Category: Space Sunday

August and September 2022 mark the 45th anniversaries of the launches of Voyager 1 and Voyager 2, NASA’s twin interplanetary – and now interstellar – explorers.

Designed to take advantages of a planetary alignment which occurs once every 176 years, allowing the use the gravities of one of the outer planets to “slingshot” a vehicle on to the next, the two Voyager mission vehicles remain in operation today, and continue to stand at the forefront of our understanding of the local space surrounding our solar system.

Voyager 1 continues to set records as the furthest man-made object from Earth – it is now over 23.3 billion kilometres away – whilst Voyager 2 remains famous for giving us our first detailed views of Uranus and Neptune during its 20-year voyage through the outer solar system.

Products of the 1970s, the Voyager craft stand as museum pieces by today’s standards. Each has around 23 million times less memory than a modern cellphone, their communications systems can only transmit and receive data some 38,000 times slower than a modern cellular network, and they record the data they gather on an 8-track tape recorder prior to transmitting it back to Earth. Nevertheless, the amount of knowledge they have gathered and returned to us about the outer reaches of the solar system, the heliosphere (the bubble of space around the Sun in which the solar system resides), the heliopause (the boundary between that Sun-dominated “bubble” and the galaxy at large) and the realm of interstellar space beyond that bubble.

Operated by NASA’s Jet Propulsion Laboratory (JPL), the Voyager craft were launched in reverse order, with Voyager 2 lifting-off on August 20th, 1977 and Voyager 1 following on September 5th, 1977. The reason for this ordering was simple: during the development of the mission, Saturn’s moon Titan, known to have an atmosphere, was identified as a primary target for fly-by investigation, and so was assigned to Voyager 1.

However, in order to reach the moon, the vehicle would have to follow a course that would carry it over Saturn’s northern reaches, and throw it “down” and out of the plane of the ecliptic and away from any chance of reaching the outer planets. Instead, Voyager 2 was tasked with completing the “grand tour” of the major planets – Jupiter, Saturn, Uranus and Neptune, and in order to achieve this, it would have to be launched first.

Even so, thanks to the nature of orbital mechanics requiring Voyager 2 to be thrown out on a more circular, “indirect” path towards Jupiter whilst Voyager 1 could be launched more directly towards Jupiter meant it could reach the gas giant first, arriving in January 1979, having “overtaken” Voyager 2 in December 1977. . Its passage through the Jovian system revolutionised our appreciation of the Galilean moons of the system, after which it travelled on to its November 1980 encounter with Saturn and then Titan.

Voyager 2’s more circular trajectory meant it did not reach Jupiter until July 1979, six months behind Voyager 1, but its route allowed it to make a much closer fly-by of Europa, the ice-covered Galilean moon, giving scientists the first hint of the nature of the mechanisms at work deep within the moon.

From here the vehicle journeyed on to an August 1981 encounter with Saturn and then Uranus in 1986 and then Neptune in August 1989, whilst Voyager 1 continued onwards toward the heliopause, all of which I covered in  Space Sunday: Voyager at 40.

In 2010, Voyager 1 commenced a two-year transition from the space dominated by the Sun and its outward flow of radiation, and the realm of interstellar space. The first indications that it was beyond the influence of the Sun’s radiation came in later 2012 – although it was not until March 2013 that this was empirically confirmed through analysis of multiple data returned by the vehicle.

Voyager 2 commenced its voyage through the heliopause in 2013; however, as it was still travelling within the plane of the ecliptic, it was effectively travelling through a “thicker” part of the “bubble wall” of the heliosphere, so it did not enter interstellar space until November 2018.

Even so, and possibly confusingly, neither craft have actually departed the solar system per se. This is because the “size” of the solar system is measured in two ways: the influence of the Sun’s outward flow of radiation and by the influence of its. Despite having passed through the former, both craft are sill within space affected by the latter, and neither will reach the Oort Cloud – the source region of long-period comets and seen as marking the outer limits of the Sun’s gravitational influence – for another 300 years.

As such, both of the nuclear-powered vehicles are now engaged in a multi-vehicle mission (having been joined in it by the likes of the New Horizons spacecraft, the Parker Solar Probe and others) referred to as the Heliophysics Mission.

The Heliophysics Mission fleet provides invaluable insights into our Sun, from understanding the corona or the outermost part of the sun’s atmosphere, to examining the sun’s impacts throughout the solar system, including here on Earth, in our atmosphere, and on into interstellar space. Over the last 45 years, the Voyager missions have been integral in providing this knowledge and have helped change our understanding of the sun and its influence in ways no other spacecraft can.

