The Quiet Revolution: Why Electric Propulsion Matters for Suborbital Flight

Space tourism is no longer a distant fantasy. Companies like Blue Origin and Virgin Galactic have already flown private passengers to the edge of space aboard suborbital vehicles. But these early trips rely on traditional chemical rockets—powerful, loud, and environmentally taxing. As the industry matures, a quieter, more efficient technology is gaining traction: electric propulsion. While still emerging for suborbital applications, electric propulsion offers a path to lower costs, cleaner operations, and more flexible flight profiles. This article explores how electric propulsion works, why it is a game-changer for suborbital space tourism, and what hurdles remain before it becomes standard.

Understanding Electric Propulsion: From Ion Thrusters to Hall-Effect Engines

Electric propulsion is not a single technology but a family of systems that use electrical energy to accelerate propellant. Unlike chemical rockets that produce thrust by burning fuel and oxidizer in a combustion chamber, electric thrusters generate thrust by ionizing a gas (typically xenon or krypton) and accelerating the ions using electric or magnetic fields. The result is a very high exhaust velocity, which translates to a high specific impulse (Isp)—a measure of fuel efficiency. Common types include:

  • Ion thrusters: Ions are accelerated through a series of grids using a high-voltage electric field. Known for extremely high Isp (up to 10,000 seconds), they produce low thrust but are very fuel-efficient.
  • Hall-effect thrusters: A magnetic field traps electrons, which then ionize neutral gas. The ions are accelerated by an electric field. These offer a middle ground between thrust and efficiency.
  • Pulsed plasma thrusters (PPTs): Use a solid propellant (like PTFE) that is ablated and accelerated by a pulsed electric discharge. Simple and compact but low efficiency.
  • Electrospray thrusters: Use ionic liquids accelerated through fine nozzles. Emerging technology with potential for micro-thrust applications.

For suborbital vehicles, Hall-effect thrusters and ion thrusters are currently the most promising candidates due to their balance of efficiency, maturity, and scalability.

Why Electric Propulsion for Suborbital Tourism? Key Advantages

Radical Efficiency Gains

The most compelling advantage is specific impulse. A typical chemical rocket engine achieves an Isp of about 300–450 seconds. Electric thrusters can reach 1,500–5,000 seconds, meaning they can produce the same total impulse using far less propellant. For suborbital tourism, this translates to significantly lower fuel mass, reducing the overall vehicle weight and launch costs. With less propellant to carry, the vehicle can be smaller, lighter, and potentially reusable—key factors for any commercial space tourism business.

Environmental Benefits: Cleaner Flights

Chemical rockets burn propellants that release carbon dioxide, water vapor, soot, and other pollutants into the upper atmosphere. While the total emissions from suborbital flights are still small compared to aviation, the industry is under scrutiny as it scales. Electric propulsion uses inert gases like xenon, which produce no combustion byproducts. The main environmental impact comes from manufacturing the propellant and generating the electricity used to power the thruster—both of which can be sourced from renewable energy. This positions electric propulsion as a greener alternative, aligning with growing demand for sustainable travel.

Lower Operating Costs Through Reusability and Reduced Refurbishment

Chemical rockets experience extreme heat, pressure, and vibration during combustion, which causes significant wear and tear on engine components. Electric thrusters operate at much lower temperatures and without high-pressure combustion, greatly reducing thermal and mechanical stress. This means the propulsion system can last for many more flights before needing major refurbishment—critical for the cost-per-seat model of space tourism. Additionally, the simplicity of electric thrusters (fewer moving parts) translates to simpler ground operations and quicker turnaround times.

Extended and Customizable Flight Profiles

Suborbital flights typically follow a ballistic trajectory: a powerful boost, a few minutes of weightlessness, then reentry. With chemical rockets, thrust duration is short and the trajectory is largely fixed by the burn profile. Electric propulsion, while low-thrust, can sustain thrust for much longer periods (minutes to hours). This could enable new mission profiles such as sustained microgravity experiments, gradual ascents that reduce g-forces on passengers, or even controlled descent maneuvers. Tourism operators could offer longer, more valuable flight experiences.

