Inside of an unassuming recycled shipping container in Maryland might sit the very future of interstellar travel.
Scientists at the Johns Hopkins University Applied Physics Laboratory are performing experiments on whether the extreme heat of our sun can power a spacecraft to the far reaches of our solar system and beyond… interstellar space.
The seeds for this spacecraft are being planted in a shipping container. A wall of the shipping container is lined with thousands of LEDs, and a metal latticework system runs down the center. A black curtain covers part of the device. A small black and white tile is mounted onto the latticework, and a dark curtain is laced around the experiment. Once the LED lights are switched on, they can shine brighter than 20 times our own sun and become extremely hot.
The scientists then pump liquid helium through a small embedded tube, and the helium absorbs the heat from the LEDs, and winds through the latticework, and expands until it’s finally released through a small nozzle. And just like that, what was a theoretical idea that had its origins in 1956, becomes a reality.
Jason Benjoski, a materials scientist at the Applied Physics Laboratory, explained the scientific breakthrough: “What this is showing is that solar thermal propulsion is not just fantasy.”
Designing the Ship
Traditional combusting fuel spaceships have two fundamental issues: speed limitations and supply. How do you get to the edge of the solar system as fast as you can without running out of fuel?
Solar propulsion might be the answer.
The theory behind solar propulsion is that it is powered by a solar thermal engine that gathers hydrogen from the sun and heats it before expelling it out of a nozzle to generate thrust.
The only problem? You have to get really close to the sun.
The spacecraft would have to do like Icarus, but without being burned by the sun. It would have to be extremely close to the sun to gain the required speed—anywhere between 30,000 and 200,000 mph—without melting.
The spacecraft would have to pull off an Oberth maneuver, essentially turning the sun into a giant slingshot. For those that have seen the movie Interstellar, the maneuver works in much the same way that it did for the Endurance spacecraft in the movie. The spacecraft used the gravity of the massive black hole Gargantua to propel it back home.
The solar thermal rocket would use the sun’s gravity as a force multiplier and will pick up massive amounts of speed as it fires its engines racing around the star. The closer it gets to the sun, the faster it will go. APL’s mission design has the probe passing just a million miles from the surface of the sun.
NASA’s Parker Solar Space Probe will achieve some of these gravitational speed boosts. Parker will make its closest approach to the sun in 2025—at 4 million miles from the sun’s surface—and traveling at nearly 430,000 miles per hour. The probe will have received gravity assists from the Sun and Venus over the course of seven years.
The heat is the biggest issue the Interstellar solar probe needs to overcome. For the APL mission, the probe would spend around two-and-a-half hours in temperatures approaching 4,500 degrees Fahrenheit as it completed its Oberth maneuver. That’s enough heat to melt through Parker’s heat shield.
Looking to the stars
NASA has its sights set beyond Mars and towards interstellar space. To get there, they have to do it faster and more efficiently.
Voyager 1 and Voyager 2 are the only manmade spacecraft to reach the limits of interstellar space. However, at 30,000 miles per hour, it took nearly half a century to get there.
That is why NASA is working with scientists at the Applied Physics Laboratory to find new ways to propel spacecraft at much faster speeds. NASA formed the partnership a little over a year ago in October 2019, claiming that such a mission could be launched as soon as 2030.
New solar systems, planets, and perhaps even life exist beyond the confines of our solar neighborhood—we just have to get there.
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