– Nicola Fox, director of the NASA’s Heliophysics Division

Today, as both Voyagers explore interstellar space, they are providing humanity with observations of uncharted territory. This is the first time we’ve been able to directly study how a star, our sun, interacts with the particles and magnetic fields outside our heliosphere, helping scientists understand the local neighbourhood between the stars, upending some of the theories about this region, and providing key information for future missions.

– Linda Spilker, Voyager’s deputy project scientist at JPL

Continue reading “Space Sunday: Voyager at 45” →

Ten years ago, on August 6th, 2012, the world held its breath as a capsule the size of a small truck slammed into the Martian atmosphere at the start of 7-minute descent referred to as the “seven minutes from hell”.

It would either end with the extraordinary sight (had we been able to see it) with a rocket-propelled platform hovering just metres above the surface of the planet as it gently winched a rover the size of an SUV to the floor of Gale Crater – or in a fresh new crater within the crater.

Fortunately, the former was the case, marking the true start of the Mars Science Laboratory (MSL) mission on Mars, an attempt to seek evidence that, billions of years ago, Mars had the conditions needed to support microscopic life. Coincidentally, it marked the start of the column that would morph into Space Sunday.

Since that heady day, the rover – called Curiosity – has clocked up some impressive statistics, including:

• Achieving its primary mission objective – to discover whether Mars had the conditions under which life may have arisen – within its initial 90-day mission period.
• Driving almost 29 kilometres around Gale Crater.
• Ascending 625 metres above the floor of the crater.
• Analysing 41 rock and soil samples using its onboard suite of science instruments, furthering our understanding about Mars.
• Providing huge insights into the Martian climate and weather.
• Being so successful, it has seen its mission initially extended to its full 2-year “post landing” period, and then in multi-year increments, including a recent 3-year further extension.

While Curiosity’s work has been more recently overshadowed by its sibling, Perseverance, it is still ongoing. In the last ten years, the rover has studied the Red Planet’s skies, capturing images of shining clouds and witnessing the transit of the Martian moons Phobos and Deimos across the face of the Sun, causing very localised eclipse phenomena.

In addition, the rover’s radiation sensors have helped scientists measure the amount of high-energy radiation future astronauts would be exposed to on the Martian surface, increasing our understanding of what will be needed to keep them as safe as possible – both in terms of practical protections and the types of procedures required to minimise their overall exposure whilst working on the surface of Mars.

However, Curiosity’s most important work is that of determining that liquid water as well as the chemical building blocks and nutrients needed for supporting life were present for at least tens of millions of years in Gale Crater – and that similar conditions could exist elsewhere on Mars. These discoveries directly confirmed the need for the Mars 2020 mission with Perseverance – which is designed to look for the direct evidence that microbial life did take hold in the conditions Curiosity found to be true.

After exploring the bedrock floor of the crater, Curiosity started on a major phase of its mission – scaling the flank of “Mount Sharp”, a 5-km high mound of materials deposited against and around the crater’s central impact peak during the many warm, wet periods that marked the very early history of Mars, and which meant Gale Crater was once the site of a huge lake of liquid water.

The climb has taken up the majority of the rover’s time on Mars, and is still continuing, with Curiosity recently move into an entirely new phase of operations. For the last few months the rover has been making its way along a canyon marking the transition between the more submerged parts of “Mount Sharp” – officially called Aeolis Mons – a region believed to have formed as water was drying out, leaving behind salty minerals called sulphates.

We’re seeing evidence of dramatic changes in the ancient Martian climate. The question now is whether the habitable conditions that Curiosity has found up to now persisted through these changes. Did they disappear, never to return, or did they come and go over millions of years?

– Ashwin Vasavada, Curiosity’s project scientist

The team plans to spend the next few years exploring the sulphate-rich area. Within it, they have targets in mind like the Gediz Vallis channel, which may have formed during a flood late in Mount Sharp’s history, and large cemented fractures that show the effects of groundwater higher up the mountain.

All this progress has come at a cost, however. Along the way, Curiosity had suffered several issues – all of which have been overcome as a result of a team of literally hundreds of engineers and scientists based at the Jet Propulsion laboratory (JPL) and other NASA centres as well as research centres and universities across the United States.

This has allowed major issues that might otherwise have crippled the rover’s abilities. How Curiosity drills for samples has been reinvented a number of times to overcome problems that as the very least might have ended the rover’s ability to drill at all and at worse, crippled its ability to use its robot arm.

Another area of concern has been the rover’s aluminium wheels. These bear the brunt of the sheer force of Curiosity’s progress as it makes its way over the unforgiving Martian landscape; and even while the rover’s daily progress can only be measured in metres-per-day, the fact is that it is constantly traversing terrain which could rip any one of the large aluminium wheels apart given sufficient time. As such, damage was to be expected – but the speed with which it occurred early in the mission still came as a shock, with engineers going so far as to have the rover reverse course and find a new way around some particularly rough terrain at the foot of “Mount Sharp”.

