Category: Other Worlds and Tech

If all continues on track, Monday, August 29th, 2022 will mark the start of America’s return to the Moon with crewed missions, just a few months shy of the 50th anniversary of the last crewed mission, Apollo 17 (December 7th-19th, 1972). It will come with the lift-off of the Artemis 1 mission, and the maiden flight of NASA’s new heavy lift launcher, the Space Launch System.

The mission will be – as most no doubtless know only too well – uncrewed, and the destination not the lunar surface, but cislunar space in what will be the most comprehensive test of the SLS rocket and the Orion Multi-Purpose Crew Vehicle (MPCV) ahead of crewed flights, which are due to commence with Artemis 2.

The final countdown for the launch commenced on Saturday, August 27th at launch pad 39B within the Kennedy Space Centre, Florida, and providing no significant hitches occur, it is due to terminate at 12:33 UTC on August 29th with the ignition of the booster’s four RS-25 shuttle-derived motors and two massive solid rocket boosters (also derived from those used in the space shuttle programme). At the time of writing this piece, and despite a thunderstorm leading to a lighting strike at the launch facility on the evening of August 27th, everything was on course for the launch, and the forecast indicated a 70% likelihood that the weather at Cape Canaveral and downrange from the launch pad would be good for the launch.

However, all things are not guaranteed, and the mission has a slim 2-hour launch window in which to get off the pad. Should the launch have to be scrubbed for any reason, further launch windows will be available on September 2nd (2 hours), and September 5th (90 minutes).

There is a lot riding on this mission; while Orion has already flown once in space – eight years ago in the uncrewed Exploration Flight Test-1, launched atop a Delta IV Heavy rocket – this will be the first flight of the vehicle outside of directly orbiting the Earth; however, for SLS, the mission could very much be make-or-break. The vehicle has been beset by issues throughout its development programme (many of which amounted to either unforced errors or came as a result of the entire Artemis programme being unduly accelerated by the Trump Administration to achieve a crewed landing by 2024 rather than 2028, as originally planned. As such any major or catastrophic failure could have major repercussions for NASA and the US government space programme.

SLS has been more than two decades in development. It started life in the early 2000s as the Ares V under NASA’s Constellation programme. Instigated by the then NASA administrator Michael Griffin, Ares 5 was to be the heavy-lift launch vehicle intended to help return humans to the Moon and (eventually / primarily) help pave the way to Mars, working alongside the smaller Ares 1 crew launch vehicle and what was then called the Orion Crew Exploration Vehicle (CEV). I say “primarily”, because Griffin was a strong advocate of human missions to Mars and the Ares programme was actually named for (and pretty much lifted from) the Mars Direct humans-to-Mars concept first proposed by Robert Zubrin and David Baker  in 1990.

Despite enormous strides made in the development of Ares 1 (the first of which actually few in 2009) and the Orion CEV, the Obama administration opted to scrap the constellation programme on the grounds of cost. While Ares 1 went away in its entirety, Orion and Ares V underwent a redesign process, the former having its capabilities increased, whist Ares V went back to the drawing board to later emerge as the SLS.

The key differences between Ares V and SLS is the former was intended to be a heavy-lift cargo launcher, capable of delivering up to 168 tonnes to low-Earth orbit (LEO), up to 71 tonnes to lunar orbit and around 60 tonnes to Mars, with Ares 1 left to carry crews up to orbit. SLS, on the other hand is intended to be both a crewed and cargo launch vehicle, capable of delivering between 95 and 130 tonnes to LEO depending on the vehicle type, or some 46 tonnes to lunar orbit (Block 2 cargo) and 30-40 tonnes to Mars (Block 2 cargo).

The primary objectives for Artemis 1 are to prove the SLS launch system’s Block 1 launch capabilities; achieve a distant retrograde orbit (DRO) around the Moon, and make a safe return to Earth with a successful atmospheric re-entry and splashdown by the Orion MPCV capsule. The overall mission duration is expected to be some 42 days.

This first flight – which will also mark the first use of the European-built Orion service module (Orion’s flight in 2014 didn’t require a service module) – is to be one of only three launches of the SLS Block 1 rocket. This uses what is called the  Interim Cryogenic Propulsion Stage (ICPS) – essentially the upper stage of a Delta IV rocket. From Artemis 4 onwards, launches will use the more powerful Exploration Upper Stage (EUS) in what is termed the Block 1B SLS variant, and which will also be used in the Block 2 cargo variant (if this eventually flies).

The ICPS will be used to insert Orion into its trajectory to the Moon prior to separating from the capsule and its service module and performing one further crucial mission task. It will then pretty much parallel Orion to the Moon before using the latter’s gravity to slingshot itself away into a highly elliptical orbit of its own.

As well as being used to check-out SLS and Orion, Artemis 1 has a number of science goals, and the Orion MPCV is not the only payload for the mission. Shortly after Orion separates from the ICPS, the latter – in that other crucial aspect of the mission mentioned above – will deploy multiple cubesats on trajectories to the Moon. These will carry out an range of scientific tasks, including:

• Detecting, measuring, and comparing the impact of deep space radiation on living organisms (yeast in this instance) over long durations.
• Studying the dynamic particles and magnetic fields that stream from the Sun and as a proof of concept for the feasibility of a network of stations to track space weather.
• Imaging Earth’s plasmasphere to study the radiation environment around the Earth.
• Searching for additional evidence of lunar water ice from a low lunar orbit.
• Mapping hydrogen within craters near the lunar south pole, tracking depth and distribution of hydrogen-rich compounds like water over a 60-day, 141 lunar orbit mission.
• Flying by the Moon to collect surface spectroscopy and thermograph and return the results to Earth for analysis.

In addition, some of the cubesat missions will be technology demonstrators, including a further solar sail demonstrator; using very small automated vehicles to operate in close proximity to large vehicles and image them / look for potential damage; using small, low thrust gas motors for trajectory control in the space between Earth and the Moon.

Nor is that all; Orion itself will be carrying a number of experiments within the capsule, with a focus on gaining a better understanding of the radiation regime between the Earth and Moon and within cislunar space.

The most evident of the onboard experiments is “Commander Moonikin Campos”, a mannequin dressed in the Orion Crew Survival System Suit. Sharing (OCSSS).  Sharing same iconic orange colour as the survival suits used on shuttle missions, the OCSSS is a much more advanced version, designed to be worn continuously for periods of up to 6 days at a time (so whilst en route to the Moon, whilst in lunar orbit and during a return to Earth), to offer enhanced radiation protection for the wearer whilst aboard Orion. To this end the mannequin – named for Apollo 13 electrical subsystems engineer Arturo Campos, who played a major role in bringing that crew back to Earth alive – is equipped with a plethora of radiation sensors to test the effectiveness of the suit.

Continue reading “Space Sunday: “we are go for launch” – Artemis 1 on the pad” →

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” →