Safety & Redundancy

Electric propulsion systems are inherently less explosive than chemical ones. There is no high-pressure combustion chamber, no volatile oxidizer. Xenon is inert and non-flammable, reducing risk on the ground and in flight. Multiple small thrusters can be distributed for redundancy, allowing graceful degradation of propulsion capability instead of catastrophic failure.

The Major Challenge: Low Thrust and the Power Problem

Despite these advantages, electric propulsion has a fundamental limitation: low thrust. A typical Hall-effect thruster produces thrust measured in millinewtons to a few newtons, compared to hundreds of kilonewtons for a chemical rocket. To overcome Earth's gravity and reach suborbital altitudes (typically 80–120 km), a vehicle must accelerate rapidly. With low thrust, the acceleration is very slow, making direct liftoff from the ground impossible. This is why electric propulsion is currently used mainly in space for orbital maneuvers, not for launch.

Power Source Constraints

Electric thrusters require large amounts of electrical power—usually tens to hundreds of kilowatts for suborbital-scale thrust. For a space tourism vehicle, this power must come from on-board batteries or solar panels. Batteries capable of delivering megawatts for minutes are extremely heavy, negating some of the weight savings from reduced propellant. Solar panels are less effective in the lower atmosphere and add drag. Researchers are exploring high-energy-density batteries (e.g., lithium-air, solid-state) and supercapacitors to bridge this gap.

Acceleration Time and G-Forces

Even if the power problem is solved, the low thrust means long acceleration times—potentially tens of minutes to reach orbital velocities (though suborbital requires less delta-v). During that time, passengers would experience sustained low g-force acceleration (maybe 0.1–0.5 g) rather than the brief high-g of chemical rockets. This could be more comfortable for some, but it also means the vehicle must spend much longer in the denser parts of the atmosphere, increasing aerodynamic heating and drag. Trajectory optimization is needed.

Propellant Management

Xenon is expensive (about $2,000/kg) and relatively scarce. For commercial tourism, using cheaper alternatives like krypton or even iodine is being investigated. Iodine can be stored as a solid and sublimated, offering higher density and lower cost, but it is corrosive and requires special handling.

Hybrid Solutions: The Best of Both Worlds

Given the low-thrust limitation, many experts believe the most viable path is a hybrid propulsion system. A small chemical rocket (solid or liquid) provides the high thrust needed for initial launch and ascent through the lower atmosphere. Once the vehicle reaches the stratosphere (~30–50 km altitude), the chemical engine shuts down and an electric propulsion system takes over for the remainder of the ascent and for sustained microgravity maneuvers. This approach reduces the chemical propellant mass (still the main weight driver) while allowing the efficiencies of electric propulsion where it works best: in near-vacuum conditions. Reusability is enhanced because the chemical engine operates for only a short duration. Such a hybrid could dramatically reduce operating costs compared to all-chemical vehicles.

Current Research and Development Efforts

Several organizations are pushing the boundaries of electric propulsion for suborbital and small launch vehicles:

  • NASA Glenn Research Center continues to develop advanced Hall-effect thrusters with higher power levels and greater durability. Their High Power Electric Propulsion (HiPEP) program has tested thrusters up to 50 kW. (Source: NASA Solar Electric Propulsion)
  • The European Space Agency (ESA) is funding studies on "air-breathing" electric propulsion, which could scoop atmospheric gas as propellant for very low orbital flight—potentially applicable to suborbital loitering.
  • Private companies like Phase Four have developed RF (radio-frequency) thrusters that are more compact and have no eroding electrodes, improving lifetime. Their Maxwell thruster is being considered for small satellite and suborbital demonstration missions.
  • The University of Tokyo and Japanese space agency JAXA have demonstrated a pulsed plasma thruster designed for microsatellite station-keeping, but scaling it for suborbital use is early-stage.
  • Startups like Exotrail and ThrustMe are commercializing low-power electric thrusters for CubeSats, but are also exploring high-power variants for future space tugs that could support suborbital tourism infrastructure.

One notable project is the Launcher Orbiter (now part of Vaya Space) which proposed using a hybrid chemical/electric propulsion architecture for a small launch vehicle. While that company pivoted, the concept remains active in engineering circles.