To counter the risk of wheel breakage, Curiosity’s driving has been extensively revised, and new algorithms written to help the rover better maintain traction whilst manoeuvring over rocks and to better analyse feedback from wheel motors to prevent them overworking or forcing the rover into an manoeuvre that might result in the loss of a wheel. In addition, the rover routinely examines the state of its wheels using both the MastCam system and the MAHLI imager on the robot arm.

Another threat to the rover’s future is that of electrical output. Curiosity utilises the radioactive decay of plutonium pellets within its radioisotope thermoelectric generator (RTG) to create heat which can be converted into electrical power. On the plus side, this means the rover is not dependent on the vagaries of solar power and can (initially) produce much higher levels of electrical power – some 2,000 2atts on its arrival on Mars.

The downside, however, is that the 4.8 Kg of plutonium within Curiosity’s RTG have a half-live of 14 years – and the rover is now 10 years into that period. As such, it is generating a lot less heat that can be turned into electrical power,, and as a result engineers and scientists are now looking at ways to operate the rover more efficiently and reduce the daily power requirements. This includes switching some operations to run in parallel, effectively sharing power.

Despite this latter points, Curiosity is still performing at near-optimal levels for this period in its life, and with caution and forethought, in is not inconceivable to believe the rover will not still be investigating “Mount Sharp” – even on a reduced basis – in another 10 years.

Continue reading “Space Sunday: Curiosity’s 10th, and motors for rockets” →

The approval came not through NASA’s core budgetary process, but as a result of an additional NASA authorisation bill being appended to the newly passed Creating Helpful Incentives to Produce Semiconductors (CHIPS) Act of 2022, intended to increase semiconductor manufacturing in the United States in the wake of pandemic-induced supply chain shortages.

The authorisation bill included in the act specifically targets NASA to receive funding to support ISS operations, and to further the agency’s lunar ambitions and robot exploration of Mars. In addition, the 2023 Commerce, Justice and Science (CJS) spending bill. currently being drafted in Congress, looks as though it will seek to provide NASA with the US $25.9738 billion it has requested for its 2023 operational budget – albeit it with one or two small strings attached. These include ensuring the asteroid-hunting NEO Surveyor mission launches in 2026 as planned, rather than slipping to 2028; cutting a part of the space technology spending that includes nuclear thermal propulsion work; and adding $50 million to support a new commercial crew provider beyond Space and Boeing to increase program options.

However, while paying the lion’s share towards ISS operations, the US relies heavily on the assistance of its International partners: a further 15 nations (Brazil having withdrawn in 2007), with both the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) providing core modules for the station, and the Canadian Space Agency (CSA) crucial support systems. While 14 out of the 15 (the majority operating under the auspices of ESA), the same cannot be said for the 15th – Russia, which is also the second largest financial contributor to the station, as well as the largest contributor of pressurised modules.

Russia has long bulked at any attempts to extend ISS operations beyond 2024, and while it appeared that a shorter extension to the station’s life to take it through to 2028, that was thrown into doubt in early 2021, when the Russian space agency, Roscosmos, announced that a module – the Solar Power Module-1 (SPM-1, also referred to as NEM-1) – due for launch in 2024, would be repurposed to serve as the core power module for a new, smaller, all-Russian space station, provisionally called the Russian Orbital Service Station (ROSS).

At the time, it was indicated that work on ROSS would commence in 2024 and conclude around 2029. However, that time line was then pushed back to 2030-2035, possibly signalling Russia would remain fully engaged in ISS operations through until 2030. Then came the Russian invasion of Ukraine, international outrage, condemnation and the rest. This included assorted (and somewhat silly) threats on the part of the then head of Roscosmos, Dmitry Rogozin, which included statements that Russia would depart the ISS in 2024 – and might take parts of it with them…

While Rogozin has now departed Roscosmos for pastures new, his replacement at the agency, his replacement – equal hardliner Yuri Borisov – Has sounded something of a warning that attitudes towards ISS operations have not shifted, telling the TASS news agency that Russia’s engagement in ISS will come to an end “after 2024” – the date to which the committed to support the station.

Exactly what “after 2024” means in practice remains unclear. ISS partners are obligated to give at least 12 months warning of an intention to depart the project – and Russia has never taken that step through to now, and it could be argued that 2030 is as much “after 2024” as 2025.

That said, coming on the heels of Borisov’s comments to TASS, Vladimir Solovyov – who is both the chief designer at RSC Energia, the company responsible for developing space station modules and the director of the Roscosmos department directly responsible for ISS operations – presented the first detailed overview of the proposed ROSS platform, including the fact that the first modules are to be operational by the end of 2028.

