltage electrical assets and propulsion in the aeronautics and space industry pose new challenges in electrical insulation materials that cannot be overlooked. Transition to new high voltage electrified systems with unprecedented high levels of voltage, power, and efficiency must be safe and reliable. Improvements in both performance and safety of megawatt power systems is complicated because of the need for additional power transmission wiring and cabling and new safety requirements that have the potential of making the resulting systems heavier. To mitigate this issue, novel lightweight materials and system solutions are required that would result in lower specific weights in the insulator and conductor. Although reduced size and weight of system components can be achieved with new concepts, designs, and technologies, the high voltage (≥300 V) operation presents a significant challenge. This challenge is further complicated when considering the extreme operating environment that is experienced in aircraft, spacecraft, and targeted human exploration destinations. This paper reviews the extreme environmental challenges for aerospace electrical insulation and the needs associated with operating under high voltage and extreme environments. It also examines several recently developed robust lightweight electrical insulation materials that could enhance insulation performance and life. In aerospace, research must consider mass when developing new technologies. The impact of these recent developments provides a pathway which could enable next generation high altitude all electric aircraft, lightweight power transmission cables for a future sustained presence on the Moon and missions to Mars using HV propulsion, such as spacecraft with Nuclear Electric Propulsion systems.

Keywords: Micro-Multilayered Multifunctional Electrical Insulation (MMEI); aerospace electrical insulation; electrical insulation composites; extreme environments; hexagonal boron nitride (h-BN); high voltage.

Figure 1

Dielectric breakdown Paschen curves for various gases at room temeprature and 400 Hz.

Figure 2

NASA’s N3-X, Turboelectric blended wing body concept.

Figure 3

Concept of manned lunar observatory.

Figure 4

Glow from sodium in the lunar atmosphere.

Figure 5

Illustration concept of a Mars nuclear propulsion system with transit habitat.

Figure 6

Full-scale 1 m long, 3-phase bus bar prototypes manufactured with the (a) with manufacturer’s SOA insulation and (b) MMEI system targeting 10 MW at 20 kV. A reduction in the average insulation weight (−15%) and thickness (−12%) was seen for the NASA MMEI prototype compared to the manufactured bus bar.

Figure 7

Scanning electron micrograph of commercially available, as received boron nitride micronized platelets. Magnification, 4.50 kX, working distance (WD): 12.5 mm.

Figure 8

Weibull distribution plot of PPSU and PPSU/h-BN composites.

Figure 9

SEM micrographs of (a) commercial h-BN PT110, (b) h-BN PT110 intercalated with iron chloride, and (c) exfoliated h-BN (PT110).