The Week in Space and Physics
The Week in Space and Physics
On exploring the ice giants, Europe's power woes, spaceplanes and a private flight to Venus
Once every two centuries the giants of the Solar System fall into alignment. A single probe, bouncing off each like a pinball, can then visit all four in a single trip: ricocheting from Jupiter to Saturn; to Uranus and then to Neptune.
Such an alignment last came to pass in the late 1970s, an event NASA sought to exploit with the Voyager missions. The attempt was an outstanding success: the two probes returned reams of data from the outer Solar System before heading into the interstellar void.
Yet, almost half a century after their visit, no other probe has followed them to Uranus or Neptune. The two ice giants remain mysterious places: driven by processes we barely understand and surrounded by unexplored moons.
That’s a shame. Similar planets are probably common in the Milky Way, and exploring them could reveal much about worlds in other solar systems. Their moons, too, are fascinating: icy worlds scarred and cracked by a turbulent past. Perhaps time, then, to send another probe to explore these worlds.
NASA seem to agree – last week they signalled approval of a report calling for the agency to send a spacecraft to Uranus. As conceived, the probe would spend years orbiting Uranus, exploring its atmosphere, rings and satellites. It would pay close attention to Uranus’ moons – especially the pair known as Ariel and Miranda.
Both have rugged and complex surfaces; scarred by canyons a dozen times deeper than the Grand Canyon and home to cliffs tens of miles high. Though small - far smaller than our Moon - they seem surprisingly active; marked by erupting volcanoes and shifting ice sheets.
Interest in such icy moons has been growing over the past decades. Researchers have realised that many are warmer than they look, heated by the intense gravity of their parent planets. That could imply oceans of liquid water sit towards their cores; water perhaps warm enough for life to thrive.
Finding that life, if it exists, will be a challenge. It is likely buried under ice sheets miles thick, a barrier impenetrable to most passing probes. Still, a mission to explore them would be a start, and would give us, for the first time in five decades, a close look at the frozen giants of the Solar System.
Solar Power from Space
For years Europe has relied on Russian gas to power homes, factories and power grids. Now, as war rages in Ukraine, that reliance has turned into a strategic blunder. Russia has drastically cut supplies of gas across Europe, threatening a long cold winter for millions of Europeans.
In response European leaders are seeking new sources of energy. Liquefied gas, shipped from America or the Middle East, may prove enough to get the continent through the winter. But they also need a longer term approach: one, ideally, that also addresses the pressing need to reduce fossil fuel use.
Europe, famous for its wet climate and northern latitudes, is not well placed for solar power to play a big part in this transition. Yet later this year the European Space Agency, ESA, will fund studies into a radical solution to capture the Sun’s power: building vast solar farms in orbit, high above the Earth.
Naively this looks like a good idea. Solar energy is free and abundant, and satellites a few thousand miles high can capture a lot of it. The resulting power can be beamed down to collectors on the Earth’s surface, which then feed into electrical grids. In theory, then, this could offer an independent and almost inexhaustible supply of clean energy.
With a closer look, however, the idea looks less sensible. ESA would need to put a lot of stuff in space to make it work, a task that would likely cost tens, if not hundreds, of billions of euros. They’d need to find a safe and efficient way to bring the power down to Earth; and also find a cheap way to maintain and repair the solar panels in orbit. Even if all this can be done, it would still take decades to put in place.
Space based power, then, is unlikely to be used any time soon. But the idea is tempting enough that several space agencies have started looking into it. ESA, for now, are only funding a feasibility study. China is also planning a test satellite, and could put a small solar farm in orbit in the 2030s. NASA is paying attention too – they launched their own study into the concept earlier this year.
The New Spaceplanes
The dream of spaceplanes - vehicles that can fly, literally, between Earth and space - may seem to have died with the Space Shuttle. Yet the idea has been quietly booming: both China and the United States now have one soaring far above the Earth.
Unlike the Shuttle, these are unmanned craft. Both are fully automatic, their descent through the atmosphere managed by computers. Both, too, seem capable of spending long periods - months or even years - in space, and both are military projects funded by secret budgets.
That last point means there are few public details about why, exactly, superpowers are building these planes. Espionage is certainly one reason: space planes can be launched at short notice and easily steered once in orbit. They could also be used to deploy satellites secretly – thereby avoiding the publicity that comes with a rocket launch.
They also allow nations to experiment with new technologies. America has likely tested innovative sensors onboard its spaceplane, technologies that could be used in future spy satellites. China may be exploring hypersonic flight, studying the re-entry glide of the spaceplane to inform the development of hypersonic missiles, capable of travelling several times the speed of sound.
For now America’s spaceplane seems more advanced than China. The X-37B, as it is called, has made six flights so far, the most recent – and still ongoing – has lasted more than two years. China’s, by contrast, is making only its second flight, and has spent just a few weeks in total in space.
Rocket Lab Dream of Venus
Rocket Lab, a rocket company with a good record of launching small satellites, announced detailed plans to send a spacecraft to Venus. The concept, first revealed in 2020, would see a small probe fly through the Venusian atmosphere, scanning its thick clouds for signs of life.
Though the idea sounds ambitious, and certainly has never been done before by a private company, Rocket Lab has already made several steps towards a successful mission. The company earlier this year sent a NASA satellite on a trajectory towards the Moon, demonstrating they have the ability to go beyond Earth orbit.
A similar approach, Rocket Lab think, could be used to reach Venus. If so, that may be success enough - proving the potential for small rockets and cheap probes to return useful data from the planets.
The most system complete solar power satellite concept that I have come across is presented in Gerard K. O’Neills’ “The High Frontier”. Uses lunar resources, launched from the lunar surface by mass drivers. Not practical in the short term but seems more long term possible than launching from Earth’s gravity well, even using Starship.