Key Takeaways:

  1. Solar thermal propulsion offers a promising alternative to traditional rocket engines, harnessing the sun’s heat for power.
  2. The experimental engine uses a flat shield made from black carbon foam, acting as both an engine and a heat shield.
  3. Coils of tubing filled with hydrogen absorb heat from the sun, creating pressurized thrust for propulsion.
  4. This technology could potentially be three times more efficient than current advanced chemical combustion engines.
  5. Engineers aim to develop a probe capable of traveling three times farther than the outer heliosphere within two decades, a distance of 50 billion miles.

Space exploration is on the verge of a groundbreaking transformation thanks to the innovative work of engineers at the Johns Hopkins University Applied Physics Laboratory.

They are in the process of bringing to life a once-theoretical rocket engine design that could potentially propel spacecraft to interstellar destinations. The concept behind this visionary engine is harnessing the sun’s heat, as opposed to traditional combustion, to generate the required thrust for propulsion.

This revolutionary solar-powered engine deviates from conventional rocket engines, taking the form of a flat shield constructed from black carbon foam. In addition to its role as an engine, this shield offers crucial protection against the sun’s intense radiation.

Below the surface, a network of tubing holds hydrogen, which absorbs solar heat, causing it to expand and pressurize. The resulting explosion of hydrogen through a nozzle generates the necessary thrust, a concept aptly named solar thermal propulsion.

Jason Benkoski, a materials scientist at the Applied Physics Laboratory, expresses his confidence in the efficiency of this system, highlighting its potential superiority from a physics standpoint. According to his calculations, the real-world application of this engine could be three times more efficient than the most advanced chemical combustion engines currently in use.

interstellar travel concept
Jason Benkoski/APL

In 2019, NASA joined forces with APL to initiate the Interstellar Probe study, aiming to identify missions for the next decade that delve into the realms beyond our sun’s immediate influence. Defining the boundary between our solar system and interstellar space remains a subject of scientific debate, but one measurable metric is the heliopause, where the sun’s magnetic fields and solar winds can no longer be detected.

APL’s ambitious objective is to develop a probe capable of traversing three times the distance from the heliosphere’s outer limits within a mere two decades—an astounding 50 billion miles. To put this into perspective, consider the current record holder, Voyager 1. Launched in 1977, it has traveled over 14 billion miles from Earth and is hurtling at a speed of 38,000 miles per hour.

oberth maneuver
Creative Commons

The APL team aspires to surpass this record by accelerating their spacecraft to an incredible 200,000 miles per hour and accomplishing the journey in half the time. However, this endeavor entails a significant feat: executing an Oberth maneuver a mere million miles from the sun’s fiery surface. This maneuver, named after rocketry pioneer Hermann Oberth, exploits a celestial body’s gravitational pull to further accelerate a spacecraft’s descent into a gravitational well.

This approach is akin to building momentum downhill for an uphill climb. The closer one gets to a massive gravitational body like the sun, the more potential energy can be harnessed. Yet, this comes with the challenge of contending with extreme heat. In 2025, NASA’s Parker Solar Probe is slated to make its closest approach to the sun, braving temperatures of up to 2,500 degrees Fahrenheit within 4 million miles of the sun’s surface.

For APL’s probe to venture within a million miles of the sun, it must endure temperatures of around 4,500 degrees Fahrenheit for a staggering 2.5 hours during its Oberth maneuver. To shield against this formidable heat, NASA is exploring novel materials that could coat the spacecraft and effectively deflect the sun’s intensity. Moreover, the hydrogen coursing through the heat shield may act as a radiator, displacing thermal energy as propellant.

Jason Benkoski’s team at APL is poised to present a comprehensive report on their experimental rocket design findings in the coming year, offering a promising glimpse into the future of space travel.

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