While not explicitly named by Solovyov, the first of these modules appears to remain the re-purposed SPM-1 / NEM-1, Solovyov indicated would launch in 2026. This will then be followed in 2028 by a Core Crew Module (CCM – this nomenclature will likely change), providing crew living facilities and additional power systems, with the two units operating as a baseline station until two additional science modules can join them in 2030.

This tends to indicate that from 2025, Roscosmos will start pivoting priorities away from ISS and to ROSS; but it does not signal they will be ending all involvement in ISS. Further, and while again not indicated by Solovyov, the fact that the science modules will not be flown until 2030 might be indicative that consideration is being given to perhaps utilising the Nauka module, which only joined the ISS in 2021 and which is capable of its own propulsion, within ROSS.

This might come down to the orbit ROSS eventually placed within. During his presentation Solovyov stated the some of Russia’s frustrations with ISS is that the station operates at an orbital inclination that precludes much of the Earth and space science Russia would like to carry out. As such, a wide range of potential orbits are being considered for ROSS, some of which would exclude any transfer of Nauka from ISS to ROSS.

As well as the four core modules, Solovyov indicated that the station’s facilities could be expended through the use of a (yet-to-be built) large-scale automated re-supply vehicle that could perform a number of roles from straightforward delivery of supplies and consumables through performing required orbital boosts to offering temporary additional working space when needed. It is additionally possible this re-supply vehicle might be combined with a capsule-like crew vehicle, allowing it to deliver both personnel and supplies to the station, with dedicated crew-only flights to and from ROSS carried out aboard a smaller vehicle intended to replace the veritable Soyuz

Most interestingly, Solovyov  stated ROSS would not necessarily be permanently crewed, but will utilise a high degree of automation for science operations, with crews visiting it to carry out very specific science research and / or to collect data and carrying out maintenance and other work. However, as he also indicated that the station could well form a part of Russia’s ambitions for the Moon and Mars (some of least at which will likely include working with China), the station could become more fully crewed from 2030 onwards.

ESA / NASA Simplify Mars Sample Return Mission

In May I wrote about the proposed ESA / NASA Mars Sample return mission to bring core samples gathered by NASA’s Perseverance rover back to Earth for analysis. At the time of that report, NASA and ESA were responding to calls for the mission to be prioritised and take place earlier than the early-to-mid 2030s. However, the plan being forward back then stuck me as being overly complicated, involved six vehicles and three individual launches; and bless them, NASA and ESA now seem to share that view:  on July 27th, 2022, the two agencies issued an update that reduced the mission to just two launches and changes the overall line-up of vehicles involved, although the fine details have yet to be worked out.

In the March-May plan, Perseverance would have deposited a cache of core sample tubes somewhere in Jezero crater. This cache would then be targeted by two landers – one carrying the Mars Ascent Vehicle (MAV), and the other a small, European-built “fetch” rover. This would collect the sample tubes from the cache and deliver them to the MAV, which it turn would launch from its lander to carry them up to a waiting Earth Return Vehicle (ERV) built by ESA, with the sample tubes transferred to that vehicle for the return to Earth.

Under the new plan, the ERV remains, as does the MAV and its lander. However, the “fetch” rover and its lander have been scrapped. Instead, the MAV will launch to Mars in 2028 and its lander will use telemetry from Perseverance to land in the vicinity of the rover, which will then drive to the MAV and perform the transfer of samples directly.

Exactly how this transfer will be managed is unclear – Perseverance isn’t exactly designed for such a task. So, as a contingency, the lander carrying the MAV will carry will also be equipped with two “Ingenuity class” helicopters. Fitted with wheels and a small grappling arm, as well as flying, these will be capable of scooting around on wheels, collecting sample tubes from the cache rack Perseverance will deposit on the surface of Mars and delivering them to the MAV. Once loaded, the MAV will launch to orbit, rendezvous with the ERV, and the sample pack transferred for its return to Earth.

Overall, the approach is still somewhat complicated, but assuming a methodology can be employed to allow Perseverance to complete the sample transfer to the MAV unaided, it means NASA will have two fresh helicopters available to support the rover in its further explorations in and around Jezero Crater. And even if the helicopters do have to be used for sample retrieval, by combining them with the MAV and its lander, an entire additional launch – and the development of a complex small-scale “fetch” rover – can be avoided, both reducing the overall cost of the mission and reducing the potential for long-term delay which might occur with the development of an entirely new class of rover.

Which is not to say the target 2027 launch date for the ERV isn’t itself challenging; three years to develop and test a space vehicle is an extremely short time-frame; as such it would seem likely this mission will slip back into the early 2030s.

Continue reading “Space Sunday: space stations, sample returns and falling rockets” →