For space agencies and the commercial space industry, the priorities of the next two decades are clear. First, astronauts will be sent to the Moon for the first time since the Apollo Era, followed by the creation of permanent infrastructure that will allow them to say there for extended periods. Then, the first crewed missions will be sent to Mars, with follow-up missions every 26 months, culminating in the creation of surface habitats (and maybe a permanent base). To meet these objectives, space agencies are investigating next-generation propulsion, power, and life support systems.
This includes solar-electric propulsion (SEP), where solar energy is used to power extremely fuel-efficient Hall-Effect thrusters. Similarly, they are looking into nuclear thermal propulsion (NTP) and compact nuclear reactors, allowing for shorter transit times and providing a steady power supply for Lunar and Martian habitats. Beyond NASA, the UK Space Agency (UKSA) has partnered with Rolls-Royce to develop nuclear systems for space exploration. In a recent tweet, the international auto and aerospace giant provided a teaser of what their “micro-reactor” will look like.
It is an exciting time for astronomers and cosmologists. Since the James Webb Space Telescope (JWST), astronomers have been treated to the most vivid and detailed images of the Universe ever taken. Webb‘s powerful infrared imagers, spectrometers, and coronographs will allow for even more in the near future, including everything from surveys of the early Universe to direct imaging studies of exoplanets. Moreover, several next-generation telescopes will become operational in the coming years with 30-meter (~98.5 feet) primary mirrors, adaptive optics, spectrometers, and coronographs.
Even with these impressive instruments, astronomers and cosmologists look forward to an era when even more sophisticated and powerful telescopes are available. For example, Zachary Cordero of the Massachusetts Institute of Technology (MIT) recently proposed a telescope with a 100-meter (328-foot) primary mirror that would be autonomously constructed in space and bent into shape by electrostatic actuators. His proposal was one of several concepts selected this year by the NASA Innovative Advanced Concepts (NIAC) program for Phase I development.
Detecting exoplanets was frontier science not long ago. But now we’ve found over 5,000 of them, and we expect to find them around almost every star. The next step is to characterize these planets more fully in hopes of finding ones that might support life. Directly imaging them will be part of that effort.
But to do that, astronomers need to block out the light from the planets’ stars. That’s challenging in binary star systems.
The coming decades of space exploration will see astronauts return to the Moon, the first crewed missions to Mars, and robotic missions to the outer Solar System (among other things). These missions will leverage innovative technologies that allow faster transits, long-duration stays, and sustainable living far from Earth. To this end, NASA and other space agencies are investigating nuclear applications, especially where energy and propulsion are concerned. Many of these proposals have been on the books since the early space age and have been thoroughly validated.
On Tuesday, January 24th, NASA and the Defense Advanced Research Projects Agency (DARPA) announced they were launching an interagency agreement to develop a nuclear-thermal propulsion (NTP) concept. The proposed nuclear rocket is known as the Demonstration Rocket for Agile Cislunar Operations (DRACO), which would enable fast-transit missions to Mars (weeks instead of months). This three-phase program will culminate with a demonstration of the DRACO in orbit, which is expected to occur by early 2027.
Today, multiple space agencies are investigating cutting-edge propulsion ideas that will allow for rapid transits to other bodies in the Solar System. These include NASA’s Nuclear-Thermal or Nuclear-Electric Propulsion (NTP/NEP) concepts that could enable transit times to Mars in 100 days (or even 45) and a nuclear-powered Chinese spacecraft that could explore Neptune and its largest moon, Triton. While these and other ideas could allow for interplanetary exploration, getting beyond the Solar System presents some major challenges.
As we explored in a previous article, it would take spacecraft using conventional propulsion anywhere from 19,000 to 81,000 years to reach even the nearest star, Proxima Centauri (4.25 light-years from Earth). To this end, engineers have been researching proposals for uncrewed spacecraft that rely on beams of directed energy (lasers) to accelerate light sails to a fraction of the speed of light. A new idea proposed by researchers from UCLA envisions a twist on the beam-sail idea: a pellet-beam concept that could accelerate a 1-ton spacecraft to the edge of the Solar System in less than 20 years.
Tractor beams make intuitive sense. Matter and energy interact with each other in countless ways throughout the Universe. Magnetism and gravity are both natural forces that can draw objects together, so there’s sort of a precedent.
But engineering an actual tractor beam is something different.
We live in an era of renewed space exploration, where multiple agencies are planning to send astronauts to the Moon in the coming years. This will be followed in the next decade with crewed missions to Mars by NASA and China, who may be joined by other nations before long. These and other missions that will take astronauts beyond Low Earth Orbit (LEO) and the Earth-Moon system require new technologies, ranging from life support and radiation shielding to power and propulsion. And when it comes to the latter, Nuclear Thermal and Nuclear Electric Propulsion (NTP/NEP) is a top contender!
NASA and the Soviet space program spent decades researching nuclear propulsion during the Space Race. A few years ago, NASA reignited its nuclear program for the purpose of developing bimodal nuclear propulsion – a two-part system consisting of an NTP and NEP element – that could enable transits to Mars in 100 days. As part of the NASA Innovative Advanced Concepts (NIAC) program for 2023, NASA selected a nuclear concept for Phase I development. This new class of bimodal nuclear propulsion system uses a “wave rotor topping cycle” and could reduce transit times to Mars to just 45 days.
Solar power, long considered the leading contender among renewable energy sources, has advanced significantly over the past few decades. The cost of manufacturing and installing solar panels has dropped considerably, and efficiency has increased, making it price competitive with coal, oil, and fossil fuels. However, some barriers, like distribution and storage, still prevent solar power from being adopted more aggressively. In addition, there’s the ever-present issue of intermittency, where arrays cannot collect power in bad weather and during evenings.
These issues have led to the concept of space-based solar power (SBSP), where satellites equipped with solar arrays could gather solar energy twenty-four hours a day, seven days a week, three-hundred and sixty-five days a year. To test this method, researchers at the California Institute of Technology (Caltech) recently launched a technology demonstrator to space. It’s called the Space Solar Power Demonstrator (SSPD), which will test several key components of SBSP and evaluate the method’s ability to harvest clean energy and beam it back to Earth.
By the end of the decade, NASA plans to mount a total of six Artemis launches that will include crewed missions to the surface, the creation of the Artemis Basecamp, and the deployment of the Lunar Gateway. NASA also plans to upgrade key components in the mission architecture along the way, which include replacing the Space Shuttle Era engines with the newly-designed RS-25E. On December 14th, NASA tested this engine for the first time at the Stennis Space Center in Mississippi, completing a hot fire test that lasted for just under three and a half minutes (209.5 seconds).
To stand on a coastal shore and watch how eagles, ravens, seagulls, and crows take flight in high winds. it’s an inspiring sight, to be sure. Additionally, it illustrates an important concept in aerial mechanics, like how the proper angling of wings can allow birds to exploit differences in wind speed to hover in mid-air. Similarly, birds can use these same differences in wind speed to gain bursts of velocity to soar and dive. These same lessons can be applied to space, where spacecraft could perform special maneuvers to pick up bursts of speed from “space weather” (solar wind).
This was the subject of a recent study led by researchers from McGill University in Montreal, Quebec. By circling between regions of the heliosphere with different wind speeds, they state, a spacecraft would be capable of “dynamic soaring” the same way avian species are. Such a spacecraft would not require propellant (which makes up the biggest mass fraction of conventional missions) and would need only a minimal power supply. Their proposal is one of many concepts for low-mass, low-cost missions that could become interplanetary (or interstellar) explorers.