Category: Space Sunday

We’re probably all familiar with the concept of some Moons within our solar system  – notably Saturn’s Enceladus, and Jupiter’s Europa, Ganymede and Callisto – potentially being completely encompassed by a liquid water (or at least a slushy) ocean under their surfaces. But how about a moon being almost completely encompassed by an ocean of hot volcanic magma just a few kilometres under its surface?

That’s the proposal contained within a new paper written under the auspices of NASA’s Jet Propulsion Laboratory, and based on an analysis of data obtained by the Jovial Infrared Auroral Mapper (JIRAM) instrument aboard NASA’s Juno mission in reference to Io, the innermost of the four Galilean moons of Jupiter.

Of course, we’ve long known that Io, a moon slightly larger than our own, is the most volcanic place in the solar system. More than 400 active volcanoes have been identified since we first witnessed one erupting in 1979, courtesy of NASA’s by Voyager 1 in 1979, and the Juno mission has imaged no fewer than 266 actively erupting during its periodic fly-bys of Io as it studies Jupiter and its moons. The overall driving force behind these volcanoes is tidal flexing deep within Io’s core and mantle, the results of the moon being in a constant state of flux thanks to the gravitational influences of (most particularly) Jupiter to one side and the three other Galilean satellites on the other.

However, there has always been something of a question as to how these volcanoes might – or might not – be related and directly powered. Here on Earth, volcanism usually occurs as a result of decompression melting within the asthenosphere – the upper limits of the mantle directly under the lithosphere/crust comprising solid and partially-melted rock. This gives rise to magma, which is then forced upwards through the lithosphere as localised volcanic eruptions. This was long held to be the case with Io, with scientists believing its volcanoes, like the majority on Earth, were driven by the upwelling of individual magma flows.

But during the Galileo spacecraft’s observations of Io between 1995 and 2003, the data gave tantalising hints that Io’s volcanism could be the result of a somewhat different process, but it has taken the unique capabilities of the Juno spacecraft to confirm this to be the case. By gathering extensive thermal and infrared imaging of Io’s mantle, the JIRAM instrument has been able to put together a comprehensive view of the upper layers of Io’s mantle, revealing that far from being a layer mix of solid and partially melted rock, Io’s asthenospheric region is entirely molten in nature.

In other words, lying just below Io’s lithosphere (roughly 12-40 km thick) is a moon-girdling ocean of magma, some 50 km thick, with a mean temperature of some 1,200ºC, and which powers all of Io’s active volcanoes.

This may not sound exciting in the scheme of things, but it further demonstrates the uniqueness and complexity to be found within the Jovian system.

A further example of this can be found with Io’s big brother, Ganymede. The third of the Galilean moons in terms of distance from Jupiter, Ganymede is not only the biggest of the Galilean moons orbiting Jupiter, it is the biggest and most massive natural satellite in the solar system. In fact, if it were orbiting the Sun rather than Jupiter, it would be classified as a planet, being even larger than Mercury.

Ganymede, like its smaller siblings around Jupiter – and the rocky planets of the inner solar system – is a complex place enjoying a complicated relationship with its parent; one which shares near-similarities with Earth’s relationship to the Sun.

Much has long been known about Ganymede as a result of observations made from Earth – such as via the Hubble Space Telescope – and by the various missions which have flown past or orbited Jupiter. These have helped us confirm that Ganymede has a sufficiently warm interior to support a global liquid water ocean beneath its crust, an ocean larger by volume than all of Earth’s combined.

We’ve also been able to (largely) confirm the presence of a tenuous atmosphere of oxygen and CO2, which seems to be particularly concentrated around the northern and southern latitudes, likely constrained by the interaction between Ganymede’s weak magnetic field and the far more powerful magnetic field generated by Jupiter – the predominant O2 content of the atmosphere is thought to be the result of water vapour escaping the moon’s interior being spilt by the radiation carried down over the poles by the magnetic field interaction.

It is this interaction between radiation, magnetic fields and the surface of Ganymede which have been part of the focus of a study made of the moon using instruments on the James Webb Space Telescope (JWST), and which was recently published.

Ganymede’s surface is dominated by two types of terrain: bright, icy features with grooves, covering about two-thirds of Ganymede’s surface, and older, well-cratered and darker regions )on places scored by asteroid impacts of the moon’s more “recent” past, which could not be confused with the brighter terrain) . The two terrain types are not differentiated in terms of their location on Ganymede’s surface, they are instead intermingled, with the lighter terrain cutting swathes across the darker terrain.

Some of these brighter swathes – notably those around the Polar Regions – carry strong evidence of water ice, which appears to have been exposed by (in the words of the study) “the combination of micro-meteoroid gardening, excavating the ice, and ion irradiation”.

