Semiconductors in reusable launch vehicles must meet extreme operational demands, combining mechanical resilience, thermal stability, and computational reliability. The harsh conditions of spaceflight—high gravitational forces, rapid temperature fluctuations, and intense radiation—necessitate advanced materials and ruggedized designs. Silicon carbide (SiC) and gallium nitride (GaN) have emerged as critical wide-bandgap semiconductors for these applications, offering superior performance over traditional silicon in power electronics, propulsion control, and onboard computing systems.

High-G tolerance is a primary requirement for semiconductors in reusable launch systems. During ascent and re-entry, vehicles like SpaceX’s Starship experience accelerations exceeding 5 G, with localized forces potentially higher due to vibration and structural loads. Conventional silicon devices face delamination and interconnect fractures under such stress. SiC and GaN, with their higher mechanical strength and Young’s modulus, mitigate these risks. SiC’s hardness (9.5 Mohs) and fracture toughness (3.5 MPa·m¹/²) make it resistant to microcracking, while GaN’s epitaxial growth on robust substrates like sapphire enhances structural integrity. Packaging innovations, such as direct-bonded copper (DBC) substrates and compliant interconnects, further improve high-G survivability.

Rapid thermal cycling presents another challenge. Launch vehicles endure temperature swings from cryogenic propellant conditions (-253°C for liquid hydrogen) to re-entry heating exceeding 1,500°C at leading edges. While semiconductors are shielded from extreme external temperatures, internal systems face cycles between -40°C and 125°C. SiC’s thermal conductivity (490 W/m·K for 4H-SiC) outperforms silicon (150 W/m·K), reducing hotspots in power modules. GaN’s high electron mobility (2,000 cm²/V·s) maintains efficiency under thermal stress, critical for high-frequency switching in motor drives. Thermal expansion mismatch is addressed through advanced packaging, such as silver-sintered die attach and alumina-ceramic substrates, which minimize fatigue during repeated cycling.

Fault-tolerant computing is essential for mission-critical avionics. Single-event upsets (SEUs) from cosmic radiation can disrupt conventional silicon CMOS logic. Radiation-hardened designs employ SiC and GaN for their inherent resistance to displacement damage, with SiC’s threshold displacement energy (21 eV for carbon sublattice) being three times higher than silicon’s. Triple modular redundancy (TMR) and error-correcting code (ECC) memory are implemented in onboard FPGAs and processors to ensure computational integrity. SiC-based power devices also enable distributed fault-tolerant architectures, where localized failures in one thruster or power converter can be isolated without cascading system collapse.

Cost-effective reusability drives material and design choices. SiC and GaN devices, though initially more expensive than silicon, reduce lifecycle costs through higher efficiency and durability. A SiC MOSFET’s lower switching losses (up to 80% reduction compared to silicon IGBTs) decrease cooling demands, simplifying thermal management systems. GaN’s ability to operate at higher frequencies (MHz range) allows for smaller passive components, reducing vehicle mass—a critical factor in launch economics. Ruggedized IC designs, such as monolithic integration of drivers and power stages, minimize failure points and streamline maintenance between flights.

In propulsion systems, SiC inverters control electric pump-fed engines with precision, handling peak currents exceeding 1,000 A. GaN RF amplifiers enable high-data-rate telemetry during ascent and descent, surviving the vibrational noise of engine ignition. For sensors, radiation-hardened SiC photodiodes monitor engine plume characteristics, while GaN-based MEMS accelerometers provide high-G trajectory data.

The shift toward reusable launch vehicles demands semiconductors that exceed traditional aerospace standards. SiC and GaN meet these needs with inherent material advantages, while system-level innovations in packaging, fault tolerance, and integration ensure reliability across multiple missions. As flight rates increase, the economic case for these technologies strengthens, positioning them as foundational to the next generation of space transportation.