Battery Technology Breakthroughs

Critical to electric propulsion's success are advances in energy storage. The specific energy of lithium-ion batteries is around 250 Wh/kg. For a suborbital vehicle needing 10,000 kWh for a 10-minute ascent, battery mass alone would be 40,000 kg—clearly too heavy. Emerging battery chemistries like lithium-sulfur (500–600 Wh/kg) or lithium-air (theoretically 3,000 Wh/kg) could reduce that to a few thousand kilograms. Solid-state batteries promise higher safety and energy density. Additionally, supercapacitors can deliver very high power for short bursts, potentially supplementing batteries for the initial acceleration phase.

Another approach is wireless power beaming from ground-based microwave or laser transmitters. This is highly speculative but would allow the vehicle to carry no power source, only receivers, dramatically reducing weight. The concept is being researched by NASA and others for high-altitude UAVs and could be adapted for suborbital tourism.

Economic Viability: Can Electric Propulsion Lower Ticket Prices?

Current suborbital flights cost $250,000–$500,000 per seat. The goal of electric propulsion advocates is to reduce that to under $50,000 per seat, potentially expanding the market from ultra-wealthy individuals to a broader demographic. The cost drivers for chemical rockets are high propellant mass (expensive fuel), short engine life (many need rebuilding after each flight), and complex ground operations. Electric propulsion directly addresses all three:

  • Propellant cost per flight could drop by 80% or more.
  • Engine life could be measured in thousands of hours instead of seconds.
  • Simpler engines reduce maintenance and inspection time.

However, the upfront development cost of high-power electric propulsion systems is substantial. And the need for large battery packs or advanced solar arrays adds initial expense. As battery costs continue to fall (following the EV industry curve), the total system cost will become more competitive. A 2022 study by the International Space Society estimated that a hybrid electric suborbital vehicle could reach break-even at around 50 flights per year, assuming $100,000 per seat. With proper scaling, ticket prices could drop to $30,000 by 2035.

Regulatory and Safety Considerations

The Federal Aviation Administration (FAA) Office of Commercial Space Transportation regulates suborbital flights. Currently, there are no specific standards for electric propulsion systems in passenger-carrying vehicles. The FAA will need to develop certification frameworks for these novel engines, addressing failure modes like electrical arcing, thruster erosion, and thermal management in the vacuum of space. Passengers must be safe from high-voltage components and radiation. The inert propellant eliminates explosion risk but introduces other hazards like high-pressure gas storage and potential leaks. Public acceptance will also depend on demonstrating reliability through many unmanned test flights.

Future Outlook: Roadmap to Electric Suborbital Tourism

It is unlikely that a fully electric suborbital vehicle will carry passengers within the next decade. The power density required for direct liftoff is simply not there yet. But a hybrid electric suborbital vehicle could be flying test flights by 2030. The likely progression:

  1. Phase 1 (2025–2028): Electric propulsion is used for in-space maneuvering of the passenger capsule after chemical launch. Allows longer microgravity and flexible trajectories.
  2. Phase 2 (2028–2032): Improved batteries enable electric thrust to partially replace chemical thrust during ascent, reducing fuel consumption.
  3. Phase 3 (2032–2035): High-power electric thrusters with advanced power sources allow a nearly all-electric ascent, with only a small chemical booster for initial kickoff.
  4. Phase 4 (2035+): Fully electric suborbital vehicles capable of vertical takeoff using electric thrust alone, assuming breakthroughs in energy storage and thruster scaling.

This timeline is aggressive but possible if battery R&D accelerates and commercial space tourism continues to grow. Companies like Lilium (urban air mobility) and Archer Aviation are advancing high-power battery systems for eVTOL aircraft, which could cross-pollinate with suborbital propulsion.

Conclusion

Electric propulsion represents a long-term strategic shift for suborbital space tourism. Its ability to drastically improve fuel efficiency, reduce environmental impact, lower operating costs, and enable new flight profiles makes it an irresistible target for researchers and entrepreneurs. The main barriers—low thrust and heavy power sources—are being steadily addressed by parallel advances in battery technology and high-power thruster design. While fully electric suborbital launch remains a future goal, hybrid systems are already within reach and could begin reshaping the economics of space tourism within a decade. For the industry to achieve its promise of making space accessible to thousands, electric propulsion is not just an option; it is likely a necessity. Continued investment and cross-sector collaboration will be the keys to turning this quiet revolution into the roar of a new era in space travel.