In other words, over the millennia, dust and material has been caught within the interactions between the two magnetic fields, smashing into the moon’s surface to expose the underlying water ice, allowing it to be irradiated by plasma also carried by the inflowing magnetic field, causing some of it to escape as water vapour which has been either further irradiated and broken down (thus giving rise to the accumulation of the tenuous, O2-rich atmosphere near the surface), or re-accreting as easily-identified water ice on the surface rock.

Whilst the two magnetic fields interact around Ganymede’s poles and along the moon’s “trailing edge” as it orbits Jupiter in a very similar manner to the interaction between Earth’s magnetic field and that of the Sun over our own poles, the spectral properties seen along the moon’s ”leading edge” in its orbit suggest that there is a far more complex, and yet to be understood interaction taking place between the magnetic fields of planet and satellite. Solving this mystery might require time – and some assistance in the form of the European Space Agency’s Jupiter Icy Moons Explorer (JUICE) mission launched in April 2023, and due to reach the Jovian system in 2031, where it will likely uncover more surprises about both Ganymede and Europa.

Continue reading “Space Sunday: Jovian Moons, and lunar aspirations” →

3D printing may be a relatively new technology, but it is one that is revolutionising may sectors of industry and commerce – and that includes space exploration. I’ve already covered the work of Relatively Space to manufacture and operate the world’s first 3D printed rocket systems in the form of the (now retired after it maiden launch failure) Terran 1, and the highly ambitious, semi-reusable Tarran R. However, NASA has actually been charting the potential for 3D printing in space and on Earth for almost a decade.

As an example of this; the first 3D printing system installed on the ISS arrived in 2014. It was a modest affair primarily designed to research whether or not practical, plastic-based 3D printing could be used in the microgravity of space. As the analysis of the printed parts demonstrated, there were no weaknesses or deficiencies in their construction when compared to identical items produced on Earth using the same process. Thus, the initial project was expanded to encompass the production of usable items – a wrench, plastic brackets, parts of an antenna system, for example – using a variety of industrial-grade plastic filaments.

The capability was then enhanced with the arrival of ReFabricator – a system which could take plastics used on the ISS and recycle them into plastic filament for use by the printer, with Recycler later adding the ability to do the same with other “waste” materials on the station.

In 2023, the European Space Agency and Airbus Industries went a stage further with Metal3D, a printer capable of producing metal and alloy parts for use on the ISS. It is part of a broader project to develop in-situ orbital and lunar 3D printing systems capable of manufacturing everything from replacement parts to entire assemblies such as radiation shields, vehicle trusses, etc. ESA plan to use an enhanced Metal3D system to use lunar regolith as its raw material in the production of equipment and components.

Meanwhile, NASA has also been busy on Earth with a range of 3D printing projects and studies, one of which  – RAMFIRE – which earlier in the year had its (quite literal) baptism of fire.

Standing for the Reactive Additive Manufacturing for the Fourth Industrial Revolution,  RAMFIRE is a unique process which combines an entirely new aluminium alloy called 6061-RAM and 3D printing to create rocket nozzles for space vehicles. To understand why it is potentially so revolutionary, three points need to be understood:

• As a rule, aluminium is a poor choice for rocket engine (and particularly engine nozzle) construction as it has a rather nasty habit of melting when exposed to high temperatures – such as those generated by a rocket engine nozzle.
• While aluminium can be strengthened to withstand higher temperatures through the use of additives, the additives themselves can make it susceptible to cracking and microfractures if the aluminium has to be wield to itself or other items as is again required in the production of rocket nozzles.
• At the same time, being able to print an entire engine nozzle as a single unit and in aluminium, has the potential of both greatly simplifying the process of rocket engine production (as the nozzle now comprises a single part, rather than up to 1,000 individual parts as is currently the case, and for the engine to be significantly lighter without any reduction in thrust, allowing for a potentially large payload to be carried.

Using 6061-RAM with a 3D printing process developed in partnership with Colorado-based Elementum 3D, NASA has been able to produce single-piece aluminium rocket nozzles which, by a combination of the additives used in the alloy and a series of special cooling channels printed into the nozzles, both withstand the heat of combustion in their chambers and also passively cool themselves in the process.

Over the summer period, two small-scale RAMFIRE nozzles were put through their paces at NASA’s Marshall Space Centre in a series of hot fire tests, the results of which were published by NASA on October 16th. The nozzles were tested using two cryogenic propellant mixes – liquid oxygen and liquid hydrogen in one batch of tests, and liquid oxygen and liquid methane in the other. It had been anticipated the nozzles would manage a pressure of up to 625 psi in their chambers, and run for a handful of minutes apiece. As it turned out, they functioned above the anticipated pressure without damage and racked up a cumulative burn time of almost 10 minutes.

This level of burn time and pressure is well in excess of the major requirement for such engine nozzles: within cargo transports carrying payloads to the surface of the Moon and landing them safely, bore lifting off again for the return trip to Earth to collect more cargo. However, the technology being developed by NASA and Elementum 3D has the potential to be used in a wide range of space vehicle applications, from propellant tank manufacture through to providing a means to provide very lightweight, thrust-efficient aerospike engines, one of the holy grails of space transportation systems.

There is still further R&D to go with RAMFIRE, but NASA and Elementum 3D are already looking at licensing 6061-RAM and the printing process to commercial organisations interested in adapting it for use in their space-based efforts  – and possibly further afield in aerospace research sectors.

Continue reading “Space Sunday: 3D printing for space, and asteroids” →

Asteroids have been something of a focus for Space Sunday of late, and they’re going to be again this week. Or at least, one is: 16 Psyche, as this is the target for a NASA mission which, if all goes according to plan, will launch from Kennedy Space Centre on October 12th, 2023.

16 Psyche was discovered by the Italian astronomer Annibale de Gasparis on 17th March 1852, and is named for the ancient Greek goddess of the soul. It has a shape consistent with that of a Jacobi ellipsoid, and measures some 278 km x 238 km x 171 km as it orbits the Sun between Mars and Jupiter once every 4.9 years at an average distance of 437 million km (2.92 AU). It is also the 16th minor planet to be found in the solar system by order of discovery (hence the 16 in its name).

But what makes 16 Psyche a subject for detailed study is the fact that it is the largest and most massive M-class asteroid – a class of asteroids which appear to contain higher concentrations of metal phases (e.g. iron-nickel) than others within the asteroid belt – yet discovered in the solar system. So massive in fact, that it was long theorised that it was the exposed core of a protoplanet.  These are bodies thought to have been created during the early history of the solar system from the collision and coalescing of planetismals, and which may have gone on to play a role in the formation of the inner planets of the solar system (in fact, for a time in the early 20th century, the coalescing of planetismals into protoplanets and protoplanets into planets was thought to be the process by which all planets were created, an idea long since proven incorrect; planetary formation is far more complex than things bumping into one another and gluing themselves together).

Thus, it is also possible that whilst a protoplanet, 16 Psyche evolved along lines which had nothing to do with planetary formation; thus, studying it might either help in our understanding of planetary formation and / or enable us to more fully understand the unique processes at work within these tiny (in terms to their relationship with planets) bodies, and the mechanisms which ultimate gave rise to their form and nature. Most intriguingly, a mission to 16 Psyche might even point to a different story as to how objects in the solar system formed.

Hence the upcoming NASA mission and spacecraft which bear the asteroid’s name. First proposed in February 2015 by Arizona State University, the idea was awarded a US $13 million grant under the agency’s ongoing Discovery Programme to allow the basic concept to be fully evaluated and the initial design for the spacecraft determined. As a result of this, the mission was officially adopted into the Discovery Programme at the start of 2017 with a budget capped at $1 billion.

At that time, the mission was targeting a later 2023 launch date; but such was the confidence in the vehicle’s development cycle that this was revised to a July 2022 launch opportunity. This would allow for a much faster mission, drastically reducing the transit time to 16 Psyche, allowing the spacecraft to reach it in 2026, rather than 2029 as would be the case with a 2023 launch. Unfortunately, COVID-19 intervened to delay the construction and testing of the spacecraft, forcing NASA to push the launch date back to October 5th, 2023. Then in September 2023, this was delayed a further week to allow time for adjustments made to the operational parameters for the spacecraft’s cold gas thrusters (used to orient the craft when manoeuvring) to be properly checked and verified.

Psyche (as in the spacecraft) will commence its journey atop a SpaceX Falcon Heavy rocket due to lift off from Pad 39A, Kennedy Space Centre, Florida at 14:16 UTC on October 12th. Once the craft has separated from the Falcon Heavy’s upper stage, it will deploy its massive solar arrays – a span totalling 25 metres and 7.3 metres across at its widest. Capable of generating 21 kilowatts of electricity whilst in the vicinity of Earth (which will decrease over distance to between 2.3-2.4 kilowatts when the spacecraft is orbiting 16 Psyche), these panels will not only provide electrical power to Psyche’s instruments, but will also power the vehicle’s primary propulsion system.

This comes in the form of four Hall-effect SPT-140 thrusters which will be used individually rather than collectively during the cruise stages of the mission, to both propel the spacecraft to its destination and slow it for orbital insertion around 16 Psyche. Each thruster uses some of the electricity generated by the solar panels to generate an electromagnetic field, which is in turn used to direct and accelerate a stream of inert xenon gas ions, expelling it as an exhaust mass to propel the craft.

The force of this exhaust is not huge – it’s about equal to that felt when holding an AA battery on the palm of the hand – but the key thing is, it can do so for weeks, and with a tiny amount of fuel, allowing for a constant acceleration, reducing the transit time to the asteroid compared to conventional meaning of transit (i.e. using momentum imparted by the launch vehicle coupled with multiple planetary flybys) and at a fraction of the propellent load (1 tonne or 10%)  that would be required if conventional chemical motors were to be used.

Even so, the journey to 16 Psyche will still the 2.6 tonne spacecraft take 5 years 10 months. The first part will be a 2-year, 7-month outward spiral around the Sun so the spacecraft can perform a flyby of Mars in May 2026. This will allow it to both accelerate and swing itself onto a trajectory which crosses that of 16 Psyche in 2029, allowing the vehicle to slow itself into an initial orbit around the asteroid in August of that year.

During the initial part of the outward cruise, the spacecraft will be used to demonstration a potential new deep space communications technology – DSOC (“dee-sock”), the Deep Space Optical Communications system. This is a laser-based system which, if it works as planned, will increase communications performance and efficiency between Earth and a spacecraft in deep space by between 10 and 100 times, simply because of the removal of signal attenuation compared to radio signals and the greater bandwidth / throughput rates lasers can provide. DSOC will initially be tested through the first 12 months of the mission and, subject to results, the demonstration may be extended into the second year of the vehicle’s cruise phase, allowing the capability to be tested over distances of up to 2.5 AU.

On arrival at 16 Psyche, the spacecraft will enter the first of five orbital regimes (one if which it will use twice) in order to thoroughly map and study the asteroid. In particular, these will attempt to probe any magnetic field the asteroid might have (the presence of such a field would greatly lend itself to the idea the asteroid is in fact the core or partial core of a protoplanet). They will also enable the craft to completely map the surface of 16 Psyche and determine its surface composition and properties.

Orbit	Duration	Inclination	Period	Duration	Mission
A	92 days	90º	32.8 hours	700 km	Magnetic field characterization and preliminary mapping
B(1)	92 days	90º	11.6 hours	303 km	Topography and magnetic field characterization
D	100 days	160º	3.6 hours	75 km	Determining the chemical composition of the surface
C	100 days	90º	7.2 hours	190 km	Gravity investigations and Magnetic field observations
B(2)	100 days	90º	11.6 hours	303 km	Topography and magnetic field characterization

Given the nature of the spacecraft and allowing for its overall condition towards the end of the primary mission, it is possible that the Psyche mission could be extended beyond this initial 21-month period.

The launch of the Psyche mission will be broadcast by NASA TV, and can be watched via the link / preview below.

October 2023 Annular Eclipse

On Saturday, October 14th, 2023, nearly one billion people across the United States and the northern countries of South America will be able to watch an annular eclipse of the Sun (or at least a partial eclipse) – as the Moon crosses the Sun’s face as seen from Earth the last solar eclipse for 2023.

An annular eclipse difference from a total eclipse in that the Sun is never completely hidden by the Moon. In the case of October 14th, this will be because  the Moon will be 4.5 days past apogee (the point where it is  farthest from Earth, and so the tip of its umbral shadow cone misses Earth by around 19,200 kilometres, so the disk of the Moon will appear too small to completely cover the Sun; around 48% of the Sun’s diameter remains visible all around the Moon’s disk, creating what can sometime be a spectacular “ring of fire”.

Those able to see an annular eclipse in the United States are located along a line commencing in Oregon and passing directly through Nevada, Utah, New Mexico  and Texas whilst touch the northeast of California and Arizona and the southwest of Colorado. In South America, the line of the eclipse passes through Mexico Nicaragua, Columbia and northernmost Brazil and touches on Costa Rica, Panama and Venezuela. Further afield, people will see a partial eclipse.

However, for those wishing to track the event, NASA’s 2023 Eclipse Explorer offers an interactive map detailing when and where the eclipse will be visible, including the path and duration of annularity (the areas from which the ‘ring of fire’ can be seen), allowing users to dive into the eclipse viewing experience like never before. Both the Time And Date and Virtual Telescope will be livestreaming the eclipse around the globe, as will Slooh via their You Tube Channel.

Of course, if you live along the line of the eclipse, you can always view it live. If you opt to do so (assuming the whether is clear), then remember: never look directly at the Sun either and especially through a telescope or binoculars or camera – don’t even use ordinary sunglasses. To view the eclipse safely you must use solar filters at all times on any optical equipment you are using to observe the Sun and / or wear solar eclipse glasses, regardless of whether your location will experience a partial solar eclipse or an annular solar eclipse. Serious eye damage and even blindness can result if you do not otherwise.

Also, don’t expect things to go really dark in the manner of a total eclipse or to be able to witness the Sun’s corona: that ring of the Sun’s disk peeping around the Moon may be small, but it is still bright enough to prevent that. But it will still be a spectacular event to see, and enthusiasts will go to whatever section of the eclipse track is most easily accessible for them in order to witness it.